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/debugfs.h>
27 #include <linux/migrate.h>
28 #include <linux/hashtable.h>
29 #include <linux/userfaultfd_k.h>
30 #include <linux/page_idle.h>
33 #include <asm/pgalloc.h>
43 SCAN_NO_REFERENCED_PAGE,
57 SCAN_ALLOC_HUGE_PAGE_FAIL,
58 SCAN_CGROUP_CHARGE_FAIL
61 #define CREATE_TRACE_POINTS
62 #include <trace/events/huge_memory.h>
65 * By default transparent hugepage support is disabled in order that avoid
66 * to risk increase the memory footprint of applications without a guaranteed
67 * benefit. When transparent hugepage support is enabled, is for all mappings,
68 * and khugepaged scans all mappings.
69 * Defrag is invoked by khugepaged hugepage allocations and by page faults
70 * for all hugepage allocations.
72 unsigned long transparent_hugepage_flags __read_mostly =
73 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
74 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
76 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
77 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
79 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
80 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
81 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
83 /* default scan 8*512 pte (or vmas) every 30 second */
84 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
85 static unsigned int khugepaged_pages_collapsed;
86 static unsigned int khugepaged_full_scans;
87 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
88 /* during fragmentation poll the hugepage allocator once every minute */
89 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
90 static struct task_struct *khugepaged_thread __read_mostly;
91 static DEFINE_MUTEX(khugepaged_mutex);
92 static DEFINE_SPINLOCK(khugepaged_mm_lock);
93 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
95 * default collapse hugepages if there is at least one pte mapped like
96 * it would have happened if the vma was large enough during page
99 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
101 static int khugepaged(void *none);
102 static int khugepaged_slab_init(void);
103 static void khugepaged_slab_exit(void);
105 #define MM_SLOTS_HASH_BITS 10
106 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
108 static struct kmem_cache *mm_slot_cache __read_mostly;
111 * struct mm_slot - hash lookup from mm to mm_slot
112 * @hash: hash collision list
113 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
114 * @mm: the mm that this information is valid for
117 struct hlist_node hash;
118 struct list_head mm_node;
119 struct mm_struct *mm;
123 * struct khugepaged_scan - cursor for scanning
124 * @mm_head: the head of the mm list to scan
125 * @mm_slot: the current mm_slot we are scanning
126 * @address: the next address inside that to be scanned
128 * There is only the one khugepaged_scan instance of this cursor structure.
130 struct khugepaged_scan {
131 struct list_head mm_head;
132 struct mm_slot *mm_slot;
133 unsigned long address;
135 static struct khugepaged_scan khugepaged_scan = {
136 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
139 static DEFINE_SPINLOCK(split_queue_lock);
140 static LIST_HEAD(split_queue);
141 static unsigned long split_queue_len;
142 static struct shrinker deferred_split_shrinker;
144 static void set_recommended_min_free_kbytes(void)
148 unsigned long recommended_min;
150 for_each_populated_zone(zone)
153 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
154 recommended_min = pageblock_nr_pages * nr_zones * 2;
157 * Make sure that on average at least two pageblocks are almost free
158 * of another type, one for a migratetype to fall back to and a
159 * second to avoid subsequent fallbacks of other types There are 3
160 * MIGRATE_TYPES we care about.
162 recommended_min += pageblock_nr_pages * nr_zones *
163 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
165 /* don't ever allow to reserve more than 5% of the lowmem */
166 recommended_min = min(recommended_min,
167 (unsigned long) nr_free_buffer_pages() / 20);
168 recommended_min <<= (PAGE_SHIFT-10);
170 if (recommended_min > min_free_kbytes) {
171 if (user_min_free_kbytes >= 0)
172 pr_info("raising min_free_kbytes from %d to %lu "
173 "to help transparent hugepage allocations\n",
174 min_free_kbytes, recommended_min);
176 min_free_kbytes = recommended_min;
178 setup_per_zone_wmarks();
181 static int start_stop_khugepaged(void)
184 if (khugepaged_enabled()) {
185 if (!khugepaged_thread)
186 khugepaged_thread = kthread_run(khugepaged, NULL,
188 if (IS_ERR(khugepaged_thread)) {
189 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
190 err = PTR_ERR(khugepaged_thread);
191 khugepaged_thread = NULL;
195 if (!list_empty(&khugepaged_scan.mm_head))
196 wake_up_interruptible(&khugepaged_wait);
198 set_recommended_min_free_kbytes();
199 } else if (khugepaged_thread) {
200 kthread_stop(khugepaged_thread);
201 khugepaged_thread = NULL;
207 static atomic_t huge_zero_refcount;
208 struct page *huge_zero_page __read_mostly;
210 struct page *get_huge_zero_page(void)
212 struct page *zero_page;
214 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
215 return READ_ONCE(huge_zero_page);
217 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
220 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
223 count_vm_event(THP_ZERO_PAGE_ALLOC);
225 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
227 __free_pages(zero_page, compound_order(zero_page));
231 /* We take additional reference here. It will be put back by shrinker */
232 atomic_set(&huge_zero_refcount, 2);
234 return READ_ONCE(huge_zero_page);
237 static void put_huge_zero_page(void)
240 * Counter should never go to zero here. Only shrinker can put
243 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
246 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
247 struct shrink_control *sc)
249 /* we can free zero page only if last reference remains */
250 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
253 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
254 struct shrink_control *sc)
256 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
257 struct page *zero_page = xchg(&huge_zero_page, NULL);
258 BUG_ON(zero_page == NULL);
259 __free_pages(zero_page, compound_order(zero_page));
266 static struct shrinker huge_zero_page_shrinker = {
267 .count_objects = shrink_huge_zero_page_count,
268 .scan_objects = shrink_huge_zero_page_scan,
269 .seeks = DEFAULT_SEEKS,
274 static ssize_t double_flag_show(struct kobject *kobj,
275 struct kobj_attribute *attr, char *buf,
276 enum transparent_hugepage_flag enabled,
277 enum transparent_hugepage_flag req_madv)
279 if (test_bit(enabled, &transparent_hugepage_flags)) {
280 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
281 return sprintf(buf, "[always] madvise never\n");
282 } else if (test_bit(req_madv, &transparent_hugepage_flags))
283 return sprintf(buf, "always [madvise] never\n");
285 return sprintf(buf, "always madvise [never]\n");
287 static ssize_t double_flag_store(struct kobject *kobj,
288 struct kobj_attribute *attr,
289 const char *buf, size_t count,
290 enum transparent_hugepage_flag enabled,
291 enum transparent_hugepage_flag req_madv)
293 if (!memcmp("always", buf,
294 min(sizeof("always")-1, count))) {
295 set_bit(enabled, &transparent_hugepage_flags);
296 clear_bit(req_madv, &transparent_hugepage_flags);
297 } else if (!memcmp("madvise", buf,
298 min(sizeof("madvise")-1, count))) {
299 clear_bit(enabled, &transparent_hugepage_flags);
300 set_bit(req_madv, &transparent_hugepage_flags);
301 } else if (!memcmp("never", buf,
302 min(sizeof("never")-1, count))) {
303 clear_bit(enabled, &transparent_hugepage_flags);
304 clear_bit(req_madv, &transparent_hugepage_flags);
311 static ssize_t enabled_show(struct kobject *kobj,
312 struct kobj_attribute *attr, char *buf)
314 return double_flag_show(kobj, attr, buf,
315 TRANSPARENT_HUGEPAGE_FLAG,
316 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
318 static ssize_t enabled_store(struct kobject *kobj,
319 struct kobj_attribute *attr,
320 const char *buf, size_t count)
324 ret = double_flag_store(kobj, attr, buf, count,
325 TRANSPARENT_HUGEPAGE_FLAG,
326 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
331 mutex_lock(&khugepaged_mutex);
332 err = start_stop_khugepaged();
333 mutex_unlock(&khugepaged_mutex);
341 static struct kobj_attribute enabled_attr =
342 __ATTR(enabled, 0644, enabled_show, enabled_store);
344 static ssize_t single_flag_show(struct kobject *kobj,
345 struct kobj_attribute *attr, char *buf,
346 enum transparent_hugepage_flag flag)
348 return sprintf(buf, "%d\n",
349 !!test_bit(flag, &transparent_hugepage_flags));
352 static ssize_t single_flag_store(struct kobject *kobj,
353 struct kobj_attribute *attr,
354 const char *buf, size_t count,
355 enum transparent_hugepage_flag flag)
360 ret = kstrtoul(buf, 10, &value);
367 set_bit(flag, &transparent_hugepage_flags);
369 clear_bit(flag, &transparent_hugepage_flags);
375 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
376 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
377 * memory just to allocate one more hugepage.
379 static ssize_t defrag_show(struct kobject *kobj,
380 struct kobj_attribute *attr, char *buf)
382 return double_flag_show(kobj, attr, buf,
383 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
384 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
386 static ssize_t defrag_store(struct kobject *kobj,
387 struct kobj_attribute *attr,
388 const char *buf, size_t count)
390 return double_flag_store(kobj, attr, buf, count,
391 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
392 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
394 static struct kobj_attribute defrag_attr =
395 __ATTR(defrag, 0644, defrag_show, defrag_store);
397 static ssize_t use_zero_page_show(struct kobject *kobj,
398 struct kobj_attribute *attr, char *buf)
400 return single_flag_show(kobj, attr, buf,
401 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
403 static ssize_t use_zero_page_store(struct kobject *kobj,
404 struct kobj_attribute *attr, const char *buf, size_t count)
406 return single_flag_store(kobj, attr, buf, count,
407 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
409 static struct kobj_attribute use_zero_page_attr =
410 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
411 #ifdef CONFIG_DEBUG_VM
412 static ssize_t debug_cow_show(struct kobject *kobj,
413 struct kobj_attribute *attr, char *buf)
415 return single_flag_show(kobj, attr, buf,
416 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
418 static ssize_t debug_cow_store(struct kobject *kobj,
419 struct kobj_attribute *attr,
420 const char *buf, size_t count)
422 return single_flag_store(kobj, attr, buf, count,
423 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
425 static struct kobj_attribute debug_cow_attr =
426 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
427 #endif /* CONFIG_DEBUG_VM */
429 static struct attribute *hugepage_attr[] = {
432 &use_zero_page_attr.attr,
433 #ifdef CONFIG_DEBUG_VM
434 &debug_cow_attr.attr,
439 static struct attribute_group hugepage_attr_group = {
440 .attrs = hugepage_attr,
443 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
444 struct kobj_attribute *attr,
447 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
450 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
451 struct kobj_attribute *attr,
452 const char *buf, size_t count)
457 err = kstrtoul(buf, 10, &msecs);
458 if (err || msecs > UINT_MAX)
461 khugepaged_scan_sleep_millisecs = msecs;
462 wake_up_interruptible(&khugepaged_wait);
466 static struct kobj_attribute scan_sleep_millisecs_attr =
467 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
468 scan_sleep_millisecs_store);
470 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
471 struct kobj_attribute *attr,
474 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
477 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
478 struct kobj_attribute *attr,
479 const char *buf, size_t count)
484 err = kstrtoul(buf, 10, &msecs);
485 if (err || msecs > UINT_MAX)
488 khugepaged_alloc_sleep_millisecs = msecs;
489 wake_up_interruptible(&khugepaged_wait);
493 static struct kobj_attribute alloc_sleep_millisecs_attr =
494 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
495 alloc_sleep_millisecs_store);
497 static ssize_t pages_to_scan_show(struct kobject *kobj,
498 struct kobj_attribute *attr,
501 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
503 static ssize_t pages_to_scan_store(struct kobject *kobj,
504 struct kobj_attribute *attr,
505 const char *buf, size_t count)
510 err = kstrtoul(buf, 10, &pages);
511 if (err || !pages || pages > UINT_MAX)
514 khugepaged_pages_to_scan = pages;
518 static struct kobj_attribute pages_to_scan_attr =
519 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
520 pages_to_scan_store);
522 static ssize_t pages_collapsed_show(struct kobject *kobj,
523 struct kobj_attribute *attr,
526 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
528 static struct kobj_attribute pages_collapsed_attr =
529 __ATTR_RO(pages_collapsed);
531 static ssize_t full_scans_show(struct kobject *kobj,
532 struct kobj_attribute *attr,
535 return sprintf(buf, "%u\n", khugepaged_full_scans);
537 static struct kobj_attribute full_scans_attr =
538 __ATTR_RO(full_scans);
540 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
541 struct kobj_attribute *attr, char *buf)
543 return single_flag_show(kobj, attr, buf,
544 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
546 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
547 struct kobj_attribute *attr,
548 const char *buf, size_t count)
550 return single_flag_store(kobj, attr, buf, count,
551 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
553 static struct kobj_attribute khugepaged_defrag_attr =
554 __ATTR(defrag, 0644, khugepaged_defrag_show,
555 khugepaged_defrag_store);
558 * max_ptes_none controls if khugepaged should collapse hugepages over
559 * any unmapped ptes in turn potentially increasing the memory
560 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
561 * reduce the available free memory in the system as it
562 * runs. Increasing max_ptes_none will instead potentially reduce the
563 * free memory in the system during the khugepaged scan.
565 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
566 struct kobj_attribute *attr,
569 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
571 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
572 struct kobj_attribute *attr,
573 const char *buf, size_t count)
576 unsigned long max_ptes_none;
578 err = kstrtoul(buf, 10, &max_ptes_none);
579 if (err || max_ptes_none > HPAGE_PMD_NR-1)
582 khugepaged_max_ptes_none = max_ptes_none;
586 static struct kobj_attribute khugepaged_max_ptes_none_attr =
587 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
588 khugepaged_max_ptes_none_store);
590 static struct attribute *khugepaged_attr[] = {
591 &khugepaged_defrag_attr.attr,
592 &khugepaged_max_ptes_none_attr.attr,
593 &pages_to_scan_attr.attr,
594 &pages_collapsed_attr.attr,
595 &full_scans_attr.attr,
596 &scan_sleep_millisecs_attr.attr,
597 &alloc_sleep_millisecs_attr.attr,
601 static struct attribute_group khugepaged_attr_group = {
602 .attrs = khugepaged_attr,
603 .name = "khugepaged",
606 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
610 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
611 if (unlikely(!*hugepage_kobj)) {
612 pr_err("failed to create transparent hugepage kobject\n");
616 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
618 pr_err("failed to register transparent hugepage group\n");
622 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
624 pr_err("failed to register transparent hugepage group\n");
625 goto remove_hp_group;
631 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
633 kobject_put(*hugepage_kobj);
637 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
639 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
640 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
641 kobject_put(hugepage_kobj);
644 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
649 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
652 #endif /* CONFIG_SYSFS */
654 static int __init hugepage_init(void)
657 struct kobject *hugepage_kobj;
659 if (!has_transparent_hugepage()) {
660 transparent_hugepage_flags = 0;
664 err = hugepage_init_sysfs(&hugepage_kobj);
668 err = khugepaged_slab_init();
672 err = register_shrinker(&huge_zero_page_shrinker);
674 goto err_hzp_shrinker;
675 err = register_shrinker(&deferred_split_shrinker);
677 goto err_split_shrinker;
680 * By default disable transparent hugepages on smaller systems,
681 * where the extra memory used could hurt more than TLB overhead
682 * is likely to save. The admin can still enable it through /sys.
684 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
685 transparent_hugepage_flags = 0;
689 err = start_stop_khugepaged();
695 unregister_shrinker(&deferred_split_shrinker);
697 unregister_shrinker(&huge_zero_page_shrinker);
699 khugepaged_slab_exit();
701 hugepage_exit_sysfs(hugepage_kobj);
705 subsys_initcall(hugepage_init);
707 static int __init setup_transparent_hugepage(char *str)
712 if (!strcmp(str, "always")) {
713 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
714 &transparent_hugepage_flags);
715 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
716 &transparent_hugepage_flags);
718 } else if (!strcmp(str, "madvise")) {
719 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
720 &transparent_hugepage_flags);
721 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
722 &transparent_hugepage_flags);
724 } else if (!strcmp(str, "never")) {
725 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
726 &transparent_hugepage_flags);
727 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
728 &transparent_hugepage_flags);
733 pr_warn("transparent_hugepage= cannot parse, ignored\n");
736 __setup("transparent_hugepage=", setup_transparent_hugepage);
738 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
740 if (likely(vma->vm_flags & VM_WRITE))
741 pmd = pmd_mkwrite(pmd);
745 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
748 entry = mk_pmd(page, prot);
749 entry = pmd_mkhuge(entry);
753 static inline struct list_head *page_deferred_list(struct page *page)
756 * ->lru in the tail pages is occupied by compound_head.
757 * Let's use ->mapping + ->index in the second tail page as list_head.
759 return (struct list_head *)&page[2].mapping;
762 void prep_transhuge_page(struct page *page)
765 * we use page->mapping and page->indexlru in second tail page
766 * as list_head: assuming THP order >= 2
768 BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
770 INIT_LIST_HEAD(page_deferred_list(page));
771 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
774 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
775 struct vm_area_struct *vma,
776 unsigned long address, pmd_t *pmd,
777 struct page *page, gfp_t gfp,
780 struct mem_cgroup *memcg;
783 unsigned long haddr = address & HPAGE_PMD_MASK;
785 VM_BUG_ON_PAGE(!PageCompound(page), page);
787 if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) {
789 count_vm_event(THP_FAULT_FALLBACK);
790 return VM_FAULT_FALLBACK;
793 pgtable = pte_alloc_one(mm, haddr);
794 if (unlikely(!pgtable)) {
795 mem_cgroup_cancel_charge(page, memcg, true);
800 clear_huge_page(page, haddr, HPAGE_PMD_NR);
802 * The memory barrier inside __SetPageUptodate makes sure that
803 * clear_huge_page writes become visible before the set_pmd_at()
806 __SetPageUptodate(page);
808 ptl = pmd_lock(mm, pmd);
809 if (unlikely(!pmd_none(*pmd))) {
811 mem_cgroup_cancel_charge(page, memcg, true);
813 pte_free(mm, pgtable);
817 /* Deliver the page fault to userland */
818 if (userfaultfd_missing(vma)) {
822 mem_cgroup_cancel_charge(page, memcg, true);
824 pte_free(mm, pgtable);
825 ret = handle_userfault(vma, address, flags,
827 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
831 entry = mk_huge_pmd(page, vma->vm_page_prot);
832 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
833 page_add_new_anon_rmap(page, vma, haddr, true);
834 mem_cgroup_commit_charge(page, memcg, false, true);
835 lru_cache_add_active_or_unevictable(page, vma);
836 pgtable_trans_huge_deposit(mm, pmd, pgtable);
837 set_pmd_at(mm, haddr, pmd, entry);
838 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
839 atomic_long_inc(&mm->nr_ptes);
841 count_vm_event(THP_FAULT_ALLOC);
847 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
849 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_RECLAIM)) | extra_gfp;
852 /* Caller must hold page table lock. */
853 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
854 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
855 struct page *zero_page)
860 entry = mk_pmd(zero_page, vma->vm_page_prot);
861 entry = pmd_mkhuge(entry);
862 pgtable_trans_huge_deposit(mm, pmd, pgtable);
863 set_pmd_at(mm, haddr, pmd, entry);
864 atomic_long_inc(&mm->nr_ptes);
868 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
869 unsigned long address, pmd_t *pmd,
874 unsigned long haddr = address & HPAGE_PMD_MASK;
876 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
877 return VM_FAULT_FALLBACK;
878 if (unlikely(anon_vma_prepare(vma)))
880 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
882 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
883 transparent_hugepage_use_zero_page()) {
886 struct page *zero_page;
889 pgtable = pte_alloc_one(mm, haddr);
890 if (unlikely(!pgtable))
892 zero_page = get_huge_zero_page();
893 if (unlikely(!zero_page)) {
894 pte_free(mm, pgtable);
895 count_vm_event(THP_FAULT_FALLBACK);
896 return VM_FAULT_FALLBACK;
898 ptl = pmd_lock(mm, pmd);
901 if (pmd_none(*pmd)) {
902 if (userfaultfd_missing(vma)) {
904 ret = handle_userfault(vma, address, flags,
906 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
908 set_huge_zero_page(pgtable, mm, vma,
917 pte_free(mm, pgtable);
918 put_huge_zero_page();
922 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
923 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
924 if (unlikely(!page)) {
925 count_vm_event(THP_FAULT_FALLBACK);
926 return VM_FAULT_FALLBACK;
928 prep_transhuge_page(page);
929 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
933 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
934 pmd_t *pmd, unsigned long pfn, pgprot_t prot, bool write)
936 struct mm_struct *mm = vma->vm_mm;
940 ptl = pmd_lock(mm, pmd);
941 if (pmd_none(*pmd)) {
942 entry = pmd_mkhuge(pfn_pmd(pfn, prot));
944 entry = pmd_mkyoung(pmd_mkdirty(entry));
945 entry = maybe_pmd_mkwrite(entry, vma);
947 set_pmd_at(mm, addr, pmd, entry);
948 update_mmu_cache_pmd(vma, addr, pmd);
953 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
954 pmd_t *pmd, unsigned long pfn, bool write)
956 pgprot_t pgprot = vma->vm_page_prot;
958 * If we had pmd_special, we could avoid all these restrictions,
959 * but we need to be consistent with PTEs and architectures that
960 * can't support a 'special' bit.
962 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
963 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
964 (VM_PFNMAP|VM_MIXEDMAP));
965 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
966 BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
968 if (addr < vma->vm_start || addr >= vma->vm_end)
969 return VM_FAULT_SIGBUS;
970 if (track_pfn_insert(vma, &pgprot, pfn))
971 return VM_FAULT_SIGBUS;
972 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
973 return VM_FAULT_NOPAGE;
976 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
977 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
978 struct vm_area_struct *vma)
980 spinlock_t *dst_ptl, *src_ptl;
981 struct page *src_page;
987 pgtable = pte_alloc_one(dst_mm, addr);
988 if (unlikely(!pgtable))
991 dst_ptl = pmd_lock(dst_mm, dst_pmd);
992 src_ptl = pmd_lockptr(src_mm, src_pmd);
993 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
997 if (unlikely(!pmd_trans_huge(pmd))) {
998 pte_free(dst_mm, pgtable);
1002 * When page table lock is held, the huge zero pmd should not be
1003 * under splitting since we don't split the page itself, only pmd to
1006 if (is_huge_zero_pmd(pmd)) {
1007 struct page *zero_page;
1009 * get_huge_zero_page() will never allocate a new page here,
1010 * since we already have a zero page to copy. It just takes a
1013 zero_page = get_huge_zero_page();
1014 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1020 src_page = pmd_page(pmd);
1021 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1023 page_dup_rmap(src_page, true);
1024 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1026 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1027 pmd = pmd_mkold(pmd_wrprotect(pmd));
1028 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1029 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1030 atomic_long_inc(&dst_mm->nr_ptes);
1034 spin_unlock(src_ptl);
1035 spin_unlock(dst_ptl);
1040 void huge_pmd_set_accessed(struct mm_struct *mm,
1041 struct vm_area_struct *vma,
1042 unsigned long address,
1043 pmd_t *pmd, pmd_t orig_pmd,
1048 unsigned long haddr;
1050 ptl = pmd_lock(mm, pmd);
1051 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1054 entry = pmd_mkyoung(orig_pmd);
1055 haddr = address & HPAGE_PMD_MASK;
1056 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1057 update_mmu_cache_pmd(vma, address, pmd);
1063 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1064 struct vm_area_struct *vma,
1065 unsigned long address,
1066 pmd_t *pmd, pmd_t orig_pmd,
1068 unsigned long haddr)
1070 struct mem_cgroup *memcg;
1075 struct page **pages;
1076 unsigned long mmun_start; /* For mmu_notifiers */
1077 unsigned long mmun_end; /* For mmu_notifiers */
1079 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1081 if (unlikely(!pages)) {
1082 ret |= VM_FAULT_OOM;
1086 for (i = 0; i < HPAGE_PMD_NR; i++) {
1087 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1089 vma, address, page_to_nid(page));
1090 if (unlikely(!pages[i] ||
1091 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1096 memcg = (void *)page_private(pages[i]);
1097 set_page_private(pages[i], 0);
1098 mem_cgroup_cancel_charge(pages[i], memcg,
1103 ret |= VM_FAULT_OOM;
1106 set_page_private(pages[i], (unsigned long)memcg);
1109 for (i = 0; i < HPAGE_PMD_NR; i++) {
1110 copy_user_highpage(pages[i], page + i,
1111 haddr + PAGE_SIZE * i, vma);
1112 __SetPageUptodate(pages[i]);
1117 mmun_end = haddr + HPAGE_PMD_SIZE;
1118 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1120 ptl = pmd_lock(mm, pmd);
1121 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1122 goto out_free_pages;
1123 VM_BUG_ON_PAGE(!PageHead(page), page);
1125 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1126 /* leave pmd empty until pte is filled */
1128 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1129 pmd_populate(mm, &_pmd, pgtable);
1131 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1133 entry = mk_pte(pages[i], vma->vm_page_prot);
1134 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1135 memcg = (void *)page_private(pages[i]);
1136 set_page_private(pages[i], 0);
1137 page_add_new_anon_rmap(pages[i], vma, haddr, false);
1138 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1139 lru_cache_add_active_or_unevictable(pages[i], vma);
1140 pte = pte_offset_map(&_pmd, haddr);
1141 VM_BUG_ON(!pte_none(*pte));
1142 set_pte_at(mm, haddr, pte, entry);
1147 smp_wmb(); /* make pte visible before pmd */
1148 pmd_populate(mm, pmd, pgtable);
1149 page_remove_rmap(page, true);
1152 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1154 ret |= VM_FAULT_WRITE;
1162 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1163 for (i = 0; i < HPAGE_PMD_NR; i++) {
1164 memcg = (void *)page_private(pages[i]);
1165 set_page_private(pages[i], 0);
1166 mem_cgroup_cancel_charge(pages[i], memcg, false);
1173 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1174 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1178 struct page *page = NULL, *new_page;
1179 struct mem_cgroup *memcg;
1180 unsigned long haddr;
1181 unsigned long mmun_start; /* For mmu_notifiers */
1182 unsigned long mmun_end; /* For mmu_notifiers */
1183 gfp_t huge_gfp; /* for allocation and charge */
1185 ptl = pmd_lockptr(mm, pmd);
1186 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1187 haddr = address & HPAGE_PMD_MASK;
1188 if (is_huge_zero_pmd(orig_pmd))
1191 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1194 page = pmd_page(orig_pmd);
1195 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1197 * We can only reuse the page if nobody else maps the huge page or it's
1198 * part. We can do it by checking page_mapcount() on each sub-page, but
1200 * The cheaper way is to check page_count() to be equal 1: every
1201 * mapcount takes page reference reference, so this way we can
1202 * guarantee, that the PMD is the only mapping.
1203 * This can give false negative if somebody pinned the page, but that's
1206 if (page_mapcount(page) == 1 && page_count(page) == 1) {
1208 entry = pmd_mkyoung(orig_pmd);
1209 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1210 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1211 update_mmu_cache_pmd(vma, address, pmd);
1212 ret |= VM_FAULT_WRITE;
1218 if (transparent_hugepage_enabled(vma) &&
1219 !transparent_hugepage_debug_cow()) {
1220 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1221 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1225 if (likely(new_page)) {
1226 prep_transhuge_page(new_page);
1229 split_huge_pmd(vma, pmd, address);
1230 ret |= VM_FAULT_FALLBACK;
1232 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1233 pmd, orig_pmd, page, haddr);
1234 if (ret & VM_FAULT_OOM) {
1235 split_huge_pmd(vma, pmd, address);
1236 ret |= VM_FAULT_FALLBACK;
1240 count_vm_event(THP_FAULT_FALLBACK);
1244 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg,
1248 split_huge_pmd(vma, pmd, address);
1251 split_huge_pmd(vma, pmd, address);
1252 ret |= VM_FAULT_FALLBACK;
1253 count_vm_event(THP_FAULT_FALLBACK);
1257 count_vm_event(THP_FAULT_ALLOC);
1260 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1262 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1263 __SetPageUptodate(new_page);
1266 mmun_end = haddr + HPAGE_PMD_SIZE;
1267 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1272 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1274 mem_cgroup_cancel_charge(new_page, memcg, true);
1279 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1280 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1281 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1282 page_add_new_anon_rmap(new_page, vma, haddr, true);
1283 mem_cgroup_commit_charge(new_page, memcg, false, true);
1284 lru_cache_add_active_or_unevictable(new_page, vma);
1285 set_pmd_at(mm, haddr, pmd, entry);
1286 update_mmu_cache_pmd(vma, address, pmd);
1288 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1289 put_huge_zero_page();
1291 VM_BUG_ON_PAGE(!PageHead(page), page);
1292 page_remove_rmap(page, true);
1295 ret |= VM_FAULT_WRITE;
1299 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1307 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1312 struct mm_struct *mm = vma->vm_mm;
1313 struct page *page = NULL;
1315 assert_spin_locked(pmd_lockptr(mm, pmd));
1317 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1320 /* Avoid dumping huge zero page */
1321 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1322 return ERR_PTR(-EFAULT);
1324 /* Full NUMA hinting faults to serialise migration in fault paths */
1325 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1328 page = pmd_page(*pmd);
1329 VM_BUG_ON_PAGE(!PageHead(page), page);
1330 if (flags & FOLL_TOUCH) {
1333 * We should set the dirty bit only for FOLL_WRITE but
1334 * for now the dirty bit in the pmd is meaningless.
1335 * And if the dirty bit will become meaningful and
1336 * we'll only set it with FOLL_WRITE, an atomic
1337 * set_bit will be required on the pmd to set the
1338 * young bit, instead of the current set_pmd_at.
1340 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1341 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1343 update_mmu_cache_pmd(vma, addr, pmd);
1345 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1347 * We don't mlock() pte-mapped THPs. This way we can avoid
1348 * leaking mlocked pages into non-VM_LOCKED VMAs.
1350 * In most cases the pmd is the only mapping of the page as we
1351 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1352 * writable private mappings in populate_vma_page_range().
1354 * The only scenario when we have the page shared here is if we
1355 * mlocking read-only mapping shared over fork(). We skip
1356 * mlocking such pages.
1358 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) &&
1359 page->mapping && trylock_page(page)) {
1362 mlock_vma_page(page);
1366 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1367 VM_BUG_ON_PAGE(!PageCompound(page), page);
1368 if (flags & FOLL_GET)
1375 /* NUMA hinting page fault entry point for trans huge pmds */
1376 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1377 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1380 struct anon_vma *anon_vma = NULL;
1382 unsigned long haddr = addr & HPAGE_PMD_MASK;
1383 int page_nid = -1, this_nid = numa_node_id();
1384 int target_nid, last_cpupid = -1;
1386 bool migrated = false;
1390 /* A PROT_NONE fault should not end up here */
1391 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1393 ptl = pmd_lock(mm, pmdp);
1394 if (unlikely(!pmd_same(pmd, *pmdp)))
1398 * If there are potential migrations, wait for completion and retry
1399 * without disrupting NUMA hinting information. Do not relock and
1400 * check_same as the page may no longer be mapped.
1402 if (unlikely(pmd_trans_migrating(*pmdp))) {
1403 page = pmd_page(*pmdp);
1405 wait_on_page_locked(page);
1409 page = pmd_page(pmd);
1410 BUG_ON(is_huge_zero_page(page));
1411 page_nid = page_to_nid(page);
1412 last_cpupid = page_cpupid_last(page);
1413 count_vm_numa_event(NUMA_HINT_FAULTS);
1414 if (page_nid == this_nid) {
1415 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1416 flags |= TNF_FAULT_LOCAL;
1419 /* See similar comment in do_numa_page for explanation */
1420 if (!(vma->vm_flags & VM_WRITE))
1421 flags |= TNF_NO_GROUP;
1424 * Acquire the page lock to serialise THP migrations but avoid dropping
1425 * page_table_lock if at all possible
1427 page_locked = trylock_page(page);
1428 target_nid = mpol_misplaced(page, vma, haddr);
1429 if (target_nid == -1) {
1430 /* If the page was locked, there are no parallel migrations */
1435 /* Migration could have started since the pmd_trans_migrating check */
1438 wait_on_page_locked(page);
1444 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1445 * to serialises splits
1449 anon_vma = page_lock_anon_vma_read(page);
1451 /* Confirm the PMD did not change while page_table_lock was released */
1453 if (unlikely(!pmd_same(pmd, *pmdp))) {
1460 /* Bail if we fail to protect against THP splits for any reason */
1461 if (unlikely(!anon_vma)) {
1468 * Migrate the THP to the requested node, returns with page unlocked
1469 * and access rights restored.
1472 migrated = migrate_misplaced_transhuge_page(mm, vma,
1473 pmdp, pmd, addr, page, target_nid);
1475 flags |= TNF_MIGRATED;
1476 page_nid = target_nid;
1478 flags |= TNF_MIGRATE_FAIL;
1482 BUG_ON(!PageLocked(page));
1483 was_writable = pmd_write(pmd);
1484 pmd = pmd_modify(pmd, vma->vm_page_prot);
1485 pmd = pmd_mkyoung(pmd);
1487 pmd = pmd_mkwrite(pmd);
1488 set_pmd_at(mm, haddr, pmdp, pmd);
1489 update_mmu_cache_pmd(vma, addr, pmdp);
1496 page_unlock_anon_vma_read(anon_vma);
1499 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1504 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1505 pmd_t *pmd, unsigned long addr)
1510 if (!__pmd_trans_huge_lock(pmd, vma, &ptl))
1513 * For architectures like ppc64 we look at deposited pgtable
1514 * when calling pmdp_huge_get_and_clear. So do the
1515 * pgtable_trans_huge_withdraw after finishing pmdp related
1518 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1520 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1521 if (vma_is_dax(vma)) {
1523 if (is_huge_zero_pmd(orig_pmd))
1524 put_huge_zero_page();
1525 } else if (is_huge_zero_pmd(orig_pmd)) {
1526 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1527 atomic_long_dec(&tlb->mm->nr_ptes);
1529 put_huge_zero_page();
1531 struct page *page = pmd_page(orig_pmd);
1532 page_remove_rmap(page, true);
1533 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1534 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1535 VM_BUG_ON_PAGE(!PageHead(page), page);
1536 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1537 atomic_long_dec(&tlb->mm->nr_ptes);
1539 tlb_remove_page(tlb, page);
1544 bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1545 unsigned long old_addr,
1546 unsigned long new_addr, unsigned long old_end,
1547 pmd_t *old_pmd, pmd_t *new_pmd)
1549 spinlock_t *old_ptl, *new_ptl;
1552 struct mm_struct *mm = vma->vm_mm;
1554 if ((old_addr & ~HPAGE_PMD_MASK) ||
1555 (new_addr & ~HPAGE_PMD_MASK) ||
1556 old_end - old_addr < HPAGE_PMD_SIZE ||
1557 (new_vma->vm_flags & VM_NOHUGEPAGE))
1561 * The destination pmd shouldn't be established, free_pgtables()
1562 * should have release it.
1564 if (WARN_ON(!pmd_none(*new_pmd))) {
1565 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1570 * We don't have to worry about the ordering of src and dst
1571 * ptlocks because exclusive mmap_sem prevents deadlock.
1573 if (__pmd_trans_huge_lock(old_pmd, vma, &old_ptl)) {
1574 new_ptl = pmd_lockptr(mm, new_pmd);
1575 if (new_ptl != old_ptl)
1576 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1577 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1578 VM_BUG_ON(!pmd_none(*new_pmd));
1580 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1582 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1583 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1585 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1586 if (new_ptl != old_ptl)
1587 spin_unlock(new_ptl);
1588 spin_unlock(old_ptl);
1596 * - 0 if PMD could not be locked
1597 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1598 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1600 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1601 unsigned long addr, pgprot_t newprot, int prot_numa)
1603 struct mm_struct *mm = vma->vm_mm;
1607 if (__pmd_trans_huge_lock(pmd, vma, &ptl)) {
1609 bool preserve_write = prot_numa && pmd_write(*pmd);
1613 * Avoid trapping faults against the zero page. The read-only
1614 * data is likely to be read-cached on the local CPU and
1615 * local/remote hits to the zero page are not interesting.
1617 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1622 if (!prot_numa || !pmd_protnone(*pmd)) {
1623 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1624 entry = pmd_modify(entry, newprot);
1626 entry = pmd_mkwrite(entry);
1628 set_pmd_at(mm, addr, pmd, entry);
1629 BUG_ON(!preserve_write && pmd_write(entry));
1638 * Returns true if a given pmd maps a thp, false otherwise.
1640 * Note that if it returns true, this routine returns without unlocking page
1641 * table lock. So callers must unlock it.
1643 bool __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1646 *ptl = pmd_lock(vma->vm_mm, pmd);
1647 if (likely(pmd_trans_huge(*pmd)))
1653 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1655 int hugepage_madvise(struct vm_area_struct *vma,
1656 unsigned long *vm_flags, int advice)
1662 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1663 * can't handle this properly after s390_enable_sie, so we simply
1664 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1666 if (mm_has_pgste(vma->vm_mm))
1670 * Be somewhat over-protective like KSM for now!
1672 if (*vm_flags & VM_NO_THP)
1674 *vm_flags &= ~VM_NOHUGEPAGE;
1675 *vm_flags |= VM_HUGEPAGE;
1677 * If the vma become good for khugepaged to scan,
1678 * register it here without waiting a page fault that
1679 * may not happen any time soon.
1681 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1684 case MADV_NOHUGEPAGE:
1686 * Be somewhat over-protective like KSM for now!
1688 if (*vm_flags & VM_NO_THP)
1690 *vm_flags &= ~VM_HUGEPAGE;
1691 *vm_flags |= VM_NOHUGEPAGE;
1693 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1694 * this vma even if we leave the mm registered in khugepaged if
1695 * it got registered before VM_NOHUGEPAGE was set.
1703 static int __init khugepaged_slab_init(void)
1705 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1706 sizeof(struct mm_slot),
1707 __alignof__(struct mm_slot), 0, NULL);
1714 static void __init khugepaged_slab_exit(void)
1716 kmem_cache_destroy(mm_slot_cache);
1719 static inline struct mm_slot *alloc_mm_slot(void)
1721 if (!mm_slot_cache) /* initialization failed */
1723 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1726 static inline void free_mm_slot(struct mm_slot *mm_slot)
1728 kmem_cache_free(mm_slot_cache, mm_slot);
1731 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1733 struct mm_slot *mm_slot;
1735 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1736 if (mm == mm_slot->mm)
1742 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1743 struct mm_slot *mm_slot)
1746 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1749 static inline int khugepaged_test_exit(struct mm_struct *mm)
1751 return atomic_read(&mm->mm_users) == 0;
1754 int __khugepaged_enter(struct mm_struct *mm)
1756 struct mm_slot *mm_slot;
1759 mm_slot = alloc_mm_slot();
1763 /* __khugepaged_exit() must not run from under us */
1764 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1765 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1766 free_mm_slot(mm_slot);
1770 spin_lock(&khugepaged_mm_lock);
1771 insert_to_mm_slots_hash(mm, mm_slot);
1773 * Insert just behind the scanning cursor, to let the area settle
1776 wakeup = list_empty(&khugepaged_scan.mm_head);
1777 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1778 spin_unlock(&khugepaged_mm_lock);
1780 atomic_inc(&mm->mm_count);
1782 wake_up_interruptible(&khugepaged_wait);
1787 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1788 unsigned long vm_flags)
1790 unsigned long hstart, hend;
1793 * Not yet faulted in so we will register later in the
1794 * page fault if needed.
1798 /* khugepaged not yet working on file or special mappings */
1800 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
1801 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1802 hend = vma->vm_end & HPAGE_PMD_MASK;
1804 return khugepaged_enter(vma, vm_flags);
1808 void __khugepaged_exit(struct mm_struct *mm)
1810 struct mm_slot *mm_slot;
1813 spin_lock(&khugepaged_mm_lock);
1814 mm_slot = get_mm_slot(mm);
1815 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1816 hash_del(&mm_slot->hash);
1817 list_del(&mm_slot->mm_node);
1820 spin_unlock(&khugepaged_mm_lock);
1823 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1824 free_mm_slot(mm_slot);
1826 } else if (mm_slot) {
1828 * This is required to serialize against
1829 * khugepaged_test_exit() (which is guaranteed to run
1830 * under mmap sem read mode). Stop here (after we
1831 * return all pagetables will be destroyed) until
1832 * khugepaged has finished working on the pagetables
1833 * under the mmap_sem.
1835 down_write(&mm->mmap_sem);
1836 up_write(&mm->mmap_sem);
1840 static void release_pte_page(struct page *page)
1842 /* 0 stands for page_is_file_cache(page) == false */
1843 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1845 putback_lru_page(page);
1848 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1850 while (--_pte >= pte) {
1851 pte_t pteval = *_pte;
1852 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
1853 release_pte_page(pte_page(pteval));
1857 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1858 unsigned long address,
1861 struct page *page = NULL;
1863 int none_or_zero = 0, result = 0;
1864 bool referenced = false, writable = false;
1866 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1867 _pte++, address += PAGE_SIZE) {
1868 pte_t pteval = *_pte;
1869 if (pte_none(pteval) || (pte_present(pteval) &&
1870 is_zero_pfn(pte_pfn(pteval)))) {
1871 if (!userfaultfd_armed(vma) &&
1872 ++none_or_zero <= khugepaged_max_ptes_none) {
1875 result = SCAN_EXCEED_NONE_PTE;
1879 if (!pte_present(pteval)) {
1880 result = SCAN_PTE_NON_PRESENT;
1883 page = vm_normal_page(vma, address, pteval);
1884 if (unlikely(!page)) {
1885 result = SCAN_PAGE_NULL;
1889 VM_BUG_ON_PAGE(PageCompound(page), page);
1890 VM_BUG_ON_PAGE(!PageAnon(page), page);
1891 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
1894 * We can do it before isolate_lru_page because the
1895 * page can't be freed from under us. NOTE: PG_lock
1896 * is needed to serialize against split_huge_page
1897 * when invoked from the VM.
1899 if (!trylock_page(page)) {
1900 result = SCAN_PAGE_LOCK;
1905 * cannot use mapcount: can't collapse if there's a gup pin.
1906 * The page must only be referenced by the scanned process
1907 * and page swap cache.
1909 if (page_count(page) != 1 + !!PageSwapCache(page)) {
1911 result = SCAN_PAGE_COUNT;
1914 if (pte_write(pteval)) {
1917 if (PageSwapCache(page) && !reuse_swap_page(page)) {
1919 result = SCAN_SWAP_CACHE_PAGE;
1923 * Page is not in the swap cache. It can be collapsed
1929 * Isolate the page to avoid collapsing an hugepage
1930 * currently in use by the VM.
1932 if (isolate_lru_page(page)) {
1934 result = SCAN_DEL_PAGE_LRU;
1937 /* 0 stands for page_is_file_cache(page) == false */
1938 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1939 VM_BUG_ON_PAGE(!PageLocked(page), page);
1940 VM_BUG_ON_PAGE(PageLRU(page), page);
1942 /* If there is no mapped pte young don't collapse the page */
1943 if (pte_young(pteval) ||
1944 page_is_young(page) || PageReferenced(page) ||
1945 mmu_notifier_test_young(vma->vm_mm, address))
1948 if (likely(writable)) {
1949 if (likely(referenced)) {
1950 result = SCAN_SUCCEED;
1951 trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
1952 referenced, writable, result);
1956 result = SCAN_PAGE_RO;
1960 release_pte_pages(pte, _pte);
1961 trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
1962 referenced, writable, result);
1966 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1967 struct vm_area_struct *vma,
1968 unsigned long address,
1972 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1973 pte_t pteval = *_pte;
1974 struct page *src_page;
1976 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1977 clear_user_highpage(page, address);
1978 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1979 if (is_zero_pfn(pte_pfn(pteval))) {
1981 * ptl mostly unnecessary.
1985 * paravirt calls inside pte_clear here are
1988 pte_clear(vma->vm_mm, address, _pte);
1992 src_page = pte_page(pteval);
1993 copy_user_highpage(page, src_page, address, vma);
1994 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
1995 release_pte_page(src_page);
1997 * ptl mostly unnecessary, but preempt has to
1998 * be disabled to update the per-cpu stats
1999 * inside page_remove_rmap().
2003 * paravirt calls inside pte_clear here are
2006 pte_clear(vma->vm_mm, address, _pte);
2007 page_remove_rmap(src_page, false);
2009 free_page_and_swap_cache(src_page);
2012 address += PAGE_SIZE;
2017 static void khugepaged_alloc_sleep(void)
2021 add_wait_queue(&khugepaged_wait, &wait);
2022 freezable_schedule_timeout_interruptible(
2023 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2024 remove_wait_queue(&khugepaged_wait, &wait);
2027 static int khugepaged_node_load[MAX_NUMNODES];
2029 static bool khugepaged_scan_abort(int nid)
2034 * If zone_reclaim_mode is disabled, then no extra effort is made to
2035 * allocate memory locally.
2037 if (!zone_reclaim_mode)
2040 /* If there is a count for this node already, it must be acceptable */
2041 if (khugepaged_node_load[nid])
2044 for (i = 0; i < MAX_NUMNODES; i++) {
2045 if (!khugepaged_node_load[i])
2047 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2054 static int khugepaged_find_target_node(void)
2056 static int last_khugepaged_target_node = NUMA_NO_NODE;
2057 int nid, target_node = 0, max_value = 0;
2059 /* find first node with max normal pages hit */
2060 for (nid = 0; nid < MAX_NUMNODES; nid++)
2061 if (khugepaged_node_load[nid] > max_value) {
2062 max_value = khugepaged_node_load[nid];
2066 /* do some balance if several nodes have the same hit record */
2067 if (target_node <= last_khugepaged_target_node)
2068 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2070 if (max_value == khugepaged_node_load[nid]) {
2075 last_khugepaged_target_node = target_node;
2079 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2081 if (IS_ERR(*hpage)) {
2087 khugepaged_alloc_sleep();
2088 } else if (*hpage) {
2096 static struct page *
2097 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2098 unsigned long address, int node)
2100 VM_BUG_ON_PAGE(*hpage, *hpage);
2103 * Before allocating the hugepage, release the mmap_sem read lock.
2104 * The allocation can take potentially a long time if it involves
2105 * sync compaction, and we do not need to hold the mmap_sem during
2106 * that. We will recheck the vma after taking it again in write mode.
2108 up_read(&mm->mmap_sem);
2110 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2111 if (unlikely(!*hpage)) {
2112 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2113 *hpage = ERR_PTR(-ENOMEM);
2117 prep_transhuge_page(*hpage);
2118 count_vm_event(THP_COLLAPSE_ALLOC);
2122 static int khugepaged_find_target_node(void)
2127 static inline struct page *alloc_hugepage(int defrag)
2131 page = alloc_pages(alloc_hugepage_gfpmask(defrag, 0), HPAGE_PMD_ORDER);
2133 prep_transhuge_page(page);
2137 static struct page *khugepaged_alloc_hugepage(bool *wait)
2142 hpage = alloc_hugepage(khugepaged_defrag());
2144 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2149 khugepaged_alloc_sleep();
2151 count_vm_event(THP_COLLAPSE_ALLOC);
2152 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2157 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2160 *hpage = khugepaged_alloc_hugepage(wait);
2162 if (unlikely(!*hpage))
2168 static struct page *
2169 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2170 unsigned long address, int node)
2172 up_read(&mm->mmap_sem);
2179 static bool hugepage_vma_check(struct vm_area_struct *vma)
2181 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2182 (vma->vm_flags & VM_NOHUGEPAGE))
2184 if (!vma->anon_vma || vma->vm_ops)
2186 if (is_vma_temporary_stack(vma))
2188 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2192 static void collapse_huge_page(struct mm_struct *mm,
2193 unsigned long address,
2194 struct page **hpage,
2195 struct vm_area_struct *vma,
2201 struct page *new_page;
2202 spinlock_t *pmd_ptl, *pte_ptl;
2203 int isolated, result = 0;
2204 unsigned long hstart, hend;
2205 struct mem_cgroup *memcg;
2206 unsigned long mmun_start; /* For mmu_notifiers */
2207 unsigned long mmun_end; /* For mmu_notifiers */
2210 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2212 /* Only allocate from the target node */
2213 gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2216 /* release the mmap_sem read lock. */
2217 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2219 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2223 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2224 result = SCAN_CGROUP_CHARGE_FAIL;
2229 * Prevent all access to pagetables with the exception of
2230 * gup_fast later hanlded by the ptep_clear_flush and the VM
2231 * handled by the anon_vma lock + PG_lock.
2233 down_write(&mm->mmap_sem);
2234 if (unlikely(khugepaged_test_exit(mm))) {
2235 result = SCAN_ANY_PROCESS;
2239 vma = find_vma(mm, address);
2241 result = SCAN_VMA_NULL;
2244 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2245 hend = vma->vm_end & HPAGE_PMD_MASK;
2246 if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
2247 result = SCAN_ADDRESS_RANGE;
2250 if (!hugepage_vma_check(vma)) {
2251 result = SCAN_VMA_CHECK;
2254 pmd = mm_find_pmd(mm, address);
2256 result = SCAN_PMD_NULL;
2260 anon_vma_lock_write(vma->anon_vma);
2262 pte = pte_offset_map(pmd, address);
2263 pte_ptl = pte_lockptr(mm, pmd);
2265 mmun_start = address;
2266 mmun_end = address + HPAGE_PMD_SIZE;
2267 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2268 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2270 * After this gup_fast can't run anymore. This also removes
2271 * any huge TLB entry from the CPU so we won't allow
2272 * huge and small TLB entries for the same virtual address
2273 * to avoid the risk of CPU bugs in that area.
2275 _pmd = pmdp_collapse_flush(vma, address, pmd);
2276 spin_unlock(pmd_ptl);
2277 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2280 isolated = __collapse_huge_page_isolate(vma, address, pte);
2281 spin_unlock(pte_ptl);
2283 if (unlikely(!isolated)) {
2286 BUG_ON(!pmd_none(*pmd));
2288 * We can only use set_pmd_at when establishing
2289 * hugepmds and never for establishing regular pmds that
2290 * points to regular pagetables. Use pmd_populate for that
2292 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2293 spin_unlock(pmd_ptl);
2294 anon_vma_unlock_write(vma->anon_vma);
2300 * All pages are isolated and locked so anon_vma rmap
2301 * can't run anymore.
2303 anon_vma_unlock_write(vma->anon_vma);
2305 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2307 __SetPageUptodate(new_page);
2308 pgtable = pmd_pgtable(_pmd);
2310 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2311 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2314 * spin_lock() below is not the equivalent of smp_wmb(), so
2315 * this is needed to avoid the copy_huge_page writes to become
2316 * visible after the set_pmd_at() write.
2321 BUG_ON(!pmd_none(*pmd));
2322 page_add_new_anon_rmap(new_page, vma, address, true);
2323 mem_cgroup_commit_charge(new_page, memcg, false, true);
2324 lru_cache_add_active_or_unevictable(new_page, vma);
2325 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2326 set_pmd_at(mm, address, pmd, _pmd);
2327 update_mmu_cache_pmd(vma, address, pmd);
2328 spin_unlock(pmd_ptl);
2332 khugepaged_pages_collapsed++;
2333 result = SCAN_SUCCEED;
2335 up_write(&mm->mmap_sem);
2336 trace_mm_collapse_huge_page(mm, isolated, result);
2340 trace_mm_collapse_huge_page(mm, isolated, result);
2343 mem_cgroup_cancel_charge(new_page, memcg, true);
2347 static int khugepaged_scan_pmd(struct mm_struct *mm,
2348 struct vm_area_struct *vma,
2349 unsigned long address,
2350 struct page **hpage)
2354 int ret = 0, none_or_zero = 0, result = 0;
2355 struct page *page = NULL;
2356 unsigned long _address;
2358 int node = NUMA_NO_NODE;
2359 bool writable = false, referenced = false;
2361 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2363 pmd = mm_find_pmd(mm, address);
2365 result = SCAN_PMD_NULL;
2369 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2370 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2371 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2372 _pte++, _address += PAGE_SIZE) {
2373 pte_t pteval = *_pte;
2374 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2375 if (!userfaultfd_armed(vma) &&
2376 ++none_or_zero <= khugepaged_max_ptes_none) {
2379 result = SCAN_EXCEED_NONE_PTE;
2383 if (!pte_present(pteval)) {
2384 result = SCAN_PTE_NON_PRESENT;
2387 if (pte_write(pteval))
2390 page = vm_normal_page(vma, _address, pteval);
2391 if (unlikely(!page)) {
2392 result = SCAN_PAGE_NULL;
2396 /* TODO: teach khugepaged to collapse THP mapped with pte */
2397 if (PageCompound(page)) {
2398 result = SCAN_PAGE_COMPOUND;
2403 * Record which node the original page is from and save this
2404 * information to khugepaged_node_load[].
2405 * Khupaged will allocate hugepage from the node has the max
2408 node = page_to_nid(page);
2409 if (khugepaged_scan_abort(node)) {
2410 result = SCAN_SCAN_ABORT;
2413 khugepaged_node_load[node]++;
2414 if (!PageLRU(page)) {
2415 result = SCAN_SCAN_ABORT;
2418 if (PageLocked(page)) {
2419 result = SCAN_PAGE_LOCK;
2422 if (!PageAnon(page)) {
2423 result = SCAN_PAGE_ANON;
2428 * cannot use mapcount: can't collapse if there's a gup pin.
2429 * The page must only be referenced by the scanned process
2430 * and page swap cache.
2432 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2433 result = SCAN_PAGE_COUNT;
2436 if (pte_young(pteval) ||
2437 page_is_young(page) || PageReferenced(page) ||
2438 mmu_notifier_test_young(vma->vm_mm, address))
2443 result = SCAN_SUCCEED;
2446 result = SCAN_NO_REFERENCED_PAGE;
2449 result = SCAN_PAGE_RO;
2452 pte_unmap_unlock(pte, ptl);
2454 node = khugepaged_find_target_node();
2455 /* collapse_huge_page will return with the mmap_sem released */
2456 collapse_huge_page(mm, address, hpage, vma, node);
2459 trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
2460 none_or_zero, result);
2464 static void collect_mm_slot(struct mm_slot *mm_slot)
2466 struct mm_struct *mm = mm_slot->mm;
2468 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2470 if (khugepaged_test_exit(mm)) {
2472 hash_del(&mm_slot->hash);
2473 list_del(&mm_slot->mm_node);
2476 * Not strictly needed because the mm exited already.
2478 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2481 /* khugepaged_mm_lock actually not necessary for the below */
2482 free_mm_slot(mm_slot);
2487 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2488 struct page **hpage)
2489 __releases(&khugepaged_mm_lock)
2490 __acquires(&khugepaged_mm_lock)
2492 struct mm_slot *mm_slot;
2493 struct mm_struct *mm;
2494 struct vm_area_struct *vma;
2498 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2500 if (khugepaged_scan.mm_slot)
2501 mm_slot = khugepaged_scan.mm_slot;
2503 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2504 struct mm_slot, mm_node);
2505 khugepaged_scan.address = 0;
2506 khugepaged_scan.mm_slot = mm_slot;
2508 spin_unlock(&khugepaged_mm_lock);
2511 down_read(&mm->mmap_sem);
2512 if (unlikely(khugepaged_test_exit(mm)))
2515 vma = find_vma(mm, khugepaged_scan.address);
2518 for (; vma; vma = vma->vm_next) {
2519 unsigned long hstart, hend;
2522 if (unlikely(khugepaged_test_exit(mm))) {
2526 if (!hugepage_vma_check(vma)) {
2531 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2532 hend = vma->vm_end & HPAGE_PMD_MASK;
2535 if (khugepaged_scan.address > hend)
2537 if (khugepaged_scan.address < hstart)
2538 khugepaged_scan.address = hstart;
2539 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2541 while (khugepaged_scan.address < hend) {
2544 if (unlikely(khugepaged_test_exit(mm)))
2545 goto breakouterloop;
2547 VM_BUG_ON(khugepaged_scan.address < hstart ||
2548 khugepaged_scan.address + HPAGE_PMD_SIZE >
2550 ret = khugepaged_scan_pmd(mm, vma,
2551 khugepaged_scan.address,
2553 /* move to next address */
2554 khugepaged_scan.address += HPAGE_PMD_SIZE;
2555 progress += HPAGE_PMD_NR;
2557 /* we released mmap_sem so break loop */
2558 goto breakouterloop_mmap_sem;
2559 if (progress >= pages)
2560 goto breakouterloop;
2564 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2565 breakouterloop_mmap_sem:
2567 spin_lock(&khugepaged_mm_lock);
2568 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2570 * Release the current mm_slot if this mm is about to die, or
2571 * if we scanned all vmas of this mm.
2573 if (khugepaged_test_exit(mm) || !vma) {
2575 * Make sure that if mm_users is reaching zero while
2576 * khugepaged runs here, khugepaged_exit will find
2577 * mm_slot not pointing to the exiting mm.
2579 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2580 khugepaged_scan.mm_slot = list_entry(
2581 mm_slot->mm_node.next,
2582 struct mm_slot, mm_node);
2583 khugepaged_scan.address = 0;
2585 khugepaged_scan.mm_slot = NULL;
2586 khugepaged_full_scans++;
2589 collect_mm_slot(mm_slot);
2595 static int khugepaged_has_work(void)
2597 return !list_empty(&khugepaged_scan.mm_head) &&
2598 khugepaged_enabled();
2601 static int khugepaged_wait_event(void)
2603 return !list_empty(&khugepaged_scan.mm_head) ||
2604 kthread_should_stop();
2607 static void khugepaged_do_scan(void)
2609 struct page *hpage = NULL;
2610 unsigned int progress = 0, pass_through_head = 0;
2611 unsigned int pages = khugepaged_pages_to_scan;
2614 barrier(); /* write khugepaged_pages_to_scan to local stack */
2616 while (progress < pages) {
2617 if (!khugepaged_prealloc_page(&hpage, &wait))
2622 if (unlikely(kthread_should_stop() || try_to_freeze()))
2625 spin_lock(&khugepaged_mm_lock);
2626 if (!khugepaged_scan.mm_slot)
2627 pass_through_head++;
2628 if (khugepaged_has_work() &&
2629 pass_through_head < 2)
2630 progress += khugepaged_scan_mm_slot(pages - progress,
2634 spin_unlock(&khugepaged_mm_lock);
2637 if (!IS_ERR_OR_NULL(hpage))
2641 static void khugepaged_wait_work(void)
2643 if (khugepaged_has_work()) {
2644 if (!khugepaged_scan_sleep_millisecs)
2647 wait_event_freezable_timeout(khugepaged_wait,
2648 kthread_should_stop(),
2649 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2653 if (khugepaged_enabled())
2654 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2657 static int khugepaged(void *none)
2659 struct mm_slot *mm_slot;
2662 set_user_nice(current, MAX_NICE);
2664 while (!kthread_should_stop()) {
2665 khugepaged_do_scan();
2666 khugepaged_wait_work();
2669 spin_lock(&khugepaged_mm_lock);
2670 mm_slot = khugepaged_scan.mm_slot;
2671 khugepaged_scan.mm_slot = NULL;
2673 collect_mm_slot(mm_slot);
2674 spin_unlock(&khugepaged_mm_lock);
2678 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2679 unsigned long haddr, pmd_t *pmd)
2681 struct mm_struct *mm = vma->vm_mm;
2686 /* leave pmd empty until pte is filled */
2687 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2689 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2690 pmd_populate(mm, &_pmd, pgtable);
2692 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2694 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2695 entry = pte_mkspecial(entry);
2696 pte = pte_offset_map(&_pmd, haddr);
2697 VM_BUG_ON(!pte_none(*pte));
2698 set_pte_at(mm, haddr, pte, entry);
2701 smp_wmb(); /* make pte visible before pmd */
2702 pmd_populate(mm, pmd, pgtable);
2703 put_huge_zero_page();
2706 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2707 unsigned long haddr, bool freeze)
2709 struct mm_struct *mm = vma->vm_mm;
2716 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2717 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2718 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2719 VM_BUG_ON(!pmd_trans_huge(*pmd));
2721 count_vm_event(THP_SPLIT_PMD);
2723 if (vma_is_dax(vma)) {
2724 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2725 if (is_huge_zero_pmd(_pmd))
2726 put_huge_zero_page();
2728 } else if (is_huge_zero_pmd(*pmd)) {
2729 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2732 page = pmd_page(*pmd);
2733 VM_BUG_ON_PAGE(!page_count(page), page);
2734 atomic_add(HPAGE_PMD_NR - 1, &page->_count);
2735 write = pmd_write(*pmd);
2736 young = pmd_young(*pmd);
2738 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2739 pmd_populate(mm, &_pmd, pgtable);
2741 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2744 * Note that NUMA hinting access restrictions are not
2745 * transferred to avoid any possibility of altering
2746 * permissions across VMAs.
2749 swp_entry_t swp_entry;
2750 swp_entry = make_migration_entry(page + i, write);
2751 entry = swp_entry_to_pte(swp_entry);
2753 entry = mk_pte(page + i, vma->vm_page_prot);
2754 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2756 entry = pte_wrprotect(entry);
2758 entry = pte_mkold(entry);
2760 pte = pte_offset_map(&_pmd, haddr);
2761 BUG_ON(!pte_none(*pte));
2762 set_pte_at(mm, haddr, pte, entry);
2763 atomic_inc(&page[i]._mapcount);
2768 * Set PG_double_map before dropping compound_mapcount to avoid
2769 * false-negative page_mapped().
2771 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2772 for (i = 0; i < HPAGE_PMD_NR; i++)
2773 atomic_inc(&page[i]._mapcount);
2776 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2777 /* Last compound_mapcount is gone. */
2778 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
2779 if (TestClearPageDoubleMap(page)) {
2780 /* No need in mapcount reference anymore */
2781 for (i = 0; i < HPAGE_PMD_NR; i++)
2782 atomic_dec(&page[i]._mapcount);
2786 smp_wmb(); /* make pte visible before pmd */
2788 * Up to this point the pmd is present and huge and userland has the
2789 * whole access to the hugepage during the split (which happens in
2790 * place). If we overwrite the pmd with the not-huge version pointing
2791 * to the pte here (which of course we could if all CPUs were bug
2792 * free), userland could trigger a small page size TLB miss on the
2793 * small sized TLB while the hugepage TLB entry is still established in
2794 * the huge TLB. Some CPU doesn't like that.
2795 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2796 * 383 on page 93. Intel should be safe but is also warns that it's
2797 * only safe if the permission and cache attributes of the two entries
2798 * loaded in the two TLB is identical (which should be the case here).
2799 * But it is generally safer to never allow small and huge TLB entries
2800 * for the same virtual address to be loaded simultaneously. So instead
2801 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2802 * current pmd notpresent (atomically because here the pmd_trans_huge
2803 * and pmd_trans_splitting must remain set at all times on the pmd
2804 * until the split is complete for this pmd), then we flush the SMP TLB
2805 * and finally we write the non-huge version of the pmd entry with
2808 pmdp_invalidate(vma, haddr, pmd);
2809 pmd_populate(mm, pmd, pgtable);
2812 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2813 page_remove_rmap(page + i, false);
2819 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2820 unsigned long address)
2823 struct mm_struct *mm = vma->vm_mm;
2824 struct page *page = NULL;
2825 unsigned long haddr = address & HPAGE_PMD_MASK;
2827 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2828 ptl = pmd_lock(mm, pmd);
2829 if (unlikely(!pmd_trans_huge(*pmd)))
2831 page = pmd_page(*pmd);
2832 __split_huge_pmd_locked(vma, pmd, haddr, false);
2833 if (PageMlocked(page))
2839 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
2842 munlock_vma_page(page);
2848 static void split_huge_pmd_address(struct vm_area_struct *vma,
2849 unsigned long address)
2855 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2857 pgd = pgd_offset(vma->vm_mm, address);
2858 if (!pgd_present(*pgd))
2861 pud = pud_offset(pgd, address);
2862 if (!pud_present(*pud))
2865 pmd = pmd_offset(pud, address);
2866 if (!pmd_present(*pmd) || !pmd_trans_huge(*pmd))
2869 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2870 * materialize from under us.
2872 split_huge_pmd(vma, pmd, address);
2875 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2876 unsigned long start,
2881 * If the new start address isn't hpage aligned and it could
2882 * previously contain an hugepage: check if we need to split
2885 if (start & ~HPAGE_PMD_MASK &&
2886 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2887 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2888 split_huge_pmd_address(vma, start);
2891 * If the new end address isn't hpage aligned and it could
2892 * previously contain an hugepage: check if we need to split
2895 if (end & ~HPAGE_PMD_MASK &&
2896 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2897 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2898 split_huge_pmd_address(vma, end);
2901 * If we're also updating the vma->vm_next->vm_start, if the new
2902 * vm_next->vm_start isn't page aligned and it could previously
2903 * contain an hugepage: check if we need to split an huge pmd.
2905 if (adjust_next > 0) {
2906 struct vm_area_struct *next = vma->vm_next;
2907 unsigned long nstart = next->vm_start;
2908 nstart += adjust_next << PAGE_SHIFT;
2909 if (nstart & ~HPAGE_PMD_MASK &&
2910 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2911 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2912 split_huge_pmd_address(next, nstart);
2916 static void freeze_page_vma(struct vm_area_struct *vma, struct page *page,
2917 unsigned long address)
2924 int i, nr = HPAGE_PMD_NR;
2926 /* Skip pages which doesn't belong to the VMA */
2927 if (address < vma->vm_start) {
2928 int off = (vma->vm_start - address) >> PAGE_SHIFT;
2931 address = vma->vm_start;
2934 pgd = pgd_offset(vma->vm_mm, address);
2935 if (!pgd_present(*pgd))
2937 pud = pud_offset(pgd, address);
2938 if (!pud_present(*pud))
2940 pmd = pmd_offset(pud, address);
2941 ptl = pmd_lock(vma->vm_mm, pmd);
2942 if (!pmd_present(*pmd)) {
2946 if (pmd_trans_huge(*pmd)) {
2947 if (page == pmd_page(*pmd))
2948 __split_huge_pmd_locked(vma, pmd, address, true);
2954 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
2955 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++) {
2956 pte_t entry, swp_pte;
2957 swp_entry_t swp_entry;
2959 if (!pte_present(pte[i]))
2961 if (page_to_pfn(page) != pte_pfn(pte[i]))
2963 flush_cache_page(vma, address, page_to_pfn(page));
2964 entry = ptep_clear_flush(vma, address, pte + i);
2965 swp_entry = make_migration_entry(page, pte_write(entry));
2966 swp_pte = swp_entry_to_pte(swp_entry);
2967 if (pte_soft_dirty(entry))
2968 swp_pte = pte_swp_mksoft_dirty(swp_pte);
2969 set_pte_at(vma->vm_mm, address, pte + i, swp_pte);
2970 page_remove_rmap(page, false);
2973 pte_unmap_unlock(pte, ptl);
2976 static void freeze_page(struct anon_vma *anon_vma, struct page *page)
2978 struct anon_vma_chain *avc;
2979 pgoff_t pgoff = page_to_pgoff(page);
2981 VM_BUG_ON_PAGE(!PageHead(page), page);
2983 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff,
2984 pgoff + HPAGE_PMD_NR - 1) {
2985 unsigned long haddr;
2987 haddr = __vma_address(page, avc->vma) & HPAGE_PMD_MASK;
2988 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
2989 haddr, haddr + HPAGE_PMD_SIZE);
2990 freeze_page_vma(avc->vma, page, haddr);
2991 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
2992 haddr, haddr + HPAGE_PMD_SIZE);
2996 static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page,
2997 unsigned long address)
3002 swp_entry_t swp_entry;
3003 int i, nr = HPAGE_PMD_NR;
3005 /* Skip pages which doesn't belong to the VMA */
3006 if (address < vma->vm_start) {
3007 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3010 address = vma->vm_start;
3013 pmd = mm_find_pmd(vma->vm_mm, address);
3016 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3017 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++) {
3018 if (!is_swap_pte(pte[i]))
3021 swp_entry = pte_to_swp_entry(pte[i]);
3022 if (!is_migration_entry(swp_entry))
3024 if (migration_entry_to_page(swp_entry) != page)
3028 page_add_anon_rmap(page, vma, address, false);
3030 entry = pte_mkold(mk_pte(page, vma->vm_page_prot));
3031 entry = pte_mkdirty(entry);
3032 if (is_write_migration_entry(swp_entry))
3033 entry = maybe_mkwrite(entry, vma);
3035 flush_dcache_page(page);
3036 set_pte_at(vma->vm_mm, address, pte + i, entry);
3038 /* No need to invalidate - it was non-present before */
3039 update_mmu_cache(vma, address, pte + i);
3041 pte_unmap_unlock(pte, ptl);
3044 static void unfreeze_page(struct anon_vma *anon_vma, struct page *page)
3046 struct anon_vma_chain *avc;
3047 pgoff_t pgoff = page_to_pgoff(page);
3049 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
3050 pgoff, pgoff + HPAGE_PMD_NR - 1) {
3051 unsigned long address = __vma_address(page, avc->vma);
3053 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3054 address, address + HPAGE_PMD_SIZE);
3055 unfreeze_page_vma(avc->vma, page, address);
3056 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3057 address, address + HPAGE_PMD_SIZE);
3061 static int __split_huge_page_tail(struct page *head, int tail,
3062 struct lruvec *lruvec, struct list_head *list)
3065 struct page *page_tail = head + tail;
3067 mapcount = atomic_read(&page_tail->_mapcount) + 1;
3068 VM_BUG_ON_PAGE(atomic_read(&page_tail->_count) != 0, page_tail);
3071 * tail_page->_count is zero and not changing from under us. But
3072 * get_page_unless_zero() may be running from under us on the
3073 * tail_page. If we used atomic_set() below instead of atomic_add(), we
3074 * would then run atomic_set() concurrently with
3075 * get_page_unless_zero(), and atomic_set() is implemented in C not
3076 * using locked ops. spin_unlock on x86 sometime uses locked ops
3077 * because of PPro errata 66, 92, so unless somebody can guarantee
3078 * atomic_set() here would be safe on all archs (and not only on x86),
3079 * it's safer to use atomic_add().
3081 atomic_add(mapcount + 1, &page_tail->_count);
3084 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3085 page_tail->flags |= (head->flags &
3086 ((1L << PG_referenced) |
3087 (1L << PG_swapbacked) |
3088 (1L << PG_mlocked) |
3089 (1L << PG_uptodate) |
3092 (1L << PG_unevictable)));
3093 page_tail->flags |= (1L << PG_dirty);
3096 * After clearing PageTail the gup refcount can be released.
3097 * Page flags also must be visible before we make the page non-compound.
3101 clear_compound_head(page_tail);
3103 if (page_is_young(head))
3104 set_page_young(page_tail);
3105 if (page_is_idle(head))
3106 set_page_idle(page_tail);
3108 /* ->mapping in first tail page is compound_mapcount */
3109 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3111 page_tail->mapping = head->mapping;
3113 page_tail->index = head->index + tail;
3114 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3115 lru_add_page_tail(head, page_tail, lruvec, list);
3120 static void __split_huge_page(struct page *page, struct list_head *list)
3122 struct page *head = compound_head(page);
3123 struct zone *zone = page_zone(head);
3124 struct lruvec *lruvec;
3125 int i, tail_mapcount;
3127 /* prevent PageLRU to go away from under us, and freeze lru stats */
3128 spin_lock_irq(&zone->lru_lock);
3129 lruvec = mem_cgroup_page_lruvec(head, zone);
3131 /* complete memcg works before add pages to LRU */
3132 mem_cgroup_split_huge_fixup(head);
3135 for (i = HPAGE_PMD_NR - 1; i >= 1; i--)
3136 tail_mapcount += __split_huge_page_tail(head, i, lruvec, list);
3137 atomic_sub(tail_mapcount, &head->_count);
3139 ClearPageCompound(head);
3140 spin_unlock_irq(&zone->lru_lock);
3142 unfreeze_page(page_anon_vma(head), head);
3144 for (i = 0; i < HPAGE_PMD_NR; i++) {
3145 struct page *subpage = head + i;
3146 if (subpage == page)
3148 unlock_page(subpage);
3151 * Subpages may be freed if there wasn't any mapping
3152 * like if add_to_swap() is running on a lru page that
3153 * had its mapping zapped. And freeing these pages
3154 * requires taking the lru_lock so we do the put_page
3155 * of the tail pages after the split is complete.
3161 int total_mapcount(struct page *page)
3165 VM_BUG_ON_PAGE(PageTail(page), page);
3167 if (likely(!PageCompound(page)))
3168 return atomic_read(&page->_mapcount) + 1;
3170 ret = compound_mapcount(page);
3173 for (i = 0; i < HPAGE_PMD_NR; i++)
3174 ret += atomic_read(&page[i]._mapcount) + 1;
3175 if (PageDoubleMap(page))
3176 ret -= HPAGE_PMD_NR;
3181 * This function splits huge page into normal pages. @page can point to any
3182 * subpage of huge page to split. Split doesn't change the position of @page.
3184 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3185 * The huge page must be locked.
3187 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3189 * Both head page and tail pages will inherit mapping, flags, and so on from
3192 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3193 * they are not mapped.
3195 * Returns 0 if the hugepage is split successfully.
3196 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3199 int split_huge_page_to_list(struct page *page, struct list_head *list)
3201 struct page *head = compound_head(page);
3202 struct anon_vma *anon_vma;
3203 int count, mapcount, ret;
3206 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3207 VM_BUG_ON_PAGE(!PageAnon(page), page);
3208 VM_BUG_ON_PAGE(!PageLocked(page), page);
3209 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3210 VM_BUG_ON_PAGE(!PageCompound(page), page);
3213 * The caller does not necessarily hold an mmap_sem that would prevent
3214 * the anon_vma disappearing so we first we take a reference to it
3215 * and then lock the anon_vma for write. This is similar to
3216 * page_lock_anon_vma_read except the write lock is taken to serialise
3217 * against parallel split or collapse operations.
3219 anon_vma = page_get_anon_vma(head);
3224 anon_vma_lock_write(anon_vma);
3227 * Racy check if we can split the page, before freeze_page() will
3230 if (total_mapcount(head) != page_count(head) - 1) {
3235 mlocked = PageMlocked(page);
3236 freeze_page(anon_vma, head);
3237 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3239 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3243 /* Prevent deferred_split_scan() touching ->_count */
3244 spin_lock(&split_queue_lock);
3245 count = page_count(head);
3246 mapcount = total_mapcount(head);
3247 if (mapcount == count - 1) {
3248 if (!list_empty(page_deferred_list(head))) {
3250 list_del(page_deferred_list(head));
3252 spin_unlock(&split_queue_lock);
3253 __split_huge_page(page, list);
3255 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount > count - 1) {
3256 spin_unlock(&split_queue_lock);
3257 pr_alert("total_mapcount: %u, page_count(): %u\n",
3260 dump_page(head, NULL);
3261 dump_page(page, "total_mapcount(head) > page_count(head) - 1");
3264 spin_unlock(&split_queue_lock);
3265 unfreeze_page(anon_vma, head);
3270 anon_vma_unlock_write(anon_vma);
3271 put_anon_vma(anon_vma);
3273 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3277 void free_transhuge_page(struct page *page)
3279 unsigned long flags;
3281 spin_lock_irqsave(&split_queue_lock, flags);
3282 if (!list_empty(page_deferred_list(page))) {
3284 list_del(page_deferred_list(page));
3286 spin_unlock_irqrestore(&split_queue_lock, flags);
3287 free_compound_page(page);
3290 void deferred_split_huge_page(struct page *page)
3292 unsigned long flags;
3294 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3296 spin_lock_irqsave(&split_queue_lock, flags);
3297 if (list_empty(page_deferred_list(page))) {
3298 list_add_tail(page_deferred_list(page), &split_queue);
3301 spin_unlock_irqrestore(&split_queue_lock, flags);
3304 static unsigned long deferred_split_count(struct shrinker *shrink,
3305 struct shrink_control *sc)
3308 * Split a page from split_queue will free up at least one page,
3309 * at most HPAGE_PMD_NR - 1. We don't track exact number.
3310 * Let's use HPAGE_PMD_NR / 2 as ballpark.
3312 return ACCESS_ONCE(split_queue_len) * HPAGE_PMD_NR / 2;
3315 static unsigned long deferred_split_scan(struct shrinker *shrink,
3316 struct shrink_control *sc)
3318 unsigned long flags;
3319 LIST_HEAD(list), *pos, *next;
3323 spin_lock_irqsave(&split_queue_lock, flags);
3324 list_splice_init(&split_queue, &list);
3326 /* Take pin on all head pages to avoid freeing them under us */
3327 list_for_each_safe(pos, next, &list) {
3328 page = list_entry((void *)pos, struct page, mapping);
3329 page = compound_head(page);
3330 /* race with put_compound_page() */
3331 if (!get_page_unless_zero(page)) {
3332 list_del_init(page_deferred_list(page));
3336 spin_unlock_irqrestore(&split_queue_lock, flags);
3338 list_for_each_safe(pos, next, &list) {
3339 page = list_entry((void *)pos, struct page, mapping);
3341 /* split_huge_page() removes page from list on success */
3342 if (!split_huge_page(page))
3348 spin_lock_irqsave(&split_queue_lock, flags);
3349 list_splice_tail(&list, &split_queue);
3350 spin_unlock_irqrestore(&split_queue_lock, flags);
3352 return split * HPAGE_PMD_NR / 2;
3355 static struct shrinker deferred_split_shrinker = {
3356 .count_objects = deferred_split_count,
3357 .scan_objects = deferred_split_scan,
3358 .seeks = DEFAULT_SEEKS,
3361 #ifdef CONFIG_DEBUG_FS
3362 static int split_huge_pages_set(void *data, u64 val)
3366 unsigned long pfn, max_zone_pfn;
3367 unsigned long total = 0, split = 0;
3372 for_each_populated_zone(zone) {
3373 max_zone_pfn = zone_end_pfn(zone);
3374 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3375 if (!pfn_valid(pfn))
3378 page = pfn_to_page(pfn);
3379 if (!get_page_unless_zero(page))
3382 if (zone != page_zone(page))
3385 if (!PageHead(page) || !PageAnon(page) ||
3391 if (!split_huge_page(page))
3399 pr_info("%lu of %lu THP split", split, total);
3403 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3406 static int __init split_huge_pages_debugfs(void)
3410 ret = debugfs_create_file("split_huge_pages", 0644, NULL, NULL,
3411 &split_huge_pages_fops);
3413 pr_warn("Failed to create split_huge_pages in debugfs");
3416 late_initcall(split_huge_pages_debugfs);