mm: put_and_wait_on_page_locked() while page is migrated
[sfrench/cifs-2.6.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         /* Always do synchronous compaction */
637         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
638                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
639
640         /* Kick kcompactd and fail quickly */
641         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
642                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
643
644         /* Synchronous compaction if madvised, otherwise kick kcompactd */
645         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
646                 return GFP_TRANSHUGE_LIGHT |
647                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
648                                         __GFP_KSWAPD_RECLAIM);
649
650         /* Only do synchronous compaction if madvised */
651         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
652                 return GFP_TRANSHUGE_LIGHT |
653                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
654
655         return GFP_TRANSHUGE_LIGHT;
656 }
657
658 /* Caller must hold page table lock. */
659 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
660                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
661                 struct page *zero_page)
662 {
663         pmd_t entry;
664         if (!pmd_none(*pmd))
665                 return false;
666         entry = mk_pmd(zero_page, vma->vm_page_prot);
667         entry = pmd_mkhuge(entry);
668         if (pgtable)
669                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
670         set_pmd_at(mm, haddr, pmd, entry);
671         mm_inc_nr_ptes(mm);
672         return true;
673 }
674
675 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
676 {
677         struct vm_area_struct *vma = vmf->vma;
678         gfp_t gfp;
679         struct page *page;
680         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
681
682         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
683                 return VM_FAULT_FALLBACK;
684         if (unlikely(anon_vma_prepare(vma)))
685                 return VM_FAULT_OOM;
686         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
687                 return VM_FAULT_OOM;
688         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
689                         !mm_forbids_zeropage(vma->vm_mm) &&
690                         transparent_hugepage_use_zero_page()) {
691                 pgtable_t pgtable;
692                 struct page *zero_page;
693                 bool set;
694                 vm_fault_t ret;
695                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
696                 if (unlikely(!pgtable))
697                         return VM_FAULT_OOM;
698                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
699                 if (unlikely(!zero_page)) {
700                         pte_free(vma->vm_mm, pgtable);
701                         count_vm_event(THP_FAULT_FALLBACK);
702                         return VM_FAULT_FALLBACK;
703                 }
704                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
705                 ret = 0;
706                 set = false;
707                 if (pmd_none(*vmf->pmd)) {
708                         ret = check_stable_address_space(vma->vm_mm);
709                         if (ret) {
710                                 spin_unlock(vmf->ptl);
711                         } else if (userfaultfd_missing(vma)) {
712                                 spin_unlock(vmf->ptl);
713                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
714                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
715                         } else {
716                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
717                                                    haddr, vmf->pmd, zero_page);
718                                 spin_unlock(vmf->ptl);
719                                 set = true;
720                         }
721                 } else
722                         spin_unlock(vmf->ptl);
723                 if (!set)
724                         pte_free(vma->vm_mm, pgtable);
725                 return ret;
726         }
727         gfp = alloc_hugepage_direct_gfpmask(vma);
728         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
729         if (unlikely(!page)) {
730                 count_vm_event(THP_FAULT_FALLBACK);
731                 return VM_FAULT_FALLBACK;
732         }
733         prep_transhuge_page(page);
734         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
735 }
736
737 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
738                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
739                 pgtable_t pgtable)
740 {
741         struct mm_struct *mm = vma->vm_mm;
742         pmd_t entry;
743         spinlock_t *ptl;
744
745         ptl = pmd_lock(mm, pmd);
746         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
747         if (pfn_t_devmap(pfn))
748                 entry = pmd_mkdevmap(entry);
749         if (write) {
750                 entry = pmd_mkyoung(pmd_mkdirty(entry));
751                 entry = maybe_pmd_mkwrite(entry, vma);
752         }
753
754         if (pgtable) {
755                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
756                 mm_inc_nr_ptes(mm);
757         }
758
759         set_pmd_at(mm, addr, pmd, entry);
760         update_mmu_cache_pmd(vma, addr, pmd);
761         spin_unlock(ptl);
762 }
763
764 vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
765                         pmd_t *pmd, pfn_t pfn, bool write)
766 {
767         pgprot_t pgprot = vma->vm_page_prot;
768         pgtable_t pgtable = NULL;
769         /*
770          * If we had pmd_special, we could avoid all these restrictions,
771          * but we need to be consistent with PTEs and architectures that
772          * can't support a 'special' bit.
773          */
774         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
775                         !pfn_t_devmap(pfn));
776         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
777                                                 (VM_PFNMAP|VM_MIXEDMAP));
778         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
779
780         if (addr < vma->vm_start || addr >= vma->vm_end)
781                 return VM_FAULT_SIGBUS;
782
783         if (arch_needs_pgtable_deposit()) {
784                 pgtable = pte_alloc_one(vma->vm_mm, addr);
785                 if (!pgtable)
786                         return VM_FAULT_OOM;
787         }
788
789         track_pfn_insert(vma, &pgprot, pfn);
790
791         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
792         return VM_FAULT_NOPAGE;
793 }
794 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
795
796 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
797 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
798 {
799         if (likely(vma->vm_flags & VM_WRITE))
800                 pud = pud_mkwrite(pud);
801         return pud;
802 }
803
804 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
805                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
806 {
807         struct mm_struct *mm = vma->vm_mm;
808         pud_t entry;
809         spinlock_t *ptl;
810
811         ptl = pud_lock(mm, pud);
812         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
813         if (pfn_t_devmap(pfn))
814                 entry = pud_mkdevmap(entry);
815         if (write) {
816                 entry = pud_mkyoung(pud_mkdirty(entry));
817                 entry = maybe_pud_mkwrite(entry, vma);
818         }
819         set_pud_at(mm, addr, pud, entry);
820         update_mmu_cache_pud(vma, addr, pud);
821         spin_unlock(ptl);
822 }
823
824 vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
825                         pud_t *pud, pfn_t pfn, bool write)
826 {
827         pgprot_t pgprot = vma->vm_page_prot;
828         /*
829          * If we had pud_special, we could avoid all these restrictions,
830          * but we need to be consistent with PTEs and architectures that
831          * can't support a 'special' bit.
832          */
833         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
834                         !pfn_t_devmap(pfn));
835         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
836                                                 (VM_PFNMAP|VM_MIXEDMAP));
837         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
838
839         if (addr < vma->vm_start || addr >= vma->vm_end)
840                 return VM_FAULT_SIGBUS;
841
842         track_pfn_insert(vma, &pgprot, pfn);
843
844         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
845         return VM_FAULT_NOPAGE;
846 }
847 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
848 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
849
850 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
851                 pmd_t *pmd, int flags)
852 {
853         pmd_t _pmd;
854
855         _pmd = pmd_mkyoung(*pmd);
856         if (flags & FOLL_WRITE)
857                 _pmd = pmd_mkdirty(_pmd);
858         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
859                                 pmd, _pmd, flags & FOLL_WRITE))
860                 update_mmu_cache_pmd(vma, addr, pmd);
861 }
862
863 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
864                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
865 {
866         unsigned long pfn = pmd_pfn(*pmd);
867         struct mm_struct *mm = vma->vm_mm;
868         struct page *page;
869
870         assert_spin_locked(pmd_lockptr(mm, pmd));
871
872         /*
873          * When we COW a devmap PMD entry, we split it into PTEs, so we should
874          * not be in this function with `flags & FOLL_COW` set.
875          */
876         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
877
878         if (flags & FOLL_WRITE && !pmd_write(*pmd))
879                 return NULL;
880
881         if (pmd_present(*pmd) && pmd_devmap(*pmd))
882                 /* pass */;
883         else
884                 return NULL;
885
886         if (flags & FOLL_TOUCH)
887                 touch_pmd(vma, addr, pmd, flags);
888
889         /*
890          * device mapped pages can only be returned if the
891          * caller will manage the page reference count.
892          */
893         if (!(flags & FOLL_GET))
894                 return ERR_PTR(-EEXIST);
895
896         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
897         *pgmap = get_dev_pagemap(pfn, *pgmap);
898         if (!*pgmap)
899                 return ERR_PTR(-EFAULT);
900         page = pfn_to_page(pfn);
901         get_page(page);
902
903         return page;
904 }
905
906 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
907                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
908                   struct vm_area_struct *vma)
909 {
910         spinlock_t *dst_ptl, *src_ptl;
911         struct page *src_page;
912         pmd_t pmd;
913         pgtable_t pgtable = NULL;
914         int ret = -ENOMEM;
915
916         /* Skip if can be re-fill on fault */
917         if (!vma_is_anonymous(vma))
918                 return 0;
919
920         pgtable = pte_alloc_one(dst_mm, addr);
921         if (unlikely(!pgtable))
922                 goto out;
923
924         dst_ptl = pmd_lock(dst_mm, dst_pmd);
925         src_ptl = pmd_lockptr(src_mm, src_pmd);
926         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
927
928         ret = -EAGAIN;
929         pmd = *src_pmd;
930
931 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
932         if (unlikely(is_swap_pmd(pmd))) {
933                 swp_entry_t entry = pmd_to_swp_entry(pmd);
934
935                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
936                 if (is_write_migration_entry(entry)) {
937                         make_migration_entry_read(&entry);
938                         pmd = swp_entry_to_pmd(entry);
939                         if (pmd_swp_soft_dirty(*src_pmd))
940                                 pmd = pmd_swp_mksoft_dirty(pmd);
941                         set_pmd_at(src_mm, addr, src_pmd, pmd);
942                 }
943                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
944                 mm_inc_nr_ptes(dst_mm);
945                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
946                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
947                 ret = 0;
948                 goto out_unlock;
949         }
950 #endif
951
952         if (unlikely(!pmd_trans_huge(pmd))) {
953                 pte_free(dst_mm, pgtable);
954                 goto out_unlock;
955         }
956         /*
957          * When page table lock is held, the huge zero pmd should not be
958          * under splitting since we don't split the page itself, only pmd to
959          * a page table.
960          */
961         if (is_huge_zero_pmd(pmd)) {
962                 struct page *zero_page;
963                 /*
964                  * get_huge_zero_page() will never allocate a new page here,
965                  * since we already have a zero page to copy. It just takes a
966                  * reference.
967                  */
968                 zero_page = mm_get_huge_zero_page(dst_mm);
969                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
970                                 zero_page);
971                 ret = 0;
972                 goto out_unlock;
973         }
974
975         src_page = pmd_page(pmd);
976         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
977         get_page(src_page);
978         page_dup_rmap(src_page, true);
979         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
980         mm_inc_nr_ptes(dst_mm);
981         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
982
983         pmdp_set_wrprotect(src_mm, addr, src_pmd);
984         pmd = pmd_mkold(pmd_wrprotect(pmd));
985         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
986
987         ret = 0;
988 out_unlock:
989         spin_unlock(src_ptl);
990         spin_unlock(dst_ptl);
991 out:
992         return ret;
993 }
994
995 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
996 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
997                 pud_t *pud, int flags)
998 {
999         pud_t _pud;
1000
1001         _pud = pud_mkyoung(*pud);
1002         if (flags & FOLL_WRITE)
1003                 _pud = pud_mkdirty(_pud);
1004         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1005                                 pud, _pud, flags & FOLL_WRITE))
1006                 update_mmu_cache_pud(vma, addr, pud);
1007 }
1008
1009 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1010                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1011 {
1012         unsigned long pfn = pud_pfn(*pud);
1013         struct mm_struct *mm = vma->vm_mm;
1014         struct page *page;
1015
1016         assert_spin_locked(pud_lockptr(mm, pud));
1017
1018         if (flags & FOLL_WRITE && !pud_write(*pud))
1019                 return NULL;
1020
1021         if (pud_present(*pud) && pud_devmap(*pud))
1022                 /* pass */;
1023         else
1024                 return NULL;
1025
1026         if (flags & FOLL_TOUCH)
1027                 touch_pud(vma, addr, pud, flags);
1028
1029         /*
1030          * device mapped pages can only be returned if the
1031          * caller will manage the page reference count.
1032          */
1033         if (!(flags & FOLL_GET))
1034                 return ERR_PTR(-EEXIST);
1035
1036         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1037         *pgmap = get_dev_pagemap(pfn, *pgmap);
1038         if (!*pgmap)
1039                 return ERR_PTR(-EFAULT);
1040         page = pfn_to_page(pfn);
1041         get_page(page);
1042
1043         return page;
1044 }
1045
1046 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1047                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1048                   struct vm_area_struct *vma)
1049 {
1050         spinlock_t *dst_ptl, *src_ptl;
1051         pud_t pud;
1052         int ret;
1053
1054         dst_ptl = pud_lock(dst_mm, dst_pud);
1055         src_ptl = pud_lockptr(src_mm, src_pud);
1056         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1057
1058         ret = -EAGAIN;
1059         pud = *src_pud;
1060         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1061                 goto out_unlock;
1062
1063         /*
1064          * When page table lock is held, the huge zero pud should not be
1065          * under splitting since we don't split the page itself, only pud to
1066          * a page table.
1067          */
1068         if (is_huge_zero_pud(pud)) {
1069                 /* No huge zero pud yet */
1070         }
1071
1072         pudp_set_wrprotect(src_mm, addr, src_pud);
1073         pud = pud_mkold(pud_wrprotect(pud));
1074         set_pud_at(dst_mm, addr, dst_pud, pud);
1075
1076         ret = 0;
1077 out_unlock:
1078         spin_unlock(src_ptl);
1079         spin_unlock(dst_ptl);
1080         return ret;
1081 }
1082
1083 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1084 {
1085         pud_t entry;
1086         unsigned long haddr;
1087         bool write = vmf->flags & FAULT_FLAG_WRITE;
1088
1089         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1090         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1091                 goto unlock;
1092
1093         entry = pud_mkyoung(orig_pud);
1094         if (write)
1095                 entry = pud_mkdirty(entry);
1096         haddr = vmf->address & HPAGE_PUD_MASK;
1097         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1098                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1099
1100 unlock:
1101         spin_unlock(vmf->ptl);
1102 }
1103 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1104
1105 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1106 {
1107         pmd_t entry;
1108         unsigned long haddr;
1109         bool write = vmf->flags & FAULT_FLAG_WRITE;
1110
1111         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1112         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1113                 goto unlock;
1114
1115         entry = pmd_mkyoung(orig_pmd);
1116         if (write)
1117                 entry = pmd_mkdirty(entry);
1118         haddr = vmf->address & HPAGE_PMD_MASK;
1119         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1120                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1121
1122 unlock:
1123         spin_unlock(vmf->ptl);
1124 }
1125
1126 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1127                         pmd_t orig_pmd, struct page *page)
1128 {
1129         struct vm_area_struct *vma = vmf->vma;
1130         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1131         struct mem_cgroup *memcg;
1132         pgtable_t pgtable;
1133         pmd_t _pmd;
1134         int i;
1135         vm_fault_t ret = 0;
1136         struct page **pages;
1137         unsigned long mmun_start;       /* For mmu_notifiers */
1138         unsigned long mmun_end;         /* For mmu_notifiers */
1139
1140         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1141                               GFP_KERNEL);
1142         if (unlikely(!pages)) {
1143                 ret |= VM_FAULT_OOM;
1144                 goto out;
1145         }
1146
1147         for (i = 0; i < HPAGE_PMD_NR; i++) {
1148                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1149                                                vmf->address, page_to_nid(page));
1150                 if (unlikely(!pages[i] ||
1151                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1152                                      GFP_KERNEL, &memcg, false))) {
1153                         if (pages[i])
1154                                 put_page(pages[i]);
1155                         while (--i >= 0) {
1156                                 memcg = (void *)page_private(pages[i]);
1157                                 set_page_private(pages[i], 0);
1158                                 mem_cgroup_cancel_charge(pages[i], memcg,
1159                                                 false);
1160                                 put_page(pages[i]);
1161                         }
1162                         kfree(pages);
1163                         ret |= VM_FAULT_OOM;
1164                         goto out;
1165                 }
1166                 set_page_private(pages[i], (unsigned long)memcg);
1167         }
1168
1169         for (i = 0; i < HPAGE_PMD_NR; i++) {
1170                 copy_user_highpage(pages[i], page + i,
1171                                    haddr + PAGE_SIZE * i, vma);
1172                 __SetPageUptodate(pages[i]);
1173                 cond_resched();
1174         }
1175
1176         mmun_start = haddr;
1177         mmun_end   = haddr + HPAGE_PMD_SIZE;
1178         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1179
1180         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1181         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1182                 goto out_free_pages;
1183         VM_BUG_ON_PAGE(!PageHead(page), page);
1184
1185         /*
1186          * Leave pmd empty until pte is filled note we must notify here as
1187          * concurrent CPU thread might write to new page before the call to
1188          * mmu_notifier_invalidate_range_end() happens which can lead to a
1189          * device seeing memory write in different order than CPU.
1190          *
1191          * See Documentation/vm/mmu_notifier.rst
1192          */
1193         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1194
1195         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1196         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1197
1198         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1199                 pte_t entry;
1200                 entry = mk_pte(pages[i], vma->vm_page_prot);
1201                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1202                 memcg = (void *)page_private(pages[i]);
1203                 set_page_private(pages[i], 0);
1204                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1205                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1206                 lru_cache_add_active_or_unevictable(pages[i], vma);
1207                 vmf->pte = pte_offset_map(&_pmd, haddr);
1208                 VM_BUG_ON(!pte_none(*vmf->pte));
1209                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1210                 pte_unmap(vmf->pte);
1211         }
1212         kfree(pages);
1213
1214         smp_wmb(); /* make pte visible before pmd */
1215         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1216         page_remove_rmap(page, true);
1217         spin_unlock(vmf->ptl);
1218
1219         /*
1220          * No need to double call mmu_notifier->invalidate_range() callback as
1221          * the above pmdp_huge_clear_flush_notify() did already call it.
1222          */
1223         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1224                                                 mmun_end);
1225
1226         ret |= VM_FAULT_WRITE;
1227         put_page(page);
1228
1229 out:
1230         return ret;
1231
1232 out_free_pages:
1233         spin_unlock(vmf->ptl);
1234         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1235         for (i = 0; i < HPAGE_PMD_NR; i++) {
1236                 memcg = (void *)page_private(pages[i]);
1237                 set_page_private(pages[i], 0);
1238                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1239                 put_page(pages[i]);
1240         }
1241         kfree(pages);
1242         goto out;
1243 }
1244
1245 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1246 {
1247         struct vm_area_struct *vma = vmf->vma;
1248         struct page *page = NULL, *new_page;
1249         struct mem_cgroup *memcg;
1250         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1251         unsigned long mmun_start;       /* For mmu_notifiers */
1252         unsigned long mmun_end;         /* For mmu_notifiers */
1253         gfp_t huge_gfp;                 /* for allocation and charge */
1254         vm_fault_t ret = 0;
1255
1256         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1257         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1258         if (is_huge_zero_pmd(orig_pmd))
1259                 goto alloc;
1260         spin_lock(vmf->ptl);
1261         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1262                 goto out_unlock;
1263
1264         page = pmd_page(orig_pmd);
1265         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1266         /*
1267          * We can only reuse the page if nobody else maps the huge page or it's
1268          * part.
1269          */
1270         if (!trylock_page(page)) {
1271                 get_page(page);
1272                 spin_unlock(vmf->ptl);
1273                 lock_page(page);
1274                 spin_lock(vmf->ptl);
1275                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1276                         unlock_page(page);
1277                         put_page(page);
1278                         goto out_unlock;
1279                 }
1280                 put_page(page);
1281         }
1282         if (reuse_swap_page(page, NULL)) {
1283                 pmd_t entry;
1284                 entry = pmd_mkyoung(orig_pmd);
1285                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1286                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1287                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1288                 ret |= VM_FAULT_WRITE;
1289                 unlock_page(page);
1290                 goto out_unlock;
1291         }
1292         unlock_page(page);
1293         get_page(page);
1294         spin_unlock(vmf->ptl);
1295 alloc:
1296         if (transparent_hugepage_enabled(vma) &&
1297             !transparent_hugepage_debug_cow()) {
1298                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1299                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1300         } else
1301                 new_page = NULL;
1302
1303         if (likely(new_page)) {
1304                 prep_transhuge_page(new_page);
1305         } else {
1306                 if (!page) {
1307                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1308                         ret |= VM_FAULT_FALLBACK;
1309                 } else {
1310                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1311                         if (ret & VM_FAULT_OOM) {
1312                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1313                                 ret |= VM_FAULT_FALLBACK;
1314                         }
1315                         put_page(page);
1316                 }
1317                 count_vm_event(THP_FAULT_FALLBACK);
1318                 goto out;
1319         }
1320
1321         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1322                                         huge_gfp, &memcg, true))) {
1323                 put_page(new_page);
1324                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1325                 if (page)
1326                         put_page(page);
1327                 ret |= VM_FAULT_FALLBACK;
1328                 count_vm_event(THP_FAULT_FALLBACK);
1329                 goto out;
1330         }
1331
1332         count_vm_event(THP_FAULT_ALLOC);
1333
1334         if (!page)
1335                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1336         else
1337                 copy_user_huge_page(new_page, page, vmf->address,
1338                                     vma, HPAGE_PMD_NR);
1339         __SetPageUptodate(new_page);
1340
1341         mmun_start = haddr;
1342         mmun_end   = haddr + HPAGE_PMD_SIZE;
1343         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1344
1345         spin_lock(vmf->ptl);
1346         if (page)
1347                 put_page(page);
1348         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1349                 spin_unlock(vmf->ptl);
1350                 mem_cgroup_cancel_charge(new_page, memcg, true);
1351                 put_page(new_page);
1352                 goto out_mn;
1353         } else {
1354                 pmd_t entry;
1355                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1356                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1357                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1358                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1359                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1360                 lru_cache_add_active_or_unevictable(new_page, vma);
1361                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1362                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1363                 if (!page) {
1364                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1365                 } else {
1366                         VM_BUG_ON_PAGE(!PageHead(page), page);
1367                         page_remove_rmap(page, true);
1368                         put_page(page);
1369                 }
1370                 ret |= VM_FAULT_WRITE;
1371         }
1372         spin_unlock(vmf->ptl);
1373 out_mn:
1374         /*
1375          * No need to double call mmu_notifier->invalidate_range() callback as
1376          * the above pmdp_huge_clear_flush_notify() did already call it.
1377          */
1378         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1379                                                mmun_end);
1380 out:
1381         return ret;
1382 out_unlock:
1383         spin_unlock(vmf->ptl);
1384         return ret;
1385 }
1386
1387 /*
1388  * FOLL_FORCE can write to even unwritable pmd's, but only
1389  * after we've gone through a COW cycle and they are dirty.
1390  */
1391 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1392 {
1393         return pmd_write(pmd) ||
1394                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1395 }
1396
1397 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1398                                    unsigned long addr,
1399                                    pmd_t *pmd,
1400                                    unsigned int flags)
1401 {
1402         struct mm_struct *mm = vma->vm_mm;
1403         struct page *page = NULL;
1404
1405         assert_spin_locked(pmd_lockptr(mm, pmd));
1406
1407         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1408                 goto out;
1409
1410         /* Avoid dumping huge zero page */
1411         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1412                 return ERR_PTR(-EFAULT);
1413
1414         /* Full NUMA hinting faults to serialise migration in fault paths */
1415         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1416                 goto out;
1417
1418         page = pmd_page(*pmd);
1419         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1420         if (flags & FOLL_TOUCH)
1421                 touch_pmd(vma, addr, pmd, flags);
1422         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1423                 /*
1424                  * We don't mlock() pte-mapped THPs. This way we can avoid
1425                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1426                  *
1427                  * For anon THP:
1428                  *
1429                  * In most cases the pmd is the only mapping of the page as we
1430                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1431                  * writable private mappings in populate_vma_page_range().
1432                  *
1433                  * The only scenario when we have the page shared here is if we
1434                  * mlocking read-only mapping shared over fork(). We skip
1435                  * mlocking such pages.
1436                  *
1437                  * For file THP:
1438                  *
1439                  * We can expect PageDoubleMap() to be stable under page lock:
1440                  * for file pages we set it in page_add_file_rmap(), which
1441                  * requires page to be locked.
1442                  */
1443
1444                 if (PageAnon(page) && compound_mapcount(page) != 1)
1445                         goto skip_mlock;
1446                 if (PageDoubleMap(page) || !page->mapping)
1447                         goto skip_mlock;
1448                 if (!trylock_page(page))
1449                         goto skip_mlock;
1450                 lru_add_drain();
1451                 if (page->mapping && !PageDoubleMap(page))
1452                         mlock_vma_page(page);
1453                 unlock_page(page);
1454         }
1455 skip_mlock:
1456         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1457         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1458         if (flags & FOLL_GET)
1459                 get_page(page);
1460
1461 out:
1462         return page;
1463 }
1464
1465 /* NUMA hinting page fault entry point for trans huge pmds */
1466 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1467 {
1468         struct vm_area_struct *vma = vmf->vma;
1469         struct anon_vma *anon_vma = NULL;
1470         struct page *page;
1471         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1472         int page_nid = -1, this_nid = numa_node_id();
1473         int target_nid, last_cpupid = -1;
1474         bool page_locked;
1475         bool migrated = false;
1476         bool was_writable;
1477         int flags = 0;
1478
1479         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1480         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1481                 goto out_unlock;
1482
1483         /*
1484          * If there are potential migrations, wait for completion and retry
1485          * without disrupting NUMA hinting information. Do not relock and
1486          * check_same as the page may no longer be mapped.
1487          */
1488         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1489                 page = pmd_page(*vmf->pmd);
1490                 if (!get_page_unless_zero(page))
1491                         goto out_unlock;
1492                 spin_unlock(vmf->ptl);
1493                 put_and_wait_on_page_locked(page);
1494                 goto out;
1495         }
1496
1497         page = pmd_page(pmd);
1498         BUG_ON(is_huge_zero_page(page));
1499         page_nid = page_to_nid(page);
1500         last_cpupid = page_cpupid_last(page);
1501         count_vm_numa_event(NUMA_HINT_FAULTS);
1502         if (page_nid == this_nid) {
1503                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1504                 flags |= TNF_FAULT_LOCAL;
1505         }
1506
1507         /* See similar comment in do_numa_page for explanation */
1508         if (!pmd_savedwrite(pmd))
1509                 flags |= TNF_NO_GROUP;
1510
1511         /*
1512          * Acquire the page lock to serialise THP migrations but avoid dropping
1513          * page_table_lock if at all possible
1514          */
1515         page_locked = trylock_page(page);
1516         target_nid = mpol_misplaced(page, vma, haddr);
1517         if (target_nid == -1) {
1518                 /* If the page was locked, there are no parallel migrations */
1519                 if (page_locked)
1520                         goto clear_pmdnuma;
1521         }
1522
1523         /* Migration could have started since the pmd_trans_migrating check */
1524         if (!page_locked) {
1525                 page_nid = -1;
1526                 if (!get_page_unless_zero(page))
1527                         goto out_unlock;
1528                 spin_unlock(vmf->ptl);
1529                 put_and_wait_on_page_locked(page);
1530                 goto out;
1531         }
1532
1533         /*
1534          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1535          * to serialises splits
1536          */
1537         get_page(page);
1538         spin_unlock(vmf->ptl);
1539         anon_vma = page_lock_anon_vma_read(page);
1540
1541         /* Confirm the PMD did not change while page_table_lock was released */
1542         spin_lock(vmf->ptl);
1543         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1544                 unlock_page(page);
1545                 put_page(page);
1546                 page_nid = -1;
1547                 goto out_unlock;
1548         }
1549
1550         /* Bail if we fail to protect against THP splits for any reason */
1551         if (unlikely(!anon_vma)) {
1552                 put_page(page);
1553                 page_nid = -1;
1554                 goto clear_pmdnuma;
1555         }
1556
1557         /*
1558          * Since we took the NUMA fault, we must have observed the !accessible
1559          * bit. Make sure all other CPUs agree with that, to avoid them
1560          * modifying the page we're about to migrate.
1561          *
1562          * Must be done under PTL such that we'll observe the relevant
1563          * inc_tlb_flush_pending().
1564          *
1565          * We are not sure a pending tlb flush here is for a huge page
1566          * mapping or not. Hence use the tlb range variant
1567          */
1568         if (mm_tlb_flush_pending(vma->vm_mm)) {
1569                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1570                 /*
1571                  * change_huge_pmd() released the pmd lock before
1572                  * invalidating the secondary MMUs sharing the primary
1573                  * MMU pagetables (with ->invalidate_range()). The
1574                  * mmu_notifier_invalidate_range_end() (which
1575                  * internally calls ->invalidate_range()) in
1576                  * change_pmd_range() will run after us, so we can't
1577                  * rely on it here and we need an explicit invalidate.
1578                  */
1579                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1580                                               haddr + HPAGE_PMD_SIZE);
1581         }
1582
1583         /*
1584          * Migrate the THP to the requested node, returns with page unlocked
1585          * and access rights restored.
1586          */
1587         spin_unlock(vmf->ptl);
1588
1589         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1590                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1591         if (migrated) {
1592                 flags |= TNF_MIGRATED;
1593                 page_nid = target_nid;
1594         } else
1595                 flags |= TNF_MIGRATE_FAIL;
1596
1597         goto out;
1598 clear_pmdnuma:
1599         BUG_ON(!PageLocked(page));
1600         was_writable = pmd_savedwrite(pmd);
1601         pmd = pmd_modify(pmd, vma->vm_page_prot);
1602         pmd = pmd_mkyoung(pmd);
1603         if (was_writable)
1604                 pmd = pmd_mkwrite(pmd);
1605         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1606         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1607         unlock_page(page);
1608 out_unlock:
1609         spin_unlock(vmf->ptl);
1610
1611 out:
1612         if (anon_vma)
1613                 page_unlock_anon_vma_read(anon_vma);
1614
1615         if (page_nid != -1)
1616                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1617                                 flags);
1618
1619         return 0;
1620 }
1621
1622 /*
1623  * Return true if we do MADV_FREE successfully on entire pmd page.
1624  * Otherwise, return false.
1625  */
1626 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1627                 pmd_t *pmd, unsigned long addr, unsigned long next)
1628 {
1629         spinlock_t *ptl;
1630         pmd_t orig_pmd;
1631         struct page *page;
1632         struct mm_struct *mm = tlb->mm;
1633         bool ret = false;
1634
1635         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1636
1637         ptl = pmd_trans_huge_lock(pmd, vma);
1638         if (!ptl)
1639                 goto out_unlocked;
1640
1641         orig_pmd = *pmd;
1642         if (is_huge_zero_pmd(orig_pmd))
1643                 goto out;
1644
1645         if (unlikely(!pmd_present(orig_pmd))) {
1646                 VM_BUG_ON(thp_migration_supported() &&
1647                                   !is_pmd_migration_entry(orig_pmd));
1648                 goto out;
1649         }
1650
1651         page = pmd_page(orig_pmd);
1652         /*
1653          * If other processes are mapping this page, we couldn't discard
1654          * the page unless they all do MADV_FREE so let's skip the page.
1655          */
1656         if (page_mapcount(page) != 1)
1657                 goto out;
1658
1659         if (!trylock_page(page))
1660                 goto out;
1661
1662         /*
1663          * If user want to discard part-pages of THP, split it so MADV_FREE
1664          * will deactivate only them.
1665          */
1666         if (next - addr != HPAGE_PMD_SIZE) {
1667                 get_page(page);
1668                 spin_unlock(ptl);
1669                 split_huge_page(page);
1670                 unlock_page(page);
1671                 put_page(page);
1672                 goto out_unlocked;
1673         }
1674
1675         if (PageDirty(page))
1676                 ClearPageDirty(page);
1677         unlock_page(page);
1678
1679         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1680                 pmdp_invalidate(vma, addr, pmd);
1681                 orig_pmd = pmd_mkold(orig_pmd);
1682                 orig_pmd = pmd_mkclean(orig_pmd);
1683
1684                 set_pmd_at(mm, addr, pmd, orig_pmd);
1685                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1686         }
1687
1688         mark_page_lazyfree(page);
1689         ret = true;
1690 out:
1691         spin_unlock(ptl);
1692 out_unlocked:
1693         return ret;
1694 }
1695
1696 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1697 {
1698         pgtable_t pgtable;
1699
1700         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1701         pte_free(mm, pgtable);
1702         mm_dec_nr_ptes(mm);
1703 }
1704
1705 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1706                  pmd_t *pmd, unsigned long addr)
1707 {
1708         pmd_t orig_pmd;
1709         spinlock_t *ptl;
1710
1711         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1712
1713         ptl = __pmd_trans_huge_lock(pmd, vma);
1714         if (!ptl)
1715                 return 0;
1716         /*
1717          * For architectures like ppc64 we look at deposited pgtable
1718          * when calling pmdp_huge_get_and_clear. So do the
1719          * pgtable_trans_huge_withdraw after finishing pmdp related
1720          * operations.
1721          */
1722         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1723                         tlb->fullmm);
1724         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1725         if (vma_is_dax(vma)) {
1726                 if (arch_needs_pgtable_deposit())
1727                         zap_deposited_table(tlb->mm, pmd);
1728                 spin_unlock(ptl);
1729                 if (is_huge_zero_pmd(orig_pmd))
1730                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1731         } else if (is_huge_zero_pmd(orig_pmd)) {
1732                 zap_deposited_table(tlb->mm, pmd);
1733                 spin_unlock(ptl);
1734                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1735         } else {
1736                 struct page *page = NULL;
1737                 int flush_needed = 1;
1738
1739                 if (pmd_present(orig_pmd)) {
1740                         page = pmd_page(orig_pmd);
1741                         page_remove_rmap(page, true);
1742                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1743                         VM_BUG_ON_PAGE(!PageHead(page), page);
1744                 } else if (thp_migration_supported()) {
1745                         swp_entry_t entry;
1746
1747                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1748                         entry = pmd_to_swp_entry(orig_pmd);
1749                         page = pfn_to_page(swp_offset(entry));
1750                         flush_needed = 0;
1751                 } else
1752                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1753
1754                 if (PageAnon(page)) {
1755                         zap_deposited_table(tlb->mm, pmd);
1756                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1757                 } else {
1758                         if (arch_needs_pgtable_deposit())
1759                                 zap_deposited_table(tlb->mm, pmd);
1760                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1761                 }
1762
1763                 spin_unlock(ptl);
1764                 if (flush_needed)
1765                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1766         }
1767         return 1;
1768 }
1769
1770 #ifndef pmd_move_must_withdraw
1771 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1772                                          spinlock_t *old_pmd_ptl,
1773                                          struct vm_area_struct *vma)
1774 {
1775         /*
1776          * With split pmd lock we also need to move preallocated
1777          * PTE page table if new_pmd is on different PMD page table.
1778          *
1779          * We also don't deposit and withdraw tables for file pages.
1780          */
1781         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1782 }
1783 #endif
1784
1785 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1786 {
1787 #ifdef CONFIG_MEM_SOFT_DIRTY
1788         if (unlikely(is_pmd_migration_entry(pmd)))
1789                 pmd = pmd_swp_mksoft_dirty(pmd);
1790         else if (pmd_present(pmd))
1791                 pmd = pmd_mksoft_dirty(pmd);
1792 #endif
1793         return pmd;
1794 }
1795
1796 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1797                   unsigned long new_addr, unsigned long old_end,
1798                   pmd_t *old_pmd, pmd_t *new_pmd)
1799 {
1800         spinlock_t *old_ptl, *new_ptl;
1801         pmd_t pmd;
1802         struct mm_struct *mm = vma->vm_mm;
1803         bool force_flush = false;
1804
1805         if ((old_addr & ~HPAGE_PMD_MASK) ||
1806             (new_addr & ~HPAGE_PMD_MASK) ||
1807             old_end - old_addr < HPAGE_PMD_SIZE)
1808                 return false;
1809
1810         /*
1811          * The destination pmd shouldn't be established, free_pgtables()
1812          * should have release it.
1813          */
1814         if (WARN_ON(!pmd_none(*new_pmd))) {
1815                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1816                 return false;
1817         }
1818
1819         /*
1820          * We don't have to worry about the ordering of src and dst
1821          * ptlocks because exclusive mmap_sem prevents deadlock.
1822          */
1823         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1824         if (old_ptl) {
1825                 new_ptl = pmd_lockptr(mm, new_pmd);
1826                 if (new_ptl != old_ptl)
1827                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1828                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1829                 if (pmd_present(pmd))
1830                         force_flush = true;
1831                 VM_BUG_ON(!pmd_none(*new_pmd));
1832
1833                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1834                         pgtable_t pgtable;
1835                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1836                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1837                 }
1838                 pmd = move_soft_dirty_pmd(pmd);
1839                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1840                 if (force_flush)
1841                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1842                 if (new_ptl != old_ptl)
1843                         spin_unlock(new_ptl);
1844                 spin_unlock(old_ptl);
1845                 return true;
1846         }
1847         return false;
1848 }
1849
1850 /*
1851  * Returns
1852  *  - 0 if PMD could not be locked
1853  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1854  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1855  */
1856 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1857                 unsigned long addr, pgprot_t newprot, int prot_numa)
1858 {
1859         struct mm_struct *mm = vma->vm_mm;
1860         spinlock_t *ptl;
1861         pmd_t entry;
1862         bool preserve_write;
1863         int ret;
1864
1865         ptl = __pmd_trans_huge_lock(pmd, vma);
1866         if (!ptl)
1867                 return 0;
1868
1869         preserve_write = prot_numa && pmd_write(*pmd);
1870         ret = 1;
1871
1872 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1873         if (is_swap_pmd(*pmd)) {
1874                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1875
1876                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1877                 if (is_write_migration_entry(entry)) {
1878                         pmd_t newpmd;
1879                         /*
1880                          * A protection check is difficult so
1881                          * just be safe and disable write
1882                          */
1883                         make_migration_entry_read(&entry);
1884                         newpmd = swp_entry_to_pmd(entry);
1885                         if (pmd_swp_soft_dirty(*pmd))
1886                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1887                         set_pmd_at(mm, addr, pmd, newpmd);
1888                 }
1889                 goto unlock;
1890         }
1891 #endif
1892
1893         /*
1894          * Avoid trapping faults against the zero page. The read-only
1895          * data is likely to be read-cached on the local CPU and
1896          * local/remote hits to the zero page are not interesting.
1897          */
1898         if (prot_numa && is_huge_zero_pmd(*pmd))
1899                 goto unlock;
1900
1901         if (prot_numa && pmd_protnone(*pmd))
1902                 goto unlock;
1903
1904         /*
1905          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1906          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1907          * which is also under down_read(mmap_sem):
1908          *
1909          *      CPU0:                           CPU1:
1910          *                              change_huge_pmd(prot_numa=1)
1911          *                               pmdp_huge_get_and_clear_notify()
1912          * madvise_dontneed()
1913          *  zap_pmd_range()
1914          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1915          *   // skip the pmd
1916          *                               set_pmd_at();
1917          *                               // pmd is re-established
1918          *
1919          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1920          * which may break userspace.
1921          *
1922          * pmdp_invalidate() is required to make sure we don't miss
1923          * dirty/young flags set by hardware.
1924          */
1925         entry = pmdp_invalidate(vma, addr, pmd);
1926
1927         entry = pmd_modify(entry, newprot);
1928         if (preserve_write)
1929                 entry = pmd_mk_savedwrite(entry);
1930         ret = HPAGE_PMD_NR;
1931         set_pmd_at(mm, addr, pmd, entry);
1932         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1933 unlock:
1934         spin_unlock(ptl);
1935         return ret;
1936 }
1937
1938 /*
1939  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1940  *
1941  * Note that if it returns page table lock pointer, this routine returns without
1942  * unlocking page table lock. So callers must unlock it.
1943  */
1944 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1945 {
1946         spinlock_t *ptl;
1947         ptl = pmd_lock(vma->vm_mm, pmd);
1948         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1949                         pmd_devmap(*pmd)))
1950                 return ptl;
1951         spin_unlock(ptl);
1952         return NULL;
1953 }
1954
1955 /*
1956  * Returns true if a given pud maps a thp, false otherwise.
1957  *
1958  * Note that if it returns true, this routine returns without unlocking page
1959  * table lock. So callers must unlock it.
1960  */
1961 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1962 {
1963         spinlock_t *ptl;
1964
1965         ptl = pud_lock(vma->vm_mm, pud);
1966         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1967                 return ptl;
1968         spin_unlock(ptl);
1969         return NULL;
1970 }
1971
1972 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1973 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1974                  pud_t *pud, unsigned long addr)
1975 {
1976         pud_t orig_pud;
1977         spinlock_t *ptl;
1978
1979         ptl = __pud_trans_huge_lock(pud, vma);
1980         if (!ptl)
1981                 return 0;
1982         /*
1983          * For architectures like ppc64 we look at deposited pgtable
1984          * when calling pudp_huge_get_and_clear. So do the
1985          * pgtable_trans_huge_withdraw after finishing pudp related
1986          * operations.
1987          */
1988         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1989                         tlb->fullmm);
1990         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1991         if (vma_is_dax(vma)) {
1992                 spin_unlock(ptl);
1993                 /* No zero page support yet */
1994         } else {
1995                 /* No support for anonymous PUD pages yet */
1996                 BUG();
1997         }
1998         return 1;
1999 }
2000
2001 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2002                 unsigned long haddr)
2003 {
2004         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2005         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2006         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2007         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2008
2009         count_vm_event(THP_SPLIT_PUD);
2010
2011         pudp_huge_clear_flush_notify(vma, haddr, pud);
2012 }
2013
2014 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2015                 unsigned long address)
2016 {
2017         spinlock_t *ptl;
2018         struct mm_struct *mm = vma->vm_mm;
2019         unsigned long haddr = address & HPAGE_PUD_MASK;
2020
2021         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2022         ptl = pud_lock(mm, pud);
2023         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2024                 goto out;
2025         __split_huge_pud_locked(vma, pud, haddr);
2026
2027 out:
2028         spin_unlock(ptl);
2029         /*
2030          * No need to double call mmu_notifier->invalidate_range() callback as
2031          * the above pudp_huge_clear_flush_notify() did already call it.
2032          */
2033         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2034                                                HPAGE_PUD_SIZE);
2035 }
2036 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2037
2038 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2039                 unsigned long haddr, pmd_t *pmd)
2040 {
2041         struct mm_struct *mm = vma->vm_mm;
2042         pgtable_t pgtable;
2043         pmd_t _pmd;
2044         int i;
2045
2046         /*
2047          * Leave pmd empty until pte is filled note that it is fine to delay
2048          * notification until mmu_notifier_invalidate_range_end() as we are
2049          * replacing a zero pmd write protected page with a zero pte write
2050          * protected page.
2051          *
2052          * See Documentation/vm/mmu_notifier.rst
2053          */
2054         pmdp_huge_clear_flush(vma, haddr, pmd);
2055
2056         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2057         pmd_populate(mm, &_pmd, pgtable);
2058
2059         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2060                 pte_t *pte, entry;
2061                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2062                 entry = pte_mkspecial(entry);
2063                 pte = pte_offset_map(&_pmd, haddr);
2064                 VM_BUG_ON(!pte_none(*pte));
2065                 set_pte_at(mm, haddr, pte, entry);
2066                 pte_unmap(pte);
2067         }
2068         smp_wmb(); /* make pte visible before pmd */
2069         pmd_populate(mm, pmd, pgtable);
2070 }
2071
2072 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2073                 unsigned long haddr, bool freeze)
2074 {
2075         struct mm_struct *mm = vma->vm_mm;
2076         struct page *page;
2077         pgtable_t pgtable;
2078         pmd_t old_pmd, _pmd;
2079         bool young, write, soft_dirty, pmd_migration = false;
2080         unsigned long addr;
2081         int i;
2082
2083         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2084         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2085         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2086         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2087                                 && !pmd_devmap(*pmd));
2088
2089         count_vm_event(THP_SPLIT_PMD);
2090
2091         if (!vma_is_anonymous(vma)) {
2092                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2093                 /*
2094                  * We are going to unmap this huge page. So
2095                  * just go ahead and zap it
2096                  */
2097                 if (arch_needs_pgtable_deposit())
2098                         zap_deposited_table(mm, pmd);
2099                 if (vma_is_dax(vma))
2100                         return;
2101                 page = pmd_page(_pmd);
2102                 if (!PageDirty(page) && pmd_dirty(_pmd))
2103                         set_page_dirty(page);
2104                 if (!PageReferenced(page) && pmd_young(_pmd))
2105                         SetPageReferenced(page);
2106                 page_remove_rmap(page, true);
2107                 put_page(page);
2108                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2109                 return;
2110         } else if (is_huge_zero_pmd(*pmd)) {
2111                 /*
2112                  * FIXME: Do we want to invalidate secondary mmu by calling
2113                  * mmu_notifier_invalidate_range() see comments below inside
2114                  * __split_huge_pmd() ?
2115                  *
2116                  * We are going from a zero huge page write protected to zero
2117                  * small page also write protected so it does not seems useful
2118                  * to invalidate secondary mmu at this time.
2119                  */
2120                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2121         }
2122
2123         /*
2124          * Up to this point the pmd is present and huge and userland has the
2125          * whole access to the hugepage during the split (which happens in
2126          * place). If we overwrite the pmd with the not-huge version pointing
2127          * to the pte here (which of course we could if all CPUs were bug
2128          * free), userland could trigger a small page size TLB miss on the
2129          * small sized TLB while the hugepage TLB entry is still established in
2130          * the huge TLB. Some CPU doesn't like that.
2131          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2132          * 383 on page 93. Intel should be safe but is also warns that it's
2133          * only safe if the permission and cache attributes of the two entries
2134          * loaded in the two TLB is identical (which should be the case here).
2135          * But it is generally safer to never allow small and huge TLB entries
2136          * for the same virtual address to be loaded simultaneously. So instead
2137          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2138          * current pmd notpresent (atomically because here the pmd_trans_huge
2139          * must remain set at all times on the pmd until the split is complete
2140          * for this pmd), then we flush the SMP TLB and finally we write the
2141          * non-huge version of the pmd entry with pmd_populate.
2142          */
2143         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2144
2145         pmd_migration = is_pmd_migration_entry(old_pmd);
2146         if (unlikely(pmd_migration)) {
2147                 swp_entry_t entry;
2148
2149                 entry = pmd_to_swp_entry(old_pmd);
2150                 page = pfn_to_page(swp_offset(entry));
2151                 write = is_write_migration_entry(entry);
2152                 young = false;
2153                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2154         } else {
2155                 page = pmd_page(old_pmd);
2156                 if (pmd_dirty(old_pmd))
2157                         SetPageDirty(page);
2158                 write = pmd_write(old_pmd);
2159                 young = pmd_young(old_pmd);
2160                 soft_dirty = pmd_soft_dirty(old_pmd);
2161         }
2162         VM_BUG_ON_PAGE(!page_count(page), page);
2163         page_ref_add(page, HPAGE_PMD_NR - 1);
2164
2165         /*
2166          * Withdraw the table only after we mark the pmd entry invalid.
2167          * This's critical for some architectures (Power).
2168          */
2169         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2170         pmd_populate(mm, &_pmd, pgtable);
2171
2172         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2173                 pte_t entry, *pte;
2174                 /*
2175                  * Note that NUMA hinting access restrictions are not
2176                  * transferred to avoid any possibility of altering
2177                  * permissions across VMAs.
2178                  */
2179                 if (freeze || pmd_migration) {
2180                         swp_entry_t swp_entry;
2181                         swp_entry = make_migration_entry(page + i, write);
2182                         entry = swp_entry_to_pte(swp_entry);
2183                         if (soft_dirty)
2184                                 entry = pte_swp_mksoft_dirty(entry);
2185                 } else {
2186                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2187                         entry = maybe_mkwrite(entry, vma);
2188                         if (!write)
2189                                 entry = pte_wrprotect(entry);
2190                         if (!young)
2191                                 entry = pte_mkold(entry);
2192                         if (soft_dirty)
2193                                 entry = pte_mksoft_dirty(entry);
2194                 }
2195                 pte = pte_offset_map(&_pmd, addr);
2196                 BUG_ON(!pte_none(*pte));
2197                 set_pte_at(mm, addr, pte, entry);
2198                 atomic_inc(&page[i]._mapcount);
2199                 pte_unmap(pte);
2200         }
2201
2202         /*
2203          * Set PG_double_map before dropping compound_mapcount to avoid
2204          * false-negative page_mapped().
2205          */
2206         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2207                 for (i = 0; i < HPAGE_PMD_NR; i++)
2208                         atomic_inc(&page[i]._mapcount);
2209         }
2210
2211         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2212                 /* Last compound_mapcount is gone. */
2213                 __dec_node_page_state(page, NR_ANON_THPS);
2214                 if (TestClearPageDoubleMap(page)) {
2215                         /* No need in mapcount reference anymore */
2216                         for (i = 0; i < HPAGE_PMD_NR; i++)
2217                                 atomic_dec(&page[i]._mapcount);
2218                 }
2219         }
2220
2221         smp_wmb(); /* make pte visible before pmd */
2222         pmd_populate(mm, pmd, pgtable);
2223
2224         if (freeze) {
2225                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2226                         page_remove_rmap(page + i, false);
2227                         put_page(page + i);
2228                 }
2229         }
2230 }
2231
2232 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2233                 unsigned long address, bool freeze, struct page *page)
2234 {
2235         spinlock_t *ptl;
2236         struct mm_struct *mm = vma->vm_mm;
2237         unsigned long haddr = address & HPAGE_PMD_MASK;
2238
2239         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2240         ptl = pmd_lock(mm, pmd);
2241
2242         /*
2243          * If caller asks to setup a migration entries, we need a page to check
2244          * pmd against. Otherwise we can end up replacing wrong page.
2245          */
2246         VM_BUG_ON(freeze && !page);
2247         if (page && page != pmd_page(*pmd))
2248                 goto out;
2249
2250         if (pmd_trans_huge(*pmd)) {
2251                 page = pmd_page(*pmd);
2252                 if (PageMlocked(page))
2253                         clear_page_mlock(page);
2254         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2255                 goto out;
2256         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2257 out:
2258         spin_unlock(ptl);
2259         /*
2260          * No need to double call mmu_notifier->invalidate_range() callback.
2261          * They are 3 cases to consider inside __split_huge_pmd_locked():
2262          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2263          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2264          *    fault will trigger a flush_notify before pointing to a new page
2265          *    (it is fine if the secondary mmu keeps pointing to the old zero
2266          *    page in the meantime)
2267          *  3) Split a huge pmd into pte pointing to the same page. No need
2268          *     to invalidate secondary tlb entry they are all still valid.
2269          *     any further changes to individual pte will notify. So no need
2270          *     to call mmu_notifier->invalidate_range()
2271          */
2272         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2273                                                HPAGE_PMD_SIZE);
2274 }
2275
2276 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2277                 bool freeze, struct page *page)
2278 {
2279         pgd_t *pgd;
2280         p4d_t *p4d;
2281         pud_t *pud;
2282         pmd_t *pmd;
2283
2284         pgd = pgd_offset(vma->vm_mm, address);
2285         if (!pgd_present(*pgd))
2286                 return;
2287
2288         p4d = p4d_offset(pgd, address);
2289         if (!p4d_present(*p4d))
2290                 return;
2291
2292         pud = pud_offset(p4d, address);
2293         if (!pud_present(*pud))
2294                 return;
2295
2296         pmd = pmd_offset(pud, address);
2297
2298         __split_huge_pmd(vma, pmd, address, freeze, page);
2299 }
2300
2301 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2302                              unsigned long start,
2303                              unsigned long end,
2304                              long adjust_next)
2305 {
2306         /*
2307          * If the new start address isn't hpage aligned and it could
2308          * previously contain an hugepage: check if we need to split
2309          * an huge pmd.
2310          */
2311         if (start & ~HPAGE_PMD_MASK &&
2312             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2313             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2314                 split_huge_pmd_address(vma, start, false, NULL);
2315
2316         /*
2317          * If the new end address isn't hpage aligned and it could
2318          * previously contain an hugepage: check if we need to split
2319          * an huge pmd.
2320          */
2321         if (end & ~HPAGE_PMD_MASK &&
2322             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2323             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2324                 split_huge_pmd_address(vma, end, false, NULL);
2325
2326         /*
2327          * If we're also updating the vma->vm_next->vm_start, if the new
2328          * vm_next->vm_start isn't page aligned and it could previously
2329          * contain an hugepage: check if we need to split an huge pmd.
2330          */
2331         if (adjust_next > 0) {
2332                 struct vm_area_struct *next = vma->vm_next;
2333                 unsigned long nstart = next->vm_start;
2334                 nstart += adjust_next << PAGE_SHIFT;
2335                 if (nstart & ~HPAGE_PMD_MASK &&
2336                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2337                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2338                         split_huge_pmd_address(next, nstart, false, NULL);
2339         }
2340 }
2341
2342 static void unmap_page(struct page *page)
2343 {
2344         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2345                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2346         bool unmap_success;
2347
2348         VM_BUG_ON_PAGE(!PageHead(page), page);
2349
2350         if (PageAnon(page))
2351                 ttu_flags |= TTU_SPLIT_FREEZE;
2352
2353         unmap_success = try_to_unmap(page, ttu_flags);
2354         VM_BUG_ON_PAGE(!unmap_success, page);
2355 }
2356
2357 static void remap_page(struct page *page)
2358 {
2359         int i;
2360         if (PageTransHuge(page)) {
2361                 remove_migration_ptes(page, page, true);
2362         } else {
2363                 for (i = 0; i < HPAGE_PMD_NR; i++)
2364                         remove_migration_ptes(page + i, page + i, true);
2365         }
2366 }
2367
2368 static void __split_huge_page_tail(struct page *head, int tail,
2369                 struct lruvec *lruvec, struct list_head *list)
2370 {
2371         struct page *page_tail = head + tail;
2372
2373         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2374
2375         /*
2376          * Clone page flags before unfreezing refcount.
2377          *
2378          * After successful get_page_unless_zero() might follow flags change,
2379          * for exmaple lock_page() which set PG_waiters.
2380          */
2381         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2382         page_tail->flags |= (head->flags &
2383                         ((1L << PG_referenced) |
2384                          (1L << PG_swapbacked) |
2385                          (1L << PG_swapcache) |
2386                          (1L << PG_mlocked) |
2387                          (1L << PG_uptodate) |
2388                          (1L << PG_active) |
2389                          (1L << PG_workingset) |
2390                          (1L << PG_locked) |
2391                          (1L << PG_unevictable) |
2392                          (1L << PG_dirty)));
2393
2394         /* ->mapping in first tail page is compound_mapcount */
2395         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2396                         page_tail);
2397         page_tail->mapping = head->mapping;
2398         page_tail->index = head->index + tail;
2399
2400         /* Page flags must be visible before we make the page non-compound. */
2401         smp_wmb();
2402
2403         /*
2404          * Clear PageTail before unfreezing page refcount.
2405          *
2406          * After successful get_page_unless_zero() might follow put_page()
2407          * which needs correct compound_head().
2408          */
2409         clear_compound_head(page_tail);
2410
2411         /* Finally unfreeze refcount. Additional reference from page cache. */
2412         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2413                                           PageSwapCache(head)));
2414
2415         if (page_is_young(head))
2416                 set_page_young(page_tail);
2417         if (page_is_idle(head))
2418                 set_page_idle(page_tail);
2419
2420         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2421
2422         /*
2423          * always add to the tail because some iterators expect new
2424          * pages to show after the currently processed elements - e.g.
2425          * migrate_pages
2426          */
2427         lru_add_page_tail(head, page_tail, lruvec, list);
2428 }
2429
2430 static void __split_huge_page(struct page *page, struct list_head *list,
2431                 pgoff_t end, unsigned long flags)
2432 {
2433         struct page *head = compound_head(page);
2434         struct zone *zone = page_zone(head);
2435         struct lruvec *lruvec;
2436         int i;
2437
2438         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2439
2440         /* complete memcg works before add pages to LRU */
2441         mem_cgroup_split_huge_fixup(head);
2442
2443         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2444                 __split_huge_page_tail(head, i, lruvec, list);
2445                 /* Some pages can be beyond i_size: drop them from page cache */
2446                 if (head[i].index >= end) {
2447                         ClearPageDirty(head + i);
2448                         __delete_from_page_cache(head + i, NULL);
2449                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2450                                 shmem_uncharge(head->mapping->host, 1);
2451                         put_page(head + i);
2452                 }
2453         }
2454
2455         ClearPageCompound(head);
2456         /* See comment in __split_huge_page_tail() */
2457         if (PageAnon(head)) {
2458                 /* Additional pin to swap cache */
2459                 if (PageSwapCache(head))
2460                         page_ref_add(head, 2);
2461                 else
2462                         page_ref_inc(head);
2463         } else {
2464                 /* Additional pin to page cache */
2465                 page_ref_add(head, 2);
2466                 xa_unlock(&head->mapping->i_pages);
2467         }
2468
2469         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2470
2471         remap_page(head);
2472
2473         for (i = 0; i < HPAGE_PMD_NR; i++) {
2474                 struct page *subpage = head + i;
2475                 if (subpage == page)
2476                         continue;
2477                 unlock_page(subpage);
2478
2479                 /*
2480                  * Subpages may be freed if there wasn't any mapping
2481                  * like if add_to_swap() is running on a lru page that
2482                  * had its mapping zapped. And freeing these pages
2483                  * requires taking the lru_lock so we do the put_page
2484                  * of the tail pages after the split is complete.
2485                  */
2486                 put_page(subpage);
2487         }
2488 }
2489
2490 int total_mapcount(struct page *page)
2491 {
2492         int i, compound, ret;
2493
2494         VM_BUG_ON_PAGE(PageTail(page), page);
2495
2496         if (likely(!PageCompound(page)))
2497                 return atomic_read(&page->_mapcount) + 1;
2498
2499         compound = compound_mapcount(page);
2500         if (PageHuge(page))
2501                 return compound;
2502         ret = compound;
2503         for (i = 0; i < HPAGE_PMD_NR; i++)
2504                 ret += atomic_read(&page[i]._mapcount) + 1;
2505         /* File pages has compound_mapcount included in _mapcount */
2506         if (!PageAnon(page))
2507                 return ret - compound * HPAGE_PMD_NR;
2508         if (PageDoubleMap(page))
2509                 ret -= HPAGE_PMD_NR;
2510         return ret;
2511 }
2512
2513 /*
2514  * This calculates accurately how many mappings a transparent hugepage
2515  * has (unlike page_mapcount() which isn't fully accurate). This full
2516  * accuracy is primarily needed to know if copy-on-write faults can
2517  * reuse the page and change the mapping to read-write instead of
2518  * copying them. At the same time this returns the total_mapcount too.
2519  *
2520  * The function returns the highest mapcount any one of the subpages
2521  * has. If the return value is one, even if different processes are
2522  * mapping different subpages of the transparent hugepage, they can
2523  * all reuse it, because each process is reusing a different subpage.
2524  *
2525  * The total_mapcount is instead counting all virtual mappings of the
2526  * subpages. If the total_mapcount is equal to "one", it tells the
2527  * caller all mappings belong to the same "mm" and in turn the
2528  * anon_vma of the transparent hugepage can become the vma->anon_vma
2529  * local one as no other process may be mapping any of the subpages.
2530  *
2531  * It would be more accurate to replace page_mapcount() with
2532  * page_trans_huge_mapcount(), however we only use
2533  * page_trans_huge_mapcount() in the copy-on-write faults where we
2534  * need full accuracy to avoid breaking page pinning, because
2535  * page_trans_huge_mapcount() is slower than page_mapcount().
2536  */
2537 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2538 {
2539         int i, ret, _total_mapcount, mapcount;
2540
2541         /* hugetlbfs shouldn't call it */
2542         VM_BUG_ON_PAGE(PageHuge(page), page);
2543
2544         if (likely(!PageTransCompound(page))) {
2545                 mapcount = atomic_read(&page->_mapcount) + 1;
2546                 if (total_mapcount)
2547                         *total_mapcount = mapcount;
2548                 return mapcount;
2549         }
2550
2551         page = compound_head(page);
2552
2553         _total_mapcount = ret = 0;
2554         for (i = 0; i < HPAGE_PMD_NR; i++) {
2555                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2556                 ret = max(ret, mapcount);
2557                 _total_mapcount += mapcount;
2558         }
2559         if (PageDoubleMap(page)) {
2560                 ret -= 1;
2561                 _total_mapcount -= HPAGE_PMD_NR;
2562         }
2563         mapcount = compound_mapcount(page);
2564         ret += mapcount;
2565         _total_mapcount += mapcount;
2566         if (total_mapcount)
2567                 *total_mapcount = _total_mapcount;
2568         return ret;
2569 }
2570
2571 /* Racy check whether the huge page can be split */
2572 bool can_split_huge_page(struct page *page, int *pextra_pins)
2573 {
2574         int extra_pins;
2575
2576         /* Additional pins from page cache */
2577         if (PageAnon(page))
2578                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2579         else
2580                 extra_pins = HPAGE_PMD_NR;
2581         if (pextra_pins)
2582                 *pextra_pins = extra_pins;
2583         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2584 }
2585
2586 /*
2587  * This function splits huge page into normal pages. @page can point to any
2588  * subpage of huge page to split. Split doesn't change the position of @page.
2589  *
2590  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2591  * The huge page must be locked.
2592  *
2593  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2594  *
2595  * Both head page and tail pages will inherit mapping, flags, and so on from
2596  * the hugepage.
2597  *
2598  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2599  * they are not mapped.
2600  *
2601  * Returns 0 if the hugepage is split successfully.
2602  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2603  * us.
2604  */
2605 int split_huge_page_to_list(struct page *page, struct list_head *list)
2606 {
2607         struct page *head = compound_head(page);
2608         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2609         struct anon_vma *anon_vma = NULL;
2610         struct address_space *mapping = NULL;
2611         int count, mapcount, extra_pins, ret;
2612         bool mlocked;
2613         unsigned long flags;
2614         pgoff_t end;
2615
2616         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2617         VM_BUG_ON_PAGE(!PageLocked(page), page);
2618         VM_BUG_ON_PAGE(!PageCompound(page), page);
2619
2620         if (PageWriteback(page))
2621                 return -EBUSY;
2622
2623         if (PageAnon(head)) {
2624                 /*
2625                  * The caller does not necessarily hold an mmap_sem that would
2626                  * prevent the anon_vma disappearing so we first we take a
2627                  * reference to it and then lock the anon_vma for write. This
2628                  * is similar to page_lock_anon_vma_read except the write lock
2629                  * is taken to serialise against parallel split or collapse
2630                  * operations.
2631                  */
2632                 anon_vma = page_get_anon_vma(head);
2633                 if (!anon_vma) {
2634                         ret = -EBUSY;
2635                         goto out;
2636                 }
2637                 end = -1;
2638                 mapping = NULL;
2639                 anon_vma_lock_write(anon_vma);
2640         } else {
2641                 mapping = head->mapping;
2642
2643                 /* Truncated ? */
2644                 if (!mapping) {
2645                         ret = -EBUSY;
2646                         goto out;
2647                 }
2648
2649                 anon_vma = NULL;
2650                 i_mmap_lock_read(mapping);
2651
2652                 /*
2653                  *__split_huge_page() may need to trim off pages beyond EOF:
2654                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2655                  * which cannot be nested inside the page tree lock. So note
2656                  * end now: i_size itself may be changed at any moment, but
2657                  * head page lock is good enough to serialize the trimming.
2658                  */
2659                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2660         }
2661
2662         /*
2663          * Racy check if we can split the page, before unmap_page() will
2664          * split PMDs
2665          */
2666         if (!can_split_huge_page(head, &extra_pins)) {
2667                 ret = -EBUSY;
2668                 goto out_unlock;
2669         }
2670
2671         mlocked = PageMlocked(page);
2672         unmap_page(head);
2673         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2674
2675         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2676         if (mlocked)
2677                 lru_add_drain();
2678
2679         /* prevent PageLRU to go away from under us, and freeze lru stats */
2680         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2681
2682         if (mapping) {
2683                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2684
2685                 /*
2686                  * Check if the head page is present in page cache.
2687                  * We assume all tail are present too, if head is there.
2688                  */
2689                 xa_lock(&mapping->i_pages);
2690                 if (xas_load(&xas) != head)
2691                         goto fail;
2692         }
2693
2694         /* Prevent deferred_split_scan() touching ->_refcount */
2695         spin_lock(&pgdata->split_queue_lock);
2696         count = page_count(head);
2697         mapcount = total_mapcount(head);
2698         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2699                 if (!list_empty(page_deferred_list(head))) {
2700                         pgdata->split_queue_len--;
2701                         list_del(page_deferred_list(head));
2702                 }
2703                 if (mapping)
2704                         __dec_node_page_state(page, NR_SHMEM_THPS);
2705                 spin_unlock(&pgdata->split_queue_lock);
2706                 __split_huge_page(page, list, end, flags);
2707                 if (PageSwapCache(head)) {
2708                         swp_entry_t entry = { .val = page_private(head) };
2709
2710                         ret = split_swap_cluster(entry);
2711                 } else
2712                         ret = 0;
2713         } else {
2714                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2715                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2716                                         mapcount, count);
2717                         if (PageTail(page))
2718                                 dump_page(head, NULL);
2719                         dump_page(page, "total_mapcount(head) > 0");
2720                         BUG();
2721                 }
2722                 spin_unlock(&pgdata->split_queue_lock);
2723 fail:           if (mapping)
2724                         xa_unlock(&mapping->i_pages);
2725                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2726                 remap_page(head);
2727                 ret = -EBUSY;
2728         }
2729
2730 out_unlock:
2731         if (anon_vma) {
2732                 anon_vma_unlock_write(anon_vma);
2733                 put_anon_vma(anon_vma);
2734         }
2735         if (mapping)
2736                 i_mmap_unlock_read(mapping);
2737 out:
2738         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2739         return ret;
2740 }
2741
2742 void free_transhuge_page(struct page *page)
2743 {
2744         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2745         unsigned long flags;
2746
2747         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2748         if (!list_empty(page_deferred_list(page))) {
2749                 pgdata->split_queue_len--;
2750                 list_del(page_deferred_list(page));
2751         }
2752         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2753         free_compound_page(page);
2754 }
2755
2756 void deferred_split_huge_page(struct page *page)
2757 {
2758         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2759         unsigned long flags;
2760
2761         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2762
2763         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2764         if (list_empty(page_deferred_list(page))) {
2765                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2766                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2767                 pgdata->split_queue_len++;
2768         }
2769         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2770 }
2771
2772 static unsigned long deferred_split_count(struct shrinker *shrink,
2773                 struct shrink_control *sc)
2774 {
2775         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2776         return READ_ONCE(pgdata->split_queue_len);
2777 }
2778
2779 static unsigned long deferred_split_scan(struct shrinker *shrink,
2780                 struct shrink_control *sc)
2781 {
2782         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2783         unsigned long flags;
2784         LIST_HEAD(list), *pos, *next;
2785         struct page *page;
2786         int split = 0;
2787
2788         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2789         /* Take pin on all head pages to avoid freeing them under us */
2790         list_for_each_safe(pos, next, &pgdata->split_queue) {
2791                 page = list_entry((void *)pos, struct page, mapping);
2792                 page = compound_head(page);
2793                 if (get_page_unless_zero(page)) {
2794                         list_move(page_deferred_list(page), &list);
2795                 } else {
2796                         /* We lost race with put_compound_page() */
2797                         list_del_init(page_deferred_list(page));
2798                         pgdata->split_queue_len--;
2799                 }
2800                 if (!--sc->nr_to_scan)
2801                         break;
2802         }
2803         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2804
2805         list_for_each_safe(pos, next, &list) {
2806                 page = list_entry((void *)pos, struct page, mapping);
2807                 if (!trylock_page(page))
2808                         goto next;
2809                 /* split_huge_page() removes page from list on success */
2810                 if (!split_huge_page(page))
2811                         split++;
2812                 unlock_page(page);
2813 next:
2814                 put_page(page);
2815         }
2816
2817         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2818         list_splice_tail(&list, &pgdata->split_queue);
2819         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2820
2821         /*
2822          * Stop shrinker if we didn't split any page, but the queue is empty.
2823          * This can happen if pages were freed under us.
2824          */
2825         if (!split && list_empty(&pgdata->split_queue))
2826                 return SHRINK_STOP;
2827         return split;
2828 }
2829
2830 static struct shrinker deferred_split_shrinker = {
2831         .count_objects = deferred_split_count,
2832         .scan_objects = deferred_split_scan,
2833         .seeks = DEFAULT_SEEKS,
2834         .flags = SHRINKER_NUMA_AWARE,
2835 };
2836
2837 #ifdef CONFIG_DEBUG_FS
2838 static int split_huge_pages_set(void *data, u64 val)
2839 {
2840         struct zone *zone;
2841         struct page *page;
2842         unsigned long pfn, max_zone_pfn;
2843         unsigned long total = 0, split = 0;
2844
2845         if (val != 1)
2846                 return -EINVAL;
2847
2848         for_each_populated_zone(zone) {
2849                 max_zone_pfn = zone_end_pfn(zone);
2850                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2851                         if (!pfn_valid(pfn))
2852                                 continue;
2853
2854                         page = pfn_to_page(pfn);
2855                         if (!get_page_unless_zero(page))
2856                                 continue;
2857
2858                         if (zone != page_zone(page))
2859                                 goto next;
2860
2861                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2862                                 goto next;
2863
2864                         total++;
2865                         lock_page(page);
2866                         if (!split_huge_page(page))
2867                                 split++;
2868                         unlock_page(page);
2869 next:
2870                         put_page(page);
2871                 }
2872         }
2873
2874         pr_info("%lu of %lu THP split\n", split, total);
2875
2876         return 0;
2877 }
2878 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2879                 "%llu\n");
2880
2881 static int __init split_huge_pages_debugfs(void)
2882 {
2883         void *ret;
2884
2885         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2886                         &split_huge_pages_fops);
2887         if (!ret)
2888                 pr_warn("Failed to create split_huge_pages in debugfs");
2889         return 0;
2890 }
2891 late_initcall(split_huge_pages_debugfs);
2892 #endif
2893
2894 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2895 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2896                 struct page *page)
2897 {
2898         struct vm_area_struct *vma = pvmw->vma;
2899         struct mm_struct *mm = vma->vm_mm;
2900         unsigned long address = pvmw->address;
2901         pmd_t pmdval;
2902         swp_entry_t entry;
2903         pmd_t pmdswp;
2904
2905         if (!(pvmw->pmd && !pvmw->pte))
2906                 return;
2907
2908         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2909         pmdval = *pvmw->pmd;
2910         pmdp_invalidate(vma, address, pvmw->pmd);
2911         if (pmd_dirty(pmdval))
2912                 set_page_dirty(page);
2913         entry = make_migration_entry(page, pmd_write(pmdval));
2914         pmdswp = swp_entry_to_pmd(entry);
2915         if (pmd_soft_dirty(pmdval))
2916                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2917         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2918         page_remove_rmap(page, true);
2919         put_page(page);
2920 }
2921
2922 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2923 {
2924         struct vm_area_struct *vma = pvmw->vma;
2925         struct mm_struct *mm = vma->vm_mm;
2926         unsigned long address = pvmw->address;
2927         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2928         pmd_t pmde;
2929         swp_entry_t entry;
2930
2931         if (!(pvmw->pmd && !pvmw->pte))
2932                 return;
2933
2934         entry = pmd_to_swp_entry(*pvmw->pmd);
2935         get_page(new);
2936         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2937         if (pmd_swp_soft_dirty(*pvmw->pmd))
2938                 pmde = pmd_mksoft_dirty(pmde);
2939         if (is_write_migration_entry(entry))
2940                 pmde = maybe_pmd_mkwrite(pmde, vma);
2941
2942         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2943         if (PageAnon(new))
2944                 page_add_anon_rmap(new, vma, mmun_start, true);
2945         else
2946                 page_add_file_rmap(new, true);
2947         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2948         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
2949                 mlock_vma_page(new);
2950         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2951 }
2952 #endif