2 * Copyright (C) 2009 Red Hat, Inc.
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/sched.h>
12 #include <linux/highmem.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mmu_notifier.h>
15 #include <linux/rmap.h>
16 #include <linux/swap.h>
17 #include <linux/shrinker.h>
18 #include <linux/mm_inline.h>
19 #include <linux/swapops.h>
20 #include <linux/dax.h>
21 #include <linux/khugepaged.h>
22 #include <linux/freezer.h>
23 #include <linux/pfn_t.h>
24 #include <linux/mman.h>
25 #include <linux/memremap.h>
26 #include <linux/pagemap.h>
27 #include <linux/debugfs.h>
28 #include <linux/migrate.h>
29 #include <linux/hashtable.h>
30 #include <linux/userfaultfd_k.h>
31 #include <linux/page_idle.h>
32 #include <linux/shmem_fs.h>
35 #include <asm/pgalloc.h>
39 * By default transparent hugepage support is disabled in order that avoid
40 * to risk increase the memory footprint of applications without a guaranteed
41 * benefit. When transparent hugepage support is enabled, is for all mappings,
42 * and khugepaged scans all mappings.
43 * Defrag is invoked by khugepaged hugepage allocations and by page faults
44 * for all hugepage allocations.
46 unsigned long transparent_hugepage_flags __read_mostly =
47 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
48 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
51 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
53 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
54 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
55 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
57 static struct shrinker deferred_split_shrinker;
59 static atomic_t huge_zero_refcount;
60 struct page *huge_zero_page __read_mostly;
62 static struct page *get_huge_zero_page(void)
64 struct page *zero_page;
66 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
67 return READ_ONCE(huge_zero_page);
69 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
72 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
75 count_vm_event(THP_ZERO_PAGE_ALLOC);
77 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
79 __free_pages(zero_page, compound_order(zero_page));
83 /* We take additional reference here. It will be put back by shrinker */
84 atomic_set(&huge_zero_refcount, 2);
86 return READ_ONCE(huge_zero_page);
89 static void put_huge_zero_page(void)
92 * Counter should never go to zero here. Only shrinker can put
95 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
98 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
100 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
101 return READ_ONCE(huge_zero_page);
103 if (!get_huge_zero_page())
106 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
107 put_huge_zero_page();
109 return READ_ONCE(huge_zero_page);
112 void mm_put_huge_zero_page(struct mm_struct *mm)
114 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
115 put_huge_zero_page();
118 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
119 struct shrink_control *sc)
121 /* we can free zero page only if last reference remains */
122 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
125 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
126 struct shrink_control *sc)
128 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
129 struct page *zero_page = xchg(&huge_zero_page, NULL);
130 BUG_ON(zero_page == NULL);
131 __free_pages(zero_page, compound_order(zero_page));
138 static struct shrinker huge_zero_page_shrinker = {
139 .count_objects = shrink_huge_zero_page_count,
140 .scan_objects = shrink_huge_zero_page_scan,
141 .seeks = DEFAULT_SEEKS,
146 static ssize_t triple_flag_store(struct kobject *kobj,
147 struct kobj_attribute *attr,
148 const char *buf, size_t count,
149 enum transparent_hugepage_flag enabled,
150 enum transparent_hugepage_flag deferred,
151 enum transparent_hugepage_flag req_madv)
153 if (!memcmp("defer", buf,
154 min(sizeof("defer")-1, count))) {
155 if (enabled == deferred)
157 clear_bit(enabled, &transparent_hugepage_flags);
158 clear_bit(req_madv, &transparent_hugepage_flags);
159 set_bit(deferred, &transparent_hugepage_flags);
160 } else if (!memcmp("always", buf,
161 min(sizeof("always")-1, count))) {
162 clear_bit(deferred, &transparent_hugepage_flags);
163 clear_bit(req_madv, &transparent_hugepage_flags);
164 set_bit(enabled, &transparent_hugepage_flags);
165 } else if (!memcmp("madvise", buf,
166 min(sizeof("madvise")-1, count))) {
167 clear_bit(enabled, &transparent_hugepage_flags);
168 clear_bit(deferred, &transparent_hugepage_flags);
169 set_bit(req_madv, &transparent_hugepage_flags);
170 } else if (!memcmp("never", buf,
171 min(sizeof("never")-1, count))) {
172 clear_bit(enabled, &transparent_hugepage_flags);
173 clear_bit(req_madv, &transparent_hugepage_flags);
174 clear_bit(deferred, &transparent_hugepage_flags);
181 static ssize_t enabled_show(struct kobject *kobj,
182 struct kobj_attribute *attr, char *buf)
184 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
185 return sprintf(buf, "[always] madvise never\n");
186 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
187 return sprintf(buf, "always [madvise] never\n");
189 return sprintf(buf, "always madvise [never]\n");
192 static ssize_t enabled_store(struct kobject *kobj,
193 struct kobj_attribute *attr,
194 const char *buf, size_t count)
198 ret = triple_flag_store(kobj, attr, buf, count,
199 TRANSPARENT_HUGEPAGE_FLAG,
200 TRANSPARENT_HUGEPAGE_FLAG,
201 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
204 int err = start_stop_khugepaged();
211 static struct kobj_attribute enabled_attr =
212 __ATTR(enabled, 0644, enabled_show, enabled_store);
214 ssize_t single_hugepage_flag_show(struct kobject *kobj,
215 struct kobj_attribute *attr, char *buf,
216 enum transparent_hugepage_flag flag)
218 return sprintf(buf, "%d\n",
219 !!test_bit(flag, &transparent_hugepage_flags));
222 ssize_t single_hugepage_flag_store(struct kobject *kobj,
223 struct kobj_attribute *attr,
224 const char *buf, size_t count,
225 enum transparent_hugepage_flag flag)
230 ret = kstrtoul(buf, 10, &value);
237 set_bit(flag, &transparent_hugepage_flags);
239 clear_bit(flag, &transparent_hugepage_flags);
245 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
246 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
247 * memory just to allocate one more hugepage.
249 static ssize_t defrag_show(struct kobject *kobj,
250 struct kobj_attribute *attr, char *buf)
252 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
253 return sprintf(buf, "[always] defer madvise never\n");
254 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
255 return sprintf(buf, "always [defer] madvise never\n");
256 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
257 return sprintf(buf, "always defer [madvise] never\n");
259 return sprintf(buf, "always defer madvise [never]\n");
262 static ssize_t defrag_store(struct kobject *kobj,
263 struct kobj_attribute *attr,
264 const char *buf, size_t count)
266 return triple_flag_store(kobj, attr, buf, count,
267 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
268 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
269 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
271 static struct kobj_attribute defrag_attr =
272 __ATTR(defrag, 0644, defrag_show, defrag_store);
274 static ssize_t use_zero_page_show(struct kobject *kobj,
275 struct kobj_attribute *attr, char *buf)
277 return single_hugepage_flag_show(kobj, attr, buf,
278 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
280 static ssize_t use_zero_page_store(struct kobject *kobj,
281 struct kobj_attribute *attr, const char *buf, size_t count)
283 return single_hugepage_flag_store(kobj, attr, buf, count,
284 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
286 static struct kobj_attribute use_zero_page_attr =
287 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
288 #ifdef CONFIG_DEBUG_VM
289 static ssize_t debug_cow_show(struct kobject *kobj,
290 struct kobj_attribute *attr, char *buf)
292 return single_hugepage_flag_show(kobj, attr, buf,
293 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
295 static ssize_t debug_cow_store(struct kobject *kobj,
296 struct kobj_attribute *attr,
297 const char *buf, size_t count)
299 return single_hugepage_flag_store(kobj, attr, buf, count,
300 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
302 static struct kobj_attribute debug_cow_attr =
303 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
304 #endif /* CONFIG_DEBUG_VM */
306 static struct attribute *hugepage_attr[] = {
309 &use_zero_page_attr.attr,
310 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
311 &shmem_enabled_attr.attr,
313 #ifdef CONFIG_DEBUG_VM
314 &debug_cow_attr.attr,
319 static struct attribute_group hugepage_attr_group = {
320 .attrs = hugepage_attr,
323 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
327 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
328 if (unlikely(!*hugepage_kobj)) {
329 pr_err("failed to create transparent hugepage kobject\n");
333 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
335 pr_err("failed to register transparent hugepage group\n");
339 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
341 pr_err("failed to register transparent hugepage group\n");
342 goto remove_hp_group;
348 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
350 kobject_put(*hugepage_kobj);
354 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
356 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
357 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
358 kobject_put(hugepage_kobj);
361 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
366 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
369 #endif /* CONFIG_SYSFS */
371 static int __init hugepage_init(void)
374 struct kobject *hugepage_kobj;
376 if (!has_transparent_hugepage()) {
377 transparent_hugepage_flags = 0;
382 * hugepages can't be allocated by the buddy allocator
384 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
386 * we use page->mapping and page->index in second tail page
387 * as list_head: assuming THP order >= 2
389 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
391 err = hugepage_init_sysfs(&hugepage_kobj);
395 err = khugepaged_init();
399 err = register_shrinker(&huge_zero_page_shrinker);
401 goto err_hzp_shrinker;
402 err = register_shrinker(&deferred_split_shrinker);
404 goto err_split_shrinker;
407 * By default disable transparent hugepages on smaller systems,
408 * where the extra memory used could hurt more than TLB overhead
409 * is likely to save. The admin can still enable it through /sys.
411 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
412 transparent_hugepage_flags = 0;
416 err = start_stop_khugepaged();
422 unregister_shrinker(&deferred_split_shrinker);
424 unregister_shrinker(&huge_zero_page_shrinker);
426 khugepaged_destroy();
428 hugepage_exit_sysfs(hugepage_kobj);
432 subsys_initcall(hugepage_init);
434 static int __init setup_transparent_hugepage(char *str)
439 if (!strcmp(str, "always")) {
440 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
441 &transparent_hugepage_flags);
442 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
443 &transparent_hugepage_flags);
445 } else if (!strcmp(str, "madvise")) {
446 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
447 &transparent_hugepage_flags);
448 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
449 &transparent_hugepage_flags);
451 } else if (!strcmp(str, "never")) {
452 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
453 &transparent_hugepage_flags);
454 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
455 &transparent_hugepage_flags);
460 pr_warn("transparent_hugepage= cannot parse, ignored\n");
463 __setup("transparent_hugepage=", setup_transparent_hugepage);
465 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
467 if (likely(vma->vm_flags & VM_WRITE))
468 pmd = pmd_mkwrite(pmd);
472 static inline struct list_head *page_deferred_list(struct page *page)
475 * ->lru in the tail pages is occupied by compound_head.
476 * Let's use ->mapping + ->index in the second tail page as list_head.
478 return (struct list_head *)&page[2].mapping;
481 void prep_transhuge_page(struct page *page)
484 * we use page->mapping and page->indexlru in second tail page
485 * as list_head: assuming THP order >= 2
488 INIT_LIST_HEAD(page_deferred_list(page));
489 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
492 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
493 loff_t off, unsigned long flags, unsigned long size)
496 loff_t off_end = off + len;
497 loff_t off_align = round_up(off, size);
498 unsigned long len_pad;
500 if (off_end <= off_align || (off_end - off_align) < size)
503 len_pad = len + size;
504 if (len_pad < len || (off + len_pad) < off)
507 addr = current->mm->get_unmapped_area(filp, 0, len_pad,
508 off >> PAGE_SHIFT, flags);
509 if (IS_ERR_VALUE(addr))
512 addr += (off - addr) & (size - 1);
516 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
517 unsigned long len, unsigned long pgoff, unsigned long flags)
519 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
523 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
526 addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
531 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
533 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
535 static int __do_huge_pmd_anonymous_page(struct fault_env *fe, struct page *page,
538 struct vm_area_struct *vma = fe->vma;
539 struct mem_cgroup *memcg;
541 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
543 VM_BUG_ON_PAGE(!PageCompound(page), page);
545 if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
547 count_vm_event(THP_FAULT_FALLBACK);
548 return VM_FAULT_FALLBACK;
551 pgtable = pte_alloc_one(vma->vm_mm, haddr);
552 if (unlikely(!pgtable)) {
553 mem_cgroup_cancel_charge(page, memcg, true);
558 clear_huge_page(page, haddr, HPAGE_PMD_NR);
560 * The memory barrier inside __SetPageUptodate makes sure that
561 * clear_huge_page writes become visible before the set_pmd_at()
564 __SetPageUptodate(page);
566 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
567 if (unlikely(!pmd_none(*fe->pmd))) {
568 spin_unlock(fe->ptl);
569 mem_cgroup_cancel_charge(page, memcg, true);
571 pte_free(vma->vm_mm, pgtable);
575 /* Deliver the page fault to userland */
576 if (userfaultfd_missing(vma)) {
579 spin_unlock(fe->ptl);
580 mem_cgroup_cancel_charge(page, memcg, true);
582 pte_free(vma->vm_mm, pgtable);
583 ret = handle_userfault(fe, VM_UFFD_MISSING);
584 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
588 entry = mk_huge_pmd(page, vma->vm_page_prot);
589 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
590 page_add_new_anon_rmap(page, vma, haddr, true);
591 mem_cgroup_commit_charge(page, memcg, false, true);
592 lru_cache_add_active_or_unevictable(page, vma);
593 pgtable_trans_huge_deposit(vma->vm_mm, fe->pmd, pgtable);
594 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
595 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
596 atomic_long_inc(&vma->vm_mm->nr_ptes);
597 spin_unlock(fe->ptl);
598 count_vm_event(THP_FAULT_ALLOC);
605 * If THP defrag is set to always then directly reclaim/compact as necessary
606 * If set to defer then do only background reclaim/compact and defer to khugepaged
607 * If set to madvise and the VMA is flagged then directly reclaim/compact
608 * When direct reclaim/compact is allowed, don't retry except for flagged VMA's
610 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
612 bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
614 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
615 &transparent_hugepage_flags) && vma_madvised)
616 return GFP_TRANSHUGE;
617 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
618 &transparent_hugepage_flags))
619 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
620 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
621 &transparent_hugepage_flags))
622 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
624 return GFP_TRANSHUGE_LIGHT;
627 /* Caller must hold page table lock. */
628 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
629 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
630 struct page *zero_page)
635 entry = mk_pmd(zero_page, vma->vm_page_prot);
636 entry = pmd_mkhuge(entry);
638 pgtable_trans_huge_deposit(mm, pmd, pgtable);
639 set_pmd_at(mm, haddr, pmd, entry);
640 atomic_long_inc(&mm->nr_ptes);
644 int do_huge_pmd_anonymous_page(struct fault_env *fe)
646 struct vm_area_struct *vma = fe->vma;
649 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
651 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
652 return VM_FAULT_FALLBACK;
653 if (unlikely(anon_vma_prepare(vma)))
655 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
657 if (!(fe->flags & FAULT_FLAG_WRITE) &&
658 !mm_forbids_zeropage(vma->vm_mm) &&
659 transparent_hugepage_use_zero_page()) {
661 struct page *zero_page;
664 pgtable = pte_alloc_one(vma->vm_mm, haddr);
665 if (unlikely(!pgtable))
667 zero_page = mm_get_huge_zero_page(vma->vm_mm);
668 if (unlikely(!zero_page)) {
669 pte_free(vma->vm_mm, pgtable);
670 count_vm_event(THP_FAULT_FALLBACK);
671 return VM_FAULT_FALLBACK;
673 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
676 if (pmd_none(*fe->pmd)) {
677 if (userfaultfd_missing(vma)) {
678 spin_unlock(fe->ptl);
679 ret = handle_userfault(fe, VM_UFFD_MISSING);
680 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
682 set_huge_zero_page(pgtable, vma->vm_mm, vma,
683 haddr, fe->pmd, zero_page);
684 spin_unlock(fe->ptl);
688 spin_unlock(fe->ptl);
690 pte_free(vma->vm_mm, pgtable);
693 gfp = alloc_hugepage_direct_gfpmask(vma);
694 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
695 if (unlikely(!page)) {
696 count_vm_event(THP_FAULT_FALLBACK);
697 return VM_FAULT_FALLBACK;
699 prep_transhuge_page(page);
700 return __do_huge_pmd_anonymous_page(fe, page, gfp);
703 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
704 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
706 struct mm_struct *mm = vma->vm_mm;
710 ptl = pmd_lock(mm, pmd);
711 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
712 if (pfn_t_devmap(pfn))
713 entry = pmd_mkdevmap(entry);
715 entry = pmd_mkyoung(pmd_mkdirty(entry));
716 entry = maybe_pmd_mkwrite(entry, vma);
718 set_pmd_at(mm, addr, pmd, entry);
719 update_mmu_cache_pmd(vma, addr, pmd);
723 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
724 pmd_t *pmd, pfn_t pfn, bool write)
726 pgprot_t pgprot = vma->vm_page_prot;
728 * If we had pmd_special, we could avoid all these restrictions,
729 * but we need to be consistent with PTEs and architectures that
730 * can't support a 'special' bit.
732 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
733 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
734 (VM_PFNMAP|VM_MIXEDMAP));
735 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
736 BUG_ON(!pfn_t_devmap(pfn));
738 if (addr < vma->vm_start || addr >= vma->vm_end)
739 return VM_FAULT_SIGBUS;
741 track_pfn_insert(vma, &pgprot, pfn);
743 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
744 return VM_FAULT_NOPAGE;
746 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
748 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
754 * We should set the dirty bit only for FOLL_WRITE but for now
755 * the dirty bit in the pmd is meaningless. And if the dirty
756 * bit will become meaningful and we'll only set it with
757 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
758 * set the young bit, instead of the current set_pmd_at.
760 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
761 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
763 update_mmu_cache_pmd(vma, addr, pmd);
766 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
767 pmd_t *pmd, int flags)
769 unsigned long pfn = pmd_pfn(*pmd);
770 struct mm_struct *mm = vma->vm_mm;
771 struct dev_pagemap *pgmap;
774 assert_spin_locked(pmd_lockptr(mm, pmd));
776 if (flags & FOLL_WRITE && !pmd_write(*pmd))
779 if (pmd_present(*pmd) && pmd_devmap(*pmd))
784 if (flags & FOLL_TOUCH)
785 touch_pmd(vma, addr, pmd);
788 * device mapped pages can only be returned if the
789 * caller will manage the page reference count.
791 if (!(flags & FOLL_GET))
792 return ERR_PTR(-EEXIST);
794 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
795 pgmap = get_dev_pagemap(pfn, NULL);
797 return ERR_PTR(-EFAULT);
798 page = pfn_to_page(pfn);
800 put_dev_pagemap(pgmap);
805 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
806 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
807 struct vm_area_struct *vma)
809 spinlock_t *dst_ptl, *src_ptl;
810 struct page *src_page;
812 pgtable_t pgtable = NULL;
815 /* Skip if can be re-fill on fault */
816 if (!vma_is_anonymous(vma))
819 pgtable = pte_alloc_one(dst_mm, addr);
820 if (unlikely(!pgtable))
823 dst_ptl = pmd_lock(dst_mm, dst_pmd);
824 src_ptl = pmd_lockptr(src_mm, src_pmd);
825 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
829 if (unlikely(!pmd_trans_huge(pmd))) {
830 pte_free(dst_mm, pgtable);
834 * When page table lock is held, the huge zero pmd should not be
835 * under splitting since we don't split the page itself, only pmd to
838 if (is_huge_zero_pmd(pmd)) {
839 struct page *zero_page;
841 * get_huge_zero_page() will never allocate a new page here,
842 * since we already have a zero page to copy. It just takes a
845 zero_page = mm_get_huge_zero_page(dst_mm);
846 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
852 src_page = pmd_page(pmd);
853 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
855 page_dup_rmap(src_page, true);
856 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
857 atomic_long_inc(&dst_mm->nr_ptes);
858 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
860 pmdp_set_wrprotect(src_mm, addr, src_pmd);
861 pmd = pmd_mkold(pmd_wrprotect(pmd));
862 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
866 spin_unlock(src_ptl);
867 spin_unlock(dst_ptl);
872 void huge_pmd_set_accessed(struct fault_env *fe, pmd_t orig_pmd)
877 fe->ptl = pmd_lock(fe->vma->vm_mm, fe->pmd);
878 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
881 entry = pmd_mkyoung(orig_pmd);
882 haddr = fe->address & HPAGE_PMD_MASK;
883 if (pmdp_set_access_flags(fe->vma, haddr, fe->pmd, entry,
884 fe->flags & FAULT_FLAG_WRITE))
885 update_mmu_cache_pmd(fe->vma, fe->address, fe->pmd);
888 spin_unlock(fe->ptl);
891 static int do_huge_pmd_wp_page_fallback(struct fault_env *fe, pmd_t orig_pmd,
894 struct vm_area_struct *vma = fe->vma;
895 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
896 struct mem_cgroup *memcg;
901 unsigned long mmun_start; /* For mmu_notifiers */
902 unsigned long mmun_end; /* For mmu_notifiers */
904 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
906 if (unlikely(!pages)) {
911 for (i = 0; i < HPAGE_PMD_NR; i++) {
912 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
913 __GFP_OTHER_NODE, vma,
914 fe->address, page_to_nid(page));
915 if (unlikely(!pages[i] ||
916 mem_cgroup_try_charge(pages[i], vma->vm_mm,
917 GFP_KERNEL, &memcg, false))) {
921 memcg = (void *)page_private(pages[i]);
922 set_page_private(pages[i], 0);
923 mem_cgroup_cancel_charge(pages[i], memcg,
931 set_page_private(pages[i], (unsigned long)memcg);
934 for (i = 0; i < HPAGE_PMD_NR; i++) {
935 copy_user_highpage(pages[i], page + i,
936 haddr + PAGE_SIZE * i, vma);
937 __SetPageUptodate(pages[i]);
942 mmun_end = haddr + HPAGE_PMD_SIZE;
943 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
945 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
946 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
948 VM_BUG_ON_PAGE(!PageHead(page), page);
950 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
951 /* leave pmd empty until pte is filled */
953 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, fe->pmd);
954 pmd_populate(vma->vm_mm, &_pmd, pgtable);
956 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
958 entry = mk_pte(pages[i], vma->vm_page_prot);
959 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
960 memcg = (void *)page_private(pages[i]);
961 set_page_private(pages[i], 0);
962 page_add_new_anon_rmap(pages[i], fe->vma, haddr, false);
963 mem_cgroup_commit_charge(pages[i], memcg, false, false);
964 lru_cache_add_active_or_unevictable(pages[i], vma);
965 fe->pte = pte_offset_map(&_pmd, haddr);
966 VM_BUG_ON(!pte_none(*fe->pte));
967 set_pte_at(vma->vm_mm, haddr, fe->pte, entry);
972 smp_wmb(); /* make pte visible before pmd */
973 pmd_populate(vma->vm_mm, fe->pmd, pgtable);
974 page_remove_rmap(page, true);
975 spin_unlock(fe->ptl);
977 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
979 ret |= VM_FAULT_WRITE;
986 spin_unlock(fe->ptl);
987 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
988 for (i = 0; i < HPAGE_PMD_NR; i++) {
989 memcg = (void *)page_private(pages[i]);
990 set_page_private(pages[i], 0);
991 mem_cgroup_cancel_charge(pages[i], memcg, false);
998 int do_huge_pmd_wp_page(struct fault_env *fe, pmd_t orig_pmd)
1000 struct vm_area_struct *vma = fe->vma;
1001 struct page *page = NULL, *new_page;
1002 struct mem_cgroup *memcg;
1003 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1004 unsigned long mmun_start; /* For mmu_notifiers */
1005 unsigned long mmun_end; /* For mmu_notifiers */
1006 gfp_t huge_gfp; /* for allocation and charge */
1009 fe->ptl = pmd_lockptr(vma->vm_mm, fe->pmd);
1010 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1011 if (is_huge_zero_pmd(orig_pmd))
1014 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1017 page = pmd_page(orig_pmd);
1018 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1020 * We can only reuse the page if nobody else maps the huge page or it's
1023 if (page_trans_huge_mapcount(page, NULL) == 1) {
1025 entry = pmd_mkyoung(orig_pmd);
1026 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1027 if (pmdp_set_access_flags(vma, haddr, fe->pmd, entry, 1))
1028 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1029 ret |= VM_FAULT_WRITE;
1033 spin_unlock(fe->ptl);
1035 if (transparent_hugepage_enabled(vma) &&
1036 !transparent_hugepage_debug_cow()) {
1037 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1038 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1042 if (likely(new_page)) {
1043 prep_transhuge_page(new_page);
1046 split_huge_pmd(vma, fe->pmd, fe->address);
1047 ret |= VM_FAULT_FALLBACK;
1049 ret = do_huge_pmd_wp_page_fallback(fe, orig_pmd, page);
1050 if (ret & VM_FAULT_OOM) {
1051 split_huge_pmd(vma, fe->pmd, fe->address);
1052 ret |= VM_FAULT_FALLBACK;
1056 count_vm_event(THP_FAULT_FALLBACK);
1060 if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1061 huge_gfp, &memcg, true))) {
1063 split_huge_pmd(vma, fe->pmd, fe->address);
1066 ret |= VM_FAULT_FALLBACK;
1067 count_vm_event(THP_FAULT_FALLBACK);
1071 count_vm_event(THP_FAULT_ALLOC);
1074 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1076 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1077 __SetPageUptodate(new_page);
1080 mmun_end = haddr + HPAGE_PMD_SIZE;
1081 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1086 if (unlikely(!pmd_same(*fe->pmd, orig_pmd))) {
1087 spin_unlock(fe->ptl);
1088 mem_cgroup_cancel_charge(new_page, memcg, true);
1093 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1094 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1095 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
1096 page_add_new_anon_rmap(new_page, vma, haddr, true);
1097 mem_cgroup_commit_charge(new_page, memcg, false, true);
1098 lru_cache_add_active_or_unevictable(new_page, vma);
1099 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
1100 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1102 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1104 VM_BUG_ON_PAGE(!PageHead(page), page);
1105 page_remove_rmap(page, true);
1108 ret |= VM_FAULT_WRITE;
1110 spin_unlock(fe->ptl);
1112 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1116 spin_unlock(fe->ptl);
1120 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1125 struct mm_struct *mm = vma->vm_mm;
1126 struct page *page = NULL;
1128 assert_spin_locked(pmd_lockptr(mm, pmd));
1130 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1133 /* Avoid dumping huge zero page */
1134 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1135 return ERR_PTR(-EFAULT);
1137 /* Full NUMA hinting faults to serialise migration in fault paths */
1138 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1141 page = pmd_page(*pmd);
1142 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1143 if (flags & FOLL_TOUCH)
1144 touch_pmd(vma, addr, pmd);
1145 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1147 * We don't mlock() pte-mapped THPs. This way we can avoid
1148 * leaking mlocked pages into non-VM_LOCKED VMAs.
1152 * In most cases the pmd is the only mapping of the page as we
1153 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1154 * writable private mappings in populate_vma_page_range().
1156 * The only scenario when we have the page shared here is if we
1157 * mlocking read-only mapping shared over fork(). We skip
1158 * mlocking such pages.
1162 * We can expect PageDoubleMap() to be stable under page lock:
1163 * for file pages we set it in page_add_file_rmap(), which
1164 * requires page to be locked.
1167 if (PageAnon(page) && compound_mapcount(page) != 1)
1169 if (PageDoubleMap(page) || !page->mapping)
1171 if (!trylock_page(page))
1174 if (page->mapping && !PageDoubleMap(page))
1175 mlock_vma_page(page);
1179 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1180 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1181 if (flags & FOLL_GET)
1188 /* NUMA hinting page fault entry point for trans huge pmds */
1189 int do_huge_pmd_numa_page(struct fault_env *fe, pmd_t pmd)
1191 struct vm_area_struct *vma = fe->vma;
1192 struct anon_vma *anon_vma = NULL;
1194 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1195 int page_nid = -1, this_nid = numa_node_id();
1196 int target_nid, last_cpupid = -1;
1198 bool migrated = false;
1202 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
1203 if (unlikely(!pmd_same(pmd, *fe->pmd)))
1207 * If there are potential migrations, wait for completion and retry
1208 * without disrupting NUMA hinting information. Do not relock and
1209 * check_same as the page may no longer be mapped.
1211 if (unlikely(pmd_trans_migrating(*fe->pmd))) {
1212 page = pmd_page(*fe->pmd);
1213 spin_unlock(fe->ptl);
1214 wait_on_page_locked(page);
1218 page = pmd_page(pmd);
1219 BUG_ON(is_huge_zero_page(page));
1220 page_nid = page_to_nid(page);
1221 last_cpupid = page_cpupid_last(page);
1222 count_vm_numa_event(NUMA_HINT_FAULTS);
1223 if (page_nid == this_nid) {
1224 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1225 flags |= TNF_FAULT_LOCAL;
1228 /* See similar comment in do_numa_page for explanation */
1229 if (!pmd_write(pmd))
1230 flags |= TNF_NO_GROUP;
1233 * Acquire the page lock to serialise THP migrations but avoid dropping
1234 * page_table_lock if at all possible
1236 page_locked = trylock_page(page);
1237 target_nid = mpol_misplaced(page, vma, haddr);
1238 if (target_nid == -1) {
1239 /* If the page was locked, there are no parallel migrations */
1244 /* Migration could have started since the pmd_trans_migrating check */
1246 spin_unlock(fe->ptl);
1247 wait_on_page_locked(page);
1253 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1254 * to serialises splits
1257 spin_unlock(fe->ptl);
1258 anon_vma = page_lock_anon_vma_read(page);
1260 /* Confirm the PMD did not change while page_table_lock was released */
1262 if (unlikely(!pmd_same(pmd, *fe->pmd))) {
1269 /* Bail if we fail to protect against THP splits for any reason */
1270 if (unlikely(!anon_vma)) {
1277 * Migrate the THP to the requested node, returns with page unlocked
1278 * and access rights restored.
1280 spin_unlock(fe->ptl);
1281 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1282 fe->pmd, pmd, fe->address, page, target_nid);
1284 flags |= TNF_MIGRATED;
1285 page_nid = target_nid;
1287 flags |= TNF_MIGRATE_FAIL;
1291 BUG_ON(!PageLocked(page));
1292 was_writable = pmd_write(pmd);
1293 pmd = pmd_modify(pmd, vma->vm_page_prot);
1294 pmd = pmd_mkyoung(pmd);
1296 pmd = pmd_mkwrite(pmd);
1297 set_pmd_at(vma->vm_mm, haddr, fe->pmd, pmd);
1298 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1301 spin_unlock(fe->ptl);
1305 page_unlock_anon_vma_read(anon_vma);
1308 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, fe->flags);
1314 * Return true if we do MADV_FREE successfully on entire pmd page.
1315 * Otherwise, return false.
1317 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1318 pmd_t *pmd, unsigned long addr, unsigned long next)
1323 struct mm_struct *mm = tlb->mm;
1326 ptl = pmd_trans_huge_lock(pmd, vma);
1331 if (is_huge_zero_pmd(orig_pmd))
1334 page = pmd_page(orig_pmd);
1336 * If other processes are mapping this page, we couldn't discard
1337 * the page unless they all do MADV_FREE so let's skip the page.
1339 if (page_mapcount(page) != 1)
1342 if (!trylock_page(page))
1346 * If user want to discard part-pages of THP, split it so MADV_FREE
1347 * will deactivate only them.
1349 if (next - addr != HPAGE_PMD_SIZE) {
1352 split_huge_page(page);
1358 if (PageDirty(page))
1359 ClearPageDirty(page);
1362 if (PageActive(page))
1363 deactivate_page(page);
1365 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1366 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1368 orig_pmd = pmd_mkold(orig_pmd);
1369 orig_pmd = pmd_mkclean(orig_pmd);
1371 set_pmd_at(mm, addr, pmd, orig_pmd);
1372 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1381 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1382 pmd_t *pmd, unsigned long addr)
1387 ptl = __pmd_trans_huge_lock(pmd, vma);
1391 * For architectures like ppc64 we look at deposited pgtable
1392 * when calling pmdp_huge_get_and_clear. So do the
1393 * pgtable_trans_huge_withdraw after finishing pmdp related
1396 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1398 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1399 if (vma_is_dax(vma)) {
1401 if (is_huge_zero_pmd(orig_pmd))
1402 tlb_remove_page(tlb, pmd_page(orig_pmd));
1403 } else if (is_huge_zero_pmd(orig_pmd)) {
1404 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1405 atomic_long_dec(&tlb->mm->nr_ptes);
1407 tlb_remove_page(tlb, pmd_page(orig_pmd));
1409 struct page *page = pmd_page(orig_pmd);
1410 page_remove_rmap(page, true);
1411 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1412 VM_BUG_ON_PAGE(!PageHead(page), page);
1413 if (PageAnon(page)) {
1415 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1416 pte_free(tlb->mm, pgtable);
1417 atomic_long_dec(&tlb->mm->nr_ptes);
1418 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1420 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1423 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1428 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1429 unsigned long new_addr, unsigned long old_end,
1430 pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1432 spinlock_t *old_ptl, *new_ptl;
1434 struct mm_struct *mm = vma->vm_mm;
1435 bool force_flush = false;
1437 if ((old_addr & ~HPAGE_PMD_MASK) ||
1438 (new_addr & ~HPAGE_PMD_MASK) ||
1439 old_end - old_addr < HPAGE_PMD_SIZE)
1443 * The destination pmd shouldn't be established, free_pgtables()
1444 * should have release it.
1446 if (WARN_ON(!pmd_none(*new_pmd))) {
1447 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1452 * We don't have to worry about the ordering of src and dst
1453 * ptlocks because exclusive mmap_sem prevents deadlock.
1455 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1457 new_ptl = pmd_lockptr(mm, new_pmd);
1458 if (new_ptl != old_ptl)
1459 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1460 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1461 if (pmd_present(pmd) && pmd_dirty(pmd))
1463 VM_BUG_ON(!pmd_none(*new_pmd));
1465 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1466 vma_is_anonymous(vma)) {
1468 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1469 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1471 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1472 if (new_ptl != old_ptl)
1473 spin_unlock(new_ptl);
1475 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1478 spin_unlock(old_ptl);
1486 * - 0 if PMD could not be locked
1487 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1488 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1490 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1491 unsigned long addr, pgprot_t newprot, int prot_numa)
1493 struct mm_struct *mm = vma->vm_mm;
1497 ptl = __pmd_trans_huge_lock(pmd, vma);
1500 bool preserve_write = prot_numa && pmd_write(*pmd);
1504 * Avoid trapping faults against the zero page. The read-only
1505 * data is likely to be read-cached on the local CPU and
1506 * local/remote hits to the zero page are not interesting.
1508 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1513 if (!prot_numa || !pmd_protnone(*pmd)) {
1514 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1515 entry = pmd_modify(entry, newprot);
1517 entry = pmd_mkwrite(entry);
1519 set_pmd_at(mm, addr, pmd, entry);
1520 BUG_ON(vma_is_anonymous(vma) && !preserve_write &&
1530 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1532 * Note that if it returns page table lock pointer, this routine returns without
1533 * unlocking page table lock. So callers must unlock it.
1535 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1538 ptl = pmd_lock(vma->vm_mm, pmd);
1539 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1545 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1546 unsigned long haddr, pmd_t *pmd)
1548 struct mm_struct *mm = vma->vm_mm;
1553 /* leave pmd empty until pte is filled */
1554 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1556 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1557 pmd_populate(mm, &_pmd, pgtable);
1559 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1561 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1562 entry = pte_mkspecial(entry);
1563 pte = pte_offset_map(&_pmd, haddr);
1564 VM_BUG_ON(!pte_none(*pte));
1565 set_pte_at(mm, haddr, pte, entry);
1568 smp_wmb(); /* make pte visible before pmd */
1569 pmd_populate(mm, pmd, pgtable);
1572 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
1573 unsigned long haddr, bool freeze)
1575 struct mm_struct *mm = vma->vm_mm;
1579 bool young, write, dirty, soft_dirty;
1583 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
1584 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1585 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
1586 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
1588 count_vm_event(THP_SPLIT_PMD);
1590 if (!vma_is_anonymous(vma)) {
1591 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1592 if (vma_is_dax(vma))
1594 page = pmd_page(_pmd);
1595 if (!PageReferenced(page) && pmd_young(_pmd))
1596 SetPageReferenced(page);
1597 page_remove_rmap(page, true);
1599 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1601 } else if (is_huge_zero_pmd(*pmd)) {
1602 return __split_huge_zero_page_pmd(vma, haddr, pmd);
1605 page = pmd_page(*pmd);
1606 VM_BUG_ON_PAGE(!page_count(page), page);
1607 page_ref_add(page, HPAGE_PMD_NR - 1);
1608 write = pmd_write(*pmd);
1609 young = pmd_young(*pmd);
1610 dirty = pmd_dirty(*pmd);
1611 soft_dirty = pmd_soft_dirty(*pmd);
1613 pmdp_huge_split_prepare(vma, haddr, pmd);
1614 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1615 pmd_populate(mm, &_pmd, pgtable);
1617 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
1620 * Note that NUMA hinting access restrictions are not
1621 * transferred to avoid any possibility of altering
1622 * permissions across VMAs.
1625 swp_entry_t swp_entry;
1626 swp_entry = make_migration_entry(page + i, write);
1627 entry = swp_entry_to_pte(swp_entry);
1629 entry = pte_swp_mksoft_dirty(entry);
1631 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
1632 entry = maybe_mkwrite(entry, vma);
1634 entry = pte_wrprotect(entry);
1636 entry = pte_mkold(entry);
1638 entry = pte_mksoft_dirty(entry);
1641 SetPageDirty(page + i);
1642 pte = pte_offset_map(&_pmd, addr);
1643 BUG_ON(!pte_none(*pte));
1644 set_pte_at(mm, addr, pte, entry);
1645 atomic_inc(&page[i]._mapcount);
1650 * Set PG_double_map before dropping compound_mapcount to avoid
1651 * false-negative page_mapped().
1653 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
1654 for (i = 0; i < HPAGE_PMD_NR; i++)
1655 atomic_inc(&page[i]._mapcount);
1658 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
1659 /* Last compound_mapcount is gone. */
1660 __dec_node_page_state(page, NR_ANON_THPS);
1661 if (TestClearPageDoubleMap(page)) {
1662 /* No need in mapcount reference anymore */
1663 for (i = 0; i < HPAGE_PMD_NR; i++)
1664 atomic_dec(&page[i]._mapcount);
1668 smp_wmb(); /* make pte visible before pmd */
1670 * Up to this point the pmd is present and huge and userland has the
1671 * whole access to the hugepage during the split (which happens in
1672 * place). If we overwrite the pmd with the not-huge version pointing
1673 * to the pte here (which of course we could if all CPUs were bug
1674 * free), userland could trigger a small page size TLB miss on the
1675 * small sized TLB while the hugepage TLB entry is still established in
1676 * the huge TLB. Some CPU doesn't like that.
1677 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
1678 * 383 on page 93. Intel should be safe but is also warns that it's
1679 * only safe if the permission and cache attributes of the two entries
1680 * loaded in the two TLB is identical (which should be the case here).
1681 * But it is generally safer to never allow small and huge TLB entries
1682 * for the same virtual address to be loaded simultaneously. So instead
1683 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
1684 * current pmd notpresent (atomically because here the pmd_trans_huge
1685 * and pmd_trans_splitting must remain set at all times on the pmd
1686 * until the split is complete for this pmd), then we flush the SMP TLB
1687 * and finally we write the non-huge version of the pmd entry with
1690 pmdp_invalidate(vma, haddr, pmd);
1691 pmd_populate(mm, pmd, pgtable);
1694 for (i = 0; i < HPAGE_PMD_NR; i++) {
1695 page_remove_rmap(page + i, false);
1701 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1702 unsigned long address, bool freeze, struct page *page)
1705 struct mm_struct *mm = vma->vm_mm;
1706 unsigned long haddr = address & HPAGE_PMD_MASK;
1708 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
1709 ptl = pmd_lock(mm, pmd);
1712 * If caller asks to setup a migration entries, we need a page to check
1713 * pmd against. Otherwise we can end up replacing wrong page.
1715 VM_BUG_ON(freeze && !page);
1716 if (page && page != pmd_page(*pmd))
1719 if (pmd_trans_huge(*pmd)) {
1720 page = pmd_page(*pmd);
1721 if (PageMlocked(page))
1722 clear_page_mlock(page);
1723 } else if (!pmd_devmap(*pmd))
1725 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
1728 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
1731 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
1732 bool freeze, struct page *page)
1738 pgd = pgd_offset(vma->vm_mm, address);
1739 if (!pgd_present(*pgd))
1742 pud = pud_offset(pgd, address);
1743 if (!pud_present(*pud))
1746 pmd = pmd_offset(pud, address);
1748 __split_huge_pmd(vma, pmd, address, freeze, page);
1751 void vma_adjust_trans_huge(struct vm_area_struct *vma,
1752 unsigned long start,
1757 * If the new start address isn't hpage aligned and it could
1758 * previously contain an hugepage: check if we need to split
1761 if (start & ~HPAGE_PMD_MASK &&
1762 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
1763 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
1764 split_huge_pmd_address(vma, start, false, NULL);
1767 * If the new end address isn't hpage aligned and it could
1768 * previously contain an hugepage: check if we need to split
1771 if (end & ~HPAGE_PMD_MASK &&
1772 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
1773 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
1774 split_huge_pmd_address(vma, end, false, NULL);
1777 * If we're also updating the vma->vm_next->vm_start, if the new
1778 * vm_next->vm_start isn't page aligned and it could previously
1779 * contain an hugepage: check if we need to split an huge pmd.
1781 if (adjust_next > 0) {
1782 struct vm_area_struct *next = vma->vm_next;
1783 unsigned long nstart = next->vm_start;
1784 nstart += adjust_next << PAGE_SHIFT;
1785 if (nstart & ~HPAGE_PMD_MASK &&
1786 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
1787 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
1788 split_huge_pmd_address(next, nstart, false, NULL);
1792 static void freeze_page(struct page *page)
1794 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
1798 VM_BUG_ON_PAGE(!PageHead(page), page);
1801 ttu_flags |= TTU_MIGRATION;
1803 /* We only need TTU_SPLIT_HUGE_PMD once */
1804 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
1805 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) {
1806 /* Cut short if the page is unmapped */
1807 if (page_count(page) == 1)
1810 ret = try_to_unmap(page + i, ttu_flags);
1812 VM_BUG_ON_PAGE(ret, page + i - 1);
1815 static void unfreeze_page(struct page *page)
1819 for (i = 0; i < HPAGE_PMD_NR; i++)
1820 remove_migration_ptes(page + i, page + i, true);
1823 static void __split_huge_page_tail(struct page *head, int tail,
1824 struct lruvec *lruvec, struct list_head *list)
1826 struct page *page_tail = head + tail;
1828 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
1829 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
1832 * tail_page->_refcount is zero and not changing from under us. But
1833 * get_page_unless_zero() may be running from under us on the
1834 * tail_page. If we used atomic_set() below instead of atomic_inc() or
1835 * atomic_add(), we would then run atomic_set() concurrently with
1836 * get_page_unless_zero(), and atomic_set() is implemented in C not
1837 * using locked ops. spin_unlock on x86 sometime uses locked ops
1838 * because of PPro errata 66, 92, so unless somebody can guarantee
1839 * atomic_set() here would be safe on all archs (and not only on x86),
1840 * it's safer to use atomic_inc()/atomic_add().
1842 if (PageAnon(head)) {
1843 page_ref_inc(page_tail);
1845 /* Additional pin to radix tree */
1846 page_ref_add(page_tail, 2);
1849 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1850 page_tail->flags |= (head->flags &
1851 ((1L << PG_referenced) |
1852 (1L << PG_swapbacked) |
1853 (1L << PG_mlocked) |
1854 (1L << PG_uptodate) |
1857 (1L << PG_unevictable) |
1861 * After clearing PageTail the gup refcount can be released.
1862 * Page flags also must be visible before we make the page non-compound.
1866 clear_compound_head(page_tail);
1868 if (page_is_young(head))
1869 set_page_young(page_tail);
1870 if (page_is_idle(head))
1871 set_page_idle(page_tail);
1873 /* ->mapping in first tail page is compound_mapcount */
1874 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
1876 page_tail->mapping = head->mapping;
1878 page_tail->index = head->index + tail;
1879 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
1880 lru_add_page_tail(head, page_tail, lruvec, list);
1883 static void __split_huge_page(struct page *page, struct list_head *list,
1884 unsigned long flags)
1886 struct page *head = compound_head(page);
1887 struct zone *zone = page_zone(head);
1888 struct lruvec *lruvec;
1892 lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
1894 /* complete memcg works before add pages to LRU */
1895 mem_cgroup_split_huge_fixup(head);
1897 if (!PageAnon(page))
1898 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
1900 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1901 __split_huge_page_tail(head, i, lruvec, list);
1902 /* Some pages can be beyond i_size: drop them from page cache */
1903 if (head[i].index >= end) {
1904 __ClearPageDirty(head + i);
1905 __delete_from_page_cache(head + i, NULL);
1906 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
1907 shmem_uncharge(head->mapping->host, 1);
1912 ClearPageCompound(head);
1913 /* See comment in __split_huge_page_tail() */
1914 if (PageAnon(head)) {
1917 /* Additional pin to radix tree */
1918 page_ref_add(head, 2);
1919 spin_unlock(&head->mapping->tree_lock);
1922 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
1924 unfreeze_page(head);
1926 for (i = 0; i < HPAGE_PMD_NR; i++) {
1927 struct page *subpage = head + i;
1928 if (subpage == page)
1930 unlock_page(subpage);
1933 * Subpages may be freed if there wasn't any mapping
1934 * like if add_to_swap() is running on a lru page that
1935 * had its mapping zapped. And freeing these pages
1936 * requires taking the lru_lock so we do the put_page
1937 * of the tail pages after the split is complete.
1943 int total_mapcount(struct page *page)
1945 int i, compound, ret;
1947 VM_BUG_ON_PAGE(PageTail(page), page);
1949 if (likely(!PageCompound(page)))
1950 return atomic_read(&page->_mapcount) + 1;
1952 compound = compound_mapcount(page);
1956 for (i = 0; i < HPAGE_PMD_NR; i++)
1957 ret += atomic_read(&page[i]._mapcount) + 1;
1958 /* File pages has compound_mapcount included in _mapcount */
1959 if (!PageAnon(page))
1960 return ret - compound * HPAGE_PMD_NR;
1961 if (PageDoubleMap(page))
1962 ret -= HPAGE_PMD_NR;
1967 * This calculates accurately how many mappings a transparent hugepage
1968 * has (unlike page_mapcount() which isn't fully accurate). This full
1969 * accuracy is primarily needed to know if copy-on-write faults can
1970 * reuse the page and change the mapping to read-write instead of
1971 * copying them. At the same time this returns the total_mapcount too.
1973 * The function returns the highest mapcount any one of the subpages
1974 * has. If the return value is one, even if different processes are
1975 * mapping different subpages of the transparent hugepage, they can
1976 * all reuse it, because each process is reusing a different subpage.
1978 * The total_mapcount is instead counting all virtual mappings of the
1979 * subpages. If the total_mapcount is equal to "one", it tells the
1980 * caller all mappings belong to the same "mm" and in turn the
1981 * anon_vma of the transparent hugepage can become the vma->anon_vma
1982 * local one as no other process may be mapping any of the subpages.
1984 * It would be more accurate to replace page_mapcount() with
1985 * page_trans_huge_mapcount(), however we only use
1986 * page_trans_huge_mapcount() in the copy-on-write faults where we
1987 * need full accuracy to avoid breaking page pinning, because
1988 * page_trans_huge_mapcount() is slower than page_mapcount().
1990 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
1992 int i, ret, _total_mapcount, mapcount;
1994 /* hugetlbfs shouldn't call it */
1995 VM_BUG_ON_PAGE(PageHuge(page), page);
1997 if (likely(!PageTransCompound(page))) {
1998 mapcount = atomic_read(&page->_mapcount) + 1;
2000 *total_mapcount = mapcount;
2004 page = compound_head(page);
2006 _total_mapcount = ret = 0;
2007 for (i = 0; i < HPAGE_PMD_NR; i++) {
2008 mapcount = atomic_read(&page[i]._mapcount) + 1;
2009 ret = max(ret, mapcount);
2010 _total_mapcount += mapcount;
2012 if (PageDoubleMap(page)) {
2014 _total_mapcount -= HPAGE_PMD_NR;
2016 mapcount = compound_mapcount(page);
2018 _total_mapcount += mapcount;
2020 *total_mapcount = _total_mapcount;
2025 * This function splits huge page into normal pages. @page can point to any
2026 * subpage of huge page to split. Split doesn't change the position of @page.
2028 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2029 * The huge page must be locked.
2031 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2033 * Both head page and tail pages will inherit mapping, flags, and so on from
2036 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2037 * they are not mapped.
2039 * Returns 0 if the hugepage is split successfully.
2040 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2043 int split_huge_page_to_list(struct page *page, struct list_head *list)
2045 struct page *head = compound_head(page);
2046 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2047 struct anon_vma *anon_vma = NULL;
2048 struct address_space *mapping = NULL;
2049 int count, mapcount, extra_pins, ret;
2051 unsigned long flags;
2053 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2054 VM_BUG_ON_PAGE(!PageLocked(page), page);
2055 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2056 VM_BUG_ON_PAGE(!PageCompound(page), page);
2058 if (PageAnon(head)) {
2060 * The caller does not necessarily hold an mmap_sem that would
2061 * prevent the anon_vma disappearing so we first we take a
2062 * reference to it and then lock the anon_vma for write. This
2063 * is similar to page_lock_anon_vma_read except the write lock
2064 * is taken to serialise against parallel split or collapse
2067 anon_vma = page_get_anon_vma(head);
2074 anon_vma_lock_write(anon_vma);
2076 mapping = head->mapping;
2084 /* Addidional pins from radix tree */
2085 extra_pins = HPAGE_PMD_NR;
2087 i_mmap_lock_read(mapping);
2091 * Racy check if we can split the page, before freeze_page() will
2094 if (total_mapcount(head) != page_count(head) - extra_pins - 1) {
2099 mlocked = PageMlocked(page);
2101 VM_BUG_ON_PAGE(compound_mapcount(head), head);
2103 /* Make sure the page is not on per-CPU pagevec as it takes pin */
2107 /* prevent PageLRU to go away from under us, and freeze lru stats */
2108 spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2113 spin_lock(&mapping->tree_lock);
2114 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2117 * Check if the head page is present in radix tree.
2118 * We assume all tail are present too, if head is there.
2120 if (radix_tree_deref_slot_protected(pslot,
2121 &mapping->tree_lock) != head)
2125 /* Prevent deferred_split_scan() touching ->_refcount */
2126 spin_lock(&pgdata->split_queue_lock);
2127 count = page_count(head);
2128 mapcount = total_mapcount(head);
2129 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2130 if (!list_empty(page_deferred_list(head))) {
2131 pgdata->split_queue_len--;
2132 list_del(page_deferred_list(head));
2135 __dec_node_page_state(page, NR_SHMEM_THPS);
2136 spin_unlock(&pgdata->split_queue_lock);
2137 __split_huge_page(page, list, flags);
2140 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2141 pr_alert("total_mapcount: %u, page_count(): %u\n",
2144 dump_page(head, NULL);
2145 dump_page(page, "total_mapcount(head) > 0");
2148 spin_unlock(&pgdata->split_queue_lock);
2150 spin_unlock(&mapping->tree_lock);
2151 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2152 unfreeze_page(head);
2158 anon_vma_unlock_write(anon_vma);
2159 put_anon_vma(anon_vma);
2162 i_mmap_unlock_read(mapping);
2164 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2168 void free_transhuge_page(struct page *page)
2170 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2171 unsigned long flags;
2173 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2174 if (!list_empty(page_deferred_list(page))) {
2175 pgdata->split_queue_len--;
2176 list_del(page_deferred_list(page));
2178 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2179 free_compound_page(page);
2182 void deferred_split_huge_page(struct page *page)
2184 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2185 unsigned long flags;
2187 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2189 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2190 if (list_empty(page_deferred_list(page))) {
2191 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2192 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2193 pgdata->split_queue_len++;
2195 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2198 static unsigned long deferred_split_count(struct shrinker *shrink,
2199 struct shrink_control *sc)
2201 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2202 return ACCESS_ONCE(pgdata->split_queue_len);
2205 static unsigned long deferred_split_scan(struct shrinker *shrink,
2206 struct shrink_control *sc)
2208 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2209 unsigned long flags;
2210 LIST_HEAD(list), *pos, *next;
2214 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2215 /* Take pin on all head pages to avoid freeing them under us */
2216 list_for_each_safe(pos, next, &pgdata->split_queue) {
2217 page = list_entry((void *)pos, struct page, mapping);
2218 page = compound_head(page);
2219 if (get_page_unless_zero(page)) {
2220 list_move(page_deferred_list(page), &list);
2222 /* We lost race with put_compound_page() */
2223 list_del_init(page_deferred_list(page));
2224 pgdata->split_queue_len--;
2226 if (!--sc->nr_to_scan)
2229 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2231 list_for_each_safe(pos, next, &list) {
2232 page = list_entry((void *)pos, struct page, mapping);
2234 /* split_huge_page() removes page from list on success */
2235 if (!split_huge_page(page))
2241 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2242 list_splice_tail(&list, &pgdata->split_queue);
2243 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2246 * Stop shrinker if we didn't split any page, but the queue is empty.
2247 * This can happen if pages were freed under us.
2249 if (!split && list_empty(&pgdata->split_queue))
2254 static struct shrinker deferred_split_shrinker = {
2255 .count_objects = deferred_split_count,
2256 .scan_objects = deferred_split_scan,
2257 .seeks = DEFAULT_SEEKS,
2258 .flags = SHRINKER_NUMA_AWARE,
2261 #ifdef CONFIG_DEBUG_FS
2262 static int split_huge_pages_set(void *data, u64 val)
2266 unsigned long pfn, max_zone_pfn;
2267 unsigned long total = 0, split = 0;
2272 for_each_populated_zone(zone) {
2273 max_zone_pfn = zone_end_pfn(zone);
2274 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2275 if (!pfn_valid(pfn))
2278 page = pfn_to_page(pfn);
2279 if (!get_page_unless_zero(page))
2282 if (zone != page_zone(page))
2285 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2290 if (!split_huge_page(page))
2298 pr_info("%lu of %lu THP split\n", split, total);
2302 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2305 static int __init split_huge_pages_debugfs(void)
2309 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2310 &split_huge_pages_fops);
2312 pr_warn("Failed to create split_huge_pages in debugfs");
2315 late_initcall(split_huge_pages_debugfs);