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/pfn_t.h>
25 #include <linux/mman.h>
26 #include <linux/memremap.h>
27 #include <linux/pagemap.h>
28 #include <linux/debugfs.h>
29 #include <linux/migrate.h>
30 #include <linux/hashtable.h>
31 #include <linux/userfaultfd_k.h>
32 #include <linux/page_idle.h>
35 #include <asm/pgalloc.h>
45 SCAN_NO_REFERENCED_PAGE,
59 SCAN_ALLOC_HUGE_PAGE_FAIL,
60 SCAN_CGROUP_CHARGE_FAIL
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/huge_memory.h>
67 * By default transparent hugepage support is disabled in order that avoid
68 * to risk increase the memory footprint of applications without a guaranteed
69 * benefit. When transparent hugepage support is enabled, is for all mappings,
70 * and khugepaged scans all mappings.
71 * Defrag is invoked by khugepaged hugepage allocations and by page faults
72 * for all hugepage allocations.
74 unsigned long transparent_hugepage_flags __read_mostly =
75 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
76 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
78 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
79 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
81 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
82 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
83 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
85 /* default scan 8*512 pte (or vmas) every 30 second */
86 static unsigned int khugepaged_pages_to_scan __read_mostly;
87 static unsigned int khugepaged_pages_collapsed;
88 static unsigned int khugepaged_full_scans;
89 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
90 /* during fragmentation poll the hugepage allocator once every minute */
91 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
92 static unsigned long khugepaged_sleep_expire;
93 static struct task_struct *khugepaged_thread __read_mostly;
94 static DEFINE_MUTEX(khugepaged_mutex);
95 static DEFINE_SPINLOCK(khugepaged_mm_lock);
96 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
98 * default collapse hugepages if there is at least one pte mapped like
99 * it would have happened if the vma was large enough during page
102 static unsigned int khugepaged_max_ptes_none __read_mostly;
104 static int khugepaged(void *none);
105 static int khugepaged_slab_init(void);
106 static void khugepaged_slab_exit(void);
108 #define MM_SLOTS_HASH_BITS 10
109 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
111 static struct kmem_cache *mm_slot_cache __read_mostly;
114 * struct mm_slot - hash lookup from mm to mm_slot
115 * @hash: hash collision list
116 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
117 * @mm: the mm that this information is valid for
120 struct hlist_node hash;
121 struct list_head mm_node;
122 struct mm_struct *mm;
126 * struct khugepaged_scan - cursor for scanning
127 * @mm_head: the head of the mm list to scan
128 * @mm_slot: the current mm_slot we are scanning
129 * @address: the next address inside that to be scanned
131 * There is only the one khugepaged_scan instance of this cursor structure.
133 struct khugepaged_scan {
134 struct list_head mm_head;
135 struct mm_slot *mm_slot;
136 unsigned long address;
138 static struct khugepaged_scan khugepaged_scan = {
139 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
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 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 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 triple_flag_store(struct kobject *kobj,
274 struct kobj_attribute *attr,
275 const char *buf, size_t count,
276 enum transparent_hugepage_flag enabled,
277 enum transparent_hugepage_flag deferred,
278 enum transparent_hugepage_flag req_madv)
280 if (!memcmp("defer", buf,
281 min(sizeof("defer")-1, count))) {
282 if (enabled == deferred)
284 clear_bit(enabled, &transparent_hugepage_flags);
285 clear_bit(req_madv, &transparent_hugepage_flags);
286 set_bit(deferred, &transparent_hugepage_flags);
287 } else if (!memcmp("always", buf,
288 min(sizeof("always")-1, count))) {
289 clear_bit(deferred, &transparent_hugepage_flags);
290 clear_bit(req_madv, &transparent_hugepage_flags);
291 set_bit(enabled, &transparent_hugepage_flags);
292 } else if (!memcmp("madvise", buf,
293 min(sizeof("madvise")-1, count))) {
294 clear_bit(enabled, &transparent_hugepage_flags);
295 clear_bit(deferred, &transparent_hugepage_flags);
296 set_bit(req_madv, &transparent_hugepage_flags);
297 } else if (!memcmp("never", buf,
298 min(sizeof("never")-1, count))) {
299 clear_bit(enabled, &transparent_hugepage_flags);
300 clear_bit(req_madv, &transparent_hugepage_flags);
301 clear_bit(deferred, &transparent_hugepage_flags);
308 static ssize_t enabled_show(struct kobject *kobj,
309 struct kobj_attribute *attr, char *buf)
311 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
312 return sprintf(buf, "[always] madvise never\n");
313 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
314 return sprintf(buf, "always [madvise] never\n");
316 return sprintf(buf, "always madvise [never]\n");
319 static ssize_t enabled_store(struct kobject *kobj,
320 struct kobj_attribute *attr,
321 const char *buf, size_t count)
325 ret = triple_flag_store(kobj, attr, buf, count,
326 TRANSPARENT_HUGEPAGE_FLAG,
327 TRANSPARENT_HUGEPAGE_FLAG,
328 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
333 mutex_lock(&khugepaged_mutex);
334 err = start_stop_khugepaged();
335 mutex_unlock(&khugepaged_mutex);
343 static struct kobj_attribute enabled_attr =
344 __ATTR(enabled, 0644, enabled_show, enabled_store);
346 static ssize_t single_flag_show(struct kobject *kobj,
347 struct kobj_attribute *attr, char *buf,
348 enum transparent_hugepage_flag flag)
350 return sprintf(buf, "%d\n",
351 !!test_bit(flag, &transparent_hugepage_flags));
354 static ssize_t single_flag_store(struct kobject *kobj,
355 struct kobj_attribute *attr,
356 const char *buf, size_t count,
357 enum transparent_hugepage_flag flag)
362 ret = kstrtoul(buf, 10, &value);
369 set_bit(flag, &transparent_hugepage_flags);
371 clear_bit(flag, &transparent_hugepage_flags);
377 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
378 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
379 * memory just to allocate one more hugepage.
381 static ssize_t defrag_show(struct kobject *kobj,
382 struct kobj_attribute *attr, char *buf)
384 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
385 return sprintf(buf, "[always] defer madvise never\n");
386 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
387 return sprintf(buf, "always [defer] madvise never\n");
388 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
389 return sprintf(buf, "always defer [madvise] never\n");
391 return sprintf(buf, "always defer madvise [never]\n");
394 static ssize_t defrag_store(struct kobject *kobj,
395 struct kobj_attribute *attr,
396 const char *buf, size_t count)
398 return triple_flag_store(kobj, attr, buf, count,
399 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
400 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
401 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
403 static struct kobj_attribute defrag_attr =
404 __ATTR(defrag, 0644, defrag_show, defrag_store);
406 static ssize_t use_zero_page_show(struct kobject *kobj,
407 struct kobj_attribute *attr, char *buf)
409 return single_flag_show(kobj, attr, buf,
410 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
412 static ssize_t use_zero_page_store(struct kobject *kobj,
413 struct kobj_attribute *attr, const char *buf, size_t count)
415 return single_flag_store(kobj, attr, buf, count,
416 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
418 static struct kobj_attribute use_zero_page_attr =
419 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
420 #ifdef CONFIG_DEBUG_VM
421 static ssize_t debug_cow_show(struct kobject *kobj,
422 struct kobj_attribute *attr, char *buf)
424 return single_flag_show(kobj, attr, buf,
425 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
427 static ssize_t debug_cow_store(struct kobject *kobj,
428 struct kobj_attribute *attr,
429 const char *buf, size_t count)
431 return single_flag_store(kobj, attr, buf, count,
432 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
434 static struct kobj_attribute debug_cow_attr =
435 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
436 #endif /* CONFIG_DEBUG_VM */
438 static struct attribute *hugepage_attr[] = {
441 &use_zero_page_attr.attr,
442 #ifdef CONFIG_DEBUG_VM
443 &debug_cow_attr.attr,
448 static struct attribute_group hugepage_attr_group = {
449 .attrs = hugepage_attr,
452 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
453 struct kobj_attribute *attr,
456 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
459 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
460 struct kobj_attribute *attr,
461 const char *buf, size_t count)
466 err = kstrtoul(buf, 10, &msecs);
467 if (err || msecs > UINT_MAX)
470 khugepaged_scan_sleep_millisecs = msecs;
471 khugepaged_sleep_expire = 0;
472 wake_up_interruptible(&khugepaged_wait);
476 static struct kobj_attribute scan_sleep_millisecs_attr =
477 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
478 scan_sleep_millisecs_store);
480 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
481 struct kobj_attribute *attr,
484 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
487 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
488 struct kobj_attribute *attr,
489 const char *buf, size_t count)
494 err = kstrtoul(buf, 10, &msecs);
495 if (err || msecs > UINT_MAX)
498 khugepaged_alloc_sleep_millisecs = msecs;
499 khugepaged_sleep_expire = 0;
500 wake_up_interruptible(&khugepaged_wait);
504 static struct kobj_attribute alloc_sleep_millisecs_attr =
505 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
506 alloc_sleep_millisecs_store);
508 static ssize_t pages_to_scan_show(struct kobject *kobj,
509 struct kobj_attribute *attr,
512 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
514 static ssize_t pages_to_scan_store(struct kobject *kobj,
515 struct kobj_attribute *attr,
516 const char *buf, size_t count)
521 err = kstrtoul(buf, 10, &pages);
522 if (err || !pages || pages > UINT_MAX)
525 khugepaged_pages_to_scan = pages;
529 static struct kobj_attribute pages_to_scan_attr =
530 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
531 pages_to_scan_store);
533 static ssize_t pages_collapsed_show(struct kobject *kobj,
534 struct kobj_attribute *attr,
537 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
539 static struct kobj_attribute pages_collapsed_attr =
540 __ATTR_RO(pages_collapsed);
542 static ssize_t full_scans_show(struct kobject *kobj,
543 struct kobj_attribute *attr,
546 return sprintf(buf, "%u\n", khugepaged_full_scans);
548 static struct kobj_attribute full_scans_attr =
549 __ATTR_RO(full_scans);
551 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
552 struct kobj_attribute *attr, char *buf)
554 return single_flag_show(kobj, attr, buf,
555 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
557 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
558 struct kobj_attribute *attr,
559 const char *buf, size_t count)
561 return single_flag_store(kobj, attr, buf, count,
562 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
564 static struct kobj_attribute khugepaged_defrag_attr =
565 __ATTR(defrag, 0644, khugepaged_defrag_show,
566 khugepaged_defrag_store);
569 * max_ptes_none controls if khugepaged should collapse hugepages over
570 * any unmapped ptes in turn potentially increasing the memory
571 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
572 * reduce the available free memory in the system as it
573 * runs. Increasing max_ptes_none will instead potentially reduce the
574 * free memory in the system during the khugepaged scan.
576 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
577 struct kobj_attribute *attr,
580 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
582 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
583 struct kobj_attribute *attr,
584 const char *buf, size_t count)
587 unsigned long max_ptes_none;
589 err = kstrtoul(buf, 10, &max_ptes_none);
590 if (err || max_ptes_none > HPAGE_PMD_NR-1)
593 khugepaged_max_ptes_none = max_ptes_none;
597 static struct kobj_attribute khugepaged_max_ptes_none_attr =
598 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
599 khugepaged_max_ptes_none_store);
601 static struct attribute *khugepaged_attr[] = {
602 &khugepaged_defrag_attr.attr,
603 &khugepaged_max_ptes_none_attr.attr,
604 &pages_to_scan_attr.attr,
605 &pages_collapsed_attr.attr,
606 &full_scans_attr.attr,
607 &scan_sleep_millisecs_attr.attr,
608 &alloc_sleep_millisecs_attr.attr,
612 static struct attribute_group khugepaged_attr_group = {
613 .attrs = khugepaged_attr,
614 .name = "khugepaged",
617 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
621 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
622 if (unlikely(!*hugepage_kobj)) {
623 pr_err("failed to create transparent hugepage kobject\n");
627 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
629 pr_err("failed to register transparent hugepage group\n");
633 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
635 pr_err("failed to register transparent hugepage group\n");
636 goto remove_hp_group;
642 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
644 kobject_put(*hugepage_kobj);
648 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
650 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
651 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
652 kobject_put(hugepage_kobj);
655 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
660 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
663 #endif /* CONFIG_SYSFS */
665 static int __init hugepage_init(void)
668 struct kobject *hugepage_kobj;
670 if (!has_transparent_hugepage()) {
671 transparent_hugepage_flags = 0;
675 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
676 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
678 * hugepages can't be allocated by the buddy allocator
680 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
682 * we use page->mapping and page->index in second tail page
683 * as list_head: assuming THP order >= 2
685 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
687 err = hugepage_init_sysfs(&hugepage_kobj);
691 err = khugepaged_slab_init();
695 err = register_shrinker(&huge_zero_page_shrinker);
697 goto err_hzp_shrinker;
698 err = register_shrinker(&deferred_split_shrinker);
700 goto err_split_shrinker;
703 * By default disable transparent hugepages on smaller systems,
704 * where the extra memory used could hurt more than TLB overhead
705 * is likely to save. The admin can still enable it through /sys.
707 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
708 transparent_hugepage_flags = 0;
712 err = start_stop_khugepaged();
718 unregister_shrinker(&deferred_split_shrinker);
720 unregister_shrinker(&huge_zero_page_shrinker);
722 khugepaged_slab_exit();
724 hugepage_exit_sysfs(hugepage_kobj);
728 subsys_initcall(hugepage_init);
730 static int __init setup_transparent_hugepage(char *str)
735 if (!strcmp(str, "always")) {
736 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
737 &transparent_hugepage_flags);
738 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
739 &transparent_hugepage_flags);
741 } else if (!strcmp(str, "madvise")) {
742 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
743 &transparent_hugepage_flags);
744 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
745 &transparent_hugepage_flags);
747 } else if (!strcmp(str, "never")) {
748 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
749 &transparent_hugepage_flags);
750 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
751 &transparent_hugepage_flags);
756 pr_warn("transparent_hugepage= cannot parse, ignored\n");
759 __setup("transparent_hugepage=", setup_transparent_hugepage);
761 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
763 if (likely(vma->vm_flags & VM_WRITE))
764 pmd = pmd_mkwrite(pmd);
768 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
770 return pmd_mkhuge(mk_pmd(page, prot));
773 static inline struct list_head *page_deferred_list(struct page *page)
776 * ->lru in the tail pages is occupied by compound_head.
777 * Let's use ->mapping + ->index in the second tail page as list_head.
779 return (struct list_head *)&page[2].mapping;
782 void prep_transhuge_page(struct page *page)
785 * we use page->mapping and page->indexlru in second tail page
786 * as list_head: assuming THP order >= 2
789 INIT_LIST_HEAD(page_deferred_list(page));
790 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
793 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
794 struct vm_area_struct *vma,
795 unsigned long address, pmd_t *pmd,
796 struct page *page, gfp_t gfp,
799 struct mem_cgroup *memcg;
802 unsigned long haddr = address & HPAGE_PMD_MASK;
804 VM_BUG_ON_PAGE(!PageCompound(page), page);
806 if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) {
808 count_vm_event(THP_FAULT_FALLBACK);
809 return VM_FAULT_FALLBACK;
812 pgtable = pte_alloc_one(mm, haddr);
813 if (unlikely(!pgtable)) {
814 mem_cgroup_cancel_charge(page, memcg, true);
819 clear_huge_page(page, haddr, HPAGE_PMD_NR);
821 * The memory barrier inside __SetPageUptodate makes sure that
822 * clear_huge_page writes become visible before the set_pmd_at()
825 __SetPageUptodate(page);
827 ptl = pmd_lock(mm, pmd);
828 if (unlikely(!pmd_none(*pmd))) {
830 mem_cgroup_cancel_charge(page, memcg, true);
832 pte_free(mm, pgtable);
836 /* Deliver the page fault to userland */
837 if (userfaultfd_missing(vma)) {
841 mem_cgroup_cancel_charge(page, memcg, true);
843 pte_free(mm, pgtable);
844 ret = handle_userfault(vma, address, flags,
846 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
850 entry = mk_huge_pmd(page, vma->vm_page_prot);
851 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
852 page_add_new_anon_rmap(page, vma, haddr, true);
853 mem_cgroup_commit_charge(page, memcg, false, true);
854 lru_cache_add_active_or_unevictable(page, vma);
855 pgtable_trans_huge_deposit(mm, pmd, pgtable);
856 set_pmd_at(mm, haddr, pmd, entry);
857 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
858 atomic_long_inc(&mm->nr_ptes);
860 count_vm_event(THP_FAULT_ALLOC);
867 * If THP is set to always then directly reclaim/compact as necessary
868 * If set to defer then do no reclaim and defer to khugepaged
869 * If set to madvise and the VMA is flagged then directly reclaim/compact
871 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
873 gfp_t reclaim_flags = 0;
875 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags) &&
876 (vma->vm_flags & VM_HUGEPAGE))
877 reclaim_flags = __GFP_DIRECT_RECLAIM;
878 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
879 reclaim_flags = __GFP_KSWAPD_RECLAIM;
880 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
881 reclaim_flags = __GFP_DIRECT_RECLAIM;
883 return GFP_TRANSHUGE | reclaim_flags;
886 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
887 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
889 return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0);
892 /* Caller must hold page table lock. */
893 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
894 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
895 struct page *zero_page)
900 entry = mk_pmd(zero_page, vma->vm_page_prot);
901 entry = pmd_mkhuge(entry);
903 pgtable_trans_huge_deposit(mm, pmd, pgtable);
904 set_pmd_at(mm, haddr, pmd, entry);
905 atomic_long_inc(&mm->nr_ptes);
909 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
910 unsigned long address, pmd_t *pmd,
915 unsigned long haddr = address & HPAGE_PMD_MASK;
917 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
918 return VM_FAULT_FALLBACK;
919 if (unlikely(anon_vma_prepare(vma)))
921 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
923 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
924 transparent_hugepage_use_zero_page()) {
927 struct page *zero_page;
930 pgtable = pte_alloc_one(mm, haddr);
931 if (unlikely(!pgtable))
933 zero_page = get_huge_zero_page();
934 if (unlikely(!zero_page)) {
935 pte_free(mm, pgtable);
936 count_vm_event(THP_FAULT_FALLBACK);
937 return VM_FAULT_FALLBACK;
939 ptl = pmd_lock(mm, pmd);
942 if (pmd_none(*pmd)) {
943 if (userfaultfd_missing(vma)) {
945 ret = handle_userfault(vma, address, flags,
947 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
949 set_huge_zero_page(pgtable, mm, vma,
958 pte_free(mm, pgtable);
959 put_huge_zero_page();
963 gfp = alloc_hugepage_direct_gfpmask(vma);
964 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
965 if (unlikely(!page)) {
966 count_vm_event(THP_FAULT_FALLBACK);
967 return VM_FAULT_FALLBACK;
969 prep_transhuge_page(page);
970 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
974 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
975 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
977 struct mm_struct *mm = vma->vm_mm;
981 ptl = pmd_lock(mm, pmd);
982 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
983 if (pfn_t_devmap(pfn))
984 entry = pmd_mkdevmap(entry);
986 entry = pmd_mkyoung(pmd_mkdirty(entry));
987 entry = maybe_pmd_mkwrite(entry, vma);
989 set_pmd_at(mm, addr, pmd, entry);
990 update_mmu_cache_pmd(vma, addr, pmd);
994 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
995 pmd_t *pmd, pfn_t pfn, bool write)
997 pgprot_t pgprot = vma->vm_page_prot;
999 * If we had pmd_special, we could avoid all these restrictions,
1000 * but we need to be consistent with PTEs and architectures that
1001 * can't support a 'special' bit.
1003 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1004 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1005 (VM_PFNMAP|VM_MIXEDMAP));
1006 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1007 BUG_ON(!pfn_t_devmap(pfn));
1009 if (addr < vma->vm_start || addr >= vma->vm_end)
1010 return VM_FAULT_SIGBUS;
1011 if (track_pfn_insert(vma, &pgprot, pfn))
1012 return VM_FAULT_SIGBUS;
1013 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
1014 return VM_FAULT_NOPAGE;
1017 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1023 * We should set the dirty bit only for FOLL_WRITE but for now
1024 * the dirty bit in the pmd is meaningless. And if the dirty
1025 * bit will become meaningful and we'll only set it with
1026 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
1027 * set the young bit, instead of the current set_pmd_at.
1029 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1030 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1032 update_mmu_cache_pmd(vma, addr, pmd);
1035 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1036 pmd_t *pmd, int flags)
1038 unsigned long pfn = pmd_pfn(*pmd);
1039 struct mm_struct *mm = vma->vm_mm;
1040 struct dev_pagemap *pgmap;
1043 assert_spin_locked(pmd_lockptr(mm, pmd));
1045 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1048 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1053 if (flags & FOLL_TOUCH)
1054 touch_pmd(vma, addr, pmd);
1057 * device mapped pages can only be returned if the
1058 * caller will manage the page reference count.
1060 if (!(flags & FOLL_GET))
1061 return ERR_PTR(-EEXIST);
1063 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1064 pgmap = get_dev_pagemap(pfn, NULL);
1066 return ERR_PTR(-EFAULT);
1067 page = pfn_to_page(pfn);
1069 put_dev_pagemap(pgmap);
1074 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1075 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1076 struct vm_area_struct *vma)
1078 spinlock_t *dst_ptl, *src_ptl;
1079 struct page *src_page;
1081 pgtable_t pgtable = NULL;
1084 if (!vma_is_dax(vma)) {
1086 pgtable = pte_alloc_one(dst_mm, addr);
1087 if (unlikely(!pgtable))
1091 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1092 src_ptl = pmd_lockptr(src_mm, src_pmd);
1093 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1097 if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
1098 pte_free(dst_mm, pgtable);
1102 * When page table lock is held, the huge zero pmd should not be
1103 * under splitting since we don't split the page itself, only pmd to
1106 if (is_huge_zero_pmd(pmd)) {
1107 struct page *zero_page;
1109 * get_huge_zero_page() will never allocate a new page here,
1110 * since we already have a zero page to copy. It just takes a
1113 zero_page = get_huge_zero_page();
1114 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1120 if (!vma_is_dax(vma)) {
1121 /* thp accounting separate from pmd_devmap accounting */
1122 src_page = pmd_page(pmd);
1123 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1125 page_dup_rmap(src_page, true);
1126 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1127 atomic_long_inc(&dst_mm->nr_ptes);
1128 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1131 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1132 pmd = pmd_mkold(pmd_wrprotect(pmd));
1133 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1137 spin_unlock(src_ptl);
1138 spin_unlock(dst_ptl);
1143 void huge_pmd_set_accessed(struct mm_struct *mm,
1144 struct vm_area_struct *vma,
1145 unsigned long address,
1146 pmd_t *pmd, pmd_t orig_pmd,
1151 unsigned long haddr;
1153 ptl = pmd_lock(mm, pmd);
1154 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1157 entry = pmd_mkyoung(orig_pmd);
1158 haddr = address & HPAGE_PMD_MASK;
1159 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1160 update_mmu_cache_pmd(vma, address, pmd);
1166 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1167 struct vm_area_struct *vma,
1168 unsigned long address,
1169 pmd_t *pmd, pmd_t orig_pmd,
1171 unsigned long haddr)
1173 struct mem_cgroup *memcg;
1178 struct page **pages;
1179 unsigned long mmun_start; /* For mmu_notifiers */
1180 unsigned long mmun_end; /* For mmu_notifiers */
1182 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1184 if (unlikely(!pages)) {
1185 ret |= VM_FAULT_OOM;
1189 for (i = 0; i < HPAGE_PMD_NR; i++) {
1190 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1192 vma, address, page_to_nid(page));
1193 if (unlikely(!pages[i] ||
1194 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1199 memcg = (void *)page_private(pages[i]);
1200 set_page_private(pages[i], 0);
1201 mem_cgroup_cancel_charge(pages[i], memcg,
1206 ret |= VM_FAULT_OOM;
1209 set_page_private(pages[i], (unsigned long)memcg);
1212 for (i = 0; i < HPAGE_PMD_NR; i++) {
1213 copy_user_highpage(pages[i], page + i,
1214 haddr + PAGE_SIZE * i, vma);
1215 __SetPageUptodate(pages[i]);
1220 mmun_end = haddr + HPAGE_PMD_SIZE;
1221 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1223 ptl = pmd_lock(mm, pmd);
1224 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1225 goto out_free_pages;
1226 VM_BUG_ON_PAGE(!PageHead(page), page);
1228 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1229 /* leave pmd empty until pte is filled */
1231 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1232 pmd_populate(mm, &_pmd, pgtable);
1234 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1236 entry = mk_pte(pages[i], vma->vm_page_prot);
1237 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1238 memcg = (void *)page_private(pages[i]);
1239 set_page_private(pages[i], 0);
1240 page_add_new_anon_rmap(pages[i], vma, haddr, false);
1241 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1242 lru_cache_add_active_or_unevictable(pages[i], vma);
1243 pte = pte_offset_map(&_pmd, haddr);
1244 VM_BUG_ON(!pte_none(*pte));
1245 set_pte_at(mm, haddr, pte, entry);
1250 smp_wmb(); /* make pte visible before pmd */
1251 pmd_populate(mm, pmd, pgtable);
1252 page_remove_rmap(page, true);
1255 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1257 ret |= VM_FAULT_WRITE;
1265 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1266 for (i = 0; i < HPAGE_PMD_NR; i++) {
1267 memcg = (void *)page_private(pages[i]);
1268 set_page_private(pages[i], 0);
1269 mem_cgroup_cancel_charge(pages[i], memcg, false);
1276 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1277 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1281 struct page *page = NULL, *new_page;
1282 struct mem_cgroup *memcg;
1283 unsigned long haddr;
1284 unsigned long mmun_start; /* For mmu_notifiers */
1285 unsigned long mmun_end; /* For mmu_notifiers */
1286 gfp_t huge_gfp; /* for allocation and charge */
1288 ptl = pmd_lockptr(mm, pmd);
1289 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1290 haddr = address & HPAGE_PMD_MASK;
1291 if (is_huge_zero_pmd(orig_pmd))
1294 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1297 page = pmd_page(orig_pmd);
1298 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1300 * We can only reuse the page if nobody else maps the huge page or it's
1303 if (page_trans_huge_mapcount(page, NULL) == 1) {
1305 entry = pmd_mkyoung(orig_pmd);
1306 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1307 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1308 update_mmu_cache_pmd(vma, address, pmd);
1309 ret |= VM_FAULT_WRITE;
1315 if (transparent_hugepage_enabled(vma) &&
1316 !transparent_hugepage_debug_cow()) {
1317 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1318 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1322 if (likely(new_page)) {
1323 prep_transhuge_page(new_page);
1326 split_huge_pmd(vma, pmd, address);
1327 ret |= VM_FAULT_FALLBACK;
1329 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1330 pmd, orig_pmd, page, haddr);
1331 if (ret & VM_FAULT_OOM) {
1332 split_huge_pmd(vma, pmd, address);
1333 ret |= VM_FAULT_FALLBACK;
1337 count_vm_event(THP_FAULT_FALLBACK);
1341 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg,
1345 split_huge_pmd(vma, pmd, address);
1348 split_huge_pmd(vma, pmd, address);
1349 ret |= VM_FAULT_FALLBACK;
1350 count_vm_event(THP_FAULT_FALLBACK);
1354 count_vm_event(THP_FAULT_ALLOC);
1357 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1359 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1360 __SetPageUptodate(new_page);
1363 mmun_end = haddr + HPAGE_PMD_SIZE;
1364 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1369 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1371 mem_cgroup_cancel_charge(new_page, memcg, true);
1376 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1377 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1378 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1379 page_add_new_anon_rmap(new_page, vma, haddr, true);
1380 mem_cgroup_commit_charge(new_page, memcg, false, true);
1381 lru_cache_add_active_or_unevictable(new_page, vma);
1382 set_pmd_at(mm, haddr, pmd, entry);
1383 update_mmu_cache_pmd(vma, address, pmd);
1385 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1386 put_huge_zero_page();
1388 VM_BUG_ON_PAGE(!PageHead(page), page);
1389 page_remove_rmap(page, true);
1392 ret |= VM_FAULT_WRITE;
1396 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1404 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1409 struct mm_struct *mm = vma->vm_mm;
1410 struct page *page = NULL;
1412 assert_spin_locked(pmd_lockptr(mm, pmd));
1414 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1417 /* Avoid dumping huge zero page */
1418 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1419 return ERR_PTR(-EFAULT);
1421 /* Full NUMA hinting faults to serialise migration in fault paths */
1422 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1425 page = pmd_page(*pmd);
1426 VM_BUG_ON_PAGE(!PageHead(page), page);
1427 if (flags & FOLL_TOUCH)
1428 touch_pmd(vma, addr, pmd);
1429 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1431 * We don't mlock() pte-mapped THPs. This way we can avoid
1432 * leaking mlocked pages into non-VM_LOCKED VMAs.
1434 * In most cases the pmd is the only mapping of the page as we
1435 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1436 * writable private mappings in populate_vma_page_range().
1438 * The only scenario when we have the page shared here is if we
1439 * mlocking read-only mapping shared over fork(). We skip
1440 * mlocking such pages.
1442 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) &&
1443 page->mapping && trylock_page(page)) {
1446 mlock_vma_page(page);
1450 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1451 VM_BUG_ON_PAGE(!PageCompound(page), page);
1452 if (flags & FOLL_GET)
1459 /* NUMA hinting page fault entry point for trans huge pmds */
1460 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1461 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1464 struct anon_vma *anon_vma = NULL;
1466 unsigned long haddr = addr & HPAGE_PMD_MASK;
1467 int page_nid = -1, this_nid = numa_node_id();
1468 int target_nid, last_cpupid = -1;
1470 bool migrated = false;
1474 /* A PROT_NONE fault should not end up here */
1475 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1477 ptl = pmd_lock(mm, pmdp);
1478 if (unlikely(!pmd_same(pmd, *pmdp)))
1482 * If there are potential migrations, wait for completion and retry
1483 * without disrupting NUMA hinting information. Do not relock and
1484 * check_same as the page may no longer be mapped.
1486 if (unlikely(pmd_trans_migrating(*pmdp))) {
1487 page = pmd_page(*pmdp);
1489 wait_on_page_locked(page);
1493 page = pmd_page(pmd);
1494 BUG_ON(is_huge_zero_page(page));
1495 page_nid = page_to_nid(page);
1496 last_cpupid = page_cpupid_last(page);
1497 count_vm_numa_event(NUMA_HINT_FAULTS);
1498 if (page_nid == this_nid) {
1499 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1500 flags |= TNF_FAULT_LOCAL;
1503 /* See similar comment in do_numa_page for explanation */
1504 if (!(vma->vm_flags & VM_WRITE))
1505 flags |= TNF_NO_GROUP;
1508 * Acquire the page lock to serialise THP migrations but avoid dropping
1509 * page_table_lock if at all possible
1511 page_locked = trylock_page(page);
1512 target_nid = mpol_misplaced(page, vma, haddr);
1513 if (target_nid == -1) {
1514 /* If the page was locked, there are no parallel migrations */
1519 /* Migration could have started since the pmd_trans_migrating check */
1522 wait_on_page_locked(page);
1528 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1529 * to serialises splits
1533 anon_vma = page_lock_anon_vma_read(page);
1535 /* Confirm the PMD did not change while page_table_lock was released */
1537 if (unlikely(!pmd_same(pmd, *pmdp))) {
1544 /* Bail if we fail to protect against THP splits for any reason */
1545 if (unlikely(!anon_vma)) {
1552 * Migrate the THP to the requested node, returns with page unlocked
1553 * and access rights restored.
1556 migrated = migrate_misplaced_transhuge_page(mm, vma,
1557 pmdp, pmd, addr, page, target_nid);
1559 flags |= TNF_MIGRATED;
1560 page_nid = target_nid;
1562 flags |= TNF_MIGRATE_FAIL;
1566 BUG_ON(!PageLocked(page));
1567 was_writable = pmd_write(pmd);
1568 pmd = pmd_modify(pmd, vma->vm_page_prot);
1569 pmd = pmd_mkyoung(pmd);
1571 pmd = pmd_mkwrite(pmd);
1572 set_pmd_at(mm, haddr, pmdp, pmd);
1573 update_mmu_cache_pmd(vma, addr, pmdp);
1580 page_unlock_anon_vma_read(anon_vma);
1583 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1588 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1589 pmd_t *pmd, unsigned long addr, unsigned long next)
1595 struct mm_struct *mm = tlb->mm;
1598 ptl = pmd_trans_huge_lock(pmd, vma);
1603 if (is_huge_zero_pmd(orig_pmd)) {
1608 page = pmd_page(orig_pmd);
1610 * If other processes are mapping this page, we couldn't discard
1611 * the page unless they all do MADV_FREE so let's skip the page.
1613 if (page_mapcount(page) != 1)
1616 if (!trylock_page(page))
1620 * If user want to discard part-pages of THP, split it so MADV_FREE
1621 * will deactivate only them.
1623 if (next - addr != HPAGE_PMD_SIZE) {
1626 if (split_huge_page(page)) {
1637 if (PageDirty(page))
1638 ClearPageDirty(page);
1641 if (PageActive(page))
1642 deactivate_page(page);
1644 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1645 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1647 orig_pmd = pmd_mkold(orig_pmd);
1648 orig_pmd = pmd_mkclean(orig_pmd);
1650 set_pmd_at(mm, addr, pmd, orig_pmd);
1651 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1660 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1661 pmd_t *pmd, unsigned long addr)
1666 ptl = __pmd_trans_huge_lock(pmd, vma);
1670 * For architectures like ppc64 we look at deposited pgtable
1671 * when calling pmdp_huge_get_and_clear. So do the
1672 * pgtable_trans_huge_withdraw after finishing pmdp related
1675 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1677 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1678 if (vma_is_dax(vma)) {
1680 if (is_huge_zero_pmd(orig_pmd))
1681 tlb_remove_page(tlb, pmd_page(orig_pmd));
1682 } else if (is_huge_zero_pmd(orig_pmd)) {
1683 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1684 atomic_long_dec(&tlb->mm->nr_ptes);
1686 tlb_remove_page(tlb, pmd_page(orig_pmd));
1688 struct page *page = pmd_page(orig_pmd);
1689 page_remove_rmap(page, true);
1690 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1691 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1692 VM_BUG_ON_PAGE(!PageHead(page), page);
1693 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1694 atomic_long_dec(&tlb->mm->nr_ptes);
1696 tlb_remove_page(tlb, page);
1701 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1702 unsigned long new_addr, unsigned long old_end,
1703 pmd_t *old_pmd, pmd_t *new_pmd)
1705 spinlock_t *old_ptl, *new_ptl;
1707 struct mm_struct *mm = vma->vm_mm;
1709 if ((old_addr & ~HPAGE_PMD_MASK) ||
1710 (new_addr & ~HPAGE_PMD_MASK) ||
1711 old_end - old_addr < HPAGE_PMD_SIZE)
1715 * The destination pmd shouldn't be established, free_pgtables()
1716 * should have release it.
1718 if (WARN_ON(!pmd_none(*new_pmd))) {
1719 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1724 * We don't have to worry about the ordering of src and dst
1725 * ptlocks because exclusive mmap_sem prevents deadlock.
1727 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1729 new_ptl = pmd_lockptr(mm, new_pmd);
1730 if (new_ptl != old_ptl)
1731 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1732 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1733 VM_BUG_ON(!pmd_none(*new_pmd));
1735 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1736 vma_is_anonymous(vma)) {
1738 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1739 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1741 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1742 if (new_ptl != old_ptl)
1743 spin_unlock(new_ptl);
1744 spin_unlock(old_ptl);
1752 * - 0 if PMD could not be locked
1753 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1754 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1756 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1757 unsigned long addr, pgprot_t newprot, int prot_numa)
1759 struct mm_struct *mm = vma->vm_mm;
1763 ptl = __pmd_trans_huge_lock(pmd, vma);
1766 bool preserve_write = prot_numa && pmd_write(*pmd);
1770 * Avoid trapping faults against the zero page. The read-only
1771 * data is likely to be read-cached on the local CPU and
1772 * local/remote hits to the zero page are not interesting.
1774 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1779 if (!prot_numa || !pmd_protnone(*pmd)) {
1780 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1781 entry = pmd_modify(entry, newprot);
1783 entry = pmd_mkwrite(entry);
1785 set_pmd_at(mm, addr, pmd, entry);
1786 BUG_ON(!preserve_write && pmd_write(entry));
1795 * Returns true if a given pmd maps a thp, false otherwise.
1797 * Note that if it returns true, this routine returns without unlocking page
1798 * table lock. So callers must unlock it.
1800 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1803 ptl = pmd_lock(vma->vm_mm, pmd);
1804 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1810 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1812 int hugepage_madvise(struct vm_area_struct *vma,
1813 unsigned long *vm_flags, int advice)
1819 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1820 * can't handle this properly after s390_enable_sie, so we simply
1821 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1823 if (mm_has_pgste(vma->vm_mm))
1827 * Be somewhat over-protective like KSM for now!
1829 if (*vm_flags & VM_NO_THP)
1831 *vm_flags &= ~VM_NOHUGEPAGE;
1832 *vm_flags |= VM_HUGEPAGE;
1834 * If the vma become good for khugepaged to scan,
1835 * register it here without waiting a page fault that
1836 * may not happen any time soon.
1838 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1841 case MADV_NOHUGEPAGE:
1843 * Be somewhat over-protective like KSM for now!
1845 if (*vm_flags & VM_NO_THP)
1847 *vm_flags &= ~VM_HUGEPAGE;
1848 *vm_flags |= VM_NOHUGEPAGE;
1850 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1851 * this vma even if we leave the mm registered in khugepaged if
1852 * it got registered before VM_NOHUGEPAGE was set.
1860 static int __init khugepaged_slab_init(void)
1862 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1863 sizeof(struct mm_slot),
1864 __alignof__(struct mm_slot), 0, NULL);
1871 static void __init khugepaged_slab_exit(void)
1873 kmem_cache_destroy(mm_slot_cache);
1876 static inline struct mm_slot *alloc_mm_slot(void)
1878 if (!mm_slot_cache) /* initialization failed */
1880 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1883 static inline void free_mm_slot(struct mm_slot *mm_slot)
1885 kmem_cache_free(mm_slot_cache, mm_slot);
1888 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1890 struct mm_slot *mm_slot;
1892 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1893 if (mm == mm_slot->mm)
1899 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1900 struct mm_slot *mm_slot)
1903 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1906 static inline int khugepaged_test_exit(struct mm_struct *mm)
1908 return atomic_read(&mm->mm_users) == 0;
1911 int __khugepaged_enter(struct mm_struct *mm)
1913 struct mm_slot *mm_slot;
1916 mm_slot = alloc_mm_slot();
1920 /* __khugepaged_exit() must not run from under us */
1921 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1922 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1923 free_mm_slot(mm_slot);
1927 spin_lock(&khugepaged_mm_lock);
1928 insert_to_mm_slots_hash(mm, mm_slot);
1930 * Insert just behind the scanning cursor, to let the area settle
1933 wakeup = list_empty(&khugepaged_scan.mm_head);
1934 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1935 spin_unlock(&khugepaged_mm_lock);
1937 atomic_inc(&mm->mm_count);
1939 wake_up_interruptible(&khugepaged_wait);
1944 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1945 unsigned long vm_flags)
1947 unsigned long hstart, hend;
1950 * Not yet faulted in so we will register later in the
1951 * page fault if needed.
1954 if (vma->vm_ops || (vm_flags & VM_NO_THP))
1955 /* khugepaged not yet working on file or special mappings */
1957 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1958 hend = vma->vm_end & HPAGE_PMD_MASK;
1960 return khugepaged_enter(vma, vm_flags);
1964 void __khugepaged_exit(struct mm_struct *mm)
1966 struct mm_slot *mm_slot;
1969 spin_lock(&khugepaged_mm_lock);
1970 mm_slot = get_mm_slot(mm);
1971 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1972 hash_del(&mm_slot->hash);
1973 list_del(&mm_slot->mm_node);
1976 spin_unlock(&khugepaged_mm_lock);
1979 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1980 free_mm_slot(mm_slot);
1982 } else if (mm_slot) {
1984 * This is required to serialize against
1985 * khugepaged_test_exit() (which is guaranteed to run
1986 * under mmap sem read mode). Stop here (after we
1987 * return all pagetables will be destroyed) until
1988 * khugepaged has finished working on the pagetables
1989 * under the mmap_sem.
1991 down_write(&mm->mmap_sem);
1992 up_write(&mm->mmap_sem);
1996 static void release_pte_page(struct page *page)
1998 /* 0 stands for page_is_file_cache(page) == false */
1999 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2001 putback_lru_page(page);
2004 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2006 while (--_pte >= pte) {
2007 pte_t pteval = *_pte;
2008 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2009 release_pte_page(pte_page(pteval));
2013 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2014 unsigned long address,
2017 struct page *page = NULL;
2019 int none_or_zero = 0, result = 0;
2020 bool referenced = false, writable = false;
2022 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2023 _pte++, address += PAGE_SIZE) {
2024 pte_t pteval = *_pte;
2025 if (pte_none(pteval) || (pte_present(pteval) &&
2026 is_zero_pfn(pte_pfn(pteval)))) {
2027 if (!userfaultfd_armed(vma) &&
2028 ++none_or_zero <= khugepaged_max_ptes_none) {
2031 result = SCAN_EXCEED_NONE_PTE;
2035 if (!pte_present(pteval)) {
2036 result = SCAN_PTE_NON_PRESENT;
2039 page = vm_normal_page(vma, address, pteval);
2040 if (unlikely(!page)) {
2041 result = SCAN_PAGE_NULL;
2045 VM_BUG_ON_PAGE(PageCompound(page), page);
2046 VM_BUG_ON_PAGE(!PageAnon(page), page);
2047 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2050 * We can do it before isolate_lru_page because the
2051 * page can't be freed from under us. NOTE: PG_lock
2052 * is needed to serialize against split_huge_page
2053 * when invoked from the VM.
2055 if (!trylock_page(page)) {
2056 result = SCAN_PAGE_LOCK;
2061 * cannot use mapcount: can't collapse if there's a gup pin.
2062 * The page must only be referenced by the scanned process
2063 * and page swap cache.
2065 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2067 result = SCAN_PAGE_COUNT;
2070 if (pte_write(pteval)) {
2073 if (PageSwapCache(page) &&
2074 !reuse_swap_page(page, NULL)) {
2076 result = SCAN_SWAP_CACHE_PAGE;
2080 * Page is not in the swap cache. It can be collapsed
2086 * Isolate the page to avoid collapsing an hugepage
2087 * currently in use by the VM.
2089 if (isolate_lru_page(page)) {
2091 result = SCAN_DEL_PAGE_LRU;
2094 /* 0 stands for page_is_file_cache(page) == false */
2095 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2096 VM_BUG_ON_PAGE(!PageLocked(page), page);
2097 VM_BUG_ON_PAGE(PageLRU(page), page);
2099 /* If there is no mapped pte young don't collapse the page */
2100 if (pte_young(pteval) ||
2101 page_is_young(page) || PageReferenced(page) ||
2102 mmu_notifier_test_young(vma->vm_mm, address))
2105 if (likely(writable)) {
2106 if (likely(referenced)) {
2107 result = SCAN_SUCCEED;
2108 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2109 referenced, writable, result);
2113 result = SCAN_PAGE_RO;
2117 release_pte_pages(pte, _pte);
2118 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2119 referenced, writable, result);
2123 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2124 struct vm_area_struct *vma,
2125 unsigned long address,
2129 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2130 pte_t pteval = *_pte;
2131 struct page *src_page;
2133 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2134 clear_user_highpage(page, address);
2135 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2136 if (is_zero_pfn(pte_pfn(pteval))) {
2138 * ptl mostly unnecessary.
2142 * paravirt calls inside pte_clear here are
2145 pte_clear(vma->vm_mm, address, _pte);
2149 src_page = pte_page(pteval);
2150 copy_user_highpage(page, src_page, address, vma);
2151 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2152 release_pte_page(src_page);
2154 * ptl mostly unnecessary, but preempt has to
2155 * be disabled to update the per-cpu stats
2156 * inside page_remove_rmap().
2160 * paravirt calls inside pte_clear here are
2163 pte_clear(vma->vm_mm, address, _pte);
2164 page_remove_rmap(src_page, false);
2166 free_page_and_swap_cache(src_page);
2169 address += PAGE_SIZE;
2174 static void khugepaged_alloc_sleep(void)
2178 add_wait_queue(&khugepaged_wait, &wait);
2179 freezable_schedule_timeout_interruptible(
2180 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2181 remove_wait_queue(&khugepaged_wait, &wait);
2184 static int khugepaged_node_load[MAX_NUMNODES];
2186 static bool khugepaged_scan_abort(int nid)
2191 * If zone_reclaim_mode is disabled, then no extra effort is made to
2192 * allocate memory locally.
2194 if (!zone_reclaim_mode)
2197 /* If there is a count for this node already, it must be acceptable */
2198 if (khugepaged_node_load[nid])
2201 for (i = 0; i < MAX_NUMNODES; i++) {
2202 if (!khugepaged_node_load[i])
2204 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2211 static int khugepaged_find_target_node(void)
2213 static int last_khugepaged_target_node = NUMA_NO_NODE;
2214 int nid, target_node = 0, max_value = 0;
2216 /* find first node with max normal pages hit */
2217 for (nid = 0; nid < MAX_NUMNODES; nid++)
2218 if (khugepaged_node_load[nid] > max_value) {
2219 max_value = khugepaged_node_load[nid];
2223 /* do some balance if several nodes have the same hit record */
2224 if (target_node <= last_khugepaged_target_node)
2225 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2227 if (max_value == khugepaged_node_load[nid]) {
2232 last_khugepaged_target_node = target_node;
2236 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2238 if (IS_ERR(*hpage)) {
2244 khugepaged_alloc_sleep();
2245 } else if (*hpage) {
2253 static struct page *
2254 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2255 unsigned long address, int node)
2257 VM_BUG_ON_PAGE(*hpage, *hpage);
2260 * Before allocating the hugepage, release the mmap_sem read lock.
2261 * The allocation can take potentially a long time if it involves
2262 * sync compaction, and we do not need to hold the mmap_sem during
2263 * that. We will recheck the vma after taking it again in write mode.
2265 up_read(&mm->mmap_sem);
2267 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2268 if (unlikely(!*hpage)) {
2269 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2270 *hpage = ERR_PTR(-ENOMEM);
2274 prep_transhuge_page(*hpage);
2275 count_vm_event(THP_COLLAPSE_ALLOC);
2279 static int khugepaged_find_target_node(void)
2284 static inline struct page *alloc_khugepaged_hugepage(void)
2288 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2291 prep_transhuge_page(page);
2295 static struct page *khugepaged_alloc_hugepage(bool *wait)
2300 hpage = alloc_khugepaged_hugepage();
2302 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2307 khugepaged_alloc_sleep();
2309 count_vm_event(THP_COLLAPSE_ALLOC);
2310 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2315 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2318 *hpage = khugepaged_alloc_hugepage(wait);
2320 if (unlikely(!*hpage))
2326 static struct page *
2327 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2328 unsigned long address, int node)
2330 up_read(&mm->mmap_sem);
2337 static bool hugepage_vma_check(struct vm_area_struct *vma)
2339 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2340 (vma->vm_flags & VM_NOHUGEPAGE))
2342 if (!vma->anon_vma || vma->vm_ops)
2344 if (is_vma_temporary_stack(vma))
2346 return !(vma->vm_flags & VM_NO_THP);
2349 static void collapse_huge_page(struct mm_struct *mm,
2350 unsigned long address,
2351 struct page **hpage,
2352 struct vm_area_struct *vma,
2358 struct page *new_page;
2359 spinlock_t *pmd_ptl, *pte_ptl;
2360 int isolated = 0, result = 0;
2361 unsigned long hstart, hend;
2362 struct mem_cgroup *memcg;
2363 unsigned long mmun_start; /* For mmu_notifiers */
2364 unsigned long mmun_end; /* For mmu_notifiers */
2367 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2369 /* Only allocate from the target node */
2370 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
2372 /* release the mmap_sem read lock. */
2373 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2375 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2379 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2380 result = SCAN_CGROUP_CHARGE_FAIL;
2385 * Prevent all access to pagetables with the exception of
2386 * gup_fast later hanlded by the ptep_clear_flush and the VM
2387 * handled by the anon_vma lock + PG_lock.
2389 down_write(&mm->mmap_sem);
2390 if (unlikely(khugepaged_test_exit(mm))) {
2391 result = SCAN_ANY_PROCESS;
2395 vma = find_vma(mm, address);
2397 result = SCAN_VMA_NULL;
2400 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2401 hend = vma->vm_end & HPAGE_PMD_MASK;
2402 if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
2403 result = SCAN_ADDRESS_RANGE;
2406 if (!hugepage_vma_check(vma)) {
2407 result = SCAN_VMA_CHECK;
2410 pmd = mm_find_pmd(mm, address);
2412 result = SCAN_PMD_NULL;
2416 anon_vma_lock_write(vma->anon_vma);
2418 pte = pte_offset_map(pmd, address);
2419 pte_ptl = pte_lockptr(mm, pmd);
2421 mmun_start = address;
2422 mmun_end = address + HPAGE_PMD_SIZE;
2423 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2424 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2426 * After this gup_fast can't run anymore. This also removes
2427 * any huge TLB entry from the CPU so we won't allow
2428 * huge and small TLB entries for the same virtual address
2429 * to avoid the risk of CPU bugs in that area.
2431 _pmd = pmdp_collapse_flush(vma, address, pmd);
2432 spin_unlock(pmd_ptl);
2433 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2436 isolated = __collapse_huge_page_isolate(vma, address, pte);
2437 spin_unlock(pte_ptl);
2439 if (unlikely(!isolated)) {
2442 BUG_ON(!pmd_none(*pmd));
2444 * We can only use set_pmd_at when establishing
2445 * hugepmds and never for establishing regular pmds that
2446 * points to regular pagetables. Use pmd_populate for that
2448 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2449 spin_unlock(pmd_ptl);
2450 anon_vma_unlock_write(vma->anon_vma);
2456 * All pages are isolated and locked so anon_vma rmap
2457 * can't run anymore.
2459 anon_vma_unlock_write(vma->anon_vma);
2461 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2463 __SetPageUptodate(new_page);
2464 pgtable = pmd_pgtable(_pmd);
2466 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2467 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2470 * spin_lock() below is not the equivalent of smp_wmb(), so
2471 * this is needed to avoid the copy_huge_page writes to become
2472 * visible after the set_pmd_at() write.
2477 BUG_ON(!pmd_none(*pmd));
2478 page_add_new_anon_rmap(new_page, vma, address, true);
2479 mem_cgroup_commit_charge(new_page, memcg, false, true);
2480 lru_cache_add_active_or_unevictable(new_page, vma);
2481 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2482 set_pmd_at(mm, address, pmd, _pmd);
2483 update_mmu_cache_pmd(vma, address, pmd);
2484 spin_unlock(pmd_ptl);
2488 khugepaged_pages_collapsed++;
2489 result = SCAN_SUCCEED;
2491 up_write(&mm->mmap_sem);
2492 trace_mm_collapse_huge_page(mm, isolated, result);
2496 trace_mm_collapse_huge_page(mm, isolated, result);
2499 mem_cgroup_cancel_charge(new_page, memcg, true);
2503 static int khugepaged_scan_pmd(struct mm_struct *mm,
2504 struct vm_area_struct *vma,
2505 unsigned long address,
2506 struct page **hpage)
2510 int ret = 0, none_or_zero = 0, result = 0;
2511 struct page *page = NULL;
2512 unsigned long _address;
2514 int node = NUMA_NO_NODE;
2515 bool writable = false, referenced = false;
2517 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2519 pmd = mm_find_pmd(mm, address);
2521 result = SCAN_PMD_NULL;
2525 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2526 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2527 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2528 _pte++, _address += PAGE_SIZE) {
2529 pte_t pteval = *_pte;
2530 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2531 if (!userfaultfd_armed(vma) &&
2532 ++none_or_zero <= khugepaged_max_ptes_none) {
2535 result = SCAN_EXCEED_NONE_PTE;
2539 if (!pte_present(pteval)) {
2540 result = SCAN_PTE_NON_PRESENT;
2543 if (pte_write(pteval))
2546 page = vm_normal_page(vma, _address, pteval);
2547 if (unlikely(!page)) {
2548 result = SCAN_PAGE_NULL;
2552 /* TODO: teach khugepaged to collapse THP mapped with pte */
2553 if (PageCompound(page)) {
2554 result = SCAN_PAGE_COMPOUND;
2559 * Record which node the original page is from and save this
2560 * information to khugepaged_node_load[].
2561 * Khupaged will allocate hugepage from the node has the max
2564 node = page_to_nid(page);
2565 if (khugepaged_scan_abort(node)) {
2566 result = SCAN_SCAN_ABORT;
2569 khugepaged_node_load[node]++;
2570 if (!PageLRU(page)) {
2571 result = SCAN_PAGE_LRU;
2574 if (PageLocked(page)) {
2575 result = SCAN_PAGE_LOCK;
2578 if (!PageAnon(page)) {
2579 result = SCAN_PAGE_ANON;
2584 * cannot use mapcount: can't collapse if there's a gup pin.
2585 * The page must only be referenced by the scanned process
2586 * and page swap cache.
2588 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2589 result = SCAN_PAGE_COUNT;
2592 if (pte_young(pteval) ||
2593 page_is_young(page) || PageReferenced(page) ||
2594 mmu_notifier_test_young(vma->vm_mm, address))
2599 result = SCAN_SUCCEED;
2602 result = SCAN_NO_REFERENCED_PAGE;
2605 result = SCAN_PAGE_RO;
2608 pte_unmap_unlock(pte, ptl);
2610 node = khugepaged_find_target_node();
2611 /* collapse_huge_page will return with the mmap_sem released */
2612 collapse_huge_page(mm, address, hpage, vma, node);
2615 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
2616 none_or_zero, result);
2620 static void collect_mm_slot(struct mm_slot *mm_slot)
2622 struct mm_struct *mm = mm_slot->mm;
2624 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2626 if (khugepaged_test_exit(mm)) {
2628 hash_del(&mm_slot->hash);
2629 list_del(&mm_slot->mm_node);
2632 * Not strictly needed because the mm exited already.
2634 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2637 /* khugepaged_mm_lock actually not necessary for the below */
2638 free_mm_slot(mm_slot);
2643 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2644 struct page **hpage)
2645 __releases(&khugepaged_mm_lock)
2646 __acquires(&khugepaged_mm_lock)
2648 struct mm_slot *mm_slot;
2649 struct mm_struct *mm;
2650 struct vm_area_struct *vma;
2654 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2656 if (khugepaged_scan.mm_slot)
2657 mm_slot = khugepaged_scan.mm_slot;
2659 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2660 struct mm_slot, mm_node);
2661 khugepaged_scan.address = 0;
2662 khugepaged_scan.mm_slot = mm_slot;
2664 spin_unlock(&khugepaged_mm_lock);
2667 down_read(&mm->mmap_sem);
2668 if (unlikely(khugepaged_test_exit(mm)))
2671 vma = find_vma(mm, khugepaged_scan.address);
2674 for (; vma; vma = vma->vm_next) {
2675 unsigned long hstart, hend;
2678 if (unlikely(khugepaged_test_exit(mm))) {
2682 if (!hugepage_vma_check(vma)) {
2687 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2688 hend = vma->vm_end & HPAGE_PMD_MASK;
2691 if (khugepaged_scan.address > hend)
2693 if (khugepaged_scan.address < hstart)
2694 khugepaged_scan.address = hstart;
2695 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2697 while (khugepaged_scan.address < hend) {
2700 if (unlikely(khugepaged_test_exit(mm)))
2701 goto breakouterloop;
2703 VM_BUG_ON(khugepaged_scan.address < hstart ||
2704 khugepaged_scan.address + HPAGE_PMD_SIZE >
2706 ret = khugepaged_scan_pmd(mm, vma,
2707 khugepaged_scan.address,
2709 /* move to next address */
2710 khugepaged_scan.address += HPAGE_PMD_SIZE;
2711 progress += HPAGE_PMD_NR;
2713 /* we released mmap_sem so break loop */
2714 goto breakouterloop_mmap_sem;
2715 if (progress >= pages)
2716 goto breakouterloop;
2720 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2721 breakouterloop_mmap_sem:
2723 spin_lock(&khugepaged_mm_lock);
2724 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2726 * Release the current mm_slot if this mm is about to die, or
2727 * if we scanned all vmas of this mm.
2729 if (khugepaged_test_exit(mm) || !vma) {
2731 * Make sure that if mm_users is reaching zero while
2732 * khugepaged runs here, khugepaged_exit will find
2733 * mm_slot not pointing to the exiting mm.
2735 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2736 khugepaged_scan.mm_slot = list_entry(
2737 mm_slot->mm_node.next,
2738 struct mm_slot, mm_node);
2739 khugepaged_scan.address = 0;
2741 khugepaged_scan.mm_slot = NULL;
2742 khugepaged_full_scans++;
2745 collect_mm_slot(mm_slot);
2751 static int khugepaged_has_work(void)
2753 return !list_empty(&khugepaged_scan.mm_head) &&
2754 khugepaged_enabled();
2757 static int khugepaged_wait_event(void)
2759 return !list_empty(&khugepaged_scan.mm_head) ||
2760 kthread_should_stop();
2763 static void khugepaged_do_scan(void)
2765 struct page *hpage = NULL;
2766 unsigned int progress = 0, pass_through_head = 0;
2767 unsigned int pages = khugepaged_pages_to_scan;
2770 barrier(); /* write khugepaged_pages_to_scan to local stack */
2772 while (progress < pages) {
2773 if (!khugepaged_prealloc_page(&hpage, &wait))
2778 if (unlikely(kthread_should_stop() || try_to_freeze()))
2781 spin_lock(&khugepaged_mm_lock);
2782 if (!khugepaged_scan.mm_slot)
2783 pass_through_head++;
2784 if (khugepaged_has_work() &&
2785 pass_through_head < 2)
2786 progress += khugepaged_scan_mm_slot(pages - progress,
2790 spin_unlock(&khugepaged_mm_lock);
2793 if (!IS_ERR_OR_NULL(hpage))
2797 static bool khugepaged_should_wakeup(void)
2799 return kthread_should_stop() ||
2800 time_after_eq(jiffies, khugepaged_sleep_expire);
2803 static void khugepaged_wait_work(void)
2805 if (khugepaged_has_work()) {
2806 const unsigned long scan_sleep_jiffies =
2807 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
2809 if (!scan_sleep_jiffies)
2812 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
2813 wait_event_freezable_timeout(khugepaged_wait,
2814 khugepaged_should_wakeup(),
2815 scan_sleep_jiffies);
2819 if (khugepaged_enabled())
2820 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2823 static int khugepaged(void *none)
2825 struct mm_slot *mm_slot;
2828 set_user_nice(current, MAX_NICE);
2830 while (!kthread_should_stop()) {
2831 khugepaged_do_scan();
2832 khugepaged_wait_work();
2835 spin_lock(&khugepaged_mm_lock);
2836 mm_slot = khugepaged_scan.mm_slot;
2837 khugepaged_scan.mm_slot = NULL;
2839 collect_mm_slot(mm_slot);
2840 spin_unlock(&khugepaged_mm_lock);
2844 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2845 unsigned long haddr, pmd_t *pmd)
2847 struct mm_struct *mm = vma->vm_mm;
2852 /* leave pmd empty until pte is filled */
2853 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2855 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2856 pmd_populate(mm, &_pmd, pgtable);
2858 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2860 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2861 entry = pte_mkspecial(entry);
2862 pte = pte_offset_map(&_pmd, haddr);
2863 VM_BUG_ON(!pte_none(*pte));
2864 set_pte_at(mm, haddr, pte, entry);
2867 smp_wmb(); /* make pte visible before pmd */
2868 pmd_populate(mm, pmd, pgtable);
2869 put_huge_zero_page();
2872 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2873 unsigned long haddr, bool freeze)
2875 struct mm_struct *mm = vma->vm_mm;
2879 bool young, write, dirty;
2883 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2884 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2885 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2886 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
2888 count_vm_event(THP_SPLIT_PMD);
2890 if (vma_is_dax(vma)) {
2891 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2892 if (is_huge_zero_pmd(_pmd))
2893 put_huge_zero_page();
2895 } else if (is_huge_zero_pmd(*pmd)) {
2896 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2899 page = pmd_page(*pmd);
2900 VM_BUG_ON_PAGE(!page_count(page), page);
2901 page_ref_add(page, HPAGE_PMD_NR - 1);
2902 write = pmd_write(*pmd);
2903 young = pmd_young(*pmd);
2904 dirty = pmd_dirty(*pmd);
2906 pmdp_huge_split_prepare(vma, haddr, pmd);
2907 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2908 pmd_populate(mm, &_pmd, pgtable);
2910 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2913 * Note that NUMA hinting access restrictions are not
2914 * transferred to avoid any possibility of altering
2915 * permissions across VMAs.
2918 swp_entry_t swp_entry;
2919 swp_entry = make_migration_entry(page + i, write);
2920 entry = swp_entry_to_pte(swp_entry);
2922 entry = mk_pte(page + i, vma->vm_page_prot);
2923 entry = maybe_mkwrite(entry, vma);
2925 entry = pte_wrprotect(entry);
2927 entry = pte_mkold(entry);
2930 SetPageDirty(page + i);
2931 pte = pte_offset_map(&_pmd, addr);
2932 BUG_ON(!pte_none(*pte));
2933 set_pte_at(mm, addr, pte, entry);
2934 atomic_inc(&page[i]._mapcount);
2939 * Set PG_double_map before dropping compound_mapcount to avoid
2940 * false-negative page_mapped().
2942 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2943 for (i = 0; i < HPAGE_PMD_NR; i++)
2944 atomic_inc(&page[i]._mapcount);
2947 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2948 /* Last compound_mapcount is gone. */
2949 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
2950 if (TestClearPageDoubleMap(page)) {
2951 /* No need in mapcount reference anymore */
2952 for (i = 0; i < HPAGE_PMD_NR; i++)
2953 atomic_dec(&page[i]._mapcount);
2957 smp_wmb(); /* make pte visible before pmd */
2959 * Up to this point the pmd is present and huge and userland has the
2960 * whole access to the hugepage during the split (which happens in
2961 * place). If we overwrite the pmd with the not-huge version pointing
2962 * to the pte here (which of course we could if all CPUs were bug
2963 * free), userland could trigger a small page size TLB miss on the
2964 * small sized TLB while the hugepage TLB entry is still established in
2965 * the huge TLB. Some CPU doesn't like that.
2966 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2967 * 383 on page 93. Intel should be safe but is also warns that it's
2968 * only safe if the permission and cache attributes of the two entries
2969 * loaded in the two TLB is identical (which should be the case here).
2970 * But it is generally safer to never allow small and huge TLB entries
2971 * for the same virtual address to be loaded simultaneously. So instead
2972 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2973 * current pmd notpresent (atomically because here the pmd_trans_huge
2974 * and pmd_trans_splitting must remain set at all times on the pmd
2975 * until the split is complete for this pmd), then we flush the SMP TLB
2976 * and finally we write the non-huge version of the pmd entry with
2979 pmdp_invalidate(vma, haddr, pmd);
2980 pmd_populate(mm, pmd, pgtable);
2983 for (i = 0; i < HPAGE_PMD_NR; i++) {
2984 page_remove_rmap(page + i, false);
2990 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2991 unsigned long address, bool freeze)
2994 struct mm_struct *mm = vma->vm_mm;
2995 unsigned long haddr = address & HPAGE_PMD_MASK;
2997 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2998 ptl = pmd_lock(mm, pmd);
2999 if (pmd_trans_huge(*pmd)) {
3000 struct page *page = pmd_page(*pmd);
3001 if (PageMlocked(page))
3002 clear_page_mlock(page);
3003 } else if (!pmd_devmap(*pmd))
3005 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
3008 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
3011 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
3012 bool freeze, struct page *page)
3018 pgd = pgd_offset(vma->vm_mm, address);
3019 if (!pgd_present(*pgd))
3022 pud = pud_offset(pgd, address);
3023 if (!pud_present(*pud))
3026 pmd = pmd_offset(pud, address);
3027 if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)))
3031 * If caller asks to setup a migration entries, we need a page to check
3032 * pmd against. Otherwise we can end up replacing wrong page.
3034 VM_BUG_ON(freeze && !page);
3035 if (page && page != pmd_page(*pmd))
3039 * Caller holds the mmap_sem write mode or the anon_vma lock,
3040 * so a huge pmd cannot materialize from under us (khugepaged
3041 * holds both the mmap_sem write mode and the anon_vma lock
3044 __split_huge_pmd(vma, pmd, address, freeze);
3047 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3048 unsigned long start,
3053 * If the new start address isn't hpage aligned and it could
3054 * previously contain an hugepage: check if we need to split
3057 if (start & ~HPAGE_PMD_MASK &&
3058 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3059 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3060 split_huge_pmd_address(vma, start, false, NULL);
3063 * If the new end address isn't hpage aligned and it could
3064 * previously contain an hugepage: check if we need to split
3067 if (end & ~HPAGE_PMD_MASK &&
3068 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3069 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3070 split_huge_pmd_address(vma, end, false, NULL);
3073 * If we're also updating the vma->vm_next->vm_start, if the new
3074 * vm_next->vm_start isn't page aligned and it could previously
3075 * contain an hugepage: check if we need to split an huge pmd.
3077 if (adjust_next > 0) {
3078 struct vm_area_struct *next = vma->vm_next;
3079 unsigned long nstart = next->vm_start;
3080 nstart += adjust_next << PAGE_SHIFT;
3081 if (nstart & ~HPAGE_PMD_MASK &&
3082 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3083 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3084 split_huge_pmd_address(next, nstart, false, NULL);
3088 static void freeze_page(struct page *page)
3090 enum ttu_flags ttu_flags = TTU_MIGRATION | TTU_IGNORE_MLOCK |
3091 TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED;
3094 VM_BUG_ON_PAGE(!PageHead(page), page);
3096 /* We only need TTU_SPLIT_HUGE_PMD once */
3097 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
3098 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) {
3099 /* Cut short if the page is unmapped */
3100 if (page_count(page) == 1)
3103 ret = try_to_unmap(page + i, ttu_flags);
3108 static void unfreeze_page(struct page *page)
3112 for (i = 0; i < HPAGE_PMD_NR; i++)
3113 remove_migration_ptes(page + i, page + i, true);
3116 static void __split_huge_page_tail(struct page *head, int tail,
3117 struct lruvec *lruvec, struct list_head *list)
3119 struct page *page_tail = head + tail;
3121 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
3122 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
3125 * tail_page->_refcount is zero and not changing from under us. But
3126 * get_page_unless_zero() may be running from under us on the
3127 * tail_page. If we used atomic_set() below instead of atomic_inc(), we
3128 * would then run atomic_set() concurrently with
3129 * get_page_unless_zero(), and atomic_set() is implemented in C not
3130 * using locked ops. spin_unlock on x86 sometime uses locked ops
3131 * because of PPro errata 66, 92, so unless somebody can guarantee
3132 * atomic_set() here would be safe on all archs (and not only on x86),
3133 * it's safer to use atomic_inc().
3135 page_ref_inc(page_tail);
3137 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3138 page_tail->flags |= (head->flags &
3139 ((1L << PG_referenced) |
3140 (1L << PG_swapbacked) |
3141 (1L << PG_mlocked) |
3142 (1L << PG_uptodate) |
3145 (1L << PG_unevictable) |
3149 * After clearing PageTail the gup refcount can be released.
3150 * Page flags also must be visible before we make the page non-compound.
3154 clear_compound_head(page_tail);
3156 if (page_is_young(head))
3157 set_page_young(page_tail);
3158 if (page_is_idle(head))
3159 set_page_idle(page_tail);
3161 /* ->mapping in first tail page is compound_mapcount */
3162 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3164 page_tail->mapping = head->mapping;
3166 page_tail->index = head->index + tail;
3167 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3168 lru_add_page_tail(head, page_tail, lruvec, list);
3171 static void __split_huge_page(struct page *page, struct list_head *list)
3173 struct page *head = compound_head(page);
3174 struct zone *zone = page_zone(head);
3175 struct lruvec *lruvec;
3178 /* prevent PageLRU to go away from under us, and freeze lru stats */
3179 spin_lock_irq(&zone->lru_lock);
3180 lruvec = mem_cgroup_page_lruvec(head, zone);
3182 /* complete memcg works before add pages to LRU */
3183 mem_cgroup_split_huge_fixup(head);
3185 for (i = HPAGE_PMD_NR - 1; i >= 1; i--)
3186 __split_huge_page_tail(head, i, lruvec, list);
3188 ClearPageCompound(head);
3189 spin_unlock_irq(&zone->lru_lock);
3191 unfreeze_page(head);
3193 for (i = 0; i < HPAGE_PMD_NR; i++) {
3194 struct page *subpage = head + i;
3195 if (subpage == page)
3197 unlock_page(subpage);
3200 * Subpages may be freed if there wasn't any mapping
3201 * like if add_to_swap() is running on a lru page that
3202 * had its mapping zapped. And freeing these pages
3203 * requires taking the lru_lock so we do the put_page
3204 * of the tail pages after the split is complete.
3210 int total_mapcount(struct page *page)
3214 VM_BUG_ON_PAGE(PageTail(page), page);
3216 if (likely(!PageCompound(page)))
3217 return atomic_read(&page->_mapcount) + 1;
3219 ret = compound_mapcount(page);
3222 for (i = 0; i < HPAGE_PMD_NR; i++)
3223 ret += atomic_read(&page[i]._mapcount) + 1;
3224 if (PageDoubleMap(page))
3225 ret -= HPAGE_PMD_NR;
3230 * This calculates accurately how many mappings a transparent hugepage
3231 * has (unlike page_mapcount() which isn't fully accurate). This full
3232 * accuracy is primarily needed to know if copy-on-write faults can
3233 * reuse the page and change the mapping to read-write instead of
3234 * copying them. At the same time this returns the total_mapcount too.
3236 * The function returns the highest mapcount any one of the subpages
3237 * has. If the return value is one, even if different processes are
3238 * mapping different subpages of the transparent hugepage, they can
3239 * all reuse it, because each process is reusing a different subpage.
3241 * The total_mapcount is instead counting all virtual mappings of the
3242 * subpages. If the total_mapcount is equal to "one", it tells the
3243 * caller all mappings belong to the same "mm" and in turn the
3244 * anon_vma of the transparent hugepage can become the vma->anon_vma
3245 * local one as no other process may be mapping any of the subpages.
3247 * It would be more accurate to replace page_mapcount() with
3248 * page_trans_huge_mapcount(), however we only use
3249 * page_trans_huge_mapcount() in the copy-on-write faults where we
3250 * need full accuracy to avoid breaking page pinning, because
3251 * page_trans_huge_mapcount() is slower than page_mapcount().
3253 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
3255 int i, ret, _total_mapcount, mapcount;
3257 /* hugetlbfs shouldn't call it */
3258 VM_BUG_ON_PAGE(PageHuge(page), page);
3260 if (likely(!PageTransCompound(page))) {
3261 mapcount = atomic_read(&page->_mapcount) + 1;
3263 *total_mapcount = mapcount;
3267 page = compound_head(page);
3269 _total_mapcount = ret = 0;
3270 for (i = 0; i < HPAGE_PMD_NR; i++) {
3271 mapcount = atomic_read(&page[i]._mapcount) + 1;
3272 ret = max(ret, mapcount);
3273 _total_mapcount += mapcount;
3275 if (PageDoubleMap(page)) {
3277 _total_mapcount -= HPAGE_PMD_NR;
3279 mapcount = compound_mapcount(page);
3281 _total_mapcount += mapcount;
3283 *total_mapcount = _total_mapcount;
3288 * This function splits huge page into normal pages. @page can point to any
3289 * subpage of huge page to split. Split doesn't change the position of @page.
3291 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3292 * The huge page must be locked.
3294 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3296 * Both head page and tail pages will inherit mapping, flags, and so on from
3299 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3300 * they are not mapped.
3302 * Returns 0 if the hugepage is split successfully.
3303 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3306 int split_huge_page_to_list(struct page *page, struct list_head *list)
3308 struct page *head = compound_head(page);
3309 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
3310 struct anon_vma *anon_vma;
3311 int count, mapcount, ret;
3313 unsigned long flags;
3315 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3316 VM_BUG_ON_PAGE(!PageAnon(page), page);
3317 VM_BUG_ON_PAGE(!PageLocked(page), page);
3318 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3319 VM_BUG_ON_PAGE(!PageCompound(page), page);
3322 * The caller does not necessarily hold an mmap_sem that would prevent
3323 * the anon_vma disappearing so we first we take a reference to it
3324 * and then lock the anon_vma for write. This is similar to
3325 * page_lock_anon_vma_read except the write lock is taken to serialise
3326 * against parallel split or collapse operations.
3328 anon_vma = page_get_anon_vma(head);
3333 anon_vma_lock_write(anon_vma);
3336 * Racy check if we can split the page, before freeze_page() will
3339 if (total_mapcount(head) != page_count(head) - 1) {
3344 mlocked = PageMlocked(page);
3346 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3348 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3352 /* Prevent deferred_split_scan() touching ->_refcount */
3353 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3354 count = page_count(head);
3355 mapcount = total_mapcount(head);
3356 if (!mapcount && count == 1) {
3357 if (!list_empty(page_deferred_list(head))) {
3358 pgdata->split_queue_len--;
3359 list_del(page_deferred_list(head));
3361 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3362 __split_huge_page(page, list);
3364 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
3365 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3366 pr_alert("total_mapcount: %u, page_count(): %u\n",
3369 dump_page(head, NULL);
3370 dump_page(page, "total_mapcount(head) > 0");
3373 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3374 unfreeze_page(head);
3379 anon_vma_unlock_write(anon_vma);
3380 put_anon_vma(anon_vma);
3382 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3386 void free_transhuge_page(struct page *page)
3388 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3389 unsigned long flags;
3391 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3392 if (!list_empty(page_deferred_list(page))) {
3393 pgdata->split_queue_len--;
3394 list_del(page_deferred_list(page));
3396 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3397 free_compound_page(page);
3400 void deferred_split_huge_page(struct page *page)
3402 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3403 unsigned long flags;
3405 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3407 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3408 if (list_empty(page_deferred_list(page))) {
3409 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
3410 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
3411 pgdata->split_queue_len++;
3413 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3416 static unsigned long deferred_split_count(struct shrinker *shrink,
3417 struct shrink_control *sc)
3419 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3420 return ACCESS_ONCE(pgdata->split_queue_len);
3423 static unsigned long deferred_split_scan(struct shrinker *shrink,
3424 struct shrink_control *sc)
3426 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3427 unsigned long flags;
3428 LIST_HEAD(list), *pos, *next;
3432 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3433 /* Take pin on all head pages to avoid freeing them under us */
3434 list_for_each_safe(pos, next, &pgdata->split_queue) {
3435 page = list_entry((void *)pos, struct page, mapping);
3436 page = compound_head(page);
3437 if (get_page_unless_zero(page)) {
3438 list_move(page_deferred_list(page), &list);
3440 /* We lost race with put_compound_page() */
3441 list_del_init(page_deferred_list(page));
3442 pgdata->split_queue_len--;
3444 if (!--sc->nr_to_scan)
3447 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3449 list_for_each_safe(pos, next, &list) {
3450 page = list_entry((void *)pos, struct page, mapping);
3452 /* split_huge_page() removes page from list on success */
3453 if (!split_huge_page(page))
3459 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3460 list_splice_tail(&list, &pgdata->split_queue);
3461 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3464 * Stop shrinker if we didn't split any page, but the queue is empty.
3465 * This can happen if pages were freed under us.
3467 if (!split && list_empty(&pgdata->split_queue))
3472 static struct shrinker deferred_split_shrinker = {
3473 .count_objects = deferred_split_count,
3474 .scan_objects = deferred_split_scan,
3475 .seeks = DEFAULT_SEEKS,
3476 .flags = SHRINKER_NUMA_AWARE,
3479 #ifdef CONFIG_DEBUG_FS
3480 static int split_huge_pages_set(void *data, u64 val)
3484 unsigned long pfn, max_zone_pfn;
3485 unsigned long total = 0, split = 0;
3490 for_each_populated_zone(zone) {
3491 max_zone_pfn = zone_end_pfn(zone);
3492 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3493 if (!pfn_valid(pfn))
3496 page = pfn_to_page(pfn);
3497 if (!get_page_unless_zero(page))
3500 if (zone != page_zone(page))
3503 if (!PageHead(page) || !PageAnon(page) ||
3509 if (!split_huge_page(page))
3517 pr_info("%lu of %lu THP split\n", split, total);
3521 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3524 static int __init split_huge_pages_debugfs(void)
3528 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3529 &split_huge_pages_fops);
3531 pr_warn("Failed to create split_huge_pages in debugfs");
3534 late_initcall(split_huge_pages_debugfs);