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TOMOYO Linux Cross Reference
Linux/mm/hugetlb.c

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  1 /*
  2  * Generic hugetlb support.
  3  * (C) William Irwin, April 2004
  4  */
  5 #include <linux/list.h>
  6 #include <linux/init.h>
  7 #include <linux/module.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/cpuset.h>
 17 #include <linux/mutex.h>
 18 #include <linux/bootmem.h>
 19 #include <linux/sysfs.h>
 20 #include <linux/slab.h>
 21 #include <linux/mmdebug.h>
 22 #include <linux/rmap.h>
 23 #include <linux/swap.h>
 24 #include <linux/swapops.h>
 25 
 26 #include <asm/page.h>
 27 #include <asm/pgtable.h>
 28 #include <linux/io.h>
 29 
 30 #include <linux/hugetlb.h>
 31 #include <linux/node.h>
 32 #include "internal.h"
 33 
 34 const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
 35 static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
 36 unsigned long hugepages_treat_as_movable;
 37 
 38 static int max_hstate;
 39 unsigned int default_hstate_idx;
 40 struct hstate hstates[HUGE_MAX_HSTATE];
 41 
 42 __initdata LIST_HEAD(huge_boot_pages);
 43 
 44 /* for command line parsing */
 45 static struct hstate * __initdata parsed_hstate;
 46 static unsigned long __initdata default_hstate_max_huge_pages;
 47 static unsigned long __initdata default_hstate_size;
 48 
 49 #define for_each_hstate(h) \
 50         for ((h) = hstates; (h) < &hstates[max_hstate]; (h)++)
 51 
 52 /*
 53  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
 54  */
 55 static DEFINE_SPINLOCK(hugetlb_lock);
 56 
 57 static inline void unlock_or_release_subpool(struct hugepage_subpool *spool)
 58 {
 59         bool free = (spool->count == 0) && (spool->used_hpages == 0);
 60 
 61         spin_unlock(&spool->lock);
 62 
 63         /* If no pages are used, and no other handles to the subpool
 64          * remain, free the subpool the subpool remain */
 65         if (free)
 66                 kfree(spool);
 67 }
 68 
 69 struct hugepage_subpool *hugepage_new_subpool(long nr_blocks)
 70 {
 71         struct hugepage_subpool *spool;
 72 
 73         spool = kmalloc(sizeof(*spool), GFP_KERNEL);
 74         if (!spool)
 75                 return NULL;
 76 
 77         spin_lock_init(&spool->lock);
 78         spool->count = 1;
 79         spool->max_hpages = nr_blocks;
 80         spool->used_hpages = 0;
 81 
 82         return spool;
 83 }
 84 
 85 void hugepage_put_subpool(struct hugepage_subpool *spool)
 86 {
 87         spin_lock(&spool->lock);
 88         BUG_ON(!spool->count);
 89         spool->count--;
 90         unlock_or_release_subpool(spool);
 91 }
 92 
 93 static int hugepage_subpool_get_pages(struct hugepage_subpool *spool,
 94                                       long delta)
 95 {
 96         int ret = 0;
 97 
 98         if (!spool)
 99                 return 0;
100 
101         spin_lock(&spool->lock);
102         if ((spool->used_hpages + delta) <= spool->max_hpages) {
103                 spool->used_hpages += delta;
104         } else {
105                 ret = -ENOMEM;
106         }
107         spin_unlock(&spool->lock);
108 
109         return ret;
110 }
111 
112 static void hugepage_subpool_put_pages(struct hugepage_subpool *spool,
113                                        long delta)
114 {
115         if (!spool)
116                 return;
117 
118         spin_lock(&spool->lock);
119         spool->used_hpages -= delta;
120         /* If hugetlbfs_put_super couldn't free spool due to
121         * an outstanding quota reference, free it now. */
122         unlock_or_release_subpool(spool);
123 }
124 
125 static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
126 {
127         return HUGETLBFS_SB(inode->i_sb)->spool;
128 }
129 
130 static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
131 {
132         return subpool_inode(vma->vm_file->f_dentry->d_inode);
133 }
134 
135 /*
136  * Region tracking -- allows tracking of reservations and instantiated pages
137  *                    across the pages in a mapping.
138  *
139  * The region data structures are protected by a combination of the mmap_sem
140  * and the hugetlb_instantion_mutex.  To access or modify a region the caller
141  * must either hold the mmap_sem for write, or the mmap_sem for read and
142  * the hugetlb_instantiation mutex:
143  *
144  *      down_write(&mm->mmap_sem);
145  * or
146  *      down_read(&mm->mmap_sem);
147  *      mutex_lock(&hugetlb_instantiation_mutex);
148  */
149 struct file_region {
150         struct list_head link;
151         long from;
152         long to;
153 };
154 
155 static long region_add(struct list_head *head, long f, long t)
156 {
157         struct file_region *rg, *nrg, *trg;
158 
159         /* Locate the region we are either in or before. */
160         list_for_each_entry(rg, head, link)
161                 if (f <= rg->to)
162                         break;
163 
164         /* Round our left edge to the current segment if it encloses us. */
165         if (f > rg->from)
166                 f = rg->from;
167 
168         /* Check for and consume any regions we now overlap with. */
169         nrg = rg;
170         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
171                 if (&rg->link == head)
172                         break;
173                 if (rg->from > t)
174                         break;
175 
176                 /* If this area reaches higher then extend our area to
177                  * include it completely.  If this is not the first area
178                  * which we intend to reuse, free it. */
179                 if (rg->to > t)
180                         t = rg->to;
181                 if (rg != nrg) {
182                         list_del(&rg->link);
183                         kfree(rg);
184                 }
185         }
186         nrg->from = f;
187         nrg->to = t;
188         return 0;
189 }
190 
191 static long region_chg(struct list_head *head, long f, long t)
192 {
193         struct file_region *rg, *nrg;
194         long chg = 0;
195 
196         /* Locate the region we are before or in. */
197         list_for_each_entry(rg, head, link)
198                 if (f <= rg->to)
199                         break;
200 
201         /* If we are below the current region then a new region is required.
202          * Subtle, allocate a new region at the position but make it zero
203          * size such that we can guarantee to record the reservation. */
204         if (&rg->link == head || t < rg->from) {
205                 nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
206                 if (!nrg)
207                         return -ENOMEM;
208                 nrg->from = f;
209                 nrg->to   = f;
210                 INIT_LIST_HEAD(&nrg->link);
211                 list_add(&nrg->link, rg->link.prev);
212 
213                 return t - f;
214         }
215 
216         /* Round our left edge to the current segment if it encloses us. */
217         if (f > rg->from)
218                 f = rg->from;
219         chg = t - f;
220 
221         /* Check for and consume any regions we now overlap with. */
222         list_for_each_entry(rg, rg->link.prev, link) {
223                 if (&rg->link == head)
224                         break;
225                 if (rg->from > t)
226                         return chg;
227 
228                 /* We overlap with this area, if it extends further than
229                  * us then we must extend ourselves.  Account for its
230                  * existing reservation. */
231                 if (rg->to > t) {
232                         chg += rg->to - t;
233                         t = rg->to;
234                 }
235                 chg -= rg->to - rg->from;
236         }
237         return chg;
238 }
239 
240 static long region_truncate(struct list_head *head, long end)
241 {
242         struct file_region *rg, *trg;
243         long chg = 0;
244 
245         /* Locate the region we are either in or before. */
246         list_for_each_entry(rg, head, link)
247                 if (end <= rg->to)
248                         break;
249         if (&rg->link == head)
250                 return 0;
251 
252         /* If we are in the middle of a region then adjust it. */
253         if (end > rg->from) {
254                 chg = rg->to - end;
255                 rg->to = end;
256                 rg = list_entry(rg->link.next, typeof(*rg), link);
257         }
258 
259         /* Drop any remaining regions. */
260         list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
261                 if (&rg->link == head)
262                         break;
263                 chg += rg->to - rg->from;
264                 list_del(&rg->link);
265                 kfree(rg);
266         }
267         return chg;
268 }
269 
270 static long region_count(struct list_head *head, long f, long t)
271 {
272         struct file_region *rg;
273         long chg = 0;
274 
275         /* Locate each segment we overlap with, and count that overlap. */
276         list_for_each_entry(rg, head, link) {
277                 int seg_from;
278                 int seg_to;
279 
280                 if (rg->to <= f)
281                         continue;
282                 if (rg->from >= t)
283                         break;
284 
285                 seg_from = max(rg->from, f);
286                 seg_to = min(rg->to, t);
287 
288                 chg += seg_to - seg_from;
289         }
290 
291         return chg;
292 }
293 
294 /*
295  * Convert the address within this vma to the page offset within
296  * the mapping, in pagecache page units; huge pages here.
297  */
298 static pgoff_t vma_hugecache_offset(struct hstate *h,
299                         struct vm_area_struct *vma, unsigned long address)
300 {
301         return ((address - vma->vm_start) >> huge_page_shift(h)) +
302                         (vma->vm_pgoff >> huge_page_order(h));
303 }
304 
305 pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
306                                      unsigned long address)
307 {
308         return vma_hugecache_offset(hstate_vma(vma), vma, address);
309 }
310 
311 /*
312  * Return the size of the pages allocated when backing a VMA. In the majority
313  * cases this will be same size as used by the page table entries.
314  */
315 unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
316 {
317         struct hstate *hstate;
318 
319         if (!is_vm_hugetlb_page(vma))
320                 return PAGE_SIZE;
321 
322         hstate = hstate_vma(vma);
323 
324         return 1UL << (hstate->order + PAGE_SHIFT);
325 }
326 EXPORT_SYMBOL_GPL(vma_kernel_pagesize);
327 
328 /*
329  * Return the page size being used by the MMU to back a VMA. In the majority
330  * of cases, the page size used by the kernel matches the MMU size. On
331  * architectures where it differs, an architecture-specific version of this
332  * function is required.
333  */
334 #ifndef vma_mmu_pagesize
335 unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
336 {
337         return vma_kernel_pagesize(vma);
338 }
339 #endif
340 
341 /*
342  * Flags for MAP_PRIVATE reservations.  These are stored in the bottom
343  * bits of the reservation map pointer, which are always clear due to
344  * alignment.
345  */
346 #define HPAGE_RESV_OWNER    (1UL << 0)
347 #define HPAGE_RESV_UNMAPPED (1UL << 1)
348 #define HPAGE_RESV_MASK (HPAGE_RESV_OWNER | HPAGE_RESV_UNMAPPED)
349 
350 /*
351  * These helpers are used to track how many pages are reserved for
352  * faults in a MAP_PRIVATE mapping. Only the process that called mmap()
353  * is guaranteed to have their future faults succeed.
354  *
355  * With the exception of reset_vma_resv_huge_pages() which is called at fork(),
356  * the reserve counters are updated with the hugetlb_lock held. It is safe
357  * to reset the VMA at fork() time as it is not in use yet and there is no
358  * chance of the global counters getting corrupted as a result of the values.
359  *
360  * The private mapping reservation is represented in a subtly different
361  * manner to a shared mapping.  A shared mapping has a region map associated
362  * with the underlying file, this region map represents the backing file
363  * pages which have ever had a reservation assigned which this persists even
364  * after the page is instantiated.  A private mapping has a region map
365  * associated with the original mmap which is attached to all VMAs which
366  * reference it, this region map represents those offsets which have consumed
367  * reservation ie. where pages have been instantiated.
368  */
369 static unsigned long get_vma_private_data(struct vm_area_struct *vma)
370 {
371         return (unsigned long)vma->vm_private_data;
372 }
373 
374 static void set_vma_private_data(struct vm_area_struct *vma,
375                                                         unsigned long value)
376 {
377         vma->vm_private_data = (void *)value;
378 }
379 
380 struct resv_map {
381         struct kref refs;
382         struct list_head regions;
383 };
384 
385 static struct resv_map *resv_map_alloc(void)
386 {
387         struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
388         if (!resv_map)
389                 return NULL;
390 
391         kref_init(&resv_map->refs);
392         INIT_LIST_HEAD(&resv_map->regions);
393 
394         return resv_map;
395 }
396 
397 static void resv_map_release(struct kref *ref)
398 {
399         struct resv_map *resv_map = container_of(ref, struct resv_map, refs);
400 
401         /* Clear out any active regions before we release the map. */
402         region_truncate(&resv_map->regions, 0);
403         kfree(resv_map);
404 }
405 
406 static struct resv_map *vma_resv_map(struct vm_area_struct *vma)
407 {
408         VM_BUG_ON(!is_vm_hugetlb_page(vma));
409         if (!(vma->vm_flags & VM_MAYSHARE))
410                 return (struct resv_map *)(get_vma_private_data(vma) &
411                                                         ~HPAGE_RESV_MASK);
412         return NULL;
413 }
414 
415 static void set_vma_resv_map(struct vm_area_struct *vma, struct resv_map *map)
416 {
417         VM_BUG_ON(!is_vm_hugetlb_page(vma));
418         VM_BUG_ON(vma->vm_flags & VM_MAYSHARE);
419 
420         set_vma_private_data(vma, (get_vma_private_data(vma) &
421                                 HPAGE_RESV_MASK) | (unsigned long)map);
422 }
423 
424 static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
425 {
426         VM_BUG_ON(!is_vm_hugetlb_page(vma));
427         VM_BUG_ON(vma->vm_flags & VM_MAYSHARE);
428 
429         set_vma_private_data(vma, get_vma_private_data(vma) | flags);
430 }
431 
432 static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
433 {
434         VM_BUG_ON(!is_vm_hugetlb_page(vma));
435 
436         return (get_vma_private_data(vma) & flag) != 0;
437 }
438 
439 /* Decrement the reserved pages in the hugepage pool by one */
440 static void decrement_hugepage_resv_vma(struct hstate *h,
441                         struct vm_area_struct *vma)
442 {
443         if (vma->vm_flags & VM_NORESERVE)
444                 return;
445 
446         if (vma->vm_flags & VM_MAYSHARE) {
447                 /* Shared mappings always use reserves */
448                 h->resv_huge_pages--;
449         } else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
450                 /*
451                  * Only the process that called mmap() has reserves for
452                  * private mappings.
453                  */
454                 h->resv_huge_pages--;
455         }
456 }
457 
458 /* Reset counters to 0 and clear all HPAGE_RESV_* flags */
459 void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
460 {
461         VM_BUG_ON(!is_vm_hugetlb_page(vma));
462         if (!(vma->vm_flags & VM_MAYSHARE))
463                 vma->vm_private_data = (void *)0;
464 }
465 
466 /* Returns true if the VMA has associated reserve pages */
467 static int vma_has_reserves(struct vm_area_struct *vma)
468 {
469         if (vma->vm_flags & VM_MAYSHARE)
470                 return 1;
471         if (is_vma_resv_set(vma, HPAGE_RESV_OWNER))
472                 return 1;
473         return 0;
474 }
475 
476 static void copy_gigantic_page(struct page *dst, struct page *src)
477 {
478         int i;
479         struct hstate *h = page_hstate(src);
480         struct page *dst_base = dst;
481         struct page *src_base = src;
482 
483         for (i = 0; i < pages_per_huge_page(h); ) {
484                 cond_resched();
485                 copy_highpage(dst, src);
486 
487                 i++;
488                 dst = mem_map_next(dst, dst_base, i);
489                 src = mem_map_next(src, src_base, i);
490         }
491 }
492 
493 void copy_huge_page(struct page *dst, struct page *src)
494 {
495         int i;
496         struct hstate *h = page_hstate(src);
497 
498         if (unlikely(pages_per_huge_page(h) > MAX_ORDER_NR_PAGES)) {
499                 copy_gigantic_page(dst, src);
500                 return;
501         }
502 
503         might_sleep();
504         for (i = 0; i < pages_per_huge_page(h); i++) {
505                 cond_resched();
506                 copy_highpage(dst + i, src + i);
507         }
508 }
509 
510 static void enqueue_huge_page(struct hstate *h, struct page *page)
511 {
512         int nid = page_to_nid(page);
513         list_add(&page->lru, &h->hugepage_freelists[nid]);
514         h->free_huge_pages++;
515         h->free_huge_pages_node[nid]++;
516 }
517 
518 static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
519 {
520         struct page *page;
521 
522         if (list_empty(&h->hugepage_freelists[nid]))
523                 return NULL;
524         page = list_entry(h->hugepage_freelists[nid].next, struct page, lru);
525         list_del(&page->lru);
526         set_page_refcounted(page);
527         h->free_huge_pages--;
528         h->free_huge_pages_node[nid]--;
529         return page;
530 }
531 
532 static struct page *dequeue_huge_page_vma(struct hstate *h,
533                                 struct vm_area_struct *vma,
534                                 unsigned long address, int avoid_reserve)
535 {
536         struct page *page = NULL;
537         struct mempolicy *mpol;
538         nodemask_t *nodemask;
539         struct zonelist *zonelist;
540         struct zone *zone;
541         struct zoneref *z;
542         unsigned int cpuset_mems_cookie;
543 
544 retry_cpuset:
545         cpuset_mems_cookie = get_mems_allowed();
546         zonelist = huge_zonelist(vma, address,
547                                         htlb_alloc_mask, &mpol, &nodemask);
548         /*
549          * A child process with MAP_PRIVATE mappings created by their parent
550          * have no page reserves. This check ensures that reservations are
551          * not "stolen". The child may still get SIGKILLed
552          */
553         if (!vma_has_reserves(vma) &&
554                         h->free_huge_pages - h->resv_huge_pages == 0)
555                 goto err;
556 
557         /* If reserves cannot be used, ensure enough pages are in the pool */
558         if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
559                 goto err;
560 
561         for_each_zone_zonelist_nodemask(zone, z, zonelist,
562                                                 MAX_NR_ZONES - 1, nodemask) {
563                 if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask)) {
564                         page = dequeue_huge_page_node(h, zone_to_nid(zone));
565                         if (page) {
566                                 if (!avoid_reserve)
567                                         decrement_hugepage_resv_vma(h, vma);
568                                 break;
569                         }
570                 }
571         }
572 
573         mpol_cond_put(mpol);
574         if (unlikely(!put_mems_allowed(cpuset_mems_cookie) && !page))
575                 goto retry_cpuset;
576         return page;
577 
578 err:
579         mpol_cond_put(mpol);
580         return NULL;
581 }
582 
583 static void update_and_free_page(struct hstate *h, struct page *page)
584 {
585         int i;
586 
587         VM_BUG_ON(h->order >= MAX_ORDER);
588 
589         h->nr_huge_pages--;
590         h->nr_huge_pages_node[page_to_nid(page)]--;
591         for (i = 0; i < pages_per_huge_page(h); i++) {
592                 page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
593                                 1 << PG_referenced | 1 << PG_dirty |
594                                 1 << PG_active | 1 << PG_reserved |
595                                 1 << PG_private | 1 << PG_writeback);
596         }
597         set_compound_page_dtor(page, NULL);
598         set_page_refcounted(page);
599         arch_release_hugepage(page);
600         __free_pages(page, huge_page_order(h));
601 }
602 
603 struct hstate *size_to_hstate(unsigned long size)
604 {
605         struct hstate *h;
606 
607         for_each_hstate(h) {
608                 if (huge_page_size(h) == size)
609                         return h;
610         }
611         return NULL;
612 }
613 
614 static void free_huge_page(struct page *page)
615 {
616         /*
617          * Can't pass hstate in here because it is called from the
618          * compound page destructor.
619          */
620         struct hstate *h = page_hstate(page);
621         int nid = page_to_nid(page);
622         struct hugepage_subpool *spool =
623                 (struct hugepage_subpool *)page_private(page);
624 
625         set_page_private(page, 0);
626         page->mapping = NULL;
627         BUG_ON(page_count(page));
628         BUG_ON(page_mapcount(page));
629         INIT_LIST_HEAD(&page->lru);
630 
631         spin_lock(&hugetlb_lock);
632         if (h->surplus_huge_pages_node[nid] && huge_page_order(h) < MAX_ORDER) {
633                 update_and_free_page(h, page);
634                 h->surplus_huge_pages--;
635                 h->surplus_huge_pages_node[nid]--;
636         } else {
637                 enqueue_huge_page(h, page);
638         }
639         spin_unlock(&hugetlb_lock);
640         hugepage_subpool_put_pages(spool, 1);
641 }
642 
643 static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
644 {
645         set_compound_page_dtor(page, free_huge_page);
646         spin_lock(&hugetlb_lock);
647         h->nr_huge_pages++;
648         h->nr_huge_pages_node[nid]++;
649         spin_unlock(&hugetlb_lock);
650         put_page(page); /* free it into the hugepage allocator */
651 }
652 
653 static void prep_compound_gigantic_page(struct page *page, unsigned long order)
654 {
655         int i;
656         int nr_pages = 1 << order;
657         struct page *p = page + 1;
658 
659         /* we rely on prep_new_huge_page to set the destructor */
660         set_compound_order(page, order);
661         __SetPageHead(page);
662         for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
663                 __SetPageTail(p);
664                 set_page_count(p, 0);
665                 p->first_page = page;
666         }
667 }
668 
669 int PageHuge(struct page *page)
670 {
671         compound_page_dtor *dtor;
672 
673         if (!PageCompound(page))
674                 return 0;
675 
676         page = compound_head(page);
677         dtor = get_compound_page_dtor(page);
678 
679         return dtor == free_huge_page;
680 }
681 EXPORT_SYMBOL_GPL(PageHuge);
682 
683 /*
684  * PageHeadHuge() only returns true for hugetlbfs head page, but not for
685  * normal or transparent huge pages.
686  */
687 int PageHeadHuge(struct page *page_head)
688 {
689         compound_page_dtor *dtor;
690 
691         if (!PageHead(page_head))
692                 return 0;
693 
694         dtor = get_compound_page_dtor(page_head);
695 
696         return dtor == free_huge_page;
697 }
698 EXPORT_SYMBOL_GPL(PageHeadHuge);
699 
700 pgoff_t __basepage_index(struct page *page)
701 {
702         struct page *page_head = compound_head(page);
703         pgoff_t index = page_index(page_head);
704         unsigned long compound_idx;
705 
706         if (!PageHuge(page_head))
707                 return page_index(page);
708 
709         if (compound_order(page_head) >= MAX_ORDER)
710                 compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
711         else
712                 compound_idx = page - page_head;
713 
714         return (index << compound_order(page_head)) + compound_idx;
715 }
716 
717 static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
718 {
719         struct page *page;
720 
721         if (h->order >= MAX_ORDER)
722                 return NULL;
723 
724         page = alloc_pages_exact_node(nid,
725                 htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
726                                                 __GFP_REPEAT|__GFP_NOWARN,
727                 huge_page_order(h));
728         if (page) {
729                 if (arch_prepare_hugepage(page)) {
730                         __free_pages(page, huge_page_order(h));
731                         return NULL;
732                 }
733                 prep_new_huge_page(h, page, nid);
734         }
735 
736         return page;
737 }
738 
739 /*
740  * common helper functions for hstate_next_node_to_{alloc|free}.
741  * We may have allocated or freed a huge page based on a different
742  * nodes_allowed previously, so h->next_node_to_{alloc|free} might
743  * be outside of *nodes_allowed.  Ensure that we use an allowed
744  * node for alloc or free.
745  */
746 static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
747 {
748         nid = next_node(nid, *nodes_allowed);
749         if (nid == MAX_NUMNODES)
750                 nid = first_node(*nodes_allowed);
751         VM_BUG_ON(nid >= MAX_NUMNODES);
752 
753         return nid;
754 }
755 
756 static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
757 {
758         if (!node_isset(nid, *nodes_allowed))
759                 nid = next_node_allowed(nid, nodes_allowed);
760         return nid;
761 }
762 
763 /*
764  * returns the previously saved node ["this node"] from which to
765  * allocate a persistent huge page for the pool and advance the
766  * next node from which to allocate, handling wrap at end of node
767  * mask.
768  */
769 static int hstate_next_node_to_alloc(struct hstate *h,
770                                         nodemask_t *nodes_allowed)
771 {
772         int nid;
773 
774         VM_BUG_ON(!nodes_allowed);
775 
776         nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
777         h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);
778 
779         return nid;
780 }
781 
782 static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
783 {
784         struct page *page;
785         int start_nid;
786         int next_nid;
787         int ret = 0;
788 
789         start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
790         next_nid = start_nid;
791 
792         do {
793                 page = alloc_fresh_huge_page_node(h, next_nid);
794                 if (page) {
795                         ret = 1;
796                         break;
797                 }
798                 next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
799         } while (next_nid != start_nid);
800 
801         if (ret)
802                 count_vm_event(HTLB_BUDDY_PGALLOC);
803         else
804                 count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
805 
806         return ret;
807 }
808 
809 /*
810  * helper for free_pool_huge_page() - return the previously saved
811  * node ["this node"] from which to free a huge page.  Advance the
812  * next node id whether or not we find a free huge page to free so
813  * that the next attempt to free addresses the next node.
814  */
815 static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
816 {
817         int nid;
818 
819         VM_BUG_ON(!nodes_allowed);
820 
821         nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
822         h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);
823 
824         return nid;
825 }
826 
827 /*
828  * Free huge page from pool from next node to free.
829  * Attempt to keep persistent huge pages more or less
830  * balanced over allowed nodes.
831  * Called with hugetlb_lock locked.
832  */
833 static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
834                                                          bool acct_surplus)
835 {
836         int start_nid;
837         int next_nid;
838         int ret = 0;
839 
840         start_nid = hstate_next_node_to_free(h, nodes_allowed);
841         next_nid = start_nid;
842 
843         do {
844                 /*
845                  * If we're returning unused surplus pages, only examine
846                  * nodes with surplus pages.
847                  */
848                 if ((!acct_surplus || h->surplus_huge_pages_node[next_nid]) &&
849                     !list_empty(&h->hugepage_freelists[next_nid])) {
850                         struct page *page =
851                                 list_entry(h->hugepage_freelists[next_nid].next,
852                                           struct page, lru);
853                         list_del(&page->lru);
854                         h->free_huge_pages--;
855                         h->free_huge_pages_node[next_nid]--;
856                         if (acct_surplus) {
857                                 h->surplus_huge_pages--;
858                                 h->surplus_huge_pages_node[next_nid]--;
859                         }
860                         update_and_free_page(h, page);
861                         ret = 1;
862                         break;
863                 }
864                 next_nid = hstate_next_node_to_free(h, nodes_allowed);
865         } while (next_nid != start_nid);
866 
867         return ret;
868 }
869 
870 static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
871 {
872         struct page *page;
873         unsigned int r_nid;
874 
875         if (h->order >= MAX_ORDER)
876                 return NULL;
877 
878         /*
879          * Assume we will successfully allocate the surplus page to
880          * prevent racing processes from causing the surplus to exceed
881          * overcommit
882          *
883          * This however introduces a different race, where a process B
884          * tries to grow the static hugepage pool while alloc_pages() is
885          * called by process A. B will only examine the per-node
886          * counters in determining if surplus huge pages can be
887          * converted to normal huge pages in adjust_pool_surplus(). A
888          * won't be able to increment the per-node counter, until the
889          * lock is dropped by B, but B doesn't drop hugetlb_lock until
890          * no more huge pages can be converted from surplus to normal
891          * state (and doesn't try to convert again). Thus, we have a
892          * case where a surplus huge page exists, the pool is grown, and
893          * the surplus huge page still exists after, even though it
894          * should just have been converted to a normal huge page. This
895          * does not leak memory, though, as the hugepage will be freed
896          * once it is out of use. It also does not allow the counters to
897          * go out of whack in adjust_pool_surplus() as we don't modify
898          * the node values until we've gotten the hugepage and only the
899          * per-node value is checked there.
900          */
901         spin_lock(&hugetlb_lock);
902         if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
903                 spin_unlock(&hugetlb_lock);
904                 return NULL;
905         } else {
906                 h->nr_huge_pages++;
907                 h->surplus_huge_pages++;
908         }
909         spin_unlock(&hugetlb_lock);
910 
911         if (nid == NUMA_NO_NODE)
912                 page = alloc_pages(htlb_alloc_mask|__GFP_COMP|
913                                    __GFP_REPEAT|__GFP_NOWARN,
914                                    huge_page_order(h));
915         else
916                 page = alloc_pages_exact_node(nid,
917                         htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
918                         __GFP_REPEAT|__GFP_NOWARN, huge_page_order(h));
919 
920         if (page && arch_prepare_hugepage(page)) {
921                 __free_pages(page, huge_page_order(h));
922                 return NULL;
923         }
924 
925         spin_lock(&hugetlb_lock);
926         if (page) {
927                 r_nid = page_to_nid(page);
928                 set_compound_page_dtor(page, free_huge_page);
929                 /*
930                  * We incremented the global counters already
931                  */
932                 h->nr_huge_pages_node[r_nid]++;
933                 h->surplus_huge_pages_node[r_nid]++;
934                 __count_vm_event(HTLB_BUDDY_PGALLOC);
935         } else {
936                 h->nr_huge_pages--;
937                 h->surplus_huge_pages--;
938                 __count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
939         }
940         spin_unlock(&hugetlb_lock);
941 
942         return page;
943 }
944 
945 /*
946  * This allocation function is useful in the context where vma is irrelevant.
947  * E.g. soft-offlining uses this function because it only cares physical
948  * address of error page.
949  */
950 struct page *alloc_huge_page_node(struct hstate *h, int nid)
951 {
952         struct page *page;
953 
954         spin_lock(&hugetlb_lock);
955         page = dequeue_huge_page_node(h, nid);
956         spin_unlock(&hugetlb_lock);
957 
958         if (!page)
959                 page = alloc_buddy_huge_page(h, nid);
960 
961         return page;
962 }
963 
964 /*
965  * Increase the hugetlb pool such that it can accommodate a reservation
966  * of size 'delta'.
967  */
968 static int gather_surplus_pages(struct hstate *h, int delta)
969 {
970         struct list_head surplus_list;
971         struct page *page, *tmp;
972         int ret, i;
973         int needed, allocated;
974 
975         needed = (h->resv_huge_pages + delta) - h->free_huge_pages;
976         if (needed <= 0) {
977                 h->resv_huge_pages += delta;
978                 return 0;
979         }
980 
981         allocated = 0;
982         INIT_LIST_HEAD(&surplus_list);
983 
984         ret = -ENOMEM;
985 retry:
986         spin_unlock(&hugetlb_lock);
987         for (i = 0; i < needed; i++) {
988                 page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
989                 if (!page)
990                         /*
991                          * We were not able to allocate enough pages to
992                          * satisfy the entire reservation so we free what
993                          * we've allocated so far.
994                          */
995                         goto free;
996 
997                 list_add(&page->lru, &surplus_list);
998         }
999         allocated += needed;
1000 
1001         /*
1002          * After retaking hugetlb_lock, we need to recalculate 'needed'
1003          * because either resv_huge_pages or free_huge_pages may have changed.
1004          */
1005         spin_lock(&hugetlb_lock);
1006         needed = (h->resv_huge_pages + delta) -
1007                         (h->free_huge_pages + allocated);
1008         if (needed > 0)
1009                 goto retry;
1010 
1011         /*
1012          * The surplus_list now contains _at_least_ the number of extra pages
1013          * needed to accommodate the reservation.  Add the appropriate number
1014          * of pages to the hugetlb pool and free the extras back to the buddy
1015          * allocator.  Commit the entire reservation here to prevent another
1016          * process from stealing the pages as they are added to the pool but
1017          * before they are reserved.
1018          */
1019         needed += allocated;
1020         h->resv_huge_pages += delta;
1021         ret = 0;
1022 
1023         /* Free the needed pages to the hugetlb pool */
1024         list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
1025                 if ((--needed) < 0)
1026                         break;
1027                 list_del(&page->lru);
1028                 /*
1029                  * This page is now managed by the hugetlb allocator and has
1030                  * no users -- drop the buddy allocator's reference.
1031                  */
1032                 put_page_testzero(page);
1033                 VM_BUG_ON(page_count(page));
1034                 enqueue_huge_page(h, page);
1035         }
1036         spin_unlock(&hugetlb_lock);
1037 
1038         /* Free unnecessary surplus pages to the buddy allocator */
1039 free:
1040         if (!list_empty(&surplus_list)) {
1041                 list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
1042                         list_del(&page->lru);
1043                         put_page(page);
1044                 }
1045         }
1046         spin_lock(&hugetlb_lock);
1047 
1048         return ret;
1049 }
1050 
1051 /*
1052  * When releasing a hugetlb pool reservation, any surplus pages that were
1053  * allocated to satisfy the reservation must be explicitly freed if they were
1054  * never used.
1055  * Called with hugetlb_lock held.
1056  */
1057 static void return_unused_surplus_pages(struct hstate *h,
1058                                         unsigned long unused_resv_pages)
1059 {
1060         unsigned long nr_pages;
1061 
1062         /* Uncommit the reservation */
1063         h->resv_huge_pages -= unused_resv_pages;
1064 
1065         /* Cannot return gigantic pages currently */
1066         if (h->order >= MAX_ORDER)
1067                 return;
1068 
1069         nr_pages = min(unused_resv_pages, h->surplus_huge_pages);
1070 
1071         /*
1072          * We want to release as many surplus pages as possible, spread
1073          * evenly across all nodes with memory. Iterate across these nodes
1074          * until we can no longer free unreserved surplus pages. This occurs
1075          * when the nodes with surplus pages have no free pages.
1076          * free_pool_huge_page() will balance the the freed pages across the
1077          * on-line nodes with memory and will handle the hstate accounting.
1078          */
1079         while (nr_pages--) {
1080                 if (!free_pool_huge_page(h, &node_states[N_HIGH_MEMORY], 1))
1081                         break;
1082                 cond_resched_lock(&hugetlb_lock);
1083         }
1084 }
1085 
1086 /*
1087  * Determine if the huge page at addr within the vma has an associated
1088  * reservation.  Where it does not we will need to logically increase
1089  * reservation and actually increase subpool usage before an allocation
1090  * can occur.  Where any new reservation would be required the
1091  * reservation change is prepared, but not committed.  Once the page
1092  * has been allocated from the subpool and instantiated the change should
1093  * be committed via vma_commit_reservation.  No action is required on
1094  * failure.
1095  */
1096 static long vma_needs_reservation(struct hstate *h,
1097                         struct vm_area_struct *vma, unsigned long addr)
1098 {
1099         struct address_space *mapping = vma->vm_file->f_mapping;
1100         struct inode *inode = mapping->host;
1101 
1102         if (vma->vm_flags & VM_MAYSHARE) {
1103                 pgoff_t idx = vma_hugecache_offset(h, vma, addr);
1104                 return region_chg(&inode->i_mapping->private_list,
1105                                                         idx, idx + 1);
1106 
1107         } else if (!is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
1108                 return 1;
1109 
1110         } else  {
1111                 long err;
1112                 pgoff_t idx = vma_hugecache_offset(h, vma, addr);
1113                 struct resv_map *reservations = vma_resv_map(vma);
1114 
1115                 err = region_chg(&reservations->regions, idx, idx + 1);
1116                 if (err < 0)
1117                         return err;
1118                 return 0;
1119         }
1120 }
1121 static void vma_commit_reservation(struct hstate *h,
1122                         struct vm_area_struct *vma, unsigned long addr)
1123 {
1124         struct address_space *mapping = vma->vm_file->f_mapping;
1125         struct inode *inode = mapping->host;
1126 
1127         if (vma->vm_flags & VM_MAYSHARE) {
1128                 pgoff_t idx = vma_hugecache_offset(h, vma, addr);
1129                 region_add(&inode->i_mapping->private_list, idx, idx + 1);
1130 
1131         } else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
1132                 pgoff_t idx = vma_hugecache_offset(h, vma, addr);
1133                 struct resv_map *reservations = vma_resv_map(vma);
1134 
1135                 /* Mark this page used in the map. */
1136                 region_add(&reservations->regions, idx, idx + 1);
1137         }
1138 }
1139 
1140 static struct page *alloc_huge_page(struct vm_area_struct *vma,
1141                                     unsigned long addr, int avoid_reserve)
1142 {
1143         struct hugepage_subpool *spool = subpool_vma(vma);
1144         struct hstate *h = hstate_vma(vma);
1145         struct page *page;
1146         long chg;
1147 
1148         /*
1149          * Processes that did not create the mapping will have no
1150          * reserves and will not have accounted against subpool
1151          * limit. Check that the subpool limit can be made before
1152          * satisfying the allocation MAP_NORESERVE mappings may also
1153          * need pages and subpool limit allocated allocated if no reserve
1154          * mapping overlaps.
1155          */
1156         chg = vma_needs_reservation(h, vma, addr);
1157         if (chg < 0)
1158                 return ERR_PTR(-VM_FAULT_OOM);
1159         if (chg)
1160                 if (hugepage_subpool_get_pages(spool, chg))
1161                         return ERR_PTR(-VM_FAULT_SIGBUS);
1162 
1163         spin_lock(&hugetlb_lock);
1164         page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve);
1165         spin_unlock(&hugetlb_lock);
1166 
1167         if (!page) {
1168                 page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
1169                 if (!page) {
1170                         hugepage_subpool_put_pages(spool, chg);
1171                         return ERR_PTR(-VM_FAULT_SIGBUS);
1172                 }
1173         }
1174 
1175         set_page_private(page, (unsigned long)spool);
1176 
1177         vma_commit_reservation(h, vma, addr);
1178 
1179         return page;
1180 }
1181 
1182 int __weak alloc_bootmem_huge_page(struct hstate *h)
1183 {
1184         struct huge_bootmem_page *m;
1185         int nr_nodes = nodes_weight(node_states[N_HIGH_MEMORY]);
1186 
1187         while (nr_nodes) {
1188                 void *addr;
1189 
1190                 addr = __alloc_bootmem_node_nopanic(
1191                                 NODE_DATA(hstate_next_node_to_alloc(h,
1192                                                 &node_states[N_HIGH_MEMORY])),
1193                                 huge_page_size(h), huge_page_size(h), 0);
1194 
1195                 if (addr) {
1196                         /*
1197                          * Use the beginning of the huge page to store the
1198                          * huge_bootmem_page struct (until gather_bootmem
1199                          * puts them into the mem_map).
1200                          */
1201                         m = addr;
1202                         goto found;
1203                 }
1204                 nr_nodes--;
1205         }
1206         return 0;
1207 
1208 found:
1209         BUG_ON((unsigned long)virt_to_phys(m) & (huge_page_size(h) - 1));
1210         /* Put them into a private list first because mem_map is not up yet */
1211         list_add(&m->list, &huge_boot_pages);
1212         m->hstate = h;
1213         return 1;
1214 }
1215 
1216 static void prep_compound_huge_page(struct page *page, int order)
1217 {
1218         if (unlikely(order > (MAX_ORDER - 1)))
1219                 prep_compound_gigantic_page(page, order);
1220         else
1221                 prep_compound_page(page, order);
1222 }
1223 
1224 /* Put bootmem huge pages into the standard lists after mem_map is up */
1225 static void __init gather_bootmem_prealloc(void)
1226 {
1227         struct huge_bootmem_page *m;
1228 
1229         list_for_each_entry(m, &huge_boot_pages, list) {
1230                 struct hstate *h = m->hstate;
1231                 struct page *page;
1232 
1233 #ifdef CONFIG_HIGHMEM
1234                 page = pfn_to_page(m->phys >> PAGE_SHIFT);
1235                 free_bootmem_late((unsigned long)m,
1236                                   sizeof(struct huge_bootmem_page));
1237 #else
1238                 page = virt_to_page(m);
1239 #endif
1240                 __ClearPageReserved(page);
1241                 WARN_ON(page_count(page) != 1);
1242                 prep_compound_huge_page(page, h->order);
1243                 prep_new_huge_page(h, page, page_to_nid(page));
1244                 /*
1245                  * If we had gigantic hugepages allocated at boot time, we need
1246                  * to restore the 'stolen' pages to totalram_pages in order to
1247                  * fix confusing memory reports from free(1) and another
1248                  * side-effects, like CommitLimit going negative.
1249                  */
1250                 if (h->order > (MAX_ORDER - 1))
1251                         totalram_pages += 1 << h->order;
1252         }
1253 }
1254 
1255 static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
1256 {
1257         unsigned long i;
1258 
1259         for (i = 0; i < h->max_huge_pages; ++i) {
1260                 if (h->order >= MAX_ORDER) {
1261                         if (!alloc_bootmem_huge_page(h))
1262                                 break;
1263                 } else if (!alloc_fresh_huge_page(h,
1264                                          &node_states[N_HIGH_MEMORY]))
1265                         break;
1266         }
1267         h->max_huge_pages = i;
1268 }
1269 
1270 static void __init hugetlb_init_hstates(void)
1271 {
1272         struct hstate *h;
1273 
1274         for_each_hstate(h) {
1275                 /* oversize hugepages were init'ed in early boot */
1276                 if (h->order < MAX_ORDER)
1277                         hugetlb_hstate_alloc_pages(h);
1278         }
1279 }
1280 
1281 static char * __init memfmt(char *buf, unsigned long n)
1282 {
1283         if (n >= (1UL << 30))
1284                 sprintf(buf, "%lu GB", n >> 30);
1285         else if (n >= (1UL << 20))
1286                 sprintf(buf, "%lu MB", n >> 20);
1287         else
1288                 sprintf(buf, "%lu KB", n >> 10);
1289         return buf;
1290 }
1291 
1292 static void __init report_hugepages(void)
1293 {
1294         struct hstate *h;
1295 
1296         for_each_hstate(h) {
1297                 char buf[32];
1298                 printk(KERN_INFO "HugeTLB registered %s page size, "
1299                                  "pre-allocated %ld pages\n",
1300                         memfmt(buf, huge_page_size(h)),
1301                         h->free_huge_pages);
1302         }
1303 }
1304 
1305 #ifdef CONFIG_HIGHMEM
1306 static void try_to_free_low(struct hstate *h, unsigned long count,
1307                                                 nodemask_t *nodes_allowed)
1308 {
1309         int i;
1310 
1311         if (h->order >= MAX_ORDER)
1312                 return;
1313 
1314         for_each_node_mask(i, *nodes_allowed) {
1315                 struct page *page, *next;
1316                 struct list_head *freel = &h->hugepage_freelists[i];
1317                 list_for_each_entry_safe(page, next, freel, lru) {
1318                         if (count >= h->nr_huge_pages)
1319                                 return;
1320                         if (PageHighMem(page))
1321                                 continue;
1322                         list_del(&page->lru);
1323                         update_and_free_page(h, page);
1324                         h->free_huge_pages--;
1325                         h->free_huge_pages_node[page_to_nid(page)]--;
1326                 }
1327         }
1328 }
1329 #else
1330 static inline void try_to_free_low(struct hstate *h, unsigned long count,
1331                                                 nodemask_t *nodes_allowed)
1332 {
1333 }
1334 #endif
1335 
1336 /*
1337  * Increment or decrement surplus_huge_pages.  Keep node-specific counters
1338  * balanced by operating on them in a round-robin fashion.
1339  * Returns 1 if an adjustment was made.
1340  */
1341 static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
1342                                 int delta)
1343 {
1344         int start_nid, next_nid;
1345         int ret = 0;
1346 
1347         VM_BUG_ON(delta != -1 && delta != 1);
1348 
1349         if (delta < 0)
1350                 start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
1351         else
1352                 start_nid = hstate_next_node_to_free(h, nodes_allowed);
1353         next_nid = start_nid;
1354 
1355         do {
1356                 int nid = next_nid;
1357                 if (delta < 0)  {
1358                         /*
1359                          * To shrink on this node, there must be a surplus page
1360                          */
1361                         if (!h->surplus_huge_pages_node[nid]) {
1362                                 next_nid = hstate_next_node_to_alloc(h,
1363                                                                 nodes_allowed);
1364                                 continue;
1365                         }
1366                 }
1367                 if (delta > 0) {
1368                         /*
1369                          * Surplus cannot exceed the total number of pages
1370                          */
1371                         if (h->surplus_huge_pages_node[nid] >=
1372                                                 h->nr_huge_pages_node[nid]) {
1373                                 next_nid = hstate_next_node_to_free(h,
1374                                                                 nodes_allowed);
1375                                 continue;
1376                         }
1377                 }
1378 
1379                 h->surplus_huge_pages += delta;
1380                 h->surplus_huge_pages_node[nid] += delta;
1381                 ret = 1;
1382                 break;
1383         } while (next_nid != start_nid);
1384 
1385         return ret;
1386 }
1387 
1388 #define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
1389 static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
1390                                                 nodemask_t *nodes_allowed)
1391 {
1392         unsigned long min_count, ret;
1393 
1394         if (h->order >= MAX_ORDER)
1395                 return h->max_huge_pages;
1396 
1397         /*
1398          * Increase the pool size
1399          * First take pages out of surplus state.  Then make up the
1400          * remaining difference by allocating fresh huge pages.
1401          *
1402          * We might race with alloc_buddy_huge_page() here and be unable
1403          * to convert a surplus huge page to a normal huge page. That is
1404          * not critical, though, it just means the overall size of the
1405          * pool might be one hugepage larger than it needs to be, but
1406          * within all the constraints specified by the sysctls.
1407          */
1408         spin_lock(&hugetlb_lock);
1409         while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
1410                 if (!adjust_pool_surplus(h, nodes_allowed, -1))
1411                         break;
1412         }
1413 
1414         while (count > persistent_huge_pages(h)) {
1415                 /*
1416                  * If this allocation races such that we no longer need the
1417                  * page, free_huge_page will handle it by freeing the page
1418                  * and reducing the surplus.
1419                  */
1420                 spin_unlock(&hugetlb_lock);
1421 
1422                 /* yield cpu to avoid soft lockup */
1423                 cond_resched();
1424 
1425                 ret = alloc_fresh_huge_page(h, nodes_allowed);
1426                 spin_lock(&hugetlb_lock);
1427                 if (!ret)
1428                         goto out;
1429 
1430                 /* Bail for signals. Probably ctrl-c from user */
1431                 if (signal_pending(current))
1432                         goto out;
1433         }
1434 
1435         /*
1436          * Decrease the pool size
1437          * First return free pages to the buddy allocator (being careful
1438          * to keep enough around to satisfy reservations).  Then place
1439          * pages into surplus state as needed so the pool will shrink
1440          * to the desired size as pages become free.
1441          *
1442          * By placing pages into the surplus state independent of the
1443          * overcommit value, we are allowing the surplus pool size to
1444          * exceed overcommit. There are few sane options here. Since
1445          * alloc_buddy_huge_page() is checking the global counter,
1446          * though, we'll note that we're not allowed to exceed surplus
1447          * and won't grow the pool anywhere else. Not until one of the
1448          * sysctls are changed, or the surplus pages go out of use.
1449          */
1450         min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;
1451         min_count = max(count, min_count);
1452         try_to_free_low(h, min_count, nodes_allowed);
1453         while (min_count < persistent_huge_pages(h)) {
1454                 if (!free_pool_huge_page(h, nodes_allowed, 0))
1455                         break;
1456                 cond_resched_lock(&hugetlb_lock);
1457         }
1458         while (count < persistent_huge_pages(h)) {
1459                 if (!adjust_pool_surplus(h, nodes_allowed, 1))
1460                         break;
1461         }
1462 out:
1463         ret = persistent_huge_pages(h);
1464         spin_unlock(&hugetlb_lock);
1465         return ret;
1466 }
1467 
1468 #define HSTATE_ATTR_RO(_name) \
1469         static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
1470 
1471 #define HSTATE_ATTR(_name) \
1472         static struct kobj_attribute _name##_attr = \
1473                 __ATTR(_name, 0644, _name##_show, _name##_store)
1474 
1475 static struct kobject *hugepages_kobj;
1476 static struct kobject *hstate_kobjs[HUGE_MAX_HSTATE];
1477 
1478 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp);
1479 
1480 static struct hstate *kobj_to_hstate(struct kobject *kobj, int *nidp)
1481 {
1482         int i;
1483 
1484         for (i = 0; i < HUGE_MAX_HSTATE; i++)
1485                 if (hstate_kobjs[i] == kobj) {
1486                         if (nidp)
1487                                 *nidp = NUMA_NO_NODE;
1488                         return &hstates[i];
1489                 }
1490 
1491         return kobj_to_node_hstate(kobj, nidp);
1492 }
1493 
1494 static ssize_t nr_hugepages_show_common(struct kobject *kobj,
1495                                         struct kobj_attribute *attr, char *buf)
1496 {
1497         struct hstate *h;
1498         unsigned long nr_huge_pages;
1499         int nid;
1500 
1501         h = kobj_to_hstate(kobj, &nid);
1502         if (nid == NUMA_NO_NODE)
1503                 nr_huge_pages = h->nr_huge_pages;
1504         else
1505                 nr_huge_pages = h->nr_huge_pages_node[nid];
1506 
1507         return sprintf(buf, "%lu\n", nr_huge_pages);
1508 }
1509 
1510 static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
1511                         struct kobject *kobj, struct kobj_attribute *attr,
1512                         const char *buf, size_t len)
1513 {
1514         int err;
1515         int nid;
1516         unsigned long count;
1517         struct hstate *h;
1518         NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
1519 
1520         err = strict_strtoul(buf, 10, &count);
1521         if (err)
1522                 goto out;
1523 
1524         h = kobj_to_hstate(kobj, &nid);
1525         if (h->order >= MAX_ORDER) {
1526                 err = -EINVAL;
1527                 goto out;
1528         }
1529 
1530         if (nid == NUMA_NO_NODE) {
1531                 /*
1532                  * global hstate attribute
1533                  */
1534                 if (!(obey_mempolicy &&
1535                                 init_nodemask_of_mempolicy(nodes_allowed))) {
1536                         NODEMASK_FREE(nodes_allowed);
1537                         nodes_allowed = &node_states[N_HIGH_MEMORY];
1538                 }
1539         } else if (nodes_allowed) {
1540                 /*
1541                  * per node hstate attribute: adjust count to global,
1542                  * but restrict alloc/free to the specified node.
1543                  */
1544                 count += h->nr_huge_pages - h->nr_huge_pages_node[nid];
1545                 init_nodemask_of_node(nodes_allowed, nid);
1546         } else
1547                 nodes_allowed = &node_states[N_HIGH_MEMORY];
1548 
1549         h->max_huge_pages = set_max_huge_pages(h, count, nodes_allowed);
1550 
1551         if (nodes_allowed != &node_states[N_HIGH_MEMORY])
1552                 NODEMASK_FREE(nodes_allowed);
1553 
1554         return len;
1555 out:
1556         NODEMASK_FREE(nodes_allowed);
1557         return err;
1558 }
1559 
1560 static ssize_t nr_hugepages_show(struct kobject *kobj,
1561                                        struct kobj_attribute *attr, char *buf)
1562 {
1563         return nr_hugepages_show_common(kobj, attr, buf);
1564 }
1565 
1566 static ssize_t nr_hugepages_store(struct kobject *kobj,
1567                struct kobj_attribute *attr, const char *buf, size_t len)
1568 {
1569         return nr_hugepages_store_common(false, kobj, attr, buf, len);
1570 }
1571 HSTATE_ATTR(nr_hugepages);
1572 
1573 #ifdef CONFIG_NUMA
1574 
1575 /*
1576  * hstate attribute for optionally mempolicy-based constraint on persistent
1577  * huge page alloc/free.
1578  */
1579 static ssize_t nr_hugepages_mempolicy_show(struct kobject *kobj,
1580                                        struct kobj_attribute *attr, char *buf)
1581 {
1582         return nr_hugepages_show_common(kobj, attr, buf);
1583 }
1584 
1585 static ssize_t nr_hugepages_mempolicy_store(struct kobject *kobj,
1586                struct kobj_attribute *attr, const char *buf, size_t len)
1587 {
1588         return nr_hugepages_store_common(true, kobj, attr, buf, len);
1589 }
1590 HSTATE_ATTR(nr_hugepages_mempolicy);
1591 #endif
1592 
1593 
1594 static ssize_t nr_overcommit_hugepages_show(struct kobject *kobj,
1595                                         struct kobj_attribute *attr, char *buf)
1596 {
1597         struct hstate *h = kobj_to_hstate(kobj, NULL);
1598         return sprintf(buf, "%lu\n", h->nr_overcommit_huge_pages);
1599 }
1600 
1601 static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
1602                 struct kobj_attribute *attr, const char *buf, size_t count)
1603 {
1604         int err;
1605         unsigned long input;
1606         struct hstate *h = kobj_to_hstate(kobj, NULL);
1607 
1608         if (h->order >= MAX_ORDER)
1609                 return -EINVAL;
1610 
1611         err = strict_strtoul(buf, 10, &input);
1612         if (err)
1613                 return err;
1614 
1615         spin_lock(&hugetlb_lock);
1616         h->nr_overcommit_huge_pages = input;
1617         spin_unlock(&hugetlb_lock);
1618 
1619         return count;
1620 }
1621 HSTATE_ATTR(nr_overcommit_hugepages);
1622 
1623 static ssize_t free_hugepages_show(struct kobject *kobj,
1624                                         struct kobj_attribute *attr, char *buf)
1625 {
1626         struct hstate *h;
1627         unsigned long free_huge_pages;
1628         int nid;
1629 
1630         h = kobj_to_hstate(kobj, &nid);
1631         if (nid == NUMA_NO_NODE)
1632                 free_huge_pages = h->free_huge_pages;
1633         else
1634                 free_huge_pages = h->free_huge_pages_node[nid];
1635 
1636         return sprintf(buf, "%lu\n", free_huge_pages);
1637 }
1638 HSTATE_ATTR_RO(free_hugepages);
1639 
1640 static ssize_t resv_hugepages_show(struct kobject *kobj,
1641                                         struct kobj_attribute *attr, char *buf)
1642 {
1643         struct hstate *h = kobj_to_hstate(kobj, NULL);
1644         return sprintf(buf, "%lu\n", h->resv_huge_pages);
1645 }
1646 HSTATE_ATTR_RO(resv_hugepages);
1647 
1648 static ssize_t surplus_hugepages_show(struct kobject *kobj,
1649                                         struct kobj_attribute *attr, char *buf)
1650 {
1651         struct hstate *h;
1652         unsigned long surplus_huge_pages;
1653         int nid;
1654 
1655         h = kobj_to_hstate(kobj, &nid);
1656         if (nid == NUMA_NO_NODE)
1657                 surplus_huge_pages = h->surplus_huge_pages;
1658         else
1659                 surplus_huge_pages = h->surplus_huge_pages_node[nid];
1660 
1661         return sprintf(buf, "%lu\n", surplus_huge_pages);
1662 }
1663 HSTATE_ATTR_RO(surplus_hugepages);
1664 
1665 static struct attribute *hstate_attrs[] = {
1666         &nr_hugepages_attr.attr,
1667         &nr_overcommit_hugepages_attr.attr,
1668         &free_hugepages_attr.attr,
1669         &resv_hugepages_attr.attr,
1670         &surplus_hugepages_attr.attr,
1671 #ifdef CONFIG_NUMA
1672         &nr_hugepages_mempolicy_attr.attr,
1673 #endif
1674         NULL,
1675 };
1676 
1677 static struct attribute_group hstate_attr_group = {
1678         .attrs = hstate_attrs,
1679 };
1680 
1681 static int hugetlb_sysfs_add_hstate(struct hstate *h, struct kobject *parent,
1682                                     struct kobject **hstate_kobjs,
1683                                     struct attribute_group *hstate_attr_group)
1684 {
1685         int retval;
1686         int hi = h - hstates;
1687 
1688         hstate_kobjs[hi] = kobject_create_and_add(h->name, parent);
1689         if (!hstate_kobjs[hi])
1690                 return -ENOMEM;
1691 
1692         retval = sysfs_create_group(hstate_kobjs[hi], hstate_attr_group);
1693         if (retval)
1694                 kobject_put(hstate_kobjs[hi]);
1695 
1696         return retval;
1697 }
1698 
1699 static void __init hugetlb_sysfs_init(void)
1700 {
1701         struct hstate *h;
1702         int err;
1703 
1704         hugepages_kobj = kobject_create_and_add("hugepages", mm_kobj);
1705         if (!hugepages_kobj)
1706                 return;
1707 
1708         for_each_hstate(h) {
1709                 err = hugetlb_sysfs_add_hstate(h, hugepages_kobj,
1710                                          hstate_kobjs, &hstate_attr_group);
1711                 if (err)
1712                         printk(KERN_ERR "Hugetlb: Unable to add hstate %s",
1713                                                                 h->name);
1714         }
1715 }
1716 
1717 #ifdef CONFIG_NUMA
1718 
1719 /*
1720  * node_hstate/s - associate per node hstate attributes, via their kobjects,
1721  * with node sysdevs in node_devices[] using a parallel array.  The array
1722  * index of a node sysdev or _hstate == node id.
1723  * This is here to avoid any static dependency of the node sysdev driver, in
1724  * the base kernel, on the hugetlb module.
1725  */
1726 struct node_hstate {
1727         struct kobject          *hugepages_kobj;
1728         struct kobject          *hstate_kobjs[HUGE_MAX_HSTATE];
1729 };
1730 struct node_hstate node_hstates[MAX_NUMNODES];
1731 
1732 /*
1733  * A subset of global hstate attributes for node sysdevs
1734  */
1735 static struct attribute *per_node_hstate_attrs[] = {
1736         &nr_hugepages_attr.attr,
1737         &free_hugepages_attr.attr,
1738         &surplus_hugepages_attr.attr,
1739         NULL,
1740 };
1741 
1742 static struct attribute_group per_node_hstate_attr_group = {
1743         .attrs = per_node_hstate_attrs,
1744 };
1745 
1746 /*
1747  * kobj_to_node_hstate - lookup global hstate for node sysdev hstate attr kobj.
1748  * Returns node id via non-NULL nidp.
1749  */
1750 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
1751 {
1752         int nid;
1753 
1754         for (nid = 0; nid < nr_node_ids; nid++) {
1755                 struct node_hstate *nhs = &node_hstates[nid];
1756                 int i;
1757                 for (i = 0; i < HUGE_MAX_HSTATE; i++)
1758                         if (nhs->hstate_kobjs[i] == kobj) {
1759                                 if (nidp)
1760                                         *nidp = nid;
1761                                 return &hstates[i];
1762                         }
1763         }
1764 
1765         BUG();
1766         return NULL;
1767 }
1768 
1769 /*
1770  * Unregister hstate attributes from a single node sysdev.
1771  * No-op if no hstate attributes attached.
1772  */
1773 void hugetlb_unregister_node(struct node *node)
1774 {
1775         struct hstate *h;
1776         struct node_hstate *nhs = &node_hstates[node->sysdev.id];
1777 
1778         if (!nhs->hugepages_kobj)
1779                 return;         /* no hstate attributes */
1780 
1781         for_each_hstate(h)
1782                 if (nhs->hstate_kobjs[h - hstates]) {
1783                         kobject_put(nhs->hstate_kobjs[h - hstates]);
1784                         nhs->hstate_kobjs[h - hstates] = NULL;
1785                 }
1786 
1787         kobject_put(nhs->hugepages_kobj);
1788         nhs->hugepages_kobj = NULL;
1789 }
1790 
1791 /*
1792  * hugetlb module exit:  unregister hstate attributes from node sysdevs
1793  * that have them.
1794  */
1795 static void hugetlb_unregister_all_nodes(void)
1796 {
1797         int nid;
1798 
1799         /*
1800          * disable node sysdev registrations.
1801          */
1802         register_hugetlbfs_with_node(NULL, NULL);
1803 
1804         /*
1805          * remove hstate attributes from any nodes that have them.
1806          */
1807         for (nid = 0; nid < nr_node_ids; nid++)
1808                 hugetlb_unregister_node(&node_devices[nid]);
1809 }
1810 
1811 /*
1812  * Register hstate attributes for a single node sysdev.
1813  * No-op if attributes already registered.
1814  */
1815 void hugetlb_register_node(struct node *node)
1816 {
1817         struct hstate *h;
1818         struct node_hstate *nhs = &node_hstates[node->sysdev.id];
1819         int err;
1820 
1821         if (nhs->hugepages_kobj)
1822                 return;         /* already allocated */
1823 
1824         nhs->hugepages_kobj = kobject_create_and_add("hugepages",
1825                                                         &node->sysdev.kobj);
1826         if (!nhs->hugepages_kobj)
1827                 return;
1828 
1829         for_each_hstate(h) {
1830                 err = hugetlb_sysfs_add_hstate(h, nhs->hugepages_kobj,
1831                                                 nhs->hstate_kobjs,
1832                                                 &per_node_hstate_attr_group);
1833                 if (err) {
1834                         printk(KERN_ERR "Hugetlb: Unable to add hstate %s"
1835                                         " for node %d\n",
1836                                                 h->name, node->sysdev.id);
1837                         hugetlb_unregister_node(node);
1838                         break;
1839                 }
1840         }
1841 }
1842 
1843 /*
1844  * hugetlb init time:  register hstate attributes for all registered node
1845  * sysdevs of nodes that have memory.  All on-line nodes should have
1846  * registered their associated sysdev by this time.
1847  */
1848 static void hugetlb_register_all_nodes(void)
1849 {
1850         int nid;
1851 
1852         for_each_node_state(nid, N_HIGH_MEMORY) {
1853                 struct node *node = &node_devices[nid];
1854                 if (node->sysdev.id == nid)
1855                         hugetlb_register_node(node);
1856         }
1857 
1858         /*
1859          * Let the node sysdev driver know we're here so it can
1860          * [un]register hstate attributes on node hotplug.
1861          */
1862         register_hugetlbfs_with_node(hugetlb_register_node,
1863                                      hugetlb_unregister_node);
1864 }
1865 #else   /* !CONFIG_NUMA */
1866 
1867 static struct hstate *kobj_to_node_hstate(struct kobject *kobj, int *nidp)
1868 {
1869         BUG();
1870         if (nidp)
1871                 *nidp = -1;
1872         return NULL;
1873 }
1874 
1875 static void hugetlb_unregister_all_nodes(void) { }
1876 
1877 static void hugetlb_register_all_nodes(void) { }
1878 
1879 #endif
1880 
1881 static void __exit hugetlb_exit(void)
1882 {
1883         struct hstate *h;
1884 
1885         hugetlb_unregister_all_nodes();
1886 
1887         for_each_hstate(h) {
1888                 kobject_put(hstate_kobjs[h - hstates]);
1889         }
1890 
1891         kobject_put(hugepages_kobj);
1892 }
1893 module_exit(hugetlb_exit);
1894 
1895 static int __init hugetlb_init(void)
1896 {
1897         if (!hugepages_supported())
1898                 return 0;
1899 
1900         if (!size_to_hstate(default_hstate_size)) {
1901                 default_hstate_size = HPAGE_SIZE;
1902                 if (!size_to_hstate(default_hstate_size))
1903                         hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
1904         }
1905         default_hstate_idx = size_to_hstate(default_hstate_size) - hstates;
1906         if (default_hstate_max_huge_pages)
1907                 default_hstate.max_huge_pages = default_hstate_max_huge_pages;
1908 
1909         hugetlb_init_hstates();
1910 
1911         gather_bootmem_prealloc();
1912 
1913         report_hugepages();
1914 
1915         hugetlb_sysfs_init();
1916 
1917         hugetlb_register_all_nodes();
1918 
1919         return 0;
1920 }
1921 module_init(hugetlb_init);
1922 
1923 /* Should be called on processing a hugepagesz=... option */
1924 void __init hugetlb_add_hstate(unsigned order)
1925 {
1926         struct hstate *h;
1927         unsigned long i;
1928 
1929         if (size_to_hstate(PAGE_SIZE << order)) {
1930                 printk(KERN_WARNING "hugepagesz= specified twice, ignoring\n");
1931                 return;
1932         }
1933         BUG_ON(max_hstate >= HUGE_MAX_HSTATE);
1934         BUG_ON(order == 0);
1935         h = &hstates[max_hstate++];
1936         h->order = order;
1937         h->mask = ~((1ULL << (order + PAGE_SHIFT)) - 1);
1938         h->nr_huge_pages = 0;
1939         h->free_huge_pages = 0;
1940         for (i = 0; i < MAX_NUMNODES; ++i)
1941                 INIT_LIST_HEAD(&h->hugepage_freelists[i]);
1942         h->next_nid_to_alloc = first_node(node_states[N_HIGH_MEMORY]);
1943         h->next_nid_to_free = first_node(node_states[N_HIGH_MEMORY]);
1944         snprintf(h->name, HSTATE_NAME_LEN, "hugepages-%lukB",
1945                                         huge_page_size(h)/1024);
1946 
1947         parsed_hstate = h;
1948 }
1949 
1950 static int __init hugetlb_nrpages_setup(char *s)
1951 {
1952         unsigned long *mhp;
1953         static unsigned long *last_mhp;
1954 
1955         /*
1956          * !max_hstate means we haven't parsed a hugepagesz= parameter yet,
1957          * so this hugepages= parameter goes to the "default hstate".
1958          */
1959         if (!max_hstate)
1960                 mhp = &default_hstate_max_huge_pages;
1961         else
1962                 mhp = &parsed_hstate->max_huge_pages;
1963 
1964         if (mhp == last_mhp) {
1965                 printk(KERN_WARNING "hugepages= specified twice without "
1966                         "interleaving hugepagesz=, ignoring\n");
1967                 return 1;
1968         }
1969 
1970         if (sscanf(s, "%lu", mhp) <= 0)
1971                 *mhp = 0;
1972 
1973         /*
1974          * Global state is always initialized later in hugetlb_init.
1975          * But we need to allocate >= MAX_ORDER hstates here early to still
1976          * use the bootmem allocator.
1977          */
1978         if (max_hstate && parsed_hstate->order >= MAX_ORDER)
1979                 hugetlb_hstate_alloc_pages(parsed_hstate);
1980 
1981         last_mhp = mhp;
1982 
1983         return 1;
1984 }
1985 __setup("hugepages=", hugetlb_nrpages_setup);
1986 
1987 static int __init hugetlb_default_setup(char *s)
1988 {
1989         default_hstate_size = memparse(s, &s);
1990         return 1;
1991 }
1992 __setup("default_hugepagesz=", hugetlb_default_setup);
1993 
1994 static unsigned int cpuset_mems_nr(unsigned int *array)
1995 {
1996         int node;
1997         unsigned int nr = 0;
1998 
1999         for_each_node_mask(node, cpuset_current_mems_allowed)
2000                 nr += array[node];
2001 
2002         return nr;
2003 }
2004 
2005 #ifdef CONFIG_SYSCTL
2006 static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
2007                          struct ctl_table *table, int write,
2008                          void __user *buffer, size_t *length, loff_t *ppos)
2009 {
2010         struct hstate *h = &default_hstate;
2011         unsigned long tmp;
2012         int ret;
2013 
2014         if (!hugepages_supported())
2015                 return -ENOTSUPP;
2016 
2017         tmp = h->max_huge_pages;
2018 
2019         if (write && h->order >= MAX_ORDER)
2020                 return -EINVAL;
2021 
2022         table->data = &tmp;
2023         table->maxlen = sizeof(unsigned long);
2024         ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
2025         if (ret)
2026                 goto out;
2027 
2028         if (write) {
2029                 NODEMASK_ALLOC(nodemask_t, nodes_allowed,
2030                                                 GFP_KERNEL | __GFP_NORETRY);
2031                 if (!(obey_mempolicy &&
2032                                init_nodemask_of_mempolicy(nodes_allowed))) {
2033                         NODEMASK_FREE(nodes_allowed);
2034                         nodes_allowed = &node_states[N_HIGH_MEMORY];
2035                 }
2036                 h->max_huge_pages = set_max_huge_pages(h, tmp, nodes_allowed);
2037 
2038                 if (nodes_allowed != &node_states[N_HIGH_MEMORY])
2039                         NODEMASK_FREE(nodes_allowed);
2040         }
2041 out:
2042         return ret;
2043 }
2044 
2045 int hugetlb_sysctl_handler(struct ctl_table *table, int write,
2046                           void __user *buffer, size_t *length, loff_t *ppos)
2047 {
2048 
2049         return hugetlb_sysctl_handler_common(false, table, write,
2050                                                         buffer, length, ppos);
2051 }
2052 
2053 #ifdef CONFIG_NUMA
2054 int hugetlb_mempolicy_sysctl_handler(struct ctl_table *table, int write,
2055                           void __user *buffer, size_t *length, loff_t *ppos)
2056 {
2057         return hugetlb_sysctl_handler_common(true, table, write,
2058                                                         buffer, length, ppos);
2059 }
2060 #endif /* CONFIG_NUMA */
2061 
2062 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
2063                         void __user *buffer,
2064                         size_t *length, loff_t *ppos)
2065 {
2066         proc_dointvec(table, write, buffer, length, ppos);
2067         if (hugepages_treat_as_movable)
2068                 htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
2069         else
2070                 htlb_alloc_mask = GFP_HIGHUSER;
2071         return 0;
2072 }
2073 
2074 int hugetlb_overcommit_handler(struct ctl_table *table, int write,
2075                         void __user *buffer,
2076                         size_t *length, loff_t *ppos)
2077 {
2078         struct hstate *h = &default_hstate;
2079         unsigned long tmp;
2080         int ret;
2081 
2082         if (!hugepages_supported())
2083                 return -ENOTSUPP;
2084 
2085         tmp = h->nr_overcommit_huge_pages;
2086 
2087         if (write && h->order >= MAX_ORDER)
2088                 return -EINVAL;
2089 
2090         table->data = &tmp;
2091         table->maxlen = sizeof(unsigned long);
2092         ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
2093         if (ret)
2094                 goto out;
2095 
2096         if (write) {
2097                 spin_lock(&hugetlb_lock);
2098                 h->nr_overcommit_huge_pages = tmp;
2099                 spin_unlock(&hugetlb_lock);
2100         }
2101 out:
2102         return ret;
2103 }
2104 
2105 #endif /* CONFIG_SYSCTL */
2106 
2107 void hugetlb_report_meminfo(struct seq_file *m)
2108 {
2109         struct hstate *h = &default_hstate;
2110         if (!hugepages_supported())
2111                 return;
2112         seq_printf(m,
2113                         "HugePages_Total:   %5lu\n"
2114                         "HugePages_Free:    %5lu\n"
2115                         "HugePages_Rsvd:    %5lu\n"
2116                         "HugePages_Surp:    %5lu\n"
2117                         "Hugepagesize:   %8lu kB\n",
2118                         h->nr_huge_pages,
2119                         h->free_huge_pages,
2120                         h->resv_huge_pages,
2121                         h->surplus_huge_pages,
2122                         1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
2123 }
2124 
2125 int hugetlb_report_node_meminfo(int nid, char *buf)
2126 {
2127         struct hstate *h = &default_hstate;
2128         if (!hugepages_supported())
2129                 return 0;
2130         return sprintf(buf,
2131                 "Node %d HugePages_Total: %5u\n"
2132                 "Node %d HugePages_Free:  %5u\n"
2133                 "Node %d HugePages_Surp:  %5u\n",
2134                 nid, h->nr_huge_pages_node[nid],
2135                 nid, h->free_huge_pages_node[nid],
2136                 nid, h->surplus_huge_pages_node[nid]);
2137 }
2138 
2139 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
2140 unsigned long hugetlb_total_pages(void)
2141 {
2142         struct hstate *h;
2143         unsigned long nr_total_pages = 0;
2144 
2145         for_each_hstate(h)
2146                 nr_total_pages += h->nr_huge_pages * pages_per_huge_page(h);
2147         return nr_total_pages;
2148 }
2149 
2150 static int hugetlb_acct_memory(struct hstate *h, long delta)
2151 {
2152         int ret = -ENOMEM;
2153 
2154         spin_lock(&hugetlb_lock);
2155         /*
2156          * When cpuset is configured, it breaks the strict hugetlb page
2157          * reservation as the accounting is done on a global variable. Such
2158          * reservation is completely rubbish in the presence of cpuset because
2159          * the reservation is not checked against page availability for the
2160          * current cpuset. Application can still potentially OOM'ed by kernel
2161          * with lack of free htlb page in cpuset that the task is in.
2162          * Attempt to enforce strict accounting with cpuset is almost
2163          * impossible (or too ugly) because cpuset is too fluid that
2164          * task or memory node can be dynamically moved between cpusets.
2165          *
2166          * The change of semantics for shared hugetlb mapping with cpuset is
2167          * undesirable. However, in order to preserve some of the semantics,
2168          * we fall back to check against current free page availability as
2169          * a best attempt and hopefully to minimize the impact of changing
2170          * semantics that cpuset has.
2171          */
2172         if (delta > 0) {
2173                 if (gather_surplus_pages(h, delta) < 0)
2174                         goto out;
2175 
2176                 if (delta > cpuset_mems_nr(h->free_huge_pages_node)) {
2177                         return_unused_surplus_pages(h, delta);
2178                         goto out;
2179                 }
2180         }
2181 
2182         ret = 0;
2183         if (delta < 0)
2184                 return_unused_surplus_pages(h, (unsigned long) -delta);
2185 
2186 out:
2187         spin_unlock(&hugetlb_lock);
2188         return ret;
2189 }
2190 
2191 static void hugetlb_vm_op_open(struct vm_area_struct *vma)
2192 {
2193         struct resv_map *reservations = vma_resv_map(vma);
2194 
2195         /*
2196          * This new VMA should share its siblings reservation map if present.
2197          * The VMA will only ever have a valid reservation map pointer where
2198          * it is being copied for another still existing VMA.  As that VMA
2199          * has a reference to the reservation map it cannot disappear until
2200          * after this open call completes.  It is therefore safe to take a
2201          * new reference here without additional locking.
2202          */
2203         if (reservations)
2204                 kref_get(&reservations->refs);
2205 }
2206 
2207 static void resv_map_put(struct vm_area_struct *vma)
2208 {
2209         struct resv_map *reservations = vma_resv_map(vma);
2210 
2211         if (!reservations)
2212                 return;
2213         kref_put(&reservations->refs, resv_map_release);
2214 }
2215 
2216 static void hugetlb_vm_op_close(struct vm_area_struct *vma)
2217 {
2218         struct hstate *h = hstate_vma(vma);
2219         struct resv_map *reservations = vma_resv_map(vma);
2220         struct hugepage_subpool *spool = subpool_vma(vma);
2221         unsigned long reserve;
2222         unsigned long start;
2223         unsigned long end;
2224 
2225         if (reservations) {
2226                 start = vma_hugecache_offset(h, vma, vma->vm_start);
2227                 end = vma_hugecache_offset(h, vma, vma->vm_end);
2228 
2229                 reserve = (end - start) -
2230                         region_count(&reservations->regions, start, end);
2231 
2232                 resv_map_put(vma);
2233 
2234                 if (reserve) {
2235                         hugetlb_acct_memory(h, -reserve);
2236                         hugepage_subpool_put_pages(spool, reserve);
2237                 }
2238         }
2239 }
2240 
2241 /*
2242  * We cannot handle pagefaults against hugetlb pages at all.  They cause
2243  * handle_mm_fault() to try to instantiate regular-sized pages in the
2244  * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
2245  * this far.
2246  */
2247 static int hugetlb_vm_op_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
2248 {
2249         BUG();
2250         return 0;
2251 }
2252 
2253 const struct vm_operations_struct hugetlb_vm_ops = {
2254         .fault = hugetlb_vm_op_fault,
2255         .open = hugetlb_vm_op_open,
2256         .close = hugetlb_vm_op_close,
2257 };
2258 
2259 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
2260                                 int writable)
2261 {
2262         pte_t entry;
2263 
2264         if (writable) {
2265                 entry =
2266                     pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
2267         } else {
2268                 entry = huge_pte_wrprotect(mk_pte(page, vma->vm_page_prot));
2269         }
2270         entry = pte_mkyoung(entry);
2271         entry = pte_mkhuge(entry);
2272 
2273         return entry;
2274 }
2275 
2276 static void set_huge_ptep_writable(struct vm_area_struct *vma,
2277                                    unsigned long address, pte_t *ptep)
2278 {
2279         pte_t entry;
2280 
2281         entry = pte_mkwrite(pte_mkdirty(huge_ptep_get(ptep)));
2282         if (huge_ptep_set_access_flags(vma, address, ptep, entry, 1))
2283                 update_mmu_cache(vma, address, ptep);
2284 }
2285 
2286 static int is_hugetlb_entry_migration(pte_t pte)
2287 {
2288         swp_entry_t swp;
2289 
2290         if (huge_pte_none(pte) || pte_present(pte))
2291                 return 0;
2292         swp = pte_to_swp_entry(pte);
2293         if (non_swap_entry(swp) && is_migration_entry(swp))
2294                 return 1;
2295         else
2296                 return 0;
2297 }
2298 
2299 static int is_hugetlb_entry_hwpoisoned(pte_t pte)
2300 {
2301         swp_entry_t swp;
2302 
2303         if (huge_pte_none(pte) || pte_present(pte))
2304                 return 0;
2305         swp = pte_to_swp_entry(pte);
2306         if (non_swap_entry(swp) && is_hwpoison_entry(swp))
2307                 return 1;
2308         else
2309                 return 0;
2310 }
2311 
2312 int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
2313                             struct vm_area_struct *vma)
2314 {
2315         pte_t *src_pte, *dst_pte, entry;
2316         struct page *ptepage;
2317         unsigned long addr;
2318         int cow;
2319         struct hstate *h = hstate_vma(vma);
2320         unsigned long sz = huge_page_size(h);
2321 
2322         cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
2323 
2324         for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
2325                 src_pte = huge_pte_offset(src, addr);
2326                 if (!src_pte)
2327                         continue;
2328                 dst_pte = huge_pte_alloc(dst, addr, sz);
2329                 if (!dst_pte)
2330                         goto nomem;
2331 
2332                 /* If the pagetables are shared don't copy or take references */
2333                 if (dst_pte == src_pte)
2334                         continue;
2335 
2336                 spin_lock(&dst->page_table_lock);
2337                 spin_lock_nested(&src->page_table_lock, SINGLE_DEPTH_NESTING);
2338                 entry = huge_ptep_get(src_pte);
2339                 if (huge_pte_none(entry)) { /* skip none entry */
2340                         ;
2341                 } else if (unlikely(is_hugetlb_entry_migration(entry) ||
2342                                     is_hugetlb_entry_hwpoisoned(entry))) {
2343                         swp_entry_t swp_entry = pte_to_swp_entry(entry);
2344 
2345                         if (is_write_migration_entry(swp_entry) && cow) {
2346                                 /*
2347                                  * COW mappings require pages in both
2348                                  * parent and child to be set to read.
2349                                  */
2350                                 make_migration_entry_read(&swp_entry);
2351                                 entry = swp_entry_to_pte(swp_entry);
2352                                 set_huge_pte_at(src, addr, src_pte, entry);
2353                         }
2354                         set_huge_pte_at(dst, addr, dst_pte, entry);
2355                 } else {
2356                         if (cow)
2357                                 huge_ptep_set_wrprotect(src, addr, src_pte);
2358                         entry = huge_ptep_get(src_pte);
2359                         ptepage = pte_page(entry);
2360                         get_page(ptepage);
2361                         page_dup_rmap(ptepage);
2362                         set_huge_pte_at(dst, addr, dst_pte, entry);
2363                 }
2364                 spin_unlock(&src->page_table_lock);
2365                 spin_unlock(&dst->page_table_lock);
2366         }
2367         return 0;
2368 
2369 nomem:
2370         return -ENOMEM;
2371 }
2372 
2373 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
2374                             unsigned long end, struct page *ref_page)
2375 {
2376         struct mm_struct *mm = vma->vm_mm;
2377         unsigned long address;
2378         pte_t *ptep;
2379         pte_t pte;
2380         struct page *page;
2381         struct page *tmp;
2382         struct hstate *h = hstate_vma(vma);
2383         unsigned long sz = huge_page_size(h);
2384 
2385         /*
2386          * A page gathering list, protected by per file i_mmap_mutex. The
2387          * lock is used to avoid list corruption from multiple unmapping
2388          * of the same page since we are using page->lru.
2389          */
2390         LIST_HEAD(page_list);
2391 
2392         WARN_ON(!is_vm_hugetlb_page(vma));
2393         BUG_ON(start & ~huge_page_mask(h));
2394         BUG_ON(end & ~huge_page_mask(h));
2395 
2396         mmu_notifier_invalidate_range_start(mm, start, end);
2397         spin_lock(&mm->page_table_lock);
2398         for (address = start; address < end; address += sz) {
2399                 ptep = huge_pte_offset(mm, address);
2400                 if (!ptep)
2401                         continue;
2402 
2403                 if (huge_pmd_unshare(mm, &address, ptep))
2404                         continue;
2405 
2406                 /*
2407                  * If a reference page is supplied, it is because a specific
2408                  * page is being unmapped, not a range. Ensure the page we
2409                  * are about to unmap is the actual page of interest.
2410                  */
2411                 if (ref_page) {
2412                         pte = huge_ptep_get(ptep);
2413                         if (huge_pte_none(pte))
2414                                 continue;
2415                         page = pte_page(pte);
2416                         if (page != ref_page)
2417                                 continue;
2418 
2419                         /*
2420                          * Mark the VMA as having unmapped its page so that
2421                          * future faults in this VMA will fail rather than
2422                          * looking like data was lost
2423                          */
2424                         set_vma_resv_flags(vma, HPAGE_RESV_UNMAPPED);
2425                 }
2426 
2427                 pte = huge_ptep_get_and_clear(mm, address, ptep);
2428                 if (huge_pte_none(pte))
2429                         continue;
2430 
2431                 /*
2432                  * Migrating hugepage or HWPoisoned hugepage is already
2433                  * unmapped and its refcount is dropped
2434                  */
2435                 if (unlikely(!pte_present(pte)))
2436                         continue;
2437 
2438                 page = pte_page(pte);
2439                 if (pte_dirty(pte))
2440                         set_page_dirty(page);
2441                 list_add(&page->lru, &page_list);
2442         }
2443         spin_unlock(&mm->page_table_lock);
2444         flush_tlb_range(vma, start, end);
2445         mmu_notifier_invalidate_range_end(mm, start, end);
2446         list_for_each_entry_safe(page, tmp, &page_list, lru) {
2447                 page_remove_rmap(page);
2448                 list_del(&page->lru);
2449                 put_page(page);
2450         }
2451 }
2452 
2453 void __unmap_hugepage_range_final(struct vm_area_struct *vma,
2454                           unsigned long start, unsigned long end,
2455                           struct page *ref_page)
2456 {
2457         __unmap_hugepage_range(vma, start, end, ref_page);
2458 
2459         /*
2460          * Clear this flag so that x86's huge_pmd_share page_table_shareable
2461          * test will fail on a vma being torn down, and not grab a page table
2462          * on its way out.  We're lucky that the flag has such an appropriate
2463          * name, and can in fact be safely cleared here. We could clear it
2464          * before the __unmap_hugepage_range above, but all that's necessary
2465          * is to clear it before releasing the i_mmap_mutex. This works
2466          * because in the context this is called, the VMA is about to be
2467          * destroyed and the i_mmap_mutex is held.
2468          */
2469         vma->vm_flags &= ~VM_MAYSHARE;
2470 }
2471 
2472 void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
2473                           unsigned long end, struct page *ref_page)
2474 {
2475         mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
2476         __unmap_hugepage_range(vma, start, end, ref_page);
2477         mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
2478 }
2479 
2480 /*
2481  * This is called when the original mapper is failing to COW a MAP_PRIVATE
2482  * mappping it owns the reserve page for. The intention is to unmap the page
2483  * from other VMAs and let the children be SIGKILLed if they are faulting the
2484  * same region.
2485  */
2486 static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
2487                                 struct page *page, unsigned long address)
2488 {
2489         struct hstate *h = hstate_vma(vma);
2490         struct vm_area_struct *iter_vma;
2491         struct address_space *mapping;
2492         struct prio_tree_iter iter;
2493         pgoff_t pgoff;
2494 
2495         /*
2496          * vm_pgoff is in PAGE_SIZE units, hence the different calculation
2497          * from page cache lookup which is in HPAGE_SIZE units.
2498          */
2499         address = address & huge_page_mask(h);
2500         pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) +
2501                         vma->vm_pgoff;
2502         mapping = vma->vm_file->f_dentry->d_inode->i_mapping;
2503 
2504         /*
2505          * Take the mapping lock for the duration of the table walk. As
2506          * this mapping should be shared between all the VMAs,
2507          * __unmap_hugepage_range() is called as the lock is already held
2508          */
2509         mutex_lock(&mapping->i_mmap_mutex);
2510         vma_prio_tree_foreach(iter_vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
2511                 /* Do not unmap the current VMA */
2512                 if (iter_vma == vma)
2513                         continue;
2514 
2515                 /*
2516                  * Shared VMAs have their own reserves and do not affect
2517                  * MAP_PRIVATE accounting but it is possible that a shared
2518                  * VMA is using the same page so check and skip such VMAs.
2519                  */
2520                 if (iter_vma->vm_flags & VM_MAYSHARE)
2521                         continue;
2522 
2523                 /*
2524                  * Unmap the page from other VMAs without their own reserves.
2525                  * They get marked to be SIGKILLed if they fault in these
2526                  * areas. This is because a future no-page fault on this VMA
2527                  * could insert a zeroed page instead of the data existing
2528                  * from the time of fork. This would look like data corruption
2529                  */
2530                 if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER))
2531                         __unmap_hugepage_range(iter_vma,
2532                                 address, address + huge_page_size(h),
2533                                 page);
2534         }
2535         mutex_unlock(&mapping->i_mmap_mutex);
2536 
2537         return 1;
2538 }
2539 
2540 /*
2541  * Hugetlb_cow() should be called with page lock of the original hugepage held.
2542  */
2543 static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
2544                         unsigned long address, pte_t *ptep, pte_t pte,
2545                         struct page *pagecache_page)
2546 {
2547         struct hstate *h = hstate_vma(vma);
2548         struct page *old_page, *new_page;
2549         int avoidcopy;
2550         int outside_reserve = 0;
2551 
2552         old_page = pte_page(pte);
2553 
2554 retry_avoidcopy:
2555         /* If no-one else is actually using this page, avoid the copy
2556          * and just make the page writable */
2557         avoidcopy = (page_mapcount(old_page) == 1);
2558         if (avoidcopy) {
2559                 if (PageAnon(old_page))
2560                         page_move_anon_rmap(old_page, vma, address);
2561                 set_huge_ptep_writable(vma, address, ptep);
2562                 return 0;
2563         }
2564 
2565         /*
2566          * If the process that created a MAP_PRIVATE mapping is about to
2567          * perform a COW due to a shared page count, attempt to satisfy
2568          * the allocation without using the existing reserves. The pagecache
2569          * page is used to determine if the reserve at this address was
2570          * consumed or not. If reserves were used, a partial faulted mapping
2571          * at the time of fork() could consume its reserves on COW instead
2572          * of the full address range.
2573          */
2574         if (!(vma->vm_flags & VM_MAYSHARE) &&
2575                         is_vma_resv_set(vma, HPAGE_RESV_OWNER) &&
2576                         old_page != pagecache_page)
2577                 outside_reserve = 1;
2578 
2579         page_cache_get(old_page);
2580 
2581         /* Drop page_table_lock as buddy allocator may be called */
2582         spin_unlock(&mm->page_table_lock);
2583         new_page = alloc_huge_page(vma, address, outside_reserve);
2584 
2585         if (IS_ERR(new_page)) {
2586                 page_cache_release(old_page);
2587 
2588                 /*
2589                  * If a process owning a MAP_PRIVATE mapping fails to COW,
2590                  * it is due to references held by a child and an insufficient
2591                  * huge page pool. To guarantee the original mappers
2592                  * reliability, unmap the page from child processes. The child
2593                  * may get SIGKILLed if it later faults.
2594                  */
2595                 if (outside_reserve) {
2596                         BUG_ON(huge_pte_none(pte));
2597                         if (unmap_ref_private(mm, vma, old_page, address)) {
2598                                 BUG_ON(huge_pte_none(pte));
2599                                 spin_lock(&mm->page_table_lock);
2600                                 goto retry_avoidcopy;
2601                         }
2602                         WARN_ON_ONCE(1);
2603                 }
2604 
2605                 /* Caller expects lock to be held */
2606                 spin_lock(&mm->page_table_lock);
2607                 return -PTR_ERR(new_page);
2608         }
2609 
2610         /*
2611          * When the original hugepage is shared one, it does not have
2612          * anon_vma prepared.
2613          */
2614         if (unlikely(anon_vma_prepare(vma))) {
2615                 page_cache_release(new_page);
2616                 page_cache_release(old_page);
2617                 /* Caller expects lock to be held */
2618                 spin_lock(&mm->page_table_lock);
2619                 return VM_FAULT_OOM;
2620         }
2621 
2622         copy_user_huge_page(new_page, old_page, address, vma,
2623                             pages_per_huge_page(h));
2624         __SetPageUptodate(new_page);
2625 
2626         /*
2627          * Retake the page_table_lock to check for racing updates
2628          * before the page tables are altered
2629          */
2630         spin_lock(&mm->page_table_lock);
2631         ptep = huge_pte_offset(mm, address & huge_page_mask(h));
2632         if (likely(pte_same(huge_ptep_get(ptep), pte))) {
2633                 /* Break COW */
2634                 mmu_notifier_invalidate_range_start(mm,
2635                         address & huge_page_mask(h),
2636                         (address & huge_page_mask(h)) + huge_page_size(h));
2637                 huge_ptep_clear_flush(vma, address, ptep);
2638                 set_huge_pte_at(mm, address, ptep,
2639                                 make_huge_pte(vma, new_page, 1));
2640                 page_remove_rmap(old_page);
2641                 hugepage_add_new_anon_rmap(new_page, vma, address);
2642                 /* Make the old page be freed below */
2643                 new_page = old_page;
2644                 mmu_notifier_invalidate_range_end(mm,
2645                         address & huge_page_mask(h),
2646                         (address & huge_page_mask(h)) + huge_page_size(h));
2647         }
2648         page_cache_release(new_page);
2649         page_cache_release(old_page);
2650         return 0;
2651 }
2652 
2653 /* Return the pagecache page at a given address within a VMA */
2654 static struct page *hugetlbfs_pagecache_page(struct hstate *h,
2655                         struct vm_area_struct *vma, unsigned long address)
2656 {
2657         struct address_space *mapping;
2658         pgoff_t idx;
2659 
2660         mapping = vma->vm_file->f_mapping;
2661         idx = vma_hugecache_offset(h, vma, address);
2662 
2663         return find_lock_page(mapping, idx);
2664 }
2665 
2666 /*
2667  * Return whether there is a pagecache page to back given address within VMA.
2668  * Caller follow_hugetlb_page() holds page_table_lock so we cannot lock_page.
2669  */
2670 static bool hugetlbfs_pagecache_present(struct hstate *h,
2671                         struct vm_area_struct *vma, unsigned long address)
2672 {
2673         struct address_space *mapping;
2674         pgoff_t idx;
2675         struct page *page;
2676 
2677         mapping = vma->vm_file->f_mapping;
2678         idx = vma_hugecache_offset(h, vma, address);
2679 
2680         page = find_get_page(mapping, idx);
2681         if (page)
2682                 put_page(page);
2683         return page != NULL;
2684 }
2685 
2686 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
2687                         unsigned long address, pte_t *ptep, unsigned int flags)
2688 {
2689         struct hstate *h = hstate_vma(vma);
2690         int ret = VM_FAULT_SIGBUS;
2691         pgoff_t idx;
2692         unsigned long size;
2693         struct page *page;
2694         struct address_space *mapping;
2695         pte_t new_pte;
2696 
2697         /*
2698          * Currently, we are forced to kill the process in the event the
2699          * original mapper has unmapped pages from the child due to a failed
2700          * COW. Warn that such a situation has occurred as it may not be obvious
2701          */
2702         if (is_vma_resv_set(vma, HPAGE_RESV_UNMAPPED)) {
2703                 printk(KERN_WARNING
2704                         "PID %d killed due to inadequate hugepage pool\n",
2705                         current->pid);
2706                 return ret;
2707         }
2708 
2709         mapping = vma->vm_file->f_mapping;
2710         idx = vma_hugecache_offset(h, vma, address);
2711 
2712         /*
2713          * Use page lock to guard against racing truncation
2714          * before we get page_table_lock.
2715          */
2716 retry:
2717         page = find_lock_page(mapping, idx);
2718         if (!page) {
2719                 size = i_size_read(mapping->host) >> huge_page_shift(h);
2720                 if (idx >= size)
2721                         goto out;
2722                 page = alloc_huge_page(vma, address, 0);
2723                 if (IS_ERR(page)) {
2724                         ret = -PTR_ERR(page);
2725                         goto out;
2726                 }
2727                 clear_huge_page(page, address, pages_per_huge_page(h));
2728                 __SetPageUptodate(page);
2729 
2730                 if (vma->vm_flags & VM_MAYSHARE) {
2731                         int err;
2732                         struct inode *inode = mapping->host;
2733 
2734                         err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
2735                         if (err) {
2736                                 put_page(page);
2737                                 if (err == -EEXIST)
2738                                         goto retry;
2739                                 goto out;
2740                         }
2741 
2742                         spin_lock(&inode->i_lock);
2743                         inode->i_blocks += blocks_per_huge_page(h);
2744                         spin_unlock(&inode->i_lock);
2745                         page_dup_rmap(page);
2746                 } else {
2747                         lock_page(page);
2748                         if (unlikely(anon_vma_prepare(vma))) {
2749                                 ret = VM_FAULT_OOM;
2750                                 goto backout_unlocked;
2751                         }
2752                         hugepage_add_new_anon_rmap(page, vma, address);
2753                 }
2754         } else {
2755                 /*
2756                  * If memory error occurs between mmap() and fault, some process
2757                  * don't have hwpoisoned swap entry for errored virtual address.
2758                  * So we need to block hugepage fault by PG_hwpoison bit check.
2759                  */
2760                 if (unlikely(PageHWPoison(page))) {
2761                         ret = VM_FAULT_HWPOISON |
2762                               VM_FAULT_SET_HINDEX(h - hstates);
2763                         goto backout_unlocked;
2764                 }
2765                 page_dup_rmap(page);
2766         }
2767 
2768         /*
2769          * If we are going to COW a private mapping later, we examine the
2770          * pending reservations for this page now. This will ensure that
2771          * any allocations necessary to record that reservation occur outside
2772          * the spinlock.
2773          */
2774         if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED))
2775                 if (vma_needs_reservation(h, vma, address) < 0) {
2776                         ret = VM_FAULT_OOM;
2777                         goto backout_unlocked;
2778                 }
2779 
2780         spin_lock(&mm->page_table_lock);
2781         size = i_size_read(mapping->host) >> huge_page_shift(h);
2782         if (idx >= size)
2783                 goto backout;
2784 
2785         ret = 0;
2786         if (!huge_pte_none(huge_ptep_get(ptep)))
2787                 goto backout;
2788 
2789         new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
2790                                 && (vma->vm_flags & VM_SHARED)));
2791         set_huge_pte_at(mm, address, ptep, new_pte);
2792 
2793         if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
2794                 /* Optimization, do the COW without a second fault */
2795                 ret = hugetlb_cow(mm, vma, address, ptep, new_pte, page);
2796         }
2797 
2798         spin_unlock(&mm->page_table_lock);
2799         unlock_page(page);
2800 out:
2801         return ret;
2802 
2803 backout:
2804         spin_unlock(&mm->page_table_lock);
2805 backout_unlocked:
2806         unlock_page(page);
2807         put_page(page);
2808         goto out;
2809 }
2810 
2811 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2812                         unsigned long address, unsigned int flags)
2813 {
2814         pte_t *ptep;
2815         pte_t entry;
2816         int ret;
2817         struct page *page = NULL;
2818         struct page *pagecache_page = NULL;
2819         static DEFINE_MUTEX(hugetlb_instantiation_mutex);
2820         struct hstate *h = hstate_vma(vma);
2821         int need_wait_lock = 0;
2822 
2823         ptep = huge_pte_offset(mm, address);
2824         if (ptep) {
2825                 entry = huge_ptep_get(ptep);
2826                 if (unlikely(is_hugetlb_entry_migration(entry))) {
2827                         migration_entry_wait_huge(mm, ptep);
2828                         return 0;
2829                 } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
2830                         return VM_FAULT_HWPOISON_LARGE |
2831                                VM_FAULT_SET_HINDEX(h - hstates);
2832         } else {
2833                 ptep = huge_pte_alloc(mm, address, huge_page_size(h));
2834                 if (!ptep)
2835                         return VM_FAULT_OOM;
2836         }
2837 
2838         /*
2839          * Serialize hugepage allocation and instantiation, so that we don't
2840          * get spurious allocation failures if two CPUs race to instantiate
2841          * the same page in the page cache.
2842          */
2843         mutex_lock(&hugetlb_instantiation_mutex);
2844         entry = huge_ptep_get(ptep);
2845         if (huge_pte_none(entry)) {
2846                 ret = hugetlb_no_page(mm, vma, address, ptep, flags);
2847                 goto out_mutex;
2848         }
2849 
2850         ret = 0;
2851 
2852         /*
2853          * entry could be a migration/hwpoison entry at this point, so this
2854          * check prevents the kernel from going below assuming that we have
2855          * a active hugepage in pagecache. This goto expects the 2nd page fault,
2856          * and is_hugetlb_entry_(migration|hwpoisoned) check will properly
2857          * handle it.
2858          */
2859         if (!pte_present(entry))
2860                 goto out_mutex;
2861 
2862         /*
2863          * If we are going to COW the mapping later, we examine the pending
2864          * reservations for this page now. This will ensure that any
2865          * allocations necessary to record that reservation occur outside the
2866          * spinlock. For private mappings, we also lookup the pagecache
2867          * page now as it is used to determine if a reservation has been
2868          * consumed.
2869          */
2870         if ((flags & FAULT_FLAG_WRITE) && !pte_write(entry)) {
2871                 if (vma_needs_reservation(h, vma, address) < 0) {
2872                         ret = VM_FAULT_OOM;
2873                         goto out_mutex;
2874                 }
2875 
2876                 if (!(vma->vm_flags & VM_MAYSHARE))
2877                         pagecache_page = hugetlbfs_pagecache_page(h,
2878                                                                 vma, address);
2879         }
2880 
2881         spin_lock(&mm->page_table_lock);
2882         /* Check for a racing update before calling hugetlb_cow */
2883         if (unlikely(!pte_same(entry, huge_ptep_get(ptep))))
2884                 goto out_page_table_lock;
2885 
2886         /*
2887          * hugetlb_cow() requires page locks of pte_page(entry) and
2888          * pagecache_page, so here we need take the former one
2889          * when page != pagecache_page or !pagecache_page.
2890          */
2891         page = pte_page(entry);
2892         if (page != pagecache_page)
2893                 if (!trylock_page(page)) {
2894                         need_wait_lock = 1;
2895                         goto out_page_table_lock;
2896                 }
2897 
2898         get_page(page);
2899 
2900         if (flags & FAULT_FLAG_WRITE) {
2901                 if (!pte_write(entry)) {
2902                         ret = hugetlb_cow(mm, vma, address, ptep, entry,
2903                                                         pagecache_page);
2904                         goto out_put_page;
2905                 }
2906                 entry = pte_mkdirty(entry);
2907         }
2908         entry = pte_mkyoung(entry);
2909         if (huge_ptep_set_access_flags(vma, address, ptep, entry,
2910                                                 flags & FAULT_FLAG_WRITE))
2911                 update_mmu_cache(vma, address, ptep);
2912 out_put_page:
2913         if (page != pagecache_page)
2914                 unlock_page(page);
2915         put_page(page);
2916 out_page_table_lock:
2917         spin_unlock(&mm->page_table_lock);
2918 
2919         if (pagecache_page) {
2920                 unlock_page(pagecache_page);
2921                 put_page(pagecache_page);
2922         }
2923 out_mutex:
2924         mutex_unlock(&hugetlb_instantiation_mutex);
2925 
2926         /*
2927          * Generally it's safe to hold refcount during waiting page lock. But
2928          * here we just wait to defer the next page fault to avoid busy loop and
2929          * the page is not used after unlocked before returning from the current
2930          * page fault. So we are safe from accessing freed page, even if we wait
2931          * here without taking refcount.
2932          */
2933         if (need_wait_lock)
2934                 wait_on_page_locked(page);
2935         return ret;
2936 }
2937 
2938 /* Can be overriden by architectures */
2939 __attribute__((weak)) struct page *
2940 follow_huge_pud(struct mm_struct *mm, unsigned long address,
2941                pud_t *pud, int write)
2942 {
2943         BUG();
2944         return NULL;
2945 }
2946 
2947 int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
2948                         struct page **pages, struct vm_area_struct **vmas,
2949                         unsigned long *position, int *length, int i,
2950                         unsigned int flags)
2951 {
2952         unsigned long pfn_offset;
2953         unsigned long vaddr = *position;
2954         int remainder = *length;
2955         struct hstate *h = hstate_vma(vma);
2956 
2957         spin_lock(&mm->page_table_lock);
2958         while (vaddr < vma->vm_end && remainder) {
2959                 pte_t *pte;
2960                 int absent;
2961                 struct page *page;
2962 
2963                 /*
2964                  * Some archs (sparc64, sh*) have multiple pte_ts to
2965                  * each hugepage.  We have to make sure we get the
2966                  * first, for the page indexing below to work.
2967                  */
2968                 pte = huge_pte_offset(mm, vaddr & huge_page_mask(h));
2969                 absent = !pte || huge_pte_none(huge_ptep_get(pte));
2970 
2971                 /*
2972                  * When coredumping, it suits get_dump_page if we just return
2973                  * an error where there's an empty slot with no huge pagecache
2974                  * to back it.  This way, we avoid allocating a hugepage, and
2975                  * the sparse dumpfile avoids allocating disk blocks, but its
2976                  * huge holes still show up with zeroes where they need to be.
2977                  */
2978                 if (absent && (flags & FOLL_DUMP) &&
2979                     !hugetlbfs_pagecache_present(h, vma, vaddr)) {
2980                         remainder = 0;
2981                         break;
2982                 }
2983 
2984                 /*
2985                  * We need call hugetlb_fault for both hugepages under migration
2986                  * (in which case hugetlb_fault waits for the migration,) and
2987                  * hwpoisoned hugepages (in which case we need to prevent the
2988                  * caller from accessing to them.) In order to do this, we use
2989                  * here is_swap_pte instead of is_hugetlb_entry_migration and
2990                  * is_hugetlb_entry_hwpoisoned. This is because it simply covers
2991                  * both cases, and because we can't follow correct pages
2992                  * directly from any kind of swap entries.
2993                  */
2994                 if (absent || is_swap_pte(huge_ptep_get(pte)) ||
2995                     ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
2996                         int ret;
2997 
2998                         spin_unlock(&mm->page_table_lock);
2999                         ret = hugetlb_fault(mm, vma, vaddr,
3000                                 (flags & FOLL_WRITE) ? FAULT_FLAG_WRITE : 0);
3001                         spin_lock(&mm->page_table_lock);
3002                         if (!(ret & VM_FAULT_ERROR))
3003                                 continue;
3004 
3005                         remainder = 0;
3006                         break;
3007                 }
3008 
3009                 pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT;
3010                 page = pte_page(huge_ptep_get(pte));
3011 same_page:
3012                 if (pages) {
3013                         pages[i] = mem_map_offset(page, pfn_offset);
3014                         get_page(pages[i]);
3015                 }
3016 
3017                 if (vmas)
3018                         vmas[i] = vma;
3019 
3020                 vaddr += PAGE_SIZE;
3021                 ++pfn_offset;
3022                 --remainder;
3023                 ++i;
3024                 if (vaddr < vma->vm_end && remainder &&
3025                                 pfn_offset < pages_per_huge_page(h)) {
3026                         /*
3027                          * We use pfn_offset to avoid touching the pageframes
3028                          * of this compound page.
3029                          */
3030                         goto same_page;
3031                 }
3032         }
3033         spin_unlock(&mm->page_table_lock);
3034         *length = remainder;
3035         *position = vaddr;
3036 
3037         return i ? i : -EFAULT;
3038 }
3039 
3040 void hugetlb_change_protection(struct vm_area_struct *vma,
3041                 unsigned long address, unsigned long end, pgprot_t newprot)
3042 {
3043         struct mm_struct *mm = vma->vm_mm;
3044         unsigned long start = address;
3045         pte_t *ptep;
3046         pte_t pte;
3047         struct hstate *h = hstate_vma(vma);
3048 
3049         BUG_ON(address >= end);
3050         flush_cache_range(vma, address, end);
3051 
3052         mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
3053         spin_lock(&mm->page_table_lock);
3054         for (; address < end; address += huge_page_size(h)) {
3055                 ptep = huge_pte_offset(mm, address);
3056                 if (!ptep)
3057                         continue;
3058                 if (huge_pmd_unshare(mm, &address, ptep))
3059                         continue;
3060                 pte = huge_ptep_get(ptep);
3061                 if (unlikely(is_hugetlb_entry_hwpoisoned(pte)))
3062                         continue;
3063                 if (unlikely(is_hugetlb_entry_migration(pte))) {
3064                         swp_entry_t entry = pte_to_swp_entry(pte);
3065 
3066                         if (is_write_migration_entry(entry)) {
3067                                 pte_t newpte;
3068 
3069                                 make_migration_entry_read(&entry);
3070                                 newpte = swp_entry_to_pte(entry);
3071                                 set_huge_pte_at(mm, address, ptep, newpte);
3072                         }
3073                         continue;
3074                 }
3075                 if (!huge_pte_none(pte)) {
3076                         pte = huge_ptep_get_and_clear(mm, address, ptep);
3077                         pte = pte_mkhuge(pte_modify(pte, newprot));
3078                         set_huge_pte_at(mm, address, ptep, pte);
3079                 }
3080         }
3081         spin_unlock(&mm->page_table_lock);
3082         /*
3083          * Must flush TLB before releasing i_mmap_mutex: x86's huge_pmd_unshare
3084          * may have cleared our pud entry and done put_page on the page table:
3085          * once we release i_mmap_mutex, another task can do the final put_page
3086          * and that page table be reused and filled with junk.
3087          */
3088         flush_tlb_range(vma, start, end);
3089         mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
3090 }
3091 
3092 int hugetlb_reserve_pages(struct inode *inode,
3093                                         long from, long to,
3094                                         struct vm_area_struct *vma,
3095                                         vm_flags_t vm_flags)
3096 {
3097         long ret, chg;
3098         struct hstate *h = hstate_inode(inode);
3099         struct hugepage_subpool *spool = subpool_inode(inode);
3100 
3101         /* This should never happen */
3102         if (from > to) {
3103 #ifdef CONFIG_DEBUG_VM
3104                 WARN(1, "%s called with a negative range\n", __func__);
3105 #endif
3106                 return -EINVAL;
3107         }
3108 
3109         /*
3110          * Only apply hugepage reservation if asked. At fault time, an
3111          * attempt will be made for VM_NORESERVE to allocate a page
3112          * without using reserves
3113          */
3114         if (vm_flags & VM_NORESERVE)
3115                 return 0;
3116 
3117         /*
3118          * Shared mappings base their reservation on the number of pages that
3119          * are already allocated on behalf of the file. Private mappings need
3120          * to reserve the full area even if read-only as mprotect() may be
3121          * called to make the mapping read-write. Assume !vma is a shm mapping
3122          */
3123         if (!vma || vma->vm_flags & VM_MAYSHARE)
3124                 chg = region_chg(&inode->i_mapping->private_list, from, to);
3125         else {
3126                 struct resv_map *resv_map = resv_map_alloc();
3127                 if (!resv_map)
3128                         return -ENOMEM;
3129 
3130                 chg = to - from;
3131 
3132                 set_vma_resv_map(vma, resv_map);
3133                 set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
3134         }
3135 
3136         if (chg < 0) {
3137                 ret = chg;
3138                 goto out_err;
3139         }
3140 
3141         /* There must be enough pages in the subpool for the mapping */
3142         if (hugepage_subpool_get_pages(spool, chg)) {
3143                 ret = -ENOSPC;
3144                 goto out_err;
3145         }
3146 
3147         /*
3148          * Check enough hugepages are available for the reservation.
3149          * Hand the pages back to the subpool if there are not
3150          */
3151         ret = hugetlb_acct_memory(h, chg);
3152         if (ret < 0) {
3153                 hugepage_subpool_put_pages(spool, chg);
3154                 goto out_err;
3155         }
3156 
3157         /*
3158          * Account for the reservations made. Shared mappings record regions
3159          * that have reservations as they are shared by multiple VMAs.
3160          * When the last VMA disappears, the region map says how much
3161          * the reservation was and the page cache tells how much of
3162          * the reservation was consumed. Private mappings are per-VMA and
3163          * only the consumed reservations are tracked. When the VMA
3164          * disappears, the original reservation is the VMA size and the
3165          * consumed reservations are stored in the map. Hence, nothing
3166          * else has to be done for private mappings here
3167          */
3168         if (!vma || vma->vm_flags & VM_MAYSHARE)
3169                 region_add(&inode->i_mapping->private_list, from, to);
3170         return 0;
3171 out_err:
3172         if (vma)
3173                 resv_map_put(vma);
3174         return ret;
3175 }
3176 
3177 void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
3178 {
3179         struct hstate *h = hstate_inode(inode);
3180         long chg = region_truncate(&inode->i_mapping->private_list, offset);
3181         struct hugepage_subpool *spool = subpool_inode(inode);
3182 
3183         spin_lock(&inode->i_lock);
3184         inode->i_blocks -= (blocks_per_huge_page(h) * freed);
3185         spin_unlock(&inode->i_lock);
3186 
3187         hugepage_subpool_put_pages(spool, (chg - freed));
3188         hugetlb_acct_memory(h, -(chg - freed));
3189 }
3190 
3191 #ifdef CONFIG_MEMORY_FAILURE
3192 
3193 /* Should be called in hugetlb_lock */
3194 static int is_hugepage_on_freelist(struct page *hpage)
3195 {
3196         struct page *page;
3197         struct page *tmp;
3198         struct hstate *h = page_hstate(hpage);
3199         int nid = page_to_nid(hpage);
3200 
3201         list_for_each_entry_safe(page, tmp, &h->hugepage_freelists[nid], lru)
3202                 if (page == hpage)
3203                         return 1;
3204         return 0;
3205 }
3206 
3207 /*
3208  * This function is called from memory failure code.
3209  * Assume the caller holds page lock of the head page.
3210  */
3211 int dequeue_hwpoisoned_huge_page(struct page *hpage)
3212 {
3213         struct hstate *h = page_hstate(hpage);
3214         int nid = page_to_nid(hpage);
3215         int ret = -EBUSY;
3216 
3217         spin_lock(&hugetlb_lock);
3218         if (is_hugepage_on_freelist(hpage)) {
3219                 list_del(&hpage->lru);
3220                 set_page_refcounted(hpage);
3221                 h->free_huge_pages--;
3222                 h->free_huge_pages_node[nid]--;
3223                 ret = 0;
3224         }
3225         spin_unlock(&hugetlb_lock);
3226         return ret;
3227 }
3228 #endif
3229 

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