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/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>
38 #include <asm/pgalloc.h>
42 * By default transparent hugepage support is disabled in order that avoid
43 * to risk increase the memory footprint of applications without a guaranteed
44 * benefit. When transparent hugepage support is enabled, is for all mappings,
45 * and khugepaged scans all mappings.
46 * Defrag is invoked by khugepaged hugepage allocations and by page faults
47 * for all hugepage allocations.
49 unsigned long transparent_hugepage_flags __read_mostly =
50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
51 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
54 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
56 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
57 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
58 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
60 static struct shrinker deferred_split_shrinker;
62 static atomic_t huge_zero_refcount;
63 struct page *huge_zero_page __read_mostly;
65 static struct page *get_huge_zero_page(void)
67 struct page *zero_page;
69 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
70 return READ_ONCE(huge_zero_page);
72 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
75 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
78 count_vm_event(THP_ZERO_PAGE_ALLOC);
80 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
82 __free_pages(zero_page, compound_order(zero_page));
86 /* We take additional reference here. It will be put back by shrinker */
87 atomic_set(&huge_zero_refcount, 2);
89 return READ_ONCE(huge_zero_page);
92 static void put_huge_zero_page(void)
95 * Counter should never go to zero here. Only shrinker can put
98 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
101 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
103 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
104 return READ_ONCE(huge_zero_page);
106 if (!get_huge_zero_page())
109 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
110 put_huge_zero_page();
112 return READ_ONCE(huge_zero_page);
115 void mm_put_huge_zero_page(struct mm_struct *mm)
117 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
118 put_huge_zero_page();
121 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
122 struct shrink_control *sc)
124 /* we can free zero page only if last reference remains */
125 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
128 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
129 struct shrink_control *sc)
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));
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,
148 static ssize_t enabled_show(struct kobject *kobj,
149 struct kobj_attribute *attr, char *buf)
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");
156 return sprintf(buf, "always madvise [never]\n");
159 static ssize_t enabled_store(struct kobject *kobj,
160 struct kobj_attribute *attr,
161 const char *buf, size_t count)
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);
181 int err = start_stop_khugepaged();
187 static struct kobj_attribute enabled_attr =
188 __ATTR(enabled, 0644, enabled_show, enabled_store);
190 ssize_t single_hugepage_flag_show(struct kobject *kobj,
191 struct kobj_attribute *attr, char *buf,
192 enum transparent_hugepage_flag flag)
194 return sprintf(buf, "%d\n",
195 !!test_bit(flag, &transparent_hugepage_flags));
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)
206 ret = kstrtoul(buf, 10, &value);
213 set_bit(flag, &transparent_hugepage_flags);
215 clear_bit(flag, &transparent_hugepage_flags);
220 static ssize_t defrag_show(struct kobject *kobj,
221 struct kobj_attribute *attr, char *buf)
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");
234 static ssize_t defrag_store(struct kobject *kobj,
235 struct kobj_attribute *attr,
236 const char *buf, size_t count)
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);
273 static struct kobj_attribute defrag_attr =
274 __ATTR(defrag, 0644, defrag_show, defrag_store);
276 static ssize_t use_zero_page_show(struct kobject *kobj,
277 struct kobj_attribute *attr, char *buf)
279 return single_hugepage_flag_show(kobj, attr, buf,
280 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
282 static ssize_t use_zero_page_store(struct kobject *kobj,
283 struct kobj_attribute *attr, const char *buf, size_t count)
285 return single_hugepage_flag_store(kobj, attr, buf, count,
286 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
288 static struct kobj_attribute use_zero_page_attr =
289 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
291 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
292 struct kobj_attribute *attr, char *buf)
294 return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
296 static struct kobj_attribute hpage_pmd_size_attr =
297 __ATTR_RO(hpage_pmd_size);
299 #ifdef CONFIG_DEBUG_VM
300 static ssize_t debug_cow_show(struct kobject *kobj,
301 struct kobj_attribute *attr, char *buf)
303 return single_hugepage_flag_show(kobj, attr, buf,
304 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
306 static ssize_t debug_cow_store(struct kobject *kobj,
307 struct kobj_attribute *attr,
308 const char *buf, size_t count)
310 return single_hugepage_flag_store(kobj, attr, buf, count,
311 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
313 static struct kobj_attribute debug_cow_attr =
314 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
315 #endif /* CONFIG_DEBUG_VM */
317 static struct attribute *hugepage_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,
325 #ifdef CONFIG_DEBUG_VM
326 &debug_cow_attr.attr,
331 static const struct attribute_group hugepage_attr_group = {
332 .attrs = hugepage_attr,
335 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
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");
345 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
347 pr_err("failed to register transparent hugepage group\n");
351 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
353 pr_err("failed to register transparent hugepage group\n");
354 goto remove_hp_group;
360 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
362 kobject_put(*hugepage_kobj);
366 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
368 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
369 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
370 kobject_put(hugepage_kobj);
373 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
378 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
381 #endif /* CONFIG_SYSFS */
383 static int __init hugepage_init(void)
386 struct kobject *hugepage_kobj;
388 if (!has_transparent_hugepage()) {
389 transparent_hugepage_flags = 0;
394 * hugepages can't be allocated by the buddy allocator
396 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
398 * we use page->mapping and page->index in second tail page
399 * as list_head: assuming THP order >= 2
401 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
403 err = hugepage_init_sysfs(&hugepage_kobj);
407 err = khugepaged_init();
411 err = register_shrinker(&huge_zero_page_shrinker);
413 goto err_hzp_shrinker;
414 err = register_shrinker(&deferred_split_shrinker);
416 goto err_split_shrinker;
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.
423 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
424 transparent_hugepage_flags = 0;
428 err = start_stop_khugepaged();
434 unregister_shrinker(&deferred_split_shrinker);
436 unregister_shrinker(&huge_zero_page_shrinker);
438 khugepaged_destroy();
440 hugepage_exit_sysfs(hugepage_kobj);
444 subsys_initcall(hugepage_init);
446 static int __init setup_transparent_hugepage(char *str)
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);
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);
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);
472 pr_warn("transparent_hugepage= cannot parse, ignored\n");
475 __setup("transparent_hugepage=", setup_transparent_hugepage);
477 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
479 if (likely(vma->vm_flags & VM_WRITE))
480 pmd = pmd_mkwrite(pmd);
484 static inline struct list_head *page_deferred_list(struct page *page)
487 * ->lru in the tail pages is occupied by compound_head.
488 * Let's use ->mapping + ->index in the second tail page as list_head.
490 return (struct list_head *)&page[2].mapping;
493 void prep_transhuge_page(struct page *page)
496 * we use page->mapping and page->indexlru in second tail page
497 * as list_head: assuming THP order >= 2
500 INIT_LIST_HEAD(page_deferred_list(page));
501 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
504 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
505 loff_t off, unsigned long flags, unsigned long size)
508 loff_t off_end = off + len;
509 loff_t off_align = round_up(off, size);
510 unsigned long len_pad;
512 if (off_end <= off_align || (off_end - off_align) < size)
515 len_pad = len + size;
516 if (len_pad < len || (off + len_pad) < off)
519 addr = current->mm->get_unmapped_area(filp, 0, len_pad,
520 off >> PAGE_SHIFT, flags);
521 if (IS_ERR_VALUE(addr))
524 addr += (off - addr) & (size - 1);
528 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
529 unsigned long len, unsigned long pgoff, unsigned long flags)
531 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
535 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
538 addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
543 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
545 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
547 static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
550 struct vm_area_struct *vma = vmf->vma;
551 struct mem_cgroup *memcg;
553 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
556 VM_BUG_ON_PAGE(!PageCompound(page), page);
558 if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
560 count_vm_event(THP_FAULT_FALLBACK);
561 return VM_FAULT_FALLBACK;
564 pgtable = pte_alloc_one(vma->vm_mm, haddr);
565 if (unlikely(!pgtable)) {
570 clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
572 * The memory barrier inside __SetPageUptodate makes sure that
573 * clear_huge_page writes become visible before the set_pmd_at()
576 __SetPageUptodate(page);
578 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
579 if (unlikely(!pmd_none(*vmf->pmd))) {
584 ret = check_stable_address_space(vma->vm_mm);
588 /* Deliver the page fault to userland */
589 if (userfaultfd_missing(vma)) {
592 spin_unlock(vmf->ptl);
593 mem_cgroup_cancel_charge(page, memcg, true);
595 pte_free(vma->vm_mm, pgtable);
596 ret = handle_userfault(vmf, VM_UFFD_MISSING);
597 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
601 entry = mk_huge_pmd(page, vma->vm_page_prot);
602 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
603 page_add_new_anon_rmap(page, vma, haddr, true);
604 mem_cgroup_commit_charge(page, memcg, false, true);
605 lru_cache_add_active_or_unevictable(page, vma);
606 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
607 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
608 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
609 atomic_long_inc(&vma->vm_mm->nr_ptes);
610 spin_unlock(vmf->ptl);
611 count_vm_event(THP_FAULT_ALLOC);
616 spin_unlock(vmf->ptl);
619 pte_free(vma->vm_mm, pgtable);
620 mem_cgroup_cancel_charge(page, memcg, true);
627 * always: directly stall for all thp allocations
628 * defer: wake kswapd and fail if not immediately available
629 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
630 * fail if not immediately available
631 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
633 * never: never stall for any thp allocation
635 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
637 const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
639 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
640 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
641 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
642 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
643 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
644 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
645 __GFP_KSWAPD_RECLAIM);
646 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
647 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
649 return GFP_TRANSHUGE_LIGHT;
652 /* Caller must hold page table lock. */
653 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
654 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
655 struct page *zero_page)
660 entry = mk_pmd(zero_page, vma->vm_page_prot);
661 entry = pmd_mkhuge(entry);
663 pgtable_trans_huge_deposit(mm, pmd, pgtable);
664 set_pmd_at(mm, haddr, pmd, entry);
665 atomic_long_inc(&mm->nr_ptes);
669 int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
671 struct vm_area_struct *vma = vmf->vma;
674 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
676 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
677 return VM_FAULT_FALLBACK;
678 if (unlikely(anon_vma_prepare(vma)))
680 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
682 if (!(vmf->flags & FAULT_FLAG_WRITE) &&
683 !mm_forbids_zeropage(vma->vm_mm) &&
684 transparent_hugepage_use_zero_page()) {
686 struct page *zero_page;
689 pgtable = pte_alloc_one(vma->vm_mm, haddr);
690 if (unlikely(!pgtable))
692 zero_page = mm_get_huge_zero_page(vma->vm_mm);
693 if (unlikely(!zero_page)) {
694 pte_free(vma->vm_mm, pgtable);
695 count_vm_event(THP_FAULT_FALLBACK);
696 return VM_FAULT_FALLBACK;
698 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
701 if (pmd_none(*vmf->pmd)) {
702 ret = check_stable_address_space(vma->vm_mm);
704 spin_unlock(vmf->ptl);
705 } else if (userfaultfd_missing(vma)) {
706 spin_unlock(vmf->ptl);
707 ret = handle_userfault(vmf, VM_UFFD_MISSING);
708 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
710 set_huge_zero_page(pgtable, vma->vm_mm, vma,
711 haddr, vmf->pmd, zero_page);
712 spin_unlock(vmf->ptl);
716 spin_unlock(vmf->ptl);
718 pte_free(vma->vm_mm, pgtable);
721 gfp = alloc_hugepage_direct_gfpmask(vma);
722 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
723 if (unlikely(!page)) {
724 count_vm_event(THP_FAULT_FALLBACK);
725 return VM_FAULT_FALLBACK;
727 prep_transhuge_page(page);
728 return __do_huge_pmd_anonymous_page(vmf, page, gfp);
731 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
732 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
735 struct mm_struct *mm = vma->vm_mm;
739 ptl = pmd_lock(mm, pmd);
740 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
741 if (pfn_t_devmap(pfn))
742 entry = pmd_mkdevmap(entry);
744 entry = pmd_mkyoung(pmd_mkdirty(entry));
745 entry = maybe_pmd_mkwrite(entry, vma);
749 pgtable_trans_huge_deposit(mm, pmd, pgtable);
750 atomic_long_inc(&mm->nr_ptes);
753 set_pmd_at(mm, addr, pmd, entry);
754 update_mmu_cache_pmd(vma, addr, pmd);
758 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
759 pmd_t *pmd, pfn_t pfn, bool write)
761 pgprot_t pgprot = vma->vm_page_prot;
762 pgtable_t pgtable = NULL;
764 * If we had pmd_special, we could avoid all these restrictions,
765 * but we need to be consistent with PTEs and architectures that
766 * can't support a 'special' bit.
768 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
769 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
770 (VM_PFNMAP|VM_MIXEDMAP));
771 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
772 BUG_ON(!pfn_t_devmap(pfn));
774 if (addr < vma->vm_start || addr >= vma->vm_end)
775 return VM_FAULT_SIGBUS;
777 if (arch_needs_pgtable_deposit()) {
778 pgtable = pte_alloc_one(vma->vm_mm, addr);
783 track_pfn_insert(vma, &pgprot, pfn);
785 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
786 return VM_FAULT_NOPAGE;
788 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
790 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
791 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
793 if (likely(vma->vm_flags & VM_WRITE))
794 pud = pud_mkwrite(pud);
798 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
799 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
801 struct mm_struct *mm = vma->vm_mm;
805 ptl = pud_lock(mm, pud);
806 entry = pud_mkhuge(pfn_t_pud(pfn, prot));
807 if (pfn_t_devmap(pfn))
808 entry = pud_mkdevmap(entry);
810 entry = pud_mkyoung(pud_mkdirty(entry));
811 entry = maybe_pud_mkwrite(entry, vma);
813 set_pud_at(mm, addr, pud, entry);
814 update_mmu_cache_pud(vma, addr, pud);
818 int vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
819 pud_t *pud, pfn_t pfn, bool write)
821 pgprot_t pgprot = vma->vm_page_prot;
823 * If we had pud_special, we could avoid all these restrictions,
824 * but we need to be consistent with PTEs and architectures that
825 * can't support a 'special' bit.
827 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
828 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
829 (VM_PFNMAP|VM_MIXEDMAP));
830 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
831 BUG_ON(!pfn_t_devmap(pfn));
833 if (addr < vma->vm_start || addr >= vma->vm_end)
834 return VM_FAULT_SIGBUS;
836 track_pfn_insert(vma, &pgprot, pfn);
838 insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
839 return VM_FAULT_NOPAGE;
841 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
842 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
844 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
850 * We should set the dirty bit only for FOLL_WRITE but for now
851 * the dirty bit in the pmd is meaningless. And if the dirty
852 * bit will become meaningful and we'll only set it with
853 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
854 * set the young bit, instead of the current set_pmd_at.
856 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
857 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
859 update_mmu_cache_pmd(vma, addr, pmd);
862 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
863 pmd_t *pmd, int flags)
865 unsigned long pfn = pmd_pfn(*pmd);
866 struct mm_struct *mm = vma->vm_mm;
867 struct dev_pagemap *pgmap;
870 assert_spin_locked(pmd_lockptr(mm, pmd));
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.
876 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
878 if (flags & FOLL_WRITE && !pmd_write(*pmd))
881 if (pmd_present(*pmd) && pmd_devmap(*pmd))
886 if (flags & FOLL_TOUCH)
887 touch_pmd(vma, addr, pmd);
890 * device mapped pages can only be returned if the
891 * caller will manage the page reference count.
893 if (!(flags & FOLL_GET))
894 return ERR_PTR(-EEXIST);
896 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
897 pgmap = get_dev_pagemap(pfn, NULL);
899 return ERR_PTR(-EFAULT);
900 page = pfn_to_page(pfn);
902 put_dev_pagemap(pgmap);
907 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
908 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
909 struct vm_area_struct *vma)
911 spinlock_t *dst_ptl, *src_ptl;
912 struct page *src_page;
914 pgtable_t pgtable = NULL;
917 /* Skip if can be re-fill on fault */
918 if (!vma_is_anonymous(vma))
921 pgtable = pte_alloc_one(dst_mm, addr);
922 if (unlikely(!pgtable))
925 dst_ptl = pmd_lock(dst_mm, dst_pmd);
926 src_ptl = pmd_lockptr(src_mm, src_pmd);
927 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
931 if (unlikely(!pmd_trans_huge(pmd))) {
932 pte_free(dst_mm, pgtable);
936 * When page table lock is held, the huge zero pmd should not be
937 * under splitting since we don't split the page itself, only pmd to
940 if (is_huge_zero_pmd(pmd)) {
941 struct page *zero_page;
943 * get_huge_zero_page() will never allocate a new page here,
944 * since we already have a zero page to copy. It just takes a
947 zero_page = mm_get_huge_zero_page(dst_mm);
948 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
954 src_page = pmd_page(pmd);
955 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
957 page_dup_rmap(src_page, true);
958 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
959 atomic_long_inc(&dst_mm->nr_ptes);
960 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
962 pmdp_set_wrprotect(src_mm, addr, src_pmd);
963 pmd = pmd_mkold(pmd_wrprotect(pmd));
964 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
968 spin_unlock(src_ptl);
969 spin_unlock(dst_ptl);
974 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
975 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
981 * We should set the dirty bit only for FOLL_WRITE but for now
982 * the dirty bit in the pud is meaningless. And if the dirty
983 * bit will become meaningful and we'll only set it with
984 * FOLL_WRITE, an atomic set_bit will be required on the pud to
985 * set the young bit, instead of the current set_pud_at.
987 _pud = pud_mkyoung(pud_mkdirty(*pud));
988 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
990 update_mmu_cache_pud(vma, addr, pud);
993 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
994 pud_t *pud, int flags)
996 unsigned long pfn = pud_pfn(*pud);
997 struct mm_struct *mm = vma->vm_mm;
998 struct dev_pagemap *pgmap;
1001 assert_spin_locked(pud_lockptr(mm, pud));
1003 if (flags & FOLL_WRITE && !pud_write(*pud))
1006 if (pud_present(*pud) && pud_devmap(*pud))
1011 if (flags & FOLL_TOUCH)
1012 touch_pud(vma, addr, pud);
1015 * device mapped pages can only be returned if the
1016 * caller will manage the page reference count.
1018 if (!(flags & FOLL_GET))
1019 return ERR_PTR(-EEXIST);
1021 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1022 pgmap = get_dev_pagemap(pfn, NULL);
1024 return ERR_PTR(-EFAULT);
1025 page = pfn_to_page(pfn);
1027 put_dev_pagemap(pgmap);
1032 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1033 pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1034 struct vm_area_struct *vma)
1036 spinlock_t *dst_ptl, *src_ptl;
1040 dst_ptl = pud_lock(dst_mm, dst_pud);
1041 src_ptl = pud_lockptr(src_mm, src_pud);
1042 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1046 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1050 * When page table lock is held, the huge zero pud should not be
1051 * under splitting since we don't split the page itself, only pud to
1054 if (is_huge_zero_pud(pud)) {
1055 /* No huge zero pud yet */
1058 pudp_set_wrprotect(src_mm, addr, src_pud);
1059 pud = pud_mkold(pud_wrprotect(pud));
1060 set_pud_at(dst_mm, addr, dst_pud, pud);
1064 spin_unlock(src_ptl);
1065 spin_unlock(dst_ptl);
1069 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1072 unsigned long haddr;
1073 bool write = vmf->flags & FAULT_FLAG_WRITE;
1075 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1076 if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1079 entry = pud_mkyoung(orig_pud);
1081 entry = pud_mkdirty(entry);
1082 haddr = vmf->address & HPAGE_PUD_MASK;
1083 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1084 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1087 spin_unlock(vmf->ptl);
1089 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1091 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1094 unsigned long haddr;
1095 bool write = vmf->flags & FAULT_FLAG_WRITE;
1097 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1098 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1101 entry = pmd_mkyoung(orig_pmd);
1103 entry = pmd_mkdirty(entry);
1104 haddr = vmf->address & HPAGE_PMD_MASK;
1105 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1106 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1109 spin_unlock(vmf->ptl);
1112 static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
1115 struct vm_area_struct *vma = vmf->vma;
1116 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1117 struct mem_cgroup *memcg;
1121 struct page **pages;
1122 unsigned long mmun_start; /* For mmu_notifiers */
1123 unsigned long mmun_end; /* For mmu_notifiers */
1125 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1127 if (unlikely(!pages)) {
1128 ret |= VM_FAULT_OOM;
1132 for (i = 0; i < HPAGE_PMD_NR; i++) {
1133 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1134 vmf->address, page_to_nid(page));
1135 if (unlikely(!pages[i] ||
1136 mem_cgroup_try_charge(pages[i], vma->vm_mm,
1137 GFP_KERNEL, &memcg, false))) {
1141 memcg = (void *)page_private(pages[i]);
1142 set_page_private(pages[i], 0);
1143 mem_cgroup_cancel_charge(pages[i], memcg,
1148 ret |= VM_FAULT_OOM;
1151 set_page_private(pages[i], (unsigned long)memcg);
1154 for (i = 0; i < HPAGE_PMD_NR; i++) {
1155 copy_user_highpage(pages[i], page + i,
1156 haddr + PAGE_SIZE * i, vma);
1157 __SetPageUptodate(pages[i]);
1162 mmun_end = haddr + HPAGE_PMD_SIZE;
1163 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1165 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1166 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1167 goto out_free_pages;
1168 VM_BUG_ON_PAGE(!PageHead(page), page);
1170 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1171 /* leave pmd empty until pte is filled */
1173 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1174 pmd_populate(vma->vm_mm, &_pmd, pgtable);
1176 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1178 entry = mk_pte(pages[i], vma->vm_page_prot);
1179 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1180 memcg = (void *)page_private(pages[i]);
1181 set_page_private(pages[i], 0);
1182 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1183 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1184 lru_cache_add_active_or_unevictable(pages[i], vma);
1185 vmf->pte = pte_offset_map(&_pmd, haddr);
1186 VM_BUG_ON(!pte_none(*vmf->pte));
1187 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1188 pte_unmap(vmf->pte);
1192 smp_wmb(); /* make pte visible before pmd */
1193 pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1194 page_remove_rmap(page, true);
1195 spin_unlock(vmf->ptl);
1197 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1199 ret |= VM_FAULT_WRITE;
1206 spin_unlock(vmf->ptl);
1207 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1208 for (i = 0; i < HPAGE_PMD_NR; i++) {
1209 memcg = (void *)page_private(pages[i]);
1210 set_page_private(pages[i], 0);
1211 mem_cgroup_cancel_charge(pages[i], memcg, false);
1218 int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1220 struct vm_area_struct *vma = vmf->vma;
1221 struct page *page = NULL, *new_page;
1222 struct mem_cgroup *memcg;
1223 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1224 unsigned long mmun_start; /* For mmu_notifiers */
1225 unsigned long mmun_end; /* For mmu_notifiers */
1226 gfp_t huge_gfp; /* for allocation and charge */
1229 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1230 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1231 if (is_huge_zero_pmd(orig_pmd))
1233 spin_lock(vmf->ptl);
1234 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1237 page = pmd_page(orig_pmd);
1238 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1240 * We can only reuse the page if nobody else maps the huge page or it's
1243 if (!trylock_page(page)) {
1245 spin_unlock(vmf->ptl);
1247 spin_lock(vmf->ptl);
1248 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1255 if (reuse_swap_page(page, NULL)) {
1257 entry = pmd_mkyoung(orig_pmd);
1258 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1259 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1260 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1261 ret |= VM_FAULT_WRITE;
1267 spin_unlock(vmf->ptl);
1269 if (transparent_hugepage_enabled(vma) &&
1270 !transparent_hugepage_debug_cow()) {
1271 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1272 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1276 if (likely(new_page)) {
1277 prep_transhuge_page(new_page);
1280 split_huge_pmd(vma, vmf->pmd, vmf->address);
1281 ret |= VM_FAULT_FALLBACK;
1283 ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1284 if (ret & VM_FAULT_OOM) {
1285 split_huge_pmd(vma, vmf->pmd, vmf->address);
1286 ret |= VM_FAULT_FALLBACK;
1290 count_vm_event(THP_FAULT_FALLBACK);
1294 if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1295 huge_gfp, &memcg, true))) {
1297 split_huge_pmd(vma, vmf->pmd, vmf->address);
1300 ret |= VM_FAULT_FALLBACK;
1301 count_vm_event(THP_FAULT_FALLBACK);
1305 count_vm_event(THP_FAULT_ALLOC);
1308 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1310 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1311 __SetPageUptodate(new_page);
1314 mmun_end = haddr + HPAGE_PMD_SIZE;
1315 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1317 spin_lock(vmf->ptl);
1320 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1321 spin_unlock(vmf->ptl);
1322 mem_cgroup_cancel_charge(new_page, memcg, true);
1327 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1328 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1329 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1330 page_add_new_anon_rmap(new_page, vma, haddr, true);
1331 mem_cgroup_commit_charge(new_page, memcg, false, true);
1332 lru_cache_add_active_or_unevictable(new_page, vma);
1333 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1334 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1336 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1338 VM_BUG_ON_PAGE(!PageHead(page), page);
1339 page_remove_rmap(page, true);
1342 ret |= VM_FAULT_WRITE;
1344 spin_unlock(vmf->ptl);
1346 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1350 spin_unlock(vmf->ptl);
1355 * FOLL_FORCE can write to even unwritable pmd's, but only
1356 * after we've gone through a COW cycle and they are dirty.
1358 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1360 return pmd_write(pmd) ||
1361 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1364 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1369 struct mm_struct *mm = vma->vm_mm;
1370 struct page *page = NULL;
1372 assert_spin_locked(pmd_lockptr(mm, pmd));
1374 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1377 /* Avoid dumping huge zero page */
1378 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1379 return ERR_PTR(-EFAULT);
1381 /* Full NUMA hinting faults to serialise migration in fault paths */
1382 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1385 page = pmd_page(*pmd);
1386 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1387 if (flags & FOLL_TOUCH)
1388 touch_pmd(vma, addr, pmd);
1389 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1391 * We don't mlock() pte-mapped THPs. This way we can avoid
1392 * leaking mlocked pages into non-VM_LOCKED VMAs.
1396 * In most cases the pmd is the only mapping of the page as we
1397 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1398 * writable private mappings in populate_vma_page_range().
1400 * The only scenario when we have the page shared here is if we
1401 * mlocking read-only mapping shared over fork(). We skip
1402 * mlocking such pages.
1406 * We can expect PageDoubleMap() to be stable under page lock:
1407 * for file pages we set it in page_add_file_rmap(), which
1408 * requires page to be locked.
1411 if (PageAnon(page) && compound_mapcount(page) != 1)
1413 if (PageDoubleMap(page) || !page->mapping)
1415 if (!trylock_page(page))
1418 if (page->mapping && !PageDoubleMap(page))
1419 mlock_vma_page(page);
1423 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1424 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1425 if (flags & FOLL_GET)
1432 /* NUMA hinting page fault entry point for trans huge pmds */
1433 int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1435 struct vm_area_struct *vma = vmf->vma;
1436 struct anon_vma *anon_vma = NULL;
1438 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1439 int page_nid = -1, this_nid = numa_node_id();
1440 int target_nid, last_cpupid = -1;
1442 bool migrated = false;
1446 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1447 if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1451 * If there are potential migrations, wait for completion and retry
1452 * without disrupting NUMA hinting information. Do not relock and
1453 * check_same as the page may no longer be mapped.
1455 if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1456 page = pmd_page(*vmf->pmd);
1457 if (!get_page_unless_zero(page))
1459 spin_unlock(vmf->ptl);
1460 wait_on_page_locked(page);
1465 page = pmd_page(pmd);
1466 BUG_ON(is_huge_zero_page(page));
1467 page_nid = page_to_nid(page);
1468 last_cpupid = page_cpupid_last(page);
1469 count_vm_numa_event(NUMA_HINT_FAULTS);
1470 if (page_nid == this_nid) {
1471 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1472 flags |= TNF_FAULT_LOCAL;
1475 /* See similar comment in do_numa_page for explanation */
1476 if (!pmd_savedwrite(pmd))
1477 flags |= TNF_NO_GROUP;
1480 * Acquire the page lock to serialise THP migrations but avoid dropping
1481 * page_table_lock if at all possible
1483 page_locked = trylock_page(page);
1484 target_nid = mpol_misplaced(page, vma, haddr);
1485 if (target_nid == -1) {
1486 /* If the page was locked, there are no parallel migrations */
1491 /* Migration could have started since the pmd_trans_migrating check */
1494 if (!get_page_unless_zero(page))
1496 spin_unlock(vmf->ptl);
1497 wait_on_page_locked(page);
1503 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1504 * to serialises splits
1507 spin_unlock(vmf->ptl);
1508 anon_vma = page_lock_anon_vma_read(page);
1510 /* Confirm the PMD did not change while page_table_lock was released */
1511 spin_lock(vmf->ptl);
1512 if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1519 /* Bail if we fail to protect against THP splits for any reason */
1520 if (unlikely(!anon_vma)) {
1527 * Since we took the NUMA fault, we must have observed the !accessible
1528 * bit. Make sure all other CPUs agree with that, to avoid them
1529 * modifying the page we're about to migrate.
1531 * Must be done under PTL such that we'll observe the relevant
1532 * inc_tlb_flush_pending().
1534 * We are not sure a pending tlb flush here is for a huge page
1535 * mapping or not. Hence use the tlb range variant
1537 if (mm_tlb_flush_pending(vma->vm_mm))
1538 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1541 * Migrate the THP to the requested node, returns with page unlocked
1542 * and access rights restored.
1544 spin_unlock(vmf->ptl);
1546 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1547 vmf->pmd, pmd, vmf->address, page, target_nid);
1549 flags |= TNF_MIGRATED;
1550 page_nid = target_nid;
1552 flags |= TNF_MIGRATE_FAIL;
1556 BUG_ON(!PageLocked(page));
1557 was_writable = pmd_savedwrite(pmd);
1558 pmd = pmd_modify(pmd, vma->vm_page_prot);
1559 pmd = pmd_mkyoung(pmd);
1561 pmd = pmd_mkwrite(pmd);
1562 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1563 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1566 spin_unlock(vmf->ptl);
1570 page_unlock_anon_vma_read(anon_vma);
1573 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1580 * Return true if we do MADV_FREE successfully on entire pmd page.
1581 * Otherwise, return false.
1583 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1584 pmd_t *pmd, unsigned long addr, unsigned long next)
1589 struct mm_struct *mm = tlb->mm;
1592 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1594 ptl = pmd_trans_huge_lock(pmd, vma);
1599 if (is_huge_zero_pmd(orig_pmd))
1602 page = pmd_page(orig_pmd);
1604 * If other processes are mapping this page, we couldn't discard
1605 * the page unless they all do MADV_FREE so let's skip the page.
1607 if (page_mapcount(page) != 1)
1610 if (!trylock_page(page))
1614 * If user want to discard part-pages of THP, split it so MADV_FREE
1615 * will deactivate only them.
1617 if (next - addr != HPAGE_PMD_SIZE) {
1620 split_huge_page(page);
1626 if (PageDirty(page))
1627 ClearPageDirty(page);
1630 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1631 pmdp_invalidate(vma, addr, pmd);
1632 orig_pmd = pmd_mkold(orig_pmd);
1633 orig_pmd = pmd_mkclean(orig_pmd);
1635 set_pmd_at(mm, addr, pmd, orig_pmd);
1636 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1639 mark_page_lazyfree(page);
1647 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1651 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1652 pte_free(mm, pgtable);
1653 atomic_long_dec(&mm->nr_ptes);
1656 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1657 pmd_t *pmd, unsigned long addr)
1662 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1664 ptl = __pmd_trans_huge_lock(pmd, vma);
1668 * For architectures like ppc64 we look at deposited pgtable
1669 * when calling pmdp_huge_get_and_clear. So do the
1670 * pgtable_trans_huge_withdraw after finishing pmdp related
1673 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1675 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1676 if (vma_is_dax(vma)) {
1677 if (arch_needs_pgtable_deposit())
1678 zap_deposited_table(tlb->mm, pmd);
1680 if (is_huge_zero_pmd(orig_pmd))
1681 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1682 } else if (is_huge_zero_pmd(orig_pmd)) {
1683 zap_deposited_table(tlb->mm, pmd);
1685 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1687 struct page *page = pmd_page(orig_pmd);
1688 page_remove_rmap(page, true);
1689 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1690 VM_BUG_ON_PAGE(!PageHead(page), page);
1691 if (PageAnon(page)) {
1692 zap_deposited_table(tlb->mm, pmd);
1693 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1695 if (arch_needs_pgtable_deposit())
1696 zap_deposited_table(tlb->mm, pmd);
1697 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1700 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1705 #ifndef pmd_move_must_withdraw
1706 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1707 spinlock_t *old_pmd_ptl,
1708 struct vm_area_struct *vma)
1711 * With split pmd lock we also need to move preallocated
1712 * PTE page table if new_pmd is on different PMD page table.
1714 * We also don't deposit and withdraw tables for file pages.
1716 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1720 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1721 unsigned long new_addr, unsigned long old_end,
1722 pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1724 spinlock_t *old_ptl, *new_ptl;
1726 struct mm_struct *mm = vma->vm_mm;
1727 bool force_flush = false;
1729 if ((old_addr & ~HPAGE_PMD_MASK) ||
1730 (new_addr & ~HPAGE_PMD_MASK) ||
1731 old_end - old_addr < HPAGE_PMD_SIZE)
1735 * The destination pmd shouldn't be established, free_pgtables()
1736 * should have release it.
1738 if (WARN_ON(!pmd_none(*new_pmd))) {
1739 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1744 * We don't have to worry about the ordering of src and dst
1745 * ptlocks because exclusive mmap_sem prevents deadlock.
1747 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1749 new_ptl = pmd_lockptr(mm, new_pmd);
1750 if (new_ptl != old_ptl)
1751 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1752 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1753 if (pmd_present(pmd) && pmd_dirty(pmd))
1755 VM_BUG_ON(!pmd_none(*new_pmd));
1757 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1759 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1760 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1762 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1763 if (new_ptl != old_ptl)
1764 spin_unlock(new_ptl);
1766 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1769 spin_unlock(old_ptl);
1777 * - 0 if PMD could not be locked
1778 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1779 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1781 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1782 unsigned long addr, pgprot_t newprot, int prot_numa)
1784 struct mm_struct *mm = vma->vm_mm;
1787 bool preserve_write;
1790 ptl = __pmd_trans_huge_lock(pmd, vma);
1794 preserve_write = prot_numa && pmd_write(*pmd);
1798 * Avoid trapping faults against the zero page. The read-only
1799 * data is likely to be read-cached on the local CPU and
1800 * local/remote hits to the zero page are not interesting.
1802 if (prot_numa && is_huge_zero_pmd(*pmd))
1805 if (prot_numa && pmd_protnone(*pmd))
1809 * In case prot_numa, we are under down_read(mmap_sem). It's critical
1810 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1811 * which is also under down_read(mmap_sem):
1814 * change_huge_pmd(prot_numa=1)
1815 * pmdp_huge_get_and_clear_notify()
1816 * madvise_dontneed()
1818 * pmd_trans_huge(*pmd) == 0 (without ptl)
1821 * // pmd is re-established
1823 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1824 * which may break userspace.
1826 * pmdp_invalidate() is required to make sure we don't miss
1827 * dirty/young flags set by hardware.
1830 pmdp_invalidate(vma, addr, pmd);
1833 * Recover dirty/young flags. It relies on pmdp_invalidate to not
1836 if (pmd_dirty(*pmd))
1837 entry = pmd_mkdirty(entry);
1838 if (pmd_young(*pmd))
1839 entry = pmd_mkyoung(entry);
1841 entry = pmd_modify(entry, newprot);
1843 entry = pmd_mk_savedwrite(entry);
1845 set_pmd_at(mm, addr, pmd, entry);
1846 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1853 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1855 * Note that if it returns page table lock pointer, this routine returns without
1856 * unlocking page table lock. So callers must unlock it.
1858 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1861 ptl = pmd_lock(vma->vm_mm, pmd);
1862 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1869 * Returns true if a given pud maps a thp, false otherwise.
1871 * Note that if it returns true, this routine returns without unlocking page
1872 * table lock. So callers must unlock it.
1874 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1878 ptl = pud_lock(vma->vm_mm, pud);
1879 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1885 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1886 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1887 pud_t *pud, unsigned long addr)
1892 ptl = __pud_trans_huge_lock(pud, vma);
1896 * For architectures like ppc64 we look at deposited pgtable
1897 * when calling pudp_huge_get_and_clear. So do the
1898 * pgtable_trans_huge_withdraw after finishing pudp related
1901 orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1903 tlb_remove_pud_tlb_entry(tlb, pud, addr);
1904 if (vma_is_dax(vma)) {
1906 /* No zero page support yet */
1908 /* No support for anonymous PUD pages yet */
1914 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1915 unsigned long haddr)
1917 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1918 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1919 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1920 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1922 count_vm_event(THP_SPLIT_PUD);
1924 pudp_huge_clear_flush_notify(vma, haddr, pud);
1927 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
1928 unsigned long address)
1931 struct mm_struct *mm = vma->vm_mm;
1932 unsigned long haddr = address & HPAGE_PUD_MASK;
1934 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
1935 ptl = pud_lock(mm, pud);
1936 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
1938 __split_huge_pud_locked(vma, pud, haddr);
1942 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PUD_SIZE);
1944 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1946 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1947 unsigned long haddr, pmd_t *pmd)
1949 struct mm_struct *mm = vma->vm_mm;
1954 /* leave pmd empty until pte is filled */
1955 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1957 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1958 pmd_populate(mm, &_pmd, pgtable);
1960 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1962 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1963 entry = pte_mkspecial(entry);
1964 pte = pte_offset_map(&_pmd, haddr);
1965 VM_BUG_ON(!pte_none(*pte));
1966 set_pte_at(mm, haddr, pte, entry);
1969 smp_wmb(); /* make pte visible before pmd */
1970 pmd_populate(mm, pmd, pgtable);
1973 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
1974 unsigned long haddr, bool freeze)
1976 struct mm_struct *mm = vma->vm_mm;
1980 bool young, write, dirty, soft_dirty;
1984 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
1985 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1986 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
1987 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
1989 count_vm_event(THP_SPLIT_PMD);
1991 if (!vma_is_anonymous(vma)) {
1992 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1994 * We are going to unmap this huge page. So
1995 * just go ahead and zap it
1997 if (arch_needs_pgtable_deposit())
1998 zap_deposited_table(mm, pmd);
1999 if (vma_is_dax(vma))
2001 page = pmd_page(_pmd);
2002 if (!PageReferenced(page) && pmd_young(_pmd))
2003 SetPageReferenced(page);
2004 page_remove_rmap(page, true);
2006 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
2008 } else if (is_huge_zero_pmd(*pmd)) {
2009 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2012 page = pmd_page(*pmd);
2013 VM_BUG_ON_PAGE(!page_count(page), page);
2014 page_ref_add(page, HPAGE_PMD_NR - 1);
2015 write = pmd_write(*pmd);
2016 young = pmd_young(*pmd);
2017 dirty = pmd_dirty(*pmd);
2018 soft_dirty = pmd_soft_dirty(*pmd);
2020 pmdp_huge_split_prepare(vma, haddr, pmd);
2021 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2022 pmd_populate(mm, &_pmd, pgtable);
2024 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2027 * Note that NUMA hinting access restrictions are not
2028 * transferred to avoid any possibility of altering
2029 * permissions across VMAs.
2032 swp_entry_t swp_entry;
2033 swp_entry = make_migration_entry(page + i, write);
2034 entry = swp_entry_to_pte(swp_entry);
2036 entry = pte_swp_mksoft_dirty(entry);
2038 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2039 entry = maybe_mkwrite(entry, vma);
2041 entry = pte_wrprotect(entry);
2043 entry = pte_mkold(entry);
2045 entry = pte_mksoft_dirty(entry);
2048 SetPageDirty(page + i);
2049 pte = pte_offset_map(&_pmd, addr);
2050 BUG_ON(!pte_none(*pte));
2051 set_pte_at(mm, addr, pte, entry);
2052 atomic_inc(&page[i]._mapcount);
2057 * Set PG_double_map before dropping compound_mapcount to avoid
2058 * false-negative page_mapped().
2060 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2061 for (i = 0; i < HPAGE_PMD_NR; i++)
2062 atomic_inc(&page[i]._mapcount);
2065 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2066 /* Last compound_mapcount is gone. */
2067 __dec_node_page_state(page, NR_ANON_THPS);
2068 if (TestClearPageDoubleMap(page)) {
2069 /* No need in mapcount reference anymore */
2070 for (i = 0; i < HPAGE_PMD_NR; i++)
2071 atomic_dec(&page[i]._mapcount);
2075 smp_wmb(); /* make pte visible before pmd */
2077 * Up to this point the pmd is present and huge and userland has the
2078 * whole access to the hugepage during the split (which happens in
2079 * place). If we overwrite the pmd with the not-huge version pointing
2080 * to the pte here (which of course we could if all CPUs were bug
2081 * free), userland could trigger a small page size TLB miss on the
2082 * small sized TLB while the hugepage TLB entry is still established in
2083 * the huge TLB. Some CPU doesn't like that.
2084 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2085 * 383 on page 93. Intel should be safe but is also warns that it's
2086 * only safe if the permission and cache attributes of the two entries
2087 * loaded in the two TLB is identical (which should be the case here).
2088 * But it is generally safer to never allow small and huge TLB entries
2089 * for the same virtual address to be loaded simultaneously. So instead
2090 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2091 * current pmd notpresent (atomically because here the pmd_trans_huge
2092 * and pmd_trans_splitting must remain set at all times on the pmd
2093 * until the split is complete for this pmd), then we flush the SMP TLB
2094 * and finally we write the non-huge version of the pmd entry with
2097 pmdp_invalidate(vma, haddr, pmd);
2098 pmd_populate(mm, pmd, pgtable);
2101 for (i = 0; i < HPAGE_PMD_NR; i++) {
2102 page_remove_rmap(page + i, false);
2108 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2109 unsigned long address, bool freeze, struct page *page)
2112 struct mm_struct *mm = vma->vm_mm;
2113 unsigned long haddr = address & HPAGE_PMD_MASK;
2115 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2116 ptl = pmd_lock(mm, pmd);
2119 * If caller asks to setup a migration entries, we need a page to check
2120 * pmd against. Otherwise we can end up replacing wrong page.
2122 VM_BUG_ON(freeze && !page);
2123 if (page && page != pmd_page(*pmd))
2126 if (pmd_trans_huge(*pmd)) {
2127 page = pmd_page(*pmd);
2128 if (PageMlocked(page))
2129 clear_page_mlock(page);
2130 } else if (!pmd_devmap(*pmd))
2132 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2135 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
2138 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2139 bool freeze, struct page *page)
2146 pgd = pgd_offset(vma->vm_mm, address);
2147 if (!pgd_present(*pgd))
2150 p4d = p4d_offset(pgd, address);
2151 if (!p4d_present(*p4d))
2154 pud = pud_offset(p4d, address);
2155 if (!pud_present(*pud))
2158 pmd = pmd_offset(pud, address);
2160 __split_huge_pmd(vma, pmd, address, freeze, page);
2163 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2164 unsigned long start,
2169 * If the new start address isn't hpage aligned and it could
2170 * previously contain an hugepage: check if we need to split
2173 if (start & ~HPAGE_PMD_MASK &&
2174 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2175 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2176 split_huge_pmd_address(vma, start, false, NULL);
2179 * If the new end address isn't hpage aligned and it could
2180 * previously contain an hugepage: check if we need to split
2183 if (end & ~HPAGE_PMD_MASK &&
2184 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2185 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2186 split_huge_pmd_address(vma, end, false, NULL);
2189 * If we're also updating the vma->vm_next->vm_start, if the new
2190 * vm_next->vm_start isn't page aligned and it could previously
2191 * contain an hugepage: check if we need to split an huge pmd.
2193 if (adjust_next > 0) {
2194 struct vm_area_struct *next = vma->vm_next;
2195 unsigned long nstart = next->vm_start;
2196 nstart += adjust_next << PAGE_SHIFT;
2197 if (nstart & ~HPAGE_PMD_MASK &&
2198 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2199 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2200 split_huge_pmd_address(next, nstart, false, NULL);
2204 static void freeze_page(struct page *page)
2206 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2207 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2210 VM_BUG_ON_PAGE(!PageHead(page), page);
2213 ttu_flags |= TTU_MIGRATION;
2215 unmap_success = try_to_unmap(page, ttu_flags);
2216 VM_BUG_ON_PAGE(!unmap_success, page);
2219 static void unfreeze_page(struct page *page)
2222 if (PageTransHuge(page)) {
2223 remove_migration_ptes(page, page, true);
2225 for (i = 0; i < HPAGE_PMD_NR; i++)
2226 remove_migration_ptes(page + i, page + i, true);
2230 static void __split_huge_page_tail(struct page *head, int tail,
2231 struct lruvec *lruvec, struct list_head *list)
2233 struct page *page_tail = head + tail;
2235 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2236 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
2239 * tail_page->_refcount is zero and not changing from under us. But
2240 * get_page_unless_zero() may be running from under us on the
2241 * tail_page. If we used atomic_set() below instead of atomic_inc() or
2242 * atomic_add(), we would then run atomic_set() concurrently with
2243 * get_page_unless_zero(), and atomic_set() is implemented in C not
2244 * using locked ops. spin_unlock on x86 sometime uses locked ops
2245 * because of PPro errata 66, 92, so unless somebody can guarantee
2246 * atomic_set() here would be safe on all archs (and not only on x86),
2247 * it's safer to use atomic_inc()/atomic_add().
2249 if (PageAnon(head) && !PageSwapCache(head)) {
2250 page_ref_inc(page_tail);
2252 /* Additional pin to radix tree */
2253 page_ref_add(page_tail, 2);
2256 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2257 page_tail->flags |= (head->flags &
2258 ((1L << PG_referenced) |
2259 (1L << PG_swapbacked) |
2260 (1L << PG_swapcache) |
2261 (1L << PG_mlocked) |
2262 (1L << PG_uptodate) |
2265 (1L << PG_unevictable) |
2269 * After clearing PageTail the gup refcount can be released.
2270 * Page flags also must be visible before we make the page non-compound.
2274 clear_compound_head(page_tail);
2276 if (page_is_young(head))
2277 set_page_young(page_tail);
2278 if (page_is_idle(head))
2279 set_page_idle(page_tail);
2281 /* ->mapping in first tail page is compound_mapcount */
2282 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2284 page_tail->mapping = head->mapping;
2286 page_tail->index = head->index + tail;
2287 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2288 lru_add_page_tail(head, page_tail, lruvec, list);
2291 static void __split_huge_page(struct page *page, struct list_head *list,
2292 unsigned long flags)
2294 struct page *head = compound_head(page);
2295 struct zone *zone = page_zone(head);
2296 struct lruvec *lruvec;
2300 lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2302 /* complete memcg works before add pages to LRU */
2303 mem_cgroup_split_huge_fixup(head);
2305 if (!PageAnon(page))
2306 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2308 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2309 __split_huge_page_tail(head, i, lruvec, list);
2310 /* Some pages can be beyond i_size: drop them from page cache */
2311 if (head[i].index >= end) {
2312 __ClearPageDirty(head + i);
2313 __delete_from_page_cache(head + i, NULL);
2314 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2315 shmem_uncharge(head->mapping->host, 1);
2320 ClearPageCompound(head);
2321 /* See comment in __split_huge_page_tail() */
2322 if (PageAnon(head)) {
2323 /* Additional pin to radix tree of swap cache */
2324 if (PageSwapCache(head))
2325 page_ref_add(head, 2);
2329 /* Additional pin to radix tree */
2330 page_ref_add(head, 2);
2331 spin_unlock(&head->mapping->tree_lock);
2334 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2336 unfreeze_page(head);
2338 for (i = 0; i < HPAGE_PMD_NR; i++) {
2339 struct page *subpage = head + i;
2340 if (subpage == page)
2342 unlock_page(subpage);
2345 * Subpages may be freed if there wasn't any mapping
2346 * like if add_to_swap() is running on a lru page that
2347 * had its mapping zapped. And freeing these pages
2348 * requires taking the lru_lock so we do the put_page
2349 * of the tail pages after the split is complete.
2355 int total_mapcount(struct page *page)
2357 int i, compound, ret;
2359 VM_BUG_ON_PAGE(PageTail(page), page);
2361 if (likely(!PageCompound(page)))
2362 return atomic_read(&page->_mapcount) + 1;
2364 compound = compound_mapcount(page);
2368 for (i = 0; i < HPAGE_PMD_NR; i++)
2369 ret += atomic_read(&page[i]._mapcount) + 1;
2370 /* File pages has compound_mapcount included in _mapcount */
2371 if (!PageAnon(page))
2372 return ret - compound * HPAGE_PMD_NR;
2373 if (PageDoubleMap(page))
2374 ret -= HPAGE_PMD_NR;
2379 * This calculates accurately how many mappings a transparent hugepage
2380 * has (unlike page_mapcount() which isn't fully accurate). This full
2381 * accuracy is primarily needed to know if copy-on-write faults can
2382 * reuse the page and change the mapping to read-write instead of
2383 * copying them. At the same time this returns the total_mapcount too.
2385 * The function returns the highest mapcount any one of the subpages
2386 * has. If the return value is one, even if different processes are
2387 * mapping different subpages of the transparent hugepage, they can
2388 * all reuse it, because each process is reusing a different subpage.
2390 * The total_mapcount is instead counting all virtual mappings of the
2391 * subpages. If the total_mapcount is equal to "one", it tells the
2392 * caller all mappings belong to the same "mm" and in turn the
2393 * anon_vma of the transparent hugepage can become the vma->anon_vma
2394 * local one as no other process may be mapping any of the subpages.
2396 * It would be more accurate to replace page_mapcount() with
2397 * page_trans_huge_mapcount(), however we only use
2398 * page_trans_huge_mapcount() in the copy-on-write faults where we
2399 * need full accuracy to avoid breaking page pinning, because
2400 * page_trans_huge_mapcount() is slower than page_mapcount().
2402 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2404 int i, ret, _total_mapcount, mapcount;
2406 /* hugetlbfs shouldn't call it */
2407 VM_BUG_ON_PAGE(PageHuge(page), page);
2409 if (likely(!PageTransCompound(page))) {
2410 mapcount = atomic_read(&page->_mapcount) + 1;
2412 *total_mapcount = mapcount;
2416 page = compound_head(page);
2418 _total_mapcount = ret = 0;
2419 for (i = 0; i < HPAGE_PMD_NR; i++) {
2420 mapcount = atomic_read(&page[i]._mapcount) + 1;
2421 ret = max(ret, mapcount);
2422 _total_mapcount += mapcount;
2424 if (PageDoubleMap(page)) {
2426 _total_mapcount -= HPAGE_PMD_NR;
2428 mapcount = compound_mapcount(page);
2430 _total_mapcount += mapcount;
2432 *total_mapcount = _total_mapcount;
2436 /* Racy check whether the huge page can be split */
2437 bool can_split_huge_page(struct page *page, int *pextra_pins)
2441 /* Additional pins from radix tree */
2443 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2445 extra_pins = HPAGE_PMD_NR;
2447 *pextra_pins = extra_pins;
2448 return total_mapcount(page) == page_count(page) - extra_pins - 1;
2452 * This function splits huge page into normal pages. @page can point to any
2453 * subpage of huge page to split. Split doesn't change the position of @page.
2455 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2456 * The huge page must be locked.
2458 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2460 * Both head page and tail pages will inherit mapping, flags, and so on from
2463 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2464 * they are not mapped.
2466 * Returns 0 if the hugepage is split successfully.
2467 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2470 int split_huge_page_to_list(struct page *page, struct list_head *list)
2472 struct page *head = compound_head(page);
2473 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2474 struct anon_vma *anon_vma = NULL;
2475 struct address_space *mapping = NULL;
2476 int count, mapcount, extra_pins, ret;
2478 unsigned long flags;
2480 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2481 VM_BUG_ON_PAGE(!PageLocked(page), page);
2482 VM_BUG_ON_PAGE(!PageCompound(page), page);
2484 if (PageWriteback(page))
2487 if (PageAnon(head)) {
2489 * The caller does not necessarily hold an mmap_sem that would
2490 * prevent the anon_vma disappearing so we first we take a
2491 * reference to it and then lock the anon_vma for write. This
2492 * is similar to page_lock_anon_vma_read except the write lock
2493 * is taken to serialise against parallel split or collapse
2496 anon_vma = page_get_anon_vma(head);
2502 anon_vma_lock_write(anon_vma);
2504 mapping = head->mapping;
2513 i_mmap_lock_read(mapping);
2517 * Racy check if we can split the page, before freeze_page() will
2520 if (!can_split_huge_page(head, &extra_pins)) {
2525 mlocked = PageMlocked(page);
2527 VM_BUG_ON_PAGE(compound_mapcount(head), head);
2529 /* Make sure the page is not on per-CPU pagevec as it takes pin */
2533 /* prevent PageLRU to go away from under us, and freeze lru stats */
2534 spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2539 spin_lock(&mapping->tree_lock);
2540 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2543 * Check if the head page is present in radix tree.
2544 * We assume all tail are present too, if head is there.
2546 if (radix_tree_deref_slot_protected(pslot,
2547 &mapping->tree_lock) != head)
2551 /* Prevent deferred_split_scan() touching ->_refcount */
2552 spin_lock(&pgdata->split_queue_lock);
2553 count = page_count(head);
2554 mapcount = total_mapcount(head);
2555 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2556 if (!list_empty(page_deferred_list(head))) {
2557 pgdata->split_queue_len--;
2558 list_del(page_deferred_list(head));
2561 __dec_node_page_state(page, NR_SHMEM_THPS);
2562 spin_unlock(&pgdata->split_queue_lock);
2563 __split_huge_page(page, list, flags);
2564 if (PageSwapCache(head)) {
2565 swp_entry_t entry = { .val = page_private(head) };
2567 ret = split_swap_cluster(entry);
2571 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2572 pr_alert("total_mapcount: %u, page_count(): %u\n",
2575 dump_page(head, NULL);
2576 dump_page(page, "total_mapcount(head) > 0");
2579 spin_unlock(&pgdata->split_queue_lock);
2581 spin_unlock(&mapping->tree_lock);
2582 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2583 unfreeze_page(head);
2589 anon_vma_unlock_write(anon_vma);
2590 put_anon_vma(anon_vma);
2593 i_mmap_unlock_read(mapping);
2595 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2599 void free_transhuge_page(struct page *page)
2601 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2602 unsigned long flags;
2604 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2605 if (!list_empty(page_deferred_list(page))) {
2606 pgdata->split_queue_len--;
2607 list_del(page_deferred_list(page));
2609 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2610 free_compound_page(page);
2613 void deferred_split_huge_page(struct page *page)
2615 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2616 unsigned long flags;
2618 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2620 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2621 if (list_empty(page_deferred_list(page))) {
2622 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2623 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2624 pgdata->split_queue_len++;
2626 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2629 static unsigned long deferred_split_count(struct shrinker *shrink,
2630 struct shrink_control *sc)
2632 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2633 return ACCESS_ONCE(pgdata->split_queue_len);
2636 static unsigned long deferred_split_scan(struct shrinker *shrink,
2637 struct shrink_control *sc)
2639 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2640 unsigned long flags;
2641 LIST_HEAD(list), *pos, *next;
2645 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2646 /* Take pin on all head pages to avoid freeing them under us */
2647 list_for_each_safe(pos, next, &pgdata->split_queue) {
2648 page = list_entry((void *)pos, struct page, mapping);
2649 page = compound_head(page);
2650 if (get_page_unless_zero(page)) {
2651 list_move(page_deferred_list(page), &list);
2653 /* We lost race with put_compound_page() */
2654 list_del_init(page_deferred_list(page));
2655 pgdata->split_queue_len--;
2657 if (!--sc->nr_to_scan)
2660 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2662 list_for_each_safe(pos, next, &list) {
2663 page = list_entry((void *)pos, struct page, mapping);
2665 /* split_huge_page() removes page from list on success */
2666 if (!split_huge_page(page))
2672 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2673 list_splice_tail(&list, &pgdata->split_queue);
2674 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2677 * Stop shrinker if we didn't split any page, but the queue is empty.
2678 * This can happen if pages were freed under us.
2680 if (!split && list_empty(&pgdata->split_queue))
2685 static struct shrinker deferred_split_shrinker = {
2686 .count_objects = deferred_split_count,
2687 .scan_objects = deferred_split_scan,
2688 .seeks = DEFAULT_SEEKS,
2689 .flags = SHRINKER_NUMA_AWARE,
2692 #ifdef CONFIG_DEBUG_FS
2693 static int split_huge_pages_set(void *data, u64 val)
2697 unsigned long pfn, max_zone_pfn;
2698 unsigned long total = 0, split = 0;
2703 for_each_populated_zone(zone) {
2704 max_zone_pfn = zone_end_pfn(zone);
2705 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2706 if (!pfn_valid(pfn))
2709 page = pfn_to_page(pfn);
2710 if (!get_page_unless_zero(page))
2713 if (zone != page_zone(page))
2716 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2721 if (!split_huge_page(page))
2729 pr_info("%lu of %lu THP split\n", split, total);
2733 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2736 static int __init split_huge_pages_debugfs(void)
2740 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2741 &split_huge_pages_fops);
2743 pr_warn("Failed to create split_huge_pages in debugfs");
2746 late_initcall(split_huge_pages_debugfs);