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/kthread.h>
22 #include <linux/khugepaged.h>
23 #include <linux/freezer.h>
24 #include <linux/mman.h>
25 #include <linux/pagemap.h>
26 #include <linux/migrate.h>
27 #include <linux/hashtable.h>
28 #include <linux/userfaultfd_k.h>
29 #include <linux/page_idle.h>
32 #include <asm/pgalloc.h>
42 SCAN_NO_REFERENCED_PAGE,
56 SCAN_ALLOC_HUGE_PAGE_FAIL,
57 SCAN_CGROUP_CHARGE_FAIL
60 #define CREATE_TRACE_POINTS
61 #include <trace/events/huge_memory.h>
64 * By default transparent hugepage support is disabled in order that avoid
65 * to risk increase the memory footprint of applications without a guaranteed
66 * benefit. When transparent hugepage support is enabled, is for all mappings,
67 * and khugepaged scans all mappings.
68 * Defrag is invoked by khugepaged hugepage allocations and by page faults
69 * for all hugepage allocations.
71 unsigned long transparent_hugepage_flags __read_mostly =
72 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
73 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
75 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
76 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
78 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
79 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
80 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
82 /* default scan 8*512 pte (or vmas) every 30 second */
83 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
84 static unsigned int khugepaged_pages_collapsed;
85 static unsigned int khugepaged_full_scans;
86 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
87 /* during fragmentation poll the hugepage allocator once every minute */
88 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
89 static struct task_struct *khugepaged_thread __read_mostly;
90 static DEFINE_MUTEX(khugepaged_mutex);
91 static DEFINE_SPINLOCK(khugepaged_mm_lock);
92 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
94 * default collapse hugepages if there is at least one pte mapped like
95 * it would have happened if the vma was large enough during page
98 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
100 static int khugepaged(void *none);
101 static int khugepaged_slab_init(void);
102 static void khugepaged_slab_exit(void);
104 #define MM_SLOTS_HASH_BITS 10
105 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
107 static struct kmem_cache *mm_slot_cache __read_mostly;
110 * struct mm_slot - hash lookup from mm to mm_slot
111 * @hash: hash collision list
112 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
113 * @mm: the mm that this information is valid for
116 struct hlist_node hash;
117 struct list_head mm_node;
118 struct mm_struct *mm;
122 * struct khugepaged_scan - cursor for scanning
123 * @mm_head: the head of the mm list to scan
124 * @mm_slot: the current mm_slot we are scanning
125 * @address: the next address inside that to be scanned
127 * There is only the one khugepaged_scan instance of this cursor structure.
129 struct khugepaged_scan {
130 struct list_head mm_head;
131 struct mm_slot *mm_slot;
132 unsigned long address;
134 static struct khugepaged_scan khugepaged_scan = {
135 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
138 static DEFINE_SPINLOCK(split_queue_lock);
139 static LIST_HEAD(split_queue);
140 static unsigned long split_queue_len;
141 static struct shrinker deferred_split_shrinker;
143 static void set_recommended_min_free_kbytes(void)
147 unsigned long recommended_min;
149 for_each_populated_zone(zone)
152 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
153 recommended_min = pageblock_nr_pages * nr_zones * 2;
156 * Make sure that on average at least two pageblocks are almost free
157 * of another type, one for a migratetype to fall back to and a
158 * second to avoid subsequent fallbacks of other types There are 3
159 * MIGRATE_TYPES we care about.
161 recommended_min += pageblock_nr_pages * nr_zones *
162 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
164 /* don't ever allow to reserve more than 5% of the lowmem */
165 recommended_min = min(recommended_min,
166 (unsigned long) nr_free_buffer_pages() / 20);
167 recommended_min <<= (PAGE_SHIFT-10);
169 if (recommended_min > min_free_kbytes) {
170 if (user_min_free_kbytes >= 0)
171 pr_info("raising min_free_kbytes from %d to %lu "
172 "to help transparent hugepage allocations\n",
173 min_free_kbytes, recommended_min);
175 min_free_kbytes = recommended_min;
177 setup_per_zone_wmarks();
180 static int start_stop_khugepaged(void)
183 if (khugepaged_enabled()) {
184 if (!khugepaged_thread)
185 khugepaged_thread = kthread_run(khugepaged, NULL,
187 if (IS_ERR(khugepaged_thread)) {
188 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
189 err = PTR_ERR(khugepaged_thread);
190 khugepaged_thread = NULL;
194 if (!list_empty(&khugepaged_scan.mm_head))
195 wake_up_interruptible(&khugepaged_wait);
197 set_recommended_min_free_kbytes();
198 } else if (khugepaged_thread) {
199 kthread_stop(khugepaged_thread);
200 khugepaged_thread = NULL;
206 static atomic_t huge_zero_refcount;
207 struct page *huge_zero_page __read_mostly;
209 struct page *get_huge_zero_page(void)
211 struct page *zero_page;
213 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
214 return READ_ONCE(huge_zero_page);
216 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
219 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
222 count_vm_event(THP_ZERO_PAGE_ALLOC);
224 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
226 __free_pages(zero_page, compound_order(zero_page));
230 /* We take additional reference here. It will be put back by shrinker */
231 atomic_set(&huge_zero_refcount, 2);
233 return READ_ONCE(huge_zero_page);
236 static void put_huge_zero_page(void)
239 * Counter should never go to zero here. Only shrinker can put
242 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
245 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
246 struct shrink_control *sc)
248 /* we can free zero page only if last reference remains */
249 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
252 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
253 struct shrink_control *sc)
255 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
256 struct page *zero_page = xchg(&huge_zero_page, NULL);
257 BUG_ON(zero_page == NULL);
258 __free_pages(zero_page, compound_order(zero_page));
265 static struct shrinker huge_zero_page_shrinker = {
266 .count_objects = shrink_huge_zero_page_count,
267 .scan_objects = shrink_huge_zero_page_scan,
268 .seeks = DEFAULT_SEEKS,
273 static ssize_t double_flag_show(struct kobject *kobj,
274 struct kobj_attribute *attr, char *buf,
275 enum transparent_hugepage_flag enabled,
276 enum transparent_hugepage_flag req_madv)
278 if (test_bit(enabled, &transparent_hugepage_flags)) {
279 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
280 return sprintf(buf, "[always] madvise never\n");
281 } else if (test_bit(req_madv, &transparent_hugepage_flags))
282 return sprintf(buf, "always [madvise] never\n");
284 return sprintf(buf, "always madvise [never]\n");
286 static ssize_t double_flag_store(struct kobject *kobj,
287 struct kobj_attribute *attr,
288 const char *buf, size_t count,
289 enum transparent_hugepage_flag enabled,
290 enum transparent_hugepage_flag req_madv)
292 if (!memcmp("always", buf,
293 min(sizeof("always")-1, count))) {
294 set_bit(enabled, &transparent_hugepage_flags);
295 clear_bit(req_madv, &transparent_hugepage_flags);
296 } else if (!memcmp("madvise", buf,
297 min(sizeof("madvise")-1, count))) {
298 clear_bit(enabled, &transparent_hugepage_flags);
299 set_bit(req_madv, &transparent_hugepage_flags);
300 } else if (!memcmp("never", buf,
301 min(sizeof("never")-1, count))) {
302 clear_bit(enabled, &transparent_hugepage_flags);
303 clear_bit(req_madv, &transparent_hugepage_flags);
310 static ssize_t enabled_show(struct kobject *kobj,
311 struct kobj_attribute *attr, char *buf)
313 return double_flag_show(kobj, attr, buf,
314 TRANSPARENT_HUGEPAGE_FLAG,
315 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
317 static ssize_t enabled_store(struct kobject *kobj,
318 struct kobj_attribute *attr,
319 const char *buf, size_t count)
323 ret = double_flag_store(kobj, attr, buf, count,
324 TRANSPARENT_HUGEPAGE_FLAG,
325 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
330 mutex_lock(&khugepaged_mutex);
331 err = start_stop_khugepaged();
332 mutex_unlock(&khugepaged_mutex);
340 static struct kobj_attribute enabled_attr =
341 __ATTR(enabled, 0644, enabled_show, enabled_store);
343 static ssize_t single_flag_show(struct kobject *kobj,
344 struct kobj_attribute *attr, char *buf,
345 enum transparent_hugepage_flag flag)
347 return sprintf(buf, "%d\n",
348 !!test_bit(flag, &transparent_hugepage_flags));
351 static ssize_t single_flag_store(struct kobject *kobj,
352 struct kobj_attribute *attr,
353 const char *buf, size_t count,
354 enum transparent_hugepage_flag flag)
359 ret = kstrtoul(buf, 10, &value);
366 set_bit(flag, &transparent_hugepage_flags);
368 clear_bit(flag, &transparent_hugepage_flags);
374 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
375 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
376 * memory just to allocate one more hugepage.
378 static ssize_t defrag_show(struct kobject *kobj,
379 struct kobj_attribute *attr, char *buf)
381 return double_flag_show(kobj, attr, buf,
382 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
383 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
385 static ssize_t defrag_store(struct kobject *kobj,
386 struct kobj_attribute *attr,
387 const char *buf, size_t count)
389 return double_flag_store(kobj, attr, buf, count,
390 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
391 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
393 static struct kobj_attribute defrag_attr =
394 __ATTR(defrag, 0644, defrag_show, defrag_store);
396 static ssize_t use_zero_page_show(struct kobject *kobj,
397 struct kobj_attribute *attr, char *buf)
399 return single_flag_show(kobj, attr, buf,
400 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
402 static ssize_t use_zero_page_store(struct kobject *kobj,
403 struct kobj_attribute *attr, const char *buf, size_t count)
405 return single_flag_store(kobj, attr, buf, count,
406 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
408 static struct kobj_attribute use_zero_page_attr =
409 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
410 #ifdef CONFIG_DEBUG_VM
411 static ssize_t debug_cow_show(struct kobject *kobj,
412 struct kobj_attribute *attr, char *buf)
414 return single_flag_show(kobj, attr, buf,
415 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
417 static ssize_t debug_cow_store(struct kobject *kobj,
418 struct kobj_attribute *attr,
419 const char *buf, size_t count)
421 return single_flag_store(kobj, attr, buf, count,
422 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
424 static struct kobj_attribute debug_cow_attr =
425 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
426 #endif /* CONFIG_DEBUG_VM */
428 static struct attribute *hugepage_attr[] = {
431 &use_zero_page_attr.attr,
432 #ifdef CONFIG_DEBUG_VM
433 &debug_cow_attr.attr,
438 static struct attribute_group hugepage_attr_group = {
439 .attrs = hugepage_attr,
442 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
443 struct kobj_attribute *attr,
446 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
449 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
450 struct kobj_attribute *attr,
451 const char *buf, size_t count)
456 err = kstrtoul(buf, 10, &msecs);
457 if (err || msecs > UINT_MAX)
460 khugepaged_scan_sleep_millisecs = msecs;
461 wake_up_interruptible(&khugepaged_wait);
465 static struct kobj_attribute scan_sleep_millisecs_attr =
466 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
467 scan_sleep_millisecs_store);
469 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
470 struct kobj_attribute *attr,
473 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
476 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
477 struct kobj_attribute *attr,
478 const char *buf, size_t count)
483 err = kstrtoul(buf, 10, &msecs);
484 if (err || msecs > UINT_MAX)
487 khugepaged_alloc_sleep_millisecs = msecs;
488 wake_up_interruptible(&khugepaged_wait);
492 static struct kobj_attribute alloc_sleep_millisecs_attr =
493 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
494 alloc_sleep_millisecs_store);
496 static ssize_t pages_to_scan_show(struct kobject *kobj,
497 struct kobj_attribute *attr,
500 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
502 static ssize_t pages_to_scan_store(struct kobject *kobj,
503 struct kobj_attribute *attr,
504 const char *buf, size_t count)
509 err = kstrtoul(buf, 10, &pages);
510 if (err || !pages || pages > UINT_MAX)
513 khugepaged_pages_to_scan = pages;
517 static struct kobj_attribute pages_to_scan_attr =
518 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
519 pages_to_scan_store);
521 static ssize_t pages_collapsed_show(struct kobject *kobj,
522 struct kobj_attribute *attr,
525 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
527 static struct kobj_attribute pages_collapsed_attr =
528 __ATTR_RO(pages_collapsed);
530 static ssize_t full_scans_show(struct kobject *kobj,
531 struct kobj_attribute *attr,
534 return sprintf(buf, "%u\n", khugepaged_full_scans);
536 static struct kobj_attribute full_scans_attr =
537 __ATTR_RO(full_scans);
539 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
540 struct kobj_attribute *attr, char *buf)
542 return single_flag_show(kobj, attr, buf,
543 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
545 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
546 struct kobj_attribute *attr,
547 const char *buf, size_t count)
549 return single_flag_store(kobj, attr, buf, count,
550 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
552 static struct kobj_attribute khugepaged_defrag_attr =
553 __ATTR(defrag, 0644, khugepaged_defrag_show,
554 khugepaged_defrag_store);
557 * max_ptes_none controls if khugepaged should collapse hugepages over
558 * any unmapped ptes in turn potentially increasing the memory
559 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
560 * reduce the available free memory in the system as it
561 * runs. Increasing max_ptes_none will instead potentially reduce the
562 * free memory in the system during the khugepaged scan.
564 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
565 struct kobj_attribute *attr,
568 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
570 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
571 struct kobj_attribute *attr,
572 const char *buf, size_t count)
575 unsigned long max_ptes_none;
577 err = kstrtoul(buf, 10, &max_ptes_none);
578 if (err || max_ptes_none > HPAGE_PMD_NR-1)
581 khugepaged_max_ptes_none = max_ptes_none;
585 static struct kobj_attribute khugepaged_max_ptes_none_attr =
586 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
587 khugepaged_max_ptes_none_store);
589 static struct attribute *khugepaged_attr[] = {
590 &khugepaged_defrag_attr.attr,
591 &khugepaged_max_ptes_none_attr.attr,
592 &pages_to_scan_attr.attr,
593 &pages_collapsed_attr.attr,
594 &full_scans_attr.attr,
595 &scan_sleep_millisecs_attr.attr,
596 &alloc_sleep_millisecs_attr.attr,
600 static struct attribute_group khugepaged_attr_group = {
601 .attrs = khugepaged_attr,
602 .name = "khugepaged",
605 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
609 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
610 if (unlikely(!*hugepage_kobj)) {
611 pr_err("failed to create transparent hugepage kobject\n");
615 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
617 pr_err("failed to register transparent hugepage group\n");
621 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
623 pr_err("failed to register transparent hugepage group\n");
624 goto remove_hp_group;
630 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
632 kobject_put(*hugepage_kobj);
636 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
638 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
639 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
640 kobject_put(hugepage_kobj);
643 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
648 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
651 #endif /* CONFIG_SYSFS */
653 static int __init hugepage_init(void)
656 struct kobject *hugepage_kobj;
658 if (!has_transparent_hugepage()) {
659 transparent_hugepage_flags = 0;
663 err = hugepage_init_sysfs(&hugepage_kobj);
667 err = khugepaged_slab_init();
671 err = register_shrinker(&huge_zero_page_shrinker);
673 goto err_hzp_shrinker;
674 err = register_shrinker(&deferred_split_shrinker);
676 goto err_split_shrinker;
679 * By default disable transparent hugepages on smaller systems,
680 * where the extra memory used could hurt more than TLB overhead
681 * is likely to save. The admin can still enable it through /sys.
683 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
684 transparent_hugepage_flags = 0;
688 err = start_stop_khugepaged();
694 unregister_shrinker(&deferred_split_shrinker);
696 unregister_shrinker(&huge_zero_page_shrinker);
698 khugepaged_slab_exit();
700 hugepage_exit_sysfs(hugepage_kobj);
704 subsys_initcall(hugepage_init);
706 static int __init setup_transparent_hugepage(char *str)
711 if (!strcmp(str, "always")) {
712 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
713 &transparent_hugepage_flags);
714 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
715 &transparent_hugepage_flags);
717 } else if (!strcmp(str, "madvise")) {
718 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
719 &transparent_hugepage_flags);
720 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
721 &transparent_hugepage_flags);
723 } else if (!strcmp(str, "never")) {
724 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
725 &transparent_hugepage_flags);
726 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
727 &transparent_hugepage_flags);
732 pr_warn("transparent_hugepage= cannot parse, ignored\n");
735 __setup("transparent_hugepage=", setup_transparent_hugepage);
737 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
739 if (likely(vma->vm_flags & VM_WRITE))
740 pmd = pmd_mkwrite(pmd);
744 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
747 entry = mk_pmd(page, prot);
748 entry = pmd_mkhuge(entry);
752 static inline struct list_head *page_deferred_list(struct page *page)
755 * ->lru in the tail pages is occupied by compound_head.
756 * Let's use ->mapping + ->index in the second tail page as list_head.
758 return (struct list_head *)&page[2].mapping;
761 void prep_transhuge_page(struct page *page)
764 * we use page->mapping and page->indexlru in second tail page
765 * as list_head: assuming THP order >= 2
767 BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
769 INIT_LIST_HEAD(page_deferred_list(page));
770 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
773 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
774 struct vm_area_struct *vma,
775 unsigned long address, pmd_t *pmd,
776 struct page *page, gfp_t gfp,
779 struct mem_cgroup *memcg;
782 unsigned long haddr = address & HPAGE_PMD_MASK;
784 VM_BUG_ON_PAGE(!PageCompound(page), page);
786 if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) {
788 count_vm_event(THP_FAULT_FALLBACK);
789 return VM_FAULT_FALLBACK;
792 pgtable = pte_alloc_one(mm, haddr);
793 if (unlikely(!pgtable)) {
794 mem_cgroup_cancel_charge(page, memcg, true);
799 clear_huge_page(page, haddr, HPAGE_PMD_NR);
801 * The memory barrier inside __SetPageUptodate makes sure that
802 * clear_huge_page writes become visible before the set_pmd_at()
805 __SetPageUptodate(page);
807 ptl = pmd_lock(mm, pmd);
808 if (unlikely(!pmd_none(*pmd))) {
810 mem_cgroup_cancel_charge(page, memcg, true);
812 pte_free(mm, pgtable);
816 /* Deliver the page fault to userland */
817 if (userfaultfd_missing(vma)) {
821 mem_cgroup_cancel_charge(page, memcg, true);
823 pte_free(mm, pgtable);
824 ret = handle_userfault(vma, address, flags,
826 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
830 entry = mk_huge_pmd(page, vma->vm_page_prot);
831 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
832 page_add_new_anon_rmap(page, vma, haddr, true);
833 mem_cgroup_commit_charge(page, memcg, false, true);
834 lru_cache_add_active_or_unevictable(page, vma);
835 pgtable_trans_huge_deposit(mm, pmd, pgtable);
836 set_pmd_at(mm, haddr, pmd, entry);
837 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
838 atomic_long_inc(&mm->nr_ptes);
840 count_vm_event(THP_FAULT_ALLOC);
846 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
848 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_RECLAIM)) | extra_gfp;
851 /* Caller must hold page table lock. */
852 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
853 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
854 struct page *zero_page)
859 entry = mk_pmd(zero_page, vma->vm_page_prot);
860 entry = pmd_mkhuge(entry);
861 pgtable_trans_huge_deposit(mm, pmd, pgtable);
862 set_pmd_at(mm, haddr, pmd, entry);
863 atomic_long_inc(&mm->nr_ptes);
867 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
868 unsigned long address, pmd_t *pmd,
873 unsigned long haddr = address & HPAGE_PMD_MASK;
875 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
876 return VM_FAULT_FALLBACK;
877 if (unlikely(anon_vma_prepare(vma)))
879 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
881 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
882 transparent_hugepage_use_zero_page()) {
885 struct page *zero_page;
888 pgtable = pte_alloc_one(mm, haddr);
889 if (unlikely(!pgtable))
891 zero_page = get_huge_zero_page();
892 if (unlikely(!zero_page)) {
893 pte_free(mm, pgtable);
894 count_vm_event(THP_FAULT_FALLBACK);
895 return VM_FAULT_FALLBACK;
897 ptl = pmd_lock(mm, pmd);
900 if (pmd_none(*pmd)) {
901 if (userfaultfd_missing(vma)) {
903 ret = handle_userfault(vma, address, flags,
905 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
907 set_huge_zero_page(pgtable, mm, vma,
916 pte_free(mm, pgtable);
917 put_huge_zero_page();
921 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
922 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
923 if (unlikely(!page)) {
924 count_vm_event(THP_FAULT_FALLBACK);
925 return VM_FAULT_FALLBACK;
927 prep_transhuge_page(page);
928 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
932 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
933 pmd_t *pmd, unsigned long pfn, pgprot_t prot, bool write)
935 struct mm_struct *mm = vma->vm_mm;
939 ptl = pmd_lock(mm, pmd);
940 if (pmd_none(*pmd)) {
941 entry = pmd_mkhuge(pfn_pmd(pfn, prot));
943 entry = pmd_mkyoung(pmd_mkdirty(entry));
944 entry = maybe_pmd_mkwrite(entry, vma);
946 set_pmd_at(mm, addr, pmd, entry);
947 update_mmu_cache_pmd(vma, addr, pmd);
952 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
953 pmd_t *pmd, unsigned long pfn, bool write)
955 pgprot_t pgprot = vma->vm_page_prot;
957 * If we had pmd_special, we could avoid all these restrictions,
958 * but we need to be consistent with PTEs and architectures that
959 * can't support a 'special' bit.
961 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
962 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
963 (VM_PFNMAP|VM_MIXEDMAP));
964 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
965 BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
967 if (addr < vma->vm_start || addr >= vma->vm_end)
968 return VM_FAULT_SIGBUS;
969 if (track_pfn_insert(vma, &pgprot, pfn))
970 return VM_FAULT_SIGBUS;
971 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
972 return VM_FAULT_NOPAGE;
975 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
976 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
977 struct vm_area_struct *vma)
979 spinlock_t *dst_ptl, *src_ptl;
980 struct page *src_page;
986 pgtable = pte_alloc_one(dst_mm, addr);
987 if (unlikely(!pgtable))
990 dst_ptl = pmd_lock(dst_mm, dst_pmd);
991 src_ptl = pmd_lockptr(src_mm, src_pmd);
992 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
996 if (unlikely(!pmd_trans_huge(pmd))) {
997 pte_free(dst_mm, pgtable);
1001 * When page table lock is held, the huge zero pmd should not be
1002 * under splitting since we don't split the page itself, only pmd to
1005 if (is_huge_zero_pmd(pmd)) {
1006 struct page *zero_page;
1008 * get_huge_zero_page() will never allocate a new page here,
1009 * since we already have a zero page to copy. It just takes a
1012 zero_page = get_huge_zero_page();
1013 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1019 src_page = pmd_page(pmd);
1020 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1022 page_dup_rmap(src_page, true);
1023 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1025 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1026 pmd = pmd_mkold(pmd_wrprotect(pmd));
1027 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1028 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1029 atomic_long_inc(&dst_mm->nr_ptes);
1033 spin_unlock(src_ptl);
1034 spin_unlock(dst_ptl);
1039 void huge_pmd_set_accessed(struct mm_struct *mm,
1040 struct vm_area_struct *vma,
1041 unsigned long address,
1042 pmd_t *pmd, pmd_t orig_pmd,
1047 unsigned long haddr;
1049 ptl = pmd_lock(mm, pmd);
1050 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1053 entry = pmd_mkyoung(orig_pmd);
1054 haddr = address & HPAGE_PMD_MASK;
1055 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1056 update_mmu_cache_pmd(vma, address, pmd);
1062 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1063 struct vm_area_struct *vma,
1064 unsigned long address,
1065 pmd_t *pmd, pmd_t orig_pmd,
1067 unsigned long haddr)
1069 struct mem_cgroup *memcg;
1074 struct page **pages;
1075 unsigned long mmun_start; /* For mmu_notifiers */
1076 unsigned long mmun_end; /* For mmu_notifiers */
1078 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1080 if (unlikely(!pages)) {
1081 ret |= VM_FAULT_OOM;
1085 for (i = 0; i < HPAGE_PMD_NR; i++) {
1086 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1088 vma, address, page_to_nid(page));
1089 if (unlikely(!pages[i] ||
1090 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1095 memcg = (void *)page_private(pages[i]);
1096 set_page_private(pages[i], 0);
1097 mem_cgroup_cancel_charge(pages[i], memcg,
1102 ret |= VM_FAULT_OOM;
1105 set_page_private(pages[i], (unsigned long)memcg);
1108 for (i = 0; i < HPAGE_PMD_NR; i++) {
1109 copy_user_highpage(pages[i], page + i,
1110 haddr + PAGE_SIZE * i, vma);
1111 __SetPageUptodate(pages[i]);
1116 mmun_end = haddr + HPAGE_PMD_SIZE;
1117 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1119 ptl = pmd_lock(mm, pmd);
1120 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1121 goto out_free_pages;
1122 VM_BUG_ON_PAGE(!PageHead(page), page);
1124 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1125 /* leave pmd empty until pte is filled */
1127 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1128 pmd_populate(mm, &_pmd, pgtable);
1130 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1132 entry = mk_pte(pages[i], vma->vm_page_prot);
1133 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1134 memcg = (void *)page_private(pages[i]);
1135 set_page_private(pages[i], 0);
1136 page_add_new_anon_rmap(pages[i], vma, haddr, false);
1137 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1138 lru_cache_add_active_or_unevictable(pages[i], vma);
1139 pte = pte_offset_map(&_pmd, haddr);
1140 VM_BUG_ON(!pte_none(*pte));
1141 set_pte_at(mm, haddr, pte, entry);
1146 smp_wmb(); /* make pte visible before pmd */
1147 pmd_populate(mm, pmd, pgtable);
1148 page_remove_rmap(page, true);
1151 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1153 ret |= VM_FAULT_WRITE;
1161 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1162 for (i = 0; i < HPAGE_PMD_NR; i++) {
1163 memcg = (void *)page_private(pages[i]);
1164 set_page_private(pages[i], 0);
1165 mem_cgroup_cancel_charge(pages[i], memcg, false);
1172 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1173 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1177 struct page *page = NULL, *new_page;
1178 struct mem_cgroup *memcg;
1179 unsigned long haddr;
1180 unsigned long mmun_start; /* For mmu_notifiers */
1181 unsigned long mmun_end; /* For mmu_notifiers */
1182 gfp_t huge_gfp; /* for allocation and charge */
1184 ptl = pmd_lockptr(mm, pmd);
1185 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1186 haddr = address & HPAGE_PMD_MASK;
1187 if (is_huge_zero_pmd(orig_pmd))
1190 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1193 page = pmd_page(orig_pmd);
1194 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1196 * We can only reuse the page if nobody else maps the huge page or it's
1197 * part. We can do it by checking page_mapcount() on each sub-page, but
1199 * The cheaper way is to check page_count() to be equal 1: every
1200 * mapcount takes page reference reference, so this way we can
1201 * guarantee, that the PMD is the only mapping.
1202 * This can give false negative if somebody pinned the page, but that's
1205 if (page_mapcount(page) == 1 && page_count(page) == 1) {
1207 entry = pmd_mkyoung(orig_pmd);
1208 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1209 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1210 update_mmu_cache_pmd(vma, address, pmd);
1211 ret |= VM_FAULT_WRITE;
1217 if (transparent_hugepage_enabled(vma) &&
1218 !transparent_hugepage_debug_cow()) {
1219 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1220 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1224 if (likely(new_page)) {
1225 prep_transhuge_page(new_page);
1228 split_huge_pmd(vma, pmd, address);
1229 ret |= VM_FAULT_FALLBACK;
1231 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1232 pmd, orig_pmd, page, haddr);
1233 if (ret & VM_FAULT_OOM) {
1234 split_huge_pmd(vma, pmd, address);
1235 ret |= VM_FAULT_FALLBACK;
1239 count_vm_event(THP_FAULT_FALLBACK);
1243 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg,
1247 split_huge_pmd(vma, pmd, address);
1250 split_huge_pmd(vma, pmd, address);
1251 ret |= VM_FAULT_FALLBACK;
1252 count_vm_event(THP_FAULT_FALLBACK);
1256 count_vm_event(THP_FAULT_ALLOC);
1259 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1261 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1262 __SetPageUptodate(new_page);
1265 mmun_end = haddr + HPAGE_PMD_SIZE;
1266 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1271 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1273 mem_cgroup_cancel_charge(new_page, memcg, true);
1278 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1279 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1280 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1281 page_add_new_anon_rmap(new_page, vma, haddr, true);
1282 mem_cgroup_commit_charge(new_page, memcg, false, true);
1283 lru_cache_add_active_or_unevictable(new_page, vma);
1284 set_pmd_at(mm, haddr, pmd, entry);
1285 update_mmu_cache_pmd(vma, address, pmd);
1287 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1288 put_huge_zero_page();
1290 VM_BUG_ON_PAGE(!PageHead(page), page);
1291 page_remove_rmap(page, true);
1294 ret |= VM_FAULT_WRITE;
1298 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1306 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1311 struct mm_struct *mm = vma->vm_mm;
1312 struct page *page = NULL;
1314 assert_spin_locked(pmd_lockptr(mm, pmd));
1316 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1319 /* Avoid dumping huge zero page */
1320 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1321 return ERR_PTR(-EFAULT);
1323 /* Full NUMA hinting faults to serialise migration in fault paths */
1324 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1327 page = pmd_page(*pmd);
1328 VM_BUG_ON_PAGE(!PageHead(page), page);
1329 if (flags & FOLL_TOUCH) {
1332 * We should set the dirty bit only for FOLL_WRITE but
1333 * for now the dirty bit in the pmd is meaningless.
1334 * And if the dirty bit will become meaningful and
1335 * we'll only set it with FOLL_WRITE, an atomic
1336 * set_bit will be required on the pmd to set the
1337 * young bit, instead of the current set_pmd_at.
1339 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1340 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1342 update_mmu_cache_pmd(vma, addr, pmd);
1344 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1346 * We don't mlock() pte-mapped THPs. This way we can avoid
1347 * leaking mlocked pages into non-VM_LOCKED VMAs.
1349 * In most cases the pmd is the only mapping of the page as we
1350 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1351 * writable private mappings in populate_vma_page_range().
1353 * The only scenario when we have the page shared here is if we
1354 * mlocking read-only mapping shared over fork(). We skip
1355 * mlocking such pages.
1357 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) &&
1358 page->mapping && trylock_page(page)) {
1361 mlock_vma_page(page);
1365 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1366 VM_BUG_ON_PAGE(!PageCompound(page), page);
1367 if (flags & FOLL_GET)
1374 /* NUMA hinting page fault entry point for trans huge pmds */
1375 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1376 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1379 struct anon_vma *anon_vma = NULL;
1381 unsigned long haddr = addr & HPAGE_PMD_MASK;
1382 int page_nid = -1, this_nid = numa_node_id();
1383 int target_nid, last_cpupid = -1;
1385 bool migrated = false;
1389 /* A PROT_NONE fault should not end up here */
1390 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1392 ptl = pmd_lock(mm, pmdp);
1393 if (unlikely(!pmd_same(pmd, *pmdp)))
1397 * If there are potential migrations, wait for completion and retry
1398 * without disrupting NUMA hinting information. Do not relock and
1399 * check_same as the page may no longer be mapped.
1401 if (unlikely(pmd_trans_migrating(*pmdp))) {
1402 page = pmd_page(*pmdp);
1404 wait_on_page_locked(page);
1408 page = pmd_page(pmd);
1409 BUG_ON(is_huge_zero_page(page));
1410 page_nid = page_to_nid(page);
1411 last_cpupid = page_cpupid_last(page);
1412 count_vm_numa_event(NUMA_HINT_FAULTS);
1413 if (page_nid == this_nid) {
1414 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1415 flags |= TNF_FAULT_LOCAL;
1418 /* See similar comment in do_numa_page for explanation */
1419 if (!(vma->vm_flags & VM_WRITE))
1420 flags |= TNF_NO_GROUP;
1423 * Acquire the page lock to serialise THP migrations but avoid dropping
1424 * page_table_lock if at all possible
1426 page_locked = trylock_page(page);
1427 target_nid = mpol_misplaced(page, vma, haddr);
1428 if (target_nid == -1) {
1429 /* If the page was locked, there are no parallel migrations */
1434 /* Migration could have started since the pmd_trans_migrating check */
1437 wait_on_page_locked(page);
1443 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1444 * to serialises splits
1448 anon_vma = page_lock_anon_vma_read(page);
1450 /* Confirm the PMD did not change while page_table_lock was released */
1452 if (unlikely(!pmd_same(pmd, *pmdp))) {
1459 /* Bail if we fail to protect against THP splits for any reason */
1460 if (unlikely(!anon_vma)) {
1467 * Migrate the THP to the requested node, returns with page unlocked
1468 * and access rights restored.
1471 migrated = migrate_misplaced_transhuge_page(mm, vma,
1472 pmdp, pmd, addr, page, target_nid);
1474 flags |= TNF_MIGRATED;
1475 page_nid = target_nid;
1477 flags |= TNF_MIGRATE_FAIL;
1481 BUG_ON(!PageLocked(page));
1482 was_writable = pmd_write(pmd);
1483 pmd = pmd_modify(pmd, vma->vm_page_prot);
1484 pmd = pmd_mkyoung(pmd);
1486 pmd = pmd_mkwrite(pmd);
1487 set_pmd_at(mm, haddr, pmdp, pmd);
1488 update_mmu_cache_pmd(vma, addr, pmdp);
1495 page_unlock_anon_vma_read(anon_vma);
1498 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1503 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1504 pmd_t *pmd, unsigned long addr)
1509 if (!__pmd_trans_huge_lock(pmd, vma, &ptl))
1512 * For architectures like ppc64 we look at deposited pgtable
1513 * when calling pmdp_huge_get_and_clear. So do the
1514 * pgtable_trans_huge_withdraw after finishing pmdp related
1517 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1519 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1520 if (vma_is_dax(vma)) {
1522 if (is_huge_zero_pmd(orig_pmd))
1523 put_huge_zero_page();
1524 } else if (is_huge_zero_pmd(orig_pmd)) {
1525 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1526 atomic_long_dec(&tlb->mm->nr_ptes);
1528 put_huge_zero_page();
1530 struct page *page = pmd_page(orig_pmd);
1531 page_remove_rmap(page, true);
1532 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1533 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1534 VM_BUG_ON_PAGE(!PageHead(page), page);
1535 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1536 atomic_long_dec(&tlb->mm->nr_ptes);
1538 tlb_remove_page(tlb, page);
1543 bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1544 unsigned long old_addr,
1545 unsigned long new_addr, unsigned long old_end,
1546 pmd_t *old_pmd, pmd_t *new_pmd)
1548 spinlock_t *old_ptl, *new_ptl;
1551 struct mm_struct *mm = vma->vm_mm;
1553 if ((old_addr & ~HPAGE_PMD_MASK) ||
1554 (new_addr & ~HPAGE_PMD_MASK) ||
1555 old_end - old_addr < HPAGE_PMD_SIZE ||
1556 (new_vma->vm_flags & VM_NOHUGEPAGE))
1560 * The destination pmd shouldn't be established, free_pgtables()
1561 * should have release it.
1563 if (WARN_ON(!pmd_none(*new_pmd))) {
1564 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1569 * We don't have to worry about the ordering of src and dst
1570 * ptlocks because exclusive mmap_sem prevents deadlock.
1572 if (__pmd_trans_huge_lock(old_pmd, vma, &old_ptl)) {
1573 new_ptl = pmd_lockptr(mm, new_pmd);
1574 if (new_ptl != old_ptl)
1575 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1576 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1577 VM_BUG_ON(!pmd_none(*new_pmd));
1579 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1581 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1582 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1584 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1585 if (new_ptl != old_ptl)
1586 spin_unlock(new_ptl);
1587 spin_unlock(old_ptl);
1595 * - 0 if PMD could not be locked
1596 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1597 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1599 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1600 unsigned long addr, pgprot_t newprot, int prot_numa)
1602 struct mm_struct *mm = vma->vm_mm;
1606 if (__pmd_trans_huge_lock(pmd, vma, &ptl)) {
1608 bool preserve_write = prot_numa && pmd_write(*pmd);
1612 * Avoid trapping faults against the zero page. The read-only
1613 * data is likely to be read-cached on the local CPU and
1614 * local/remote hits to the zero page are not interesting.
1616 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1621 if (!prot_numa || !pmd_protnone(*pmd)) {
1622 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1623 entry = pmd_modify(entry, newprot);
1625 entry = pmd_mkwrite(entry);
1627 set_pmd_at(mm, addr, pmd, entry);
1628 BUG_ON(!preserve_write && pmd_write(entry));
1637 * Returns true if a given pmd maps a thp, false otherwise.
1639 * Note that if it returns true, this routine returns without unlocking page
1640 * table lock. So callers must unlock it.
1642 bool __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1645 *ptl = pmd_lock(vma->vm_mm, pmd);
1646 if (likely(pmd_trans_huge(*pmd)))
1652 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1654 int hugepage_madvise(struct vm_area_struct *vma,
1655 unsigned long *vm_flags, int advice)
1661 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1662 * can't handle this properly after s390_enable_sie, so we simply
1663 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1665 if (mm_has_pgste(vma->vm_mm))
1669 * Be somewhat over-protective like KSM for now!
1671 if (*vm_flags & VM_NO_THP)
1673 *vm_flags &= ~VM_NOHUGEPAGE;
1674 *vm_flags |= VM_HUGEPAGE;
1676 * If the vma become good for khugepaged to scan,
1677 * register it here without waiting a page fault that
1678 * may not happen any time soon.
1680 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1683 case MADV_NOHUGEPAGE:
1685 * Be somewhat over-protective like KSM for now!
1687 if (*vm_flags & VM_NO_THP)
1689 *vm_flags &= ~VM_HUGEPAGE;
1690 *vm_flags |= VM_NOHUGEPAGE;
1692 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1693 * this vma even if we leave the mm registered in khugepaged if
1694 * it got registered before VM_NOHUGEPAGE was set.
1702 static int __init khugepaged_slab_init(void)
1704 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1705 sizeof(struct mm_slot),
1706 __alignof__(struct mm_slot), 0, NULL);
1713 static void __init khugepaged_slab_exit(void)
1715 kmem_cache_destroy(mm_slot_cache);
1718 static inline struct mm_slot *alloc_mm_slot(void)
1720 if (!mm_slot_cache) /* initialization failed */
1722 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1725 static inline void free_mm_slot(struct mm_slot *mm_slot)
1727 kmem_cache_free(mm_slot_cache, mm_slot);
1730 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1732 struct mm_slot *mm_slot;
1734 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1735 if (mm == mm_slot->mm)
1741 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1742 struct mm_slot *mm_slot)
1745 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1748 static inline int khugepaged_test_exit(struct mm_struct *mm)
1750 return atomic_read(&mm->mm_users) == 0;
1753 int __khugepaged_enter(struct mm_struct *mm)
1755 struct mm_slot *mm_slot;
1758 mm_slot = alloc_mm_slot();
1762 /* __khugepaged_exit() must not run from under us */
1763 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1764 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1765 free_mm_slot(mm_slot);
1769 spin_lock(&khugepaged_mm_lock);
1770 insert_to_mm_slots_hash(mm, mm_slot);
1772 * Insert just behind the scanning cursor, to let the area settle
1775 wakeup = list_empty(&khugepaged_scan.mm_head);
1776 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1777 spin_unlock(&khugepaged_mm_lock);
1779 atomic_inc(&mm->mm_count);
1781 wake_up_interruptible(&khugepaged_wait);
1786 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1787 unsigned long vm_flags)
1789 unsigned long hstart, hend;
1792 * Not yet faulted in so we will register later in the
1793 * page fault if needed.
1797 /* khugepaged not yet working on file or special mappings */
1799 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
1800 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1801 hend = vma->vm_end & HPAGE_PMD_MASK;
1803 return khugepaged_enter(vma, vm_flags);
1807 void __khugepaged_exit(struct mm_struct *mm)
1809 struct mm_slot *mm_slot;
1812 spin_lock(&khugepaged_mm_lock);
1813 mm_slot = get_mm_slot(mm);
1814 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1815 hash_del(&mm_slot->hash);
1816 list_del(&mm_slot->mm_node);
1819 spin_unlock(&khugepaged_mm_lock);
1822 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1823 free_mm_slot(mm_slot);
1825 } else if (mm_slot) {
1827 * This is required to serialize against
1828 * khugepaged_test_exit() (which is guaranteed to run
1829 * under mmap sem read mode). Stop here (after we
1830 * return all pagetables will be destroyed) until
1831 * khugepaged has finished working on the pagetables
1832 * under the mmap_sem.
1834 down_write(&mm->mmap_sem);
1835 up_write(&mm->mmap_sem);
1839 static void release_pte_page(struct page *page)
1841 /* 0 stands for page_is_file_cache(page) == false */
1842 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1844 putback_lru_page(page);
1847 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1849 while (--_pte >= pte) {
1850 pte_t pteval = *_pte;
1851 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
1852 release_pte_page(pte_page(pteval));
1856 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1857 unsigned long address,
1860 struct page *page = NULL;
1862 int none_or_zero = 0, result = 0;
1863 bool referenced = false, writable = false;
1865 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1866 _pte++, address += PAGE_SIZE) {
1867 pte_t pteval = *_pte;
1868 if (pte_none(pteval) || (pte_present(pteval) &&
1869 is_zero_pfn(pte_pfn(pteval)))) {
1870 if (!userfaultfd_armed(vma) &&
1871 ++none_or_zero <= khugepaged_max_ptes_none) {
1874 result = SCAN_EXCEED_NONE_PTE;
1878 if (!pte_present(pteval)) {
1879 result = SCAN_PTE_NON_PRESENT;
1882 page = vm_normal_page(vma, address, pteval);
1883 if (unlikely(!page)) {
1884 result = SCAN_PAGE_NULL;
1888 VM_BUG_ON_PAGE(PageCompound(page), page);
1889 VM_BUG_ON_PAGE(!PageAnon(page), page);
1890 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1893 * We can do it before isolate_lru_page because the
1894 * page can't be freed from under us. NOTE: PG_lock
1895 * is needed to serialize against split_huge_page
1896 * when invoked from the VM.
1898 if (!trylock_page(page)) {
1899 result = SCAN_PAGE_LOCK;
1904 * cannot use mapcount: can't collapse if there's a gup pin.
1905 * The page must only be referenced by the scanned process
1906 * and page swap cache.
1908 if (page_count(page) != 1 + !!PageSwapCache(page)) {
1910 result = SCAN_PAGE_COUNT;
1913 if (pte_write(pteval)) {
1916 if (PageSwapCache(page) && !reuse_swap_page(page)) {
1918 result = SCAN_SWAP_CACHE_PAGE;
1922 * Page is not in the swap cache. It can be collapsed
1928 * Isolate the page to avoid collapsing an hugepage
1929 * currently in use by the VM.
1931 if (isolate_lru_page(page)) {
1933 result = SCAN_DEL_PAGE_LRU;
1936 /* 0 stands for page_is_file_cache(page) == false */
1937 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1938 VM_BUG_ON_PAGE(!PageLocked(page), page);
1939 VM_BUG_ON_PAGE(PageLRU(page), page);
1941 /* If there is no mapped pte young don't collapse the page */
1942 if (pte_young(pteval) ||
1943 page_is_young(page) || PageReferenced(page) ||
1944 mmu_notifier_test_young(vma->vm_mm, address))
1947 if (likely(writable)) {
1948 if (likely(referenced)) {
1949 result = SCAN_SUCCEED;
1950 trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
1951 referenced, writable, result);
1955 result = SCAN_PAGE_RO;
1959 release_pte_pages(pte, _pte);
1960 trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
1961 referenced, writable, result);
1965 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1966 struct vm_area_struct *vma,
1967 unsigned long address,
1971 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1972 pte_t pteval = *_pte;
1973 struct page *src_page;
1975 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1976 clear_user_highpage(page, address);
1977 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1978 if (is_zero_pfn(pte_pfn(pteval))) {
1980 * ptl mostly unnecessary.
1984 * paravirt calls inside pte_clear here are
1987 pte_clear(vma->vm_mm, address, _pte);
1991 src_page = pte_page(pteval);
1992 copy_user_highpage(page, src_page, address, vma);
1993 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
1994 release_pte_page(src_page);
1996 * ptl mostly unnecessary, but preempt has to
1997 * be disabled to update the per-cpu stats
1998 * inside page_remove_rmap().
2002 * paravirt calls inside pte_clear here are
2005 pte_clear(vma->vm_mm, address, _pte);
2006 page_remove_rmap(src_page, false);
2008 free_page_and_swap_cache(src_page);
2011 address += PAGE_SIZE;
2016 static void khugepaged_alloc_sleep(void)
2020 add_wait_queue(&khugepaged_wait, &wait);
2021 freezable_schedule_timeout_interruptible(
2022 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2023 remove_wait_queue(&khugepaged_wait, &wait);
2026 static int khugepaged_node_load[MAX_NUMNODES];
2028 static bool khugepaged_scan_abort(int nid)
2033 * If zone_reclaim_mode is disabled, then no extra effort is made to
2034 * allocate memory locally.
2036 if (!zone_reclaim_mode)
2039 /* If there is a count for this node already, it must be acceptable */
2040 if (khugepaged_node_load[nid])
2043 for (i = 0; i < MAX_NUMNODES; i++) {
2044 if (!khugepaged_node_load[i])
2046 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2053 static int khugepaged_find_target_node(void)
2055 static int last_khugepaged_target_node = NUMA_NO_NODE;
2056 int nid, target_node = 0, max_value = 0;
2058 /* find first node with max normal pages hit */
2059 for (nid = 0; nid < MAX_NUMNODES; nid++)
2060 if (khugepaged_node_load[nid] > max_value) {
2061 max_value = khugepaged_node_load[nid];
2065 /* do some balance if several nodes have the same hit record */
2066 if (target_node <= last_khugepaged_target_node)
2067 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2069 if (max_value == khugepaged_node_load[nid]) {
2074 last_khugepaged_target_node = target_node;
2078 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2080 if (IS_ERR(*hpage)) {
2086 khugepaged_alloc_sleep();
2087 } else if (*hpage) {
2095 static struct page *
2096 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2097 unsigned long address, int node)
2099 VM_BUG_ON_PAGE(*hpage, *hpage);
2102 * Before allocating the hugepage, release the mmap_sem read lock.
2103 * The allocation can take potentially a long time if it involves
2104 * sync compaction, and we do not need to hold the mmap_sem during
2105 * that. We will recheck the vma after taking it again in write mode.
2107 up_read(&mm->mmap_sem);
2109 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2110 if (unlikely(!*hpage)) {
2111 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2112 *hpage = ERR_PTR(-ENOMEM);
2116 prep_transhuge_page(*hpage);
2117 count_vm_event(THP_COLLAPSE_ALLOC);
2121 static int khugepaged_find_target_node(void)
2126 static inline struct page *alloc_hugepage(int defrag)
2130 page = alloc_pages(alloc_hugepage_gfpmask(defrag, 0), HPAGE_PMD_ORDER);
2132 prep_transhuge_page(page);
2136 static struct page *khugepaged_alloc_hugepage(bool *wait)
2141 hpage = alloc_hugepage(khugepaged_defrag());
2143 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2148 khugepaged_alloc_sleep();
2150 count_vm_event(THP_COLLAPSE_ALLOC);
2151 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2156 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2159 *hpage = khugepaged_alloc_hugepage(wait);
2161 if (unlikely(!*hpage))
2167 static struct page *
2168 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2169 unsigned long address, int node)
2171 up_read(&mm->mmap_sem);
2178 static bool hugepage_vma_check(struct vm_area_struct *vma)
2180 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2181 (vma->vm_flags & VM_NOHUGEPAGE))
2183 if (!vma->anon_vma || vma->vm_ops)
2185 if (is_vma_temporary_stack(vma))
2187 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2191 static void collapse_huge_page(struct mm_struct *mm,
2192 unsigned long address,
2193 struct page **hpage,
2194 struct vm_area_struct *vma,
2200 struct page *new_page;
2201 spinlock_t *pmd_ptl, *pte_ptl;
2202 int isolated, result = 0;
2203 unsigned long hstart, hend;
2204 struct mem_cgroup *memcg;
2205 unsigned long mmun_start; /* For mmu_notifiers */
2206 unsigned long mmun_end; /* For mmu_notifiers */
2209 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2211 /* Only allocate from the target node */
2212 gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2215 /* release the mmap_sem read lock. */
2216 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2218 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2222 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2223 result = SCAN_CGROUP_CHARGE_FAIL;
2228 * Prevent all access to pagetables with the exception of
2229 * gup_fast later hanlded by the ptep_clear_flush and the VM
2230 * handled by the anon_vma lock + PG_lock.
2232 down_write(&mm->mmap_sem);
2233 if (unlikely(khugepaged_test_exit(mm))) {
2234 result = SCAN_ANY_PROCESS;
2238 vma = find_vma(mm, address);
2240 result = SCAN_VMA_NULL;
2243 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2244 hend = vma->vm_end & HPAGE_PMD_MASK;
2245 if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
2246 result = SCAN_ADDRESS_RANGE;
2249 if (!hugepage_vma_check(vma)) {
2250 result = SCAN_VMA_CHECK;
2253 pmd = mm_find_pmd(mm, address);
2255 result = SCAN_PMD_NULL;
2259 anon_vma_lock_write(vma->anon_vma);
2261 pte = pte_offset_map(pmd, address);
2262 pte_ptl = pte_lockptr(mm, pmd);
2264 mmun_start = address;
2265 mmun_end = address + HPAGE_PMD_SIZE;
2266 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2267 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2269 * After this gup_fast can't run anymore. This also removes
2270 * any huge TLB entry from the CPU so we won't allow
2271 * huge and small TLB entries for the same virtual address
2272 * to avoid the risk of CPU bugs in that area.
2274 _pmd = pmdp_collapse_flush(vma, address, pmd);
2275 spin_unlock(pmd_ptl);
2276 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2279 isolated = __collapse_huge_page_isolate(vma, address, pte);
2280 spin_unlock(pte_ptl);
2282 if (unlikely(!isolated)) {
2285 BUG_ON(!pmd_none(*pmd));
2287 * We can only use set_pmd_at when establishing
2288 * hugepmds and never for establishing regular pmds that
2289 * points to regular pagetables. Use pmd_populate for that
2291 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2292 spin_unlock(pmd_ptl);
2293 anon_vma_unlock_write(vma->anon_vma);
2299 * All pages are isolated and locked so anon_vma rmap
2300 * can't run anymore.
2302 anon_vma_unlock_write(vma->anon_vma);
2304 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2306 __SetPageUptodate(new_page);
2307 pgtable = pmd_pgtable(_pmd);
2309 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2310 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2313 * spin_lock() below is not the equivalent of smp_wmb(), so
2314 * this is needed to avoid the copy_huge_page writes to become
2315 * visible after the set_pmd_at() write.
2320 BUG_ON(!pmd_none(*pmd));
2321 page_add_new_anon_rmap(new_page, vma, address, true);
2322 mem_cgroup_commit_charge(new_page, memcg, false, true);
2323 lru_cache_add_active_or_unevictable(new_page, vma);
2324 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2325 set_pmd_at(mm, address, pmd, _pmd);
2326 update_mmu_cache_pmd(vma, address, pmd);
2327 spin_unlock(pmd_ptl);
2331 khugepaged_pages_collapsed++;
2332 result = SCAN_SUCCEED;
2334 up_write(&mm->mmap_sem);
2335 trace_mm_collapse_huge_page(mm, isolated, result);
2339 trace_mm_collapse_huge_page(mm, isolated, result);
2342 mem_cgroup_cancel_charge(new_page, memcg, true);
2346 static int khugepaged_scan_pmd(struct mm_struct *mm,
2347 struct vm_area_struct *vma,
2348 unsigned long address,
2349 struct page **hpage)
2353 int ret = 0, none_or_zero = 0, result = 0;
2354 struct page *page = NULL;
2355 unsigned long _address;
2357 int node = NUMA_NO_NODE;
2358 bool writable = false, referenced = false;
2360 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2362 pmd = mm_find_pmd(mm, address);
2364 result = SCAN_PMD_NULL;
2368 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2369 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2370 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2371 _pte++, _address += PAGE_SIZE) {
2372 pte_t pteval = *_pte;
2373 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2374 if (!userfaultfd_armed(vma) &&
2375 ++none_or_zero <= khugepaged_max_ptes_none) {
2378 result = SCAN_EXCEED_NONE_PTE;
2382 if (!pte_present(pteval)) {
2383 result = SCAN_PTE_NON_PRESENT;
2386 if (pte_write(pteval))
2389 page = vm_normal_page(vma, _address, pteval);
2390 if (unlikely(!page)) {
2391 result = SCAN_PAGE_NULL;
2395 /* TODO: teach khugepaged to collapse THP mapped with pte */
2396 if (PageCompound(page)) {
2397 result = SCAN_PAGE_COMPOUND;
2402 * Record which node the original page is from and save this
2403 * information to khugepaged_node_load[].
2404 * Khupaged will allocate hugepage from the node has the max
2407 node = page_to_nid(page);
2408 if (khugepaged_scan_abort(node)) {
2409 result = SCAN_SCAN_ABORT;
2412 khugepaged_node_load[node]++;
2413 if (!PageLRU(page)) {
2414 result = SCAN_SCAN_ABORT;
2417 if (PageLocked(page)) {
2418 result = SCAN_PAGE_LOCK;
2421 if (!PageAnon(page)) {
2422 result = SCAN_PAGE_ANON;
2427 * cannot use mapcount: can't collapse if there's a gup pin.
2428 * The page must only be referenced by the scanned process
2429 * and page swap cache.
2431 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2432 result = SCAN_PAGE_COUNT;
2435 if (pte_young(pteval) ||
2436 page_is_young(page) || PageReferenced(page) ||
2437 mmu_notifier_test_young(vma->vm_mm, address))
2442 result = SCAN_SUCCEED;
2445 result = SCAN_NO_REFERENCED_PAGE;
2448 result = SCAN_PAGE_RO;
2451 pte_unmap_unlock(pte, ptl);
2453 node = khugepaged_find_target_node();
2454 /* collapse_huge_page will return with the mmap_sem released */
2455 collapse_huge_page(mm, address, hpage, vma, node);
2458 trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
2459 none_or_zero, result);
2463 static void collect_mm_slot(struct mm_slot *mm_slot)
2465 struct mm_struct *mm = mm_slot->mm;
2467 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2469 if (khugepaged_test_exit(mm)) {
2471 hash_del(&mm_slot->hash);
2472 list_del(&mm_slot->mm_node);
2475 * Not strictly needed because the mm exited already.
2477 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2480 /* khugepaged_mm_lock actually not necessary for the below */
2481 free_mm_slot(mm_slot);
2486 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2487 struct page **hpage)
2488 __releases(&khugepaged_mm_lock)
2489 __acquires(&khugepaged_mm_lock)
2491 struct mm_slot *mm_slot;
2492 struct mm_struct *mm;
2493 struct vm_area_struct *vma;
2497 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2499 if (khugepaged_scan.mm_slot)
2500 mm_slot = khugepaged_scan.mm_slot;
2502 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2503 struct mm_slot, mm_node);
2504 khugepaged_scan.address = 0;
2505 khugepaged_scan.mm_slot = mm_slot;
2507 spin_unlock(&khugepaged_mm_lock);
2510 down_read(&mm->mmap_sem);
2511 if (unlikely(khugepaged_test_exit(mm)))
2514 vma = find_vma(mm, khugepaged_scan.address);
2517 for (; vma; vma = vma->vm_next) {
2518 unsigned long hstart, hend;
2521 if (unlikely(khugepaged_test_exit(mm))) {
2525 if (!hugepage_vma_check(vma)) {
2530 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2531 hend = vma->vm_end & HPAGE_PMD_MASK;
2534 if (khugepaged_scan.address > hend)
2536 if (khugepaged_scan.address < hstart)
2537 khugepaged_scan.address = hstart;
2538 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2540 while (khugepaged_scan.address < hend) {
2543 if (unlikely(khugepaged_test_exit(mm)))
2544 goto breakouterloop;
2546 VM_BUG_ON(khugepaged_scan.address < hstart ||
2547 khugepaged_scan.address + HPAGE_PMD_SIZE >
2549 ret = khugepaged_scan_pmd(mm, vma,
2550 khugepaged_scan.address,
2552 /* move to next address */
2553 khugepaged_scan.address += HPAGE_PMD_SIZE;
2554 progress += HPAGE_PMD_NR;
2556 /* we released mmap_sem so break loop */
2557 goto breakouterloop_mmap_sem;
2558 if (progress >= pages)
2559 goto breakouterloop;
2563 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2564 breakouterloop_mmap_sem:
2566 spin_lock(&khugepaged_mm_lock);
2567 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2569 * Release the current mm_slot if this mm is about to die, or
2570 * if we scanned all vmas of this mm.
2572 if (khugepaged_test_exit(mm) || !vma) {
2574 * Make sure that if mm_users is reaching zero while
2575 * khugepaged runs here, khugepaged_exit will find
2576 * mm_slot not pointing to the exiting mm.
2578 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2579 khugepaged_scan.mm_slot = list_entry(
2580 mm_slot->mm_node.next,
2581 struct mm_slot, mm_node);
2582 khugepaged_scan.address = 0;
2584 khugepaged_scan.mm_slot = NULL;
2585 khugepaged_full_scans++;
2588 collect_mm_slot(mm_slot);
2594 static int khugepaged_has_work(void)
2596 return !list_empty(&khugepaged_scan.mm_head) &&
2597 khugepaged_enabled();
2600 static int khugepaged_wait_event(void)
2602 return !list_empty(&khugepaged_scan.mm_head) ||
2603 kthread_should_stop();
2606 static void khugepaged_do_scan(void)
2608 struct page *hpage = NULL;
2609 unsigned int progress = 0, pass_through_head = 0;
2610 unsigned int pages = khugepaged_pages_to_scan;
2613 barrier(); /* write khugepaged_pages_to_scan to local stack */
2615 while (progress < pages) {
2616 if (!khugepaged_prealloc_page(&hpage, &wait))
2621 if (unlikely(kthread_should_stop() || try_to_freeze()))
2624 spin_lock(&khugepaged_mm_lock);
2625 if (!khugepaged_scan.mm_slot)
2626 pass_through_head++;
2627 if (khugepaged_has_work() &&
2628 pass_through_head < 2)
2629 progress += khugepaged_scan_mm_slot(pages - progress,
2633 spin_unlock(&khugepaged_mm_lock);
2636 if (!IS_ERR_OR_NULL(hpage))
2640 static void khugepaged_wait_work(void)
2642 if (khugepaged_has_work()) {
2643 if (!khugepaged_scan_sleep_millisecs)
2646 wait_event_freezable_timeout(khugepaged_wait,
2647 kthread_should_stop(),
2648 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2652 if (khugepaged_enabled())
2653 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2656 static int khugepaged(void *none)
2658 struct mm_slot *mm_slot;
2661 set_user_nice(current, MAX_NICE);
2663 while (!kthread_should_stop()) {
2664 khugepaged_do_scan();
2665 khugepaged_wait_work();
2668 spin_lock(&khugepaged_mm_lock);
2669 mm_slot = khugepaged_scan.mm_slot;
2670 khugepaged_scan.mm_slot = NULL;
2672 collect_mm_slot(mm_slot);
2673 spin_unlock(&khugepaged_mm_lock);
2677 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2678 unsigned long haddr, pmd_t *pmd)
2680 struct mm_struct *mm = vma->vm_mm;
2685 /* leave pmd empty until pte is filled */
2686 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2688 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2689 pmd_populate(mm, &_pmd, pgtable);
2691 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2693 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2694 entry = pte_mkspecial(entry);
2695 pte = pte_offset_map(&_pmd, haddr);
2696 VM_BUG_ON(!pte_none(*pte));
2697 set_pte_at(mm, haddr, pte, entry);
2700 smp_wmb(); /* make pte visible before pmd */
2701 pmd_populate(mm, pmd, pgtable);
2702 put_huge_zero_page();
2705 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2706 unsigned long haddr, bool freeze)
2708 struct mm_struct *mm = vma->vm_mm;
2715 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2716 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2717 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2718 VM_BUG_ON(!pmd_trans_huge(*pmd));
2720 count_vm_event(THP_SPLIT_PMD);
2722 if (vma_is_dax(vma)) {
2723 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2724 if (is_huge_zero_pmd(_pmd))
2725 put_huge_zero_page();
2727 } else if (is_huge_zero_pmd(*pmd)) {
2728 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2731 page = pmd_page(*pmd);
2732 VM_BUG_ON_PAGE(!page_count(page), page);
2733 atomic_add(HPAGE_PMD_NR - 1, &page->_count);
2734 write = pmd_write(*pmd);
2735 young = pmd_young(*pmd);
2737 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2738 pmd_populate(mm, &_pmd, pgtable);
2740 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2743 * Note that NUMA hinting access restrictions are not
2744 * transferred to avoid any possibility of altering
2745 * permissions across VMAs.
2748 swp_entry_t swp_entry;
2749 swp_entry = make_migration_entry(page + i, write);
2750 entry = swp_entry_to_pte(swp_entry);
2752 entry = mk_pte(page + i, vma->vm_page_prot);
2753 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2755 entry = pte_wrprotect(entry);
2757 entry = pte_mkold(entry);
2759 pte = pte_offset_map(&_pmd, haddr);
2760 BUG_ON(!pte_none(*pte));
2761 set_pte_at(mm, haddr, pte, entry);
2762 atomic_inc(&page[i]._mapcount);
2767 * Set PG_double_map before dropping compound_mapcount to avoid
2768 * false-negative page_mapped().
2770 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2771 for (i = 0; i < HPAGE_PMD_NR; i++)
2772 atomic_inc(&page[i]._mapcount);
2775 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2776 /* Last compound_mapcount is gone. */
2777 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
2778 if (TestClearPageDoubleMap(page)) {
2779 /* No need in mapcount reference anymore */
2780 for (i = 0; i < HPAGE_PMD_NR; i++)
2781 atomic_dec(&page[i]._mapcount);
2785 smp_wmb(); /* make pte visible before pmd */
2787 * Up to this point the pmd is present and huge and userland has the
2788 * whole access to the hugepage during the split (which happens in
2789 * place). If we overwrite the pmd with the not-huge version pointing
2790 * to the pte here (which of course we could if all CPUs were bug
2791 * free), userland could trigger a small page size TLB miss on the
2792 * small sized TLB while the hugepage TLB entry is still established in
2793 * the huge TLB. Some CPU doesn't like that.
2794 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2795 * 383 on page 93. Intel should be safe but is also warns that it's
2796 * only safe if the permission and cache attributes of the two entries
2797 * loaded in the two TLB is identical (which should be the case here).
2798 * But it is generally safer to never allow small and huge TLB entries
2799 * for the same virtual address to be loaded simultaneously. So instead
2800 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2801 * current pmd notpresent (atomically because here the pmd_trans_huge
2802 * and pmd_trans_splitting must remain set at all times on the pmd
2803 * until the split is complete for this pmd), then we flush the SMP TLB
2804 * and finally we write the non-huge version of the pmd entry with
2807 pmdp_invalidate(vma, haddr, pmd);
2808 pmd_populate(mm, pmd, pgtable);
2811 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2812 page_remove_rmap(page + i, false);
2818 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2819 unsigned long address)
2822 struct mm_struct *mm = vma->vm_mm;
2823 struct page *page = NULL;
2824 unsigned long haddr = address & HPAGE_PMD_MASK;
2826 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2827 ptl = pmd_lock(mm, pmd);
2828 if (unlikely(!pmd_trans_huge(*pmd)))
2830 page = pmd_page(*pmd);
2831 __split_huge_pmd_locked(vma, pmd, haddr, false);
2832 if (PageMlocked(page))
2838 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
2841 munlock_vma_page(page);
2847 static void split_huge_pmd_address(struct vm_area_struct *vma,
2848 unsigned long address)
2854 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2856 pgd = pgd_offset(vma->vm_mm, address);
2857 if (!pgd_present(*pgd))
2860 pud = pud_offset(pgd, address);
2861 if (!pud_present(*pud))
2864 pmd = pmd_offset(pud, address);
2865 if (!pmd_present(*pmd) || !pmd_trans_huge(*pmd))
2868 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2869 * materialize from under us.
2871 split_huge_pmd(vma, pmd, address);
2874 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2875 unsigned long start,
2880 * If the new start address isn't hpage aligned and it could
2881 * previously contain an hugepage: check if we need to split
2884 if (start & ~HPAGE_PMD_MASK &&
2885 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2886 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2887 split_huge_pmd_address(vma, start);
2890 * If the new end address isn't hpage aligned and it could
2891 * previously contain an hugepage: check if we need to split
2894 if (end & ~HPAGE_PMD_MASK &&
2895 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2896 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2897 split_huge_pmd_address(vma, end);
2900 * If we're also updating the vma->vm_next->vm_start, if the new
2901 * vm_next->vm_start isn't page aligned and it could previously
2902 * contain an hugepage: check if we need to split an huge pmd.
2904 if (adjust_next > 0) {
2905 struct vm_area_struct *next = vma->vm_next;
2906 unsigned long nstart = next->vm_start;
2907 nstart += adjust_next << PAGE_SHIFT;
2908 if (nstart & ~HPAGE_PMD_MASK &&
2909 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2910 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2911 split_huge_pmd_address(next, nstart);
2915 static void freeze_page_vma(struct vm_area_struct *vma, struct page *page,
2916 unsigned long address)
2923 int i, nr = HPAGE_PMD_NR;
2925 /* Skip pages which doesn't belong to the VMA */
2926 if (address < vma->vm_start) {
2927 int off = (vma->vm_start - address) >> PAGE_SHIFT;
2930 address = vma->vm_start;
2933 pgd = pgd_offset(vma->vm_mm, address);
2934 if (!pgd_present(*pgd))
2936 pud = pud_offset(pgd, address);
2937 if (!pud_present(*pud))
2939 pmd = pmd_offset(pud, address);
2940 ptl = pmd_lock(vma->vm_mm, pmd);
2941 if (!pmd_present(*pmd)) {
2945 if (pmd_trans_huge(*pmd)) {
2946 if (page == pmd_page(*pmd))
2947 __split_huge_pmd_locked(vma, pmd, address, true);
2953 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
2954 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++) {
2955 pte_t entry, swp_pte;
2956 swp_entry_t swp_entry;
2958 if (!pte_present(pte[i]))
2960 if (page_to_pfn(page) != pte_pfn(pte[i]))
2962 flush_cache_page(vma, address, page_to_pfn(page));
2963 entry = ptep_clear_flush(vma, address, pte + i);
2964 swp_entry = make_migration_entry(page, pte_write(entry));
2965 swp_pte = swp_entry_to_pte(swp_entry);
2966 if (pte_soft_dirty(entry))
2967 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2968 set_pte_at(vma->vm_mm, address, pte + i, swp_pte);
2969 page_remove_rmap(page, false);
2972 pte_unmap_unlock(pte, ptl);
2975 static void freeze_page(struct anon_vma *anon_vma, struct page *page)
2977 struct anon_vma_chain *avc;
2978 pgoff_t pgoff = page_to_pgoff(page);
2980 VM_BUG_ON_PAGE(!PageHead(page), page);
2982 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff,
2983 pgoff + HPAGE_PMD_NR - 1) {
2984 unsigned long haddr;
2986 haddr = __vma_address(page, avc->vma) & HPAGE_PMD_MASK;
2987 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
2988 haddr, haddr + HPAGE_PMD_SIZE);
2989 freeze_page_vma(avc->vma, page, haddr);
2990 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
2991 haddr, haddr + HPAGE_PMD_SIZE);
2995 static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page,
2996 unsigned long address)
3001 swp_entry_t swp_entry;
3002 int i, nr = HPAGE_PMD_NR;
3004 /* Skip pages which doesn't belong to the VMA */
3005 if (address < vma->vm_start) {
3006 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3009 address = vma->vm_start;
3012 pmd = mm_find_pmd(vma->vm_mm, address);
3015 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3016 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++) {
3017 if (!is_swap_pte(pte[i]))
3020 swp_entry = pte_to_swp_entry(pte[i]);
3021 if (!is_migration_entry(swp_entry))
3023 if (migration_entry_to_page(swp_entry) != page)
3027 page_add_anon_rmap(page, vma, address, false);
3029 entry = pte_mkold(mk_pte(page, vma->vm_page_prot));
3030 entry = pte_mkdirty(entry);
3031 if (is_write_migration_entry(swp_entry))
3032 entry = maybe_mkwrite(entry, vma);
3034 flush_dcache_page(page);
3035 set_pte_at(vma->vm_mm, address, pte + i, entry);
3037 /* No need to invalidate - it was non-present before */
3038 update_mmu_cache(vma, address, pte + i);
3040 pte_unmap_unlock(pte, ptl);
3043 static void unfreeze_page(struct anon_vma *anon_vma, struct page *page)
3045 struct anon_vma_chain *avc;
3046 pgoff_t pgoff = page_to_pgoff(page);
3048 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
3049 pgoff, pgoff + HPAGE_PMD_NR - 1) {
3050 unsigned long address = __vma_address(page, avc->vma);
3052 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3053 address, address + HPAGE_PMD_SIZE);
3054 unfreeze_page_vma(avc->vma, page, address);
3055 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3056 address, address + HPAGE_PMD_SIZE);
3060 static int __split_huge_page_tail(struct page *head, int tail,
3061 struct lruvec *lruvec, struct list_head *list)
3064 struct page *page_tail = head + tail;
3066 mapcount = atomic_read(&page_tail->_mapcount) + 1;
3067 VM_BUG_ON_PAGE(atomic_read(&page_tail->_count) != 0, page_tail);
3070 * tail_page->_count is zero and not changing from under us. But
3071 * get_page_unless_zero() may be running from under us on the
3072 * tail_page. If we used atomic_set() below instead of atomic_add(), we
3073 * would then run atomic_set() concurrently with
3074 * get_page_unless_zero(), and atomic_set() is implemented in C not
3075 * using locked ops. spin_unlock on x86 sometime uses locked ops
3076 * because of PPro errata 66, 92, so unless somebody can guarantee
3077 * atomic_set() here would be safe on all archs (and not only on x86),
3078 * it's safer to use atomic_add().
3080 atomic_add(mapcount + 1, &page_tail->_count);
3083 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3084 page_tail->flags |= (head->flags &
3085 ((1L << PG_referenced) |
3086 (1L << PG_swapbacked) |
3087 (1L << PG_mlocked) |
3088 (1L << PG_uptodate) |
3091 (1L << PG_unevictable)));
3092 page_tail->flags |= (1L << PG_dirty);
3095 * After clearing PageTail the gup refcount can be released.
3096 * Page flags also must be visible before we make the page non-compound.
3100 clear_compound_head(page_tail);
3102 if (page_is_young(head))
3103 set_page_young(page_tail);
3104 if (page_is_idle(head))
3105 set_page_idle(page_tail);
3107 /* ->mapping in first tail page is compound_mapcount */
3108 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3110 page_tail->mapping = head->mapping;
3112 page_tail->index = head->index + tail;
3113 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3114 lru_add_page_tail(head, page_tail, lruvec, list);
3119 static void __split_huge_page(struct page *page, struct list_head *list)
3121 struct page *head = compound_head(page);
3122 struct zone *zone = page_zone(head);
3123 struct lruvec *lruvec;
3124 int i, tail_mapcount;
3126 /* prevent PageLRU to go away from under us, and freeze lru stats */
3127 spin_lock_irq(&zone->lru_lock);
3128 lruvec = mem_cgroup_page_lruvec(head, zone);
3130 /* complete memcg works before add pages to LRU */
3131 mem_cgroup_split_huge_fixup(head);
3134 for (i = HPAGE_PMD_NR - 1; i >= 1; i--)
3135 tail_mapcount += __split_huge_page_tail(head, i, lruvec, list);
3136 atomic_sub(tail_mapcount, &head->_count);
3138 ClearPageCompound(head);
3139 spin_unlock_irq(&zone->lru_lock);
3141 unfreeze_page(page_anon_vma(head), head);
3143 for (i = 0; i < HPAGE_PMD_NR; i++) {
3144 struct page *subpage = head + i;
3145 if (subpage == page)
3147 unlock_page(subpage);
3150 * Subpages may be freed if there wasn't any mapping
3151 * like if add_to_swap() is running on a lru page that
3152 * had its mapping zapped. And freeing these pages
3153 * requires taking the lru_lock so we do the put_page
3154 * of the tail pages after the split is complete.
3160 int total_mapcount(struct page *page)
3164 VM_BUG_ON_PAGE(PageTail(page), page);
3166 if (likely(!PageCompound(page)))
3167 return atomic_read(&page->_mapcount) + 1;
3169 ret = compound_mapcount(page);
3172 for (i = 0; i < HPAGE_PMD_NR; i++)
3173 ret += atomic_read(&page[i]._mapcount) + 1;
3174 if (PageDoubleMap(page))
3175 ret -= HPAGE_PMD_NR;
3180 * This function splits huge page into normal pages. @page can point to any
3181 * subpage of huge page to split. Split doesn't change the position of @page.
3183 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3184 * The huge page must be locked.
3186 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3188 * Both head page and tail pages will inherit mapping, flags, and so on from
3191 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3192 * they are not mapped.
3194 * Returns 0 if the hugepage is split successfully.
3195 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3198 int split_huge_page_to_list(struct page *page, struct list_head *list)
3200 struct page *head = compound_head(page);
3201 struct anon_vma *anon_vma;
3202 int count, mapcount, ret;
3204 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3205 VM_BUG_ON_PAGE(!PageAnon(page), page);
3206 VM_BUG_ON_PAGE(!PageLocked(page), page);
3207 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3208 VM_BUG_ON_PAGE(!PageCompound(page), page);
3211 * The caller does not necessarily hold an mmap_sem that would prevent
3212 * the anon_vma disappearing so we first we take a reference to it
3213 * and then lock the anon_vma for write. This is similar to
3214 * page_lock_anon_vma_read except the write lock is taken to serialise
3215 * against parallel split or collapse operations.
3217 anon_vma = page_get_anon_vma(head);
3222 anon_vma_lock_write(anon_vma);
3225 * Racy check if we can split the page, before freeze_page() will
3228 if (total_mapcount(head) != page_count(head) - 1) {
3233 freeze_page(anon_vma, head);
3234 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3236 /* Prevent deferred_split_scan() touching ->_count */
3237 spin_lock(&split_queue_lock);
3238 count = page_count(head);
3239 mapcount = total_mapcount(head);
3240 if (mapcount == count - 1) {
3241 if (!list_empty(page_deferred_list(head))) {
3243 list_del(page_deferred_list(head));
3245 spin_unlock(&split_queue_lock);
3246 __split_huge_page(page, list);
3248 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount > count - 1) {
3249 spin_unlock(&split_queue_lock);
3250 pr_alert("total_mapcount: %u, page_count(): %u\n",
3253 dump_page(head, NULL);
3254 dump_page(page, "total_mapcount(head) > page_count(head) - 1");
3257 spin_unlock(&split_queue_lock);
3258 unfreeze_page(anon_vma, head);
3263 anon_vma_unlock_write(anon_vma);
3264 put_anon_vma(anon_vma);
3266 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3270 void free_transhuge_page(struct page *page)
3272 unsigned long flags;
3274 spin_lock_irqsave(&split_queue_lock, flags);
3275 if (!list_empty(page_deferred_list(page))) {
3277 list_del(page_deferred_list(page));
3279 spin_unlock_irqrestore(&split_queue_lock, flags);
3280 free_compound_page(page);
3283 void deferred_split_huge_page(struct page *page)
3285 unsigned long flags;
3287 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3289 spin_lock_irqsave(&split_queue_lock, flags);
3290 if (list_empty(page_deferred_list(page))) {
3291 list_add_tail(page_deferred_list(page), &split_queue);
3294 spin_unlock_irqrestore(&split_queue_lock, flags);
3297 static unsigned long deferred_split_count(struct shrinker *shrink,
3298 struct shrink_control *sc)
3301 * Split a page from split_queue will free up at least one page,
3302 * at most HPAGE_PMD_NR - 1. We don't track exact number.
3303 * Let's use HPAGE_PMD_NR / 2 as ballpark.
3305 return ACCESS_ONCE(split_queue_len) * HPAGE_PMD_NR / 2;
3308 static unsigned long deferred_split_scan(struct shrinker *shrink,
3309 struct shrink_control *sc)
3311 unsigned long flags;
3312 LIST_HEAD(list), *pos, *next;
3316 spin_lock_irqsave(&split_queue_lock, flags);
3317 list_splice_init(&split_queue, &list);
3319 /* Take pin on all head pages to avoid freeing them under us */
3320 list_for_each_safe(pos, next, &list) {
3321 page = list_entry((void *)pos, struct page, mapping);
3322 page = compound_head(page);
3323 /* race with put_compound_page() */
3324 if (!get_page_unless_zero(page)) {
3325 list_del_init(page_deferred_list(page));
3329 spin_unlock_irqrestore(&split_queue_lock, flags);
3331 list_for_each_safe(pos, next, &list) {
3332 page = list_entry((void *)pos, struct page, mapping);
3334 /* split_huge_page() removes page from list on success */
3335 if (!split_huge_page(page))
3341 spin_lock_irqsave(&split_queue_lock, flags);
3342 list_splice_tail(&list, &split_queue);
3343 spin_unlock_irqrestore(&split_queue_lock, flags);
3345 return split * HPAGE_PMD_NR / 2;
3348 static struct shrinker deferred_split_shrinker = {
3349 .count_objects = deferred_split_count,
3350 .scan_objects = deferred_split_scan,
3351 .seeks = DEFAULT_SEEKS,