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TOMOYO Linux Cross Reference
Linux/mm/hugetlb.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * Generic hugetlb support.
  4  * (C) Nadia Yvette Chambers, April 2004
  5  */
  6 #include <linux/list.h>
  7 #include <linux/init.h>
  8 #include <linux/mm.h>
  9 #include <linux/seq_file.h>
 10 #include <linux/sysctl.h>
 11 #include <linux/highmem.h>
 12 #include <linux/mmu_notifier.h>
 13 #include <linux/nodemask.h>
 14 #include <linux/pagemap.h>
 15 #include <linux/mempolicy.h>
 16 #include <linux/compiler.h>
 17 #include <linux/cpuset.h>
 18 #include <linux/mutex.h>
 19 #include <linux/memblock.h>
 20 #include <linux/sysfs.h>
 21 #include <linux/slab.h>
 22 #include <linux/sched/mm.h>
 23 #include <linux/mmdebug.h>
 24 #include <linux/sched/signal.h>
 25 #include <linux/rmap.h>
 26 #include <linux/string_helpers.h>
 27 #include <linux/swap.h>
 28 #include <linux/swapops.h>
 29 #include <linux/jhash.h>
 30 #include <linux/numa.h>
 31 #include <linux/llist.h>
 32 #include <linux/cma.h>
 33 #include <linux/migrate.h>
 34 
 35 #include <asm/page.h>
 36 #include <asm/pgalloc.h>
 37 #include <asm/tlb.h>
 38 
 39 #include <linux/io.h>
 40 #include <linux/hugetlb.h>
 41 #include <linux/hugetlb_cgroup.h>
 42 #include <linux/node.h>
 43 #include <linux/page_owner.h>
 44 #include "internal.h"
 45 #include "hugetlb_vmemmap.h"
 46 
 47 int hugetlb_max_hstate __read_mostly;
 48 unsigned int default_hstate_idx;
 49 struct hstate hstates[HUGE_MAX_HSTATE];
 50 
 51 #ifdef CONFIG_CMA
 52 static struct cma *hugetlb_cma[MAX_NUMNODES];
 53 static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata;
 54 static bool hugetlb_cma_page(struct page *page, unsigned int order)
 55 {
 56         return cma_pages_valid(hugetlb_cma[page_to_nid(page)], page,
 57                                 1 << order);
 58 }
 59 #else
 60 static bool hugetlb_cma_page(struct page *page, unsigned int order)
 61 {
 62         return false;
 63 }
 64 #endif
 65 static unsigned long hugetlb_cma_size __initdata;
 66 
 67 /*
 68  * Minimum page order among possible hugepage sizes, set to a proper value
 69  * at boot time.
 70  */
 71 static unsigned int minimum_order __read_mostly = UINT_MAX;
 72 
 73 __initdata LIST_HEAD(huge_boot_pages);
 74 
 75 /* for command line parsing */
 76 static struct hstate * __initdata parsed_hstate;
 77 static unsigned long __initdata default_hstate_max_huge_pages;
 78 static bool __initdata parsed_valid_hugepagesz = true;
 79 static bool __initdata parsed_default_hugepagesz;
 80 static unsigned int default_hugepages_in_node[MAX_NUMNODES] __initdata;
 81 
 82 /*
 83  * Protects updates to hugepage_freelists, hugepage_activelist, nr_huge_pages,
 84  * free_huge_pages, and surplus_huge_pages.
 85  */
 86 DEFINE_SPINLOCK(hugetlb_lock);
 87 
 88 /*
 89  * Serializes faults on the same logical page.  This is used to
 90  * prevent spurious OOMs when the hugepage pool is fully utilized.
 91  */
 92 static int num_fault_mutexes;
 93 struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;
 94 
 95 /* Forward declaration */
 96 static int hugetlb_acct_memory(struct hstate *h, long delta);
 97 
 98 static inline bool subpool_is_free(struct hugepage_subpool *spool)
 99 {
100         if (spool->count)
101                 return false;
102         if (spool->max_hpages != -1)
103                 return spool->used_hpages == 0;
104         if (spool->min_hpages != -1)
105                 return spool->rsv_hpages == spool->min_hpages;
106 
107         return true;
108 }
109 
110 static inline void unlock_or_release_subpool(struct hugepage_subpool *spool,
111                                                 unsigned long irq_flags)
112 {
113         spin_unlock_irqrestore(&spool->lock, irq_flags);
114 
115         /* If no pages are used, and no other handles to the subpool
116          * remain, give up any reservations based on minimum size and
117          * free the subpool */
118         if (subpool_is_free(spool)) {
119                 if (spool->min_hpages != -1)
120                         hugetlb_acct_memory(spool->hstate,
121                                                 -spool->min_hpages);
122                 kfree(spool);
123         }
124 }
125 
126 struct hugepage_subpool *hugepage_new_subpool(struct hstate *h, long max_hpages,
127                                                 long min_hpages)
128 {
129         struct hugepage_subpool *spool;
130 
131         spool = kzalloc(sizeof(*spool), GFP_KERNEL);
132         if (!spool)
133                 return NULL;
134 
135         spin_lock_init(&spool->lock);
136         spool->count = 1;
137         spool->max_hpages = max_hpages;
138         spool->hstate = h;
139         spool->min_hpages = min_hpages;
140 
141         if (min_hpages != -1 && hugetlb_acct_memory(h, min_hpages)) {
142                 kfree(spool);
143                 return NULL;
144         }
145         spool->rsv_hpages = min_hpages;
146 
147         return spool;
148 }
149 
150 void hugepage_put_subpool(struct hugepage_subpool *spool)
151 {
152         unsigned long flags;
153 
154         spin_lock_irqsave(&spool->lock, flags);
155         BUG_ON(!spool->count);
156         spool->count--;
157         unlock_or_release_subpool(spool, flags);
158 }
159 
160 /*
161  * Subpool accounting for allocating and reserving pages.
162  * Return -ENOMEM if there are not enough resources to satisfy the
163  * request.  Otherwise, return the number of pages by which the
164  * global pools must be adjusted (upward).  The returned value may
165  * only be different than the passed value (delta) in the case where
166  * a subpool minimum size must be maintained.
167  */
168 static long hugepage_subpool_get_pages(struct hugepage_subpool *spool,
169                                       long delta)
170 {
171         long ret = delta;
172 
173         if (!spool)
174                 return ret;
175 
176         spin_lock_irq(&spool->lock);
177 
178         if (spool->max_hpages != -1) {          /* maximum size accounting */
179                 if ((spool->used_hpages + delta) <= spool->max_hpages)
180                         spool->used_hpages += delta;
181                 else {
182                         ret = -ENOMEM;
183                         goto unlock_ret;
184                 }
185         }
186 
187         /* minimum size accounting */
188         if (spool->min_hpages != -1 && spool->rsv_hpages) {
189                 if (delta > spool->rsv_hpages) {
190                         /*
191                          * Asking for more reserves than those already taken on
192                          * behalf of subpool.  Return difference.
193                          */
194                         ret = delta - spool->rsv_hpages;
195                         spool->rsv_hpages = 0;
196                 } else {
197                         ret = 0;        /* reserves already accounted for */
198                         spool->rsv_hpages -= delta;
199                 }
200         }
201 
202 unlock_ret:
203         spin_unlock_irq(&spool->lock);
204         return ret;
205 }
206 
207 /*
208  * Subpool accounting for freeing and unreserving pages.
209  * Return the number of global page reservations that must be dropped.
210  * The return value may only be different than the passed value (delta)
211  * in the case where a subpool minimum size must be maintained.
212  */
213 static long hugepage_subpool_put_pages(struct hugepage_subpool *spool,
214                                        long delta)
215 {
216         long ret = delta;
217         unsigned long flags;
218 
219         if (!spool)
220                 return delta;
221 
222         spin_lock_irqsave(&spool->lock, flags);
223 
224         if (spool->max_hpages != -1)            /* maximum size accounting */
225                 spool->used_hpages -= delta;
226 
227          /* minimum size accounting */
228         if (spool->min_hpages != -1 && spool->used_hpages < spool->min_hpages) {
229                 if (spool->rsv_hpages + delta <= spool->min_hpages)
230                         ret = 0;
231                 else
232                         ret = spool->rsv_hpages + delta - spool->min_hpages;
233 
234                 spool->rsv_hpages += delta;
235                 if (spool->rsv_hpages > spool->min_hpages)
236                         spool->rsv_hpages = spool->min_hpages;
237         }
238 
239         /*
240          * If hugetlbfs_put_super couldn't free spool due to an outstanding
241          * quota reference, free it now.
242          */
243         unlock_or_release_subpool(spool, flags);
244 
245         return ret;
246 }
247 
248 static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
249 {
250         return HUGETLBFS_SB(inode->i_sb)->spool;
251 }
252 
253 static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
254 {
255         return subpool_inode(file_inode(vma->vm_file));
256 }
257 
258 /* Helper that removes a struct file_region from the resv_map cache and returns
259  * it for use.
260  */
261 static struct file_region *
262 get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
263 {
264         struct file_region *nrg = NULL;
265 
266         VM_BUG_ON(resv->region_cache_count <= 0);
267 
268         resv->region_cache_count--;
269         nrg = list_first_entry(&resv->region_cache, struct file_region, link);
270         list_del(&nrg->link);
271 
272         nrg->from = from;
273         nrg->to = to;
274 
275         return nrg;
276 }
277 
278 static void copy_hugetlb_cgroup_uncharge_info(struct file_region *nrg,
279                                               struct file_region *rg)
280 {
281 #ifdef CONFIG_CGROUP_HUGETLB
282         nrg->reservation_counter = rg->reservation_counter;
283         nrg->css = rg->css;
284         if (rg->css)
285                 css_get(rg->css);
286 #endif
287 }
288 
289 /* Helper that records hugetlb_cgroup uncharge info. */
290 static void record_hugetlb_cgroup_uncharge_info(struct hugetlb_cgroup *h_cg,
291                                                 struct hstate *h,
292                                                 struct resv_map *resv,
293                                                 struct file_region *nrg)
294 {
295 #ifdef CONFIG_CGROUP_HUGETLB
296         if (h_cg) {
297                 nrg->reservation_counter =
298                         &h_cg->rsvd_hugepage[hstate_index(h)];
299                 nrg->css = &h_cg->css;
300                 /*
301                  * The caller will hold exactly one h_cg->css reference for the
302                  * whole contiguous reservation region. But this area might be
303                  * scattered when there are already some file_regions reside in
304                  * it. As a result, many file_regions may share only one css
305                  * reference. In order to ensure that one file_region must hold
306                  * exactly one h_cg->css reference, we should do css_get for
307                  * each file_region and leave the reference held by caller
308                  * untouched.
309                  */
310                 css_get(&h_cg->css);
311                 if (!resv->pages_per_hpage)
312                         resv->pages_per_hpage = pages_per_huge_page(h);
313                 /* pages_per_hpage should be the same for all entries in
314                  * a resv_map.
315                  */
316                 VM_BUG_ON(resv->pages_per_hpage != pages_per_huge_page(h));
317         } else {
318                 nrg->reservation_counter = NULL;
319                 nrg->css = NULL;
320         }
321 #endif
322 }
323 
324 static void put_uncharge_info(struct file_region *rg)
325 {
326 #ifdef CONFIG_CGROUP_HUGETLB
327         if (rg->css)
328                 css_put(rg->css);
329 #endif
330 }
331 
332 static bool has_same_uncharge_info(struct file_region *rg,
333                                    struct file_region *org)
334 {
335 #ifdef CONFIG_CGROUP_HUGETLB
336         return rg->reservation_counter == org->reservation_counter &&
337                rg->css == org->css;
338 
339 #else
340         return true;
341 #endif
342 }
343 
344 static void coalesce_file_region(struct resv_map *resv, struct file_region *rg)
345 {
346         struct file_region *nrg = NULL, *prg = NULL;
347 
348         prg = list_prev_entry(rg, link);
349         if (&prg->link != &resv->regions && prg->to == rg->from &&
350             has_same_uncharge_info(prg, rg)) {
351                 prg->to = rg->to;
352 
353                 list_del(&rg->link);
354                 put_uncharge_info(rg);
355                 kfree(rg);
356 
357                 rg = prg;
358         }
359 
360         nrg = list_next_entry(rg, link);
361         if (&nrg->link != &resv->regions && nrg->from == rg->to &&
362             has_same_uncharge_info(nrg, rg)) {
363                 nrg->from = rg->from;
364 
365                 list_del(&rg->link);
366                 put_uncharge_info(rg);
367                 kfree(rg);
368         }
369 }
370 
371 static inline long
372 hugetlb_resv_map_add(struct resv_map *map, struct file_region *rg, long from,
373                      long to, struct hstate *h, struct hugetlb_cgroup *cg,
374                      long *regions_needed)
375 {
376         struct file_region *nrg;
377 
378         if (!regions_needed) {
379                 nrg = get_file_region_entry_from_cache(map, from, to);
380                 record_hugetlb_cgroup_uncharge_info(cg, h, map, nrg);
381                 list_add(&nrg->link, rg->link.prev);
382                 coalesce_file_region(map, nrg);
383         } else
384                 *regions_needed += 1;
385 
386         return to - from;
387 }
388 
389 /*
390  * Must be called with resv->lock held.
391  *
392  * Calling this with regions_needed != NULL will count the number of pages
393  * to be added but will not modify the linked list. And regions_needed will
394  * indicate the number of file_regions needed in the cache to carry out to add
395  * the regions for this range.
396  */
397 static long add_reservation_in_range(struct resv_map *resv, long f, long t,
398                                      struct hugetlb_cgroup *h_cg,
399                                      struct hstate *h, long *regions_needed)
400 {
401         long add = 0;
402         struct list_head *head = &resv->regions;
403         long last_accounted_offset = f;
404         struct file_region *rg = NULL, *trg = NULL;
405 
406         if (regions_needed)
407                 *regions_needed = 0;
408 
409         /* In this loop, we essentially handle an entry for the range
410          * [last_accounted_offset, rg->from), at every iteration, with some
411          * bounds checking.
412          */
413         list_for_each_entry_safe(rg, trg, head, link) {
414                 /* Skip irrelevant regions that start before our range. */
415                 if (rg->from < f) {
416                         /* If this region ends after the last accounted offset,
417                          * then we need to update last_accounted_offset.
418                          */
419                         if (rg->to > last_accounted_offset)
420                                 last_accounted_offset = rg->to;
421                         continue;
422                 }
423 
424                 /* When we find a region that starts beyond our range, we've
425                  * finished.
426                  */
427                 if (rg->from >= t)
428                         break;
429 
430                 /* Add an entry for last_accounted_offset -> rg->from, and
431                  * update last_accounted_offset.
432                  */
433                 if (rg->from > last_accounted_offset)
434                         add += hugetlb_resv_map_add(resv, rg,
435                                                     last_accounted_offset,
436                                                     rg->from, h, h_cg,
437                                                     regions_needed);
438 
439                 last_accounted_offset = rg->to;
440         }
441 
442         /* Handle the case where our range extends beyond
443          * last_accounted_offset.
444          */
445         if (last_accounted_offset < t)
446                 add += hugetlb_resv_map_add(resv, rg, last_accounted_offset,
447                                             t, h, h_cg, regions_needed);
448 
449         return add;
450 }
451 
452 /* Must be called with resv->lock acquired. Will drop lock to allocate entries.
453  */
454 static int allocate_file_region_entries(struct resv_map *resv,
455                                         int regions_needed)
456         __must_hold(&resv->lock)
457 {
458         struct list_head allocated_regions;
459         int to_allocate = 0, i = 0;
460         struct file_region *trg = NULL, *rg = NULL;
461 
462         VM_BUG_ON(regions_needed < 0);
463 
464         INIT_LIST_HEAD(&allocated_regions);
465 
466         /*
467          * Check for sufficient descriptors in the cache to accommodate
468          * the number of in progress add operations plus regions_needed.
469          *
470          * This is a while loop because when we drop the lock, some other call
471          * to region_add or region_del may have consumed some region_entries,
472          * so we keep looping here until we finally have enough entries for
473          * (adds_in_progress + regions_needed).
474          */
475         while (resv->region_cache_count <
476                (resv->adds_in_progress + regions_needed)) {
477                 to_allocate = resv->adds_in_progress + regions_needed -
478                               resv->region_cache_count;
479 
480                 /* At this point, we should have enough entries in the cache
481                  * for all the existing adds_in_progress. We should only be
482                  * needing to allocate for regions_needed.
483                  */
484                 VM_BUG_ON(resv->region_cache_count < resv->adds_in_progress);
485 
486                 spin_unlock(&resv->lock);
487                 for (i = 0; i < to_allocate; i++) {
488                         trg = kmalloc(sizeof(*trg), GFP_KERNEL);
489                         if (!trg)
490                                 goto out_of_memory;
491                         list_add(&trg->link, &allocated_regions);
492                 }
493 
494                 spin_lock(&resv->lock);
495 
496                 list_splice(&allocated_regions, &resv->region_cache);
497                 resv->region_cache_count += to_allocate;
498         }
499 
500         return 0;
501 
502 out_of_memory:
503         list_for_each_entry_safe(rg, trg, &allocated_regions, link) {
504                 list_del(&rg->link);
505                 kfree(rg);
506         }
507         return -ENOMEM;
508 }
509 
510 /*
511  * Add the huge page range represented by [f, t) to the reserve
512  * map.  Regions will be taken from the cache to fill in this range.
513  * Sufficient regions should exist in the cache due to the previous
514  * call to region_chg with the same range, but in some cases the cache will not
515  * have sufficient entries due to races with other code doing region_add or
516  * region_del.  The extra needed entries will be allocated.
517  *
518  * regions_needed is the out value provided by a previous call to region_chg.
519  *
520  * Return the number of new huge pages added to the map.  This number is greater
521  * than or equal to zero.  If file_region entries needed to be allocated for
522  * this operation and we were not able to allocate, it returns -ENOMEM.
523  * region_add of regions of length 1 never allocate file_regions and cannot
524  * fail; region_chg will always allocate at least 1 entry and a region_add for
525  * 1 page will only require at most 1 entry.
526  */
527 static long region_add(struct resv_map *resv, long f, long t,
528                        long in_regions_needed, struct hstate *h,
529                        struct hugetlb_cgroup *h_cg)
530 {
531         long add = 0, actual_regions_needed = 0;
532 
533         spin_lock(&resv->lock);
534 retry:
535 
536         /* Count how many regions are actually needed to execute this add. */
537         add_reservation_in_range(resv, f, t, NULL, NULL,
538                                  &actual_regions_needed);
539 
540         /*
541          * Check for sufficient descriptors in the cache to accommodate
542          * this add operation. Note that actual_regions_needed may be greater
543          * than in_regions_needed, as the resv_map may have been modified since
544          * the region_chg call. In this case, we need to make sure that we
545          * allocate extra entries, such that we have enough for all the
546          * existing adds_in_progress, plus the excess needed for this
547          * operation.
548          */
549         if (actual_regions_needed > in_regions_needed &&
550             resv->region_cache_count <
551                     resv->adds_in_progress +
552                             (actual_regions_needed - in_regions_needed)) {
553                 /* region_add operation of range 1 should never need to
554                  * allocate file_region entries.
555                  */
556                 VM_BUG_ON(t - f <= 1);
557 
558                 if (allocate_file_region_entries(
559                             resv, actual_regions_needed - in_regions_needed)) {
560                         return -ENOMEM;
561                 }
562 
563                 goto retry;
564         }
565 
566         add = add_reservation_in_range(resv, f, t, h_cg, h, NULL);
567 
568         resv->adds_in_progress -= in_regions_needed;
569 
570         spin_unlock(&resv->lock);
571         return add;
572 }
573 
574 /*
575  * Examine the existing reserve map and determine how many
576  * huge pages in the specified range [f, t) are NOT currently
577  * represented.  This routine is called before a subsequent
578  * call to region_add that will actually modify the reserve
579  * map to add the specified range [f, t).  region_chg does
580  * not change the number of huge pages represented by the
581  * map.  A number of new file_region structures is added to the cache as a
582  * placeholder, for the subsequent region_add call to use. At least 1
583  * file_region structure is added.
584  *
585  * out_regions_needed is the number of regions added to the
586  * resv->adds_in_progress.  This value needs to be provided to a follow up call
587  * to region_add or region_abort for proper accounting.
588  *
589  * Returns the number of huge pages that need to be added to the existing
590  * reservation map for the range [f, t).  This number is greater or equal to
591  * zero.  -ENOMEM is returned if a new file_region structure or cache entry
592  * is needed and can not be allocated.
593  */
594 static long region_chg(struct resv_map *resv, long f, long t,
595                        long *out_regions_needed)
596 {
597         long chg = 0;
598 
599         spin_lock(&resv->lock);
600 
601         /* Count how many hugepages in this range are NOT represented. */
602         chg = add_reservation_in_range(resv, f, t, NULL, NULL,
603                                        out_regions_needed);
604 
605         if (*out_regions_needed == 0)
606                 *out_regions_needed = 1;
607 
608         if (allocate_file_region_entries(resv, *out_regions_needed))
609                 return -ENOMEM;
610 
611         resv->adds_in_progress += *out_regions_needed;
612 
613         spin_unlock(&resv->lock);
614         return chg;
615 }
616 
617 /*
618  * Abort the in progress add operation.  The adds_in_progress field
619  * of the resv_map keeps track of the operations in progress between
620  * calls to region_chg and region_add.  Operations are sometimes
621  * aborted after the call to region_chg.  In such cases, region_abort
622  * is called to decrement the adds_in_progress counter. regions_needed
623  * is the value returned by the region_chg call, it is used to decrement
624  * the adds_in_progress counter.
625  *
626  * NOTE: The range arguments [f, t) are not needed or used in this
627  * routine.  They are kept to make reading the calling code easier as
628  * arguments will match the associated region_chg call.
629  */
630 static void region_abort(struct resv_map *resv, long f, long t,
631                          long regions_needed)
632 {
633         spin_lock(&resv->lock);
634         VM_BUG_ON(!resv->region_cache_count);
635         resv->adds_in_progress -= regions_needed;
636         spin_unlock(&resv->lock);
637 }
638 
639 /*
640  * Delete the specified range [f, t) from the reserve map.  If the
641  * t parameter is LONG_MAX, this indicates that ALL regions after f
642  * should be deleted.  Locate the regions which intersect [f, t)
643  * and either trim, delete or split the existing regions.
644  *
645  * Returns the number of huge pages deleted from the reserve map.
646  * In the normal case, the return value is zero or more.  In the
647  * case where a region must be split, a new region descriptor must
648  * be allocated.  If the allocation fails, -ENOMEM will be returned.
649  * NOTE: If the parameter t == LONG_MAX, then we will never split
650  * a region and possibly return -ENOMEM.  Callers specifying
651  * t == LONG_MAX do not need to check for -ENOMEM error.
652  */
653 static long region_del(struct resv_map *resv, long f, long t)
654 {
655         struct list_head *head = &resv->regions;
656         struct file_region *rg, *trg;
657         struct file_region *nrg = NULL;
658         long del = 0;
659 
660 retry:
661         spin_lock(&resv->lock);
662         list_for_each_entry_safe(rg, trg, head, link) {
663                 /*
664                  * Skip regions before the range to be deleted.  file_region
665                  * ranges are normally of the form [from, to).  However, there
666                  * may be a "placeholder" entry in the map which is of the form
667                  * (from, to) with from == to.  Check for placeholder entries
668                  * at the beginning of the range to be deleted.
669                  */
670                 if (rg->to <= f && (rg->to != rg->from || rg->to != f))
671                         continue;
672 
673                 if (rg->from >= t)
674                         break;
675 
676                 if (f > rg->from && t < rg->to) { /* Must split region */
677                         /*
678                          * Check for an entry in the cache before dropping
679                          * lock and attempting allocation.
680                          */
681                         if (!nrg &&
682                             resv->region_cache_count > resv->adds_in_progress) {
683                                 nrg = list_first_entry(&resv->region_cache,
684                                                         struct file_region,
685                                                         link);
686                                 list_del(&nrg->link);
687                                 resv->region_cache_count--;
688                         }
689 
690                         if (!nrg) {
691                                 spin_unlock(&resv->lock);
692                                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
693                                 if (!nrg)
694                                         return -ENOMEM;
695                                 goto retry;
696                         }
697 
698                         del += t - f;
699                         hugetlb_cgroup_uncharge_file_region(
700                                 resv, rg, t - f, false);
701 
702                         /* New entry for end of split region */
703                         nrg->from = t;
704                         nrg->to = rg->to;
705 
706                         copy_hugetlb_cgroup_uncharge_info(nrg, rg);
707 
708                         INIT_LIST_HEAD(&nrg->link);
709 
710                         /* Original entry is trimmed */
711                         rg->to = f;
712 
713                         list_add(&nrg->link, &rg->link);
714                         nrg = NULL;
715                         break;
716                 }
717 
718                 if (f <= rg->from && t >= rg->to) { /* Remove entire region */
719                         del += rg->to - rg->from;
720                         hugetlb_cgroup_uncharge_file_region(resv, rg,
721                                                             rg->to - rg->from, true);
722                         list_del(&rg->link);
723                         kfree(rg);
724                         continue;
725                 }
726 
727                 if (f <= rg->from) {    /* Trim beginning of region */
728                         hugetlb_cgroup_uncharge_file_region(resv, rg,
729                                                             t - rg->from, false);
730 
731                         del += t - rg->from;
732                         rg->from = t;
733                 } else {                /* Trim end of region */
734                         hugetlb_cgroup_uncharge_file_region(resv, rg,
735                                                             rg->to - f, false);
736 
737                         del += rg->to - f;
738                         rg->to = f;
739                 }
740         }
741 
742         spin_unlock(&resv->lock);
743         kfree(nrg);
744         return del;
745 }
746 
747 /*
748  * A rare out of memory error was encountered which prevented removal of
749  * the reserve map region for a page.  The huge page itself was free'ed
750  * and removed from the page cache.  This routine will adjust the subpool
751  * usage count, and the global reserve count if needed.  By incrementing
752  * these counts, the reserve map entry which could not be deleted will
753  * appear as a "reserved" entry instead of simply dangling with incorrect
754  * counts.
755  */
756 void hugetlb_fix_reserve_counts(struct inode *inode)
757 {
758         struct hugepage_subpool *spool = subpool_inode(inode);
759         long rsv_adjust;
760         bool reserved = false;
761 
762         rsv_adjust = hugepage_subpool_get_pages(spool, 1);
763         if (rsv_adjust > 0) {
764                 struct hstate *h = hstate_inode(inode);
765 
766                 if (!hugetlb_acct_memory(h, 1))
767                         reserved = true;
768         } else if (!rsv_adjust) {
769                 reserved = true;
770         }
771 
772         if (!reserved)
773                 pr_warn("hugetlb: Huge Page Reserved count may go negative.\n");
774 }
775 
776 /*
777  * Count and return the number of huge pages in the reserve map
778  * that intersect with the range [f, t).
779  */
780 static long region_count(struct resv_map *resv, long f, long t)
781 {
782         struct list_head *head = &resv->regions;
783         struct file_region *rg;
784         long chg = 0;
785 
786         spin_lock(&resv->lock);
787         /* Locate each segment we overlap with, and count that overlap. */
788         list_for_each_entry(rg, head, link) {
789                 long seg_from;
790                 long seg_to;
791 
792                 if (rg->to <= f)
793                         continue;
794                 if (rg->from >= t)
795                         break;
796 
797                 seg_from = max(rg->from, f);
798                 seg_to = min(rg->to, t);
799 
800                 chg += seg_to - seg_from;
801         }
802         spin_unlock(&resv->lock);
803 
804         return chg;
805 }
806 
807 /*
808  * Convert the address within this vma to the page offset within
809  * the mapping, in pagecache page units; huge pages here.
810  */
811 static pgoff_t vma_hugecache_offset(struct hstate *h,
812                         struct vm_area_struct *vma, unsigned long address)
813 {
814         return ((address - vma->vm_start) >> huge_page_shift(h)) +
815                         (vma->vm_pgoff >> huge_page_order(h));
816 }
817 
818 pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
819                                      unsigned long address)
820 {
821         return vma_hugecache_offset(hstate_vma(vma), vma, address);
822 }
823 EXPORT_SYMBOL_GPL(linear_hugepage_index);
824 
825 /*
826  * Return the size of the pages allocated when backing a VMA. In the majority
827  * cases this will be same size as used by the page table entries.
828  */
829 unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
830 {
831         if (vma->vm_ops && vma->vm_ops->pagesize)
832                 return vma->vm_ops->pagesize(vma);
833         return PAGE_SIZE;
834 }
835 EXPORT_SYMBOL_GPL(vma_kernel_pagesize);
836 
837 /*
838  * Return the page size being used by the MMU to back a VMA. In the majority
839  * of cases, the page size used by the kernel matches the MMU size. On
840  * architectures where it differs, an architecture-specific 'strong'
841  * version of this symbol is required.
842  */
843 __weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
844 {
845         return vma_kernel_pagesize(vma);
846 }
847 
848 /*
849  * Flags for MAP_PRIVATE reservations.  These are stored in the bottom
850  * bits of the reservation map pointer, which are always clear due to
851  * alignment.
852  */
853 #define HPAGE_RESV_OWNER    (1UL << 0)
854 #define HPAGE_RESV_UNMAPPED (1UL << 1)
855 #define HPAGE_RESV_MASK (HPAGE_RESV_OWNER | HPAGE_RESV_UNMAPPED)
856 
857 /*
858  * These helpers are used to track how many pages are reserved for
859  * faults in a MAP_PRIVATE mapping. Only the process that called mmap()
860  * is guaranteed to have their future faults succeed.
861  *
862  * With the exception of reset_vma_resv_huge_pages() which is called at fork(),
863  * the reserve counters are updated with the hugetlb_lock held. It is safe
864  * to reset the VMA at fork() time as it is not in use yet and there is no
865  * chance of the global counters getting corrupted as a result of the values.
866  *
867  * The private mapping reservation is represented in a subtly different
868  * manner to a shared mapping.  A shared mapping has a region map associated
869  * with the underlying file, this region map represents the backing file
870  * pages which have ever had a reservation assigned which this persists even
871  * after the page is instantiated.  A private mapping has a region map
872  * associated with the original mmap which is attached to all VMAs which
873  * reference it, this region map represents those offsets which have consumed
874  * reservation ie. where pages have been instantiated.
875  */
876 static unsigned long get_vma_private_data(struct vm_area_struct *vma)
877 {
878         return (unsigned long)vma->vm_private_data;
879 }
880 
881 static void set_vma_private_data(struct vm_area_struct *vma,
882                                                         unsigned long value)
883 {
884         vma->vm_private_data = (void *)value;
885 }
886 
887 static void
888 resv_map_set_hugetlb_cgroup_uncharge_info(struct resv_map *resv_map,
889                                           struct hugetlb_cgroup *h_cg,
890                                           struct hstate *h)
891 {
892 #ifdef CONFIG_CGROUP_HUGETLB
893         if (!h_cg || !h) {
894                 resv_map->reservation_counter = NULL;
895                 resv_map->pages_per_hpage = 0;
896                 resv_map->css = NULL;
897         } else {
898                 resv_map->reservation_counter =
899                         &h_cg->rsvd_hugepage[hstate_index(h)];
900                 resv_map->pages_per_hpage = pages_per_huge_page(h);
901                 resv_map->css = &h_cg->css;
902         }
903 #endif
904 }
905 
906 struct resv_map *resv_map_alloc(void)
907 {
908         struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
909         struct file_region *rg = kmalloc(sizeof(*rg), GFP_KERNEL);
910 
911         if (!resv_map || !rg) {
912                 kfree(resv_map);
913                 kfree(rg);
914                 return NULL;
915         }
916 
917         kref_init(&resv_map->refs);
918         spin_lock_init(&resv_map->lock);
919         INIT_LIST_HEAD(&resv_map->regions);
920 
921         resv_map->adds_in_progress = 0;
922         /*
923          * Initialize these to 0. On shared mappings, 0's here indicate these
924          * fields don't do cgroup accounting. On private mappings, these will be
925          * re-initialized to the proper values, to indicate that hugetlb cgroup
926          * reservations are to be un-charged from here.
927          */
928         resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, NULL, NULL);
929 
930         INIT_LIST_HEAD(&resv_map->region_cache);
931         list_add(&rg->link, &resv_map->region_cache);
932         resv_map->region_cache_count = 1;
933 
934         return resv_map;
935 }
936 
937 void resv_map_release(struct kref *ref)
938 {
939         struct resv_map *resv_map = container_of(ref, struct resv_map, refs);
940         struct list_head *head = &resv_map->region_cache;
941         struct file_region *rg, *trg;
942 
943         /* Clear out any active regions before we release the map. */
944         region_del(resv_map, 0, LONG_MAX);
945 
946         /* ... and any entries left in the cache */
947         list_for_each_entry_safe(rg, trg, head, link) {
948                 list_del(&rg->link);
949                 kfree(rg);
950         }
951 
952         VM_BUG_ON(resv_map->adds_in_progress);
953 
954         kfree(resv_map);
955 }
956 
957 static inline struct resv_map *inode_resv_map(struct inode *inode)
958 {
959         /*
960          * At inode evict time, i_mapping may not point to the original
961          * address space within the inode.  This original address space
962          * contains the pointer to the resv_map.  So, always use the
963          * address space embedded within the inode.
964          * The VERY common case is inode->mapping == &inode->i_data but,
965          * this may not be true for device special inodes.
966          */
967         return (struct resv_map *)(&inode->i_data)->private_data;
968 }
969 
970 static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
971 {
972         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
973         if (vma->vm_flags & VM_MAYSHARE) {
974                 struct address_space *mapping = vma->vm_file->f_mapping;
975                 struct inode *inode = mapping->host;
976 
977                 return inode_resv_map(inode);
978 
979         } else {
980                 return (struct resv_map *)(get_vma_private_data(vma) &
981                                                         ~HPAGE_RESV_MASK);
982         }
983 }
984 
985 static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
986 {
987         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
988         VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);
989 
990         set_vma_private_data(vma, (get_vma_private_data(vma) &
991                                 HPAGE_RESV_MASK) | (unsigned long)map);
992 }
993 
994 static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
995 {
996         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
997         VM_BUG_ON_VMA(vma->vm_flags & VM_MAYSHARE, vma);
998 
999         set_vma_private_data(vma, get_vma_private_data(vma) | flags);
1000 }
1001 
1002 static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
1003 {
1004         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
1005 
1006         return (get_vma_private_data(vma) & flag) != 0;
1007 }
1008 
1009 /* Reset counters to 0 and clear all HPAGE_RESV_* flags */
1010 void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
1011 {
1012         VM_BUG_ON_VMA(!is_vm_hugetlb_page(vma), vma);
1013         if (!(vma->vm_flags & VM_MAYSHARE))
1014                 vma->vm_private_data = (void *)0;
1015 }
1016 
1017 /*
1018  * Reset and decrement one ref on hugepage private reservation.
1019  * Called with mm->mmap_sem writer semaphore held.
1020  * This function should be only used by move_vma() and operate on
1021  * same sized vma. It should never come here with last ref on the
1022  * reservation.
1023  */
1024 void clear_vma_resv_huge_pages(struct vm_area_struct *vma)
1025 {
1026         /*
1027          * Clear the old hugetlb private page reservation.
1028          * It has already been transferred to new_vma.
1029          *
1030          * During a mremap() operation of a hugetlb vma we call move_vma()
1031          * which copies vma into new_vma and unmaps vma. After the copy
1032          * operation both new_vma and vma share a reference to the resv_map
1033          * struct, and at that point vma is about to be unmapped. We don't
1034          * want to return the reservation to the pool at unmap of vma because
1035          * the reservation still lives on in new_vma, so simply decrement the
1036          * ref here and remove the resv_map reference from this vma.
1037          */
1038         struct resv_map *reservations = vma_resv_map(vma);
1039 
1040         if (reservations && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
1041                 resv_map_put_hugetlb_cgroup_uncharge_info(reservations);
1042                 kref_put(&reservations->refs, resv_map_release);
1043         }
1044 
1045         reset_vma_resv_huge_pages(vma);
1046 }
1047 
1048 /* Returns true if the VMA has associated reserve pages */
1049 static bool vma_has_reserves(struct vm_area_struct *vma, long chg)
1050 {
1051         if (vma->vm_flags & VM_NORESERVE) {
1052                 /*
1053                  * This address is already reserved by other process(chg == 0),
1054                  * so, we should decrement reserved count. Without decrementing,
1055                  * reserve count remains after releasing inode, because this
1056                  * allocated page will go into page cache and is regarded as
1057                  * coming from reserved pool in releasing step.  Currently, we
1058                  * don't have any other solution to deal with this situation
1059                  * properly, so add work-around here.
1060                  */
1061                 if (vma->vm_flags & VM_MAYSHARE && chg == 0)
1062                         return true;
1063                 else
1064                         return false;
1065         }
1066 
1067         /* Shared mappings always use reserves */
1068         if (vma->vm_flags & VM_MAYSHARE) {
1069                 /*
1070                  * We know VM_NORESERVE is not set.  Therefore, there SHOULD
1071                  * be a region map for all pages.  The only situation where
1072                  * there is no region map is if a hole was punched via
1073                  * fallocate.  In this case, there really are no reserves to
1074                  * use.  This situation is indicated if chg != 0.
1075                  */
1076                 if (chg)
1077                         return false;
1078                 else
1079                         return true;
1080         }
1081 
1082         /*
1083          * Only the process that called mmap() has reserves for
1084          * private mappings.
1085          */
1086         if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
1087                 /*
1088                  * Like the shared case above, a hole punch or truncate
1089                  * could have been performed on the private mapping.
1090                  * Examine the value of chg to determine if reserves
1091                  * actually exist or were previously consumed.
1092                  * Very Subtle - The value of chg comes from a previous
1093                  * call to vma_needs_reserves().  The reserve map for
1094                  * private mappings has different (opposite) semantics
1095                  * than that of shared mappings.  vma_needs_reserves()
1096                  * has already taken this difference in semantics into
1097                  * account.  Therefore, the meaning of chg is the same
1098                  * as in the shared case above.  Code could easily be
1099                  * combined, but keeping it separate draws attention to
1100                  * subtle differences.
1101                  */
1102                 if (chg)
1103                         return false;
1104                 else
1105                         return true;
1106         }
1107 
1108         return false;
1109 }
1110 
1111 static void enqueue_huge_page(struct hstate *h, struct page *page)
1112 {
1113         int nid = page_to_nid(page);
1114 
1115         lockdep_assert_held(&hugetlb_lock);
1116         VM_BUG_ON_PAGE(page_count(page), page);
1117 
1118         list_move(&page->lru, &h->hugepage_freelists[nid]);
1119         h->free_huge_pages++;
1120         h->free_huge_pages_node[nid]++;
1121         SetHPageFreed(page);
1122 }
1123 
1124 static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
1125 {
1126         struct page *page;
1127         bool pin = !!(current->flags & PF_MEMALLOC_PIN);
1128 
1129         lockdep_assert_held(&hugetlb_lock);
1130         list_for_each_entry(page, &h->hugepage_freelists[nid], lru) {
1131                 if (pin && !is_pinnable_page(page))
1132                         continue;
1133 
1134                 if (PageHWPoison(page))
1135                         continue;
1136 
1137                 list_move(&page->lru, &h->hugepage_activelist);
1138                 set_page_refcounted(page);
1139                 ClearHPageFreed(page);
1140                 h->free_huge_pages--;
1141                 h->free_huge_pages_node[nid]--;
1142                 return page;
1143         }
1144 
1145         return NULL;
1146 }
1147 
1148 static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask, int nid,
1149                 nodemask_t *nmask)
1150 {
1151         unsigned int cpuset_mems_cookie;
1152         struct zonelist *zonelist;
1153         struct zone *zone;
1154         struct zoneref *z;
1155         int node = NUMA_NO_NODE;
1156 
1157         zonelist = node_zonelist(nid, gfp_mask);
1158 
1159 retry_cpuset:
1160         cpuset_mems_cookie = read_mems_allowed_begin();
1161         for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nmask) {
1162                 struct page *page;
1163 
1164                 if (!cpuset_zone_allowed(zone, gfp_mask))
1165                         continue;
1166                 /*
1167                  * no need to ask again on the same node. Pool is node rather than
1168                  * zone aware
1169                  */
1170                 if (zone_to_nid(zone) == node)
1171                         continue;
1172                 node = zone_to_nid(zone);
1173 
1174                 page = dequeue_huge_page_node_exact(h, node);
1175                 if (page)
1176                         return page;
1177         }
1178         if (unlikely(read_mems_allowed_retry(cpuset_mems_cookie)))
1179                 goto retry_cpuset;
1180 
1181         return NULL;
1182 }
1183 
1184 static struct page *dequeue_huge_page_vma(struct hstate *h,
1185                                 struct vm_area_struct *vma,
1186                                 unsigned long address, int avoid_reserve,
1187                                 long chg)
1188 {
1189         struct page *page = NULL;
1190         struct mempolicy *mpol;
1191         gfp_t gfp_mask;
1192         nodemask_t *nodemask;
1193         int nid;
1194 
1195         /*
1196          * A child process with MAP_PRIVATE mappings created by their parent
1197          * have no page reserves. This check ensures that reservations are
1198          * not "stolen". The child may still get SIGKILLed
1199          */
1200         if (!vma_has_reserves(vma, chg) &&
1201                         h->free_huge_pages - h->resv_huge_pages == 0)
1202                 goto err;
1203 
1204         /* If reserves cannot be used, ensure enough pages are in the pool */
1205         if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
1206                 goto err;
1207 
1208         gfp_mask = htlb_alloc_mask(h);
1209         nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
1210 
1211         if (mpol_is_preferred_many(mpol)) {
1212                 page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
1213 
1214                 /* Fallback to all nodes if page==NULL */
1215                 nodemask = NULL;
1216         }
1217 
1218         if (!page)
1219                 page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
1220 
1221         if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
1222                 SetHPageRestoreReserve(page);
1223                 h->resv_huge_pages--;
1224         }
1225 
1226         mpol_cond_put(mpol);
1227         return page;
1228 
1229 err:
1230         return NULL;
1231 }
1232 
1233 /*
1234  * common helper functions for hstate_next_node_to_{alloc|free}.
1235  * We may have allocated or freed a huge page based on a different
1236  * nodes_allowed previously, so h->next_node_to_{alloc|free} might
1237  * be outside of *nodes_allowed.  Ensure that we use an allowed
1238  * node for alloc or free.
1239  */
1240 static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
1241 {
1242         nid = next_node_in(nid, *nodes_allowed);
1243         VM_BUG_ON(nid >= MAX_NUMNODES);
1244 
1245         return nid;
1246 }
1247 
1248 static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
1249 {
1250         if (!node_isset(nid, *nodes_allowed))
1251                 nid = next_node_allowed(nid, nodes_allowed);
1252         return nid;
1253 }
1254 
1255 /*
1256  * returns the previously saved node ["this node"] from which to
1257  * allocate a persistent huge page for the pool and advance the
1258  * next node from which to allocate, handling wrap at end of node
1259  * mask.
1260  */
1261 static int hstate_next_node_to_alloc(struct hstate *h,
1262                                         nodemask_t *nodes_allowed)
1263 {
1264         int nid;
1265 
1266         VM_BUG_ON(!nodes_allowed);
1267 
1268         nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
1269         h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
1270 
1271         return nid;
1272 }
1273 
1274 /*
1275  * helper for remove_pool_huge_page() - return the previously saved
1276  * node ["this node"] from which to free a huge page.  Advance the
1277  * next node id whether or not we find a free huge page to free so
1278  * that the next attempt to free addresses the next node.
1279  */
1280 static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
1281 {
1282         int nid;
1283 
1284         VM_BUG_ON(!nodes_allowed);
1285 
1286         nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
1287         h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);
1288 
1289         return nid;
1290 }
1291 
1292 #define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask)           \
1293         for (nr_nodes = nodes_weight(*mask);                            \
1294                 nr_nodes > 0 &&                                         \
1295                 ((node = hstate_next_node_to_alloc(hs, mask)) || 1);    \
1296                 nr_nodes--)
1297 
1298 #define for_each_node_mask_to_free(hs, nr_nodes, node, mask)            \
1299         for (nr_nodes = nodes_weight(*mask);                            \
1300                 nr_nodes > 0 &&                                         \
1301                 ((node = hstate_next_node_to_free(hs, mask)) || 1);     \
1302                 nr_nodes--)
1303 
1304 /* used to demote non-gigantic_huge pages as well */
1305 static void __destroy_compound_gigantic_page(struct page *page,
1306                                         unsigned int order, bool demote)
1307 {
1308         int i;
1309         int nr_pages = 1 << order;
1310         struct page *p = page + 1;
1311 
1312         atomic_set(compound_mapcount_ptr(page), 0);
1313         atomic_set(compound_pincount_ptr(page), 0);
1314 
1315         for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
1316                 p->mapping = NULL;
1317                 clear_compound_head(p);
1318                 if (!demote)
1319                         set_page_refcounted(p);
1320         }
1321 
1322         set_compound_order(page, 0);
1323         page[1].compound_nr = 0;
1324         __ClearPageHead(page);
1325 }
1326 
1327 static void destroy_compound_hugetlb_page_for_demote(struct page *page,
1328                                         unsigned int order)
1329 {
1330         __destroy_compound_gigantic_page(page, order, true);
1331 }
1332 
1333 #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
1334 static void destroy_compound_gigantic_page(struct page *page,
1335                                         unsigned int order)
1336 {
1337         __destroy_compound_gigantic_page(page, order, false);
1338 }
1339 
1340 static void free_gigantic_page(struct page *page, unsigned int order)
1341 {
1342         /*
1343          * If the page isn't allocated using the cma allocator,
1344          * cma_release() returns false.
1345          */
1346 #ifdef CONFIG_CMA
1347         if (cma_release(hugetlb_cma[page_to_nid(page)], page, 1 << order))
1348                 return;
1349 #endif
1350 
1351         free_contig_range(page_to_pfn(page), 1 << order);
1352 }
1353 
1354 #ifdef CONFIG_CONTIG_ALLOC
1355 static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
1356                 int nid, nodemask_t *nodemask)
1357 {
1358         unsigned long nr_pages = pages_per_huge_page(h);
1359         if (nid == NUMA_NO_NODE)
1360                 nid = numa_mem_id();
1361 
1362 #ifdef CONFIG_CMA
1363         {
1364                 struct page *page;
1365                 int node;
1366 
1367                 if (hugetlb_cma[nid]) {
1368                         page = cma_alloc(hugetlb_cma[nid], nr_pages,
1369                                         huge_page_order(h), true);
1370                         if (page)
1371                                 return page;
1372                 }
1373 
1374                 if (!(gfp_mask & __GFP_THISNODE)) {
1375                         for_each_node_mask(node, *nodemask) {
1376                                 if (node == nid || !hugetlb_cma[node])
1377                                         continue;
1378 
1379                                 page = cma_alloc(hugetlb_cma[node], nr_pages,
1380                                                 huge_page_order(h), true);
1381                                 if (page)
1382                                         return page;
1383                         }
1384                 }
1385         }
1386 #endif
1387 
1388         return alloc_contig_pages(nr_pages, gfp_mask, nid, nodemask);
1389 }
1390 
1391 #else /* !CONFIG_CONTIG_ALLOC */
1392 static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
1393                                         int nid, nodemask_t *nodemask)
1394 {
1395         return NULL;
1396 }
1397 #endif /* CONFIG_CONTIG_ALLOC */
1398 
1399 #else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
1400 static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
1401                                         int nid, nodemask_t *nodemask)
1402 {
1403         return NULL;
1404 }
1405 static inline void free_gigantic_page(struct page *page, unsigned int order) { }
1406 static inline void destroy_compound_gigantic_page(struct page *page,
1407                                                 unsigned int order) { }
1408 #endif
1409 
1410 /*
1411  * Remove hugetlb page from lists, and update dtor so that page appears
1412  * as just a compound page.
1413  *
1414  * A reference is held on the page, except in the case of demote.
1415  *
1416  * Must be called with hugetlb lock held.
1417  */
1418 static void __remove_hugetlb_page(struct hstate *h, struct page *page,
1419                                                         bool adjust_surplus,
1420                                                         bool demote)
1421 {
1422         int nid = page_to_nid(page);
1423 
1424         VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
1425         VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);
1426 
1427         lockdep_assert_held(&hugetlb_lock);
1428         if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
1429                 return;
1430 
1431         list_del(&page->lru);
1432 
1433         if (HPageFreed(page)) {
1434                 h->free_huge_pages--;
1435                 h->free_huge_pages_node[nid]--;
1436         }
1437         if (adjust_surplus) {
1438                 h->surplus_huge_pages--;
1439                 h->surplus_huge_pages_node[nid]--;
1440         }
1441 
1442         /*
1443          * Very subtle
1444          *
1445          * For non-gigantic pages set the destructor to the normal compound
1446          * page dtor.  This is needed in case someone takes an additional
1447          * temporary ref to the page, and freeing is delayed until they drop
1448          * their reference.
1449          *
1450          * For gigantic pages set the destructor to the null dtor.  This
1451          * destructor will never be called.  Before freeing the gigantic
1452          * page destroy_compound_gigantic_page will turn the compound page
1453          * into a simple group of pages.  After this the destructor does not
1454          * apply.
1455          *
1456          * This handles the case where more than one ref is held when and
1457          * after update_and_free_page is called.
1458          *
1459          * In the case of demote we do not ref count the page as it will soon
1460          * be turned into a page of smaller size.
1461          */
1462         if (!demote)
1463                 set_page_refcounted(page);
1464         if (hstate_is_gigantic(h))
1465                 set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
1466         else
1467                 set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
1468 
1469         h->nr_huge_pages--;
1470         h->nr_huge_pages_node[nid]--;
1471 }
1472 
1473 static void remove_hugetlb_page(struct hstate *h, struct page *page,
1474                                                         bool adjust_surplus)
1475 {
1476         __remove_hugetlb_page(h, page, adjust_surplus, false);
1477 }
1478 
1479 static void remove_hugetlb_page_for_demote(struct hstate *h, struct page *page,
1480                                                         bool adjust_surplus)
1481 {
1482         __remove_hugetlb_page(h, page, adjust_surplus, true);
1483 }
1484 
1485 static void add_hugetlb_page(struct hstate *h, struct page *page,
1486                              bool adjust_surplus)
1487 {
1488         int zeroed;
1489         int nid = page_to_nid(page);
1490 
1491         VM_BUG_ON_PAGE(!HPageVmemmapOptimized(page), page);
1492 
1493         lockdep_assert_held(&hugetlb_lock);
1494 
1495         INIT_LIST_HEAD(&page->lru);
1496         h->nr_huge_pages++;
1497         h->nr_huge_pages_node[nid]++;
1498 
1499         if (adjust_surplus) {
1500                 h->surplus_huge_pages++;
1501                 h->surplus_huge_pages_node[nid]++;
1502         }
1503 
1504         set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
1505         set_page_private(page, 0);
1506         SetHPageVmemmapOptimized(page);
1507 
1508         /*
1509          * This page is about to be managed by the hugetlb allocator and
1510          * should have no users.  Drop our reference, and check for others
1511          * just in case.
1512          */
1513         zeroed = put_page_testzero(page);
1514         if (!zeroed)
1515                 /*
1516                  * It is VERY unlikely soneone else has taken a ref on
1517                  * the page.  In this case, we simply return as the
1518                  * hugetlb destructor (free_huge_page) will be called
1519                  * when this other ref is dropped.
1520                  */
1521                 return;
1522 
1523         arch_clear_hugepage_flags(page);
1524         enqueue_huge_page(h, page);
1525 }
1526 
1527 static void __update_and_free_page(struct hstate *h, struct page *page)
1528 {
1529         int i;
1530         struct page *subpage = page;
1531 
1532         if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
1533                 return;
1534 
1535         if (alloc_huge_page_vmemmap(h, page)) {
1536                 spin_lock_irq(&hugetlb_lock);
1537                 /*
1538                  * If we cannot allocate vmemmap pages, just refuse to free the
1539                  * page and put the page back on the hugetlb free list and treat
1540                  * as a surplus page.
1541                  */
1542                 add_hugetlb_page(h, page, true);
1543                 spin_unlock_irq(&hugetlb_lock);
1544                 return;
1545         }
1546 
1547         for (i = 0; i < pages_per_huge_page(h);
1548              i++, subpage = mem_map_next(subpage, page, i)) {
1549                 subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
1550                                 1 << PG_referenced | 1 << PG_dirty |
1551                                 1 << PG_active | 1 << PG_private |
1552                                 1 << PG_writeback);
1553         }
1554 
1555         /*
1556          * Non-gigantic pages demoted from CMA allocated gigantic pages
1557          * need to be given back to CMA in free_gigantic_page.
1558          */
1559         if (hstate_is_gigantic(h) ||
1560             hugetlb_cma_page(page, huge_page_order(h))) {
1561                 destroy_compound_gigantic_page(page, huge_page_order(h));
1562                 free_gigantic_page(page, huge_page_order(h));
1563         } else {
1564                 __free_pages(page, huge_page_order(h));
1565         }
1566 }
1567 
1568 /*
1569  * As update_and_free_page() can be called under any context, so we cannot
1570  * use GFP_KERNEL to allocate vmemmap pages. However, we can defer the
1571  * actual freeing in a workqueue to prevent from using GFP_ATOMIC to allocate
1572  * the vmemmap pages.
1573  *
1574  * free_hpage_workfn() locklessly retrieves the linked list of pages to be
1575  * freed and frees them one-by-one. As the page->mapping pointer is going
1576  * to be cleared in free_hpage_workfn() anyway, it is reused as the llist_node
1577  * structure of a lockless linked list of huge pages to be freed.
1578  */
1579 static LLIST_HEAD(hpage_freelist);
1580 
1581 static void free_hpage_workfn(struct work_struct *work)
1582 {
1583         struct llist_node *node;
1584 
1585         node = llist_del_all(&hpage_freelist);
1586 
1587         while (node) {
1588                 struct page *page;
1589                 struct hstate *h;
1590 
1591                 page = container_of((struct address_space **)node,
1592                                      struct page, mapping);
1593                 node = node->next;
1594                 page->mapping = NULL;
1595                 /*
1596                  * The VM_BUG_ON_PAGE(!PageHuge(page), page) in page_hstate()
1597                  * is going to trigger because a previous call to
1598                  * remove_hugetlb_page() will set_compound_page_dtor(page,
1599                  * NULL_COMPOUND_DTOR), so do not use page_hstate() directly.
1600                  */
1601                 h = size_to_hstate(page_size(page));
1602 
1603                 __update_and_free_page(h, page);
1604 
1605                 cond_resched();
1606         }
1607 }
1608 static DECLARE_WORK(free_hpage_work, free_hpage_workfn);
1609 
1610 static inline void flush_free_hpage_work(struct hstate *h)
1611 {
1612         if (free_vmemmap_pages_per_hpage(h))
1613                 flush_work(&free_hpage_work);
1614 }
1615 
1616 static void update_and_free_page(struct hstate *h, struct page *page,
1617                                  bool atomic)
1618 {
1619         if (!HPageVmemmapOptimized(page) || !atomic) {
1620                 __update_and_free_page(h, page);
1621                 return;
1622         }
1623 
1624         /*
1625          * Defer freeing to avoid using GFP_ATOMIC to allocate vmemmap pages.
1626          *
1627          * Only call schedule_work() if hpage_freelist is previously
1628          * empty. Otherwise, schedule_work() had been called but the workfn
1629          * hasn't retrieved the list yet.
1630          */
1631         if (llist_add((struct llist_node *)&page->mapping, &hpage_freelist))
1632                 schedule_work(&free_hpage_work);
1633 }
1634 
1635 static void update_and_free_pages_bulk(struct hstate *h, struct list_head *list)
1636 {
1637         struct page *page, *t_page;
1638 
1639         list_for_each_entry_safe(page, t_page, list, lru) {
1640                 update_and_free_page(h, page, false);
1641                 cond_resched();
1642         }
1643 }
1644 
1645 struct hstate *size_to_hstate(unsigned long size)
1646 {
1647         struct hstate *h;
1648 
1649         for_each_hstate(h) {
1650                 if (huge_page_size(h) == size)
1651                         return h;
1652         }
1653         return NULL;
1654 }
1655 
1656 void free_huge_page(struct page *page)
1657 {
1658         /*
1659          * Can't pass hstate in here because it is called from the
1660          * compound page destructor.
1661          */
1662         struct hstate *h = page_hstate(page);
1663         int nid = page_to_nid(page);
1664         struct hugepage_subpool *spool = hugetlb_page_subpool(page);
1665         bool restore_reserve;
1666         unsigned long flags;
1667 
1668         VM_BUG_ON_PAGE(page_count(page), page);
1669         VM_BUG_ON_PAGE(page_mapcount(page), page);
1670 
1671         hugetlb_set_page_subpool(page, NULL);
1672         page->mapping = NULL;
1673         restore_reserve = HPageRestoreReserve(page);
1674         ClearHPageRestoreReserve(page);
1675 
1676         /*
1677          * If HPageRestoreReserve was set on page, page allocation consumed a
1678          * reservation.  If the page was associated with a subpool, there
1679          * would have been a page reserved in the subpool before allocation
1680          * via hugepage_subpool_get_pages().  Since we are 'restoring' the
1681          * reservation, do not call hugepage_subpool_put_pages() as this will
1682          * remove the reserved page from the subpool.
1683          */
1684         if (!restore_reserve) {
1685                 /*
1686                  * A return code of zero implies that the subpool will be
1687                  * under its minimum size if the reservation is not restored
1688                  * after page is free.  Therefore, force restore_reserve
1689                  * operation.
1690                  */
1691                 if (hugepage_subpool_put_pages(spool, 1) == 0)
1692                         restore_reserve = true;
1693         }
1694 
1695         spin_lock_irqsave(&hugetlb_lock, flags);
1696         ClearHPageMigratable(page);
1697         hugetlb_cgroup_uncharge_page(hstate_index(h),
1698                                      pages_per_huge_page(h), page);
1699         hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h),
1700                                           pages_per_huge_page(h), page);
1701         if (restore_reserve)
1702                 h->resv_huge_pages++;
1703 
1704         if (HPageTemporary(page)) {
1705                 remove_hugetlb_page(h, page, false);
1706                 spin_unlock_irqrestore(&hugetlb_lock, flags);
1707                 update_and_free_page(h, page, true);
1708         } else if (h->surplus_huge_pages_node[nid]) {
1709                 /* remove the page from active list */
1710                 remove_hugetlb_page(h, page, true);
1711                 spin_unlock_irqrestore(&hugetlb_lock, flags);
1712                 update_and_free_page(h, page, true);
1713         } else {
1714                 arch_clear_hugepage_flags(page);
1715                 enqueue_huge_page(h, page);
1716                 spin_unlock_irqrestore(&hugetlb_lock, flags);
1717         }
1718 }
1719 
1720 /*
1721  * Must be called with the hugetlb lock held
1722  */
1723 static void __prep_account_new_huge_page(struct hstate *h, int nid)
1724 {
1725         lockdep_assert_held(&hugetlb_lock);
1726         h->nr_huge_pages++;
1727         h->nr_huge_pages_node[nid]++;
1728 }
1729 
1730 static void __prep_new_huge_page(struct hstate *h, struct page *page)
1731 {
1732         free_huge_page_vmemmap(h, page);
1733         INIT_LIST_HEAD(&page->lru);
1734         set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
1735         hugetlb_set_page_subpool(page, NULL);
1736         set_hugetlb_cgroup(page, NULL);
1737         set_hugetlb_cgroup_rsvd(page, NULL);
1738 }
1739 
1740 static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
1741 {
1742         __prep_new_huge_page(h, page);
1743         spin_lock_irq(&hugetlb_lock);
1744         __prep_account_new_huge_page(h, nid);
1745         spin_unlock_irq(&hugetlb_lock);
1746 }
1747 
1748 static bool __prep_compound_gigantic_page(struct page *page, unsigned int order,
1749                                                                 bool demote)
1750 {
1751         int i, j;
1752         int nr_pages = 1 << order;
1753         struct page *p = page + 1;
1754 
1755         /* we rely on prep_new_huge_page to set the destructor */
1756         set_compound_order(page, order);
1757         __ClearPageReserved(page);
1758         __SetPageHead(page);
1759         for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
1760                 /*
1761                  * For gigantic hugepages allocated through bootmem at
1762                  * boot, it's safer to be consistent with the not-gigantic
1763                  * hugepages and clear the PG_reserved bit from all tail pages
1764                  * too.  Otherwise drivers using get_user_pages() to access tail
1765                  * pages may get the reference counting wrong if they see
1766                  * PG_reserved set on a tail page (despite the head page not
1767                  * having PG_reserved set).  Enforcing this consistency between
1768                  * head and tail pages allows drivers to optimize away a check
1769                  * on the head page when they need know if put_page() is needed
1770                  * after get_user_pages().
1771                  */
1772                 __ClearPageReserved(p);
1773                 /*
1774                  * Subtle and very unlikely
1775                  *
1776                  * Gigantic 'page allocators' such as memblock or cma will
1777                  * return a set of pages with each page ref counted.  We need
1778                  * to turn this set of pages into a compound page with tail
1779                  * page ref counts set to zero.  Code such as speculative page
1780                  * cache adding could take a ref on a 'to be' tail page.
1781                  * We need to respect any increased ref count, and only set
1782                  * the ref count to zero if count is currently 1.  If count
1783                  * is not 1, we return an error.  An error return indicates
1784                  * the set of pages can not be converted to a gigantic page.
1785                  * The caller who allocated the pages should then discard the
1786                  * pages using the appropriate free interface.
1787                  *
1788                  * In the case of demote, the ref count will be zero.
1789                  */
1790                 if (!demote) {
1791                         if (!page_ref_freeze(p, 1)) {
1792                                 pr_warn("HugeTLB page can not be used due to unexpected inflated ref count\n");
1793                                 goto out_error;
1794                         }
1795                 } else {
1796                         VM_BUG_ON_PAGE(page_count(p), p);
1797                 }
1798                 set_compound_head(p, page);
1799         }
1800         atomic_set(compound_mapcount_ptr(page), -1);
1801         atomic_set(compound_pincount_ptr(page), 0);
1802         return true;
1803 
1804 out_error:
1805         /* undo tail page modifications made above */
1806         p = page + 1;
1807         for (j = 1; j < i; j++, p = mem_map_next(p, page, j)) {
1808                 clear_compound_head(p);
1809                 set_page_refcounted(p);
1810         }
1811         /* need to clear PG_reserved on remaining tail pages  */
1812         for (; j < nr_pages; j++, p = mem_map_next(p, page, j))
1813                 __ClearPageReserved(p);
1814         set_compound_order(page, 0);
1815         page[1].compound_nr = 0;
1816         __ClearPageHead(page);
1817         return false;
1818 }
1819 
1820 static bool prep_compound_gigantic_page(struct page *page, unsigned int order)
1821 {
1822         return __prep_compound_gigantic_page(page, order, false);
1823 }
1824 
1825 static bool prep_compound_gigantic_page_for_demote(struct page *page,
1826                                                         unsigned int order)
1827 {
1828         return __prep_compound_gigantic_page(page, order, true);
1829 }
1830 
1831 /*
1832  * PageHuge() only returns true for hugetlbfs pages, but not for normal or
1833  * transparent huge pages.  See the PageTransHuge() documentation for more
1834  * details.
1835  */
1836 int PageHuge(struct page *page)
1837 {
1838         if (!PageCompound(page))
1839                 return 0;
1840 
1841         page = compound_head(page);
1842         return page[1].compound_dtor == HUGETLB_PAGE_DTOR;
1843 }
1844 EXPORT_SYMBOL_GPL(PageHuge);
1845 
1846 /*
1847  * PageHeadHuge() only returns true for hugetlbfs head page, but not for
1848  * normal or transparent huge pages.
1849  */
1850 int PageHeadHuge(struct page *page_head)
1851 {
1852         if (!PageHead(page_head))
1853                 return 0;
1854 
1855         return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR;
1856 }
1857 
1858 /*
1859  * Find and lock address space (mapping) in write mode.
1860  *
1861  * Upon entry, the page is locked which means that page_mapping() is
1862  * stable.  Due to locking order, we can only trylock_write.  If we can
1863  * not get the lock, simply return NULL to caller.
1864  */
1865 struct address_space *hugetlb_page_mapping_lock_write(struct page *hpage)
1866 {
1867         struct address_space *mapping = page_mapping(hpage);
1868 
1869         if (!mapping)
1870                 return mapping;
1871 
1872         if (i_mmap_trylock_write(mapping))
1873                 return mapping;
1874 
1875         return NULL;
1876 }
1877 
1878 pgoff_t hugetlb_basepage_index(struct page *page)
1879 {
1880         struct page *page_head = compound_head(page);
1881         pgoff_t index = page_index(page_head);
1882         unsigned long compound_idx;
1883 
1884         if (compound_order(page_head) >= MAX_ORDER)
1885                 compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
1886         else
1887                 compound_idx = page - page_head;
1888 
1889         return (index << compound_order(page_head)) + compound_idx;
1890 }
1891 
1892 static struct page *alloc_buddy_huge_page(struct hstate *h,
1893                 gfp_t gfp_mask, int nid, nodemask_t *nmask,
1894                 nodemask_t *node_alloc_noretry)
1895 {
1896         int order = huge_page_order(h);
1897         struct page *page;
1898         bool alloc_try_hard = true;
1899 
1900         /*
1901          * By default we always try hard to allocate the page with
1902          * __GFP_RETRY_MAYFAIL flag.  However, if we are allocating pages in
1903          * a loop (to adjust global huge page counts) and previous allocation
1904          * failed, do not continue to try hard on the same node.  Use the
1905          * node_alloc_noretry bitmap to manage this state information.
1906          */
1907         if (node_alloc_noretry && node_isset(nid, *node_alloc_noretry))
1908                 alloc_try_hard = false;
1909         gfp_mask |= __GFP_COMP|__GFP_NOWARN;
1910         if (alloc_try_hard)
1911                 gfp_mask |= __GFP_RETRY_MAYFAIL;
1912         if (nid == NUMA_NO_NODE)
1913                 nid = numa_mem_id();
1914         page = __alloc_pages(gfp_mask, order, nid, nmask);
1915         if (page)
1916                 __count_vm_event(HTLB_BUDDY_PGALLOC);
1917         else
1918                 __count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
1919 
1920         /*
1921          * If we did not specify __GFP_RETRY_MAYFAIL, but still got a page this
1922          * indicates an overall state change.  Clear bit so that we resume
1923          * normal 'try hard' allocations.
1924          */
1925         if (node_alloc_noretry && page && !alloc_try_hard)
1926                 node_clear(nid, *node_alloc_noretry);
1927 
1928         /*
1929          * If we tried hard to get a page but failed, set bit so that
1930          * subsequent attempts will not try as hard until there is an
1931          * overall state change.
1932          */
1933         if (node_alloc_noretry && !page && alloc_try_hard)
1934                 node_set(nid, *node_alloc_noretry);
1935 
1936         return page;
1937 }
1938 
1939 /*
1940  * Common helper to allocate a fresh hugetlb page. All specific allocators
1941  * should use this function to get new hugetlb pages
1942  */
1943 static struct page *alloc_fresh_huge_page(struct hstate *h,
1944                 gfp_t gfp_mask, int nid, nodemask_t *nmask,
1945                 nodemask_t *node_alloc_noretry)
1946 {
1947         struct page *page;
1948         bool retry = false;
1949 
1950 retry:
1951         if (hstate_is_gigantic(h))
1952                 page = alloc_gigantic_page(h, gfp_mask, nid, nmask);
1953         else
1954                 page = alloc_buddy_huge_page(h, gfp_mask,
1955                                 nid, nmask, node_alloc_noretry);
1956         if (!page)
1957                 return NULL;
1958 
1959         if (hstate_is_gigantic(h)) {
1960                 if (!prep_compound_gigantic_page(page, huge_page_order(h))) {
1961                         /*
1962                          * Rare failure to convert pages to compound page.
1963                          * Free pages and try again - ONCE!
1964                          */
1965                         free_gigantic_page(page, huge_page_order(h));
1966                         if (!retry) {
1967                                 retry = true;
1968                                 goto retry;
1969                         }
1970                         return NULL;
1971                 }
1972         }
1973         prep_new_huge_page(h, page, page_to_nid(page));
1974 
1975         return page;
1976 }
1977 
1978 /*
1979  * Allocates a fresh page to the hugetlb allocator pool in the node interleaved
1980  * manner.
1981  */
1982 static int alloc_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
1983                                 nodemask_t *node_alloc_noretry)
1984 {
1985         struct page *page;
1986         int nr_nodes, node;
1987         gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
1988 
1989         for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
1990                 page = alloc_fresh_huge_page(h, gfp_mask, node, nodes_allowed,
1991                                                 node_alloc_noretry);
1992                 if (page)
1993                         break;
1994         }
1995 
1996         if (!page)
1997                 return 0;
1998 
1999         put_page(page); /* free it into the hugepage allocator */
2000 
2001         return 1;
2002 }
2003 
2004 /*
2005  * Remove huge page from pool from next node to free.  Attempt to keep
2006  * persistent huge pages more or less balanced over allowed nodes.
2007  * This routine only 'removes' the hugetlb page.  The caller must make
2008  * an additional call to free the page to low level allocators.
2009  * Called with hugetlb_lock locked.
2010  */
2011 static struct page *remove_pool_huge_page(struct hstate *h,
2012                                                 nodemask_t *nodes_allowed,
2013                                                  bool acct_surplus)
2014 {
2015         int nr_nodes, node;
2016         struct page *page = NULL;
2017 
2018         lockdep_assert_held(&hugetlb_lock);
2019         for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
2020                 /*
2021                  * If we're returning unused surplus pages, only examine
2022                  * nodes with surplus pages.
2023                  */
2024                 if ((!acct_surplus || h->surplus_huge_pages_node[node]) &&
2025                     !list_empty(&h->hugepage_freelists[node])) {
2026                         page = list_entry(h->hugepage_freelists[node].next,
2027                                           struct page, lru);
2028                         remove_hugetlb_page(h, page, acct_surplus);
2029                         break;
2030                 }
2031         }
2032 
2033         return page;
2034 }
2035 
2036 /*
2037  * Dissolve a given free hugepage into free buddy pages. This function does
2038  * nothing for in-use hugepages and non-hugepages.
2039  * This function returns values like below:
2040  *
2041  *  -ENOMEM: failed to allocate vmemmap pages to free the freed hugepages
2042  *           when the system is under memory pressure and the feature of
2043  *           freeing unused vmemmap pages associated with each hugetlb page
2044  *           is enabled.
2045  *  -EBUSY:  failed to dissolved free hugepages or the hugepage is in-use
2046  *           (allocated or reserved.)
2047  *       0:  successfully dissolved free hugepages or the page is not a
2048  *           hugepage (considered as already dissolved)
2049  */
2050 int dissolve_free_huge_page(struct page *page)
2051 {
2052         int rc = -EBUSY;
2053 
2054 retry:
2055         /* Not to disrupt normal path by vainly holding hugetlb_lock */
2056         if (!PageHuge(page))
2057                 return 0;
2058 
2059         spin_lock_irq(&hugetlb_lock);
2060         if (!PageHuge(page)) {
2061                 rc = 0;
2062                 goto out;
2063         }
2064 
2065         if (!page_count(page)) {
2066                 struct page *head = compound_head(page);
2067                 struct hstate *h = page_hstate(head);
2068                 if (h->free_huge_pages - h->resv_huge_pages == 0)
2069                         goto out;
2070 
2071                 /*
2072                  * We should make sure that the page is already on the free list
2073                  * when it is dissolved.
2074                  */
2075                 if (unlikely(!HPageFreed(head))) {
2076                         spin_unlock_irq(&hugetlb_lock);
2077                         cond_resched();
2078 
2079                         /*
2080                          * Theoretically, we should return -EBUSY when we
2081                          * encounter this race. In fact, we have a chance
2082                          * to successfully dissolve the page if we do a
2083                          * retry. Because the race window is quite small.
2084                          * If we seize this opportunity, it is an optimization
2085                          * for increasing the success rate of dissolving page.
2086                          */
2087                         goto retry;
2088                 }
2089 
2090                 remove_hugetlb_page(h, head, false);
2091                 h->max_huge_pages--;
2092                 spin_unlock_irq(&hugetlb_lock);
2093 
2094                 /*
2095                  * Normally update_and_free_page will allocate required vmemmmap
2096                  * before freeing the page.  update_and_free_page will fail to
2097                  * free the page if it can not allocate required vmemmap.  We
2098                  * need to adjust max_huge_pages if the page is not freed.
2099                  * Attempt to allocate vmemmmap here so that we can take
2100                  * appropriate action on failure.
2101                  */
2102                 rc = alloc_huge_page_vmemmap(h, head);
2103                 if (!rc) {
2104                         /*
2105                          * Move PageHWPoison flag from head page to the raw
2106                          * error page, which makes any subpages rather than
2107                          * the error page reusable.
2108                          */
2109                         if (PageHWPoison(head) && page != head) {
2110                                 SetPageHWPoison(page);
2111                                 ClearPageHWPoison(head);
2112                         }
2113                         update_and_free_page(h, head, false);
2114                 } else {
2115                         spin_lock_irq(&hugetlb_lock);
2116                         add_hugetlb_page(h, head, false);
2117                         h->max_huge_pages++;
2118                         spin_unlock_irq(&hugetlb_lock);
2119                 }
2120 
2121                 return rc;
2122         }
2123 out:
2124         spin_unlock_irq(&hugetlb_lock);
2125         return rc;
2126 }
2127 
2128 /*
2129  * Dissolve free hugepages in a given pfn range. Used by memory hotplug to
2130  * make specified memory blocks removable from the system.
2131  * Note that this will dissolve a free gigantic hugepage completely, if any
2132  * part of it lies within the given range.
2133  * Also note that if dissolve_free_huge_page() returns with an error, all
2134  * free hugepages that were dissolved before that error are lost.
2135  */
2136 int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
2137 {
2138         unsigned long pfn;
2139         struct page *page;
2140         int rc = 0;
2141 
2142         if (!hugepages_supported())
2143                 return rc;
2144 
2145         for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order) {
2146                 page = pfn_to_page(pfn);
2147                 rc = dissolve_free_huge_page(page);
2148                 if (rc)
2149                         break;
2150         }
2151 
2152         return rc;
2153 }
2154 
2155 /*
2156  * Allocates a fresh surplus page from the page allocator.
2157  */
2158 static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
2159                 int nid, nodemask_t *nmask, bool zero_ref)
2160 {
2161         struct page *page = NULL;
2162         bool retry = false;
2163 
2164         if (hstate_is_gigantic(h))
2165                 return NULL;
2166 
2167         spin_lock_irq(&hugetlb_lock);
2168         if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages)
2169                 goto out_unlock;
2170         spin_unlock_irq(&hugetlb_lock);
2171 
2172 retry:
2173         page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask, NULL);
2174         if (!page)
2175                 return NULL;
2176 
2177         spin_lock_irq(&hugetlb_lock);
2178         /*
2179          * We could have raced with the pool size change.
2180          * Double check that and simply deallocate the new page
2181          * if we would end up overcommiting the surpluses. Abuse
2182          * temporary page to workaround the nasty free_huge_page
2183          * codeflow
2184          */
2185         if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
2186                 SetHPageTemporary(page);
2187                 spin_unlock_irq(&hugetlb_lock);
2188                 put_page(page);
2189                 return NULL;
2190         }
2191 
2192         if (zero_ref) {
2193                 /*
2194                  * Caller requires a page with zero ref count.
2195                  * We will drop ref count here.  If someone else is holding
2196                  * a ref, the page will be freed when they drop it.  Abuse
2197                  * temporary page flag to accomplish this.
2198                  */
2199                 SetHPageTemporary(page);
2200                 if (!put_page_testzero(page)) {
2201                         /*
2202                          * Unexpected inflated ref count on freshly allocated
2203                          * huge.  Retry once.
2204                          */
2205                         pr_info("HugeTLB unexpected inflated ref count on freshly allocated page\n");
2206                         spin_unlock_irq(&hugetlb_lock);
2207                         if (retry)
2208                                 return NULL;
2209 
2210                         retry = true;
2211                         goto retry;
2212                 }
2213                 ClearHPageTemporary(page);
2214         }
2215 
2216         h->surplus_huge_pages++;
2217         h->surplus_huge_pages_node[page_to_nid(page)]++;
2218 
2219 out_unlock:
2220         spin_unlock_irq(&hugetlb_lock);
2221 
2222         return page;
2223 }
2224 
2225 static struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
2226                                      int nid, nodemask_t *nmask)
2227 {
2228         struct page *page;
2229 
2230         if (hstate_is_gigantic(h))
2231                 return NULL;
2232 
2233         page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask, NULL);
2234         if (!page)
2235                 return NULL;
2236 
2237         /*
2238          * We do not account these pages as surplus because they are only
2239          * temporary and will be released properly on the last reference
2240          */
2241         SetHPageTemporary(page);
2242 
2243         return page;
2244 }
2245 
2246 /*
2247  * Use the VMA's mpolicy to allocate a huge page from the buddy.
2248  */
2249 static
2250 struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
2251                 struct vm_area_struct *vma, unsigned long addr)
2252 {
2253         struct page *page = NULL;
2254         struct mempolicy *mpol;
2255         gfp_t gfp_mask = htlb_alloc_mask(h);
2256         int nid;
2257         nodemask_t *nodemask;
2258 
2259         nid = huge_node(vma, addr, gfp_mask, &mpol, &nodemask);
2260         if (mpol_is_preferred_many(mpol)) {
2261                 gfp_t gfp = gfp_mask | __GFP_NOWARN;
2262 
2263                 gfp &=  ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL);
2264                 page = alloc_surplus_huge_page(h, gfp, nid, nodemask, false);
2265 
2266                 /* Fallback to all nodes if page==NULL */
2267                 nodemask = NULL;
2268         }
2269 
2270         if (!page)
2271                 page = alloc_surplus_huge_page(h, gfp_mask, nid, nodemask, false);
2272         mpol_cond_put(mpol);
2273         return page;
2274 }
2275 
2276 /* page migration callback function */
2277 struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
2278                 nodemask_t *nmask, gfp_t gfp_mask)
2279 {
2280         spin_lock_irq(&hugetlb_lock);
2281         if (h->free_huge_pages - h->resv_huge_pages > 0) {
2282                 struct page *page;
2283 
2284                 page = dequeue_huge_page_nodemask(h, gfp_mask, preferred_nid, nmask);
2285                 if (page) {
2286                         spin_unlock_irq(&hugetlb_lock);
2287                         return page;
2288                 }
2289         }
2290         spin_unlock_irq(&hugetlb_lock);
2291 
2292         return alloc_migrate_huge_page(h, gfp_mask, preferred_nid, nmask);
2293 }
2294 
2295 /* mempolicy aware migration callback */
2296 struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
2297                 unsigned long address)
2298 {
2299         struct mempolicy *mpol;
2300         nodemask_t *nodemask;
2301         struct page *page;
2302         gfp_t gfp_mask;
2303         int node;
2304 
2305         gfp_mask = htlb_alloc_mask(h);
2306         node = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
2307         page = alloc_huge_page_nodemask(h, node, nodemask, gfp_mask);
2308         mpol_cond_put(mpol);
2309 
2310         return page;
2311 }
2312 
2313 /*
2314  * Increase the hugetlb pool such that it can accommodate a reservation
2315  * of size 'delta'.
2316  */
2317 static int gather_surplus_pages(struct hstate *h, long delta)
2318         __must_hold(&hugetlb_lock)
2319 {
2320         struct list_head surplus_list;
2321         struct page *page, *tmp;
2322         int ret;
2323         long i;
2324         long needed, allocated;
2325         bool alloc_ok = true;
2326 
2327         lockdep_assert_held(&hugetlb_lock);
2328         needed = (h->resv_huge_pages + delta) - h->free_huge_pages;
2329         if (needed <= 0) {
2330                 h->resv_huge_pages += delta;
2331                 return 0;
2332         }
2333 
2334         allocated = 0;
2335         INIT_LIST_HEAD(&surplus_list);
2336 
2337         ret = -ENOMEM;
2338 retry:
2339         spin_unlock_irq(&hugetlb_lock);
2340         for (i = 0; i < needed; i++) {
2341                 page = alloc_surplus_huge_page(h, htlb_alloc_mask(h),
2342                                 NUMA_NO_NODE, NULL, true);
2343                 if (!page) {
2344                         alloc_ok = false;
2345                         break;
2346                 }
2347                 list_add(&page->lru, &surplus_list);
2348                 cond_resched();
2349         }
2350         allocated += i;
2351 
2352         /*
2353          * After retaking hugetlb_lock, we need to recalculate 'needed'
2354          * because either resv_huge_pages or free_huge_pages may have changed.
2355          */
2356         spin_lock_irq(&hugetlb_lock);
2357         needed = (h->resv_huge_pages + delta) -
2358                         (h->free_huge_pages + allocated);
2359         if (needed > 0) {
2360                 if (alloc_ok)
2361                         goto retry;
2362                 /*
2363                  * We were not able to allocate enough pages to
2364                  * satisfy the entire reservation so we free what
2365                  * we've allocated so far.
2366                  */
2367                 goto free;
2368         }
2369         /*
2370          * The surplus_list now contains _at_least_ the number of extra pages
2371          * needed to accommodate the reservation.  Add the appropriate number
2372          * of pages to the hugetlb pool and free the extras back to the buddy
2373          * allocator.  Commit the entire reservation here to prevent another
2374          * process from stealing the pages as they are added to the pool but
2375          * before they are reserved.
2376          */
2377         needed += allocated;
2378         h->resv_huge_pages += delta;
2379         ret = 0;
2380 
2381         /* Free the needed pages to the hugetlb pool */
2382         list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
2383                 if ((--needed) < 0)
2384                         break;
2385                 /* Add the page to the hugetlb allocator */
2386                 enqueue_huge_page(h, page);
2387         }
2388 free:
2389         spin_unlock_irq(&hugetlb_lock);
2390 
2391         /*
2392          * Free unnecessary surplus pages to the buddy allocator.
2393          * Pages have no ref count, call free_huge_page directly.
2394          */
2395         list_for_each_entry_safe(page, tmp, &surplus_list, lru)
2396                 free_huge_page(page);
2397         spin_lock_irq(&hugetlb_lock);
2398 
2399         return ret;
2400 }
2401 
2402 /*
2403  * This routine has two main purposes:
2404  * 1) Decrement the reservation count (resv_huge_pages) by the value passed
2405  *    in unused_resv_pages.  This corresponds to the prior adjustments made
2406  *    to the associated reservation map.
2407  * 2) Free any unused surplus pages that may have been allocated to satisfy
2408  *    the reservation.  As many as unused_resv_pages may be freed.
2409  */
2410 static void return_unused_surplus_pages(struct hstate *h,
2411                                         unsigned long unused_resv_pages)
2412 {
2413         unsigned long nr_pages;
2414         struct page *page;
2415         LIST_HEAD(page_list);
2416 
2417         lockdep_assert_held(&hugetlb_lock);
2418         /* Uncommit the reservation */
2419         h->resv_huge_pages -= unused_resv_pages;
2420 
2421         /* Cannot return gigantic pages currently */
2422         if (hstate_is_gigantic(h))
2423                 goto out;
2424 
2425         /*
2426          * Part (or even all) of the reservation could have been backed
2427          * by pre-allocated pages. Only free surplus pages.
2428          */
2429         nr_pages = min(unused_resv_pages, h->surplus_huge_pages);
2430 
2431         /*
2432          * We want to release as many surplus pages as possible, spread
2433          * evenly across all nodes with memory. Iterate across these nodes
2434          * until we can no longer free unreserved surplus pages. This occurs
2435          * when the nodes with surplus pages have no free pages.
2436          * remove_pool_huge_page() will balance the freed pages across the
2437          * on-line nodes with memory and will handle the hstate accounting.
2438          */
2439         while (nr_pages--) {
2440                 page = remove_pool_huge_page(h, &node_states[N_MEMORY], 1);
2441                 if (!page)
2442                         goto out;
2443 
2444                 list_add(&page->lru, &page_list);
2445         }
2446 
2447 out:
2448         spin_unlock_irq(&hugetlb_lock);
2449         update_and_free_pages_bulk(h, &page_list);
2450         spin_lock_irq(&hugetlb_lock);
2451 }
2452 
2453 
2454 /*
2455  * vma_needs_reservation, vma_commit_reservation and vma_end_reservation
2456  * are used by the huge page allocation routines to manage reservations.
2457  *
2458  * vma_needs_reservation is called to determine if the huge page at addr
2459  * within the vma has an associated reservation.  If a reservation is
2460  * needed, the value 1 is returned.  The caller is then responsible for
2461  * managing the global reservation and subpool usage counts.  After
2462  * the huge page has been allocated, vma_commit_reservation is called
2463  * to add the page to the reservation map.  If the page allocation fails,
2464  * the reservation must be ended instead of committed.  vma_end_reservation
2465  * is called in such cases.
2466  *
2467  * In the normal case, vma_commit_reservation returns the same value
2468  * as the preceding vma_needs_reservation call.  The only time this
2469  * is not the case is if a reserve map was changed between calls.  It
2470  * is the responsibility of the caller to notice the difference and
2471  * take appropriate action.
2472  *
2473  * vma_add_reservation is used in error paths where a reservation must
2474  * be restored when a newly allocated huge page must be freed.  It is
2475  * to be called after calling vma_needs_reservation to determine if a
2476  * reservation exists.
2477  *
2478  * vma_del_reservation is used in error paths where an entry in the reserve
2479  * map was created during huge page allocation and must be removed.  It is to
2480  * be called after calling vma_needs_reservation to determine if a reservation
2481  * exists.
2482  */
2483 enum vma_resv_mode {
2484         VMA_NEEDS_RESV,
2485         VMA_COMMIT_RESV,
2486         VMA_END_RESV,
2487         VMA_ADD_RESV,
2488         VMA_DEL_RESV,
2489 };
2490 static long __vma_reservation_common(struct hstate *h,
2491                                 struct vm_area_struct *vma, unsigned long addr,
2492                                 enum vma_resv_mode mode)
2493 {
2494         struct resv_map *resv;
2495         pgoff_t idx;
2496         long ret;
2497         long dummy_out_regions_needed;
2498 
2499         resv = vma_resv_map(vma);
2500         if (!resv)
2501                 return 1;
2502 
2503         idx = vma_hugecache_offset(h, vma, addr);
2504         switch (mode) {
2505         case VMA_NEEDS_RESV:
2506                 ret = region_chg(resv, idx, idx + 1, &dummy_out_regions_needed);
2507                 /* We assume that vma_reservation_* routines always operate on
2508                  * 1 page, and that adding to resv map a 1 page entry can only
2509                  * ever require 1 region.
2510                  */
2511                 VM_BUG_ON(dummy_out_regions_needed != 1);
2512                 break;
2513         case VMA_COMMIT_RESV:
2514                 ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
2515                 /* region_add calls of range 1 should never fail. */
2516                 VM_BUG_ON(ret < 0);
2517                 break;
2518         case VMA_END_RESV:
2519                 region_abort(resv, idx, idx + 1, 1);
2520                 ret = 0;
2521                 break;
2522         case VMA_ADD_RESV:
2523                 if (vma->vm_flags & VM_MAYSHARE) {
2524                         ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
2525                         /* region_add calls of range 1 should never fail. */
2526                         VM_BUG_ON(ret < 0);
2527                 } else {
2528                         region_abort(resv, idx, idx + 1, 1);
2529                         ret = region_del(resv, idx, idx + 1);
2530                 }
2531                 break;
2532         case VMA_DEL_RESV:
2533                 if (vma->vm_flags & VM_MAYSHARE) {
2534                         region_abort(resv, idx, idx + 1, 1);
2535                         ret = region_del(resv, idx, idx + 1);
2536                 } else {
2537                         ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
2538                         /* region_add calls of range 1 should never fail. */
2539                         VM_BUG_ON(ret < 0);
2540                 }
2541                 break;
2542         default:
2543                 BUG();
2544         }
2545 
2546         if (vma->vm_flags & VM_MAYSHARE || mode == VMA_DEL_RESV)
2547                 return ret;
2548         /*
2549          * We know private mapping must have HPAGE_RESV_OWNER set.
2550          *
2551          * In most cases, reserves always exist for private mappings.
2552          * However, a file associated with mapping could have been
2553          * hole punched or truncated after reserves were consumed.
2554          * As subsequent fault on such a range will not use reserves.
2555          * Subtle - The reserve map for private mappings has the
2556          * opposite meaning than that of shared mappings.  If NO
2557          * entry is in the reserve map, it means a reservation exists.
2558          * If an entry exists in the reserve map, it means the
2559          * reservation has already been consumed.  As a result, the
2560          * return value of this routine is the opposite of the
2561          * value returned from reserve map manipulation routines above.
2562          */
2563         if (ret > 0)
2564                 return 0;
2565         if (ret == 0)
2566                 return 1;
2567         return ret;
2568 }
2569 
2570 static long vma_needs_reservation(struct hstate *h,
2571                         struct vm_area_struct *vma, unsigned long addr)
2572 {
2573         return __vma_reservation_common(h, vma, addr, VMA_NEEDS_RESV);
2574 }
2575 
2576 static long vma_commit_reservation(struct hstate *h,
2577                         struct vm_area_struct *vma, unsigned long addr)
2578 {
2579         return __vma_reservation_common(h, vma, addr, VMA_COMMIT_RESV);
2580 }
2581 
2582 static void vma_end_reservation(struct hstate *h,
2583                         struct vm_area_struct *vma, unsigned long addr)
2584 {
2585         (void)__vma_reservation_common(h, vma, addr, VMA_END_RESV);
2586 }
2587 
2588 static long vma_add_reservation(struct hstate *h,
2589                         struct vm_area_struct *vma, unsigned long addr)
2590 {
2591         return __vma_reservation_common(h, vma, addr, VMA_ADD_RESV);
2592 }
2593 
2594 static long vma_del_reservation(struct hstate *h,
2595                         struct vm_area_struct *vma, unsigned long addr)
2596 {
2597         return __vma_reservation_common(h, vma, addr, VMA_DEL_RESV);
2598 }
2599 
2600 /*
2601  * This routine is called to restore reservation information on error paths.
2602  * It should ONLY be called for pages allocated via alloc_huge_page(), and
2603  * the hugetlb mutex should remain held when calling this routine.
2604  *
2605  * It handles two specific cases:
2606  * 1) A reservation was in place and the page consumed the reservation.
2607  *    HPageRestoreReserve is set in the page.
2608  * 2) No reservation was in place for the page, so HPageRestoreReserve is
2609  *    not set.  However, alloc_huge_page always updates the reserve map.
2610  *
2611  * In case 1, free_huge_page later in the error path will increment the
2612  * global reserve count.  But, free_huge_page does not have enough context
2613  * to adjust the reservation map.  This case deals primarily with private
2614  * mappings.  Adjust the reserve map here to be consistent with global
2615  * reserve count adjustments to be made by free_huge_page.  Make sure the
2616  * reserve map indicates there is a reservation present.
2617  *
2618  * In case 2, simply undo reserve map modifications done by alloc_huge_page.
2619  */
2620 void restore_reserve_on_error(struct hstate *h, struct vm_area_struct *vma,
2621                         unsigned long address, struct page *page)
2622 {
2623         long rc = vma_needs_reservation(h, vma, address);
2624 
2625         if (HPageRestoreReserve(page)) {
2626                 if (unlikely(rc < 0))
2627                         /*
2628                          * Rare out of memory condition in reserve map
2629                          * manipulation.  Clear HPageRestoreReserve so that
2630                          * global reserve count will not be incremented
2631                          * by free_huge_page.  This will make it appear
2632                          * as though the reservation for this page was
2633                          * consumed.  This may prevent the task from
2634                          * faulting in the page at a later time.  This
2635                          * is better than inconsistent global huge page
2636                          * accounting of reserve counts.
2637                          */
2638                         ClearHPageRestoreReserve(page);
2639                 else if (rc)
2640                         (void)vma_add_reservation(h, vma, address);
2641                 else
2642                         vma_end_reservation(h, vma, address);
2643         } else {
2644                 if (!rc) {
2645                         /*
2646                          * This indicates there is an entry in the reserve map
2647                          * not added by alloc_huge_page.  We know it was added
2648                          * before the alloc_huge_page call, otherwise
2649                          * HPageRestoreReserve would be set on the page.
2650                          * Remove the entry so that a subsequent allocation
2651                          * does not consume a reservation.
2652                          */
2653                         rc = vma_del_reservation(h, vma, address);
2654                         if (rc < 0)
2655                                 /*
2656                                  * VERY rare out of memory condition.  Since
2657                                  * we can not delete the entry, set
2658                                  * HPageRestoreReserve so that the reserve
2659                                  * count will be incremented when the page
2660                                  * is freed.  This reserve will be consumed
2661                                  * on a subsequent allocation.
2662                                  */
2663                                 SetHPageRestoreReserve(page);
2664                 } else if (rc < 0) {
2665                         /*
2666                          * Rare out of memory condition from
2667                          * vma_needs_reservation call.  Memory allocation is
2668                          * only attempted if a new entry is needed.  Therefore,
2669                          * this implies there is not an entry in the
2670                          * reserve map.
2671                          *
2672                          * For shared mappings, no entry in the map indicates
2673                          * no reservation.  We are done.
2674                          */
2675                         if (!(vma->vm_flags & VM_MAYSHARE))
2676                                 /*
2677                                  * For private mappings, no entry indicates
2678                                  * a reservation is present.  Since we can
2679                                  * not add an entry, set SetHPageRestoreReserve
2680                                  * on the page so reserve count will be
2681                                  * incremented when freed.  This reserve will
2682                                  * be consumed on a subsequent allocation.
2683                                  */
2684                                 SetHPageRestoreReserve(page);
2685                 } else
2686                         /*
2687                          * No reservation present, do nothing
2688                          */
2689                          vma_end_reservation(h, vma, address);
2690         }
2691 }
2692 
2693 /*
2694  * alloc_and_dissolve_huge_page - Allocate a new page and dissolve the old one
2695  * @h: struct hstate old page belongs to
2696  * @old_page: Old page to dissolve
2697  * @list: List to isolate the page in case we need to
2698  * Returns 0 on success, otherwise negated error.
2699  */
2700 static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
2701                                         struct list_head *list)
2702 {
2703         gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
2704         int nid = page_to_nid(old_page);
2705         bool alloc_retry = false;
2706         struct page *new_page;
2707         int ret = 0;
2708 
2709         /*
2710          * Before dissolving the page, we need to allocate a new one for the
2711          * pool to remain stable.  Here, we allocate the page and 'prep' it
2712          * by doing everything but actually updating counters and adding to
2713          * the pool.  This simplifies and let us do most of the processing
2714          * under the lock.
2715          */
2716 alloc_retry:
2717         new_page = alloc_buddy_huge_page(h, gfp_mask, nid, NULL, NULL);
2718         if (!new_page)
2719                 return -ENOMEM;
2720         /*
2721          * If all goes well, this page will be directly added to the free
2722          * list in the pool.  For this the ref count needs to be zero.
2723          * Attempt to drop now, and retry once if needed.  It is VERY
2724          * unlikely there is another ref on the page.
2725          *
2726          * If someone else has a reference to the page, it will be freed
2727          * when they drop their ref.  Abuse temporary page flag to accomplish
2728          * this.  Retry once if there is an inflated ref count.
2729          */
2730         SetHPageTemporary(new_page);
2731         if (!put_page_testzero(new_page)) {
2732                 if (alloc_retry)
2733                         return -EBUSY;
2734 
2735                 alloc_retry = true;
2736                 goto alloc_retry;
2737         }
2738         ClearHPageTemporary(new_page);
2739 
2740         __prep_new_huge_page(h, new_page);
2741 
2742 retry:
2743         spin_lock_irq(&hugetlb_lock);
2744         if (!PageHuge(old_page)) {
2745                 /*
2746                  * Freed from under us. Drop new_page too.
2747                  */
2748                 goto free_new;
2749         } else if (page_count(old_page)) {
2750                 /*
2751                  * Someone has grabbed the page, try to isolate it here.
2752                  * Fail with -EBUSY if not possible.
2753                  */
2754                 spin_unlock_irq(&hugetlb_lock);
2755                 if (!isolate_huge_page(old_page, list))
2756                         ret = -EBUSY;
2757                 spin_lock_irq(&hugetlb_lock);
2758                 goto free_new;
2759         } else if (!HPageFreed(old_page)) {
2760                 /*
2761                  * Page's refcount is 0 but it has not been enqueued in the
2762                  * freelist yet. Race window is small, so we can succeed here if
2763                  * we retry.
2764                  */
2765                 spin_unlock_irq(&hugetlb_lock);
2766                 cond_resched();
2767                 goto retry;
2768         } else {
2769                 /*
2770                  * Ok, old_page is still a genuine free hugepage. Remove it from
2771                  * the freelist and decrease the counters. These will be
2772                  * incremented again when calling __prep_account_new_huge_page()
2773                  * and enqueue_huge_page() for new_page. The counters will remain
2774                  * stable since this happens under the lock.
2775                  */
2776                 remove_hugetlb_page(h, old_page, false);
2777 
2778                 /*
2779                  * Ref count on new page is already zero as it was dropped
2780                  * earlier.  It can be directly added to the pool free list.
2781                  */
2782                 __prep_account_new_huge_page(h, nid);
2783                 enqueue_huge_page(h, new_page);
2784 
2785                 /*
2786                  * Pages have been replaced, we can safely free the old one.
2787                  */
2788                 spin_unlock_irq(&hugetlb_lock);
2789                 update_and_free_page(h, old_page, false);
2790         }
2791 
2792         return ret;
2793 
2794 free_new:
2795         spin_unlock_irq(&hugetlb_lock);
2796         /* Page has a zero ref count, but needs a ref to be freed */
2797         set_page_refcounted(new_page);
2798         update_and_free_page(h, new_page, false);
2799 
2800         return ret;
2801 }
2802 
2803 int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
2804 {
2805         struct hstate *h;
2806         struct page *head;
2807         int ret = -EBUSY;
2808 
2809         /*
2810          * The page might have been dissolved from under our feet, so make sure
2811          * to carefully check the state under the lock.
2812          * Return success when racing as if we dissolved the page ourselves.
2813          */
2814         spin_lock_irq(&hugetlb_lock);
2815         if (PageHuge(page)) {
2816                 head = compound_head(page);
2817                 h = page_hstate(head);
2818         } else {
2819                 spin_unlock_irq(&hugetlb_lock);
2820                 return 0;
2821         }
2822         spin_unlock_irq(&hugetlb_lock);
2823 
2824         /*
2825          * Fence off gigantic pages as there is a cyclic dependency between
2826          * alloc_contig_range and them. Return -ENOMEM as this has the effect
2827          * of bailing out right away without further retrying.
2828          */
2829         if (hstate_is_gigantic(h))
2830                 return -ENOMEM;
2831 
2832         if (page_count(head) && isolate_huge_page(head, list))
2833                 ret = 0;
2834         else if (!page_count(head))
2835                 ret = alloc_and_dissolve_huge_page(h, head, list);
2836 
2837         return ret;
2838 }
2839 
2840 struct page *alloc_huge_page(struct vm_area_struct *vma,
2841                                     unsigned long addr, int avoid_reserve)
2842 {
2843         struct hugepage_subpool *spool = subpool_vma(vma);
2844         struct hstate *h = hstate_vma(vma);
2845         struct page *page;
2846         long map_chg, map_commit;
2847         long gbl_chg;
2848         int ret, idx;
2849         struct hugetlb_cgroup *h_cg;
2850         bool deferred_reserve;
2851 
2852         idx = hstate_index(h);
2853         /*
2854          * Examine the region/reserve map to determine if the process
2855          * has a reservation for the page to be allocated.  A return
2856          * code of zero indicates a reservation exists (no change).
2857          */
2858         map_chg = gbl_chg = vma_needs_reservation(h, vma, addr);
2859         if (map_chg < 0)
2860                 return ERR_PTR(-ENOMEM);
2861 
2862         /*
2863          * Processes that did not create the mapping will have no
2864          * reserves as indicated by the region/reserve map. Check
2865          * that the allocation will not exceed the subpool limit.
2866          * Allocations for MAP_NORESERVE mappings also need to be
2867          * checked against any subpool limit.
2868          */
2869         if (map_chg || avoid_reserve) {
2870                 gbl_chg = hugepage_subpool_get_pages(spool, 1);
2871                 if (gbl_chg < 0) {
2872                         vma_end_reservation(h, vma, addr);
2873                         return ERR_PTR(-ENOSPC);
2874                 }
2875 
2876                 /*
2877                  * Even though there was no reservation in the region/reserve
2878                  * map, there could be reservations associated with the
2879                  * subpool that can be used.  This would be indicated if the
2880                  * return value of hugepage_subpool_get_pages() is zero.
2881                  * However, if avoid_reserve is specified we still avoid even
2882                  * the subpool reservations.
2883                  */
2884                 if (avoid_reserve)
2885                         gbl_chg = 1;
2886         }
2887 
2888         /* If this allocation is not consuming a reservation, charge it now.
2889          */
2890         deferred_reserve = map_chg || avoid_reserve;
2891         if (deferred_reserve) {
2892                 ret = hugetlb_cgroup_charge_cgroup_rsvd(
2893                         idx, pages_per_huge_page(h), &h_cg);
2894                 if (ret)
2895                         goto out_subpool_put;
2896         }
2897 
2898         ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
2899         if (ret)
2900                 goto out_uncharge_cgroup_reservation;
2901 
2902         spin_lock_irq(&hugetlb_lock);
2903         /*
2904          * glb_chg is passed to indicate whether or not a page must be taken
2905          * from the global free pool (global change).  gbl_chg == 0 indicates
2906          * a reservation exists for the allocation.
2907          */
2908         page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, gbl_chg);
2909         if (!page) {
2910                 spin_unlock_irq(&hugetlb_lock);
2911                 page = alloc_buddy_huge_page_with_mpol(h, vma, addr);
2912                 if (!page)
2913                         goto out_uncharge_cgroup;
2914                 if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) {
2915                         SetHPageRestoreReserve(page);
2916                         h->resv_huge_pages--;
2917                 }
2918                 spin_lock_irq(&hugetlb_lock);
2919                 list_add(&page->lru, &h->hugepage_activelist);
2920                 /* Fall through */
2921         }
2922         hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, page);
2923         /* If allocation is not consuming a reservation, also store the
2924          * hugetlb_cgroup pointer on the page.
2925          */
2926         if (deferred_reserve) {
2927                 hugetlb_cgroup_commit_charge_rsvd(idx, pages_per_huge_page(h),
2928                                                   h_cg, page);
2929         }
2930 
2931         spin_unlock_irq(&hugetlb_lock);
2932 
2933         hugetlb_set_page_subpool(page, spool);
2934 
2935         map_commit = vma_commit_reservation(h, vma, addr);
2936         if (unlikely(map_chg > map_commit)) {
2937                 /*
2938                  * The page was added to the reservation map between
2939                  * vma_needs_reservation and vma_commit_reservation.
2940                  * This indicates a race with hugetlb_reserve_pages.
2941                  * Adjust for the subpool count incremented above AND
2942                  * in hugetlb_reserve_pages for the same page.  Also,
2943                  * the reservation count added in hugetlb_reserve_pages
2944                  * no longer applies.
2945                  */
2946                 long rsv_adjust;
2947 
2948                 rsv_adjust = hugepage_subpool_put_pages(spool, 1);
2949                 hugetlb_acct_memory(h, -rsv_adjust);
2950                 if (deferred_reserve)
2951                         hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h),
2952                                         pages_per_huge_page(h), page);
2953         }
2954         return page;
2955 
2956 out_uncharge_cgroup:
2957         hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg);
2958 out_uncharge_cgroup_reservation:
2959         if (deferred_reserve)
2960                 hugetlb_cgroup_uncharge_cgroup_rsvd(idx, pages_per_huge_page(h),
2961                                                     h_cg);
2962 out_subpool_put:
2963         if (map_chg || avoid_reserve)
2964                 hugepage_subpool_put_pages(spool, 1);
2965         vma_end_reservation(h, vma, addr);
2966         return ERR_PTR(-ENOSPC);
2967 }
2968 
2969 int alloc_bootmem_huge_page(struct hstate *h, int nid)
2970         __attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
2971 int __alloc_bootmem_huge_page(struct hstate *h, int nid)
2972 {
2973         struct huge_bootmem_page *m = NULL; /* initialize for clang */
2974         int nr_nodes, node;
2975 
2976         if (nid >= nr_online_nodes)
2977                 return 0;
2978         /* do node specific alloc */
2979         if (nid != NUMA_NO_NODE) {
2980                 m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h),
2981                                 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
2982                 if (!m)
2983                         return 0;
2984                 goto found;
2985         }
2986         /* allocate from next node when distributing huge pages */
2987         for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
2988                 m = memblock_alloc_try_nid_raw(
2989                                 huge_page_size(h), huge_page_size(h),
2990                                 0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
2991                 /*
2992                  * Use the beginning of the huge page to store the
2993                  * huge_bootmem_page struct (until gather_bootmem
2994                  * puts them into the mem_map).
2995                  */
2996                 if (!m)
2997                         return 0;
2998                 goto found;
2999         }
3000 
3001 found:
3002         /* Put them into a private list first because mem_map is not up yet */
3003         INIT_LIST_HEAD(&m->list);
3004         list_add(&m->list, &huge_boot_pages);
3005         m->hstate = h;
3006         return 1;
3007 }
3008 
3009 /*
3010  * Put bootmem huge pages into the standard lists after mem_map is up.
3011  * Note: This only applies to gigantic (order > MAX_ORDER) pages.
3012  */
3013 static void __init gather_bootmem_prealloc(void)
3014 {
3015         struct huge_bootmem_page *m;
3016 
3017         list_for_each_entry(m, &huge_boot_pages, list) {
3018                 struct page *page = virt_to_page(m);
3019                 struct hstate *h = m->hstate;
3020 
3021                 VM_BUG_ON(!hstate_is_gigantic(h));
3022                 WARN_ON(page_count(page) != 1);
3023                 if (prep_compound_gigantic_page(page, huge_page_order(h))) {
3024                         WARN_ON(PageReserved(page));
3025                         prep_new_huge_page(h, page, page_to_nid(page));
3026                         put_page(page); /* add to the hugepage allocator */
3027                 } else {
3028                         /* VERY unlikely inflated ref count on a tail page */
3029                         free_gigantic_page(page, huge_page_order(h));
3030                 }
3031 
3032                 /*
3033                  * We need to restore the 'stolen' pages to totalram_pages
3034                  * in order to fix confusing memory reports from free(1) and
3035                  * other side-effects, like CommitLimit going negative.
3036                  */
3037                 adjust_managed_page_count(page, pages_per_huge_page(h));
3038                 cond_resched();
3039         }
3040 }
3041 static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
3042 {
3043         unsigned long i;
3044         char buf[32];
3045 
3046         for (i = 0; i < h->max_huge_pages_node[nid]; ++i) {
3047                 if (hstate_is_gigantic(h)) {
3048                         if (!alloc_bootmem_huge_page(h, nid))
3049                                 break;
3050                 } else {
3051                         struct page *page;
3052                         gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
3053 
3054                         page = alloc_fresh_huge_page(h, gfp_mask, nid,
3055                                         &node_states[N_MEMORY], NULL);
3056                         if (!page)
3057                                 break;
3058                         put_page(page); /* free it into the hugepage allocator */
3059                 }
3060                 cond_resched();
3061         }
3062         if (i == h->max_huge_pages_node[nid])
3063                 return;
3064 
3065         string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
3066         pr_warn("HugeTLB: allocating %u of page size %s failed node%d.  Only allocated %lu hugepages.\n",
3067                 h->max_huge_pages_node[nid], buf, nid, i);
3068         h->max_huge_pages -= (h->max_huge_pages_node[nid] - i);
3069         h->max_huge_pages_node[nid] = i;
3070 }
3071 
3072 static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
3073 {
3074         unsigned long i;
3075         nodemask_t *node_alloc_noretry;
3076         bool node_specific_alloc = false;
3077 
3078         /* skip gigantic hugepages allocation if hugetlb_cma enabled */
3079         if (hstate_is_gigantic(h) && hugetlb_cma_size) {
3080                 pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip boot time allocation\n");
3081                 return;
3082         }
3083 
3084         /* do node specific alloc */
3085         for (i = 0; i < nr_online_nodes; i++) {
3086                 if (h->max_huge_pages_node[i] > 0) {
3087                         hugetlb_hstate_alloc_pages_onenode(h, i);
3088                         node_specific_alloc = true;
3089                 }
3090         }
3091 
3092         if (node_specific_alloc)
3093                 return;
3094 
3095         /* below will do all node balanced alloc */
3096         if (!hstate_is_gigantic(h)) {
3097                 /*
3098                  * Bit mask controlling how hard we retry per-node allocations.
3099                  * Ignore errors as lower level routines can deal with
3100                  * node_alloc_noretry == NULL.  If this kmalloc fails at boot
3101                  * time, we are likely in bigger trouble.
3102                  */
3103                 node_alloc_noretry = kmalloc(sizeof(*node_alloc_noretry),
3104                                                 GFP_KERNEL);
3105         } else {
3106                 /* allocations done at boot time */
3107                 node_alloc_noretry = NULL;
3108         }
3109 
3110         /* bit mask controlling how hard we retry per-node allocations */
3111         if (node_alloc_noretry)
3112                 nodes_clear(*node_alloc_noretry);
3113 
3114         for (i = 0; i < h->max_huge_pages; ++i) {
3115                 if (hstate_is_gigantic(h)) {
3116                         if (!alloc_bootmem_huge_page(h, NUMA_NO_NODE))
3117                                 break;
3118                 } else if (!alloc_pool_huge_page(h,
3119                                          &node_states[N_MEMORY],
3120                                          node_alloc_noretry))
3121                         break;
3122                 cond_resched();
3123         }
3124         if (i < h->max_huge_pages) {
3125                 char buf[32];
3126 
3127                 string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
3128                 pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
3129                         h->max_huge_pages, buf, i);
3130                 h->max_huge_pages = i;
3131         }
3132         kfree(node_alloc_noretry);
3133 }
3134 
3135 static void __init hugetlb_init_hstates(void)
3136 {
3137         struct hstate *h, *h2;
3138 
3139         for_each_hstate(h) {
3140                 if (minimum_order > huge_page_order(h))
3141                         minimum_order = huge_page_order(h);
3142 
3143                 /* oversize hugepages were init'ed in early boot */
3144                 if (!hstate_is_gigantic(h))
3145                         hugetlb_hstate_alloc_pages(h);
3146 
3147                 /*
3148                  * Set demote order for each hstate.  Note that
3149                  * h->demote_order is initially 0.
3150                  * - We can not demote gigantic pages if runtime freeing
3151                  *   is not supported, so skip this.
3152                  * - If CMA allocation is possible, we can not demote
3153                  *   HUGETLB_PAGE_ORDER or smaller size pages.
3154                  */
3155                 if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
3156                         continue;
3157                 if (hugetlb_cma_size && h->order <= HUGETLB_PAGE_ORDER)
3158                         continue;
3159                 for_each_hstate(h2) {
3160                         if (h2 == h)
3161                                 continue;
3162                         if (h2->order < h->order &&
3163                             h2->order > h->demote_order)
3164                                 h->demote_order = h2->order;
3165                 }
3166         }
3167         VM_BUG_ON(minimum_order == UINT_MAX);
3168 }
3169 
3170 static void __init report_hugepages(void)
3171 {
3172         struct hstate *h;
3173 
3174         for_each_hstate(h) {
3175                 char buf[32];
3176 
3177                 string_get_size(huge_page_size(h), 1, STRING_UNITS_2, buf, 32);
3178                 pr_info("HugeTLB registered %s page size, pre-allocated %ld pages\n",
3179                         buf, h->free_huge_pages);
3180         }
3181 }
3182 
3183 #ifdef CONFIG_HIGHMEM
3184 static void try_to_free_low(struct hstate *h, unsigned long count,
3185                                                 nodemask_t *nodes_allowed)
3186 {
3187         int i;
3188         LIST_HEAD(page_list);
3189 
3190         lockdep_assert_held(&hugetlb_lock);
3191         if (hstate_is_gigantic(h))
3192                 return;
3193 
3194         /*
3195          * Collect pages to be freed on a list, and free after dropping lock
3196          */
3197         for_each_node_mask(i, *nodes_allowed) {
3198                 struct page *page, *next;
3199                 struct list_head *freel = &h->hugepage_freelists[i];
3200                 list_for_each_entry_safe(page, next, freel, lru) {
3201                         if (count >= h->nr_huge_pages)
3202                                 goto out;
3203                         if (PageHighMem(page))
3204                                 continue;
3205                         remove_hugetlb_page(h, page, false);
3206                         list_add(&page->lru, &page_list);
3207                 }
3208         }
3209 
3210 out:
3211         spin_unlock_irq(&hugetlb_lock);
3212         update_and_free_pages_bulk(h, &page_list);
3213         spin_lock_irq(&hugetlb_lock);
3214 }
3215 #else
3216 static inline void try_to_free_low(struct hstate *h, unsigned long count,
3217                                                 nodemask_t *nodes_allowed)
3218 {
3219 }
3220 #endif
3221 
3222 /*
3223  * Increment or decrement surplus_huge_pages.  Keep node-specific counters
3224  * balanced by operating on them in a round-robin fashion.
3225  * Returns 1 if an adjustment was made.
3226  */
3227 static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
3228                                 int delta)
3229 {
3230         int nr_nodes, node;
3231 
3232         lockdep_assert_held(&hugetlb_lock);
3233         VM_BUG_ON(delta != -1 && delta != 1);
3234 
3235         if (delta < 0) {
3236                 for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
3237                         if (h->surplus_huge_pages_node[node])
3238                                 goto found;
3239                 }
3240         } else {
3241                 for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
3242                         if (h->surplus_huge_pages_node[node] <
3243                                         h->nr_huge_pages_node[node])
3244                                 goto found;
3245                 }
3246         }
3247         return 0;
3248 
3249 found:
3250         h->surplus_huge_pages += delta;
3251         h->surplus_huge_pages_node[node] += delta;
3252         return 1;
3253 }
3254 
3255 #define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
3256 static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
3257                               nodemask_t *nodes_allowed)
3258 {
3259         unsigned long min_count, ret;
3260         struct page *page;
3261         LIST_HEAD(page_list);
3262         NODEMASK_ALLOC(nodemask_t, node_alloc_noretry, GFP_KERNEL);
3263 
3264         /*
3265          * Bit mask controlling how hard we retry per-node allocations.
3266          * If we can not allocate the bit mask, do not attempt to allocate
3267          * the requested huge pages.
3268          */
3269         if (node_alloc_noretry)
3270                 nodes_clear(*node_alloc_noretry);
3271         else
3272                 return -ENOMEM;
3273 
3274         /*
3275          * resize_lock mutex prevents concurrent adjustments to number of
3276          * pages in hstate via the proc/sysfs interfaces.
3277          */
3278         mutex_lock(&h->resize_lock);
3279         flush_free_hpage_work(h);
3280         spin_lock_irq(&hugetlb_lock);
3281 
3282         /*
3283          * Check for a node specific request.
3284          * Changing node specific huge page count may require a corresponding
3285          * change to the global count.  In any case, the passed node mask
3286          * (nodes_allowed) will restrict alloc/free to the specified node.
3287          */
3288         if (nid != NUMA_NO_NODE) {
3289                 unsigned long old_count = count;
3290 
3291                 count += h->nr_huge_pages - h->nr_huge_pages_node[nid];
3292                 /*
3293                  * User may have specified a large count value which caused the
3294                  * above calculation to overflow.  In this case, they wanted
3295                  * to allocate as many huge pages as possible.  Set count to
3296                  * largest possible value to align with their intention.
3297                  */
3298                 if (count < old_count)
3299                         count = ULONG_MAX;
3300         }
3301 
3302         /*
3303          * Gigantic pages runtime allocation depend on the capability for large
3304          * page range allocation.
3305          * If the system does not provide this feature, return an error when
3306          * the user tries to allocate gigantic pages but let the user free the
3307          * boottime allocated gigantic pages.
3308          */
3309         if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
3310                 if (count > persistent_huge_pages(h)) {
3311                         spin_unlock_irq(&hugetlb_lock);
3312                         mutex_unlock(&h->resize_lock);
3313                         NODEMASK_FREE(node_alloc_noretry);
3314                         return -EINVAL;
3315                 }
3316                 /* Fall through to decrease pool */
3317         }
3318 
3319         /*
3320          * Increase the pool size
3321          * First take pages out of surplus state.  Then make up the
3322          * remaining difference by allocating fresh huge pages.
3323          *
3324          * We might race with alloc_surplus_huge_page() here and be unable
3325          * to convert a surplus huge page to a normal huge page. That is
3326          * not critical, though, it just means the overall size of the
3327          * pool might be one hugepage larger than it needs to be, but
3328          * within all the constraints specified by the sysctls.
3329          */
3330         while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
3331                 if (!adjust_pool_surplus(h, nodes_allowed, -1))
3332                         break;
3333         }
3334 
3335         while (count > persistent_huge_pages(h)) {
3336                 /*
3337                  * If this allocation races such that we no longer need the
3338                  * page, free_huge_page will handle it by freeing the page
3339                  * and reducing the surplus.
3340                  */
3341                 spin_unlock_irq(&hugetlb_lock);
3342 
3343                 /* yield cpu to avoid soft lockup */
3344                 cond_resched();
3345 
3346                 ret = alloc_pool_huge_page(h, nodes_allowed,
3347                                                 node_alloc_noretry);
3348                 spin_lock_irq(&hugetlb_lock);
3349                 if (!ret)
3350                         goto out;
3351 
3352                 /* Bail for signals. Probably ctrl-c from user */
3353                 if (signal_pending(current))
3354                         goto out;
3355         }
3356 
3357         /*
3358          * Decrease the pool size
3359          * First return free pages to the buddy allocator (being careful
3360          * to keep enough around to satisfy reservations).  Then place
3361          * pages into surplus state as needed so the pool will shrink
3362          * to the desired size as pages become free.
3363          *
3364          * By placing pages into the surplus state independent of the
3365          * overcommit value, we are allowing the surplus pool size to
3366          * exceed overcommit. There are few sane options here. Since
3367          * alloc_surplus_huge_page() is checking the global counter,
3368          * though, we'll note that we're not allowed to exceed surplus
3369          * and won't grow the pool anywhere else. Not until one of the
3370          * sysctls are changed, or the surplus pages go out of use.
3371          */
3372         min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;
3373         min_count = max(count, min_count);
3374         try_to_free_low(h, min_count, nodes_allowed);
3375 
3376         /*
3377          * Collect pages to be removed on list without dropping lock
3378          */
3379         while (min_count < persistent_huge_pages(h)) {
3380                 page = remove_pool_huge_page(h, nodes_allowed, 0);
3381                 if (!page)
3382                         break;
3383 
3384                 list_add(&page->lru, &page_list);
3385         }
3386         /* free the pages after dropping lock */
3387         spin_unlock_irq(&hugetlb_lock);
3388         update_and_free_pages_bulk(h, &page_list);
3389         flush_free_hpage_work(h);
3390         spin_lock_irq(&hugetlb_lock);
3391 
3392         while (count < persistent_huge_pages(h)) {
3393                 if (!adjust_pool_surplus(h, nodes_allowed, 1))
3394                         break;
3395         }
3396 out:
3397         h->max_huge_pages = persistent_huge_pages(h);
3398         spin_unlock_irq(&hugetlb_lock);
3399         mutex_unlock(&h->resize_lock);
3400 
3401         NODEMASK_FREE(node_alloc_noretry);
3402 
3403         return 0;
3404 }
3405 
3406 static int demote_free_huge_page(struct hstate *h, struct page *page)
3407 {
3408         int i, nid = page_to_nid(page);
3409         struct hstate *target_hstate;
3410         int rc = 0;
3411 
3412         target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order);
3413 
3414         remove_hugetlb_page_for_demote(h, page, false);
3415         spin_unlock_irq(&hugetlb_lock);
3416 
3417         rc = alloc_huge_page_vmemmap(h, page);
3418         if (rc) {
3419                 /* Allocation of vmemmmap failed, we can not demote page */
3420                 spin_lock_irq(&hugetlb_lock);
3421                 set_page_refcounted(page);
3422                 add_hugetlb_page(h, page, false);
3423                 return rc;
3424         }
3425 
3426         /*
3427          * Use destroy_compound_hugetlb_page_for_demote for all huge page
3428          * sizes as it will not ref count pages.
3429          */
3430         destroy_compound_hugetlb_page_for_demote(page, huge_page_order(h));
3431 
3432         /*
3433          * Taking target hstate mutex synchronizes with set_max_huge_pages.
3434          * Without the mutex, pages added to target hstate could be marked
3435          * as surplus.
3436          *
3437          * Note that we already hold h->resize_lock.  To prevent deadlock,
3438          * use the convention of always taking larger size hstate mutex first.
3439          */
3440         mutex_lock(&target_hstate->resize_lock);
3441         for (i = 0; i < pages_per_huge_page(h);
3442                                 i += pages_per_huge_page(target_hstate)) {
3443                 if (hstate_is_gigantic(target_hstate))
3444                         prep_compound_gigantic_page_for_demote(page + i,
3445                                                         target_hstate->order);
3446                 else
3447                         prep_compound_page(page + i, target_hstate->order);
3448                 set_page_private(page + i, 0);
3449                 set_page_refcounted(page + i);
3450                 prep_new_huge_page(target_hstate, page + i, nid);
3451                 put_page(page + i);
3452         }
3453         mutex_unlock(&target_hstate->resize_lock);
3454 
3455         spin_lock_irq(&hugetlb_lock);
3456 
3457         /*
3458          * Not absolutely necessary, but for consistency update max_huge_pages
3459          * based on pool changes for the demoted page.
3460          */
3461         h->max_huge_pages--;
3462         target_hstate->max_huge_pages += pages_per_huge_page(h);
3463 
3464         return rc;
3465 }
3466 
3467 static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
3468         __must_hold(&hugetlb_lock)
3469 {
3470         int nr_nodes, node;
3471         struct page *page;
3472         int rc = 0;
3473 
3474         lockdep_assert_held(&hugetlb_lock);
3475 
3476         /* We should never get here if no demote order */
3477         if (!h->demote_order) {
3478                 pr_warn("HugeTLB: NULL demote order passed to demote_pool_huge_page.\n");
3479                 return -EINVAL;         /* internal error */
3480         }
3481 
3482         for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
3483                 if (!list_empty(&h->hugepage_freelists[node])) {
3484                         page = list_entry(h->hugepage_freelists[node].next,
3485                                         struct page, lru);
3486                         rc = demote_free_huge_page(h, page);
3487                         break;
3488                 }
3489         }
3490 
3491         return rc;
3492 }
3493 
3494 #define HSTATE_ATTR_RO(_name) \
3495         static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
3496 
3497 #define HSTATE_ATTR_WO(_name) \
3498         static struct kobj_attribute _name##_attr = __ATTR_WO(_name)
3499 
3500 #define HSTATE_ATTR(_name) \
3501         static struct kobj_attribute _name##_attr = \
3502                 __ATTR(_name, 0644, _name##_show, _name##_store)
3503 
3504 static struct kobject *hugepages_kobj;
3505 static struct kobject *hstate_kobjs[HUGE_MAX_HSTATE];
3506 
3507 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp);
3508 
3509 static struct hstate *kobj_to_hstate(struct kobject *kobj, int *nidp)
3510 {
3511         int i;
3512 
3513         for (i = 0; i < HUGE_MAX_HSTATE; i++)
3514                 if (hstate_kobjs[i] == kobj) {
3515                         if (nidp)
3516                                 *nidp = NUMA_NO_NODE;
3517                         return &hstates[i];
3518                 }
3519 
3520         return kobj_to_node_hstate(kobj, nidp);
3521 }
3522 
3523 static ssize_t nr_hugepages_show_common(struct kobject *kobj,
3524                                         struct kobj_attribute *attr, char *buf)
3525 {
3526         struct hstate *h;
3527         unsigned long nr_huge_pages;
3528         int nid;
3529 
3530         h = kobj_to_hstate(kobj, &nid);
3531         if (nid == NUMA_NO_NODE)
3532                 nr_huge_pages = h->nr_huge_pages;
3533         else
3534                 nr_huge_pages = h->nr_huge_pages_node[nid];
3535 
3536         return sysfs_emit(buf, "%lu\n", nr_huge_pages);
3537 }
3538 
3539 static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
3540                                            struct hstate *h, int nid,
3541                                            unsigned long count, size_t len)
3542 {
3543         int err;
3544         nodemask_t nodes_allowed, *n_mask;
3545 
3546         if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
3547                 return -EINVAL;
3548 
3549         if (nid == NUMA_NO_NODE) {
3550                 /*
3551                  * global hstate attribute
3552                  */
3553                 if (!(obey_mempolicy &&
3554                                 init_nodemask_of_mempolicy(&nodes_allowed)))
3555                         n_mask = &node_states[N_MEMORY];
3556                 else
3557                         n_mask = &nodes_allowed;
3558         } else {
3559                 /*
3560                  * Node specific request.  count adjustment happens in
3561                  * set_max_huge_pages() after acquiring hugetlb_lock.
3562                  */
3563                 init_nodemask_of_node(&nodes_allowed, nid);
3564                 n_mask = &nodes_allowed;
3565         }
3566 
3567         err = set_max_huge_pages(h, count, nid, n_mask);
3568 
3569         return err ? err : len;
3570 }
3571 
3572 static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
3573                                          struct kobject *kobj, const char *buf,
3574                                          size_t len)
3575 {
3576         struct hstate *h;
3577         unsigned long count;
3578         int nid;
3579         int err;
3580 
3581         err = kstrtoul(buf, 10, &count);
3582         if (err)
3583                 return err;
3584 
3585         h = kobj_to_hstate(kobj, &nid);
3586         return __nr_hugepages_store_common(obey_mempolicy, h, nid, count, len);
3587 }
3588 
3589 static ssize_t nr_hugepages_show(struct kobject *kobj,
3590                                        struct kobj_attribute *attr, char *buf)
3591 {
3592         return nr_hugepages_show_common(kobj, attr, buf);
3593 }
3594 
3595 static ssize_t nr_hugepages_store(struct kobject *kobj,
3596                struct kobj_attribute *attr, const char *buf, size_t len)
3597 {
3598         return nr_hugepages_store_common(false, kobj, buf, len);
3599 }
3600 HSTATE_ATTR(nr_hugepages);
3601 
3602 #ifdef CONFIG_NUMA
3603 
3604 /*
3605  * hstate attribute for optionally mempolicy-based constraint on persistent
3606  * huge page alloc/free.
3607  */
3608 static ssize_t nr_hugepages_mempolicy_show(struct kobject *kobj,
3609                                            struct kobj_attribute *attr,
3610                                            char *buf)
3611 {
3612         return nr_hugepages_show_common(kobj, attr, buf);
3613 }
3614 
3615 static ssize_t nr_hugepages_mempolicy_store(struct kobject *kobj,
3616                struct kobj_attribute *attr, const char *buf, size_t len)
3617 {
3618         return nr_hugepages_store_common(true, kobj, buf, len);
3619 }
3620 HSTATE_ATTR(nr_hugepages_mempolicy);
3621 #endif
3622 
3623 
3624 static ssize_t nr_overcommit_hugepages_show(struct kobject *kobj,
3625                                         struct kobj_attribute *attr, char *buf)
3626 {
3627         struct hstate *h = kobj_to_hstate(kobj, NULL);
3628         return sysfs_emit(buf, "%lu\n", h->nr_overcommit_huge_pages);
3629 }
3630 
3631 static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
3632                 struct kobj_attribute *attr, const char *buf, size_t count)
3633 {
3634         int err;
3635         unsigned long input;
3636         struct hstate *h = kobj_to_hstate(kobj, NULL);
3637 
3638         if (hstate_is_gigantic(h))
3639                 return -EINVAL;
3640 
3641         err = kstrtoul(buf, 10, &input);
3642         if (err)
3643                 return err;
3644 
3645         spin_lock_irq(&hugetlb_lock);
3646         h->nr_overcommit_huge_pages = input;
3647         spin_unlock_irq(&hugetlb_lock);
3648 
3649         return count;
3650 }
3651 HSTATE_ATTR(nr_overcommit_hugepages);
3652 
3653 static ssize_t free_hugepages_show(struct kobject *kobj,
3654                                         struct kobj_attribute *attr, char *buf)
3655 {
3656         struct hstate *h;
3657         unsigned long free_huge_pages;
3658         int nid;
3659 
3660         h = kobj_to_hstate(kobj, &nid);
3661         if (nid == NUMA_NO_NODE)
3662                 free_huge_pages = h->free_huge_pages;
3663         else
3664                 free_huge_pages = h->free_huge_pages_node[nid];
3665 
3666         return sysfs_emit(buf, "%lu\n", free_huge_pages);
3667 }
3668 HSTATE_ATTR_RO(free_hugepages);
3669 
3670 static ssize_t resv_hugepages_show(struct kobject *kobj,
3671                                         struct kobj_attribute *attr, char *buf)
3672 {
3673         struct hstate *h = kobj_to_hstate(kobj, NULL);
3674         return sysfs_emit(buf, "%lu\n", h->resv_huge_pages);
3675 }
3676 HSTATE_ATTR_RO(resv_hugepages);
3677 
3678 static ssize_t surplus_hugepages_show(struct kobject *kobj,
3679                                         struct kobj_attribute *attr, char *buf)
3680 {
3681         struct hstate *h;
3682         unsigned long surplus_huge_pages;
3683         int nid;
3684 
3685         h = kobj_to_hstate(kobj, &nid);
3686         if (nid == NUMA_NO_NODE)
3687                 surplus_huge_pages = h->surplus_huge_pages;
3688         else
3689                 surplus_huge_pages = h->surplus_huge_pages_node[nid];
3690 
3691         return sysfs_emit(buf, "%lu\n", surplus_huge_pages);
3692 }
3693 HSTATE_ATTR_RO(surplus_hugepages);
3694 
3695 static ssize_t demote_store(struct kobject *kobj,
3696                struct kobj_attribute *attr, const char *buf, size_t len)
3697 {
3698         unsigned long nr_demote;
3699         unsigned long nr_available;
3700         nodemask_t nodes_allowed, *n_mask;
3701         struct hstate *h;
3702         int err = 0;
3703         int nid;
3704 
3705         err = kstrtoul(buf, 10, &nr_demote);
3706         if (err)
3707                 return err;
3708         h = kobj_to_hstate(kobj, &nid);
3709 
3710         if (nid != NUMA_NO_NODE) {
3711                 init_nodemask_of_node(&nodes_allowed, nid);
3712                 n_mask = &nodes_allowed;
3713         } else {
3714                 n_mask = &node_states[N_MEMORY];
3715         }
3716 
3717         /* Synchronize with other sysfs operations modifying huge pages */
3718         mutex_lock(&h->resize_lock);
3719         spin_lock_irq(&hugetlb_lock);
3720 
3721         while (nr_demote) {
3722                 /*
3723                  * Check for available pages to demote each time thorough the
3724                  * loop as demote_pool_huge_page will drop hugetlb_lock.
3725                  */
3726                 if (nid != NUMA_NO_NODE)
3727                         nr_available = h->free_huge_pages_node[nid];
3728                 else
3729                         nr_available = h->free_huge_pages;
3730                 nr_available -= h->resv_huge_pages;
3731                 if (!nr_available)
3732                         break;
3733 
3734                 err = demote_pool_huge_page(h, n_mask);
3735                 if (err)
3736                         break;
3737 
3738                 nr_demote--;
3739         }
3740 
3741         spin_unlock_irq(&hugetlb_lock);
3742         mutex_unlock(&h->resize_lock);
3743 
3744         if (err)
3745                 return err;
3746         return len;
3747 }
3748 HSTATE_ATTR_WO(demote);
3749 
3750 static ssize_t demote_size_show(struct kobject *kobj,
3751                                         struct kobj_attribute *attr, char *buf)
3752 {
3753         int nid;
3754         struct hstate *h = kobj_to_hstate(kobj, &nid);
3755         unsigned long demote_size = (PAGE_SIZE << h->demote_order) / SZ_1K;
3756 
3757         return sysfs_emit(buf, "%lukB\n", demote_size);
3758 }
3759 
3760 static ssize_t demote_size_store(struct kobject *kobj,
3761                                         struct kobj_attribute *attr,
3762                                         const char *buf, size_t count)
3763 {
3764         struct hstate *h, *demote_hstate;
3765         unsigned long demote_size;
3766         unsigned int demote_order;
3767         int nid;
3768 
3769         demote_size = (unsigned long)memparse(buf, NULL);
3770 
3771         demote_hstate = size_to_hstate(demote_size);
3772         if (!demote_hstate)
3773                 return -EINVAL;
3774         demote_order = demote_hstate->order;
3775         if (demote_order < HUGETLB_PAGE_ORDER)
3776                 return -EINVAL;
3777 
3778         /* demote order must be smaller than hstate order */
3779         h = kobj_to_hstate(kobj, &nid);
3780         if (demote_order >= h->order)
3781                 return -EINVAL;
3782 
3783         /* resize_lock synchronizes access to demote size and writes */
3784         mutex_lock(&h->resize_lock);
3785         h->demote_order = demote_order;
3786         mutex_unlock(&h->resize_lock);
3787 
3788         return count;
3789 }
3790 HSTATE_ATTR(demote_size);
3791 
3792 static struct attribute *hstate_attrs[] = {
3793         &nr_hugepages_attr.attr,
3794         &nr_overcommit_hugepages_attr.attr,
3795         &free_hugepages_attr.attr,
3796         &resv_hugepages_attr.attr,
3797         &surplus_hugepages_attr.attr,
3798 #ifdef CONFIG_NUMA
3799         &nr_hugepages_mempolicy_attr.attr,
3800 #endif
3801         NULL,
3802 };
3803 
3804 static const struct attribute_group hstate_attr_group = {
3805         .attrs = hstate_attrs,
3806 };
3807 
3808 static struct attribute *hstate_demote_attrs[] = {
3809         &demote_size_attr.attr,
3810         &demote_attr.attr,
3811         NULL,
3812 };
3813 
3814 static const struct attribute_group hstate_demote_attr_group = {
3815         .attrs = hstate_demote_attrs,
3816 };
3817 
3818 static int hugetlb_sysfs_add_hstate(struct hstate *h, struct kobject *parent,
3819                                     struct kobject **hstate_kobjs,
3820                                     const struct attribute_group *hstate_attr_group)
3821 {
3822         int retval;
3823         int hi = hstate_index(h);
3824 
3825         hstate_kobjs[hi] = kobject_create_and_add(h->name, parent);
3826         if (!hstate_kobjs[hi])
3827                 return -ENOMEM;
3828 
3829         retval = sysfs_create_group(hstate_kobjs[hi], hstate_attr_group);
3830         if (retval) {
3831                 kobject_put(hstate_kobjs[hi]);
3832                 hstate_kobjs[hi] = NULL;
3833         }
3834 
3835         if (h->demote_order) {
3836                 if (sysfs_create_group(hstate_kobjs[hi],
3837                                         &hstate_demote_attr_group))
3838                         pr_warn("HugeTLB unable to create demote interfaces for %s\n", h->name);
3839         }
3840 
3841         return retval;
3842 }
3843 
3844 static void __init hugetlb_sysfs_init(void)
3845 {
3846         struct hstate *h;
3847         int err;
3848 
3849         hugepages_kobj = kobject_create_and_add("hugepages", mm_kobj);
3850         if (!hugepages_kobj)
3851                 return;
3852 
3853         for_each_hstate(h) {
3854                 err = hugetlb_sysfs_add_hstate(h, hugepages_kobj,
3855                                          hstate_kobjs, &hstate_attr_group);
3856                 if (err)
3857                         pr_err("HugeTLB: Unable to add hstate %s", h->name);
3858         }
3859 }
3860 
3861 #ifdef CONFIG_NUMA
3862 
3863 /*
3864  * node_hstate/s - associate per node hstate attributes, via their kobjects,
3865  * with node devices in node_devices[] using a parallel array.  The array
3866  * index of a node device or _hstate == node id.
3867  * This is here to avoid any static dependency of the node device driver, in
3868  * the base kernel, on the hugetlb module.
3869  */
3870 struct node_hstate {
3871         struct kobject          *hugepages_kobj;
3872         struct kobject          *hstate_kobjs[HUGE_MAX_HSTATE];
3873 };
3874 static struct node_hstate node_hstates[MAX_NUMNODES];
3875 
3876 /*
3877  * A subset of global hstate attributes for node devices
3878  */
3879 static struct attribute *per_node_hstate_attrs[] = {
3880         &nr_hugepages_attr.attr,
3881         &free_hugepages_attr.attr,
3882         &surplus_hugepages_attr.attr,
3883         NULL,
3884 };
3885 
3886 static const struct attribute_group per_node_hstate_attr_group = {
3887         .attrs = per_node_hstate_attrs,
3888 };
3889 
3890 /*
3891  * kobj_to_node_hstate - lookup global hstate for node device hstate attr kobj.
3892  * Returns node id via non-NULL nidp.
3893  */
3894 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
3895 {
3896         int nid;
3897 
3898         for (nid = 0; nid < nr_node_ids; nid++) {
3899                 struct node_hstate *nhs = &node_hstates[nid];
3900                 int i;
3901                 for (i = 0; i < HUGE_MAX_HSTATE; i++)
3902                         if (nhs->hstate_kobjs[i] == kobj) {
3903                                 if (nidp)
3904                                         *nidp = nid;
3905                                 return &hstates[i];
3906                         }
3907         }
3908 
3909         BUG();
3910         return NULL;
3911 }
3912 
3913 /*
3914  * Unregister hstate attributes from a single node device.
3915  * No-op if no hstate attributes attached.
3916  */
3917 static void hugetlb_unregister_node(struct node *node)
3918 {
3919         struct hstate *h;
3920         struct node_hstate *nhs = &node_hstates[node->dev.id];
3921 
3922         if (!nhs->hugepages_kobj)
3923                 return;         /* no hstate attributes */
3924 
3925         for_each_hstate(h) {
3926                 int idx = hstate_index(h);
3927                 if (nhs->hstate_kobjs[idx]) {
3928                         kobject_put(nhs->hstate_kobjs[idx]);
3929                         nhs->hstate_kobjs[idx] = NULL;
3930                 }
3931         }
3932 
3933         kobject_put(nhs->hugepages_kobj);
3934         nhs->hugepages_kobj = NULL;
3935 }
3936 
3937 
3938 /*
3939  * Register hstate attributes for a single node device.
3940  * No-op if attributes already registered.
3941  */
3942 static void hugetlb_register_node(struct node *node)
3943 {
3944         struct hstate *h;
3945         struct node_hstate *nhs = &node_hstates[node->dev.id];
3946         int err;
3947 
3948         if (nhs->hugepages_kobj)
3949                 return;         /* already allocated */
3950 
3951         nhs->hugepages_kobj = kobject_create_and_add("hugepages",
3952                                                         &node->dev.kobj);
3953         if (!nhs->hugepages_kobj)
3954                 return;
3955 
3956         for_each_hstate(h) {
3957                 err = hugetlb_sysfs_add_hstate(h, nhs->hugepages_kobj,
3958                                                 nhs->hstate_kobjs,
3959                                                 &per_node_hstate_attr_group);
3960                 if (err) {
3961                         pr_err("HugeTLB: Unable to add hstate %s for node %d\n",
3962                                 h->name, node->dev.id);
3963                         hugetlb_unregister_node(node);
3964                         break;
3965                 }
3966         }
3967 }
3968 
3969 /*
3970  * hugetlb init time:  register hstate attributes for all registered node
3971  * devices of nodes that have memory.  All on-line nodes should have
3972  * registered their associated device by this time.
3973  */
3974 static void __init hugetlb_register_all_nodes(void)
3975 {
3976         int nid;
3977 
3978         for_each_node_state(nid, N_MEMORY) {
3979                 struct node *node = node_devices[nid];
3980                 if (node->dev.id == nid)
3981                         hugetlb_register_node(node);
3982         }
3983 
3984         /*
3985          * Let the node device driver know we're here so it can
3986          * [un]register hstate attributes on node hotplug.
3987          */
3988         register_hugetlbfs_with_node(hugetlb_register_node,
3989                                      hugetlb_unregister_node);
3990 }
3991 #else   /* !CONFIG_NUMA */
3992 
3993 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
3994 {
3995         BUG();
3996         if (nidp)
3997                 *nidp = -1;
3998         return NULL;
3999 }
4000 
4001 static void hugetlb_register_all_nodes(void) { }
4002 
4003 #endif
4004 
4005 static int __init hugetlb_init(void)
4006 {
4007         int i;
4008 
4009         BUILD_BUG_ON(sizeof_field(struct page, private) * BITS_PER_BYTE <
4010                         __NR_HPAGEFLAGS);
4011 
4012         if (!hugepages_supported()) {
4013                 if (hugetlb_max_hstate || default_hstate_max_huge_pages)
4014                         pr_warn("HugeTLB: huge pages not supported, ignoring associated command-line parameters\n");
4015                 return 0;
4016         }
4017 
4018         /*
4019          * Make sure HPAGE_SIZE (HUGETLB_PAGE_ORDER) hstate exists.  Some
4020          * architectures depend on setup being done here.
4021          */
4022         hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
4023         if (!parsed_default_hugepagesz) {
4024                 /*
4025                  * If we did not parse a default huge page size, set
4026                  * default_hstate_idx to HPAGE_SIZE hstate. And, if the
4027                  * number of huge pages for this default size was implicitly
4028                  * specified, set that here as well.
4029                  * Note that the implicit setting will overwrite an explicit
4030                  * setting.  A warning will be printed in this case.
4031                  */
4032                 default_hstate_idx = hstate_index(size_to_hstate(HPAGE_SIZE));
4033                 if (default_hstate_max_huge_pages) {
4034                         if (default_hstate.max_huge_pages) {
4035                                 char buf[32];
4036 
4037                                 string_get_size(huge_page_size(&default_hstate),
4038                                         1, STRING_UNITS_2, buf, 32);
4039                                 pr_warn("HugeTLB: Ignoring hugepages=%lu associated with %s page size\n",
4040                                         default_hstate.max_huge_pages, buf);
4041                                 pr_warn("HugeTLB: Using hugepages=%lu for number of default huge pages\n",
4042                                         default_hstate_max_huge_pages);
4043                         }
4044                         default_hstate.max_huge_pages =
4045                                 default_hstate_max_huge_pages;
4046 
4047                         for (i = 0; i < nr_online_nodes; i++)
4048                                 default_hstate.max_huge_pages_node[i] =
4049                                         default_hugepages_in_node[i];
4050                 }
4051         }
4052 
4053         hugetlb_cma_check();
4054         hugetlb_init_hstates();
4055         gather_bootmem_prealloc();
4056         report_hugepages();
4057 
4058         hugetlb_sysfs_init();
4059         hugetlb_register_all_nodes();
4060         hugetlb_cgroup_file_init();
4061 
4062 #ifdef CONFIG_SMP
4063         num_fault_mutexes = roundup_pow_of_two(8 * num_possible_cpus());
4064 #else
4065         num_fault_mutexes = 1;
4066 #endif
4067         hugetlb_fault_mutex_table =
4068                 kmalloc_array(num_fault_mutexes, sizeof(struct mutex),
4069                               GFP_KERNEL);
4070         BUG_ON(!hugetlb_fault_mutex_table);
4071 
4072         for (i = 0; i < num_fault_mutexes; i++)
4073                 mutex_init(&hugetlb_fault_mutex_table[i]);
4074         return 0;
4075 }
4076 subsys_initcall(hugetlb_init);
4077 
4078 /* Overwritten by architectures with more huge page sizes */
4079 bool __init __attribute((weak)) arch_hugetlb_valid_size(unsigned long size)
4080 {
4081         return size == HPAGE_SIZE;
4082 }
4083 
4084 void __init hugetlb_add_hstate(unsigned int order)
4085 {
4086         struct hstate *h;
4087         unsigned long i;
4088 
4089         if (size_to_hstate(PAGE_SIZE << order)) {
4090                 return;
4091         }
4092         BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);
4093         BUG_ON(order == 0);
4094         h = &hstates[hugetlb_max_hstate++];
4095         mutex_init(&h->resize_lock);
4096         h->order = order;
4097         h->mask = ~(huge_page_size(h) - 1);
4098         for (i = 0; i < MAX_NUMNODES; ++i)
4099                 INIT_LIST_HEAD(&h->hugepage_freelists[i]);
4100         INIT_LIST_HEAD(&h->hugepage_activelist);
4101         h->next_nid_to_alloc = first_memory_node;
4102         h->next_nid_to_free = first_memory_node;
4103         snprintf(h->name, HSTATE_NAME_LEN, "hugepages-%lukB",
4104                                         huge_page_size(h)/1024);
4105         hugetlb_vmemmap_init(h);
4106 
4107         parsed_hstate = h;
4108 }
4109 
4110 bool __init __weak hugetlb_node_alloc_supported(void)
4111 {
4112         return true;
4113 }
4114 /*
4115  * hugepages command line processing
4116  * hugepages normally follows a valid hugepagsz or default_hugepagsz
4117  * specification.  If not, ignore the hugepages value.  hugepages can also
4118  * be the first huge page command line  option in which case it implicitly
4119  * specifies the number of huge pages for the default size.
4120  */
4121 static int __init hugepages_setup(char *s)
4122 {
4123         unsigned long *mhp;
4124         static unsigned long *last_mhp;
4125         int node = NUMA_NO_NODE;
4126         int count;
4127         unsigned long tmp;
4128         char *p = s;
4129 
4130         if (!parsed_valid_hugepagesz) {
4131                 pr_warn("HugeTLB: hugepages=%s does not follow a valid hugepagesz, ignoring\n", s);
4132                 parsed_valid_hugepagesz = true;
4133                 return 0;
4134         }
4135 
4136         /*
4137          * !hugetlb_max_hstate means we haven't parsed a hugepagesz= parameter
4138          * yet, so this hugepages= parameter goes to the "default hstate".
4139          * Otherwise, it goes with the previously parsed hugepagesz or
4140          * default_hugepagesz.
4141          */
4142         else if (!hugetlb_max_hstate)
4143                 mhp = &default_hstate_max_huge_pages;
4144         else
4145                 mhp = &parsed_hstate->max_huge_pages;
4146 
4147         if (mhp == last_mhp) {
4148                 pr_warn("HugeTLB: hugepages= specified twice without interleaving hugepagesz=, ignoring hugepages=%s\n", s);
4149                 return 0;
4150         }
4151 
4152         while (*p) {
4153                 count = 0;
4154                 if (sscanf(p, "%lu%n", &tmp, &count) != 1)
4155                         goto invalid;
4156                 /* Parameter is node format */
4157                 if (p[count] == ':') {
4158                         if (!hugetlb_node_alloc_supported()) {
4159                                 pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
4160                                 return 0;
4161                         }
4162                         node = tmp;
4163                         p += count + 1;
4164                         if (node < 0 || node >= nr_online_nodes)
4165                                 goto invalid;
4166                         /* Parse hugepages */
4167                         if (sscanf(p, "%lu%n", &tmp, &count) != 1)
4168                                 goto invalid;
4169                         if (!hugetlb_max_hstate)
4170                                 default_hugepages_in_node[node] = tmp;
4171                         else
4172                                 parsed_hstate->max_huge_pages_node[node] = tmp;
4173                         *mhp += tmp;
4174                         /* Go to parse next node*/
4175                         if (p[count] == ',')
4176                                 p += count + 1;
4177                         else
4178                                 break;
4179                 } else {
4180                         if (p != s)
4181                                 goto invalid;
4182                         *mhp = tmp;
4183                         break;
4184                 }
4185         }
4186 
4187         /*
4188          * Global state is always initialized later in hugetlb_init.
4189          * But we need to allocate gigantic hstates here early to still
4190          * use the bootmem allocator.
4191          */
4192         if (hugetlb_max_hstate && hstate_is_gigantic(parsed_hstate))
4193                 hugetlb_hstate_alloc_pages(parsed_hstate);
4194 
4195         last_mhp = mhp;
4196 
4197         return 1;
4198 
4199 invalid:
4200         pr_warn("HugeTLB: Invalid hugepages parameter %s\n", p);
4201         return 0;
4202 }
4203 __setup("hugepages=", hugepages_setup);
4204 
4205 /*
4206  * hugepagesz command line processing
4207  * A specific huge page size can only be specified once with hugepagesz.
4208  * hugepagesz is followed by hugepages on the command line.  The global
4209  * variable 'parsed_valid_hugepagesz' is used to determine if prior
4210  * hugepagesz argument was valid.
4211  */
4212 static int __init hugepagesz_setup(char *s)
4213 {
4214         unsigned long size;
4215         struct hstate *h;
4216 
4217         parsed_valid_hugepagesz = false;
4218         size = (unsigned long)memparse(s, NULL);
4219 
4220         if (!arch_hugetlb_valid_size(size)) {
4221                 pr_err("HugeTLB: unsupported hugepagesz=%s\n", s);
4222                 return 0;
4223         }
4224 
4225         h = size_to_hstate(size);
4226         if (h) {
4227                 /*
4228                  * hstate for this size already exists.  This is normally
4229                  * an error, but is allowed if the existing hstate is the
4230                  * default hstate.  More specifically, it is only allowed if
4231                  * the number of huge pages for the default hstate was not
4232                  * previously specified.
4233                  */
4234                 if (!parsed_default_hugepagesz ||  h != &default_hstate ||
4235                     default_hstate.max_huge_pages) {
4236                         pr_warn("HugeTLB: hugepagesz=%s specified twice, ignoring\n", s);
4237                         return 0;
4238                 }
4239 
4240                 /*
4241                  * No need to call hugetlb_add_hstate() as hstate already
4242                  * exists.  But, do set parsed_hstate so that a following
4243                  * hugepages= parameter will be applied to this hstate.
4244                  */
4245                 parsed_hstate = h;
4246                 parsed_valid_hugepagesz = true;
4247                 return 1;
4248         }
4249 
4250         hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
4251         parsed_valid_hugepagesz = true;
4252         return 1;
4253 }
4254 __setup("hugepagesz=", hugepagesz_setup);
4255 
4256 /*
4257  * default_hugepagesz command line input
4258  * Only one instance of default_hugepagesz allowed on command line.
4259  */
4260 static int __init default_hugepagesz_setup(char *s)
4261 {
4262         unsigned long size;
4263         int i;
4264 
4265         parsed_valid_hugepagesz = false;
4266         if (parsed_default_hugepagesz) {
4267                 pr_err("HugeTLB: default_hugepagesz previously specified, ignoring %s\n", s);
4268                 return 0;
4269         }
4270 
4271         size = (unsigned long)memparse(s, NULL);
4272 
4273         if (!arch_hugetlb_valid_size(size)) {
4274                 pr_err("HugeTLB: unsupported default_hugepagesz=%s\n", s);
4275                 return 0;
4276         }
4277 
4278         hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
4279         parsed_valid_hugepagesz = true;
4280         parsed_default_hugepagesz = true;
4281         default_hstate_idx = hstate_index(size_to_hstate(size));
4282 
4283         /*
4284          * The number of default huge pages (for this size) could have been
4285          * specified as the first hugetlb parameter: hugepages=X.  If so,
4286          * then default_hstate_max_huge_pages is set.  If the default huge
4287          * page size is gigantic (>= MAX_ORDER), then the pages must be
4288          * allocated here from bootmem allocator.
4289          */
4290         if (default_hstate_max_huge_pages) {
4291                 default_hstate.max_huge_pages = default_hstate_max_huge_pages;
4292                 for (i = 0; i < nr_online_nodes; i++)
4293                         default_hstate.max_huge_pages_node[i] =
4294                                 default_hugepages_in_node[i];
4295                 if (hstate_is_gigantic(&default_hstate))
4296                         hugetlb_hstate_alloc_pages(&default_hstate);
4297                 default_hstate_max_huge_pages = 0;
4298         }
4299 
4300         return 1;
4301 }
4302 __setup("default_hugepagesz=", default_hugepagesz_setup);
4303 
4304 static unsigned int allowed_mems_nr(struct hstate *h)
4305 {
4306         int node;
4307         unsigned int nr = 0;
4308         nodemask_t *mpol_allowed;
4309         unsigned int *array = h->free_huge_pages_node;
4310         gfp_t gfp_mask = htlb_alloc_mask(h);
4311 
4312         mpol_allowed = policy_nodemask_current(gfp_mask);
4313 
4314         for_each_node_mask(node, cpuset_current_mems_allowed) {
4315                 if (!mpol_allowed || node_isset(node, *mpol_allowed))
4316                         nr += array[node];
4317         }
4318 
4319         return nr;
4320 }
4321 
4322 #ifdef CONFIG_SYSCTL
4323 static int proc_hugetlb_doulongvec_minmax(struct ctl_table *table, int write,
4324                                           void *buffer, size_t *length,
4325                                           loff_t *ppos, unsigned long *out)
4326 {
4327         struct ctl_table dup_table;
4328 
4329         /*
4330          * In order to avoid races with __do_proc_doulongvec_minmax(), we
4331          * can duplicate the @table and alter the duplicate of it.
4332          */
4333         dup_table = *table;
4334         dup_table.data = out;
4335 
4336         return proc_doulongvec_minmax(&dup_table, write, buffer, length, ppos);
4337 }
4338 
4339 static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
4340                          struct ctl_table *table, int write,
4341                          void *buffer, size_t *length, loff_t *ppos)
4342 {
4343         struct hstate *h = &default_hstate;
4344         unsigned long tmp = h->max_huge_pages;
4345         int ret;
4346 
4347         if (!hugepages_supported())
4348                 return -EOPNOTSUPP;
4349 
4350         ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos,
4351                                              &tmp);
4352         if (ret)
4353                 goto out;
4354 
4355         if (write)
4356                 ret = __nr_hugepages_store_common(obey_mempolicy, h,
4357                                                   NUMA_NO_NODE, tmp, *length);
4358 out:
4359         return ret;
4360 }
4361 
4362 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
4363                           void *buffer, size_t *length, loff_t *ppos)
4364 {
4365 
4366         return hugetlb_sysctl_handler_common(false, table, write,
4367                                                         buffer, length, ppos);
4368 }
4369 
4370 #ifdef CONFIG_NUMA
4371 int hugetlb_mempolicy_sysctl_handler(struct ctl_table *table, int write,
4372                           void *buffer, size_t *length, loff_t *ppos)
4373 {
4374         return hugetlb_sysctl_handler_common(true, table, write,
4375                                                         buffer, length, ppos);
4376 }
4377 #endif /* CONFIG_NUMA */
4378 
4379 int hugetlb_overcommit_handler(struct ctl_table *table, int write,
4380                 void *buffer, size_t *length, loff_t *ppos)
4381 {
4382         struct hstate *h = &default_hstate;
4383         unsigned long tmp;
4384         int ret;
4385 
4386         if (!hugepages_supported())
4387                 return -EOPNOTSUPP;
4388 
4389         tmp = h->nr_overcommit_huge_pages;
4390 
4391         if (write && hstate_is_gigantic(h))
4392                 return -EINVAL;
4393 
4394         ret = proc_hugetlb_doulongvec_minmax(table, write, buffer, length, ppos,
4395                                              &tmp);
4396         if (ret)
4397                 goto out;
4398 
4399         if (write) {
4400                 spin_lock_irq(&hugetlb_lock);
4401                 h->nr_overcommit_huge_pages = tmp;
4402                 spin_unlock_irq(&hugetlb_lock);
4403         }
4404 out:
4405         return ret;
4406 }
4407 
4408 #endif /* CONFIG_SYSCTL */
4409 
4410 void hugetlb_report_meminfo(struct seq_file *m)
4411 {
4412         struct hstate *h;
4413         unsigned long total = 0;
4414 
4415         if (!hugepages_supported())
4416                 return;
4417 
4418         for_each_hstate(h) {
4419                 unsigned long count = h->nr_huge_pages;
4420 
4421                 total += huge_page_size(h) * count;
4422 
4423                 if (h == &default_hstate)
4424                         seq_printf(m,
4425                                    "HugePages_Total:   %5lu\n"
4426                                    "HugePages_Free:    %5lu\n"
4427                                    "HugePages_Rsvd:    %5lu\n"
4428                                    "HugePages_Surp:    %5lu\n"
4429                                    "Hugepagesize:   %8lu kB\n",
4430                                    count,
4431                                    h->free_huge_pages,
4432                                    h->resv_huge_pages,
4433                                    h->surplus_huge_pages,
4434                                    huge_page_size(h) / SZ_1K);
4435         }
4436 
4437         seq_printf(m, "Hugetlb:        %8lu kB\n", total / SZ_1K);
4438 }
4439 
4440 int hugetlb_report_node_meminfo(char *buf, int len, int nid)
4441 {
4442         struct hstate *h = &default_hstate;
4443 
4444         if (!hugepages_supported())
4445                 return 0;
4446 
4447         return sysfs_emit_at(buf, len,
4448                              "Node %d HugePages_Total: %5u\n"
4449                              "Node %d HugePages_Free:  %5u\n"
4450                              "Node %d HugePages_Surp:  %5u\n",
4451                              nid, h->nr_huge_pages_node[nid],
4452                              nid, h->free_huge_pages_node[nid],
4453                              nid, h->surplus_huge_pages_node[nid]);
4454 }
4455 
4456 void hugetlb_show_meminfo(void)
4457 {
4458         struct hstate *h;
4459         int nid;
4460 
4461         if (!hugepages_supported())
4462                 return;
4463 
4464         for_each_node_state(nid, N_MEMORY)
4465                 for_each_hstate(h)
4466                         pr_info("Node %d hugepages_total=%u hugepages_free=%u hugepages_surp=%u hugepages_size=%lukB\n",
4467                                 nid,
4468                                 h->nr_huge_pages_node[nid],
4469                                 h->free_huge_pages_node[nid],
4470                                 h->surplus_huge_pages_node[nid],
4471                                 huge_page_size(h) / SZ_1K);
4472 }
4473 
4474 void hugetlb_report_usage(struct seq_file *m, struct mm_struct *mm)
4475 {
4476         seq_printf(m, "HugetlbPages:\t%8lu kB\n",
4477                    atomic_long_read(&mm->hugetlb_usage) << (PAGE_SHIFT - 10));
4478 }
4479 
4480 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
4481 unsigned long hugetlb_total_pages(void)
4482 {
4483         struct hstate *h;
4484         unsigned long nr_total_pages = 0;
4485 
4486         for_each_hstate(h)
4487                 nr_total_pages += h->nr_huge_pages * pages_per_huge_page(h);
4488         return nr_total_pages;
4489 }
4490 
4491 static int hugetlb_acct_memory(struct hstate *h, long delta)
4492 {
4493         int ret = -ENOMEM;
4494 
4495         if (!delta)
4496                 return 0;
4497 
4498         spin_lock_irq(&hugetlb_lock);
4499         /*
4500          * When cpuset is configured, it breaks the strict hugetlb page
4501          * reservation as the accounting is done on a global variable. Such
4502          * reservation is completely rubbish in the presence of cpuset because
4503          * the reservation is not checked against page availability for the
4504          * current cpuset. Application can still potentially OOM'ed by kernel
4505          * with lack of free htlb page in cpuset that the task is in.
4506          * Attempt to enforce strict accounting with cpuset is almost
4507          * impossible (or too ugly) because cpuset is too fluid that
4508          * task or memory node can be dynamically moved between cpusets.
4509          *
4510          * The change of semantics for shared hugetlb mapping with cpuset is
4511          * undesirable. However, in order to preserve some of the semantics,
4512          * we fall back to check against current free page availability as
4513          * a best attempt and hopefully to minimize the impact of changing
4514          * semantics that cpuset has.
4515          *
4516          * Apart from cpuset, we also have memory policy mechanism that
4517          * also determines from which node the kernel will allocate memory
4518          * in a NUMA system. So similar to cpuset, we also should consider
4519          * the memory policy of the current task. Similar to the description
4520          * above.
4521          */
4522         if (delta > 0) {
4523                 if (gather_surplus_pages(h, delta) < 0)
4524                         goto out;
4525 
4526                 if (delta > allowed_mems_nr(h)) {
4527                         return_unused_surplus_pages(h, delta);
4528                         goto out;
4529                 }
4530         }
4531 
4532         ret = 0;
4533         if (delta < 0)
4534                 return_unused_surplus_pages(h, (unsigned long) -delta);
4535 
4536 out:
4537         spin_unlock_irq(&hugetlb_lock);
4538         return ret;
4539 }
4540 
4541 static void hugetlb_vm_op_open(struct vm_area_struct *vma)
4542 {
4543         struct resv_map *resv = vma_resv_map(vma);
4544 
4545         /*
4546          * This new VMA should share its siblings reservation map if present.
4547          * The VMA will only ever have a valid reservation map pointer where
4548          * it is being copied for another still existing VMA.  As that VMA
4549          * has a reference to the reservation map it cannot disappear until
4550          * after this open call completes.  It is therefore safe to take a
4551          * new reference here without additional locking.
4552          */
4553         if (resv && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
4554                 resv_map_dup_hugetlb_cgroup_uncharge_info(resv);
4555                 kref_get(&resv->refs);
4556         }
4557 }
4558 
4559 static void hugetlb_vm_op_close(struct vm_area_struct *vma)
4560 {
4561         struct hstate *h = hstate_vma(vma);
4562         struct resv_map *resv = vma_resv_map(vma);
4563         struct hugepage_subpool *spool = subpool_vma(vma);
4564         unsigned long reserve, start, end;
4565         long gbl_reserve;
4566 
4567         if (!resv || !is_vma_resv_set(vma, HPAGE_RESV_OWNER))
4568                 return;
4569 
4570         start = vma_hugecache_offset(h, vma, vma->vm_start);
4571         end = vma_hugecache_offset(h, vma, vma->vm_end);
4572 
4573         reserve = (end - start) - region_count(resv, start, end);
4574         hugetlb_cgroup_uncharge_counter(resv, start, end);
4575         if (reserve) {
4576                 /*
4577                  * Decrement reserve counts.  The global reserve count may be
4578                  * adjusted if the subpool has a minimum size.
4579                  */
4580                 gbl_reserve = hugepage_subpool_put_pages(spool, reserve);
4581                 hugetlb_acct_memory(h, -gbl_reserve);
4582         }
4583 
4584         kref_put(&resv->refs, resv_map_release);
4585 }
4586 
4587 static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr)
4588 {
4589         if (addr & ~(huge_page_mask(hstate_vma(vma))))
4590                 return -EINVAL;
4591         return 0;
4592 }
4593 
4594 static unsigned long hugetlb_vm_op_pagesize(struct vm_area_struct *vma)
4595 {
4596         return huge_page_size(hstate_vma(vma));
4597 }
4598 
4599 /*
4600  * We cannot handle pagefaults against hugetlb pages at all.  They cause
4601  * handle_mm_fault() to try to instantiate regular-sized pages in the
4602  * hugepage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
4603  * this far.
4604  */
4605 static vm_fault_t hugetlb_vm_op_fault(struct vm_fault *vmf)
4606 {
4607         BUG();
4608         return 0;
4609 }
4610 
4611 /*
4612  * When a new function is introduced to vm_operations_struct and added
4613  * to hugetlb_vm_ops, please consider adding the function to shm_vm_ops.
4614  * This is because under System V memory model, mappings created via
4615  * shmget/shmat with "huge page" specified are backed by hugetlbfs files,
4616  * their original vm_ops are overwritten with shm_vm_ops.
4617  */
4618 const struct vm_operations_struct hugetlb_vm_ops = {
4619         .fault = hugetlb_vm_op_fault,
4620         .open = hugetlb_vm_op_open,
4621         .close = hugetlb_vm_op_close,
4622         .may_split = hugetlb_vm_op_split,
4623         .pagesize = hugetlb_vm_op_pagesize,
4624 };
4625 
4626 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
4627                                 int writable)
4628 {
4629         pte_t entry;
4630         unsigned int shift = huge_page_shift(hstate_vma(vma));
4631 
4632         if (writable) {
4633                 entry = huge_pte_mkwrite(huge_pte_mkdirty(mk_huge_pte(page,
4634                                          vma->vm_page_prot)));
4635         } else {
4636                 entry = huge_pte_wrprotect(mk_huge_pte(page,
4637                                            vma->vm_page_prot));
4638         }
4639         entry = pte_mkyoung(entry);
4640         entry = pte_mkhuge(entry);
4641         entry = arch_make_huge_pte(entry, shift, vma->vm_flags);
4642 
4643         return entry;
4644 }
4645 
4646 static void set_huge_ptep_writable(struct vm_area_struct *vma,
4647                                    unsigned long address, pte_t *ptep)
4648 {
4649         pte_t entry;
4650 
4651         entry = huge_pte_mkwrite(huge_pte_mkdirty(huge_ptep_get(ptep)));
4652         if (huge_ptep_set_access_flags(vma, address, ptep, entry, 1))
4653                 update_mmu_cache(vma, address, ptep);
4654 }
4655 
4656 bool is_hugetlb_entry_migration(pte_t pte)
4657 {
4658         swp_entry_t swp;
4659 
4660         if (huge_pte_none(pte) || pte_present(pte))
4661                 return false;
4662         swp = pte_to_swp_entry(pte);
4663         if (is_migration_entry(swp))
4664                 return true;
4665         else
4666                 return false;
4667 }
4668 
4669 static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
4670 {
4671         swp_entry_t swp;
4672 
4673         if (huge_pte_none(pte) || pte_present(pte))
4674                 return false;
4675         swp = pte_to_swp_entry(pte);
4676         if (is_hwpoison_entry(swp))
4677                 return true;
4678         else
4679                 return false;
4680 }
4681 
4682 static void
4683 hugetlb_install_page(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr,
4684                      struct page *new_page)
4685 {
4686         __SetPageUptodate(new_page);
4687         set_huge_pte_at(vma->vm_mm, addr, ptep, make_huge_pte(vma, new_page, 1));
4688         hugepage_add_new_anon_rmap(new_page, vma, addr);
4689         hugetlb_count_add(pages_per_huge_page(hstate_vma(vma)), vma->vm_mm);
4690         ClearHPageRestoreReserve(new_page);
4691         SetHPageMigratable(new_page);
4692 }
4693 
4694 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
4695                             struct vm_area_struct *vma)
4696 {
4697         pte_t *src_pte, *dst_pte, entry, dst_entry;
4698         struct page *ptepage;
4699         unsigned long addr;
4700         bool cow = is_cow_mapping(vma->vm_flags);
4701         struct hstate *h = hstate_vma(vma);
4702         unsigned long sz = huge_page_size(h);
4703         unsigned long npages = pages_per_huge_page(h);
4704         struct address_space *mapping = vma->vm_file->f_mapping;
4705         struct mmu_notifier_range range;
4706         int ret = 0;
4707 
4708         if (cow) {
4709                 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, src,
4710                                         vma->vm_start,
4711                                         vma->vm_end);
4712                 mmu_notifier_invalidate_range_start(&range);
4713         } else {
4714                 /*
4715                  * For shared mappings i_mmap_rwsem must be held to call
4716                  * huge_pte_alloc, otherwise the returned ptep could go
4717                  * away if part of a shared pmd and another thread calls
4718                  * huge_pmd_unshare.
4719                  */
4720                 i_mmap_lock_read(mapping);
4721         }
4722 
4723         for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
4724                 spinlock_t *src_ptl, *dst_ptl;
4725                 src_pte = huge_pte_offset(src, addr, sz);
4726                 if (!src_pte)
4727                         continue;
4728                 dst_pte = huge_pte_alloc(dst, vma, addr, sz);
4729                 if (!dst_pte) {
4730                         ret = -ENOMEM;
4731                         break;
4732                 }
4733 
4734                 /*
4735                  * If the pagetables are shared don't copy or take references.
4736                  * dst_pte == src_pte is the common case of src/dest sharing.
4737                  *
4738                  * However, src could have 'unshared' and dst shares with
4739                  * another vma.  If dst_pte !none, this implies sharing.
4740                  * Check here before taking page table lock, and once again
4741                  * after taking the lock below.
4742                  */
4743                 dst_entry = huge_ptep_get(dst_pte);
4744                 if ((dst_pte == src_pte) || !huge_pte_none(dst_entry))
4745                         continue;
4746 
4747                 dst_ptl = huge_pte_lock(h, dst, dst_pte);
4748                 src_ptl = huge_pte_lockptr(h, src, src_pte);
4749                 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
4750                 entry = huge_ptep_get(src_pte);
4751                 dst_entry = huge_ptep_get(dst_pte);
4752 again:
4753                 if (huge_pte_none(entry) || !huge_pte_none(dst_entry)) {
4754                         /*
4755                          * Skip if src entry none.  Also, skip in the
4756                          * unlikely case dst entry !none as this implies
4757                          * sharing with another vma.
4758                          */
4759                         ;
4760                 } else if (unlikely(is_hugetlb_entry_migration(entry) ||
4761                                     is_hugetlb_entry_hwpoisoned(entry))) {
4762                         swp_entry_t swp_entry = pte_to_swp_entry(entry);
4763 
4764                         if (is_writable_migration_entry(swp_entry) && cow) {
4765                                 /*
4766                                  * COW mappings require pages in both
4767                                  * parent and child to be set to read.
4768                                  */
4769                                 swp_entry = make_readable_migration_entry(
4770                                                         swp_offset(swp_entry));
4771                                 entry = swp_entry_to_pte(swp_entry);
4772                                 set_huge_swap_pte_at(src, addr, src_pte,
4773                                                      entry, sz);
4774                         }
4775                         set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz);
4776                 } else {
4777                         entry = huge_ptep_get(src_pte);
4778                         ptepage = pte_page(entry);
4779                         get_page(ptepage);
4780 
4781                         /*
4782                          * This is a rare case where we see pinned hugetlb
4783                          * pages while they're prone to COW.  We need to do the
4784                          * COW earlier during fork.
4785                          *
4786                          * When pre-allocating the page or copying data, we
4787                          * need to be without the pgtable locks since we could
4788                          * sleep during the process.
4789                          */
4790                         if (unlikely(page_needs_cow_for_dma(vma, ptepage))) {
4791                                 pte_t src_pte_old = entry;
4792                                 struct page *new;
4793 
4794                                 spin_unlock(src_ptl);
4795                                 spin_unlock(dst_ptl);
4796                                 /* Do not use reserve as it's private owned */
4797                                 new = alloc_huge_page(vma, addr, 1);
4798                                 if (IS_ERR(new)) {
4799                                         put_page(ptepage);
4800                                         ret = PTR_ERR(new);
4801                                         break;
4802                                 }
4803                                 copy_user_huge_page(new, ptepage, addr, vma,
4804                                                     npages);
4805                                 put_page(ptepage);
4806 
4807                                 /* Install the new huge page if src pte stable */
4808                                 dst_ptl = huge_pte_lock(h, dst, dst_pte);
4809                                 src_ptl = huge_pte_lockptr(h, src, src_pte);
4810                                 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
4811                                 entry = huge_ptep_get(src_pte);
4812                                 if (!pte_same(src_pte_old, entry)) {
4813                                         restore_reserve_on_error(h, vma, addr,
4814                                                                 new);
4815                                         put_page(new);
4816                                         /* dst_entry won't change as in child */
4817                                         goto again;
4818                                 }
4819                                 hugetlb_install_page(vma, dst_pte, addr, new);
4820                                 spin_unlock(src_ptl);
4821                                 spin_unlock(dst_ptl);
4822                                 continue;
4823                         }
4824 
4825                         if (cow) {
4826                                 /*
4827                                  * No need to notify as we are downgrading page
4828                                  * table protection not changing it to point
4829                                  * to a new page.
4830                                  *
4831                                  * See Documentation/vm/mmu_notifier.rst
4832                                  */
4833                                 huge_ptep_set_wrprotect(src, addr, src_pte);
4834                                 entry = huge_pte_wrprotect(entry);
4835                         }
4836 
4837                         page_dup_rmap(ptepage, true);
4838                         set_huge_pte_at(dst, addr, dst_pte, entry);
4839                         hugetlb_count_add(npages, dst);
4840                 }
4841                 spin_unlock(src_ptl);
4842                 spin_unlock(dst_ptl);
4843         }
4844 
4845         if (cow)
4846                 mmu_notifier_invalidate_range_end(&range);
4847         else
4848                 i_mmap_unlock_read(mapping);
4849 
4850         return ret;
4851 }
4852 
4853 static void move_huge_pte(struct vm_area_struct *vma, unsigned long old_addr,
4854                           unsigned long new_addr, pte_t *src_pte)
4855 {
4856         struct hstate *h = hstate_vma(vma);
4857         struct mm_struct *mm = vma->vm_mm;
4858         pte_t *dst_pte, pte;
4859         spinlock_t *src_ptl, *dst_ptl;
4860 
4861         dst_pte = huge_pte_offset(mm, new_addr, huge_page_size(h));
4862         dst_ptl = huge_pte_lock(h, mm, dst_pte);
4863         src_ptl = huge_pte_lockptr(h, mm, src_pte);
4864 
4865         /*
4866          * We don't have to worry about the ordering of src and dst ptlocks
4867          * because exclusive mmap_sem (or the i_mmap_lock) prevents deadlock.
4868          */
4869         if (src_ptl != dst_ptl)
4870                 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
4871 
4872         pte = huge_ptep_get_and_clear(mm, old_addr, src_pte);
4873         set_huge_pte_at(mm, new_addr, dst_pte, pte);
4874 
4875         if (src_ptl != dst_ptl)
4876                 spin_unlock(src_ptl);
4877         spin_unlock(dst_ptl);
4878 }
4879 
4880 int move_hugetlb_page_tables(struct vm_area_struct *vma,
4881                              struct vm_area_struct *new_vma,
4882                              unsigned long old_addr, unsigned long new_addr,
4883                              unsigned long len)
4884 {
4885         struct hstate *h = hstate_vma(vma);
4886         struct address_space *mapping = vma->vm_file->f_mapping;
4887         unsigned long sz = huge_page_size(h);
4888         struct mm_struct *mm = vma->vm_mm;
4889         unsigned long old_end = old_addr + len;
4890         unsigned long old_addr_copy;
4891         pte_t *src_pte, *dst_pte;
4892         struct mmu_notifier_range range;
4893 
4894         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, old_addr,
4895                                 old_end);
4896         adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
4897         mmu_notifier_invalidate_range_start(&range);
4898         /* Prevent race with file truncation */
4899         i_mmap_lock_write(mapping);
4900         for (; old_addr < old_end; old_addr += sz, new_addr += sz) {
4901                 src_pte = huge_pte_offset(mm, old_addr, sz);
4902                 if (!src_pte)
4903                         continue;
4904                 if (huge_pte_none(huge_ptep_get(src_pte)))
4905                         continue;
4906 
4907                 /* old_addr arg to huge_pmd_unshare() is a pointer and so the
4908                  * arg may be modified. Pass a copy instead to preserve the
4909                  * value in old_addr.
4910                  */
4911                 old_addr_copy = old_addr;
4912 
4913                 if (huge_pmd_unshare(mm, vma, &old_addr_copy, src_pte))
4914                         continue;
4915 
4916                 dst_pte = huge_pte_alloc(mm, new_vma, new_addr, sz);
4917                 if (!dst_pte)
4918                         break;
4919 
4920                 move_huge_pte(vma, old_addr, new_addr, src_pte);
4921         }
4922         flush_tlb_range(vma, old_end - len, old_end);
4923         mmu_notifier_invalidate_range_end(&range);
4924         i_mmap_unlock_write(mapping);
4925 
4926         return len + old_addr - old_end;
4927 }
4928 
4929 static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
4930                                    unsigned long start, unsigned long end,
4931                                    struct page *ref_page)
4932 {
4933         struct mm_struct *mm = vma->vm_mm;
4934         unsigned long address;
4935         pte_t *ptep;
4936         pte_t pte;
4937         spinlock_t *ptl;
4938         struct page *page;
4939         struct hstate *h = hstate_vma(vma);
4940         unsigned long sz = huge_page_size(h);
4941         struct mmu_notifier_range range;
4942         bool force_flush = false;
4943 
4944         WARN_ON(!is_vm_hugetlb_page(vma));
4945         BUG_ON(start & ~huge_page_mask(h));
4946         BUG_ON(end & ~huge_page_mask(h));
4947 
4948         /*
4949          * This is a hugetlb vma, all the pte entries should point
4950          * to huge page.
4951          */
4952         tlb_change_page_size(tlb, sz);
4953         tlb_start_vma(tlb, vma);
4954 
4955         /*
4956          * If sharing possible, alert mmu notifiers of worst case.
4957          */
4958         mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, mm, start,
4959                                 end);
4960         adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
4961         mmu_notifier_invalidate_range_start(&range);
4962         address = start;
4963         for (; address < end; address += sz) {
4964                 ptep = huge_pte_offset(mm, address, sz);
4965                 if (!ptep)
4966                         continue;
4967 
4968                 ptl = huge_pte_lock(h, mm, ptep);
4969                 if (huge_pmd_unshare(mm, vma, &address, ptep)) {
4970                         spin_unlock(ptl);
4971                         tlb_flush_pmd_range(tlb, address & PUD_MASK, PUD_SIZE);
4972                         force_flush = true;
4973                         continue;
4974                 }
4975 
4976                 pte = huge_ptep_get(ptep);
4977                 if (huge_pte_none(pte)) {
4978                         spin_unlock(ptl);
4979                         continue;
4980                 }
4981 
4982                 /*
4983                  * Migrating hugepage or HWPoisoned hugepage is already
4984                  * unmapped and its refcount is dropped, so just clear pte here.
4985                  */
4986                 if (unlikely(!pte_present(pte))) {
4987                         huge_pte_clear(mm, address, ptep, sz);
4988                         spin_unlock(ptl);
4989                         continue;
4990                 }
4991 
4992                 page = pte_page(pte);
4993                 /*
4994                  * If a reference page is supplied, it is because a specific
4995                  * page is being unmapped, not a range. Ensure the page we
4996                  * are about to unmap is the actual page of interest.
4997                  */
4998                 if (ref_page) {
4999                         if (page != ref_page) {
5000                                 spin_unlock(ptl);
5001                                 continue;
5002                         }
5003                         /*
5004                          * Mark the VMA as having unmapped its page so that
5005                          * future faults in this VMA will fail rather than
5006                          * looking like data was lost
5007                          */
5008                         set_vma_resv_flags(vma, HPAGE_RESV_UNMAPPED);
5009                 }
5010 
5011                 pte = huge_ptep_get_and_clear(mm, address, ptep);
5012                 tlb_remove_huge_tlb_entry(h, tlb, ptep, address);
5013                 if (huge_pte_dirty(pte))
5014                         set_page_dirty(page);
5015 
5016                 hugetlb_count_sub(pages_per_huge_page(h), mm);
5017                 page_remove_rmap(page, true);
5018 
5019                 spin_unlock(ptl);
5020                 tlb_remove_page_size(tlb, page, huge_page_size(h));
5021                 /*
5022                  * Bail out after unmapping reference page if supplied
5023                  */
5024                 if (ref_page)
5025                         break;
5026         }
5027         mmu_notifier_invalidate_range_end(&range);
5028         tlb_end_vma(tlb, vma);
5029 
5030         /*
5031          * If we unshared PMDs, the TLB flush was not recorded in mmu_gather. We
5032          * could defer the flush until now, since by holding i_mmap_rwsem we
5033          * guaranteed that the last refernece would not be dropped. But we must
5034          * do the flushing before we return, as otherwise i_mmap_rwsem will be
5035          * dropped and the last reference to the shared PMDs page might be
5036          * dropped as well.
5037          *
5038          * In theory we could defer the freeing of the PMD pages as well, but
5039          * huge_pmd_unshare() relies on the exact page_count for the PMD page to
5040          * detect sharing, so we cannot defer the release of the page either.
5041          * Instead, do flush now.
5042          */
5043         if (force_flush)
5044                 tlb_flush_mmu_tlbonly(tlb);
5045 }
5046 
5047 void __unmap_hugepage_range_final(struct mmu_gather *tlb,
5048                           struct vm_area_struct *vma, unsigned long start,
5049                           unsigned long end, struct page *ref_page)
5050 {
5051         __unmap_hugepage_range(tlb, vma, start, end, ref_page);
5052 
5053         /*
5054          * Clear this flag so that x86's huge_pmd_share page_table_shareable
5055          * test will fail on a vma being torn down, and not grab a page table
5056          * on its way out.  We're lucky that the flag has such an appropriate
5057          * name, and can in fact be safely cleared here. We could clear it
5058          * before the __unmap_hugepage_range above, but all that's necessary
5059          * is to clear it before releasing the i_mmap_rwsem. This works
5060          * because in the context this is called, the VMA is about to be
5061          * destroyed and the i_mmap_rwsem is held.
5062          */
5063         vma->vm_flags &= ~VM_MAYSHARE;
5064 }
5065 
5066 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
5067                           unsigned long end, struct page *ref_page)
5068 {
5069         struct mmu_gather tlb;
5070 
5071         tlb_gather_mmu(&tlb, vma->vm_mm);
5072         __unmap_hugepage_range(&tlb, vma, start, end, ref_page);
5073         tlb_finish_mmu(&tlb);
5074 }
5075 
5076 /*
5077  * This is called when the original mapper is failing to COW a MAP_PRIVATE
5078  * mapping it owns the reserve page for. The intention is to unmap the page
5079  * from other VMAs and let the children be SIGKILLed if they are faulting the
5080  * same region.
5081  */
5082 static void unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
5083                               struct page *page, unsigned long address)
5084 {
5085         struct hstate *h = hstate_vma(vma);
5086         struct vm_area_struct *iter_vma;
5087         struct address_space *mapping;
5088         pgoff_t pgoff;
5089 
5090         /*
5091          * vm_pgoff is in PAGE_SIZE units, hence the different calculation
5092          * from page cache lookup which is in HPAGE_SIZE units.
5093          */
5094         address = address & huge_page_mask(h);
5095         pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) +
5096                         vma->vm_pgoff;
5097         mapping = vma->vm_file->f_mapping;
5098 
5099         /*
5100          * Take the mapping lock for the duration of the table walk. As
5101          * this mapping should be shared between all the VMAs,
5102          * __unmap_hugepage_range() is called as the lock is already held
5103          */
5104         i_mmap_lock_write(mapping);
5105         vma_interval_tree_foreach(iter_vma, &mapping->i_mmap, pgoff, pgoff) {
5106                 /* Do not unmap the current VMA */
5107                 if (iter_vma == vma)
5108                         continue;
5109 
5110                 /*
5111                  * Shared VMAs have their own reserves and do not affect
5112                  * MAP_PRIVATE accounting but it is possible that a shared
5113                  * VMA is using the same page so check and skip such VMAs.
5114                  */
5115                 if (iter_vma->vm_flags & VM_MAYSHARE)
5116                         continue;
5117 
5118                 /*
5119                  * Unmap the page from other VMAs without their own reserves.
5120                  * They get marked to be SIGKILLed if they fault in these
5121                  * areas. This is because a future no-page fault on this VMA
5122                  * could insert a zeroed page instead of the data existing
5123                  * from the time of fork. This would look like data corruption
5124                  */
5125                 if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER))
5126                         unmap_hugepage_range(iter_vma, address,
5127                                              address + huge_page_size(h), page);
5128         }
5129         i_mmap_unlock_write(mapping);
5130 }
5131 
5132 /*
5133  * Hugetlb_cow() should be called with page lock of the original hugepage held.
5134  * Called with hugetlb_fault_mutex_table held and pte_page locked so we
5135  * cannot race with other handlers or page migration.
5136  * Keep the pte_same checks anyway to make transition from the mutex easier.
5137  */
5138 static vm_fault_t hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
5139                        unsigned long address, pte_t *ptep,
5140                        struct page *pagecache_page, spinlock_t *ptl)
5141 {
5142         pte_t pte;
5143         struct hstate *h = hstate_vma(vma);
5144         struct page *old_page, *new_page;
5145         int outside_reserve = 0;
5146         vm_fault_t ret = 0;
5147         unsigned long haddr = address & huge_page_mask(h);
5148         struct mmu_notifier_range range;
5149 
5150         pte = huge_ptep_get(ptep);
5151         old_page = pte_page(pte);
5152 
5153 retry_avoidcopy:
5154         /* If no-one else is actually using this page, avoid the copy
5155          * and just make the page writable */
5156         if (page_mapcount(old_page) == 1 && PageAnon(old_page)) {
5157                 page_move_anon_rmap(old_page, vma);
5158                 set_huge_ptep_writable(vma, haddr, ptep);
5159                 return 0;
5160         }
5161 
5162         /*
5163          * If the process that created a MAP_PRIVATE mapping is about to
5164          * perform a COW due to a shared page count, attempt to satisfy
5165          * the allocation without using the existing reserves. The pagecache
5166          * page is used to determine if the reserve at this address was
5167          * consumed or not. If reserves were used, a partial faulted mapping
5168          * at the time of fork() could consume its reserves on COW instead
5169          * of the full address range.
5170          */
5171         if (is_vma_resv_set(vma, HPAGE_RESV_OWNER) &&
5172                         old_page != pagecache_page)
5173                 outside_reserve = 1;
5174 
5175         get_page(old_page);
5176 
5177         /*
5178          * Drop page table lock as buddy allocator may be called. It will
5179          * be acquired again before returning to the caller, as expected.
5180          */
5181         spin_unlock(ptl);
5182         new_page = alloc_huge_page(vma, haddr, outside_reserve);
5183 
5184         if (IS_ERR(new_page)) {
5185                 /*
5186                  * If a process owning a MAP_PRIVATE mapping fails to COW,
5187                  * it is due to references held by a child and an insufficient
5188                  * huge page pool. To guarantee the original mappers
5189                  * reliability, unmap the page from child processes. The child
5190                  * may get SIGKILLed if it later faults.
5191                  */
5192                 if (outside_reserve) {
5193                         struct address_space *mapping = vma->vm_file->f_mapping;
5194                         pgoff_t idx;
5195                         u32 hash;
5196 
5197                         put_page(old_page);
5198                         BUG_ON(huge_pte_none(pte));
5199                         /*
5200                          * Drop hugetlb_fault_mutex and i_mmap_rwsem before
5201                          * unmapping.  unmapping needs to hold i_mmap_rwsem
5202                          * in write mode.  Dropping i_mmap_rwsem in read mode
5203                          * here is OK as COW mappings do not interact with
5204                          * PMD sharing.
5205                          *
5206                          * Reacquire both after unmap operation.
5207                          */
5208                         idx = vma_hugecache_offset(h, vma, haddr);
5209                         hash = hugetlb_fault_mutex_hash(mapping, idx);
5210                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
5211                         i_mmap_unlock_read(mapping);
5212 
5213                         unmap_ref_private(mm, vma, old_page, haddr);
5214 
5215                         i_mmap_lock_read(mapping);
5216                         mutex_lock(&hugetlb_fault_mutex_table[hash]);
5217                         spin_lock(ptl);
5218                         ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
5219                         if (likely(ptep &&
5220                                    pte_same(huge_ptep_get(ptep), pte)))
5221                                 goto retry_avoidcopy;
5222                         /*
5223                          * race occurs while re-acquiring page table
5224                          * lock, and our job is done.
5225                          */
5226                         return 0;
5227                 }
5228 
5229                 ret = vmf_error(PTR_ERR(new_page));
5230                 goto out_release_old;
5231         }
5232 
5233         /*
5234          * When the original hugepage is shared one, it does not have
5235          * anon_vma prepared.
5236          */
5237         if (unlikely(anon_vma_prepare(vma))) {
5238                 ret = VM_FAULT_OOM;
5239                 goto out_release_all;
5240         }
5241 
5242         copy_user_huge_page(new_page, old_page, address, vma,
5243                             pages_per_huge_page(h));
5244         __SetPageUptodate(new_page);
5245 
5246         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, haddr,
5247                                 haddr + huge_page_size(h));
5248         mmu_notifier_invalidate_range_start(&range);
5249 
5250         /*
5251          * Retake the page table lock to check for racing updates
5252          * before the page tables are altered
5253          */
5254         spin_lock(ptl);
5255         ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
5256         if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
5257                 ClearHPageRestoreReserve(new_page);
5258 
5259                 /* Break COW */
5260                 huge_ptep_clear_flush(vma, haddr, ptep);
5261                 mmu_notifier_invalidate_range(mm, range.start, range.end);
5262                 set_huge_pte_at(mm, haddr, ptep,
5263                                 make_huge_pte(vma, new_page, 1));
5264                 page_remove_rmap(old_page, true);
5265                 hugepage_add_new_anon_rmap(new_page, vma, haddr);
5266                 SetHPageMigratable(new_page);
5267                 /* Make the old page be freed below */
5268                 new_page = old_page;
5269         }
5270         spin_unlock(ptl);
5271         mmu_notifier_invalidate_range_end(&range);
5272 out_release_all:
5273         /* No restore in case of successful pagetable update (Break COW) */
5274         if (new_page != old_page)
5275                 restore_reserve_on_error(h, vma, haddr, new_page);
5276         put_page(new_page);
5277 out_release_old:
5278         put_page(old_page);
5279 
5280         spin_lock(ptl); /* Caller expects lock to be held */
5281         return ret;
5282 }
5283 
5284 /* Return the pagecache page at a given address within a VMA */
5285 static struct page *hugetlbfs_pagecache_page(struct hstate *h,
5286                         struct vm_area_struct *vma, unsigned long address)
5287 {
5288         struct address_space *mapping;
5289         pgoff_t idx;
5290 
5291         mapping = vma->vm_file->f_mapping;
5292         idx = vma_hugecache_offset(h, vma, address);
5293 
5294         return find_lock_page(mapping, idx);
5295 }
5296 
5297 /*
5298  * Return whether there is a pagecache page to back given address within VMA.
5299  * Caller follow_hugetlb_page() holds page_table_lock so we cannot lock_page.
5300  */
5301 static bool hugetlbfs_pagecache_present(struct hstate *h,
5302                         struct vm_area_struct *vma, unsigned long address)
5303 {
5304         struct address_space *mapping;
5305         pgoff_t idx;
5306         struct page *page;
5307 
5308         mapping = vma->vm_file->f_mapping;
5309         idx = vma_hugecache_offset(h, vma, address);
5310 
5311         page = find_get_page(mapping, idx);
5312         if (page)
5313                 put_page(page);
5314         return page != NULL;
5315 }
5316 
5317 int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
5318                            pgoff_t idx)
5319 {
5320         struct inode *inode = mapping->host;
5321         struct hstate *h = hstate_inode(inode);
5322         int err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
5323 
5324         if (err)
5325                 return err;
5326         ClearHPageRestoreReserve(page);
5327 
5328         /*
5329          * set page dirty so that it will not be removed from cache/file
5330          * by non-hugetlbfs specific code paths.
5331          */
5332         set_page_dirty(page);
5333 
5334         spin_lock(&inode->i_lock);
5335         inode->i_blocks += blocks_per_huge_page(h);
5336         spin_unlock(&inode->i_lock);
5337         return 0;
5338 }
5339 
5340 static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma,
5341                                                   struct address_space *mapping,
5342                                                   pgoff_t idx,
5343                                                   unsigned int flags,
5344                                                   unsigned long haddr,
5345                                                   unsigned long reason)
5346 {
5347         vm_fault_t ret;
5348         u32 hash;
5349         struct vm_fault vmf = {
5350                 .vma = vma,
5351                 .address = haddr,
5352                 .flags = flags,
5353 
5354                 /*
5355                  * Hard to debug if it ends up being
5356                  * used by a callee that assumes
5357                  * something about the other
5358                  * uninitialized fields... same as in
5359                  * memory.c
5360                  */
5361         };
5362 
5363         /*
5364          * hugetlb_fault_mutex and i_mmap_rwsem must be
5365          * dropped before handling userfault.  Reacquire
5366          * after handling fault to make calling code simpler.
5367          */
5368         hash = hugetlb_fault_mutex_hash(mapping, idx);
5369         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
5370         i_mmap_unlock_read(mapping);
5371         ret = handle_userfault(&vmf, reason);
5372         i_mmap_lock_read(mapping);
5373         mutex_lock(&hugetlb_fault_mutex_table[hash]);
5374 
5375         return ret;
5376 }
5377 
5378 static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
5379                         struct vm_area_struct *vma,
5380                         struct address_space *mapping, pgoff_t idx,
5381                         unsigned long address, pte_t *ptep, unsigned int flags)
5382 {
5383         struct hstate *h = hstate_vma(vma);
5384         vm_fault_t ret = VM_FAULT_SIGBUS;
5385         int anon_rmap = 0;
5386         unsigned long size;
5387         struct page *page;
5388         pte_t new_pte;
5389         spinlock_t *ptl;
5390         unsigned long haddr = address & huge_page_mask(h);
5391         bool new_page, new_pagecache_page = false;
5392 
5393         /*
5394          * Currently, we are forced to kill the process in the event the
5395          * original mapper has unmapped pages from the child due to a failed
5396          * COW. Warn that such a situation has occurred as it may not be obvious
5397          */
5398         if (is_vma_resv_set(vma, HPAGE_RESV_UNMAPPED)) {
5399                 pr_warn_ratelimited("PID %d killed due to inadequate hugepage pool\n",
5400                            current->pid);
5401                 return ret;
5402         }
5403 
5404         /*
5405          * We can not race with truncation due to holding i_mmap_rwsem.
5406          * i_size is modified when holding i_mmap_rwsem, so check here
5407          * once for faults beyond end of file.
5408          */
5409         size = i_size_read(mapping->host) >> huge_page_shift(h);
5410         if (idx >= size)
5411                 goto out;
5412 
5413 retry:
5414         new_page = false;
5415         page = find_lock_page(mapping, idx);
5416         if (!page) {
5417                 /* Check for page in userfault range */
5418                 if (userfaultfd_missing(vma)) {
5419                         ret = hugetlb_handle_userfault(vma, mapping, idx,
5420                                                        flags, haddr,
5421                                                        VM_UFFD_MISSING);
5422                         goto out;
5423                 }
5424 
5425                 page = alloc_huge_page(vma, haddr, 0);
5426                 if (IS_ERR(page)) {
5427                         /*
5428                          * Returning error will result in faulting task being
5429                          * sent SIGBUS.  The hugetlb fault mutex prevents two
5430                          * tasks from racing to fault in the same page which
5431                          * could result in false unable to allocate errors.
5432                          * Page migration does not take the fault mutex, but
5433                          * does a clear then write of pte's under page table
5434                          * lock.  Page fault code could race with migration,
5435                          * notice the clear pte and try to allocate a page
5436                          * here.  Before returning error, get ptl and make
5437                          * sure there really is no pte entry.
5438                          */
5439                         ptl = huge_pte_lock(h, mm, ptep);
5440                         ret = 0;
5441                         if (huge_pte_none(huge_ptep_get(ptep)))
5442                                 ret = vmf_error(PTR_ERR(page));
5443                         spin_unlock(ptl);
5444                         goto out;
5445                 }
5446                 clear_huge_page(page, address, pages_per_huge_page(h));
5447                 __SetPageUptodate(page);
5448                 new_page = true;
5449 
5450                 if (vma->vm_flags & VM_MAYSHARE) {
5451                         int err = huge_add_to_page_cache(page, mapping, idx);
5452                         if (err) {
5453                                 put_page(page);
5454                                 if (err == -EEXIST)
5455                                         goto retry;
5456                                 goto out;
5457                         }
5458                         new_pagecache_page = true;
5459                 } else {
5460                         lock_page(page);
5461                         if (unlikely(anon_vma_prepare(vma))) {
5462                                 ret = VM_FAULT_OOM;
5463                                 goto backout_unlocked;
5464                         }
5465                         anon_rmap = 1;
5466                 }
5467         } else {
5468                 /*
5469                  * If memory error occurs between mmap() and fault, some process
5470                  * don't have hwpoisoned swap entry for errored virtual address.
5471                  * So we need to block hugepage fault by PG_hwpoison bit check.
5472                  */
5473                 if (unlikely(PageHWPoison(page))) {
5474                         ret = VM_FAULT_HWPOISON_LARGE |
5475                                 VM_FAULT_SET_HINDEX(hstate_index(h));
5476                         goto backout_unlocked;
5477                 }
5478 
5479                 /* Check for page in userfault range. */
5480                 if (userfaultfd_minor(vma)) {
5481                         unlock_page(page);
5482                         put_page(page);
5483                         ret = hugetlb_handle_userfault(vma, mapping, idx,
5484                                                        flags, haddr,
5485                                                        VM_UFFD_MINOR);
5486                         goto out;
5487                 }
5488         }
5489 
5490         /*
5491          * If we are going to COW a private mapping later, we examine the
5492          * pending reservations for this page now. This will ensure that
5493          * any allocations necessary to record that reservation occur outside
5494          * the spinlock.
5495          */
5496         if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
5497                 if (vma_needs_reservation(h, vma, haddr) < 0) {
5498                         ret = VM_FAULT_OOM;
5499                         goto backout_unlocked;
5500                 }
5501                 /* Just decrements count, does not deallocate */
5502                 vma_end_reservation(h, vma, haddr);
5503         }
5504 
5505         ptl = huge_pte_lock(h, mm, ptep);
5506         ret = 0;
5507         if (!huge_pte_none(huge_ptep_get(ptep)))
5508                 goto backout;
5509 
5510         if (anon_rmap) {
5511                 ClearHPageRestoreReserve(page);
5512                 hugepage_add_new_anon_rmap(page, vma, haddr);
5513         } else
5514                 page_dup_rmap(page, true);
5515         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
5516                                 && (vma->vm_flags & VM_SHARED)));
5517         set_huge_pte_at(mm, haddr, ptep, new_pte);
5518 
5519         hugetlb_count_add(pages_per_huge_page(h), mm);
5520         if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
5521                 /* Optimization, do the COW without a second fault */
5522                 ret = hugetlb_cow(mm, vma, address, ptep, page, ptl);
5523         }
5524 
5525         spin_unlock(ptl);
5526 
5527         /*
5528          * Only set HPageMigratable in newly allocated pages.  Existing pages
5529          * found in the pagecache may not have HPageMigratableset if they have
5530          * been isolated for migration.
5531          */
5532         if (new_page)
5533                 SetHPageMigratable(page);
5534 
5535         unlock_page(page);
5536 out:
5537         return ret;
5538 
5539 backout:
5540         spin_unlock(ptl);
5541 backout_unlocked:
5542         unlock_page(page);
5543         /* restore reserve for newly allocated pages not in page cache */
5544         if (new_page && !new_pagecache_page)
5545                 restore_reserve_on_error(h, vma, haddr, page);
5546         put_page(page);
5547         goto out;
5548 }
5549 
5550 #ifdef CONFIG_SMP
5551 u32 hugetlb_fault_mutex_hash(struct address_space *mapping, pgoff_t idx)
5552 {
5553         unsigned long key[2];
5554         u32 hash;
5555 
5556         key[0] = (unsigned long) mapping;
5557         key[1] = idx;
5558 
5559         hash = jhash2((u32 *)&key, sizeof(key)/(sizeof(u32)), 0);
5560 
5561         return hash & (num_fault_mutexes - 1);
5562 }
5563 #else
5564 /*
5565  * For uniprocessor systems we always use a single mutex, so just
5566  * return 0 and avoid the hashing overhead.
5567  */
5568 u32 hugetlb_fault_mutex_hash(struct address_space *mapping, pgoff_t idx)
5569 {
5570         return 0;
5571 }
5572 #endif
5573 
5574 vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
5575                         unsigned long address, unsigned int flags)
5576 {
5577         pte_t *ptep, entry;
5578         spinlock_t *ptl;
5579         vm_fault_t ret;
5580         u32 hash;
5581         pgoff_t idx;
5582         struct page *page = NULL;
5583         struct page *pagecache_page = NULL;
5584         struct hstate *h = hstate_vma(vma);
5585         struct address_space *mapping;
5586         int need_wait_lock = 0;
5587         unsigned long haddr = address & huge_page_mask(h);
5588 
5589         ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
5590         if (ptep) {
5591                 /*
5592                  * Since we hold no locks, ptep could be stale.  That is
5593                  * OK as we are only making decisions based on content and
5594                  * not actually modifying content here.
5595                  */
5596                 entry = huge_ptep_get(ptep);
5597                 if (unlikely(is_hugetlb_entry_migration(entry))) {
5598                         migration_entry_wait_huge(vma, mm, ptep);
5599                         return 0;
5600                 } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
5601                         return VM_FAULT_HWPOISON_LARGE |
5602                                 VM_FAULT_SET_HINDEX(hstate_index(h));
5603         }
5604 
5605         /*
5606          * Acquire i_mmap_rwsem before calling huge_pte_alloc and hold
5607          * until finished with ptep.  This serves two purposes:
5608          * 1) It prevents huge_pmd_unshare from being called elsewhere
5609          *    and making the ptep no longer valid.
5610          * 2) It synchronizes us with i_size modifications during truncation.
5611          *
5612          * ptep could have already be assigned via huge_pte_offset.  That
5613          * is OK, as huge_pte_alloc will return the same value unless
5614          * something has changed.
5615          */
5616         mapping = vma->vm_file->f_mapping;
5617         i_mmap_lock_read(mapping);
5618         ptep = huge_pte_alloc(mm, vma, haddr, huge_page_size(h));
5619         if (!ptep) {
5620                 i_mmap_unlock_read(mapping);
5621                 return VM_FAULT_OOM;
5622         }
5623 
5624         /*
5625          * Serialize hugepage allocation and instantiation, so that we don't
5626          * get spurious allocation failures if two CPUs race to instantiate
5627          * the same page in the page cache.
5628          */
5629         idx = vma_hugecache_offset(h, vma, haddr);
5630         hash = hugetlb_fault_mutex_hash(mapping, idx);
5631         mutex_lock(&hugetlb_fault_mutex_table[hash]);
5632 
5633         entry = huge_ptep_get(ptep);
5634         if (huge_pte_none(entry)) {
5635                 ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, flags);
5636                 goto out_mutex;
5637         }
5638 
5639         ret = 0;
5640 
5641         /*
5642          * entry could be a migration/hwpoison entry at this point, so this
5643          * check prevents the kernel from going below assuming that we have
5644          * an active hugepage in pagecache. This goto expects the 2nd page
5645          * fault, and is_hugetlb_entry_(migration|hwpoisoned) check will
5646          * properly handle it.
5647          */
5648         if (!pte_present(entry))
5649                 goto out_mutex;
5650 
5651         /*
5652          * If we are going to COW the mapping later, we examine the pending
5653          * reservations for this page now. This will ensure that any
5654          * allocations necessary to record that reservation occur outside the
5655          * spinlock. For private mappings, we also lookup the pagecache
5656          * page now as it is used to determine if a reservation has been
5657          * consumed.
5658          */
5659         if ((flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
5660                 if (vma_needs_reservation(h, vma, haddr) < 0) {
5661                         ret = VM_FAULT_OOM;
5662                         goto out_mutex;
5663                 }
5664                 /* Just decrements count, does not deallocate */
5665                 vma_end_reservation(h, vma, haddr);
5666 
5667                 if (!(vma->vm_flags & VM_MAYSHARE))
5668                         pagecache_page = hugetlbfs_pagecache_page(h,
5669                                                                 vma, haddr);
5670         }
5671 
5672         ptl = huge_pte_lock(h, mm, ptep);
5673 
5674         /* Check for a racing update before calling hugetlb_cow */
5675         if (unlikely(!pte_same(entry, huge_ptep_get(ptep))))
5676                 goto out_ptl;
5677 
5678         /*
5679          * hugetlb_cow() requires page locks of pte_page(entry) and
5680          * pagecache_page, so here we need take the former one
5681          * when page != pagecache_page or !pagecache_page.
5682          */
5683         page = pte_page(entry);
5684         if (page != pagecache_page)
5685                 if (!trylock_page(page)) {
5686                         need_wait_lock = 1;
5687                         goto out_ptl;
5688                 }
5689 
5690         get_page(page);
5691 
5692         if (flags & FAULT_FLAG_WRITE) {
5693                 if (!huge_pte_write(entry)) {
5694                         ret = hugetlb_cow(mm, vma, address, ptep,
5695                                           pagecache_page, ptl);
5696                         goto out_put_page;
5697                 }
5698                 entry = huge_pte_mkdirty(entry);
5699         }
5700         entry = pte_mkyoung(entry);
5701         if (huge_ptep_set_access_flags(vma, haddr, ptep, entry,
5702                                                 flags & FAULT_FLAG_WRITE))
5703                 update_mmu_cache(vma, haddr, ptep);
5704 out_put_page:
5705         if (page != pagecache_page)
5706                 unlock_page(page);
5707         put_page(page);
5708 out_ptl:
5709         spin_unlock(ptl);
5710 
5711         if (pagecache_page) {
5712                 unlock_page(pagecache_page);
5713                 put_page(pagecache_page);
5714         }
5715 out_mutex:
5716         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
5717         i_mmap_unlock_read(mapping);
5718         /*
5719          * Generally it's safe to hold refcount during waiting page lock. But
5720          * here we just wait to defer the next page fault to avoid busy loop and
5721          * the page is not used after unlocked before returning from the current
5722          * page fault. So we are safe from accessing freed page, even if we wait
5723          * here without taking refcount.
5724          */
5725         if (need_wait_lock)
5726                 wait_on_page_locked(page);
5727         return ret;
5728 }
5729 
5730 #ifdef CONFIG_USERFAULTFD
5731 /*
5732  * Used by userfaultfd UFFDIO_COPY.  Based on mcopy_atomic_pte with
5733  * modifications for huge pages.
5734  */
5735 int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
5736                             pte_t *dst_pte,
5737                             struct vm_area_struct *dst_vma,
5738                             unsigned long dst_addr,
5739                             unsigned long src_addr,
5740                             enum mcopy_atomic_mode mode,
5741                             struct page **pagep)
5742 {
5743         bool is_continue = (mode == MCOPY_ATOMIC_CONTINUE);
5744         struct hstate *h = hstate_vma(dst_vma);
5745         struct address_space *mapping = dst_vma->vm_file->f_mapping;
5746         pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
5747         unsigned long size;
5748         int vm_shared = dst_vma->vm_flags & VM_SHARED;
5749         pte_t _dst_pte;
5750         spinlock_t *ptl;
5751         int ret = -ENOMEM;
5752         struct page *page;
5753         int writable;
5754         bool page_in_pagecache = false;
5755 
5756         if (is_continue) {
5757                 ret = -EFAULT;
5758                 page = find_lock_page(mapping, idx);
5759                 if (!page)
5760                         goto out;
5761                 page_in_pagecache = true;
5762         } else if (!*pagep) {
5763                 /* If a page already exists, then it's UFFDIO_COPY for
5764                  * a non-missing case. Return -EEXIST.
5765                  */
5766                 if (vm_shared &&
5767                     hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) {
5768                         ret = -EEXIST;
5769                         goto out;
5770                 }
5771 
5772                 page = alloc_huge_page(dst_vma, dst_addr, 0);
5773                 if (IS_ERR(page)) {
5774                         ret = -ENOMEM;
5775                         goto out;
5776                 }
5777 
5778                 ret = copy_huge_page_from_user(page,
5779                                                 (const void __user *) src_addr,
5780                                                 pages_per_huge_page(h), false);
5781 
5782                 /* fallback to copy_from_user outside mmap_lock */
5783                 if (unlikely(ret)) {
5784                         ret = -ENOENT;
5785                         /* Free the allocated page which may have
5786                          * consumed a reservation.
5787                          */
5788                         restore_reserve_on_error(h, dst_vma, dst_addr, page);
5789                         put_page(page);
5790 
5791                         /* Allocate a temporary page to hold the copied
5792                          * contents.
5793                          */
5794                         page = alloc_huge_page_vma(h, dst_vma, dst_addr);
5795                         if (!page) {
5796                                 ret = -ENOMEM;
5797                                 goto out;
5798                         }
5799                         *pagep = page;
5800                         /* Set the outparam pagep and return to the caller to
5801                          * copy the contents outside the lock. Don't free the
5802                          * page.
5803                          */
5804                         goto out;
5805                 }
5806         } else {
5807                 if (vm_shared &&
5808                     hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) {
5809                         put_page(*pagep);
5810                         ret = -EEXIST;
5811                         *pagep = NULL;
5812                         goto out;
5813                 }
5814 
5815                 page = alloc_huge_page(dst_vma, dst_addr, 0);
5816                 if (IS_ERR(page)) {
5817                         ret = -ENOMEM;
5818                         *pagep = NULL;
5819                         goto out;
5820                 }
5821                 folio_copy(page_folio(page), page_folio(*pagep));
5822                 put_page(*pagep);
5823                 *pagep = NULL;
5824         }
5825 
5826         /*
5827          * The memory barrier inside __SetPageUptodate makes sure that
5828          * preceding stores to the page contents become visible before
5829          * the set_pte_at() write.
5830          */
5831         __SetPageUptodate(page);
5832 
5833         /* Add shared, newly allocated pages to the page cache. */
5834         if (vm_shared && !is_continue) {
5835                 size = i_size_read(mapping->host) >> huge_page_shift(h);
5836                 ret = -EFAULT;
5837                 if (idx >= size)
5838                         goto out_release_nounlock;
5839 
5840                 /*
5841                  * Serialization between remove_inode_hugepages() and
5842                  * huge_add_to_page_cache() below happens through the
5843                  * hugetlb_fault_mutex_table that here must be hold by
5844                  * the caller.
5845                  */
5846                 ret = huge_add_to_page_cache(page, mapping, idx);
5847                 if (ret)
5848                         goto out_release_nounlock;
5849                 page_in_pagecache = true;
5850         }
5851 
5852         ptl = huge_pte_lockptr(h, dst_mm, dst_pte);
5853         spin_lock(ptl);
5854 
5855         /*
5856          * Recheck the i_size after holding PT lock to make sure not
5857          * to leave any page mapped (as page_mapped()) beyond the end
5858          * of the i_size (remove_inode_hugepages() is strict about
5859          * enforcing that). If we bail out here, we'll also leave a
5860          * page in the radix tree in the vm_shared case beyond the end
5861          * of the i_size, but remove_inode_hugepages() will take care
5862          * of it as soon as we drop the hugetlb_fault_mutex_table.
5863          */
5864         size = i_size_read(mapping->host) >> huge_page_shift(h);
5865         ret = -EFAULT;
5866         if (idx >= size)
5867                 goto out_release_unlock;
5868 
5869         ret = -EEXIST;
5870         if (!huge_pte_none(huge_ptep_get(dst_pte)))
5871                 goto out_release_unlock;
5872 
5873         if (vm_shared) {
5874                 page_dup_rmap(page, true);
5875         } else {
5876                 ClearHPageRestoreReserve(page);
5877                 hugepage_add_new_anon_rmap(page, dst_vma, dst_addr);
5878         }
5879 
5880         /* For CONTINUE on a non-shared VMA, don't set VM_WRITE for CoW. */
5881         if (is_continue && !vm_shared)
5882                 writable = 0;
5883         else
5884                 writable = dst_vma->vm_flags & VM_WRITE;
5885 
5886         _dst_pte = make_huge_pte(dst_vma, page, writable);
5887         if (writable)
5888                 _dst_pte = huge_pte_mkdirty(_dst_pte);
5889         _dst_pte = pte_mkyoung(_dst_pte);
5890 
5891         set_huge_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
5892 
5893         (void)huge_ptep_set_access_flags(dst_vma, dst_addr, dst_pte, _dst_pte,
5894                                         dst_vma->vm_flags & VM_WRITE);
5895         hugetlb_count_add(pages_per_huge_page(h), dst_mm);
5896 
5897         /* No need to invalidate - it was non-present before */
5898         update_mmu_cache(dst_vma, dst_addr, dst_pte);
5899 
5900         spin_unlock(ptl);
5901         if (!is_continue)
5902                 SetHPageMigratable(page);
5903         if (vm_shared || is_continue)
5904                 unlock_page(page);
5905         ret = 0;
5906 out:
5907         return ret;
5908 out_release_unlock:
5909         spin_unlock(ptl);
5910         if (vm_shared || is_continue)
5911                 unlock_page(page);
5912 out_release_nounlock:
5913         if (!page_in_pagecache)
5914                 restore_reserve_on_error(h, dst_vma, dst_addr, page);
5915         put_page(page);
5916         goto out;
5917 }
5918 #endif /* CONFIG_USERFAULTFD */
5919 
5920 static void record_subpages_vmas(struct page *page, struct vm_area_struct *vma,
5921                                  int refs, struct page **pages,
5922                                  struct vm_area_struct **vmas)
5923 {
5924         int nr;
5925 
5926         for (nr = 0; nr < refs; nr++) {
5927                 if (likely(pages))
5928                         pages[nr] = mem_map_offset(page, nr);
5929                 if (vmas)
5930                         vmas[nr] = vma;
5931         }
5932 }
5933 
5934 long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
5935                          struct page **pages, struct vm_area_struct **vmas,
5936                          unsigned long *position, unsigned long *nr_pages,
5937                          long i, unsigned int flags, int *locked)
5938 {
5939         unsigned long pfn_offset;
5940         unsigned long vaddr = *position;
5941         unsigned long remainder = *nr_pages;
5942         struct hstate *h = hstate_vma(vma);
5943         int err = -EFAULT, refs;
5944 
5945         while (vaddr < vma->vm_end && remainder) {
5946                 pte_t *pte;
5947                 spinlock_t *ptl = NULL;
5948                 int absent;
5949                 struct page *page;
5950 
5951                 /*
5952                  * If we have a pending SIGKILL, don't keep faulting pages and
5953                  * potentially allocating memory.
5954                  */
5955                 if (fatal_signal_pending(current)) {
5956                         remainder = 0;
5957                         break;
5958                 }
5959 
5960                 /*
5961                  * Some archs (sparc64, sh*) have multiple pte_ts to
5962                  * each hugepage.  We have to make sure we get the
5963                  * first, for the page indexing below to work.
5964                  *
5965                  * Note that page table lock is not held when pte is null.
5966                  */
5967                 pte = huge_pte_offset(mm, vaddr & huge_page_mask(h),
5968                                       huge_page_size(h));
5969                 if (pte)
5970                         ptl = huge_pte_lock(h, mm, pte);
5971                 absent = !pte || huge_pte_none(huge_ptep_get(pte));
5972 
5973                 /*
5974                  * When coredumping, it suits get_dump_page if we just return
5975                  * an error where there's an empty slot with no huge pagecache
5976                  * to back it.  This way, we avoid allocating a hugepage, and
5977                  * the sparse dumpfile avoids allocating disk blocks, but its
5978                  * huge holes still show up with zeroes where they need to be.
5979                  */
5980                 if (absent && (flags & FOLL_DUMP) &&
5981                     !hugetlbfs_pagecache_present(h, vma, vaddr)) {
5982                         if (pte)
5983                                 spin_unlock(ptl);
5984                         remainder = 0;
5985                         break;
5986                 }
5987 
5988                 /*
5989                  * We need call hugetlb_fault for both hugepages under migration
5990                  * (in which case hugetlb_fault waits for the migration,) and
5991                  * hwpoisoned hugepages (in which case we need to prevent the
5992                  * caller from accessing to them.) In order to do this, we use
5993                  * here is_swap_pte instead of is_hugetlb_entry_migration and
5994                  * is_hugetlb_entry_hwpoisoned. This is because it simply covers
5995                  * both cases, and because we can't follow correct pages
5996                  * directly from any kind of swap entries.
5997                  */
5998                 if (absent || is_swap_pte(huge_ptep_get(pte)) ||
5999                     ((flags & FOLL_WRITE) &&
6000                       !huge_pte_write(huge_ptep_get(pte)))) {
6001                         vm_fault_t ret;
6002                         unsigned int fault_flags = 0;
6003 
6004                         if (pte)
6005                                 spin_unlock(ptl);
6006                         if (flags & FOLL_WRITE)
6007                                 fault_flags |= FAULT_FLAG_WRITE;
6008                         if (locked)
6009                                 fault_flags |= FAULT_FLAG_ALLOW_RETRY |
6010                                         FAULT_FLAG_KILLABLE;
6011                         if (flags & FOLL_NOWAIT)
6012                                 fault_flags |= FAULT_FLAG_ALLOW_RETRY |
6013                                         FAULT_FLAG_RETRY_NOWAIT;
6014                         if (flags & FOLL_TRIED) {
6015                                 /*
6016                                  * Note: FAULT_FLAG_ALLOW_RETRY and
6017                                  * FAULT_FLAG_TRIED can co-exist
6018                                  */
6019                                 fault_flags |= FAULT_FLAG_TRIED;
6020                         }
6021                         ret = hugetlb_fault(mm, vma, vaddr, fault_flags);
6022                         if (ret & VM_FAULT_ERROR) {
6023                                 err = vm_fault_to_errno(ret, flags);
6024                                 remainder = 0;
6025                                 break;
6026                         }
6027                         if (ret & VM_FAULT_RETRY) {
6028                                 if (locked &&
6029                                     !(fault_flags & FAULT_FLAG_RETRY_NOWAIT))
6030                                         *locked = 0;
6031                                 *nr_pages = 0;
6032                                 /*
6033                                  * VM_FAULT_RETRY must not return an
6034                                  * error, it will return zero
6035                                  * instead.
6036                                  *
6037                                  * No need to update "position" as the
6038                                  * caller will not check it after
6039                                  * *nr_pages is set to 0.
6040                                  */
6041                                 return i;
6042                         }
6043                         continue;
6044                 }
6045 
6046                 pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT;
6047                 page = pte_page(huge_ptep_get(pte));
6048 
6049                 /*
6050                  * If subpage information not requested, update counters
6051                  * and skip the same_page loop below.
6052                  */
6053                 if (!pages && !vmas && !pfn_offset &&
6054                     (vaddr + huge_page_size(h) < vma->vm_end) &&
6055                     (remainder >= pages_per_huge_page(h))) {
6056                         vaddr += huge_page_size(h);
6057                         remainder -= pages_per_huge_page(h);
6058                         i += pages_per_huge_page(h);
6059                         spin_unlock(ptl);
6060                         continue;
6061                 }
6062 
6063                 /* vaddr may not be aligned to PAGE_SIZE */
6064                 refs = min3(pages_per_huge_page(h) - pfn_offset, remainder,
6065                     (vma->vm_end - ALIGN_DOWN(vaddr, PAGE_SIZE)) >> PAGE_SHIFT);
6066 
6067                 if (pages || vmas)
6068                         record_subpages_vmas(mem_map_offset(page, pfn_offset),
6069                                              vma, refs,
6070                                              likely(pages) ? pages + i : NULL,
6071                                              vmas ? vmas + i : NULL);
6072 
6073                 if (pages) {
6074                         /*
6075                          * try_grab_compound_head() should always succeed here,
6076                          * because: a) we hold the ptl lock, and b) we've just
6077                          * checked that the huge page is present in the page
6078                          * tables. If the huge page is present, then the tail
6079                          * pages must also be present. The ptl prevents the
6080                          * head page and tail pages from being rearranged in
6081                          * any way. So this page must be available at this
6082                          * point, unless the page refcount overflowed:
6083                          */
6084                         if (WARN_ON_ONCE(!try_grab_compound_head(pages[i],
6085                                                                  refs,
6086                                                                  flags))) {
6087                                 spin_unlock(ptl);
6088                                 remainder = 0;
6089                                 err = -ENOMEM;
6090                                 break;
6091                         }
6092                 }
6093 
6094                 vaddr += (refs << PAGE_SHIFT);
6095                 remainder -= refs;
6096                 i += refs;
6097 
6098                 spin_unlock(ptl);
6099         }
6100         *nr_pages = remainder;
6101         /*
6102          * setting position is actually required only if remainder is
6103          * not zero but it's faster not to add a "if (remainder)"
6104          * branch.
6105          */
6106         *position = vaddr;
6107 
6108         return i ? i : err;
6109 }
6110 
6111 unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
6112                 unsigned long address, unsigned long end, pgprot_t newprot)
6113 {
6114         struct mm_struct *mm = vma->vm_mm;
6115         unsigned long start = address;
6116         pte_t *ptep;
6117         pte_t pte;
6118         struct hstate *h = hstate_vma(vma);
6119         unsigned long pages = 0;
6120         bool shared_pmd = false;
6121         struct mmu_notifier_range range;
6122 
6123         /*
6124          * In the case of shared PMDs, the area to flush could be beyond
6125          * start/end.  Set range.start/range.end to cover the maximum possible
6126          * range if PMD sharing is possible.
6127          */
6128         mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA,
6129                                 0, vma, mm, start, end);
6130         adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end);
6131 
6132         BUG_ON(address >= end);
6133         flush_cache_range(vma, range.start, range.end);
6134 
6135         mmu_notifier_invalidate_range_start(&range);
6136         i_mmap_lock_write(vma->vm_file->f_mapping);
6137         for (; address < end; address += huge_page_size(h)) {
6138                 spinlock_t *ptl;
6139                 ptep = huge_pte_offset(mm, address, huge_page_size(h));
6140                 if (!ptep)
6141                         continue;
6142                 ptl = huge_pte_lock(h, mm, ptep);
6143                 if (huge_pmd_unshare(mm, vma, &address, ptep)) {
6144                         pages++;
6145                         spin_unlock(ptl);
6146                         shared_pmd = true;
6147                         continue;
6148                 }
6149                 pte = huge_ptep_get(ptep);
6150                 if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
6151                         spin_unlock(ptl);
6152                         continue;
6153                 }
6154                 if (unlikely(is_hugetlb_entry_migration(pte))) {
6155                         swp_entry_t entry = pte_to_swp_entry(pte);
6156 
6157                         if (is_writable_migration_entry(entry)) {
6158                                 pte_t newpte;
6159 
6160                                 entry = make_readable_migration_entry(
6161                                                         swp_offset(entry));
6162                                 newpte = swp_entry_to_pte(entry);
6163                                 set_huge_swap_pte_at(mm, address, ptep,
6164                                                      newpte, huge_page_size(h));
6165                                 pages++;
6166                         }
6167                         spin_unlock(ptl);
6168                         continue;
6169                 }
6170                 if (!huge_pte_none(pte)) {
6171                         pte_t old_pte;
6172                         unsigned int shift = huge_page_shift(hstate_vma(vma));
6173 
6174                         old_pte = huge_ptep_modify_prot_start(vma, address, ptep);
6175                         pte = pte_mkhuge(huge_pte_modify(old_pte, newprot));
6176                         pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
6177                         huge_ptep_modify_prot_commit(vma, address, ptep, old_pte, pte);
6178                         pages++;
6179                 }
6180                 spin_unlock(ptl);
6181         }
6182         /*
6183          * Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare
6184          * may have cleared our pud entry and done put_page on the page table:
6185          * once we release i_mmap_rwsem, another task can do the final put_page
6186          * and that page table be reused and filled with junk.  If we actually
6187          * did unshare a page of pmds, flush the range corresponding to the pud.
6188          */
6189         if (shared_pmd)
6190                 flush_hugetlb_tlb_range(vma, range.start, range.end);
6191         else
6192                 flush_hugetlb_tlb_range(vma, start, end);
6193         /*
6194          * No need to call mmu_notifier_invalidate_range() we are downgrading
6195          * page table protection not changing it to point to a new page.
6196          *
6197          * See Documentation/vm/mmu_notifier.rst
6198          */
6199         i_mmap_unlock_write(vma->vm_file->f_mapping);
6200         mmu_notifier_invalidate_range_end(&range);
6201 
6202         return pages << h->order;
6203 }
6204 
6205 /* Return true if reservation was successful, false otherwise.  */
6206 bool hugetlb_reserve_pages(struct inode *inode,
6207                                         long from, long to,
6208                                         struct vm_area_struct *vma,
6209                                         vm_flags_t vm_flags)
6210 {
6211         long chg, add = -1;
6212         struct hstate *h = hstate_inode(inode);
6213         struct hugepage_subpool *spool = subpool_inode(inode);
6214         struct resv_map *resv_map;
6215         struct hugetlb_cgroup *h_cg = NULL;
6216         long gbl_reserve, regions_needed = 0;
6217 
6218         /* This should never happen */
6219         if (from > to) {
6220                 VM_WARN(1, "%s called with a negative range\n", __func__);
6221                 return false;
6222         }
6223 
6224         /*
6225          * Only apply hugepage reservation if asked. At fault time, an
6226          * attempt will be made for VM_NORESERVE to allocate a page
6227          * without using reserves
6228          */
6229         if (vm_flags & VM_NORESERVE)
6230                 return true;
6231 
6232         /*
6233          * Shared mappings base their reservation on the number of pages that
6234          * are already allocated on behalf of the file. Private mappings need
6235          * to reserve the full area even if read-only as mprotect() may be
6236          * called to make the mapping read-write. Assume !vma is a shm mapping
6237          */
6238         if (!vma || vma->vm_flags & VM_MAYSHARE) {
6239                 /*
6240                  * resv_map can not be NULL as hugetlb_reserve_pages is only
6241                  * called for inodes for which resv_maps were created (see
6242                  * hugetlbfs_get_inode).
6243                  */
6244                 resv_map = inode_resv_map(inode);
6245 
6246                 chg = region_chg(resv_map, from, to, &regions_needed);
6247 
6248         } else {
6249                 /* Private mapping. */
6250                 resv_map = resv_map_alloc();
6251                 if (!resv_map)
6252                         return false;
6253 
6254                 chg = to - from;
6255 
6256                 set_vma_resv_map(vma, resv_map);
6257                 set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
6258         }
6259 
6260         if (chg < 0)
6261                 goto out_err;
6262 
6263         if (hugetlb_cgroup_charge_cgroup_rsvd(hstate_index(h),
6264                                 chg * pages_per_huge_page(h), &h_cg) < 0)
6265                 goto out_err;
6266 
6267         if (vma && !(vma->vm_flags & VM_MAYSHARE) && h_cg) {
6268                 /* For private mappings, the hugetlb_cgroup uncharge info hangs
6269                  * of the resv_map.
6270                  */
6271                 resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, h_cg, h);
6272         }
6273 
6274         /*
6275          * There must be enough pages in the subpool for the mapping. If
6276          * the subpool has a minimum size, there may be some global
6277          * reservations already in place (gbl_reserve).
6278          */
6279         gbl_reserve = hugepage_subpool_get_pages(spool, chg);
6280         if (gbl_reserve < 0)
6281                 goto out_uncharge_cgroup;
6282 
6283         /*
6284          * Check enough hugepages are available for the reservation.
6285          * Hand the pages back to the subpool if there are not
6286          */
6287         if (hugetlb_acct_memory(h, gbl_reserve) < 0)
6288                 goto out_put_pages;
6289 
6290         /*
6291          * Account for the reservations made. Shared mappings record regions
6292          * that have reservations as they are shared by multiple VMAs.
6293          * When the last VMA disappears, the region map says how much
6294          * the reservation was and the page cache tells how much of
6295          * the reservation was consumed. Private mappings are per-VMA and
6296          * only the consumed reservations are tracked. When the VMA
6297          * disappears, the original reservation is the VMA size and the
6298          * consumed reservations are stored in the map. Hence, nothing
6299          * else has to be done for private mappings here
6300          */
6301         if (!vma || vma->vm_flags & VM_MAYSHARE) {
6302                 add = region_add(resv_map, from, to, regions_needed, h, h_cg);
6303 
6304                 if (unlikely(add < 0)) {
6305                         hugetlb_acct_memory(h, -gbl_reserve);
6306                         goto out_put_pages;
6307                 } else if (unlikely(chg > add)) {
6308                         /*
6309                          * pages in this range were added to the reserve
6310                          * map between region_chg and region_add.  This
6311                          * indicates a race with alloc_huge_page.  Adjust
6312                          * the subpool and reserve counts modified above
6313                          * based on the difference.
6314                          */
6315                         long rsv_adjust;
6316 
6317                         /*
6318                          * hugetlb_cgroup_uncharge_cgroup_rsvd() will put the
6319                          * reference to h_cg->css. See comment below for detail.
6320                          */
6321                         hugetlb_cgroup_uncharge_cgroup_rsvd(
6322                                 hstate_index(h),
6323                                 (chg - add) * pages_per_huge_page(h), h_cg);
6324 
6325                         rsv_adjust = hugepage_subpool_put_pages(spool,
6326                                                                 chg - add);
6327                         hugetlb_acct_memory(h, -rsv_adjust);
6328                 } else if (h_cg) {
6329                         /*
6330                          * The file_regions will hold their own reference to
6331                          * h_cg->css. So we should release the reference held
6332                          * via hugetlb_cgroup_charge_cgroup_rsvd() when we are
6333                          * done.
6334                          */
6335                         hugetlb_cgroup_put_rsvd_cgroup(h_cg);
6336                 }
6337         }
6338         return true;
6339 
6340 out_put_pages:
6341         /* put back original number of pages, chg */
6342         (void)hugepage_subpool_put_pages(spool, chg);
6343 out_uncharge_cgroup:
6344         hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h),
6345                                             chg * pages_per_huge_page(h), h_cg);
6346 out_err:
6347         if (!vma || vma->vm_flags & VM_MAYSHARE)
6348                 /* Only call region_abort if the region_chg succeeded but the
6349                  * region_add failed or didn't run.
6350                  */
6351                 if (chg >= 0 && add < 0)
6352                         region_abort(resv_map, from, to, regions_needed);
6353         if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
6354                 kref_put(&resv_map->refs, resv_map_release);
6355         return false;
6356 }
6357 
6358 long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
6359                                                                 long freed)
6360 {
6361         struct hstate *h = hstate_inode(inode);
6362         struct resv_map *resv_map = inode_resv_map(inode);
6363         long chg = 0;
6364         struct hugepage_subpool *spool = subpool_inode(inode);
6365         long gbl_reserve;
6366 
6367         /*
6368          * Since this routine can be called in the evict inode path for all
6369          * hugetlbfs inodes, resv_map could be NULL.
6370          */
6371         if (resv_map) {
6372                 chg = region_del(resv_map, start, end);
6373                 /*
6374                  * region_del() can fail in the rare case where a region
6375                  * must be split and another region descriptor can not be
6376                  * allocated.  If end == LONG_MAX, it will not fail.
6377                  */
6378                 if (chg < 0)
6379                         return chg;
6380         }
6381 
6382         spin_lock(&inode->i_lock);
6383         inode->i_blocks -= (blocks_per_huge_page(h) * freed);
6384         spin_unlock(&inode->i_lock);
6385 
6386         /*
6387          * If the subpool has a minimum size, the number of global
6388          * reservations to be released may be adjusted.
6389          *
6390          * Note that !resv_map implies freed == 0. So (chg - freed)
6391          * won't go negative.
6392          */
6393         gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed));
6394         hugetlb_acct_memory(h, -gbl_reserve);
6395 
6396         return 0;
6397 }
6398 
6399 #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
6400 static unsigned long page_table_shareable(struct vm_area_struct *svma,
6401                                 struct vm_area_struct *vma,
6402                                 unsigned long addr, pgoff_t idx)
6403 {
6404         unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
6405                                 svma->vm_start;
6406         unsigned long sbase = saddr & PUD_MASK;
6407         unsigned long s_end = sbase + PUD_SIZE;
6408 
6409         /* Allow segments to share if only one is marked locked */
6410         unsigned long vm_flags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
6411         unsigned long svm_flags = svma->vm_flags & VM_LOCKED_CLEAR_MASK;
6412 
6413         /*
6414          * match the virtual addresses, permission and the alignment of the
6415          * page table page.
6416          */
6417         if (pmd_index(addr) != pmd_index(saddr) ||
6418             vm_flags != svm_flags ||
6419             !range_in_vma(svma, sbase, s_end))
6420                 return 0;
6421 
6422         return saddr;
6423 }
6424 
6425 static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr)
6426 {
6427         unsigned long base = addr & PUD_MASK;
6428         unsigned long end = base + PUD_SIZE;
6429 
6430         /*
6431          * check on proper vm_flags and page table alignment
6432          */
6433         if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end))
6434                 return true;
6435         return false;
6436 }
6437 
6438 bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
6439 {
6440 #ifdef CONFIG_USERFAULTFD
6441         if (uffd_disable_huge_pmd_share(vma))
6442                 return false;
6443 #endif
6444         return vma_shareable(vma, addr);
6445 }
6446 
6447 /*
6448  * Determine if start,end range within vma could be mapped by shared pmd.
6449  * If yes, adjust start and end to cover range associated with possible
6450  * shared pmd mappings.
6451  */
6452 void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
6453                                 unsigned long *start, unsigned long *end)
6454 {
6455         unsigned long v_start = ALIGN(vma->vm_start, PUD_SIZE),
6456                 v_end = ALIGN_DOWN(vma->vm_end, PUD_SIZE);
6457 
6458         /*
6459          * vma needs to span at least one aligned PUD size, and the range
6460          * must be at least partially within in.
6461          */
6462         if (!(vma->vm_flags & VM_MAYSHARE) || !(v_end > v_start) ||
6463                 (*end <= v_start) || (*start >= v_end))
6464                 return;
6465 
6466         /* Extend the range to be PUD aligned for a worst case scenario */
6467         if (*start > v_start)
6468                 *start = ALIGN_DOWN(*start, PUD_SIZE);
6469 
6470         if (*end < v_end)
6471                 *end = ALIGN(*end, PUD_SIZE);
6472 }
6473 
6474 /*
6475  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
6476  * and returns the corresponding pte. While this is not necessary for the
6477  * !shared pmd case because we can allocate the pmd later as well, it makes the
6478  * code much cleaner.
6479  *
6480  * This routine must be called with i_mmap_rwsem held in at least read mode if
6481  * sharing is possible.  For hugetlbfs, this prevents removal of any page
6482  * table entries associated with the address space.  This is important as we
6483  * are setting up sharing based on existing page table entries (mappings).
6484  */
6485 pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
6486                       unsigned long addr, pud_t *pud)
6487 {
6488         struct address_space *mapping = vma->vm_file->f_mapping;
6489         pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
6490                         vma->vm_pgoff;
6491         struct vm_area_struct *svma;
6492         unsigned long saddr;
6493         pte_t *spte = NULL;
6494         pte_t *pte;
6495         spinlock_t *ptl;
6496 
6497         i_mmap_assert_locked(mapping);
6498         vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
6499                 if (svma == vma)
6500                         continue;
6501 
6502                 saddr = page_table_shareable(svma, vma, addr, idx);
6503                 if (saddr) {
6504                         spte = huge_pte_offset(svma->vm_mm, saddr,
6505                                                vma_mmu_pagesize(svma));
6506                         if (spte) {
6507                                 get_page(virt_to_page(spte));
6508                                 break;
6509                         }
6510                 }
6511         }
6512 
6513         if (!spte)
6514                 goto out;
6515 
6516         ptl = huge_pte_lock(hstate_vma(vma), mm, spte);
6517         if (pud_none(*pud)) {
6518                 pud_populate(mm, pud,
6519                                 (pmd_t *)((unsigned long)spte & PAGE_MASK));
6520                 mm_inc_nr_pmds(mm);
6521         } else {
6522                 put_page(virt_to_page(spte));
6523         }
6524         spin_unlock(ptl);
6525 out:
6526         pte = (pte_t *)pmd_alloc(mm, pud, addr);
6527         return pte;
6528 }
6529 
6530 /*
6531  * unmap huge page backed by shared pte.
6532  *
6533  * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
6534  * indicated by page_count > 1, unmap is achieved by clearing pud and
6535  * decrementing the ref count. If count == 1, the pte page is not shared.
6536  *
6537  * Called with page table lock held and i_mmap_rwsem held in write mode.
6538  *
6539  * returns: 1 successfully unmapped a shared pte page
6540  *          0 the underlying pte page is not shared, or it is the last user
6541  */
6542 int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
6543                                         unsigned long *addr, pte_t *ptep)
6544 {
6545         pgd_t *pgd = pgd_offset(mm, *addr);
6546         p4d_t *p4d = p4d_offset(pgd, *addr);
6547         pud_t *pud = pud_offset(p4d, *addr);
6548 
6549         i_mmap_assert_write_locked(vma->vm_file->f_mapping);
6550         BUG_ON(page_count(virt_to_page(ptep)) == 0);
6551         if (page_count(virt_to_page(ptep)) == 1)
6552                 return 0;
6553 
6554         pud_clear(pud);
6555         put_page(virt_to_page(ptep));
6556         mm_dec_nr_pmds(mm);
6557         *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
6558         return 1;
6559 }
6560 
6561 #else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
6562 pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma,
6563                       unsigned long addr, pud_t *pud)
6564 {
6565         return NULL;
6566 }
6567 
6568 int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma,
6569                                 unsigned long *addr, pte_t *ptep)
6570 {
6571         return 0;
6572 }
6573 
6574 void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
6575                                 unsigned long *start, unsigned long *end)
6576 {
6577 }
6578 
6579 bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
6580 {
6581         return false;
6582 }
6583 #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */
6584 
6585 #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB
6586 pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
6587                         unsigned long addr, unsigned long sz)
6588 {
6589         pgd_t *pgd;
6590         p4d_t *p4d;
6591         pud_t *pud;
6592         pte_t *pte = NULL;
6593 
6594         pgd = pgd_offset(mm, addr);
6595         p4d = p4d_alloc(mm, pgd, addr);
6596         if (!p4d)
6597                 return NULL;
6598         pud = pud_alloc(mm, p4d, addr);
6599         if (pud) {
6600                 if (sz == PUD_SIZE) {
6601                         pte = (pte_t *)pud;
6602                 } else {
6603                         BUG_ON(sz != PMD_SIZE);
6604                         if (want_pmd_share(vma, addr) && pud_none(*pud))
6605                                 pte = huge_pmd_share(mm, vma, addr, pud);
6606                         else
6607                                 pte = (pte_t *)pmd_alloc(mm, pud, addr);
6608                 }
6609         }
6610         BUG_ON(pte && pte_present(*pte) && !pte_huge(*pte));
6611 
6612         return pte;
6613 }
6614 
6615 /*
6616  * huge_pte_offset() - Walk the page table to resolve the hugepage
6617  * entry at address @addr
6618  *
6619  * Return: Pointer to page table entry (PUD or PMD) for
6620  * address @addr, or NULL if a !p*d_present() entry is encountered and the
6621  * size @sz doesn't match the hugepage size at this level of the page
6622  * table.
6623  */
6624 pte_t *huge_pte_offset(struct mm_struct *mm,
6625                        unsigned long addr, unsigned long sz)
6626 {
6627         pgd_t *pgd;
6628         p4d_t *p4d;
6629         pud_t *pud;
6630         pmd_t *pmd;
6631 
6632         pgd = pgd_offset(mm, addr);
6633         if (!pgd_present(*pgd))
6634                 return NULL;
6635         p4d = p4d_offset(pgd, addr);
6636         if (!p4d_present(*p4d))
6637                 return NULL;
6638 
6639         pud = pud_offset(p4d, addr);
6640         if (sz == PUD_SIZE)
6641                 /* must be pud huge, non-present or none */
6642                 return (pte_t *)pud;
6643         if (!pud_present(*pud))
6644                 return NULL;
6645         /* must have a valid entry and size to go further */
6646 
6647         pmd = pmd_offset(pud, addr);
6648         /* must be pmd huge, non-present or none */
6649         return (pte_t *)pmd;
6650 }
6651 
6652 #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
6653 
6654 /*
6655  * These functions are overwritable if your architecture needs its own
6656  * behavior.
6657  */
6658 struct page * __weak
6659 follow_huge_addr(struct mm_struct *mm, unsigned long address,
6660                               int write)
6661 {
6662         return ERR_PTR(-EINVAL);
6663 }
6664 
6665 struct page * __weak
6666 follow_huge_pd(struct vm_area_struct *vma,
6667                unsigned long address, hugepd_t hpd, int flags, int pdshift)
6668 {
6669         WARN(1, "hugepd follow called with no support for hugepage directory format\n");
6670         return NULL;
6671 }
6672 
6673 struct page * __weak
6674 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
6675                 pmd_t *pmd, int flags)
6676 {
6677         struct page *page = NULL;
6678         spinlock_t *ptl;
6679         pte_t pte;
6680 
6681         /* FOLL_GET and FOLL_PIN are mutually exclusive. */
6682         if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
6683                          (FOLL_PIN | FOLL_GET)))
6684                 return NULL;
6685 
6686 retry:
6687         ptl = pmd_lockptr(mm, pmd);
6688         spin_lock(ptl);
6689         /*
6690          * make sure that the address range covered by this pmd is not
6691          * unmapped from other threads.
6692          */
6693         if (!pmd_huge(*pmd))
6694                 goto out;
6695         pte = huge_ptep_get((pte_t *)pmd);
6696         if (pte_present(pte)) {
6697                 page = pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT);
6698                 /*
6699                  * try_grab_page() should always succeed here, because: a) we
6700                  * hold the pmd (ptl) lock, and b) we've just checked that the
6701                  * huge pmd (head) page is present in the page tables. The ptl
6702                  * prevents the head page and tail pages from being rearranged
6703                  * in any way. So this page must be available at this point,
6704                  * unless the page refcount overflowed:
6705                  */
6706                 if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
6707                         page = NULL;
6708                         goto out;
6709                 }
6710         } else {
6711                 if (is_hugetlb_entry_migration(pte)) {
6712                         spin_unlock(ptl);
6713                         __migration_entry_wait(mm, (pte_t *)pmd, ptl);
6714                         goto retry;
6715                 }
6716                 /*
6717                  * hwpoisoned entry is treated as no_page_table in
6718                  * follow_page_mask().
6719                  */
6720         }
6721 out:
6722         spin_unlock(ptl);
6723         return page;
6724 }
6725 
6726 struct page * __weak
6727 follow_huge_pud(struct mm_struct *mm, unsigned long address,
6728                 pud_t *pud, int flags)
6729 {
6730         if (flags & (FOLL_GET | FOLL_PIN))
6731                 return NULL;
6732 
6733         return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
6734 }
6735 
6736 struct page * __weak
6737 follow_huge_pgd(struct mm_struct *mm, unsigned long address, pgd_t *pgd, int flags)
6738 {
6739         if (flags & (FOLL_GET | FOLL_PIN))
6740                 return NULL;
6741 
6742         return pte_page(*(pte_t *)pgd) + ((address & ~PGDIR_MASK) >> PAGE_SHIFT);
6743 }
6744 
6745 bool isolate_huge_page(struct page *page, struct list_head *list)
6746 {
6747         bool ret = true;
6748 
6749         spin_lock_irq(&hugetlb_lock);
6750         if (!PageHeadHuge(page) ||
6751             !HPageMigratable(page) ||
6752             !get_page_unless_zero(page)) {
6753                 ret = false;
6754                 goto unlock;
6755         }
6756         ClearHPageMigratable(page);
6757         list_move_tail(&page->lru, list);
6758 unlock:
6759         spin_unlock_irq(&hugetlb_lock);
6760         return ret;
6761 }
6762 
6763 int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
6764 {
6765         int ret = 0;
6766 
6767         *hugetlb = false;
6768         spin_lock_irq(&hugetlb_lock);
6769         if (PageHeadHuge(page)) {
6770                 *hugetlb = true;
6771                 if (HPageFreed(page) || HPageMigratable(page))
6772                         ret = get_page_unless_zero(page);
6773                 else
6774                         ret = -EBUSY;
6775         }
6776         spin_unlock_irq(&hugetlb_lock);
6777         return ret;
6778 }
6779 
6780 void putback_active_hugepage(struct page *page)
6781 {
6782         spin_lock_irq(&hugetlb_lock);
6783         SetHPageMigratable(page);
6784         list_move_tail(&page->lru, &(page_hstate(page))->hugepage_activelist);
6785         spin_unlock_irq(&hugetlb_lock);
6786         put_page(page);
6787 }
6788 
6789 void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason)
6790 {
6791         struct hstate *h = page_hstate(oldpage);
6792 
6793         hugetlb_cgroup_migrate(oldpage, newpage);
6794         set_page_owner_migrate_reason(newpage, reason);
6795 
6796         /*
6797          * transfer temporary state of the new huge page. This is
6798          * reverse to other transitions because the newpage is going to
6799          * be final while the old one will be freed so it takes over
6800          * the temporary status.
6801          *
6802          * Also note that we have to transfer the per-node surplus state
6803          * here as well otherwise the global surplus count will not match
6804          * the per-node's.
6805          */
6806         if (HPageTemporary(newpage)) {
6807                 int old_nid = page_to_nid(oldpage);
6808                 int new_nid = page_to_nid(newpage);
6809 
6810                 SetHPageTemporary(oldpage);
6811                 ClearHPageTemporary(newpage);
6812 
6813                 /*
6814                  * There is no need to transfer the per-node surplus state
6815                  * when we do not cross the node.
6816                  */
6817                 if (new_nid == old_nid)
6818                         return;
6819                 spin_lock_irq(&hugetlb_lock);
6820                 if (h->surplus_huge_pages_node[old_nid]) {
6821                         h->surplus_huge_pages_node[old_nid]--;
6822                         h->surplus_huge_pages_node[new_nid]++;
6823                 }
6824                 spin_unlock_irq(&hugetlb_lock);
6825         }
6826 }
6827 
6828 /*
6829  * This function will unconditionally remove all the shared pmd pgtable entries
6830  * within the specific vma for a hugetlbfs memory range.
6831  */
6832 void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
6833 {
6834         struct hstate *h = hstate_vma(vma);
6835         unsigned long sz = huge_page_size(h);
6836         struct mm_struct *mm = vma->vm_mm;
6837         struct mmu_notifier_range range;
6838         unsigned long address, start, end;
6839         spinlock_t *ptl;
6840         pte_t *ptep;
6841 
6842         if (!(vma->vm_flags & VM_MAYSHARE))
6843                 return;
6844 
6845         start = ALIGN(vma->vm_start, PUD_SIZE);
6846         end = ALIGN_DOWN(vma->vm_end, PUD_SIZE);
6847 
6848         if (start >= end)
6849                 return;
6850 
6851         /*
6852          * No need to call adjust_range_if_pmd_sharing_possible(), because
6853          * we have already done the PUD_SIZE alignment.
6854          */
6855         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm,
6856                                 start, end);
6857         mmu_notifier_invalidate_range_start(&range);
6858         i_mmap_lock_write(vma->vm_file->f_mapping);
6859         for (address = start; address < end; address += PUD_SIZE) {
6860                 unsigned long tmp = address;
6861 
6862                 ptep = huge_pte_offset(mm, address, sz);
6863                 if (!ptep)
6864                         continue;
6865                 ptl = huge_pte_lock(h, mm, ptep);
6866                 /* We don't want 'address' to be changed */
6867                 huge_pmd_unshare(mm, vma, &tmp, ptep);
6868                 spin_unlock(ptl);
6869         }
6870         flush_hugetlb_tlb_range(vma, start, end);
6871         i_mmap_unlock_write(vma->vm_file->f_mapping);
6872         /*
6873          * No need to call mmu_notifier_invalidate_range(), see
6874          * Documentation/vm/mmu_notifier.rst.
6875          */
6876         mmu_notifier_invalidate_range_end(&range);
6877 }
6878 
6879 #ifdef CONFIG_CMA
6880 static bool cma_reserve_called __initdata;
6881 
6882 static int __init cmdline_parse_hugetlb_cma(char *p)
6883 {
6884         int nid, count = 0;
6885         unsigned long tmp;
6886         char *s = p;
6887 
6888         while (*s) {
6889                 if (sscanf(s, "%lu%n", &tmp, &count) != 1)
6890                         break;
6891 
6892                 if (s[count] == ':') {
6893                         nid = tmp;
6894                         if (nid < 0 || nid >= MAX_NUMNODES)
6895                                 break;
6896 
6897                         s += count + 1;
6898                         tmp = memparse(s, &s);
6899                         hugetlb_cma_size_in_node[nid] = tmp;
6900                         hugetlb_cma_size += tmp;
6901 
6902                         /*
6903                          * Skip the separator if have one, otherwise
6904                          * break the parsing.
6905                          */
6906                         if (*s == ',')
6907                                 s++;
6908                         else
6909                                 break;
6910                 } else {
6911                         hugetlb_cma_size = memparse(p, &p);
6912                         break;
6913                 }
6914         }
6915 
6916         return 0;
6917 }
6918 
6919 early_param("hugetlb_cma", cmdline_parse_hugetlb_cma);
6920 
6921 void __init hugetlb_cma_reserve(int order)
6922 {
6923         unsigned long size, reserved, per_node;
6924         bool node_specific_cma_alloc = false;
6925         int nid;
6926 
6927         cma_reserve_called = true;
6928 
6929         if (!hugetlb_cma_size)
6930                 return;
6931 
6932         for (nid = 0; nid < MAX_NUMNODES; nid++) {
6933                 if (hugetlb_cma_size_in_node[nid] == 0)
6934                         continue;
6935 
6936                 if (!node_state(nid, N_ONLINE)) {
6937                         pr_warn("hugetlb_cma: invalid node %d specified\n", nid);
6938                         hugetlb_cma_size -= hugetlb_cma_size_in_node[nid];
6939                         hugetlb_cma_size_in_node[nid] = 0;
6940                         continue;
6941                 }
6942 
6943                 if (hugetlb_cma_size_in_node[nid] < (PAGE_SIZE << order)) {
6944                         pr_warn("hugetlb_cma: cma area of node %d should be at least %lu MiB\n",
6945                                 nid, (PAGE_SIZE << order) / SZ_1M);
6946                         hugetlb_cma_size -= hugetlb_cma_size_in_node[nid];
6947                         hugetlb_cma_size_in_node[nid] = 0;
6948                 } else {
6949                         node_specific_cma_alloc = true;
6950                 }
6951         }
6952 
6953         /* Validate the CMA size again in case some invalid nodes specified. */
6954         if (!hugetlb_cma_size)
6955                 return;
6956 
6957         if (hugetlb_cma_size < (PAGE_SIZE << order)) {
6958                 pr_warn("hugetlb_cma: cma area should be at least %lu MiB\n",
6959                         (PAGE_SIZE << order) / SZ_1M);
6960                 hugetlb_cma_size = 0;
6961                 return;
6962         }
6963 
6964         if (!node_specific_cma_alloc) {
6965                 /*
6966                  * If 3 GB area is requested on a machine with 4 numa nodes,
6967                  * let's allocate 1 GB on first three nodes and ignore the last one.
6968                  */
6969                 per_node = DIV_ROUND_UP(hugetlb_cma_size, nr_online_nodes);
6970                 pr_info("hugetlb_cma: reserve %lu MiB, up to %lu MiB per node\n",
6971                         hugetlb_cma_size / SZ_1M, per_node / SZ_1M);
6972         }
6973 
6974         reserved = 0;
6975         for_each_node_state(nid, N_ONLINE) {
6976                 int res;
6977                 char name[CMA_MAX_NAME];
6978 
6979                 if (node_specific_cma_alloc) {
6980                         if (hugetlb_cma_size_in_node[nid] == 0)
6981                                 continue;
6982 
6983                         size = hugetlb_cma_size_in_node[nid];
6984                 } else {
6985                         size = min(per_node, hugetlb_cma_size - reserved);
6986                 }
6987 
6988                 size = round_up(size, PAGE_SIZE << order);
6989 
6990                 snprintf(name, sizeof(name), "hugetlb%d", nid);
6991                 /*
6992                  * Note that 'order per bit' is based on smallest size that
6993                  * may be returned to CMA allocator in the case of
6994                  * huge page demotion.
6995                  */
6996                 res = cma_declare_contiguous_nid(0, size, 0,
6997                                                 PAGE_SIZE << HUGETLB_PAGE_ORDER,
6998                                                  0, false, name,
6999                                                  &hugetlb_cma[nid], nid);
7000                 if (res) {
7001                         pr_warn("hugetlb_cma: reservation failed: err %d, node %d",
7002                                 res, nid);
7003                         continue;
7004                 }
7005 
7006                 reserved += size;
7007                 pr_info("hugetlb_cma: reserved %lu MiB on node %d\n",
7008                         size / SZ_1M, nid);
7009 
7010                 if (reserved >= hugetlb_cma_size)
7011                         break;
7012         }
7013 
7014         if (!reserved)
7015                 /*
7016                  * hugetlb_cma_size is used to determine if allocations from
7017                  * cma are possible.  Set to zero if no cma regions are set up.
7018                  */
7019                 hugetlb_cma_size = 0;
7020 }
7021 
7022 void __init hugetlb_cma_check(void)
7023 {
7024         if (!hugetlb_cma_size || cma_reserve_called)
7025                 return;
7026 
7027         pr_warn("hugetlb_cma: the option isn't supported by current arch\n");
7028 }
7029 
7030 #endif /* CONFIG_CMA */
7031 

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