8ea1b36bd452d795da8ac2714634c6bc70a45b99
[muen/linux.git] / mm / huge_memory.c
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
37 #include <asm/tlb.h>
38 #include <asm/pgalloc.h>
39 #include "internal.h"
40
41 /*
42  * By default, transparent hugepage support is disabled in order to avoid
43  * risking an increased memory footprint for applications that are not
44  * guaranteed to benefit from it. When transparent hugepage support is
45  * enabled, it is for all mappings, and khugepaged scans all mappings.
46  * Defrag is invoked by khugepaged hugepage allocations and by page faults
47  * for all hugepage allocations.
48  */
49 unsigned long transparent_hugepage_flags __read_mostly =
50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
51         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
52 #endif
53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
54         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
55 #endif
56         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
57         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
58         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
59
60 static struct shrinker deferred_split_shrinker;
61
62 static atomic_t huge_zero_refcount;
63 struct page *huge_zero_page __read_mostly;
64
65 static struct page *get_huge_zero_page(void)
66 {
67         struct page *zero_page;
68 retry:
69         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
70                 return READ_ONCE(huge_zero_page);
71
72         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
73                         HPAGE_PMD_ORDER);
74         if (!zero_page) {
75                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
76                 return NULL;
77         }
78         count_vm_event(THP_ZERO_PAGE_ALLOC);
79         preempt_disable();
80         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
81                 preempt_enable();
82                 __free_pages(zero_page, compound_order(zero_page));
83                 goto retry;
84         }
85
86         /* We take additional reference here. It will be put back by shrinker */
87         atomic_set(&huge_zero_refcount, 2);
88         preempt_enable();
89         return READ_ONCE(huge_zero_page);
90 }
91
92 static void put_huge_zero_page(void)
93 {
94         /*
95          * Counter should never go to zero here. Only shrinker can put
96          * last reference.
97          */
98         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
99 }
100
101 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
102 {
103         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
104                 return READ_ONCE(huge_zero_page);
105
106         if (!get_huge_zero_page())
107                 return NULL;
108
109         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
110                 put_huge_zero_page();
111
112         return READ_ONCE(huge_zero_page);
113 }
114
115 void mm_put_huge_zero_page(struct mm_struct *mm)
116 {
117         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
118                 put_huge_zero_page();
119 }
120
121 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
122                                         struct shrink_control *sc)
123 {
124         /* we can free zero page only if last reference remains */
125         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
126 }
127
128 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
129                                        struct shrink_control *sc)
130 {
131         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
132                 struct page *zero_page = xchg(&huge_zero_page, NULL);
133                 BUG_ON(zero_page == NULL);
134                 __free_pages(zero_page, compound_order(zero_page));
135                 return HPAGE_PMD_NR;
136         }
137
138         return 0;
139 }
140
141 static struct shrinker huge_zero_page_shrinker = {
142         .count_objects = shrink_huge_zero_page_count,
143         .scan_objects = shrink_huge_zero_page_scan,
144         .seeks = DEFAULT_SEEKS,
145 };
146
147 #ifdef CONFIG_SYSFS
148 static ssize_t enabled_show(struct kobject *kobj,
149                             struct kobj_attribute *attr, char *buf)
150 {
151         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
152                 return sprintf(buf, "[always] madvise never\n");
153         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
154                 return sprintf(buf, "always [madvise] never\n");
155         else
156                 return sprintf(buf, "always madvise [never]\n");
157 }
158
159 static ssize_t enabled_store(struct kobject *kobj,
160                              struct kobj_attribute *attr,
161                              const char *buf, size_t count)
162 {
163         ssize_t ret = count;
164
165         if (!memcmp("always", buf,
166                     min(sizeof("always")-1, count))) {
167                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
168                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
169         } else if (!memcmp("madvise", buf,
170                            min(sizeof("madvise")-1, count))) {
171                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
172                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
173         } else if (!memcmp("never", buf,
174                            min(sizeof("never")-1, count))) {
175                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
176                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
177         } else
178                 ret = -EINVAL;
179
180         if (ret > 0) {
181                 int err = start_stop_khugepaged();
182                 if (err)
183                         ret = err;
184         }
185         return ret;
186 }
187 static struct kobj_attribute enabled_attr =
188         __ATTR(enabled, 0644, enabled_show, enabled_store);
189
190 ssize_t single_hugepage_flag_show(struct kobject *kobj,
191                                 struct kobj_attribute *attr, char *buf,
192                                 enum transparent_hugepage_flag flag)
193 {
194         return sprintf(buf, "%d\n",
195                        !!test_bit(flag, &transparent_hugepage_flags));
196 }
197
198 ssize_t single_hugepage_flag_store(struct kobject *kobj,
199                                  struct kobj_attribute *attr,
200                                  const char *buf, size_t count,
201                                  enum transparent_hugepage_flag flag)
202 {
203         unsigned long value;
204         int ret;
205
206         ret = kstrtoul(buf, 10, &value);
207         if (ret < 0)
208                 return ret;
209         if (value > 1)
210                 return -EINVAL;
211
212         if (value)
213                 set_bit(flag, &transparent_hugepage_flags);
214         else
215                 clear_bit(flag, &transparent_hugepage_flags);
216
217         return count;
218 }
219
220 static ssize_t defrag_show(struct kobject *kobj,
221                            struct kobj_attribute *attr, char *buf)
222 {
223         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
224                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
225         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
226                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
227         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
228                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
229         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
230                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
231         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
232 }
233
234 static ssize_t defrag_store(struct kobject *kobj,
235                             struct kobj_attribute *attr,
236                             const char *buf, size_t count)
237 {
238         if (!memcmp("always", buf,
239                     min(sizeof("always")-1, count))) {
240                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
241                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
242                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
243                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
244         } else if (!memcmp("defer+madvise", buf,
245                     min(sizeof("defer+madvise")-1, count))) {
246                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
247                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
248                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
249                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
250         } else if (!memcmp("defer", buf,
251                     min(sizeof("defer")-1, count))) {
252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
253                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
254                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
255                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
256         } else if (!memcmp("madvise", buf,
257                            min(sizeof("madvise")-1, count))) {
258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
259                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
260                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
261                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
262         } else if (!memcmp("never", buf,
263                            min(sizeof("never")-1, count))) {
264                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
265                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
266                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
268         } else
269                 return -EINVAL;
270
271         return count;
272 }
273 static struct kobj_attribute defrag_attr =
274         __ATTR(defrag, 0644, defrag_show, defrag_store);
275
276 static ssize_t use_zero_page_show(struct kobject *kobj,
277                 struct kobj_attribute *attr, char *buf)
278 {
279         return single_hugepage_flag_show(kobj, attr, buf,
280                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
281 }
282 static ssize_t use_zero_page_store(struct kobject *kobj,
283                 struct kobj_attribute *attr, const char *buf, size_t count)
284 {
285         return single_hugepage_flag_store(kobj, attr, buf, count,
286                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
287 }
288 static struct kobj_attribute use_zero_page_attr =
289         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
290
291 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
292                 struct kobj_attribute *attr, char *buf)
293 {
294         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
295 }
296 static struct kobj_attribute hpage_pmd_size_attr =
297         __ATTR_RO(hpage_pmd_size);
298
299 #ifdef CONFIG_DEBUG_VM
300 static ssize_t debug_cow_show(struct kobject *kobj,
301                                 struct kobj_attribute *attr, char *buf)
302 {
303         return single_hugepage_flag_show(kobj, attr, buf,
304                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
305 }
306 static ssize_t debug_cow_store(struct kobject *kobj,
307                                struct kobj_attribute *attr,
308                                const char *buf, size_t count)
309 {
310         return single_hugepage_flag_store(kobj, attr, buf, count,
311                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
312 }
313 static struct kobj_attribute debug_cow_attr =
314         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
315 #endif /* CONFIG_DEBUG_VM */
316
317 static struct attribute *hugepage_attr[] = {
318         &enabled_attr.attr,
319         &defrag_attr.attr,
320         &use_zero_page_attr.attr,
321         &hpage_pmd_size_attr.attr,
322 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
323         &shmem_enabled_attr.attr,
324 #endif
325 #ifdef CONFIG_DEBUG_VM
326         &debug_cow_attr.attr,
327 #endif
328         NULL,
329 };
330
331 static const struct attribute_group hugepage_attr_group = {
332         .attrs = hugepage_attr,
333 };
334
335 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
336 {
337         int err;
338
339         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
340         if (unlikely(!*hugepage_kobj)) {
341                 pr_err("failed to create transparent hugepage kobject\n");
342                 return -ENOMEM;
343         }
344
345         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
346         if (err) {
347                 pr_err("failed to register transparent hugepage group\n");
348                 goto delete_obj;
349         }
350
351         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
352         if (err) {
353                 pr_err("failed to register transparent hugepage group\n");
354                 goto remove_hp_group;
355         }
356
357         return 0;
358
359 remove_hp_group:
360         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
361 delete_obj:
362         kobject_put(*hugepage_kobj);
363         return err;
364 }
365
366 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
367 {
368         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
369         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
370         kobject_put(hugepage_kobj);
371 }
372 #else
373 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
374 {
375         return 0;
376 }
377
378 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
379 {
380 }
381 #endif /* CONFIG_SYSFS */
382
383 static int __init hugepage_init(void)
384 {
385         int err;
386         struct kobject *hugepage_kobj;
387
388         if (!has_transparent_hugepage()) {
389                 transparent_hugepage_flags = 0;
390                 return -EINVAL;
391         }
392
393         /*
394          * hugepages can't be allocated by the buddy allocator
395          */
396         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
397         /*
398          * we use page->mapping and page->index in second tail page
399          * as list_head: assuming THP order >= 2
400          */
401         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
402
403         err = hugepage_init_sysfs(&hugepage_kobj);
404         if (err)
405                 goto err_sysfs;
406
407         err = khugepaged_init();
408         if (err)
409                 goto err_slab;
410
411         err = register_shrinker(&huge_zero_page_shrinker);
412         if (err)
413                 goto err_hzp_shrinker;
414         err = register_shrinker(&deferred_split_shrinker);
415         if (err)
416                 goto err_split_shrinker;
417
418         /*
419          * By default disable transparent hugepages on smaller systems,
420          * where the extra memory used could hurt more than TLB overhead
421          * is likely to save.  The admin can still enable it through /sys.
422          */
423         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
424                 transparent_hugepage_flags = 0;
425                 return 0;
426         }
427
428         err = start_stop_khugepaged();
429         if (err)
430                 goto err_khugepaged;
431
432         return 0;
433 err_khugepaged:
434         unregister_shrinker(&deferred_split_shrinker);
435 err_split_shrinker:
436         unregister_shrinker(&huge_zero_page_shrinker);
437 err_hzp_shrinker:
438         khugepaged_destroy();
439 err_slab:
440         hugepage_exit_sysfs(hugepage_kobj);
441 err_sysfs:
442         return err;
443 }
444 subsys_initcall(hugepage_init);
445
446 static int __init setup_transparent_hugepage(char *str)
447 {
448         int ret = 0;
449         if (!str)
450                 goto out;
451         if (!strcmp(str, "always")) {
452                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
453                         &transparent_hugepage_flags);
454                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
455                           &transparent_hugepage_flags);
456                 ret = 1;
457         } else if (!strcmp(str, "madvise")) {
458                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
459                           &transparent_hugepage_flags);
460                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
461                         &transparent_hugepage_flags);
462                 ret = 1;
463         } else if (!strcmp(str, "never")) {
464                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
465                           &transparent_hugepage_flags);
466                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
467                           &transparent_hugepage_flags);
468                 ret = 1;
469         }
470 out:
471         if (!ret)
472                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
473         return ret;
474 }
475 __setup("transparent_hugepage=", setup_transparent_hugepage);
476
477 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
478 {
479         if (likely(vma->vm_flags & VM_WRITE))
480                 pmd = pmd_mkwrite(pmd);
481         return pmd;
482 }
483
484 static inline struct list_head *page_deferred_list(struct page *page)
485 {
486         /* ->lru in the tail pages is occupied by compound_head. */
487         return &page[2].deferred_list;
488 }
489
490 void prep_transhuge_page(struct page *page)
491 {
492         /*
493          * we use page->mapping and page->indexlru in second tail page
494          * as list_head: assuming THP order >= 2
495          */
496
497         INIT_LIST_HEAD(page_deferred_list(page));
498         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
499 }
500
501 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
502                 loff_t off, unsigned long flags, unsigned long size)
503 {
504         unsigned long addr;
505         loff_t off_end = off + len;
506         loff_t off_align = round_up(off, size);
507         unsigned long len_pad;
508
509         if (off_end <= off_align || (off_end - off_align) < size)
510                 return 0;
511
512         len_pad = len + size;
513         if (len_pad < len || (off + len_pad) < off)
514                 return 0;
515
516         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
517                                               off >> PAGE_SHIFT, flags);
518         if (IS_ERR_VALUE(addr))
519                 return 0;
520
521         addr += (off - addr) & (size - 1);
522         return addr;
523 }
524
525 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
526                 unsigned long len, unsigned long pgoff, unsigned long flags)
527 {
528         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
529
530         if (addr)
531                 goto out;
532         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
533                 goto out;
534
535         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
536         if (addr)
537                 return addr;
538
539  out:
540         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
541 }
542 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
543
544 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
545                         struct page *page, gfp_t gfp)
546 {
547         struct vm_area_struct *vma = vmf->vma;
548         struct mem_cgroup *memcg;
549         pgtable_t pgtable;
550         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
551         vm_fault_t ret = 0;
552
553         VM_BUG_ON_PAGE(!PageCompound(page), page);
554
555         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
556                 put_page(page);
557                 count_vm_event(THP_FAULT_FALLBACK);
558                 return VM_FAULT_FALLBACK;
559         }
560
561         pgtable = pte_alloc_one(vma->vm_mm, haddr);
562         if (unlikely(!pgtable)) {
563                 ret = VM_FAULT_OOM;
564                 goto release;
565         }
566
567         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
568         /*
569          * The memory barrier inside __SetPageUptodate makes sure that
570          * clear_huge_page writes become visible before the set_pmd_at()
571          * write.
572          */
573         __SetPageUptodate(page);
574
575         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
576         if (unlikely(!pmd_none(*vmf->pmd))) {
577                 goto unlock_release;
578         } else {
579                 pmd_t entry;
580
581                 ret = check_stable_address_space(vma->vm_mm);
582                 if (ret)
583                         goto unlock_release;
584
585                 /* Deliver the page fault to userland */
586                 if (userfaultfd_missing(vma)) {
587                         vm_fault_t ret2;
588
589                         spin_unlock(vmf->ptl);
590                         mem_cgroup_cancel_charge(page, memcg, true);
591                         put_page(page);
592                         pte_free(vma->vm_mm, pgtable);
593                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
594                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
595                         return ret2;
596                 }
597
598                 entry = mk_huge_pmd(page, vma->vm_page_prot);
599                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
600                 page_add_new_anon_rmap(page, vma, haddr, true);
601                 mem_cgroup_commit_charge(page, memcg, false, true);
602                 lru_cache_add_active_or_unevictable(page, vma);
603                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
604                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
605                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
606                 mm_inc_nr_ptes(vma->vm_mm);
607                 spin_unlock(vmf->ptl);
608                 count_vm_event(THP_FAULT_ALLOC);
609         }
610
611         return 0;
612 unlock_release:
613         spin_unlock(vmf->ptl);
614 release:
615         if (pgtable)
616                 pte_free(vma->vm_mm, pgtable);
617         mem_cgroup_cancel_charge(page, memcg, true);
618         put_page(page);
619         return ret;
620
621 }
622
623 /*
624  * always: directly stall for all thp allocations
625  * defer: wake kswapd and fail if not immediately available
626  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
627  *                fail if not immediately available
628  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
629  *          available
630  * never: never stall for any thp allocation
631  */
632 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
633 {
634         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
635
636         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
637                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
638         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
639                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
640         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
641                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
642                                                              __GFP_KSWAPD_RECLAIM);
643         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
644                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
645                                                              0);
646         return GFP_TRANSHUGE_LIGHT;
647 }
648
649 /* Caller must hold page table lock. */
650 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
651                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
652                 struct page *zero_page)
653 {
654         pmd_t entry;
655         if (!pmd_none(*pmd))
656                 return false;
657         entry = mk_pmd(zero_page, vma->vm_page_prot);
658         entry = pmd_mkhuge(entry);
659         if (pgtable)
660                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
661         set_pmd_at(mm, haddr, pmd, entry);
662         mm_inc_nr_ptes(mm);
663         return true;
664 }
665
666 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
667 {
668         struct vm_area_struct *vma = vmf->vma;
669         gfp_t gfp;
670         struct page *page;
671         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
672
673         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
674                 return VM_FAULT_FALLBACK;
675         if (unlikely(anon_vma_prepare(vma)))
676                 return VM_FAULT_OOM;
677         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
678                 return VM_FAULT_OOM;
679         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
680                         !mm_forbids_zeropage(vma->vm_mm) &&
681                         transparent_hugepage_use_zero_page()) {
682                 pgtable_t pgtable;
683                 struct page *zero_page;
684                 bool set;
685                 vm_fault_t ret;
686                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
687                 if (unlikely(!pgtable))
688                         return VM_FAULT_OOM;
689                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
690                 if (unlikely(!zero_page)) {
691                         pte_free(vma->vm_mm, pgtable);
692                         count_vm_event(THP_FAULT_FALLBACK);
693                         return VM_FAULT_FALLBACK;
694                 }
695                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
696                 ret = 0;
697                 set = false;
698                 if (pmd_none(*vmf->pmd)) {
699                         ret = check_stable_address_space(vma->vm_mm);
700                         if (ret) {
701                                 spin_unlock(vmf->ptl);
702                         } else if (userfaultfd_missing(vma)) {
703                                 spin_unlock(vmf->ptl);
704                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
705                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
706                         } else {
707                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
708                                                    haddr, vmf->pmd, zero_page);
709                                 spin_unlock(vmf->ptl);
710                                 set = true;
711                         }
712                 } else
713                         spin_unlock(vmf->ptl);
714                 if (!set)
715                         pte_free(vma->vm_mm, pgtable);
716                 return ret;
717         }
718         gfp = alloc_hugepage_direct_gfpmask(vma);
719         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
720         if (unlikely(!page)) {
721                 count_vm_event(THP_FAULT_FALLBACK);
722                 return VM_FAULT_FALLBACK;
723         }
724         prep_transhuge_page(page);
725         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
726 }
727
728 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
729                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
730                 pgtable_t pgtable)
731 {
732         struct mm_struct *mm = vma->vm_mm;
733         pmd_t entry;
734         spinlock_t *ptl;
735
736         ptl = pmd_lock(mm, pmd);
737         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
738         if (pfn_t_devmap(pfn))
739                 entry = pmd_mkdevmap(entry);
740         if (write) {
741                 entry = pmd_mkyoung(pmd_mkdirty(entry));
742                 entry = maybe_pmd_mkwrite(entry, vma);
743         }
744
745         if (pgtable) {
746                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
747                 mm_inc_nr_ptes(mm);
748         }
749
750         set_pmd_at(mm, addr, pmd, entry);
751         update_mmu_cache_pmd(vma, addr, pmd);
752         spin_unlock(ptl);
753 }
754
755 vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
756                         pmd_t *pmd, pfn_t pfn, bool write)
757 {
758         pgprot_t pgprot = vma->vm_page_prot;
759         pgtable_t pgtable = NULL;
760         /*
761          * If we had pmd_special, we could avoid all these restrictions,
762          * but we need to be consistent with PTEs and architectures that
763          * can't support a 'special' bit.
764          */
765         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
766                         !pfn_t_devmap(pfn));
767         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
768                                                 (VM_PFNMAP|VM_MIXEDMAP));
769         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
770
771         if (addr < vma->vm_start || addr >= vma->vm_end)
772                 return VM_FAULT_SIGBUS;
773
774         if (arch_needs_pgtable_deposit()) {
775                 pgtable = pte_alloc_one(vma->vm_mm, addr);
776                 if (!pgtable)
777                         return VM_FAULT_OOM;
778         }
779
780         track_pfn_insert(vma, &pgprot, pfn);
781
782         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
783         return VM_FAULT_NOPAGE;
784 }
785 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
786
787 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
788 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
789 {
790         if (likely(vma->vm_flags & VM_WRITE))
791                 pud = pud_mkwrite(pud);
792         return pud;
793 }
794
795 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
796                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
797 {
798         struct mm_struct *mm = vma->vm_mm;
799         pud_t entry;
800         spinlock_t *ptl;
801
802         ptl = pud_lock(mm, pud);
803         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
804         if (pfn_t_devmap(pfn))
805                 entry = pud_mkdevmap(entry);
806         if (write) {
807                 entry = pud_mkyoung(pud_mkdirty(entry));
808                 entry = maybe_pud_mkwrite(entry, vma);
809         }
810         set_pud_at(mm, addr, pud, entry);
811         update_mmu_cache_pud(vma, addr, pud);
812         spin_unlock(ptl);
813 }
814
815 vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
816                         pud_t *pud, pfn_t pfn, bool write)
817 {
818         pgprot_t pgprot = vma->vm_page_prot;
819         /*
820          * If we had pud_special, we could avoid all these restrictions,
821          * but we need to be consistent with PTEs and architectures that
822          * can't support a 'special' bit.
823          */
824         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
825                         !pfn_t_devmap(pfn));
826         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
827                                                 (VM_PFNMAP|VM_MIXEDMAP));
828         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
829
830         if (addr < vma->vm_start || addr >= vma->vm_end)
831                 return VM_FAULT_SIGBUS;
832
833         track_pfn_insert(vma, &pgprot, pfn);
834
835         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
836         return VM_FAULT_NOPAGE;
837 }
838 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
839 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
840
841 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
842                 pmd_t *pmd, int flags)
843 {
844         pmd_t _pmd;
845
846         _pmd = pmd_mkyoung(*pmd);
847         if (flags & FOLL_WRITE)
848                 _pmd = pmd_mkdirty(_pmd);
849         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
850                                 pmd, _pmd, flags & FOLL_WRITE))
851                 update_mmu_cache_pmd(vma, addr, pmd);
852 }
853
854 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
855                 pmd_t *pmd, int flags)
856 {
857         unsigned long pfn = pmd_pfn(*pmd);
858         struct mm_struct *mm = vma->vm_mm;
859         struct dev_pagemap *pgmap;
860         struct page *page;
861
862         assert_spin_locked(pmd_lockptr(mm, pmd));
863
864         /*
865          * When we COW a devmap PMD entry, we split it into PTEs, so we should
866          * not be in this function with `flags & FOLL_COW` set.
867          */
868         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
869
870         if (flags & FOLL_WRITE && !pmd_write(*pmd))
871                 return NULL;
872
873         if (pmd_present(*pmd) && pmd_devmap(*pmd))
874                 /* pass */;
875         else
876                 return NULL;
877
878         if (flags & FOLL_TOUCH)
879                 touch_pmd(vma, addr, pmd, flags);
880
881         /*
882          * device mapped pages can only be returned if the
883          * caller will manage the page reference count.
884          */
885         if (!(flags & FOLL_GET))
886                 return ERR_PTR(-EEXIST);
887
888         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
889         pgmap = get_dev_pagemap(pfn, NULL);
890         if (!pgmap)
891                 return ERR_PTR(-EFAULT);
892         page = pfn_to_page(pfn);
893         get_page(page);
894         put_dev_pagemap(pgmap);
895
896         return page;
897 }
898
899 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
900                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
901                   struct vm_area_struct *vma)
902 {
903         spinlock_t *dst_ptl, *src_ptl;
904         struct page *src_page;
905         pmd_t pmd;
906         pgtable_t pgtable = NULL;
907         int ret = -ENOMEM;
908
909         /* Skip if can be re-fill on fault */
910         if (!vma_is_anonymous(vma))
911                 return 0;
912
913         pgtable = pte_alloc_one(dst_mm, addr);
914         if (unlikely(!pgtable))
915                 goto out;
916
917         dst_ptl = pmd_lock(dst_mm, dst_pmd);
918         src_ptl = pmd_lockptr(src_mm, src_pmd);
919         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
920
921         ret = -EAGAIN;
922         pmd = *src_pmd;
923
924 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
925         if (unlikely(is_swap_pmd(pmd))) {
926                 swp_entry_t entry = pmd_to_swp_entry(pmd);
927
928                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
929                 if (is_write_migration_entry(entry)) {
930                         make_migration_entry_read(&entry);
931                         pmd = swp_entry_to_pmd(entry);
932                         if (pmd_swp_soft_dirty(*src_pmd))
933                                 pmd = pmd_swp_mksoft_dirty(pmd);
934                         set_pmd_at(src_mm, addr, src_pmd, pmd);
935                 }
936                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
937                 mm_inc_nr_ptes(dst_mm);
938                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
939                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
940                 ret = 0;
941                 goto out_unlock;
942         }
943 #endif
944
945         if (unlikely(!pmd_trans_huge(pmd))) {
946                 pte_free(dst_mm, pgtable);
947                 goto out_unlock;
948         }
949         /*
950          * When page table lock is held, the huge zero pmd should not be
951          * under splitting since we don't split the page itself, only pmd to
952          * a page table.
953          */
954         if (is_huge_zero_pmd(pmd)) {
955                 struct page *zero_page;
956                 /*
957                  * get_huge_zero_page() will never allocate a new page here,
958                  * since we already have a zero page to copy. It just takes a
959                  * reference.
960                  */
961                 zero_page = mm_get_huge_zero_page(dst_mm);
962                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
963                                 zero_page);
964                 ret = 0;
965                 goto out_unlock;
966         }
967
968         src_page = pmd_page(pmd);
969         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
970         get_page(src_page);
971         page_dup_rmap(src_page, true);
972         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
973         mm_inc_nr_ptes(dst_mm);
974         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
975
976         pmdp_set_wrprotect(src_mm, addr, src_pmd);
977         pmd = pmd_mkold(pmd_wrprotect(pmd));
978         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
979
980         ret = 0;
981 out_unlock:
982         spin_unlock(src_ptl);
983         spin_unlock(dst_ptl);
984 out:
985         return ret;
986 }
987
988 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
989 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
990                 pud_t *pud, int flags)
991 {
992         pud_t _pud;
993
994         _pud = pud_mkyoung(*pud);
995         if (flags & FOLL_WRITE)
996                 _pud = pud_mkdirty(_pud);
997         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
998                                 pud, _pud, flags & FOLL_WRITE))
999                 update_mmu_cache_pud(vma, addr, pud);
1000 }
1001
1002 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1003                 pud_t *pud, int flags)
1004 {
1005         unsigned long pfn = pud_pfn(*pud);
1006         struct mm_struct *mm = vma->vm_mm;
1007         struct dev_pagemap *pgmap;
1008         struct page *page;
1009
1010         assert_spin_locked(pud_lockptr(mm, pud));
1011
1012         if (flags & FOLL_WRITE && !pud_write(*pud))
1013                 return NULL;
1014
1015         if (pud_present(*pud) && pud_devmap(*pud))
1016                 /* pass */;
1017         else
1018                 return NULL;
1019
1020         if (flags & FOLL_TOUCH)
1021                 touch_pud(vma, addr, pud, flags);
1022
1023         /*
1024          * device mapped pages can only be returned if the
1025          * caller will manage the page reference count.
1026          */
1027         if (!(flags & FOLL_GET))
1028                 return ERR_PTR(-EEXIST);
1029
1030         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1031         pgmap = get_dev_pagemap(pfn, NULL);
1032         if (!pgmap)
1033                 return ERR_PTR(-EFAULT);
1034         page = pfn_to_page(pfn);
1035         get_page(page);
1036         put_dev_pagemap(pgmap);
1037
1038         return page;
1039 }
1040
1041 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1042                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1043                   struct vm_area_struct *vma)
1044 {
1045         spinlock_t *dst_ptl, *src_ptl;
1046         pud_t pud;
1047         int ret;
1048
1049         dst_ptl = pud_lock(dst_mm, dst_pud);
1050         src_ptl = pud_lockptr(src_mm, src_pud);
1051         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1052
1053         ret = -EAGAIN;
1054         pud = *src_pud;
1055         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1056                 goto out_unlock;
1057
1058         /*
1059          * When page table lock is held, the huge zero pud should not be
1060          * under splitting since we don't split the page itself, only pud to
1061          * a page table.
1062          */
1063         if (is_huge_zero_pud(pud)) {
1064                 /* No huge zero pud yet */
1065         }
1066
1067         pudp_set_wrprotect(src_mm, addr, src_pud);
1068         pud = pud_mkold(pud_wrprotect(pud));
1069         set_pud_at(dst_mm, addr, dst_pud, pud);
1070
1071         ret = 0;
1072 out_unlock:
1073         spin_unlock(src_ptl);
1074         spin_unlock(dst_ptl);
1075         return ret;
1076 }
1077
1078 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1079 {
1080         pud_t entry;
1081         unsigned long haddr;
1082         bool write = vmf->flags & FAULT_FLAG_WRITE;
1083
1084         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1085         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1086                 goto unlock;
1087
1088         entry = pud_mkyoung(orig_pud);
1089         if (write)
1090                 entry = pud_mkdirty(entry);
1091         haddr = vmf->address & HPAGE_PUD_MASK;
1092         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1093                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1094
1095 unlock:
1096         spin_unlock(vmf->ptl);
1097 }
1098 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1099
1100 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1101 {
1102         pmd_t entry;
1103         unsigned long haddr;
1104         bool write = vmf->flags & FAULT_FLAG_WRITE;
1105
1106         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1107         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1108                 goto unlock;
1109
1110         entry = pmd_mkyoung(orig_pmd);
1111         if (write)
1112                 entry = pmd_mkdirty(entry);
1113         haddr = vmf->address & HPAGE_PMD_MASK;
1114         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1115                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1116
1117 unlock:
1118         spin_unlock(vmf->ptl);
1119 }
1120
1121 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1122                         pmd_t orig_pmd, struct page *page)
1123 {
1124         struct vm_area_struct *vma = vmf->vma;
1125         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1126         struct mem_cgroup *memcg;
1127         pgtable_t pgtable;
1128         pmd_t _pmd;
1129         int i;
1130         vm_fault_t ret = 0;
1131         struct page **pages;
1132         unsigned long mmun_start;       /* For mmu_notifiers */
1133         unsigned long mmun_end;         /* For mmu_notifiers */
1134
1135         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1136                               GFP_KERNEL);
1137         if (unlikely(!pages)) {
1138                 ret |= VM_FAULT_OOM;
1139                 goto out;
1140         }
1141
1142         for (i = 0; i < HPAGE_PMD_NR; i++) {
1143                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1144                                                vmf->address, page_to_nid(page));
1145                 if (unlikely(!pages[i] ||
1146                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1147                                      GFP_KERNEL, &memcg, false))) {
1148                         if (pages[i])
1149                                 put_page(pages[i]);
1150                         while (--i >= 0) {
1151                                 memcg = (void *)page_private(pages[i]);
1152                                 set_page_private(pages[i], 0);
1153                                 mem_cgroup_cancel_charge(pages[i], memcg,
1154                                                 false);
1155                                 put_page(pages[i]);
1156                         }
1157                         kfree(pages);
1158                         ret |= VM_FAULT_OOM;
1159                         goto out;
1160                 }
1161                 set_page_private(pages[i], (unsigned long)memcg);
1162         }
1163
1164         for (i = 0; i < HPAGE_PMD_NR; i++) {
1165                 copy_user_highpage(pages[i], page + i,
1166                                    haddr + PAGE_SIZE * i, vma);
1167                 __SetPageUptodate(pages[i]);
1168                 cond_resched();
1169         }
1170
1171         mmun_start = haddr;
1172         mmun_end   = haddr + HPAGE_PMD_SIZE;
1173         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1174
1175         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1176         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1177                 goto out_free_pages;
1178         VM_BUG_ON_PAGE(!PageHead(page), page);
1179
1180         /*
1181          * Leave pmd empty until pte is filled note we must notify here as
1182          * concurrent CPU thread might write to new page before the call to
1183          * mmu_notifier_invalidate_range_end() happens which can lead to a
1184          * device seeing memory write in different order than CPU.
1185          *
1186          * See Documentation/vm/mmu_notifier.rst
1187          */
1188         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1189
1190         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1191         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1192
1193         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1194                 pte_t entry;
1195                 entry = mk_pte(pages[i], vma->vm_page_prot);
1196                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1197                 memcg = (void *)page_private(pages[i]);
1198                 set_page_private(pages[i], 0);
1199                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1200                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1201                 lru_cache_add_active_or_unevictable(pages[i], vma);
1202                 vmf->pte = pte_offset_map(&_pmd, haddr);
1203                 VM_BUG_ON(!pte_none(*vmf->pte));
1204                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1205                 pte_unmap(vmf->pte);
1206         }
1207         kfree(pages);
1208
1209         smp_wmb(); /* make pte visible before pmd */
1210         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1211         page_remove_rmap(page, true);
1212         spin_unlock(vmf->ptl);
1213
1214         /*
1215          * No need to double call mmu_notifier->invalidate_range() callback as
1216          * the above pmdp_huge_clear_flush_notify() did already call it.
1217          */
1218         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1219                                                 mmun_end);
1220
1221         ret |= VM_FAULT_WRITE;
1222         put_page(page);
1223
1224 out:
1225         return ret;
1226
1227 out_free_pages:
1228         spin_unlock(vmf->ptl);
1229         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1230         for (i = 0; i < HPAGE_PMD_NR; i++) {
1231                 memcg = (void *)page_private(pages[i]);
1232                 set_page_private(pages[i], 0);
1233                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1234                 put_page(pages[i]);
1235         }
1236         kfree(pages);
1237         goto out;
1238 }
1239
1240 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1241 {
1242         struct vm_area_struct *vma = vmf->vma;
1243         struct page *page = NULL, *new_page;
1244         struct mem_cgroup *memcg;
1245         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1246         unsigned long mmun_start;       /* For mmu_notifiers */
1247         unsigned long mmun_end;         /* For mmu_notifiers */
1248         gfp_t huge_gfp;                 /* for allocation and charge */
1249         vm_fault_t ret = 0;
1250
1251         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1252         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1253         if (is_huge_zero_pmd(orig_pmd))
1254                 goto alloc;
1255         spin_lock(vmf->ptl);
1256         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1257                 goto out_unlock;
1258
1259         page = pmd_page(orig_pmd);
1260         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1261         /*
1262          * We can only reuse the page if nobody else maps the huge page or it's
1263          * part.
1264          */
1265         if (!trylock_page(page)) {
1266                 get_page(page);
1267                 spin_unlock(vmf->ptl);
1268                 lock_page(page);
1269                 spin_lock(vmf->ptl);
1270                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1271                         unlock_page(page);
1272                         put_page(page);
1273                         goto out_unlock;
1274                 }
1275                 put_page(page);
1276         }
1277         if (reuse_swap_page(page, NULL)) {
1278                 pmd_t entry;
1279                 entry = pmd_mkyoung(orig_pmd);
1280                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1281                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1282                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1283                 ret |= VM_FAULT_WRITE;
1284                 unlock_page(page);
1285                 goto out_unlock;
1286         }
1287         unlock_page(page);
1288         get_page(page);
1289         spin_unlock(vmf->ptl);
1290 alloc:
1291         if (transparent_hugepage_enabled(vma) &&
1292             !transparent_hugepage_debug_cow()) {
1293                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1294                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1295         } else
1296                 new_page = NULL;
1297
1298         if (likely(new_page)) {
1299                 prep_transhuge_page(new_page);
1300         } else {
1301                 if (!page) {
1302                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1303                         ret |= VM_FAULT_FALLBACK;
1304                 } else {
1305                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1306                         if (ret & VM_FAULT_OOM) {
1307                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1308                                 ret |= VM_FAULT_FALLBACK;
1309                         }
1310                         put_page(page);
1311                 }
1312                 count_vm_event(THP_FAULT_FALLBACK);
1313                 goto out;
1314         }
1315
1316         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1317                                         huge_gfp, &memcg, true))) {
1318                 put_page(new_page);
1319                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1320                 if (page)
1321                         put_page(page);
1322                 ret |= VM_FAULT_FALLBACK;
1323                 count_vm_event(THP_FAULT_FALLBACK);
1324                 goto out;
1325         }
1326
1327         count_vm_event(THP_FAULT_ALLOC);
1328
1329         if (!page)
1330                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1331         else
1332                 copy_user_huge_page(new_page, page, vmf->address,
1333                                     vma, HPAGE_PMD_NR);
1334         __SetPageUptodate(new_page);
1335
1336         mmun_start = haddr;
1337         mmun_end   = haddr + HPAGE_PMD_SIZE;
1338         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1339
1340         spin_lock(vmf->ptl);
1341         if (page)
1342                 put_page(page);
1343         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1344                 spin_unlock(vmf->ptl);
1345                 mem_cgroup_cancel_charge(new_page, memcg, true);
1346                 put_page(new_page);
1347                 goto out_mn;
1348         } else {
1349                 pmd_t entry;
1350                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1351                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1352                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1353                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1354                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1355                 lru_cache_add_active_or_unevictable(new_page, vma);
1356                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1357                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1358                 if (!page) {
1359                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1360                 } else {
1361                         VM_BUG_ON_PAGE(!PageHead(page), page);
1362                         page_remove_rmap(page, true);
1363                         put_page(page);
1364                 }
1365                 ret |= VM_FAULT_WRITE;
1366         }
1367         spin_unlock(vmf->ptl);
1368 out_mn:
1369         /*
1370          * No need to double call mmu_notifier->invalidate_range() callback as
1371          * the above pmdp_huge_clear_flush_notify() did already call it.
1372          */
1373         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1374                                                mmun_end);
1375 out:
1376         return ret;
1377 out_unlock:
1378         spin_unlock(vmf->ptl);
1379         return ret;
1380 }
1381
1382 /*
1383  * FOLL_FORCE can write to even unwritable pmd's, but only
1384  * after we've gone through a COW cycle and they are dirty.
1385  */
1386 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1387 {
1388         return pmd_write(pmd) ||
1389                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1390 }
1391
1392 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1393                                    unsigned long addr,
1394                                    pmd_t *pmd,
1395                                    unsigned int flags)
1396 {
1397         struct mm_struct *mm = vma->vm_mm;
1398         struct page *page = NULL;
1399
1400         assert_spin_locked(pmd_lockptr(mm, pmd));
1401
1402         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1403                 goto out;
1404
1405         /* Avoid dumping huge zero page */
1406         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1407                 return ERR_PTR(-EFAULT);
1408
1409         /* Full NUMA hinting faults to serialise migration in fault paths */
1410         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1411                 goto out;
1412
1413         page = pmd_page(*pmd);
1414         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1415         if (flags & FOLL_TOUCH)
1416                 touch_pmd(vma, addr, pmd, flags);
1417         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1418                 /*
1419                  * We don't mlock() pte-mapped THPs. This way we can avoid
1420                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1421                  *
1422                  * For anon THP:
1423                  *
1424                  * In most cases the pmd is the only mapping of the page as we
1425                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1426                  * writable private mappings in populate_vma_page_range().
1427                  *
1428                  * The only scenario when we have the page shared here is if we
1429                  * mlocking read-only mapping shared over fork(). We skip
1430                  * mlocking such pages.
1431                  *
1432                  * For file THP:
1433                  *
1434                  * We can expect PageDoubleMap() to be stable under page lock:
1435                  * for file pages we set it in page_add_file_rmap(), which
1436                  * requires page to be locked.
1437                  */
1438
1439                 if (PageAnon(page) && compound_mapcount(page) != 1)
1440                         goto skip_mlock;
1441                 if (PageDoubleMap(page) || !page->mapping)
1442                         goto skip_mlock;
1443                 if (!trylock_page(page))
1444                         goto skip_mlock;
1445                 lru_add_drain();
1446                 if (page->mapping && !PageDoubleMap(page))
1447                         mlock_vma_page(page);
1448                 unlock_page(page);
1449         }
1450 skip_mlock:
1451         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1452         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1453         if (flags & FOLL_GET)
1454                 get_page(page);
1455
1456 out:
1457         return page;
1458 }
1459
1460 /* NUMA hinting page fault entry point for trans huge pmds */
1461 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1462 {
1463         struct vm_area_struct *vma = vmf->vma;
1464         struct anon_vma *anon_vma = NULL;
1465         struct page *page;
1466         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1467         int page_nid = -1, this_nid = numa_node_id();
1468         int target_nid, last_cpupid = -1;
1469         bool page_locked;
1470         bool migrated = false;
1471         bool was_writable;
1472         int flags = 0;
1473
1474         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1475         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1476                 goto out_unlock;
1477
1478         /*
1479          * If there are potential migrations, wait for completion and retry
1480          * without disrupting NUMA hinting information. Do not relock and
1481          * check_same as the page may no longer be mapped.
1482          */
1483         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1484                 page = pmd_page(*vmf->pmd);
1485                 if (!get_page_unless_zero(page))
1486                         goto out_unlock;
1487                 spin_unlock(vmf->ptl);
1488                 wait_on_page_locked(page);
1489                 put_page(page);
1490                 goto out;
1491         }
1492
1493         page = pmd_page(pmd);
1494         BUG_ON(is_huge_zero_page(page));
1495         page_nid = page_to_nid(page);
1496         last_cpupid = page_cpupid_last(page);
1497         count_vm_numa_event(NUMA_HINT_FAULTS);
1498         if (page_nid == this_nid) {
1499                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1500                 flags |= TNF_FAULT_LOCAL;
1501         }
1502
1503         /* See similar comment in do_numa_page for explanation */
1504         if (!pmd_savedwrite(pmd))
1505                 flags |= TNF_NO_GROUP;
1506
1507         /*
1508          * Acquire the page lock to serialise THP migrations but avoid dropping
1509          * page_table_lock if at all possible
1510          */
1511         page_locked = trylock_page(page);
1512         target_nid = mpol_misplaced(page, vma, haddr);
1513         if (target_nid == -1) {
1514                 /* If the page was locked, there are no parallel migrations */
1515                 if (page_locked)
1516                         goto clear_pmdnuma;
1517         }
1518
1519         /* Migration could have started since the pmd_trans_migrating check */
1520         if (!page_locked) {
1521                 page_nid = -1;
1522                 if (!get_page_unless_zero(page))
1523                         goto out_unlock;
1524                 spin_unlock(vmf->ptl);
1525                 wait_on_page_locked(page);
1526                 put_page(page);
1527                 goto out;
1528         }
1529
1530         /*
1531          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1532          * to serialises splits
1533          */
1534         get_page(page);
1535         spin_unlock(vmf->ptl);
1536         anon_vma = page_lock_anon_vma_read(page);
1537
1538         /* Confirm the PMD did not change while page_table_lock was released */
1539         spin_lock(vmf->ptl);
1540         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1541                 unlock_page(page);
1542                 put_page(page);
1543                 page_nid = -1;
1544                 goto out_unlock;
1545         }
1546
1547         /* Bail if we fail to protect against THP splits for any reason */
1548         if (unlikely(!anon_vma)) {
1549                 put_page(page);
1550                 page_nid = -1;
1551                 goto clear_pmdnuma;
1552         }
1553
1554         /*
1555          * Since we took the NUMA fault, we must have observed the !accessible
1556          * bit. Make sure all other CPUs agree with that, to avoid them
1557          * modifying the page we're about to migrate.
1558          *
1559          * Must be done under PTL such that we'll observe the relevant
1560          * inc_tlb_flush_pending().
1561          *
1562          * We are not sure a pending tlb flush here is for a huge page
1563          * mapping or not. Hence use the tlb range variant
1564          */
1565         if (mm_tlb_flush_pending(vma->vm_mm))
1566                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1567
1568         /*
1569          * Migrate the THP to the requested node, returns with page unlocked
1570          * and access rights restored.
1571          */
1572         spin_unlock(vmf->ptl);
1573
1574         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1575                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1576         if (migrated) {
1577                 flags |= TNF_MIGRATED;
1578                 page_nid = target_nid;
1579         } else
1580                 flags |= TNF_MIGRATE_FAIL;
1581
1582         goto out;
1583 clear_pmdnuma:
1584         BUG_ON(!PageLocked(page));
1585         was_writable = pmd_savedwrite(pmd);
1586         pmd = pmd_modify(pmd, vma->vm_page_prot);
1587         pmd = pmd_mkyoung(pmd);
1588         if (was_writable)
1589                 pmd = pmd_mkwrite(pmd);
1590         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1591         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1592         unlock_page(page);
1593 out_unlock:
1594         spin_unlock(vmf->ptl);
1595
1596 out:
1597         if (anon_vma)
1598                 page_unlock_anon_vma_read(anon_vma);
1599
1600         if (page_nid != -1)
1601                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1602                                 flags);
1603
1604         return 0;
1605 }
1606
1607 /*
1608  * Return true if we do MADV_FREE successfully on entire pmd page.
1609  * Otherwise, return false.
1610  */
1611 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1612                 pmd_t *pmd, unsigned long addr, unsigned long next)
1613 {
1614         spinlock_t *ptl;
1615         pmd_t orig_pmd;
1616         struct page *page;
1617         struct mm_struct *mm = tlb->mm;
1618         bool ret = false;
1619
1620         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1621
1622         ptl = pmd_trans_huge_lock(pmd, vma);
1623         if (!ptl)
1624                 goto out_unlocked;
1625
1626         orig_pmd = *pmd;
1627         if (is_huge_zero_pmd(orig_pmd))
1628                 goto out;
1629
1630         if (unlikely(!pmd_present(orig_pmd))) {
1631                 VM_BUG_ON(thp_migration_supported() &&
1632                                   !is_pmd_migration_entry(orig_pmd));
1633                 goto out;
1634         }
1635
1636         page = pmd_page(orig_pmd);
1637         /*
1638          * If other processes are mapping this page, we couldn't discard
1639          * the page unless they all do MADV_FREE so let's skip the page.
1640          */
1641         if (page_mapcount(page) != 1)
1642                 goto out;
1643
1644         if (!trylock_page(page))
1645                 goto out;
1646
1647         /*
1648          * If user want to discard part-pages of THP, split it so MADV_FREE
1649          * will deactivate only them.
1650          */
1651         if (next - addr != HPAGE_PMD_SIZE) {
1652                 get_page(page);
1653                 spin_unlock(ptl);
1654                 split_huge_page(page);
1655                 unlock_page(page);
1656                 put_page(page);
1657                 goto out_unlocked;
1658         }
1659
1660         if (PageDirty(page))
1661                 ClearPageDirty(page);
1662         unlock_page(page);
1663
1664         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1665                 pmdp_invalidate(vma, addr, pmd);
1666                 orig_pmd = pmd_mkold(orig_pmd);
1667                 orig_pmd = pmd_mkclean(orig_pmd);
1668
1669                 set_pmd_at(mm, addr, pmd, orig_pmd);
1670                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1671         }
1672
1673         mark_page_lazyfree(page);
1674         ret = true;
1675 out:
1676         spin_unlock(ptl);
1677 out_unlocked:
1678         return ret;
1679 }
1680
1681 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1682 {
1683         pgtable_t pgtable;
1684
1685         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1686         pte_free(mm, pgtable);
1687         mm_dec_nr_ptes(mm);
1688 }
1689
1690 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1691                  pmd_t *pmd, unsigned long addr)
1692 {
1693         pmd_t orig_pmd;
1694         spinlock_t *ptl;
1695
1696         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1697
1698         ptl = __pmd_trans_huge_lock(pmd, vma);
1699         if (!ptl)
1700                 return 0;
1701         /*
1702          * For architectures like ppc64 we look at deposited pgtable
1703          * when calling pmdp_huge_get_and_clear. So do the
1704          * pgtable_trans_huge_withdraw after finishing pmdp related
1705          * operations.
1706          */
1707         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1708                         tlb->fullmm);
1709         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1710         if (vma_is_dax(vma)) {
1711                 if (arch_needs_pgtable_deposit())
1712                         zap_deposited_table(tlb->mm, pmd);
1713                 spin_unlock(ptl);
1714                 if (is_huge_zero_pmd(orig_pmd))
1715                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1716         } else if (is_huge_zero_pmd(orig_pmd)) {
1717                 zap_deposited_table(tlb->mm, pmd);
1718                 spin_unlock(ptl);
1719                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1720         } else {
1721                 struct page *page = NULL;
1722                 int flush_needed = 1;
1723
1724                 if (pmd_present(orig_pmd)) {
1725                         page = pmd_page(orig_pmd);
1726                         page_remove_rmap(page, true);
1727                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1728                         VM_BUG_ON_PAGE(!PageHead(page), page);
1729                 } else if (thp_migration_supported()) {
1730                         swp_entry_t entry;
1731
1732                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1733                         entry = pmd_to_swp_entry(orig_pmd);
1734                         page = pfn_to_page(swp_offset(entry));
1735                         flush_needed = 0;
1736                 } else
1737                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1738
1739                 if (PageAnon(page)) {
1740                         zap_deposited_table(tlb->mm, pmd);
1741                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1742                 } else {
1743                         if (arch_needs_pgtable_deposit())
1744                                 zap_deposited_table(tlb->mm, pmd);
1745                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1746                 }
1747
1748                 spin_unlock(ptl);
1749                 if (flush_needed)
1750                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1751         }
1752         return 1;
1753 }
1754
1755 #ifndef pmd_move_must_withdraw
1756 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1757                                          spinlock_t *old_pmd_ptl,
1758                                          struct vm_area_struct *vma)
1759 {
1760         /*
1761          * With split pmd lock we also need to move preallocated
1762          * PTE page table if new_pmd is on different PMD page table.
1763          *
1764          * We also don't deposit and withdraw tables for file pages.
1765          */
1766         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1767 }
1768 #endif
1769
1770 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1771 {
1772 #ifdef CONFIG_MEM_SOFT_DIRTY
1773         if (unlikely(is_pmd_migration_entry(pmd)))
1774                 pmd = pmd_swp_mksoft_dirty(pmd);
1775         else if (pmd_present(pmd))
1776                 pmd = pmd_mksoft_dirty(pmd);
1777 #endif
1778         return pmd;
1779 }
1780
1781 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1782                   unsigned long new_addr, unsigned long old_end,
1783                   pmd_t *old_pmd, pmd_t *new_pmd)
1784 {
1785         spinlock_t *old_ptl, *new_ptl;
1786         pmd_t pmd;
1787         struct mm_struct *mm = vma->vm_mm;
1788         bool force_flush = false;
1789
1790         if ((old_addr & ~HPAGE_PMD_MASK) ||
1791             (new_addr & ~HPAGE_PMD_MASK) ||
1792             old_end - old_addr < HPAGE_PMD_SIZE)
1793                 return false;
1794
1795         /*
1796          * The destination pmd shouldn't be established, free_pgtables()
1797          * should have release it.
1798          */
1799         if (WARN_ON(!pmd_none(*new_pmd))) {
1800                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1801                 return false;
1802         }
1803
1804         /*
1805          * We don't have to worry about the ordering of src and dst
1806          * ptlocks because exclusive mmap_sem prevents deadlock.
1807          */
1808         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1809         if (old_ptl) {
1810                 new_ptl = pmd_lockptr(mm, new_pmd);
1811                 if (new_ptl != old_ptl)
1812                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1813                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1814                 if (pmd_present(pmd))
1815                         force_flush = true;
1816                 VM_BUG_ON(!pmd_none(*new_pmd));
1817
1818                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1819                         pgtable_t pgtable;
1820                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1821                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1822                 }
1823                 pmd = move_soft_dirty_pmd(pmd);
1824                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1825                 if (force_flush)
1826                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1827                 if (new_ptl != old_ptl)
1828                         spin_unlock(new_ptl);
1829                 spin_unlock(old_ptl);
1830                 return true;
1831         }
1832         return false;
1833 }
1834
1835 /*
1836  * Returns
1837  *  - 0 if PMD could not be locked
1838  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1839  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1840  */
1841 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1842                 unsigned long addr, pgprot_t newprot, int prot_numa)
1843 {
1844         struct mm_struct *mm = vma->vm_mm;
1845         spinlock_t *ptl;
1846         pmd_t entry;
1847         bool preserve_write;
1848         int ret;
1849
1850         ptl = __pmd_trans_huge_lock(pmd, vma);
1851         if (!ptl)
1852                 return 0;
1853
1854         preserve_write = prot_numa && pmd_write(*pmd);
1855         ret = 1;
1856
1857 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1858         if (is_swap_pmd(*pmd)) {
1859                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1860
1861                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1862                 if (is_write_migration_entry(entry)) {
1863                         pmd_t newpmd;
1864                         /*
1865                          * A protection check is difficult so
1866                          * just be safe and disable write
1867                          */
1868                         make_migration_entry_read(&entry);
1869                         newpmd = swp_entry_to_pmd(entry);
1870                         if (pmd_swp_soft_dirty(*pmd))
1871                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1872                         set_pmd_at(mm, addr, pmd, newpmd);
1873                 }
1874                 goto unlock;
1875         }
1876 #endif
1877
1878         /*
1879          * Avoid trapping faults against the zero page. The read-only
1880          * data is likely to be read-cached on the local CPU and
1881          * local/remote hits to the zero page are not interesting.
1882          */
1883         if (prot_numa && is_huge_zero_pmd(*pmd))
1884                 goto unlock;
1885
1886         if (prot_numa && pmd_protnone(*pmd))
1887                 goto unlock;
1888
1889         /*
1890          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1891          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1892          * which is also under down_read(mmap_sem):
1893          *
1894          *      CPU0:                           CPU1:
1895          *                              change_huge_pmd(prot_numa=1)
1896          *                               pmdp_huge_get_and_clear_notify()
1897          * madvise_dontneed()
1898          *  zap_pmd_range()
1899          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1900          *   // skip the pmd
1901          *                               set_pmd_at();
1902          *                               // pmd is re-established
1903          *
1904          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1905          * which may break userspace.
1906          *
1907          * pmdp_invalidate() is required to make sure we don't miss
1908          * dirty/young flags set by hardware.
1909          */
1910         entry = pmdp_invalidate(vma, addr, pmd);
1911
1912         entry = pmd_modify(entry, newprot);
1913         if (preserve_write)
1914                 entry = pmd_mk_savedwrite(entry);
1915         ret = HPAGE_PMD_NR;
1916         set_pmd_at(mm, addr, pmd, entry);
1917         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1918 unlock:
1919         spin_unlock(ptl);
1920         return ret;
1921 }
1922
1923 /*
1924  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1925  *
1926  * Note that if it returns page table lock pointer, this routine returns without
1927  * unlocking page table lock. So callers must unlock it.
1928  */
1929 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1930 {
1931         spinlock_t *ptl;
1932         ptl = pmd_lock(vma->vm_mm, pmd);
1933         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1934                         pmd_devmap(*pmd)))
1935                 return ptl;
1936         spin_unlock(ptl);
1937         return NULL;
1938 }
1939
1940 /*
1941  * Returns true if a given pud maps a thp, false otherwise.
1942  *
1943  * Note that if it returns true, this routine returns without unlocking page
1944  * table lock. So callers must unlock it.
1945  */
1946 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1947 {
1948         spinlock_t *ptl;
1949
1950         ptl = pud_lock(vma->vm_mm, pud);
1951         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1952                 return ptl;
1953         spin_unlock(ptl);
1954         return NULL;
1955 }
1956
1957 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1958 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1959                  pud_t *pud, unsigned long addr)
1960 {
1961         pud_t orig_pud;
1962         spinlock_t *ptl;
1963
1964         ptl = __pud_trans_huge_lock(pud, vma);
1965         if (!ptl)
1966                 return 0;
1967         /*
1968          * For architectures like ppc64 we look at deposited pgtable
1969          * when calling pudp_huge_get_and_clear. So do the
1970          * pgtable_trans_huge_withdraw after finishing pudp related
1971          * operations.
1972          */
1973         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1974                         tlb->fullmm);
1975         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1976         if (vma_is_dax(vma)) {
1977                 spin_unlock(ptl);
1978                 /* No zero page support yet */
1979         } else {
1980                 /* No support for anonymous PUD pages yet */
1981                 BUG();
1982         }
1983         return 1;
1984 }
1985
1986 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1987                 unsigned long haddr)
1988 {
1989         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1990         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1991         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1992         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1993
1994         count_vm_event(THP_SPLIT_PUD);
1995
1996         pudp_huge_clear_flush_notify(vma, haddr, pud);
1997 }
1998
1999 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2000                 unsigned long address)
2001 {
2002         spinlock_t *ptl;
2003         struct mm_struct *mm = vma->vm_mm;
2004         unsigned long haddr = address & HPAGE_PUD_MASK;
2005
2006         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2007         ptl = pud_lock(mm, pud);
2008         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2009                 goto out;
2010         __split_huge_pud_locked(vma, pud, haddr);
2011
2012 out:
2013         spin_unlock(ptl);
2014         /*
2015          * No need to double call mmu_notifier->invalidate_range() callback as
2016          * the above pudp_huge_clear_flush_notify() did already call it.
2017          */
2018         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2019                                                HPAGE_PUD_SIZE);
2020 }
2021 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2022
2023 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2024                 unsigned long haddr, pmd_t *pmd)
2025 {
2026         struct mm_struct *mm = vma->vm_mm;
2027         pgtable_t pgtable;
2028         pmd_t _pmd;
2029         int i;
2030
2031         /*
2032          * Leave pmd empty until pte is filled note that it is fine to delay
2033          * notification until mmu_notifier_invalidate_range_end() as we are
2034          * replacing a zero pmd write protected page with a zero pte write
2035          * protected page.
2036          *
2037          * See Documentation/vm/mmu_notifier.rst
2038          */
2039         pmdp_huge_clear_flush(vma, haddr, pmd);
2040
2041         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2042         pmd_populate(mm, &_pmd, pgtable);
2043
2044         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2045                 pte_t *pte, entry;
2046                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2047                 entry = pte_mkspecial(entry);
2048                 pte = pte_offset_map(&_pmd, haddr);
2049                 VM_BUG_ON(!pte_none(*pte));
2050                 set_pte_at(mm, haddr, pte, entry);
2051                 pte_unmap(pte);
2052         }
2053         smp_wmb(); /* make pte visible before pmd */
2054         pmd_populate(mm, pmd, pgtable);
2055 }
2056
2057 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2058                 unsigned long haddr, bool freeze)
2059 {
2060         struct mm_struct *mm = vma->vm_mm;
2061         struct page *page;
2062         pgtable_t pgtable;
2063         pmd_t old_pmd, _pmd;
2064         bool young, write, soft_dirty, pmd_migration = false;
2065         unsigned long addr;
2066         int i;
2067
2068         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2069         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2070         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2071         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2072                                 && !pmd_devmap(*pmd));
2073
2074         count_vm_event(THP_SPLIT_PMD);
2075
2076         if (!vma_is_anonymous(vma)) {
2077                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2078                 /*
2079                  * We are going to unmap this huge page. So
2080                  * just go ahead and zap it
2081                  */
2082                 if (arch_needs_pgtable_deposit())
2083                         zap_deposited_table(mm, pmd);
2084                 if (vma_is_dax(vma))
2085                         return;
2086                 page = pmd_page(_pmd);
2087                 if (!PageDirty(page) && pmd_dirty(_pmd))
2088                         set_page_dirty(page);
2089                 if (!PageReferenced(page) && pmd_young(_pmd))
2090                         SetPageReferenced(page);
2091                 page_remove_rmap(page, true);
2092                 put_page(page);
2093                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2094                 return;
2095         } else if (is_huge_zero_pmd(*pmd)) {
2096                 /*
2097                  * FIXME: Do we want to invalidate secondary mmu by calling
2098                  * mmu_notifier_invalidate_range() see comments below inside
2099                  * __split_huge_pmd() ?
2100                  *
2101                  * We are going from a zero huge page write protected to zero
2102                  * small page also write protected so it does not seems useful
2103                  * to invalidate secondary mmu at this time.
2104                  */
2105                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2106         }
2107
2108         /*
2109          * Up to this point the pmd is present and huge and userland has the
2110          * whole access to the hugepage during the split (which happens in
2111          * place). If we overwrite the pmd with the not-huge version pointing
2112          * to the pte here (which of course we could if all CPUs were bug
2113          * free), userland could trigger a small page size TLB miss on the
2114          * small sized TLB while the hugepage TLB entry is still established in
2115          * the huge TLB. Some CPU doesn't like that.
2116          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2117          * 383 on page 93. Intel should be safe but is also warns that it's
2118          * only safe if the permission and cache attributes of the two entries
2119          * loaded in the two TLB is identical (which should be the case here).
2120          * But it is generally safer to never allow small and huge TLB entries
2121          * for the same virtual address to be loaded simultaneously. So instead
2122          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2123          * current pmd notpresent (atomically because here the pmd_trans_huge
2124          * must remain set at all times on the pmd until the split is complete
2125          * for this pmd), then we flush the SMP TLB and finally we write the
2126          * non-huge version of the pmd entry with pmd_populate.
2127          */
2128         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2129
2130 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2131         pmd_migration = is_pmd_migration_entry(old_pmd);
2132         if (pmd_migration) {
2133                 swp_entry_t entry;
2134
2135                 entry = pmd_to_swp_entry(old_pmd);
2136                 page = pfn_to_page(swp_offset(entry));
2137         } else
2138 #endif
2139                 page = pmd_page(old_pmd);
2140         VM_BUG_ON_PAGE(!page_count(page), page);
2141         page_ref_add(page, HPAGE_PMD_NR - 1);
2142         if (pmd_dirty(old_pmd))
2143                 SetPageDirty(page);
2144         write = pmd_write(old_pmd);
2145         young = pmd_young(old_pmd);
2146         soft_dirty = pmd_soft_dirty(old_pmd);
2147
2148         /*
2149          * Withdraw the table only after we mark the pmd entry invalid.
2150          * This's critical for some architectures (Power).
2151          */
2152         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2153         pmd_populate(mm, &_pmd, pgtable);
2154
2155         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2156                 pte_t entry, *pte;
2157                 /*
2158                  * Note that NUMA hinting access restrictions are not
2159                  * transferred to avoid any possibility of altering
2160                  * permissions across VMAs.
2161                  */
2162                 if (freeze || pmd_migration) {
2163                         swp_entry_t swp_entry;
2164                         swp_entry = make_migration_entry(page + i, write);
2165                         entry = swp_entry_to_pte(swp_entry);
2166                         if (soft_dirty)
2167                                 entry = pte_swp_mksoft_dirty(entry);
2168                 } else {
2169                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2170                         entry = maybe_mkwrite(entry, vma);
2171                         if (!write)
2172                                 entry = pte_wrprotect(entry);
2173                         if (!young)
2174                                 entry = pte_mkold(entry);
2175                         if (soft_dirty)
2176                                 entry = pte_mksoft_dirty(entry);
2177                 }
2178                 pte = pte_offset_map(&_pmd, addr);
2179                 BUG_ON(!pte_none(*pte));
2180                 set_pte_at(mm, addr, pte, entry);
2181                 atomic_inc(&page[i]._mapcount);
2182                 pte_unmap(pte);
2183         }
2184
2185         /*
2186          * Set PG_double_map before dropping compound_mapcount to avoid
2187          * false-negative page_mapped().
2188          */
2189         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2190                 for (i = 0; i < HPAGE_PMD_NR; i++)
2191                         atomic_inc(&page[i]._mapcount);
2192         }
2193
2194         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2195                 /* Last compound_mapcount is gone. */
2196                 __dec_node_page_state(page, NR_ANON_THPS);
2197                 if (TestClearPageDoubleMap(page)) {
2198                         /* No need in mapcount reference anymore */
2199                         for (i = 0; i < HPAGE_PMD_NR; i++)
2200                                 atomic_dec(&page[i]._mapcount);
2201                 }
2202         }
2203
2204         smp_wmb(); /* make pte visible before pmd */
2205         pmd_populate(mm, pmd, pgtable);
2206
2207         if (freeze) {
2208                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2209                         page_remove_rmap(page + i, false);
2210                         put_page(page + i);
2211                 }
2212         }
2213 }
2214
2215 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2216                 unsigned long address, bool freeze, struct page *page)
2217 {
2218         spinlock_t *ptl;
2219         struct mm_struct *mm = vma->vm_mm;
2220         unsigned long haddr = address & HPAGE_PMD_MASK;
2221
2222         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2223         ptl = pmd_lock(mm, pmd);
2224
2225         /*
2226          * If caller asks to setup a migration entries, we need a page to check
2227          * pmd against. Otherwise we can end up replacing wrong page.
2228          */
2229         VM_BUG_ON(freeze && !page);
2230         if (page && page != pmd_page(*pmd))
2231                 goto out;
2232
2233         if (pmd_trans_huge(*pmd)) {
2234                 page = pmd_page(*pmd);
2235                 if (PageMlocked(page))
2236                         clear_page_mlock(page);
2237         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2238                 goto out;
2239         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2240 out:
2241         spin_unlock(ptl);
2242         /*
2243          * No need to double call mmu_notifier->invalidate_range() callback.
2244          * They are 3 cases to consider inside __split_huge_pmd_locked():
2245          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2246          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2247          *    fault will trigger a flush_notify before pointing to a new page
2248          *    (it is fine if the secondary mmu keeps pointing to the old zero
2249          *    page in the meantime)
2250          *  3) Split a huge pmd into pte pointing to the same page. No need
2251          *     to invalidate secondary tlb entry they are all still valid.
2252          *     any further changes to individual pte will notify. So no need
2253          *     to call mmu_notifier->invalidate_range()
2254          */
2255         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2256                                                HPAGE_PMD_SIZE);
2257 }
2258
2259 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2260                 bool freeze, struct page *page)
2261 {
2262         pgd_t *pgd;
2263         p4d_t *p4d;
2264         pud_t *pud;
2265         pmd_t *pmd;
2266
2267         pgd = pgd_offset(vma->vm_mm, address);
2268         if (!pgd_present(*pgd))
2269                 return;
2270
2271         p4d = p4d_offset(pgd, address);
2272         if (!p4d_present(*p4d))
2273                 return;
2274
2275         pud = pud_offset(p4d, address);
2276         if (!pud_present(*pud))
2277                 return;
2278
2279         pmd = pmd_offset(pud, address);
2280
2281         __split_huge_pmd(vma, pmd, address, freeze, page);
2282 }
2283
2284 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2285                              unsigned long start,
2286                              unsigned long end,
2287                              long adjust_next)
2288 {
2289         /*
2290          * If the new start address isn't hpage aligned and it could
2291          * previously contain an hugepage: check if we need to split
2292          * an huge pmd.
2293          */
2294         if (start & ~HPAGE_PMD_MASK &&
2295             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2296             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2297                 split_huge_pmd_address(vma, start, false, NULL);
2298
2299         /*
2300          * If the new end address isn't hpage aligned and it could
2301          * previously contain an hugepage: check if we need to split
2302          * an huge pmd.
2303          */
2304         if (end & ~HPAGE_PMD_MASK &&
2305             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2306             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2307                 split_huge_pmd_address(vma, end, false, NULL);
2308
2309         /*
2310          * If we're also updating the vma->vm_next->vm_start, if the new
2311          * vm_next->vm_start isn't page aligned and it could previously
2312          * contain an hugepage: check if we need to split an huge pmd.
2313          */
2314         if (adjust_next > 0) {
2315                 struct vm_area_struct *next = vma->vm_next;
2316                 unsigned long nstart = next->vm_start;
2317                 nstart += adjust_next << PAGE_SHIFT;
2318                 if (nstart & ~HPAGE_PMD_MASK &&
2319                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2320                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2321                         split_huge_pmd_address(next, nstart, false, NULL);
2322         }
2323 }
2324
2325 static void freeze_page(struct page *page)
2326 {
2327         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2328                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2329         bool unmap_success;
2330
2331         VM_BUG_ON_PAGE(!PageHead(page), page);
2332
2333         if (PageAnon(page))
2334                 ttu_flags |= TTU_SPLIT_FREEZE;
2335
2336         unmap_success = try_to_unmap(page, ttu_flags);
2337         VM_BUG_ON_PAGE(!unmap_success, page);
2338 }
2339
2340 static void unfreeze_page(struct page *page)
2341 {
2342         int i;
2343         if (PageTransHuge(page)) {
2344                 remove_migration_ptes(page, page, true);
2345         } else {
2346                 for (i = 0; i < HPAGE_PMD_NR; i++)
2347                         remove_migration_ptes(page + i, page + i, true);
2348         }
2349 }
2350
2351 static void __split_huge_page_tail(struct page *head, int tail,
2352                 struct lruvec *lruvec, struct list_head *list)
2353 {
2354         struct page *page_tail = head + tail;
2355
2356         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2357
2358         /*
2359          * Clone page flags before unfreezing refcount.
2360          *
2361          * After successful get_page_unless_zero() might follow flags change,
2362          * for exmaple lock_page() which set PG_waiters.
2363          */
2364         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2365         page_tail->flags |= (head->flags &
2366                         ((1L << PG_referenced) |
2367                          (1L << PG_swapbacked) |
2368                          (1L << PG_swapcache) |
2369                          (1L << PG_mlocked) |
2370                          (1L << PG_uptodate) |
2371                          (1L << PG_active) |
2372                          (1L << PG_workingset) |
2373                          (1L << PG_locked) |
2374                          (1L << PG_unevictable) |
2375                          (1L << PG_dirty)));
2376
2377         /* Page flags must be visible before we make the page non-compound. */
2378         smp_wmb();
2379
2380         /*
2381          * Clear PageTail before unfreezing page refcount.
2382          *
2383          * After successful get_page_unless_zero() might follow put_page()
2384          * which needs correct compound_head().
2385          */
2386         clear_compound_head(page_tail);
2387
2388         /* Finally unfreeze refcount. Additional reference from page cache. */
2389         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2390                                           PageSwapCache(head)));
2391
2392         if (page_is_young(head))
2393                 set_page_young(page_tail);
2394         if (page_is_idle(head))
2395                 set_page_idle(page_tail);
2396
2397         /* ->mapping in first tail page is compound_mapcount */
2398         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2399                         page_tail);
2400         page_tail->mapping = head->mapping;
2401
2402         page_tail->index = head->index + tail;
2403         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2404
2405         /*
2406          * always add to the tail because some iterators expect new
2407          * pages to show after the currently processed elements - e.g.
2408          * migrate_pages
2409          */
2410         lru_add_page_tail(head, page_tail, lruvec, list);
2411 }
2412
2413 static void __split_huge_page(struct page *page, struct list_head *list,
2414                 unsigned long flags)
2415 {
2416         struct page *head = compound_head(page);
2417         struct zone *zone = page_zone(head);
2418         struct lruvec *lruvec;
2419         pgoff_t end = -1;
2420         int i;
2421
2422         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2423
2424         /* complete memcg works before add pages to LRU */
2425         mem_cgroup_split_huge_fixup(head);
2426
2427         if (!PageAnon(page))
2428                 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2429
2430         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2431                 __split_huge_page_tail(head, i, lruvec, list);
2432                 /* Some pages can be beyond i_size: drop them from page cache */
2433                 if (head[i].index >= end) {
2434                         ClearPageDirty(head + i);
2435                         __delete_from_page_cache(head + i, NULL);
2436                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2437                                 shmem_uncharge(head->mapping->host, 1);
2438                         put_page(head + i);
2439                 }
2440         }
2441
2442         ClearPageCompound(head);
2443         /* See comment in __split_huge_page_tail() */
2444         if (PageAnon(head)) {
2445                 /* Additional pin to radix tree of swap cache */
2446                 if (PageSwapCache(head))
2447                         page_ref_add(head, 2);
2448                 else
2449                         page_ref_inc(head);
2450         } else {
2451                 /* Additional pin to radix tree */
2452                 page_ref_add(head, 2);
2453                 xa_unlock(&head->mapping->i_pages);
2454         }
2455
2456         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2457
2458         unfreeze_page(head);
2459
2460         for (i = 0; i < HPAGE_PMD_NR; i++) {
2461                 struct page *subpage = head + i;
2462                 if (subpage == page)
2463                         continue;
2464                 unlock_page(subpage);
2465
2466                 /*
2467                  * Subpages may be freed if there wasn't any mapping
2468                  * like if add_to_swap() is running on a lru page that
2469                  * had its mapping zapped. And freeing these pages
2470                  * requires taking the lru_lock so we do the put_page
2471                  * of the tail pages after the split is complete.
2472                  */
2473                 put_page(subpage);
2474         }
2475 }
2476
2477 int total_mapcount(struct page *page)
2478 {
2479         int i, compound, ret;
2480
2481         VM_BUG_ON_PAGE(PageTail(page), page);
2482
2483         if (likely(!PageCompound(page)))
2484                 return atomic_read(&page->_mapcount) + 1;
2485
2486         compound = compound_mapcount(page);
2487         if (PageHuge(page))
2488                 return compound;
2489         ret = compound;
2490         for (i = 0; i < HPAGE_PMD_NR; i++)
2491                 ret += atomic_read(&page[i]._mapcount) + 1;
2492         /* File pages has compound_mapcount included in _mapcount */
2493         if (!PageAnon(page))
2494                 return ret - compound * HPAGE_PMD_NR;
2495         if (PageDoubleMap(page))
2496                 ret -= HPAGE_PMD_NR;
2497         return ret;
2498 }
2499
2500 /*
2501  * This calculates accurately how many mappings a transparent hugepage
2502  * has (unlike page_mapcount() which isn't fully accurate). This full
2503  * accuracy is primarily needed to know if copy-on-write faults can
2504  * reuse the page and change the mapping to read-write instead of
2505  * copying them. At the same time this returns the total_mapcount too.
2506  *
2507  * The function returns the highest mapcount any one of the subpages
2508  * has. If the return value is one, even if different processes are
2509  * mapping different subpages of the transparent hugepage, they can
2510  * all reuse it, because each process is reusing a different subpage.
2511  *
2512  * The total_mapcount is instead counting all virtual mappings of the
2513  * subpages. If the total_mapcount is equal to "one", it tells the
2514  * caller all mappings belong to the same "mm" and in turn the
2515  * anon_vma of the transparent hugepage can become the vma->anon_vma
2516  * local one as no other process may be mapping any of the subpages.
2517  *
2518  * It would be more accurate to replace page_mapcount() with
2519  * page_trans_huge_mapcount(), however we only use
2520  * page_trans_huge_mapcount() in the copy-on-write faults where we
2521  * need full accuracy to avoid breaking page pinning, because
2522  * page_trans_huge_mapcount() is slower than page_mapcount().
2523  */
2524 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2525 {
2526         int i, ret, _total_mapcount, mapcount;
2527
2528         /* hugetlbfs shouldn't call it */
2529         VM_BUG_ON_PAGE(PageHuge(page), page);
2530
2531         if (likely(!PageTransCompound(page))) {
2532                 mapcount = atomic_read(&page->_mapcount) + 1;
2533                 if (total_mapcount)
2534                         *total_mapcount = mapcount;
2535                 return mapcount;
2536         }
2537
2538         page = compound_head(page);
2539
2540         _total_mapcount = ret = 0;
2541         for (i = 0; i < HPAGE_PMD_NR; i++) {
2542                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2543                 ret = max(ret, mapcount);
2544                 _total_mapcount += mapcount;
2545         }
2546         if (PageDoubleMap(page)) {
2547                 ret -= 1;
2548                 _total_mapcount -= HPAGE_PMD_NR;
2549         }
2550         mapcount = compound_mapcount(page);
2551         ret += mapcount;
2552         _total_mapcount += mapcount;
2553         if (total_mapcount)
2554                 *total_mapcount = _total_mapcount;
2555         return ret;
2556 }
2557
2558 /* Racy check whether the huge page can be split */
2559 bool can_split_huge_page(struct page *page, int *pextra_pins)
2560 {
2561         int extra_pins;
2562
2563         /* Additional pins from radix tree */
2564         if (PageAnon(page))
2565                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2566         else
2567                 extra_pins = HPAGE_PMD_NR;
2568         if (pextra_pins)
2569                 *pextra_pins = extra_pins;
2570         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2571 }
2572
2573 /*
2574  * This function splits huge page into normal pages. @page can point to any
2575  * subpage of huge page to split. Split doesn't change the position of @page.
2576  *
2577  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2578  * The huge page must be locked.
2579  *
2580  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2581  *
2582  * Both head page and tail pages will inherit mapping, flags, and so on from
2583  * the hugepage.
2584  *
2585  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2586  * they are not mapped.
2587  *
2588  * Returns 0 if the hugepage is split successfully.
2589  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2590  * us.
2591  */
2592 int split_huge_page_to_list(struct page *page, struct list_head *list)
2593 {
2594         struct page *head = compound_head(page);
2595         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2596         struct anon_vma *anon_vma = NULL;
2597         struct address_space *mapping = NULL;
2598         int count, mapcount, extra_pins, ret;
2599         bool mlocked;
2600         unsigned long flags;
2601
2602         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2603         VM_BUG_ON_PAGE(!PageLocked(page), page);
2604         VM_BUG_ON_PAGE(!PageCompound(page), page);
2605
2606         if (PageWriteback(page))
2607                 return -EBUSY;
2608
2609         if (PageAnon(head)) {
2610                 /*
2611                  * The caller does not necessarily hold an mmap_sem that would
2612                  * prevent the anon_vma disappearing so we first we take a
2613                  * reference to it and then lock the anon_vma for write. This
2614                  * is similar to page_lock_anon_vma_read except the write lock
2615                  * is taken to serialise against parallel split or collapse
2616                  * operations.
2617                  */
2618                 anon_vma = page_get_anon_vma(head);
2619                 if (!anon_vma) {
2620                         ret = -EBUSY;
2621                         goto out;
2622                 }
2623                 mapping = NULL;
2624                 anon_vma_lock_write(anon_vma);
2625         } else {
2626                 mapping = head->mapping;
2627
2628                 /* Truncated ? */
2629                 if (!mapping) {
2630                         ret = -EBUSY;
2631                         goto out;
2632                 }
2633
2634                 anon_vma = NULL;
2635                 i_mmap_lock_read(mapping);
2636         }
2637
2638         /*
2639          * Racy check if we can split the page, before freeze_page() will
2640          * split PMDs
2641          */
2642         if (!can_split_huge_page(head, &extra_pins)) {
2643                 ret = -EBUSY;
2644                 goto out_unlock;
2645         }
2646
2647         mlocked = PageMlocked(page);
2648         freeze_page(head);
2649         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2650
2651         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2652         if (mlocked)
2653                 lru_add_drain();
2654
2655         /* prevent PageLRU to go away from under us, and freeze lru stats */
2656         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2657
2658         if (mapping) {
2659                 void **pslot;
2660
2661                 xa_lock(&mapping->i_pages);
2662                 pslot = radix_tree_lookup_slot(&mapping->i_pages,
2663                                 page_index(head));
2664                 /*
2665                  * Check if the head page is present in radix tree.
2666                  * We assume all tail are present too, if head is there.
2667                  */
2668                 if (radix_tree_deref_slot_protected(pslot,
2669                                         &mapping->i_pages.xa_lock) != head)
2670                         goto fail;
2671         }
2672
2673         /* Prevent deferred_split_scan() touching ->_refcount */
2674         spin_lock(&pgdata->split_queue_lock);
2675         count = page_count(head);
2676         mapcount = total_mapcount(head);
2677         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2678                 if (!list_empty(page_deferred_list(head))) {
2679                         pgdata->split_queue_len--;
2680                         list_del(page_deferred_list(head));
2681                 }
2682                 if (mapping)
2683                         __dec_node_page_state(page, NR_SHMEM_THPS);
2684                 spin_unlock(&pgdata->split_queue_lock);
2685                 __split_huge_page(page, list, flags);
2686                 if (PageSwapCache(head)) {
2687                         swp_entry_t entry = { .val = page_private(head) };
2688
2689                         ret = split_swap_cluster(entry);
2690                 } else
2691                         ret = 0;
2692         } else {
2693                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2694                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2695                                         mapcount, count);
2696                         if (PageTail(page))
2697                                 dump_page(head, NULL);
2698                         dump_page(page, "total_mapcount(head) > 0");
2699                         BUG();
2700                 }
2701                 spin_unlock(&pgdata->split_queue_lock);
2702 fail:           if (mapping)
2703                         xa_unlock(&mapping->i_pages);
2704                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2705                 unfreeze_page(head);
2706                 ret = -EBUSY;
2707         }
2708
2709 out_unlock:
2710         if (anon_vma) {
2711                 anon_vma_unlock_write(anon_vma);
2712                 put_anon_vma(anon_vma);
2713         }
2714         if (mapping)
2715                 i_mmap_unlock_read(mapping);
2716 out:
2717         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2718         return ret;
2719 }
2720
2721 void free_transhuge_page(struct page *page)
2722 {
2723         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2724         unsigned long flags;
2725
2726         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2727         if (!list_empty(page_deferred_list(page))) {
2728                 pgdata->split_queue_len--;
2729                 list_del(page_deferred_list(page));
2730         }
2731         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2732         free_compound_page(page);
2733 }
2734
2735 void deferred_split_huge_page(struct page *page)
2736 {
2737         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2738         unsigned long flags;
2739
2740         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2741
2742         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2743         if (list_empty(page_deferred_list(page))) {
2744                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2745                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2746                 pgdata->split_queue_len++;
2747         }
2748         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2749 }
2750
2751 static unsigned long deferred_split_count(struct shrinker *shrink,
2752                 struct shrink_control *sc)
2753 {
2754         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2755         return READ_ONCE(pgdata->split_queue_len);
2756 }
2757
2758 static unsigned long deferred_split_scan(struct shrinker *shrink,
2759                 struct shrink_control *sc)
2760 {
2761         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2762         unsigned long flags;
2763         LIST_HEAD(list), *pos, *next;
2764         struct page *page;
2765         int split = 0;
2766
2767         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2768         /* Take pin on all head pages to avoid freeing them under us */
2769         list_for_each_safe(pos, next, &pgdata->split_queue) {
2770                 page = list_entry((void *)pos, struct page, mapping);
2771                 page = compound_head(page);
2772                 if (get_page_unless_zero(page)) {
2773                         list_move(page_deferred_list(page), &list);
2774                 } else {
2775                         /* We lost race with put_compound_page() */
2776                         list_del_init(page_deferred_list(page));
2777                         pgdata->split_queue_len--;
2778                 }
2779                 if (!--sc->nr_to_scan)
2780                         break;
2781         }
2782         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2783
2784         list_for_each_safe(pos, next, &list) {
2785                 page = list_entry((void *)pos, struct page, mapping);
2786                 if (!trylock_page(page))
2787                         goto next;
2788                 /* split_huge_page() removes page from list on success */
2789                 if (!split_huge_page(page))
2790                         split++;
2791                 unlock_page(page);
2792 next:
2793                 put_page(page);
2794         }
2795
2796         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2797         list_splice_tail(&list, &pgdata->split_queue);
2798         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2799
2800         /*
2801          * Stop shrinker if we didn't split any page, but the queue is empty.
2802          * This can happen if pages were freed under us.
2803          */
2804         if (!split && list_empty(&pgdata->split_queue))
2805                 return SHRINK_STOP;
2806         return split;
2807 }
2808
2809 static struct shrinker deferred_split_shrinker = {
2810         .count_objects = deferred_split_count,
2811         .scan_objects = deferred_split_scan,
2812         .seeks = DEFAULT_SEEKS,
2813         .flags = SHRINKER_NUMA_AWARE,
2814 };
2815
2816 #ifdef CONFIG_DEBUG_FS
2817 static int split_huge_pages_set(void *data, u64 val)
2818 {
2819         struct zone *zone;
2820         struct page *page;
2821         unsigned long pfn, max_zone_pfn;
2822         unsigned long total = 0, split = 0;
2823
2824         if (val != 1)
2825                 return -EINVAL;
2826
2827         for_each_populated_zone(zone) {
2828                 max_zone_pfn = zone_end_pfn(zone);
2829                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2830                         if (!pfn_valid(pfn))
2831                                 continue;
2832
2833                         page = pfn_to_page(pfn);
2834                         if (!get_page_unless_zero(page))
2835                                 continue;
2836
2837                         if (zone != page_zone(page))
2838                                 goto next;
2839
2840                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2841                                 goto next;
2842
2843                         total++;
2844                         lock_page(page);
2845                         if (!split_huge_page(page))
2846                                 split++;
2847                         unlock_page(page);
2848 next:
2849                         put_page(page);
2850                 }
2851         }
2852
2853         pr_info("%lu of %lu THP split\n", split, total);
2854
2855         return 0;
2856 }
2857 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2858                 "%llu\n");
2859
2860 static int __init split_huge_pages_debugfs(void)
2861 {
2862         void *ret;
2863
2864         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2865                         &split_huge_pages_fops);
2866         if (!ret)
2867                 pr_warn("Failed to create split_huge_pages in debugfs");
2868         return 0;
2869 }
2870 late_initcall(split_huge_pages_debugfs);
2871 #endif
2872
2873 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2874 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2875                 struct page *page)
2876 {
2877         struct vm_area_struct *vma = pvmw->vma;
2878         struct mm_struct *mm = vma->vm_mm;
2879         unsigned long address = pvmw->address;
2880         pmd_t pmdval;
2881         swp_entry_t entry;
2882         pmd_t pmdswp;
2883
2884         if (!(pvmw->pmd && !pvmw->pte))
2885                 return;
2886
2887         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2888         pmdval = *pvmw->pmd;
2889         pmdp_invalidate(vma, address, pvmw->pmd);
2890         if (pmd_dirty(pmdval))
2891                 set_page_dirty(page);
2892         entry = make_migration_entry(page, pmd_write(pmdval));
2893         pmdswp = swp_entry_to_pmd(entry);
2894         if (pmd_soft_dirty(pmdval))
2895                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2896         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2897         page_remove_rmap(page, true);
2898         put_page(page);
2899 }
2900
2901 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2902 {
2903         struct vm_area_struct *vma = pvmw->vma;
2904         struct mm_struct *mm = vma->vm_mm;
2905         unsigned long address = pvmw->address;
2906         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2907         pmd_t pmde;
2908         swp_entry_t entry;
2909
2910         if (!(pvmw->pmd && !pvmw->pte))
2911                 return;
2912
2913         entry = pmd_to_swp_entry(*pvmw->pmd);
2914         get_page(new);
2915         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2916         if (pmd_swp_soft_dirty(*pvmw->pmd))
2917                 pmde = pmd_mksoft_dirty(pmde);
2918         if (is_write_migration_entry(entry))
2919                 pmde = maybe_pmd_mkwrite(pmde, vma);
2920
2921         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2922         if (PageAnon(new))
2923                 page_add_anon_rmap(new, vma, mmun_start, true);
2924         else
2925                 page_add_file_rmap(new, true);
2926         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2927         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2928                 mlock_vma_page(new);
2929         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2930 }
2931 #endif