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TOMOYO Linux Cross Reference
Linux/mm/huge_memory.c

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  1 /*
  2  *  Copyright (C) 2009  Red Hat, Inc.
  3  *
  4  *  This work is licensed under the terms of the GNU GPL, version 2. See
  5  *  the COPYING file in the top-level directory.
  6  */
  7 
  8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  9 
 10 #include <linux/mm.h>
 11 #include <linux/sched.h>
 12 #include <linux/sched/coredump.h>
 13 #include <linux/sched/numa_balancing.h>
 14 #include <linux/highmem.h>
 15 #include <linux/hugetlb.h>
 16 #include <linux/mmu_notifier.h>
 17 #include <linux/rmap.h>
 18 #include <linux/swap.h>
 19 #include <linux/shrinker.h>
 20 #include <linux/mm_inline.h>
 21 #include <linux/swapops.h>
 22 #include <linux/dax.h>
 23 #include <linux/khugepaged.h>
 24 #include <linux/freezer.h>
 25 #include <linux/pfn_t.h>
 26 #include <linux/mman.h>
 27 #include <linux/memremap.h>
 28 #include <linux/pagemap.h>
 29 #include <linux/debugfs.h>
 30 #include <linux/migrate.h>
 31 #include <linux/hashtable.h>
 32 #include <linux/userfaultfd_k.h>
 33 #include <linux/page_idle.h>
 34 #include <linux/shmem_fs.h>
 35 #include <linux/oom.h>
 36 #include <linux/numa.h>
 37 
 38 #include <asm/tlb.h>
 39 #include <asm/pgalloc.h>
 40 #include "internal.h"
 41 
 42 /*
 43  * By default, transparent hugepage support is disabled in order to avoid
 44  * risking an increased memory footprint for applications that are not
 45  * guaranteed to benefit from it. When transparent hugepage support is
 46  * enabled, it is for all mappings, and khugepaged scans all mappings.
 47  * Defrag is invoked by khugepaged hugepage allocations and by page faults
 48  * for all hugepage allocations.
 49  */
 50 unsigned long transparent_hugepage_flags __read_mostly =
 51 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
 52         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
 53 #endif
 54 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
 55         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
 56 #endif
 57         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
 58         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
 59         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 60 
 61 static struct shrinker deferred_split_shrinker;
 62 
 63 static atomic_t huge_zero_refcount;
 64 struct page *huge_zero_page __read_mostly;
 65 
 66 bool transparent_hugepage_enabled(struct vm_area_struct *vma)
 67 {
 68         if (vma_is_anonymous(vma))
 69                 return __transparent_hugepage_enabled(vma);
 70         if (vma_is_shmem(vma) && shmem_huge_enabled(vma))
 71                 return __transparent_hugepage_enabled(vma);
 72 
 73         return false;
 74 }
 75 
 76 static struct page *get_huge_zero_page(void)
 77 {
 78         struct page *zero_page;
 79 retry:
 80         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 81                 return READ_ONCE(huge_zero_page);
 82 
 83         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 84                         HPAGE_PMD_ORDER);
 85         if (!zero_page) {
 86                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 87                 return NULL;
 88         }
 89         count_vm_event(THP_ZERO_PAGE_ALLOC);
 90         preempt_disable();
 91         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 92                 preempt_enable();
 93                 __free_pages(zero_page, compound_order(zero_page));
 94                 goto retry;
 95         }
 96 
 97         /* We take additional reference here. It will be put back by shrinker */
 98         atomic_set(&huge_zero_refcount, 2);
 99         preempt_enable();
100         return READ_ONCE(huge_zero_page);
101 }
102 
103 static void put_huge_zero_page(void)
104 {
105         /*
106          * Counter should never go to zero here. Only shrinker can put
107          * last reference.
108          */
109         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
110 }
111 
112 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
113 {
114         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
115                 return READ_ONCE(huge_zero_page);
116 
117         if (!get_huge_zero_page())
118                 return NULL;
119 
120         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
121                 put_huge_zero_page();
122 
123         return READ_ONCE(huge_zero_page);
124 }
125 
126 void mm_put_huge_zero_page(struct mm_struct *mm)
127 {
128         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
129                 put_huge_zero_page();
130 }
131 
132 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
133                                         struct shrink_control *sc)
134 {
135         /* we can free zero page only if last reference remains */
136         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
137 }
138 
139 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
140                                        struct shrink_control *sc)
141 {
142         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
143                 struct page *zero_page = xchg(&huge_zero_page, NULL);
144                 BUG_ON(zero_page == NULL);
145                 __free_pages(zero_page, compound_order(zero_page));
146                 return HPAGE_PMD_NR;
147         }
148 
149         return 0;
150 }
151 
152 static struct shrinker huge_zero_page_shrinker = {
153         .count_objects = shrink_huge_zero_page_count,
154         .scan_objects = shrink_huge_zero_page_scan,
155         .seeks = DEFAULT_SEEKS,
156 };
157 
158 #ifdef CONFIG_SYSFS
159 static ssize_t enabled_show(struct kobject *kobj,
160                             struct kobj_attribute *attr, char *buf)
161 {
162         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
163                 return sprintf(buf, "[always] madvise never\n");
164         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
165                 return sprintf(buf, "always [madvise] never\n");
166         else
167                 return sprintf(buf, "always madvise [never]\n");
168 }
169 
170 static ssize_t enabled_store(struct kobject *kobj,
171                              struct kobj_attribute *attr,
172                              const char *buf, size_t count)
173 {
174         ssize_t ret = count;
175 
176         if (!memcmp("always", buf,
177                     min(sizeof("always")-1, count))) {
178                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
179                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
180         } else if (!memcmp("madvise", buf,
181                            min(sizeof("madvise")-1, count))) {
182                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
183                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
184         } else if (!memcmp("never", buf,
185                            min(sizeof("never")-1, count))) {
186                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
187                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
188         } else
189                 ret = -EINVAL;
190 
191         if (ret > 0) {
192                 int err = start_stop_khugepaged();
193                 if (err)
194                         ret = err;
195         }
196         return ret;
197 }
198 static struct kobj_attribute enabled_attr =
199         __ATTR(enabled, 0644, enabled_show, enabled_store);
200 
201 ssize_t single_hugepage_flag_show(struct kobject *kobj,
202                                 struct kobj_attribute *attr, char *buf,
203                                 enum transparent_hugepage_flag flag)
204 {
205         return sprintf(buf, "%d\n",
206                        !!test_bit(flag, &transparent_hugepage_flags));
207 }
208 
209 ssize_t single_hugepage_flag_store(struct kobject *kobj,
210                                  struct kobj_attribute *attr,
211                                  const char *buf, size_t count,
212                                  enum transparent_hugepage_flag flag)
213 {
214         unsigned long value;
215         int ret;
216 
217         ret = kstrtoul(buf, 10, &value);
218         if (ret < 0)
219                 return ret;
220         if (value > 1)
221                 return -EINVAL;
222 
223         if (value)
224                 set_bit(flag, &transparent_hugepage_flags);
225         else
226                 clear_bit(flag, &transparent_hugepage_flags);
227 
228         return count;
229 }
230 
231 static ssize_t defrag_show(struct kobject *kobj,
232                            struct kobj_attribute *attr, char *buf)
233 {
234         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
235                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
236         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
237                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
238         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
239                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
240         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
241                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
242         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
243 }
244 
245 static ssize_t defrag_store(struct kobject *kobj,
246                             struct kobj_attribute *attr,
247                             const char *buf, size_t count)
248 {
249         if (!memcmp("always", buf,
250                     min(sizeof("always")-1, count))) {
251                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
253                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
254                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
255         } else if (!memcmp("defer+madvise", buf,
256                     min(sizeof("defer+madvise")-1, count))) {
257                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
259                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
260                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
261         } else if (!memcmp("defer", buf,
262                     min(sizeof("defer")-1, count))) {
263                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
264                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
265                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
266                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
267         } else if (!memcmp("madvise", buf,
268                            min(sizeof("madvise")-1, count))) {
269                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
270                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
271                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
272                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
273         } else if (!memcmp("never", buf,
274                            min(sizeof("never")-1, count))) {
275                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
276                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
277                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
278                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
279         } else
280                 return -EINVAL;
281 
282         return count;
283 }
284 static struct kobj_attribute defrag_attr =
285         __ATTR(defrag, 0644, defrag_show, defrag_store);
286 
287 static ssize_t use_zero_page_show(struct kobject *kobj,
288                 struct kobj_attribute *attr, char *buf)
289 {
290         return single_hugepage_flag_show(kobj, attr, buf,
291                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
292 }
293 static ssize_t use_zero_page_store(struct kobject *kobj,
294                 struct kobj_attribute *attr, const char *buf, size_t count)
295 {
296         return single_hugepage_flag_store(kobj, attr, buf, count,
297                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
298 }
299 static struct kobj_attribute use_zero_page_attr =
300         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
301 
302 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
303                 struct kobj_attribute *attr, char *buf)
304 {
305         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
306 }
307 static struct kobj_attribute hpage_pmd_size_attr =
308         __ATTR_RO(hpage_pmd_size);
309 
310 #ifdef CONFIG_DEBUG_VM
311 static ssize_t debug_cow_show(struct kobject *kobj,
312                                 struct kobj_attribute *attr, char *buf)
313 {
314         return single_hugepage_flag_show(kobj, attr, buf,
315                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
316 }
317 static ssize_t debug_cow_store(struct kobject *kobj,
318                                struct kobj_attribute *attr,
319                                const char *buf, size_t count)
320 {
321         return single_hugepage_flag_store(kobj, attr, buf, count,
322                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
323 }
324 static struct kobj_attribute debug_cow_attr =
325         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
326 #endif /* CONFIG_DEBUG_VM */
327 
328 static struct attribute *hugepage_attr[] = {
329         &enabled_attr.attr,
330         &defrag_attr.attr,
331         &use_zero_page_attr.attr,
332         &hpage_pmd_size_attr.attr,
333 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
334         &shmem_enabled_attr.attr,
335 #endif
336 #ifdef CONFIG_DEBUG_VM
337         &debug_cow_attr.attr,
338 #endif
339         NULL,
340 };
341 
342 static const struct attribute_group hugepage_attr_group = {
343         .attrs = hugepage_attr,
344 };
345 
346 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
347 {
348         int err;
349 
350         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
351         if (unlikely(!*hugepage_kobj)) {
352                 pr_err("failed to create transparent hugepage kobject\n");
353                 return -ENOMEM;
354         }
355 
356         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
357         if (err) {
358                 pr_err("failed to register transparent hugepage group\n");
359                 goto delete_obj;
360         }
361 
362         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
363         if (err) {
364                 pr_err("failed to register transparent hugepage group\n");
365                 goto remove_hp_group;
366         }
367 
368         return 0;
369 
370 remove_hp_group:
371         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
372 delete_obj:
373         kobject_put(*hugepage_kobj);
374         return err;
375 }
376 
377 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
378 {
379         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
380         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
381         kobject_put(hugepage_kobj);
382 }
383 #else
384 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
385 {
386         return 0;
387 }
388 
389 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
390 {
391 }
392 #endif /* CONFIG_SYSFS */
393 
394 static int __init hugepage_init(void)
395 {
396         int err;
397         struct kobject *hugepage_kobj;
398 
399         if (!has_transparent_hugepage()) {
400                 transparent_hugepage_flags = 0;
401                 return -EINVAL;
402         }
403 
404         /*
405          * hugepages can't be allocated by the buddy allocator
406          */
407         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
408         /*
409          * we use page->mapping and page->index in second tail page
410          * as list_head: assuming THP order >= 2
411          */
412         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
413 
414         err = hugepage_init_sysfs(&hugepage_kobj);
415         if (err)
416                 goto err_sysfs;
417 
418         err = khugepaged_init();
419         if (err)
420                 goto err_slab;
421 
422         err = register_shrinker(&huge_zero_page_shrinker);
423         if (err)
424                 goto err_hzp_shrinker;
425         err = register_shrinker(&deferred_split_shrinker);
426         if (err)
427                 goto err_split_shrinker;
428 
429         /*
430          * By default disable transparent hugepages on smaller systems,
431          * where the extra memory used could hurt more than TLB overhead
432          * is likely to save.  The admin can still enable it through /sys.
433          */
434         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
435                 transparent_hugepage_flags = 0;
436                 return 0;
437         }
438 
439         err = start_stop_khugepaged();
440         if (err)
441                 goto err_khugepaged;
442 
443         return 0;
444 err_khugepaged:
445         unregister_shrinker(&deferred_split_shrinker);
446 err_split_shrinker:
447         unregister_shrinker(&huge_zero_page_shrinker);
448 err_hzp_shrinker:
449         khugepaged_destroy();
450 err_slab:
451         hugepage_exit_sysfs(hugepage_kobj);
452 err_sysfs:
453         return err;
454 }
455 subsys_initcall(hugepage_init);
456 
457 static int __init setup_transparent_hugepage(char *str)
458 {
459         int ret = 0;
460         if (!str)
461                 goto out;
462         if (!strcmp(str, "always")) {
463                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
464                         &transparent_hugepage_flags);
465                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
466                           &transparent_hugepage_flags);
467                 ret = 1;
468         } else if (!strcmp(str, "madvise")) {
469                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
470                           &transparent_hugepage_flags);
471                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
472                         &transparent_hugepage_flags);
473                 ret = 1;
474         } else if (!strcmp(str, "never")) {
475                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
476                           &transparent_hugepage_flags);
477                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
478                           &transparent_hugepage_flags);
479                 ret = 1;
480         }
481 out:
482         if (!ret)
483                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
484         return ret;
485 }
486 __setup("transparent_hugepage=", setup_transparent_hugepage);
487 
488 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
489 {
490         if (likely(vma->vm_flags & VM_WRITE))
491                 pmd = pmd_mkwrite(pmd);
492         return pmd;
493 }
494 
495 static inline struct list_head *page_deferred_list(struct page *page)
496 {
497         /* ->lru in the tail pages is occupied by compound_head. */
498         return &page[2].deferred_list;
499 }
500 
501 void prep_transhuge_page(struct page *page)
502 {
503         /*
504          * we use page->mapping and page->indexlru in second tail page
505          * as list_head: assuming THP order >= 2
506          */
507 
508         INIT_LIST_HEAD(page_deferred_list(page));
509         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
510 }
511 
512 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
513                 loff_t off, unsigned long flags, unsigned long size)
514 {
515         unsigned long addr;
516         loff_t off_end = off + len;
517         loff_t off_align = round_up(off, size);
518         unsigned long len_pad;
519 
520         if (off_end <= off_align || (off_end - off_align) < size)
521                 return 0;
522 
523         len_pad = len + size;
524         if (len_pad < len || (off + len_pad) < off)
525                 return 0;
526 
527         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
528                                               off >> PAGE_SHIFT, flags);
529         if (IS_ERR_VALUE(addr))
530                 return 0;
531 
532         addr += (off - addr) & (size - 1);
533         return addr;
534 }
535 
536 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
537                 unsigned long len, unsigned long pgoff, unsigned long flags)
538 {
539         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
540 
541         if (addr)
542                 goto out;
543         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
544                 goto out;
545 
546         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
547         if (addr)
548                 return addr;
549 
550  out:
551         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
552 }
553 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
554 
555 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
556                         struct page *page, gfp_t gfp)
557 {
558         struct vm_area_struct *vma = vmf->vma;
559         struct mem_cgroup *memcg;
560         pgtable_t pgtable;
561         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
562         vm_fault_t ret = 0;
563 
564         VM_BUG_ON_PAGE(!PageCompound(page), page);
565 
566         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
567                 put_page(page);
568                 count_vm_event(THP_FAULT_FALLBACK);
569                 return VM_FAULT_FALLBACK;
570         }
571 
572         pgtable = pte_alloc_one(vma->vm_mm);
573         if (unlikely(!pgtable)) {
574                 ret = VM_FAULT_OOM;
575                 goto release;
576         }
577 
578         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
579         /*
580          * The memory barrier inside __SetPageUptodate makes sure that
581          * clear_huge_page writes become visible before the set_pmd_at()
582          * write.
583          */
584         __SetPageUptodate(page);
585 
586         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
587         if (unlikely(!pmd_none(*vmf->pmd))) {
588                 goto unlock_release;
589         } else {
590                 pmd_t entry;
591 
592                 ret = check_stable_address_space(vma->vm_mm);
593                 if (ret)
594                         goto unlock_release;
595 
596                 /* Deliver the page fault to userland */
597                 if (userfaultfd_missing(vma)) {
598                         vm_fault_t ret2;
599 
600                         spin_unlock(vmf->ptl);
601                         mem_cgroup_cancel_charge(page, memcg, true);
602                         put_page(page);
603                         pte_free(vma->vm_mm, pgtable);
604                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
605                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
606                         return ret2;
607                 }
608 
609                 entry = mk_huge_pmd(page, vma->vm_page_prot);
610                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
611                 page_add_new_anon_rmap(page, vma, haddr, true);
612                 mem_cgroup_commit_charge(page, memcg, false, true);
613                 lru_cache_add_active_or_unevictable(page, vma);
614                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
615                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
616                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
617                 mm_inc_nr_ptes(vma->vm_mm);
618                 spin_unlock(vmf->ptl);
619                 count_vm_event(THP_FAULT_ALLOC);
620                 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
621         }
622 
623         return 0;
624 unlock_release:
625         spin_unlock(vmf->ptl);
626 release:
627         if (pgtable)
628                 pte_free(vma->vm_mm, pgtable);
629         mem_cgroup_cancel_charge(page, memcg, true);
630         put_page(page);
631         return ret;
632 
633 }
634 
635 /*
636  * always: directly stall for all thp allocations
637  * defer: wake kswapd and fail if not immediately available
638  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
639  *                fail if not immediately available
640  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
641  *          available
642  * never: never stall for any thp allocation
643  */
644 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
645 {
646         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
647 
648         /* Always do synchronous compaction */
649         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
650                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
651 
652         /* Kick kcompactd and fail quickly */
653         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
654                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
655 
656         /* Synchronous compaction if madvised, otherwise kick kcompactd */
657         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
658                 return GFP_TRANSHUGE_LIGHT |
659                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
660                                         __GFP_KSWAPD_RECLAIM);
661 
662         /* Only do synchronous compaction if madvised */
663         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
664                 return GFP_TRANSHUGE_LIGHT |
665                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
666 
667         return GFP_TRANSHUGE_LIGHT;
668 }
669 
670 /* Caller must hold page table lock. */
671 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
672                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
673                 struct page *zero_page)
674 {
675         pmd_t entry;
676         if (!pmd_none(*pmd))
677                 return false;
678         entry = mk_pmd(zero_page, vma->vm_page_prot);
679         entry = pmd_mkhuge(entry);
680         if (pgtable)
681                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
682         set_pmd_at(mm, haddr, pmd, entry);
683         mm_inc_nr_ptes(mm);
684         return true;
685 }
686 
687 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
688 {
689         struct vm_area_struct *vma = vmf->vma;
690         gfp_t gfp;
691         struct page *page;
692         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
693 
694         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
695                 return VM_FAULT_FALLBACK;
696         if (unlikely(anon_vma_prepare(vma)))
697                 return VM_FAULT_OOM;
698         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
699                 return VM_FAULT_OOM;
700         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
701                         !mm_forbids_zeropage(vma->vm_mm) &&
702                         transparent_hugepage_use_zero_page()) {
703                 pgtable_t pgtable;
704                 struct page *zero_page;
705                 bool set;
706                 vm_fault_t ret;
707                 pgtable = pte_alloc_one(vma->vm_mm);
708                 if (unlikely(!pgtable))
709                         return VM_FAULT_OOM;
710                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
711                 if (unlikely(!zero_page)) {
712                         pte_free(vma->vm_mm, pgtable);
713                         count_vm_event(THP_FAULT_FALLBACK);
714                         return VM_FAULT_FALLBACK;
715                 }
716                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
717                 ret = 0;
718                 set = false;
719                 if (pmd_none(*vmf->pmd)) {
720                         ret = check_stable_address_space(vma->vm_mm);
721                         if (ret) {
722                                 spin_unlock(vmf->ptl);
723                         } else if (userfaultfd_missing(vma)) {
724                                 spin_unlock(vmf->ptl);
725                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
726                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
727                         } else {
728                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
729                                                    haddr, vmf->pmd, zero_page);
730                                 spin_unlock(vmf->ptl);
731                                 set = true;
732                         }
733                 } else
734                         spin_unlock(vmf->ptl);
735                 if (!set)
736                         pte_free(vma->vm_mm, pgtable);
737                 return ret;
738         }
739         gfp = alloc_hugepage_direct_gfpmask(vma);
740         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
741         if (unlikely(!page)) {
742                 count_vm_event(THP_FAULT_FALLBACK);
743                 return VM_FAULT_FALLBACK;
744         }
745         prep_transhuge_page(page);
746         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
747 }
748 
749 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
750                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
751                 pgtable_t pgtable)
752 {
753         struct mm_struct *mm = vma->vm_mm;
754         pmd_t entry;
755         spinlock_t *ptl;
756 
757         ptl = pmd_lock(mm, pmd);
758         if (!pmd_none(*pmd)) {
759                 if (write) {
760                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
761                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
762                                 goto out_unlock;
763                         }
764                         entry = pmd_mkyoung(*pmd);
765                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
766                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
767                                 update_mmu_cache_pmd(vma, addr, pmd);
768                 }
769 
770                 goto out_unlock;
771         }
772 
773         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
774         if (pfn_t_devmap(pfn))
775                 entry = pmd_mkdevmap(entry);
776         if (write) {
777                 entry = pmd_mkyoung(pmd_mkdirty(entry));
778                 entry = maybe_pmd_mkwrite(entry, vma);
779         }
780 
781         if (pgtable) {
782                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
783                 mm_inc_nr_ptes(mm);
784                 pgtable = NULL;
785         }
786 
787         set_pmd_at(mm, addr, pmd, entry);
788         update_mmu_cache_pmd(vma, addr, pmd);
789 
790 out_unlock:
791         spin_unlock(ptl);
792         if (pgtable)
793                 pte_free(mm, pgtable);
794 }
795 
796 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
797 {
798         unsigned long addr = vmf->address & PMD_MASK;
799         struct vm_area_struct *vma = vmf->vma;
800         pgprot_t pgprot = vma->vm_page_prot;
801         pgtable_t pgtable = NULL;
802 
803         /*
804          * If we had pmd_special, we could avoid all these restrictions,
805          * but we need to be consistent with PTEs and architectures that
806          * can't support a 'special' bit.
807          */
808         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
809                         !pfn_t_devmap(pfn));
810         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
811                                                 (VM_PFNMAP|VM_MIXEDMAP));
812         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
813 
814         if (addr < vma->vm_start || addr >= vma->vm_end)
815                 return VM_FAULT_SIGBUS;
816 
817         if (arch_needs_pgtable_deposit()) {
818                 pgtable = pte_alloc_one(vma->vm_mm);
819                 if (!pgtable)
820                         return VM_FAULT_OOM;
821         }
822 
823         track_pfn_insert(vma, &pgprot, pfn);
824 
825         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
826         return VM_FAULT_NOPAGE;
827 }
828 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
829 
830 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
831 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
832 {
833         if (likely(vma->vm_flags & VM_WRITE))
834                 pud = pud_mkwrite(pud);
835         return pud;
836 }
837 
838 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
839                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
840 {
841         struct mm_struct *mm = vma->vm_mm;
842         pud_t entry;
843         spinlock_t *ptl;
844 
845         ptl = pud_lock(mm, pud);
846         if (!pud_none(*pud)) {
847                 if (write) {
848                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
849                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
850                                 goto out_unlock;
851                         }
852                         entry = pud_mkyoung(*pud);
853                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
854                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
855                                 update_mmu_cache_pud(vma, addr, pud);
856                 }
857                 goto out_unlock;
858         }
859 
860         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
861         if (pfn_t_devmap(pfn))
862                 entry = pud_mkdevmap(entry);
863         if (write) {
864                 entry = pud_mkyoung(pud_mkdirty(entry));
865                 entry = maybe_pud_mkwrite(entry, vma);
866         }
867         set_pud_at(mm, addr, pud, entry);
868         update_mmu_cache_pud(vma, addr, pud);
869 
870 out_unlock:
871         spin_unlock(ptl);
872 }
873 
874 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
875 {
876         unsigned long addr = vmf->address & PUD_MASK;
877         struct vm_area_struct *vma = vmf->vma;
878         pgprot_t pgprot = vma->vm_page_prot;
879 
880         /*
881          * If we had pud_special, we could avoid all these restrictions,
882          * but we need to be consistent with PTEs and architectures that
883          * can't support a 'special' bit.
884          */
885         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
886                         !pfn_t_devmap(pfn));
887         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
888                                                 (VM_PFNMAP|VM_MIXEDMAP));
889         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
890 
891         if (addr < vma->vm_start || addr >= vma->vm_end)
892                 return VM_FAULT_SIGBUS;
893 
894         track_pfn_insert(vma, &pgprot, pfn);
895 
896         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
897         return VM_FAULT_NOPAGE;
898 }
899 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
900 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
901 
902 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
903                 pmd_t *pmd, int flags)
904 {
905         pmd_t _pmd;
906 
907         _pmd = pmd_mkyoung(*pmd);
908         if (flags & FOLL_WRITE)
909                 _pmd = pmd_mkdirty(_pmd);
910         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
911                                 pmd, _pmd, flags & FOLL_WRITE))
912                 update_mmu_cache_pmd(vma, addr, pmd);
913 }
914 
915 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
916                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
917 {
918         unsigned long pfn = pmd_pfn(*pmd);
919         struct mm_struct *mm = vma->vm_mm;
920         struct page *page;
921 
922         assert_spin_locked(pmd_lockptr(mm, pmd));
923 
924         /*
925          * When we COW a devmap PMD entry, we split it into PTEs, so we should
926          * not be in this function with `flags & FOLL_COW` set.
927          */
928         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
929 
930         if (flags & FOLL_WRITE && !pmd_write(*pmd))
931                 return NULL;
932 
933         if (pmd_present(*pmd) && pmd_devmap(*pmd))
934                 /* pass */;
935         else
936                 return NULL;
937 
938         if (flags & FOLL_TOUCH)
939                 touch_pmd(vma, addr, pmd, flags);
940 
941         /*
942          * device mapped pages can only be returned if the
943          * caller will manage the page reference count.
944          */
945         if (!(flags & FOLL_GET))
946                 return ERR_PTR(-EEXIST);
947 
948         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
949         *pgmap = get_dev_pagemap(pfn, *pgmap);
950         if (!*pgmap)
951                 return ERR_PTR(-EFAULT);
952         page = pfn_to_page(pfn);
953         get_page(page);
954 
955         return page;
956 }
957 
958 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
959                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
960                   struct vm_area_struct *vma)
961 {
962         spinlock_t *dst_ptl, *src_ptl;
963         struct page *src_page;
964         pmd_t pmd;
965         pgtable_t pgtable = NULL;
966         int ret = -ENOMEM;
967 
968         /* Skip if can be re-fill on fault */
969         if (!vma_is_anonymous(vma))
970                 return 0;
971 
972         pgtable = pte_alloc_one(dst_mm);
973         if (unlikely(!pgtable))
974                 goto out;
975 
976         dst_ptl = pmd_lock(dst_mm, dst_pmd);
977         src_ptl = pmd_lockptr(src_mm, src_pmd);
978         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
979 
980         ret = -EAGAIN;
981         pmd = *src_pmd;
982 
983 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
984         if (unlikely(is_swap_pmd(pmd))) {
985                 swp_entry_t entry = pmd_to_swp_entry(pmd);
986 
987                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
988                 if (is_write_migration_entry(entry)) {
989                         make_migration_entry_read(&entry);
990                         pmd = swp_entry_to_pmd(entry);
991                         if (pmd_swp_soft_dirty(*src_pmd))
992                                 pmd = pmd_swp_mksoft_dirty(pmd);
993                         set_pmd_at(src_mm, addr, src_pmd, pmd);
994                 }
995                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
996                 mm_inc_nr_ptes(dst_mm);
997                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
998                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
999                 ret = 0;
1000                 goto out_unlock;
1001         }
1002 #endif
1003 
1004         if (unlikely(!pmd_trans_huge(pmd))) {
1005                 pte_free(dst_mm, pgtable);
1006                 goto out_unlock;
1007         }
1008         /*
1009          * When page table lock is held, the huge zero pmd should not be
1010          * under splitting since we don't split the page itself, only pmd to
1011          * a page table.
1012          */
1013         if (is_huge_zero_pmd(pmd)) {
1014                 struct page *zero_page;
1015                 /*
1016                  * get_huge_zero_page() will never allocate a new page here,
1017                  * since we already have a zero page to copy. It just takes a
1018                  * reference.
1019                  */
1020                 zero_page = mm_get_huge_zero_page(dst_mm);
1021                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1022                                 zero_page);
1023                 ret = 0;
1024                 goto out_unlock;
1025         }
1026 
1027         src_page = pmd_page(pmd);
1028         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1029         get_page(src_page);
1030         page_dup_rmap(src_page, true);
1031         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1032         mm_inc_nr_ptes(dst_mm);
1033         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1034 
1035         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1036         pmd = pmd_mkold(pmd_wrprotect(pmd));
1037         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1038 
1039         ret = 0;
1040 out_unlock:
1041         spin_unlock(src_ptl);
1042         spin_unlock(dst_ptl);
1043 out:
1044         return ret;
1045 }
1046 
1047 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1048 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1049                 pud_t *pud, int flags)
1050 {
1051         pud_t _pud;
1052 
1053         _pud = pud_mkyoung(*pud);
1054         if (flags & FOLL_WRITE)
1055                 _pud = pud_mkdirty(_pud);
1056         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1057                                 pud, _pud, flags & FOLL_WRITE))
1058                 update_mmu_cache_pud(vma, addr, pud);
1059 }
1060 
1061 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1062                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1063 {
1064         unsigned long pfn = pud_pfn(*pud);
1065         struct mm_struct *mm = vma->vm_mm;
1066         struct page *page;
1067 
1068         assert_spin_locked(pud_lockptr(mm, pud));
1069 
1070         if (flags & FOLL_WRITE && !pud_write(*pud))
1071                 return NULL;
1072 
1073         if (pud_present(*pud) && pud_devmap(*pud))
1074                 /* pass */;
1075         else
1076                 return NULL;
1077 
1078         if (flags & FOLL_TOUCH)
1079                 touch_pud(vma, addr, pud, flags);
1080 
1081         /*
1082          * device mapped pages can only be returned if the
1083          * caller will manage the page reference count.
1084          */
1085         if (!(flags & FOLL_GET))
1086                 return ERR_PTR(-EEXIST);
1087 
1088         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1089         *pgmap = get_dev_pagemap(pfn, *pgmap);
1090         if (!*pgmap)
1091                 return ERR_PTR(-EFAULT);
1092         page = pfn_to_page(pfn);
1093         get_page(page);
1094 
1095         return page;
1096 }
1097 
1098 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1099                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1100                   struct vm_area_struct *vma)
1101 {
1102         spinlock_t *dst_ptl, *src_ptl;
1103         pud_t pud;
1104         int ret;
1105 
1106         dst_ptl = pud_lock(dst_mm, dst_pud);
1107         src_ptl = pud_lockptr(src_mm, src_pud);
1108         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1109 
1110         ret = -EAGAIN;
1111         pud = *src_pud;
1112         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1113                 goto out_unlock;
1114 
1115         /*
1116          * When page table lock is held, the huge zero pud should not be
1117          * under splitting since we don't split the page itself, only pud to
1118          * a page table.
1119          */
1120         if (is_huge_zero_pud(pud)) {
1121                 /* No huge zero pud yet */
1122         }
1123 
1124         pudp_set_wrprotect(src_mm, addr, src_pud);
1125         pud = pud_mkold(pud_wrprotect(pud));
1126         set_pud_at(dst_mm, addr, dst_pud, pud);
1127 
1128         ret = 0;
1129 out_unlock:
1130         spin_unlock(src_ptl);
1131         spin_unlock(dst_ptl);
1132         return ret;
1133 }
1134 
1135 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1136 {
1137         pud_t entry;
1138         unsigned long haddr;
1139         bool write = vmf->flags & FAULT_FLAG_WRITE;
1140 
1141         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1142         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1143                 goto unlock;
1144 
1145         entry = pud_mkyoung(orig_pud);
1146         if (write)
1147                 entry = pud_mkdirty(entry);
1148         haddr = vmf->address & HPAGE_PUD_MASK;
1149         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1150                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1151 
1152 unlock:
1153         spin_unlock(vmf->ptl);
1154 }
1155 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1156 
1157 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1158 {
1159         pmd_t entry;
1160         unsigned long haddr;
1161         bool write = vmf->flags & FAULT_FLAG_WRITE;
1162 
1163         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1164         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1165                 goto unlock;
1166 
1167         entry = pmd_mkyoung(orig_pmd);
1168         if (write)
1169                 entry = pmd_mkdirty(entry);
1170         haddr = vmf->address & HPAGE_PMD_MASK;
1171         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1172                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1173 
1174 unlock:
1175         spin_unlock(vmf->ptl);
1176 }
1177 
1178 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1179                         pmd_t orig_pmd, struct page *page)
1180 {
1181         struct vm_area_struct *vma = vmf->vma;
1182         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1183         struct mem_cgroup *memcg;
1184         pgtable_t pgtable;
1185         pmd_t _pmd;
1186         int i;
1187         vm_fault_t ret = 0;
1188         struct page **pages;
1189         struct mmu_notifier_range range;
1190 
1191         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1192                               GFP_KERNEL);
1193         if (unlikely(!pages)) {
1194                 ret |= VM_FAULT_OOM;
1195                 goto out;
1196         }
1197 
1198         for (i = 0; i < HPAGE_PMD_NR; i++) {
1199                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1200                                                vmf->address, page_to_nid(page));
1201                 if (unlikely(!pages[i] ||
1202                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1203                                      GFP_KERNEL, &memcg, false))) {
1204                         if (pages[i])
1205                                 put_page(pages[i]);
1206                         while (--i >= 0) {
1207                                 memcg = (void *)page_private(pages[i]);
1208                                 set_page_private(pages[i], 0);
1209                                 mem_cgroup_cancel_charge(pages[i], memcg,
1210                                                 false);
1211                                 put_page(pages[i]);
1212                         }
1213                         kfree(pages);
1214                         ret |= VM_FAULT_OOM;
1215                         goto out;
1216                 }
1217                 set_page_private(pages[i], (unsigned long)memcg);
1218         }
1219 
1220         for (i = 0; i < HPAGE_PMD_NR; i++) {
1221                 copy_user_highpage(pages[i], page + i,
1222                                    haddr + PAGE_SIZE * i, vma);
1223                 __SetPageUptodate(pages[i]);
1224                 cond_resched();
1225         }
1226 
1227         mmu_notifier_range_init(&range, vma->vm_mm, haddr,
1228                                 haddr + HPAGE_PMD_SIZE);
1229         mmu_notifier_invalidate_range_start(&range);
1230 
1231         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1232         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1233                 goto out_free_pages;
1234         VM_BUG_ON_PAGE(!PageHead(page), page);
1235 
1236         /*
1237          * Leave pmd empty until pte is filled note we must notify here as
1238          * concurrent CPU thread might write to new page before the call to
1239          * mmu_notifier_invalidate_range_end() happens which can lead to a
1240          * device seeing memory write in different order than CPU.
1241          *
1242          * See Documentation/vm/mmu_notifier.rst
1243          */
1244         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1245 
1246         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1247         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1248 
1249         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1250                 pte_t entry;
1251                 entry = mk_pte(pages[i], vma->vm_page_prot);
1252                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1253                 memcg = (void *)page_private(pages[i]);
1254                 set_page_private(pages[i], 0);
1255                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1256                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1257                 lru_cache_add_active_or_unevictable(pages[i], vma);
1258                 vmf->pte = pte_offset_map(&_pmd, haddr);
1259                 VM_BUG_ON(!pte_none(*vmf->pte));
1260                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1261                 pte_unmap(vmf->pte);
1262         }
1263         kfree(pages);
1264 
1265         smp_wmb(); /* make pte visible before pmd */
1266         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1267         page_remove_rmap(page, true);
1268         spin_unlock(vmf->ptl);
1269 
1270         /*
1271          * No need to double call mmu_notifier->invalidate_range() callback as
1272          * the above pmdp_huge_clear_flush_notify() did already call it.
1273          */
1274         mmu_notifier_invalidate_range_only_end(&range);
1275 
1276         ret |= VM_FAULT_WRITE;
1277         put_page(page);
1278 
1279 out:
1280         return ret;
1281 
1282 out_free_pages:
1283         spin_unlock(vmf->ptl);
1284         mmu_notifier_invalidate_range_end(&range);
1285         for (i = 0; i < HPAGE_PMD_NR; i++) {
1286                 memcg = (void *)page_private(pages[i]);
1287                 set_page_private(pages[i], 0);
1288                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1289                 put_page(pages[i]);
1290         }
1291         kfree(pages);
1292         goto out;
1293 }
1294 
1295 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1296 {
1297         struct vm_area_struct *vma = vmf->vma;
1298         struct page *page = NULL, *new_page;
1299         struct mem_cgroup *memcg;
1300         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1301         struct mmu_notifier_range range;
1302         gfp_t huge_gfp;                 /* for allocation and charge */
1303         vm_fault_t ret = 0;
1304 
1305         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1306         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1307         if (is_huge_zero_pmd(orig_pmd))
1308                 goto alloc;
1309         spin_lock(vmf->ptl);
1310         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1311                 goto out_unlock;
1312 
1313         page = pmd_page(orig_pmd);
1314         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1315         /*
1316          * We can only reuse the page if nobody else maps the huge page or it's
1317          * part.
1318          */
1319         if (!trylock_page(page)) {
1320                 get_page(page);
1321                 spin_unlock(vmf->ptl);
1322                 lock_page(page);
1323                 spin_lock(vmf->ptl);
1324                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1325                         unlock_page(page);
1326                         put_page(page);
1327                         goto out_unlock;
1328                 }
1329                 put_page(page);
1330         }
1331         if (reuse_swap_page(page, NULL)) {
1332                 pmd_t entry;
1333                 entry = pmd_mkyoung(orig_pmd);
1334                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1335                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1336                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1337                 ret |= VM_FAULT_WRITE;
1338                 unlock_page(page);
1339                 goto out_unlock;
1340         }
1341         unlock_page(page);
1342         get_page(page);
1343         spin_unlock(vmf->ptl);
1344 alloc:
1345         if (__transparent_hugepage_enabled(vma) &&
1346             !transparent_hugepage_debug_cow()) {
1347                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1348                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1349         } else
1350                 new_page = NULL;
1351 
1352         if (likely(new_page)) {
1353                 prep_transhuge_page(new_page);
1354         } else {
1355                 if (!page) {
1356                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1357                         ret |= VM_FAULT_FALLBACK;
1358                 } else {
1359                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1360                         if (ret & VM_FAULT_OOM) {
1361                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1362                                 ret |= VM_FAULT_FALLBACK;
1363                         }
1364                         put_page(page);
1365                 }
1366                 count_vm_event(THP_FAULT_FALLBACK);
1367                 goto out;
1368         }
1369 
1370         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1371                                         huge_gfp, &memcg, true))) {
1372                 put_page(new_page);
1373                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1374                 if (page)
1375                         put_page(page);
1376                 ret |= VM_FAULT_FALLBACK;
1377                 count_vm_event(THP_FAULT_FALLBACK);
1378                 goto out;
1379         }
1380 
1381         count_vm_event(THP_FAULT_ALLOC);
1382         count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1383 
1384         if (!page)
1385                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1386         else
1387                 copy_user_huge_page(new_page, page, vmf->address,
1388                                     vma, HPAGE_PMD_NR);
1389         __SetPageUptodate(new_page);
1390 
1391         mmu_notifier_range_init(&range, vma->vm_mm, haddr,
1392                                 haddr + HPAGE_PMD_SIZE);
1393         mmu_notifier_invalidate_range_start(&range);
1394 
1395         spin_lock(vmf->ptl);
1396         if (page)
1397                 put_page(page);
1398         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1399                 spin_unlock(vmf->ptl);
1400                 mem_cgroup_cancel_charge(new_page, memcg, true);
1401                 put_page(new_page);
1402                 goto out_mn;
1403         } else {
1404                 pmd_t entry;
1405                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1406                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1407                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1408                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1409                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1410                 lru_cache_add_active_or_unevictable(new_page, vma);
1411                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1412                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1413                 if (!page) {
1414                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1415                 } else {
1416                         VM_BUG_ON_PAGE(!PageHead(page), page);
1417                         page_remove_rmap(page, true);
1418                         put_page(page);
1419                 }
1420                 ret |= VM_FAULT_WRITE;
1421         }
1422         spin_unlock(vmf->ptl);
1423 out_mn:
1424         /*
1425          * No need to double call mmu_notifier->invalidate_range() callback as
1426          * the above pmdp_huge_clear_flush_notify() did already call it.
1427          */
1428         mmu_notifier_invalidate_range_only_end(&range);
1429 out:
1430         return ret;
1431 out_unlock:
1432         spin_unlock(vmf->ptl);
1433         return ret;
1434 }
1435 
1436 /*
1437  * FOLL_FORCE can write to even unwritable pmd's, but only
1438  * after we've gone through a COW cycle and they are dirty.
1439  */
1440 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1441 {
1442         return pmd_write(pmd) ||
1443                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1444 }
1445 
1446 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1447                                    unsigned long addr,
1448                                    pmd_t *pmd,
1449                                    unsigned int flags)
1450 {
1451         struct mm_struct *mm = vma->vm_mm;
1452         struct page *page = NULL;
1453 
1454         assert_spin_locked(pmd_lockptr(mm, pmd));
1455 
1456         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1457                 goto out;
1458 
1459         /* Avoid dumping huge zero page */
1460         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1461                 return ERR_PTR(-EFAULT);
1462 
1463         /* Full NUMA hinting faults to serialise migration in fault paths */
1464         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1465                 goto out;
1466 
1467         page = pmd_page(*pmd);
1468         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1469         if (flags & FOLL_TOUCH)
1470                 touch_pmd(vma, addr, pmd, flags);
1471         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1472                 /*
1473                  * We don't mlock() pte-mapped THPs. This way we can avoid
1474                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1475                  *
1476                  * For anon THP:
1477                  *
1478                  * In most cases the pmd is the only mapping of the page as we
1479                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1480                  * writable private mappings in populate_vma_page_range().
1481                  *
1482                  * The only scenario when we have the page shared here is if we
1483                  * mlocking read-only mapping shared over fork(). We skip
1484                  * mlocking such pages.
1485                  *
1486                  * For file THP:
1487                  *
1488                  * We can expect PageDoubleMap() to be stable under page lock:
1489                  * for file pages we set it in page_add_file_rmap(), which
1490                  * requires page to be locked.
1491                  */
1492 
1493                 if (PageAnon(page) && compound_mapcount(page) != 1)
1494                         goto skip_mlock;
1495                 if (PageDoubleMap(page) || !page->mapping)
1496                         goto skip_mlock;
1497                 if (!trylock_page(page))
1498                         goto skip_mlock;
1499                 lru_add_drain();
1500                 if (page->mapping && !PageDoubleMap(page))
1501                         mlock_vma_page(page);
1502                 unlock_page(page);
1503         }
1504 skip_mlock:
1505         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1506         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1507         if (flags & FOLL_GET)
1508                 get_page(page);
1509 
1510 out:
1511         return page;
1512 }
1513 
1514 /* NUMA hinting page fault entry point for trans huge pmds */
1515 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1516 {
1517         struct vm_area_struct *vma = vmf->vma;
1518         struct anon_vma *anon_vma = NULL;
1519         struct page *page;
1520         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1521         int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1522         int target_nid, last_cpupid = -1;
1523         bool page_locked;
1524         bool migrated = false;
1525         bool was_writable;
1526         int flags = 0;
1527 
1528         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1529         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1530                 goto out_unlock;
1531 
1532         /*
1533          * If there are potential migrations, wait for completion and retry
1534          * without disrupting NUMA hinting information. Do not relock and
1535          * check_same as the page may no longer be mapped.
1536          */
1537         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1538                 page = pmd_page(*vmf->pmd);
1539                 if (!get_page_unless_zero(page))
1540                         goto out_unlock;
1541                 spin_unlock(vmf->ptl);
1542                 put_and_wait_on_page_locked(page);
1543                 goto out;
1544         }
1545 
1546         page = pmd_page(pmd);
1547         BUG_ON(is_huge_zero_page(page));
1548         page_nid = page_to_nid(page);
1549         last_cpupid = page_cpupid_last(page);
1550         count_vm_numa_event(NUMA_HINT_FAULTS);
1551         if (page_nid == this_nid) {
1552                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1553                 flags |= TNF_FAULT_LOCAL;
1554         }
1555 
1556         /* See similar comment in do_numa_page for explanation */
1557         if (!pmd_savedwrite(pmd))
1558                 flags |= TNF_NO_GROUP;
1559 
1560         /*
1561          * Acquire the page lock to serialise THP migrations but avoid dropping
1562          * page_table_lock if at all possible
1563          */
1564         page_locked = trylock_page(page);
1565         target_nid = mpol_misplaced(page, vma, haddr);
1566         if (target_nid == NUMA_NO_NODE) {
1567                 /* If the page was locked, there are no parallel migrations */
1568                 if (page_locked)
1569                         goto clear_pmdnuma;
1570         }
1571 
1572         /* Migration could have started since the pmd_trans_migrating check */
1573         if (!page_locked) {
1574                 page_nid = NUMA_NO_NODE;
1575                 if (!get_page_unless_zero(page))
1576                         goto out_unlock;
1577                 spin_unlock(vmf->ptl);
1578                 put_and_wait_on_page_locked(page);
1579                 goto out;
1580         }
1581 
1582         /*
1583          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1584          * to serialises splits
1585          */
1586         get_page(page);
1587         spin_unlock(vmf->ptl);
1588         anon_vma = page_lock_anon_vma_read(page);
1589 
1590         /* Confirm the PMD did not change while page_table_lock was released */
1591         spin_lock(vmf->ptl);
1592         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1593                 unlock_page(page);
1594                 put_page(page);
1595                 page_nid = NUMA_NO_NODE;
1596                 goto out_unlock;
1597         }
1598 
1599         /* Bail if we fail to protect against THP splits for any reason */
1600         if (unlikely(!anon_vma)) {
1601                 put_page(page);
1602                 page_nid = NUMA_NO_NODE;
1603                 goto clear_pmdnuma;
1604         }
1605 
1606         /*
1607          * Since we took the NUMA fault, we must have observed the !accessible
1608          * bit. Make sure all other CPUs agree with that, to avoid them
1609          * modifying the page we're about to migrate.
1610          *
1611          * Must be done under PTL such that we'll observe the relevant
1612          * inc_tlb_flush_pending().
1613          *
1614          * We are not sure a pending tlb flush here is for a huge page
1615          * mapping or not. Hence use the tlb range variant
1616          */
1617         if (mm_tlb_flush_pending(vma->vm_mm)) {
1618                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1619                 /*
1620                  * change_huge_pmd() released the pmd lock before
1621                  * invalidating the secondary MMUs sharing the primary
1622                  * MMU pagetables (with ->invalidate_range()). The
1623                  * mmu_notifier_invalidate_range_end() (which
1624                  * internally calls ->invalidate_range()) in
1625                  * change_pmd_range() will run after us, so we can't
1626                  * rely on it here and we need an explicit invalidate.
1627                  */
1628                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1629                                               haddr + HPAGE_PMD_SIZE);
1630         }
1631 
1632         /*
1633          * Migrate the THP to the requested node, returns with page unlocked
1634          * and access rights restored.
1635          */
1636         spin_unlock(vmf->ptl);
1637 
1638         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1639                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1640         if (migrated) {
1641                 flags |= TNF_MIGRATED;
1642                 page_nid = target_nid;
1643         } else
1644                 flags |= TNF_MIGRATE_FAIL;
1645 
1646         goto out;
1647 clear_pmdnuma:
1648         BUG_ON(!PageLocked(page));
1649         was_writable = pmd_savedwrite(pmd);
1650         pmd = pmd_modify(pmd, vma->vm_page_prot);
1651         pmd = pmd_mkyoung(pmd);
1652         if (was_writable)
1653                 pmd = pmd_mkwrite(pmd);
1654         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1655         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1656         unlock_page(page);
1657 out_unlock:
1658         spin_unlock(vmf->ptl);
1659 
1660 out:
1661         if (anon_vma)
1662                 page_unlock_anon_vma_read(anon_vma);
1663 
1664         if (page_nid != NUMA_NO_NODE)
1665                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1666                                 flags);
1667 
1668         return 0;
1669 }
1670 
1671 /*
1672  * Return true if we do MADV_FREE successfully on entire pmd page.
1673  * Otherwise, return false.
1674  */
1675 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1676                 pmd_t *pmd, unsigned long addr, unsigned long next)
1677 {
1678         spinlock_t *ptl;
1679         pmd_t orig_pmd;
1680         struct page *page;
1681         struct mm_struct *mm = tlb->mm;
1682         bool ret = false;
1683 
1684         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1685 
1686         ptl = pmd_trans_huge_lock(pmd, vma);
1687         if (!ptl)
1688                 goto out_unlocked;
1689 
1690         orig_pmd = *pmd;
1691         if (is_huge_zero_pmd(orig_pmd))
1692                 goto out;
1693 
1694         if (unlikely(!pmd_present(orig_pmd))) {
1695                 VM_BUG_ON(thp_migration_supported() &&
1696                                   !is_pmd_migration_entry(orig_pmd));
1697                 goto out;
1698         }
1699 
1700         page = pmd_page(orig_pmd);
1701         /*
1702          * If other processes are mapping this page, we couldn't discard
1703          * the page unless they all do MADV_FREE so let's skip the page.
1704          */
1705         if (page_mapcount(page) != 1)
1706                 goto out;
1707 
1708         if (!trylock_page(page))
1709                 goto out;
1710 
1711         /*
1712          * If user want to discard part-pages of THP, split it so MADV_FREE
1713          * will deactivate only them.
1714          */
1715         if (next - addr != HPAGE_PMD_SIZE) {
1716                 get_page(page);
1717                 spin_unlock(ptl);
1718                 split_huge_page(page);
1719                 unlock_page(page);
1720                 put_page(page);
1721                 goto out_unlocked;
1722         }
1723 
1724         if (PageDirty(page))
1725                 ClearPageDirty(page);
1726         unlock_page(page);
1727 
1728         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1729                 pmdp_invalidate(vma, addr, pmd);
1730                 orig_pmd = pmd_mkold(orig_pmd);
1731                 orig_pmd = pmd_mkclean(orig_pmd);
1732 
1733                 set_pmd_at(mm, addr, pmd, orig_pmd);
1734                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1735         }
1736 
1737         mark_page_lazyfree(page);
1738         ret = true;
1739 out:
1740         spin_unlock(ptl);
1741 out_unlocked:
1742         return ret;
1743 }
1744 
1745 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1746 {
1747         pgtable_t pgtable;
1748 
1749         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1750         pte_free(mm, pgtable);
1751         mm_dec_nr_ptes(mm);
1752 }
1753 
1754 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1755                  pmd_t *pmd, unsigned long addr)
1756 {
1757         pmd_t orig_pmd;
1758         spinlock_t *ptl;
1759 
1760         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1761 
1762         ptl = __pmd_trans_huge_lock(pmd, vma);
1763         if (!ptl)
1764                 return 0;
1765         /*
1766          * For architectures like ppc64 we look at deposited pgtable
1767          * when calling pmdp_huge_get_and_clear. So do the
1768          * pgtable_trans_huge_withdraw after finishing pmdp related
1769          * operations.
1770          */
1771         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1772                         tlb->fullmm);
1773         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1774         if (vma_is_dax(vma)) {
1775                 if (arch_needs_pgtable_deposit())
1776                         zap_deposited_table(tlb->mm, pmd);
1777                 spin_unlock(ptl);
1778                 if (is_huge_zero_pmd(orig_pmd))
1779                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1780         } else if (is_huge_zero_pmd(orig_pmd)) {
1781                 zap_deposited_table(tlb->mm, pmd);
1782                 spin_unlock(ptl);
1783                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1784         } else {
1785                 struct page *page = NULL;
1786                 int flush_needed = 1;
1787 
1788                 if (pmd_present(orig_pmd)) {
1789                         page = pmd_page(orig_pmd);
1790                         page_remove_rmap(page, true);
1791                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1792                         VM_BUG_ON_PAGE(!PageHead(page), page);
1793                 } else if (thp_migration_supported()) {
1794                         swp_entry_t entry;
1795 
1796                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1797                         entry = pmd_to_swp_entry(orig_pmd);
1798                         page = pfn_to_page(swp_offset(entry));
1799                         flush_needed = 0;
1800                 } else
1801                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1802 
1803                 if (PageAnon(page)) {
1804                         zap_deposited_table(tlb->mm, pmd);
1805                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1806                 } else {
1807                         if (arch_needs_pgtable_deposit())
1808                                 zap_deposited_table(tlb->mm, pmd);
1809                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1810                 }
1811 
1812                 spin_unlock(ptl);
1813                 if (flush_needed)
1814                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1815         }
1816         return 1;
1817 }
1818 
1819 #ifndef pmd_move_must_withdraw
1820 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1821                                          spinlock_t *old_pmd_ptl,
1822                                          struct vm_area_struct *vma)
1823 {
1824         /*
1825          * With split pmd lock we also need to move preallocated
1826          * PTE page table if new_pmd is on different PMD page table.
1827          *
1828          * We also don't deposit and withdraw tables for file pages.
1829          */
1830         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1831 }
1832 #endif
1833 
1834 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1835 {
1836 #ifdef CONFIG_MEM_SOFT_DIRTY
1837         if (unlikely(is_pmd_migration_entry(pmd)))
1838                 pmd = pmd_swp_mksoft_dirty(pmd);
1839         else if (pmd_present(pmd))
1840                 pmd = pmd_mksoft_dirty(pmd);
1841 #endif
1842         return pmd;
1843 }
1844 
1845 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1846                   unsigned long new_addr, unsigned long old_end,
1847                   pmd_t *old_pmd, pmd_t *new_pmd)
1848 {
1849         spinlock_t *old_ptl, *new_ptl;
1850         pmd_t pmd;
1851         struct mm_struct *mm = vma->vm_mm;
1852         bool force_flush = false;
1853 
1854         if ((old_addr & ~HPAGE_PMD_MASK) ||
1855             (new_addr & ~HPAGE_PMD_MASK) ||
1856             old_end - old_addr < HPAGE_PMD_SIZE)
1857                 return false;
1858 
1859         /*
1860          * The destination pmd shouldn't be established, free_pgtables()
1861          * should have release it.
1862          */
1863         if (WARN_ON(!pmd_none(*new_pmd))) {
1864                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1865                 return false;
1866         }
1867 
1868         /*
1869          * We don't have to worry about the ordering of src and dst
1870          * ptlocks because exclusive mmap_sem prevents deadlock.
1871          */
1872         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1873         if (old_ptl) {
1874                 new_ptl = pmd_lockptr(mm, new_pmd);
1875                 if (new_ptl != old_ptl)
1876                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1877                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1878                 if (pmd_present(pmd))
1879                         force_flush = true;
1880                 VM_BUG_ON(!pmd_none(*new_pmd));
1881 
1882                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1883                         pgtable_t pgtable;
1884                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1885                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1886                 }
1887                 pmd = move_soft_dirty_pmd(pmd);
1888                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1889                 if (force_flush)
1890                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1891                 if (new_ptl != old_ptl)
1892                         spin_unlock(new_ptl);
1893                 spin_unlock(old_ptl);
1894                 return true;
1895         }
1896         return false;
1897 }
1898 
1899 /*
1900  * Returns
1901  *  - 0 if PMD could not be locked
1902  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1903  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1904  */
1905 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1906                 unsigned long addr, pgprot_t newprot, int prot_numa)
1907 {
1908         struct mm_struct *mm = vma->vm_mm;
1909         spinlock_t *ptl;
1910         pmd_t entry;
1911         bool preserve_write;
1912         int ret;
1913 
1914         ptl = __pmd_trans_huge_lock(pmd, vma);
1915         if (!ptl)
1916                 return 0;
1917 
1918         preserve_write = prot_numa && pmd_write(*pmd);
1919         ret = 1;
1920 
1921 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1922         if (is_swap_pmd(*pmd)) {
1923                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1924 
1925                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1926                 if (is_write_migration_entry(entry)) {
1927                         pmd_t newpmd;
1928                         /*
1929                          * A protection check is difficult so
1930                          * just be safe and disable write
1931                          */
1932                         make_migration_entry_read(&entry);
1933                         newpmd = swp_entry_to_pmd(entry);
1934                         if (pmd_swp_soft_dirty(*pmd))
1935                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1936                         set_pmd_at(mm, addr, pmd, newpmd);
1937                 }
1938                 goto unlock;
1939         }
1940 #endif
1941 
1942         /*
1943          * Avoid trapping faults against the zero page. The read-only
1944          * data is likely to be read-cached on the local CPU and
1945          * local/remote hits to the zero page are not interesting.
1946          */
1947         if (prot_numa && is_huge_zero_pmd(*pmd))
1948                 goto unlock;
1949 
1950         if (prot_numa && pmd_protnone(*pmd))
1951                 goto unlock;
1952 
1953         /*
1954          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1955          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1956          * which is also under down_read(mmap_sem):
1957          *
1958          *      CPU0:                           CPU1:
1959          *                              change_huge_pmd(prot_numa=1)
1960          *                               pmdp_huge_get_and_clear_notify()
1961          * madvise_dontneed()
1962          *  zap_pmd_range()
1963          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1964          *   // skip the pmd
1965          *                               set_pmd_at();
1966          *                               // pmd is re-established
1967          *
1968          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1969          * which may break userspace.
1970          *
1971          * pmdp_invalidate() is required to make sure we don't miss
1972          * dirty/young flags set by hardware.
1973          */
1974         entry = pmdp_invalidate(vma, addr, pmd);
1975 
1976         entry = pmd_modify(entry, newprot);
1977         if (preserve_write)
1978                 entry = pmd_mk_savedwrite(entry);
1979         ret = HPAGE_PMD_NR;
1980         set_pmd_at(mm, addr, pmd, entry);
1981         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1982 unlock:
1983         spin_unlock(ptl);
1984         return ret;
1985 }
1986 
1987 /*
1988  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1989  *
1990  * Note that if it returns page table lock pointer, this routine returns without
1991  * unlocking page table lock. So callers must unlock it.
1992  */
1993 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1994 {
1995         spinlock_t *ptl;
1996         ptl = pmd_lock(vma->vm_mm, pmd);
1997         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1998                         pmd_devmap(*pmd)))
1999                 return ptl;
2000         spin_unlock(ptl);
2001         return NULL;
2002 }
2003 
2004 /*
2005  * Returns true if a given pud maps a thp, false otherwise.
2006  *
2007  * Note that if it returns true, this routine returns without unlocking page
2008  * table lock. So callers must unlock it.
2009  */
2010 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2011 {
2012         spinlock_t *ptl;
2013 
2014         ptl = pud_lock(vma->vm_mm, pud);
2015         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2016                 return ptl;
2017         spin_unlock(ptl);
2018         return NULL;
2019 }
2020 
2021 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2022 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2023                  pud_t *pud, unsigned long addr)
2024 {
2025         spinlock_t *ptl;
2026 
2027         ptl = __pud_trans_huge_lock(pud, vma);
2028         if (!ptl)
2029                 return 0;
2030         /*
2031          * For architectures like ppc64 we look at deposited pgtable
2032          * when calling pudp_huge_get_and_clear. So do the
2033          * pgtable_trans_huge_withdraw after finishing pudp related
2034          * operations.
2035          */
2036         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2037         tlb_remove_pud_tlb_entry(tlb, pud, addr);
2038         if (vma_is_dax(vma)) {
2039                 spin_unlock(ptl);
2040                 /* No zero page support yet */
2041         } else {
2042                 /* No support for anonymous PUD pages yet */
2043                 BUG();
2044         }
2045         return 1;
2046 }
2047 
2048 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2049                 unsigned long haddr)
2050 {
2051         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2052         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2053         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2054         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2055 
2056         count_vm_event(THP_SPLIT_PUD);
2057 
2058         pudp_huge_clear_flush_notify(vma, haddr, pud);
2059 }
2060 
2061 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2062                 unsigned long address)
2063 {
2064         spinlock_t *ptl;
2065         struct mmu_notifier_range range;
2066 
2067         mmu_notifier_range_init(&range, vma->vm_mm, address & HPAGE_PUD_MASK,
2068                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2069         mmu_notifier_invalidate_range_start(&range);
2070         ptl = pud_lock(vma->vm_mm, pud);
2071         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2072                 goto out;
2073         __split_huge_pud_locked(vma, pud, range.start);
2074 
2075 out:
2076         spin_unlock(ptl);
2077         /*
2078          * No need to double call mmu_notifier->invalidate_range() callback as
2079          * the above pudp_huge_clear_flush_notify() did already call it.
2080          */
2081         mmu_notifier_invalidate_range_only_end(&range);
2082 }
2083 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2084 
2085 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2086                 unsigned long haddr, pmd_t *pmd)
2087 {
2088         struct mm_struct *mm = vma->vm_mm;
2089         pgtable_t pgtable;
2090         pmd_t _pmd;
2091         int i;
2092 
2093         /*
2094          * Leave pmd empty until pte is filled note that it is fine to delay
2095          * notification until mmu_notifier_invalidate_range_end() as we are
2096          * replacing a zero pmd write protected page with a zero pte write
2097          * protected page.
2098          *
2099          * See Documentation/vm/mmu_notifier.rst
2100          */
2101         pmdp_huge_clear_flush(vma, haddr, pmd);
2102 
2103         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2104         pmd_populate(mm, &_pmd, pgtable);
2105 
2106         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2107                 pte_t *pte, entry;
2108                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2109                 entry = pte_mkspecial(entry);
2110                 pte = pte_offset_map(&_pmd, haddr);
2111                 VM_BUG_ON(!pte_none(*pte));
2112                 set_pte_at(mm, haddr, pte, entry);
2113                 pte_unmap(pte);
2114         }
2115         smp_wmb(); /* make pte visible before pmd */
2116         pmd_populate(mm, pmd, pgtable);
2117 }
2118 
2119 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2120                 unsigned long haddr, bool freeze)
2121 {
2122         struct mm_struct *mm = vma->vm_mm;
2123         struct page *page;
2124         pgtable_t pgtable;
2125         pmd_t old_pmd, _pmd;
2126         bool young, write, soft_dirty, pmd_migration = false;
2127         unsigned long addr;
2128         int i;
2129 
2130         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2131         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2132         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2133         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2134                                 && !pmd_devmap(*pmd));
2135 
2136         count_vm_event(THP_SPLIT_PMD);
2137 
2138         if (!vma_is_anonymous(vma)) {
2139                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2140                 /*
2141                  * We are going to unmap this huge page. So
2142                  * just go ahead and zap it
2143                  */
2144                 if (arch_needs_pgtable_deposit())
2145                         zap_deposited_table(mm, pmd);
2146                 if (vma_is_dax(vma))
2147                         return;
2148                 page = pmd_page(_pmd);
2149                 if (!PageDirty(page) && pmd_dirty(_pmd))
2150                         set_page_dirty(page);
2151                 if (!PageReferenced(page) && pmd_young(_pmd))
2152                         SetPageReferenced(page);
2153                 page_remove_rmap(page, true);
2154                 put_page(page);
2155                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2156                 return;
2157         } else if (is_huge_zero_pmd(*pmd)) {
2158                 /*
2159                  * FIXME: Do we want to invalidate secondary mmu by calling
2160                  * mmu_notifier_invalidate_range() see comments below inside
2161                  * __split_huge_pmd() ?
2162                  *
2163                  * We are going from a zero huge page write protected to zero
2164                  * small page also write protected so it does not seems useful
2165                  * to invalidate secondary mmu at this time.
2166                  */
2167                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2168         }
2169 
2170         /*
2171          * Up to this point the pmd is present and huge and userland has the
2172          * whole access to the hugepage during the split (which happens in
2173          * place). If we overwrite the pmd with the not-huge version pointing
2174          * to the pte here (which of course we could if all CPUs were bug
2175          * free), userland could trigger a small page size TLB miss on the
2176          * small sized TLB while the hugepage TLB entry is still established in
2177          * the huge TLB. Some CPU doesn't like that.
2178          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2179          * 383 on page 93. Intel should be safe but is also warns that it's
2180          * only safe if the permission and cache attributes of the two entries
2181          * loaded in the two TLB is identical (which should be the case here).
2182          * But it is generally safer to never allow small and huge TLB entries
2183          * for the same virtual address to be loaded simultaneously. So instead
2184          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2185          * current pmd notpresent (atomically because here the pmd_trans_huge
2186          * must remain set at all times on the pmd until the split is complete
2187          * for this pmd), then we flush the SMP TLB and finally we write the
2188          * non-huge version of the pmd entry with pmd_populate.
2189          */
2190         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2191 
2192         pmd_migration = is_pmd_migration_entry(old_pmd);
2193         if (unlikely(pmd_migration)) {
2194                 swp_entry_t entry;
2195 
2196                 entry = pmd_to_swp_entry(old_pmd);
2197                 page = pfn_to_page(swp_offset(entry));
2198                 write = is_write_migration_entry(entry);
2199                 young = false;
2200                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2201         } else {
2202                 page = pmd_page(old_pmd);
2203                 if (pmd_dirty(old_pmd))
2204                         SetPageDirty(page);
2205                 write = pmd_write(old_pmd);
2206                 young = pmd_young(old_pmd);
2207                 soft_dirty = pmd_soft_dirty(old_pmd);
2208         }
2209         VM_BUG_ON_PAGE(!page_count(page), page);
2210         page_ref_add(page, HPAGE_PMD_NR - 1);
2211 
2212         /*
2213          * Withdraw the table only after we mark the pmd entry invalid.
2214          * This's critical for some architectures (Power).
2215          */
2216         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2217         pmd_populate(mm, &_pmd, pgtable);
2218 
2219         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2220                 pte_t entry, *pte;
2221                 /*
2222                  * Note that NUMA hinting access restrictions are not
2223                  * transferred to avoid any possibility of altering
2224                  * permissions across VMAs.
2225                  */
2226                 if (freeze || pmd_migration) {
2227                         swp_entry_t swp_entry;
2228                         swp_entry = make_migration_entry(page + i, write);
2229                         entry = swp_entry_to_pte(swp_entry);
2230                         if (soft_dirty)
2231                                 entry = pte_swp_mksoft_dirty(entry);
2232                 } else {
2233                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2234                         entry = maybe_mkwrite(entry, vma);
2235                         if (!write)
2236                                 entry = pte_wrprotect(entry);
2237                         if (!young)
2238                                 entry = pte_mkold(entry);
2239                         if (soft_dirty)
2240                                 entry = pte_mksoft_dirty(entry);
2241                 }
2242                 pte = pte_offset_map(&_pmd, addr);
2243                 BUG_ON(!pte_none(*pte));
2244                 set_pte_at(mm, addr, pte, entry);
2245                 atomic_inc(&page[i]._mapcount);
2246                 pte_unmap(pte);
2247         }
2248 
2249         /*
2250          * Set PG_double_map before dropping compound_mapcount to avoid
2251          * false-negative page_mapped().
2252          */
2253         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2254                 for (i = 0; i < HPAGE_PMD_NR; i++)
2255                         atomic_inc(&page[i]._mapcount);
2256         }
2257 
2258         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2259                 /* Last compound_mapcount is gone. */
2260                 __dec_node_page_state(page, NR_ANON_THPS);
2261                 if (TestClearPageDoubleMap(page)) {
2262                         /* No need in mapcount reference anymore */
2263                         for (i = 0; i < HPAGE_PMD_NR; i++)
2264                                 atomic_dec(&page[i]._mapcount);
2265                 }
2266         }
2267 
2268         smp_wmb(); /* make pte visible before pmd */
2269         pmd_populate(mm, pmd, pgtable);
2270 
2271         if (freeze) {
2272                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2273                         page_remove_rmap(page + i, false);
2274                         put_page(page + i);
2275                 }
2276         }
2277 }
2278 
2279 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2280                 unsigned long address, bool freeze, struct page *page)
2281 {
2282         spinlock_t *ptl;
2283         struct mmu_notifier_range range;
2284 
2285         mmu_notifier_range_init(&range, vma->vm_mm, address & HPAGE_PMD_MASK,
2286                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2287         mmu_notifier_invalidate_range_start(&range);
2288         ptl = pmd_lock(vma->vm_mm, pmd);
2289 
2290         /*
2291          * If caller asks to setup a migration entries, we need a page to check
2292          * pmd against. Otherwise we can end up replacing wrong page.
2293          */
2294         VM_BUG_ON(freeze && !page);
2295         if (page && page != pmd_page(*pmd))
2296                 goto out;
2297 
2298         if (pmd_trans_huge(*pmd)) {
2299                 page = pmd_page(*pmd);
2300                 if (PageMlocked(page))
2301                         clear_page_mlock(page);
2302         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2303                 goto out;
2304         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2305 out:
2306         spin_unlock(ptl);
2307         /*
2308          * No need to double call mmu_notifier->invalidate_range() callback.
2309          * They are 3 cases to consider inside __split_huge_pmd_locked():
2310          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2311          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2312          *    fault will trigger a flush_notify before pointing to a new page
2313          *    (it is fine if the secondary mmu keeps pointing to the old zero
2314          *    page in the meantime)
2315          *  3) Split a huge pmd into pte pointing to the same page. No need
2316          *     to invalidate secondary tlb entry they are all still valid.
2317          *     any further changes to individual pte will notify. So no need
2318          *     to call mmu_notifier->invalidate_range()
2319          */
2320         mmu_notifier_invalidate_range_only_end(&range);
2321 }
2322 
2323 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2324                 bool freeze, struct page *page)
2325 {
2326         pgd_t *pgd;
2327         p4d_t *p4d;
2328         pud_t *pud;
2329         pmd_t *pmd;
2330 
2331         pgd = pgd_offset(vma->vm_mm, address);
2332         if (!pgd_present(*pgd))
2333                 return;
2334 
2335         p4d = p4d_offset(pgd, address);
2336         if (!p4d_present(*p4d))
2337                 return;
2338 
2339         pud = pud_offset(p4d, address);
2340         if (!pud_present(*pud))
2341                 return;
2342 
2343         pmd = pmd_offset(pud, address);
2344 
2345         __split_huge_pmd(vma, pmd, address, freeze, page);
2346 }
2347 
2348 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2349                              unsigned long start,
2350                              unsigned long end,
2351                              long adjust_next)
2352 {
2353         /*
2354          * If the new start address isn't hpage aligned and it could
2355          * previously contain an hugepage: check if we need to split
2356          * an huge pmd.
2357          */
2358         if (start & ~HPAGE_PMD_MASK &&
2359             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2360             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2361                 split_huge_pmd_address(vma, start, false, NULL);
2362 
2363         /*
2364          * If the new end address isn't hpage aligned and it could
2365          * previously contain an hugepage: check if we need to split
2366          * an huge pmd.
2367          */
2368         if (end & ~HPAGE_PMD_MASK &&
2369             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2370             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2371                 split_huge_pmd_address(vma, end, false, NULL);
2372 
2373         /*
2374          * If we're also updating the vma->vm_next->vm_start, if the new
2375          * vm_next->vm_start isn't page aligned and it could previously
2376          * contain an hugepage: check if we need to split an huge pmd.
2377          */
2378         if (adjust_next > 0) {
2379                 struct vm_area_struct *next = vma->vm_next;
2380                 unsigned long nstart = next->vm_start;
2381                 nstart += adjust_next << PAGE_SHIFT;
2382                 if (nstart & ~HPAGE_PMD_MASK &&
2383                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2384                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2385                         split_huge_pmd_address(next, nstart, false, NULL);
2386         }
2387 }
2388 
2389 static void unmap_page(struct page *page)
2390 {
2391         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2392                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2393         bool unmap_success;
2394 
2395         VM_BUG_ON_PAGE(!PageHead(page), page);
2396 
2397         if (PageAnon(page))
2398                 ttu_flags |= TTU_SPLIT_FREEZE;
2399 
2400         unmap_success = try_to_unmap(page, ttu_flags);
2401         VM_BUG_ON_PAGE(!unmap_success, page);
2402 }
2403 
2404 static void remap_page(struct page *page)
2405 {
2406         int i;
2407         if (PageTransHuge(page)) {
2408                 remove_migration_ptes(page, page, true);
2409         } else {
2410                 for (i = 0; i < HPAGE_PMD_NR; i++)
2411                         remove_migration_ptes(page + i, page + i, true);
2412         }
2413 }
2414 
2415 static void __split_huge_page_tail(struct page *head, int tail,
2416                 struct lruvec *lruvec, struct list_head *list)
2417 {
2418         struct page *page_tail = head + tail;
2419 
2420         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2421 
2422         /*
2423          * Clone page flags before unfreezing refcount.
2424          *
2425          * After successful get_page_unless_zero() might follow flags change,
2426          * for exmaple lock_page() which set PG_waiters.
2427          */
2428         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2429         page_tail->flags |= (head->flags &
2430                         ((1L << PG_referenced) |
2431                          (1L << PG_swapbacked) |
2432                          (1L << PG_swapcache) |
2433                          (1L << PG_mlocked) |
2434                          (1L << PG_uptodate) |
2435                          (1L << PG_active) |
2436                          (1L << PG_workingset) |
2437                          (1L << PG_locked) |
2438                          (1L << PG_unevictable) |
2439                          (1L << PG_dirty)));
2440 
2441         /* ->mapping in first tail page is compound_mapcount */
2442         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2443                         page_tail);
2444         page_tail->mapping = head->mapping;
2445         page_tail->index = head->index + tail;
2446 
2447         /* Page flags must be visible before we make the page non-compound. */
2448         smp_wmb();
2449 
2450         /*
2451          * Clear PageTail before unfreezing page refcount.
2452          *
2453          * After successful get_page_unless_zero() might follow put_page()
2454          * which needs correct compound_head().
2455          */
2456         clear_compound_head(page_tail);
2457 
2458         /* Finally unfreeze refcount. Additional reference from page cache. */
2459         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2460                                           PageSwapCache(head)));
2461 
2462         if (page_is_young(head))
2463                 set_page_young(page_tail);
2464         if (page_is_idle(head))
2465                 set_page_idle(page_tail);
2466 
2467         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2468 
2469         /*
2470          * always add to the tail because some iterators expect new
2471          * pages to show after the currently processed elements - e.g.
2472          * migrate_pages
2473          */
2474         lru_add_page_tail(head, page_tail, lruvec, list);
2475 }
2476 
2477 static void __split_huge_page(struct page *page, struct list_head *list,
2478                 pgoff_t end, unsigned long flags)
2479 {
2480         struct page *head = compound_head(page);
2481         pg_data_t *pgdat = page_pgdat(head);
2482         struct lruvec *lruvec;
2483         int i;
2484 
2485         lruvec = mem_cgroup_page_lruvec(head, pgdat);
2486 
2487         /* complete memcg works before add pages to LRU */
2488         mem_cgroup_split_huge_fixup(head);
2489 
2490         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2491                 __split_huge_page_tail(head, i, lruvec, list);
2492                 /* Some pages can be beyond i_size: drop them from page cache */
2493                 if (head[i].index >= end) {
2494                         ClearPageDirty(head + i);
2495                         __delete_from_page_cache(head + i, NULL);
2496                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2497                                 shmem_uncharge(head->mapping->host, 1);
2498                         put_page(head + i);
2499                 }
2500         }
2501 
2502         ClearPageCompound(head);
2503         /* See comment in __split_huge_page_tail() */
2504         if (PageAnon(head)) {
2505                 /* Additional pin to swap cache */
2506                 if (PageSwapCache(head))
2507                         page_ref_add(head, 2);
2508                 else
2509                         page_ref_inc(head);
2510         } else {
2511                 /* Additional pin to page cache */
2512                 page_ref_add(head, 2);
2513                 xa_unlock(&head->mapping->i_pages);
2514         }
2515 
2516         spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2517 
2518         remap_page(head);
2519 
2520         for (i = 0; i < HPAGE_PMD_NR; i++) {
2521                 struct page *subpage = head + i;
2522                 if (subpage == page)
2523                         continue;
2524                 unlock_page(subpage);
2525 
2526                 /*
2527                  * Subpages may be freed if there wasn't any mapping
2528                  * like if add_to_swap() is running on a lru page that
2529                  * had its mapping zapped. And freeing these pages
2530                  * requires taking the lru_lock so we do the put_page
2531                  * of the tail pages after the split is complete.
2532                  */
2533                 put_page(subpage);
2534         }
2535 }
2536 
2537 int total_mapcount(struct page *page)
2538 {
2539         int i, compound, ret;
2540 
2541         VM_BUG_ON_PAGE(PageTail(page), page);
2542 
2543         if (likely(!PageCompound(page)))
2544                 return atomic_read(&page->_mapcount) + 1;
2545 
2546         compound = compound_mapcount(page);
2547         if (PageHuge(page))
2548                 return compound;
2549         ret = compound;
2550         for (i = 0; i < HPAGE_PMD_NR; i++)
2551                 ret += atomic_read(&page[i]._mapcount) + 1;
2552         /* File pages has compound_mapcount included in _mapcount */
2553         if (!PageAnon(page))
2554                 return ret - compound * HPAGE_PMD_NR;
2555         if (PageDoubleMap(page))
2556                 ret -= HPAGE_PMD_NR;
2557         return ret;
2558 }
2559 
2560 /*
2561  * This calculates accurately how many mappings a transparent hugepage
2562  * has (unlike page_mapcount() which isn't fully accurate). This full
2563  * accuracy is primarily needed to know if copy-on-write faults can
2564  * reuse the page and change the mapping to read-write instead of
2565  * copying them. At the same time this returns the total_mapcount too.
2566  *
2567  * The function returns the highest mapcount any one of the subpages
2568  * has. If the return value is one, even if different processes are
2569  * mapping different subpages of the transparent hugepage, they can
2570  * all reuse it, because each process is reusing a different subpage.
2571  *
2572  * The total_mapcount is instead counting all virtual mappings of the
2573  * subpages. If the total_mapcount is equal to "one", it tells the
2574  * caller all mappings belong to the same "mm" and in turn the
2575  * anon_vma of the transparent hugepage can become the vma->anon_vma
2576  * local one as no other process may be mapping any of the subpages.
2577  *
2578  * It would be more accurate to replace page_mapcount() with
2579  * page_trans_huge_mapcount(), however we only use
2580  * page_trans_huge_mapcount() in the copy-on-write faults where we
2581  * need full accuracy to avoid breaking page pinning, because
2582  * page_trans_huge_mapcount() is slower than page_mapcount().
2583  */
2584 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2585 {
2586         int i, ret, _total_mapcount, mapcount;
2587 
2588         /* hugetlbfs shouldn't call it */
2589         VM_BUG_ON_PAGE(PageHuge(page), page);
2590 
2591         if (likely(!PageTransCompound(page))) {
2592                 mapcount = atomic_read(&page->_mapcount) + 1;
2593                 if (total_mapcount)
2594                         *total_mapcount = mapcount;
2595                 return mapcount;
2596         }
2597 
2598         page = compound_head(page);
2599 
2600         _total_mapcount = ret = 0;
2601         for (i = 0; i < HPAGE_PMD_NR; i++) {
2602                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2603                 ret = max(ret, mapcount);
2604                 _total_mapcount += mapcount;
2605         }
2606         if (PageDoubleMap(page)) {
2607                 ret -= 1;
2608                 _total_mapcount -= HPAGE_PMD_NR;
2609         }
2610         mapcount = compound_mapcount(page);
2611         ret += mapcount;
2612         _total_mapcount += mapcount;
2613         if (total_mapcount)
2614                 *total_mapcount = _total_mapcount;
2615         return ret;
2616 }
2617 
2618 /* Racy check whether the huge page can be split */
2619 bool can_split_huge_page(struct page *page, int *pextra_pins)
2620 {
2621         int extra_pins;
2622 
2623         /* Additional pins from page cache */
2624         if (PageAnon(page))
2625                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2626         else
2627                 extra_pins = HPAGE_PMD_NR;
2628         if (pextra_pins)
2629                 *pextra_pins = extra_pins;
2630         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2631 }
2632 
2633 /*
2634  * This function splits huge page into normal pages. @page can point to any
2635  * subpage of huge page to split. Split doesn't change the position of @page.
2636  *
2637  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2638  * The huge page must be locked.
2639  *
2640  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2641  *
2642  * Both head page and tail pages will inherit mapping, flags, and so on from
2643  * the hugepage.
2644  *
2645  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2646  * they are not mapped.
2647  *
2648  * Returns 0 if the hugepage is split successfully.
2649  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2650  * us.
2651  */
2652 int split_huge_page_to_list(struct page *page, struct list_head *list)
2653 {
2654         struct page *head = compound_head(page);
2655         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2656         struct anon_vma *anon_vma = NULL;
2657         struct address_space *mapping = NULL;
2658         int count, mapcount, extra_pins, ret;
2659         bool mlocked;
2660         unsigned long flags;
2661         pgoff_t end;
2662 
2663         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2664         VM_BUG_ON_PAGE(!PageLocked(page), page);
2665         VM_BUG_ON_PAGE(!PageCompound(page), page);
2666 
2667         if (PageWriteback(page))
2668                 return -EBUSY;
2669 
2670         if (PageAnon(head)) {
2671                 /*
2672                  * The caller does not necessarily hold an mmap_sem that would
2673                  * prevent the anon_vma disappearing so we first we take a
2674                  * reference to it and then lock the anon_vma for write. This
2675                  * is similar to page_lock_anon_vma_read except the write lock
2676                  * is taken to serialise against parallel split or collapse
2677                  * operations.
2678                  */
2679                 anon_vma = page_get_anon_vma(head);
2680                 if (!anon_vma) {
2681                         ret = -EBUSY;
2682                         goto out;
2683                 }
2684                 end = -1;
2685                 mapping = NULL;
2686                 anon_vma_lock_write(anon_vma);
2687         } else {
2688                 mapping = head->mapping;
2689 
2690                 /* Truncated ? */
2691                 if (!mapping) {
2692                         ret = -EBUSY;
2693                         goto out;
2694                 }
2695 
2696                 anon_vma = NULL;
2697                 i_mmap_lock_read(mapping);
2698 
2699                 /*
2700                  *__split_huge_page() may need to trim off pages beyond EOF:
2701                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2702                  * which cannot be nested inside the page tree lock. So note
2703                  * end now: i_size itself may be changed at any moment, but
2704                  * head page lock is good enough to serialize the trimming.
2705                  */
2706                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2707         }
2708 
2709         /*
2710          * Racy check if we can split the page, before unmap_page() will
2711          * split PMDs
2712          */
2713         if (!can_split_huge_page(head, &extra_pins)) {
2714                 ret = -EBUSY;
2715                 goto out_unlock;
2716         }
2717 
2718         mlocked = PageMlocked(page);
2719         unmap_page(head);
2720         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2721 
2722         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2723         if (mlocked)
2724                 lru_add_drain();
2725 
2726         /* prevent PageLRU to go away from under us, and freeze lru stats */
2727         spin_lock_irqsave(&pgdata->lru_lock, flags);
2728 
2729         if (mapping) {
2730                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2731 
2732                 /*
2733                  * Check if the head page is present in page cache.
2734                  * We assume all tail are present too, if head is there.
2735                  */
2736                 xa_lock(&mapping->i_pages);
2737                 if (xas_load(&xas) != head)
2738                         goto fail;
2739         }
2740 
2741         /* Prevent deferred_split_scan() touching ->_refcount */
2742         spin_lock(&pgdata->split_queue_lock);
2743         count = page_count(head);
2744         mapcount = total_mapcount(head);
2745         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2746                 if (!list_empty(page_deferred_list(head))) {
2747                         pgdata->split_queue_len--;
2748                         list_del(page_deferred_list(head));
2749                 }
2750                 if (mapping)
2751                         __dec_node_page_state(page, NR_SHMEM_THPS);
2752                 spin_unlock(&pgdata->split_queue_lock);
2753                 __split_huge_page(page, list, end, flags);
2754                 if (PageSwapCache(head)) {
2755                         swp_entry_t entry = { .val = page_private(head) };
2756 
2757                         ret = split_swap_cluster(entry);
2758                 } else
2759                         ret = 0;
2760         } else {
2761                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2762                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2763                                         mapcount, count);
2764                         if (PageTail(page))
2765                                 dump_page(head, NULL);
2766                         dump_page(page, "total_mapcount(head) > 0");
2767                         BUG();
2768                 }
2769                 spin_unlock(&pgdata->split_queue_lock);
2770 fail:           if (mapping)
2771                         xa_unlock(&mapping->i_pages);
2772                 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2773                 remap_page(head);
2774                 ret = -EBUSY;
2775         }
2776 
2777 out_unlock:
2778         if (anon_vma) {
2779                 anon_vma_unlock_write(anon_vma);
2780                 put_anon_vma(anon_vma);
2781         }
2782         if (mapping)
2783                 i_mmap_unlock_read(mapping);
2784 out:
2785         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2786         return ret;
2787 }
2788 
2789 void free_transhuge_page(struct page *page)
2790 {
2791         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2792         unsigned long flags;
2793 
2794         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2795         if (!list_empty(page_deferred_list(page))) {
2796                 pgdata->split_queue_len--;
2797                 list_del(page_deferred_list(page));
2798         }
2799         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2800         free_compound_page(page);
2801 }
2802 
2803 void deferred_split_huge_page(struct page *page)
2804 {
2805         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2806         unsigned long flags;
2807 
2808         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2809 
2810         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2811         if (list_empty(page_deferred_list(page))) {
2812                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2813                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2814                 pgdata->split_queue_len++;
2815         }
2816         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2817 }
2818 
2819 static unsigned long deferred_split_count(struct shrinker *shrink,
2820                 struct shrink_control *sc)
2821 {
2822         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2823         return READ_ONCE(pgdata->split_queue_len);
2824 }
2825 
2826 static unsigned long deferred_split_scan(struct shrinker *shrink,
2827                 struct shrink_control *sc)
2828 {
2829         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2830         unsigned long flags;
2831         LIST_HEAD(list), *pos, *next;
2832         struct page *page;
2833         int split = 0;
2834 
2835         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2836         /* Take pin on all head pages to avoid freeing them under us */
2837         list_for_each_safe(pos, next, &pgdata->split_queue) {
2838                 page = list_entry((void *)pos, struct page, mapping);
2839                 page = compound_head(page);
2840                 if (get_page_unless_zero(page)) {
2841                         list_move(page_deferred_list(page), &list);
2842                 } else {
2843                         /* We lost race with put_compound_page() */
2844                         list_del_init(page_deferred_list(page));
2845                         pgdata->split_queue_len--;
2846                 }
2847                 if (!--sc->nr_to_scan)
2848                         break;
2849         }
2850         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2851 
2852         list_for_each_safe(pos, next, &list) {
2853                 page = list_entry((void *)pos, struct page, mapping);
2854                 if (!trylock_page(page))
2855                         goto next;
2856                 /* split_huge_page() removes page from list on success */
2857                 if (!split_huge_page(page))
2858                         split++;
2859                 unlock_page(page);
2860 next:
2861                 put_page(page);
2862         }
2863 
2864         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2865         list_splice_tail(&list, &pgdata->split_queue);
2866         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2867 
2868         /*
2869          * Stop shrinker if we didn't split any page, but the queue is empty.
2870          * This can happen if pages were freed under us.
2871          */
2872         if (!split && list_empty(&pgdata->split_queue))
2873                 return SHRINK_STOP;
2874         return split;
2875 }
2876 
2877 static struct shrinker deferred_split_shrinker = {
2878         .count_objects = deferred_split_count,
2879         .scan_objects = deferred_split_scan,
2880         .seeks = DEFAULT_SEEKS,
2881         .flags = SHRINKER_NUMA_AWARE,
2882 };
2883 
2884 #ifdef CONFIG_DEBUG_FS
2885 static int split_huge_pages_set(void *data, u64 val)
2886 {
2887         struct zone *zone;
2888         struct page *page;
2889         unsigned long pfn, max_zone_pfn;
2890         unsigned long total = 0, split = 0;
2891 
2892         if (val != 1)
2893                 return -EINVAL;
2894 
2895         for_each_populated_zone(zone) {
2896                 max_zone_pfn = zone_end_pfn(zone);
2897                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2898                         if (!pfn_valid(pfn))
2899                                 continue;
2900 
2901                         page = pfn_to_page(pfn);
2902                         if (!get_page_unless_zero(page))
2903                                 continue;
2904 
2905                         if (zone != page_zone(page))
2906                                 goto next;
2907 
2908                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2909                                 goto next;
2910 
2911                         total++;
2912                         lock_page(page);
2913                         if (!split_huge_page(page))
2914                                 split++;
2915                         unlock_page(page);
2916 next:
2917                         put_page(page);
2918                 }
2919         }
2920 
2921         pr_info("%lu of %lu THP split\n", split, total);
2922 
2923         return 0;
2924 }
2925 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2926                 "%llu\n");
2927 
2928 static int __init split_huge_pages_debugfs(void)
2929 {
2930         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2931                             &split_huge_pages_fops);
2932         return 0;
2933 }
2934 late_initcall(split_huge_pages_debugfs);
2935 #endif
2936 
2937 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2938 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2939                 struct page *page)
2940 {
2941         struct vm_area_struct *vma = pvmw->vma;
2942         struct mm_struct *mm = vma->vm_mm;
2943         unsigned long address = pvmw->address;
2944         pmd_t pmdval;
2945         swp_entry_t entry;
2946         pmd_t pmdswp;
2947 
2948         if (!(pvmw->pmd && !pvmw->pte))
2949                 return;
2950 
2951         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2952         pmdval = *pvmw->pmd;
2953         pmdp_invalidate(vma, address, pvmw->pmd);
2954         if (pmd_dirty(pmdval))
2955                 set_page_dirty(page);
2956         entry = make_migration_entry(page, pmd_write(pmdval));
2957         pmdswp = swp_entry_to_pmd(entry);
2958         if (pmd_soft_dirty(pmdval))
2959                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2960         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2961         page_remove_rmap(page, true);
2962         put_page(page);
2963 }
2964 
2965 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2966 {
2967         struct vm_area_struct *vma = pvmw->vma;
2968         struct mm_struct *mm = vma->vm_mm;
2969         unsigned long address = pvmw->address;
2970         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2971         pmd_t pmde;
2972         swp_entry_t entry;
2973 
2974         if (!(pvmw->pmd && !pvmw->pte))
2975                 return;
2976 
2977         entry = pmd_to_swp_entry(*pvmw->pmd);
2978         get_page(new);
2979         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2980         if (pmd_swp_soft_dirty(*pvmw->pmd))
2981                 pmde = pmd_mksoft_dirty(pmde);
2982         if (is_write_migration_entry(entry))
2983                 pmde = maybe_pmd_mkwrite(pmde, vma);
2984 
2985         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2986         if (PageAnon(new))
2987                 page_add_anon_rmap(new, vma, mmun_start, true);
2988         else
2989                 page_add_file_rmap(new, true);
2990         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2991         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2992                 mlock_vma_page(new);
2993         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2994 }
2995 #endif
2996 

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