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_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 struct task_struct *khugepaged_thread __read_mostly;
93 static DEFINE_MUTEX(khugepaged_mutex);
94 static DEFINE_SPINLOCK(khugepaged_mm_lock);
95 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
97 * default collapse hugepages if there is at least one pte mapped like
98 * it would have happened if the vma was large enough during page
101 static unsigned int khugepaged_max_ptes_none __read_mostly;
103 static int khugepaged(void *none);
104 static int khugepaged_slab_init(void);
105 static void khugepaged_slab_exit(void);
107 #define MM_SLOTS_HASH_BITS 10
108 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
110 static struct kmem_cache *mm_slot_cache __read_mostly;
113 * struct mm_slot - hash lookup from mm to mm_slot
114 * @hash: hash collision list
115 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
116 * @mm: the mm that this information is valid for
119 struct hlist_node hash;
120 struct list_head mm_node;
121 struct mm_struct *mm;
125 * struct khugepaged_scan - cursor for scanning
126 * @mm_head: the head of the mm list to scan
127 * @mm_slot: the current mm_slot we are scanning
128 * @address: the next address inside that to be scanned
130 * There is only the one khugepaged_scan instance of this cursor structure.
132 struct khugepaged_scan {
133 struct list_head mm_head;
134 struct mm_slot *mm_slot;
135 unsigned long address;
137 static struct khugepaged_scan khugepaged_scan = {
138 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
141 static struct shrinker deferred_split_shrinker;
143 static void set_recommended_min_free_kbytes(void)
147 unsigned long recommended_min;
149 for_each_populated_zone(zone)
152 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
153 recommended_min = pageblock_nr_pages * nr_zones * 2;
156 * Make sure that on average at least two pageblocks are almost free
157 * of another type, one for a migratetype to fall back to and a
158 * second to avoid subsequent fallbacks of other types There are 3
159 * MIGRATE_TYPES we care about.
161 recommended_min += pageblock_nr_pages * nr_zones *
162 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
164 /* don't ever allow to reserve more than 5% of the lowmem */
165 recommended_min = min(recommended_min,
166 (unsigned long) nr_free_buffer_pages() / 20);
167 recommended_min <<= (PAGE_SHIFT-10);
169 if (recommended_min > min_free_kbytes) {
170 if (user_min_free_kbytes >= 0)
171 pr_info("raising min_free_kbytes from %d to %lu "
172 "to help transparent hugepage allocations\n",
173 min_free_kbytes, recommended_min);
175 min_free_kbytes = recommended_min;
177 setup_per_zone_wmarks();
180 static int start_stop_khugepaged(void)
183 if (khugepaged_enabled()) {
184 if (!khugepaged_thread)
185 khugepaged_thread = kthread_run(khugepaged, NULL,
187 if (IS_ERR(khugepaged_thread)) {
188 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
189 err = PTR_ERR(khugepaged_thread);
190 khugepaged_thread = NULL;
194 if (!list_empty(&khugepaged_scan.mm_head))
195 wake_up_interruptible(&khugepaged_wait);
197 set_recommended_min_free_kbytes();
198 } else if (khugepaged_thread) {
199 kthread_stop(khugepaged_thread);
200 khugepaged_thread = NULL;
206 static atomic_t huge_zero_refcount;
207 struct page *huge_zero_page __read_mostly;
209 struct page *get_huge_zero_page(void)
211 struct page *zero_page;
213 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
214 return READ_ONCE(huge_zero_page);
216 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
219 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
222 count_vm_event(THP_ZERO_PAGE_ALLOC);
224 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
226 __free_pages(zero_page, compound_order(zero_page));
230 /* We take additional reference here. It will be put back by shrinker */
231 atomic_set(&huge_zero_refcount, 2);
233 return READ_ONCE(huge_zero_page);
236 static void put_huge_zero_page(void)
239 * Counter should never go to zero here. Only shrinker can put
242 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
245 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
246 struct shrink_control *sc)
248 /* we can free zero page only if last reference remains */
249 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
252 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
253 struct shrink_control *sc)
255 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
256 struct page *zero_page = xchg(&huge_zero_page, NULL);
257 BUG_ON(zero_page == NULL);
258 __free_pages(zero_page, compound_order(zero_page));
265 static struct shrinker huge_zero_page_shrinker = {
266 .count_objects = shrink_huge_zero_page_count,
267 .scan_objects = shrink_huge_zero_page_scan,
268 .seeks = DEFAULT_SEEKS,
273 static ssize_t double_flag_show(struct kobject *kobj,
274 struct kobj_attribute *attr, char *buf,
275 enum transparent_hugepage_flag enabled,
276 enum transparent_hugepage_flag req_madv)
278 if (test_bit(enabled, &transparent_hugepage_flags)) {
279 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
280 return sprintf(buf, "[always] madvise never\n");
281 } else if (test_bit(req_madv, &transparent_hugepage_flags))
282 return sprintf(buf, "always [madvise] never\n");
284 return sprintf(buf, "always madvise [never]\n");
286 static ssize_t double_flag_store(struct kobject *kobj,
287 struct kobj_attribute *attr,
288 const char *buf, size_t count,
289 enum transparent_hugepage_flag enabled,
290 enum transparent_hugepage_flag req_madv)
292 if (!memcmp("always", buf,
293 min(sizeof("always")-1, count))) {
294 set_bit(enabled, &transparent_hugepage_flags);
295 clear_bit(req_madv, &transparent_hugepage_flags);
296 } else if (!memcmp("madvise", buf,
297 min(sizeof("madvise")-1, count))) {
298 clear_bit(enabled, &transparent_hugepage_flags);
299 set_bit(req_madv, &transparent_hugepage_flags);
300 } else if (!memcmp("never", buf,
301 min(sizeof("never")-1, count))) {
302 clear_bit(enabled, &transparent_hugepage_flags);
303 clear_bit(req_madv, &transparent_hugepage_flags);
310 static ssize_t enabled_show(struct kobject *kobj,
311 struct kobj_attribute *attr, char *buf)
313 return double_flag_show(kobj, attr, buf,
314 TRANSPARENT_HUGEPAGE_FLAG,
315 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
317 static ssize_t enabled_store(struct kobject *kobj,
318 struct kobj_attribute *attr,
319 const char *buf, size_t count)
323 ret = double_flag_store(kobj, attr, buf, count,
324 TRANSPARENT_HUGEPAGE_FLAG,
325 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
330 mutex_lock(&khugepaged_mutex);
331 err = start_stop_khugepaged();
332 mutex_unlock(&khugepaged_mutex);
340 static struct kobj_attribute enabled_attr =
341 __ATTR(enabled, 0644, enabled_show, enabled_store);
343 static ssize_t single_flag_show(struct kobject *kobj,
344 struct kobj_attribute *attr, char *buf,
345 enum transparent_hugepage_flag flag)
347 return sprintf(buf, "%d\n",
348 !!test_bit(flag, &transparent_hugepage_flags));
351 static ssize_t single_flag_store(struct kobject *kobj,
352 struct kobj_attribute *attr,
353 const char *buf, size_t count,
354 enum transparent_hugepage_flag flag)
359 ret = kstrtoul(buf, 10, &value);
366 set_bit(flag, &transparent_hugepage_flags);
368 clear_bit(flag, &transparent_hugepage_flags);
374 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
375 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
376 * memory just to allocate one more hugepage.
378 static ssize_t defrag_show(struct kobject *kobj,
379 struct kobj_attribute *attr, char *buf)
381 return double_flag_show(kobj, attr, buf,
382 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
383 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
385 static ssize_t defrag_store(struct kobject *kobj,
386 struct kobj_attribute *attr,
387 const char *buf, size_t count)
389 return double_flag_store(kobj, attr, buf, count,
390 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
391 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
393 static struct kobj_attribute defrag_attr =
394 __ATTR(defrag, 0644, defrag_show, defrag_store);
396 static ssize_t use_zero_page_show(struct kobject *kobj,
397 struct kobj_attribute *attr, char *buf)
399 return single_flag_show(kobj, attr, buf,
400 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
402 static ssize_t use_zero_page_store(struct kobject *kobj,
403 struct kobj_attribute *attr, const char *buf, size_t count)
405 return single_flag_store(kobj, attr, buf, count,
406 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
408 static struct kobj_attribute use_zero_page_attr =
409 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
410 #ifdef CONFIG_DEBUG_VM
411 static ssize_t debug_cow_show(struct kobject *kobj,
412 struct kobj_attribute *attr, char *buf)
414 return single_flag_show(kobj, attr, buf,
415 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
417 static ssize_t debug_cow_store(struct kobject *kobj,
418 struct kobj_attribute *attr,
419 const char *buf, size_t count)
421 return single_flag_store(kobj, attr, buf, count,
422 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
424 static struct kobj_attribute debug_cow_attr =
425 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
426 #endif /* CONFIG_DEBUG_VM */
428 static struct attribute *hugepage_attr[] = {
431 &use_zero_page_attr.attr,
432 #ifdef CONFIG_DEBUG_VM
433 &debug_cow_attr.attr,
438 static struct attribute_group hugepage_attr_group = {
439 .attrs = hugepage_attr,
442 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
443 struct kobj_attribute *attr,
446 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
449 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
450 struct kobj_attribute *attr,
451 const char *buf, size_t count)
456 err = kstrtoul(buf, 10, &msecs);
457 if (err || msecs > UINT_MAX)
460 khugepaged_scan_sleep_millisecs = msecs;
461 wake_up_interruptible(&khugepaged_wait);
465 static struct kobj_attribute scan_sleep_millisecs_attr =
466 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
467 scan_sleep_millisecs_store);
469 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
470 struct kobj_attribute *attr,
473 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
476 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
477 struct kobj_attribute *attr,
478 const char *buf, size_t count)
483 err = kstrtoul(buf, 10, &msecs);
484 if (err || msecs > UINT_MAX)
487 khugepaged_alloc_sleep_millisecs = msecs;
488 wake_up_interruptible(&khugepaged_wait);
492 static struct kobj_attribute alloc_sleep_millisecs_attr =
493 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
494 alloc_sleep_millisecs_store);
496 static ssize_t pages_to_scan_show(struct kobject *kobj,
497 struct kobj_attribute *attr,
500 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
502 static ssize_t pages_to_scan_store(struct kobject *kobj,
503 struct kobj_attribute *attr,
504 const char *buf, size_t count)
509 err = kstrtoul(buf, 10, &pages);
510 if (err || !pages || pages > UINT_MAX)
513 khugepaged_pages_to_scan = pages;
517 static struct kobj_attribute pages_to_scan_attr =
518 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
519 pages_to_scan_store);
521 static ssize_t pages_collapsed_show(struct kobject *kobj,
522 struct kobj_attribute *attr,
525 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
527 static struct kobj_attribute pages_collapsed_attr =
528 __ATTR_RO(pages_collapsed);
530 static ssize_t full_scans_show(struct kobject *kobj,
531 struct kobj_attribute *attr,
534 return sprintf(buf, "%u\n", khugepaged_full_scans);
536 static struct kobj_attribute full_scans_attr =
537 __ATTR_RO(full_scans);
539 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
540 struct kobj_attribute *attr, char *buf)
542 return single_flag_show(kobj, attr, buf,
543 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
545 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
546 struct kobj_attribute *attr,
547 const char *buf, size_t count)
549 return single_flag_store(kobj, attr, buf, count,
550 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
552 static struct kobj_attribute khugepaged_defrag_attr =
553 __ATTR(defrag, 0644, khugepaged_defrag_show,
554 khugepaged_defrag_store);
557 * max_ptes_none controls if khugepaged should collapse hugepages over
558 * any unmapped ptes in turn potentially increasing the memory
559 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
560 * reduce the available free memory in the system as it
561 * runs. Increasing max_ptes_none will instead potentially reduce the
562 * free memory in the system during the khugepaged scan.
564 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
565 struct kobj_attribute *attr,
568 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
570 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
571 struct kobj_attribute *attr,
572 const char *buf, size_t count)
575 unsigned long max_ptes_none;
577 err = kstrtoul(buf, 10, &max_ptes_none);
578 if (err || max_ptes_none > HPAGE_PMD_NR-1)
581 khugepaged_max_ptes_none = max_ptes_none;
585 static struct kobj_attribute khugepaged_max_ptes_none_attr =
586 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
587 khugepaged_max_ptes_none_store);
589 static struct attribute *khugepaged_attr[] = {
590 &khugepaged_defrag_attr.attr,
591 &khugepaged_max_ptes_none_attr.attr,
592 &pages_to_scan_attr.attr,
593 &pages_collapsed_attr.attr,
594 &full_scans_attr.attr,
595 &scan_sleep_millisecs_attr.attr,
596 &alloc_sleep_millisecs_attr.attr,
600 static struct attribute_group khugepaged_attr_group = {
601 .attrs = khugepaged_attr,
602 .name = "khugepaged",
605 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
609 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
610 if (unlikely(!*hugepage_kobj)) {
611 pr_err("failed to create transparent hugepage kobject\n");
615 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
617 pr_err("failed to register transparent hugepage group\n");
621 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
623 pr_err("failed to register transparent hugepage group\n");
624 goto remove_hp_group;
630 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
632 kobject_put(*hugepage_kobj);
636 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
638 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
639 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
640 kobject_put(hugepage_kobj);
643 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
648 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
651 #endif /* CONFIG_SYSFS */
653 static int __init hugepage_init(void)
656 struct kobject *hugepage_kobj;
658 if (!has_transparent_hugepage()) {
659 transparent_hugepage_flags = 0;
663 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
664 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
666 * hugepages can't be allocated by the buddy allocator
668 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
670 * we use page->mapping and page->index in second tail page
671 * as list_head: assuming THP order >= 2
673 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
675 err = hugepage_init_sysfs(&hugepage_kobj);
679 err = khugepaged_slab_init();
683 err = register_shrinker(&huge_zero_page_shrinker);
685 goto err_hzp_shrinker;
686 err = register_shrinker(&deferred_split_shrinker);
688 goto err_split_shrinker;
691 * By default disable transparent hugepages on smaller systems,
692 * where the extra memory used could hurt more than TLB overhead
693 * is likely to save. The admin can still enable it through /sys.
695 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
696 transparent_hugepage_flags = 0;
700 err = start_stop_khugepaged();
706 unregister_shrinker(&deferred_split_shrinker);
708 unregister_shrinker(&huge_zero_page_shrinker);
710 khugepaged_slab_exit();
712 hugepage_exit_sysfs(hugepage_kobj);
716 subsys_initcall(hugepage_init);
718 static int __init setup_transparent_hugepage(char *str)
723 if (!strcmp(str, "always")) {
724 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
725 &transparent_hugepage_flags);
726 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
727 &transparent_hugepage_flags);
729 } else if (!strcmp(str, "madvise")) {
730 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
731 &transparent_hugepage_flags);
732 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
733 &transparent_hugepage_flags);
735 } else if (!strcmp(str, "never")) {
736 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
737 &transparent_hugepage_flags);
738 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
739 &transparent_hugepage_flags);
744 pr_warn("transparent_hugepage= cannot parse, ignored\n");
747 __setup("transparent_hugepage=", setup_transparent_hugepage);
749 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
751 if (likely(vma->vm_flags & VM_WRITE))
752 pmd = pmd_mkwrite(pmd);
756 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
759 entry = mk_pmd(page, prot);
760 entry = pmd_mkhuge(entry);
764 static inline struct list_head *page_deferred_list(struct page *page)
767 * ->lru in the tail pages is occupied by compound_head.
768 * Let's use ->mapping + ->index in the second tail page as list_head.
770 return (struct list_head *)&page[2].mapping;
773 void prep_transhuge_page(struct page *page)
776 * we use page->mapping and page->indexlru in second tail page
777 * as list_head: assuming THP order >= 2
780 INIT_LIST_HEAD(page_deferred_list(page));
781 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
784 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
785 struct vm_area_struct *vma,
786 unsigned long address, pmd_t *pmd,
787 struct page *page, gfp_t gfp,
790 struct mem_cgroup *memcg;
793 unsigned long haddr = address & HPAGE_PMD_MASK;
795 VM_BUG_ON_PAGE(!PageCompound(page), page);
797 if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) {
799 count_vm_event(THP_FAULT_FALLBACK);
800 return VM_FAULT_FALLBACK;
803 pgtable = pte_alloc_one(mm, haddr);
804 if (unlikely(!pgtable)) {
805 mem_cgroup_cancel_charge(page, memcg, true);
810 clear_huge_page(page, haddr, HPAGE_PMD_NR);
812 * The memory barrier inside __SetPageUptodate makes sure that
813 * clear_huge_page writes become visible before the set_pmd_at()
816 __SetPageUptodate(page);
818 ptl = pmd_lock(mm, pmd);
819 if (unlikely(!pmd_none(*pmd))) {
821 mem_cgroup_cancel_charge(page, memcg, true);
823 pte_free(mm, pgtable);
827 /* Deliver the page fault to userland */
828 if (userfaultfd_missing(vma)) {
832 mem_cgroup_cancel_charge(page, memcg, true);
834 pte_free(mm, pgtable);
835 ret = handle_userfault(vma, address, flags,
837 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
841 entry = mk_huge_pmd(page, vma->vm_page_prot);
842 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
843 page_add_new_anon_rmap(page, vma, haddr, true);
844 mem_cgroup_commit_charge(page, memcg, false, true);
845 lru_cache_add_active_or_unevictable(page, vma);
846 pgtable_trans_huge_deposit(mm, pmd, pgtable);
847 set_pmd_at(mm, haddr, pmd, entry);
848 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
849 atomic_long_inc(&mm->nr_ptes);
851 count_vm_event(THP_FAULT_ALLOC);
857 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
859 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_RECLAIM)) | extra_gfp;
862 /* Caller must hold page table lock. */
863 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
864 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
865 struct page *zero_page)
870 entry = mk_pmd(zero_page, vma->vm_page_prot);
871 entry = pmd_mkhuge(entry);
873 pgtable_trans_huge_deposit(mm, pmd, pgtable);
874 set_pmd_at(mm, haddr, pmd, entry);
875 atomic_long_inc(&mm->nr_ptes);
879 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
880 unsigned long address, pmd_t *pmd,
885 unsigned long haddr = address & HPAGE_PMD_MASK;
887 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
888 return VM_FAULT_FALLBACK;
889 if (unlikely(anon_vma_prepare(vma)))
891 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
893 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
894 transparent_hugepage_use_zero_page()) {
897 struct page *zero_page;
900 pgtable = pte_alloc_one(mm, haddr);
901 if (unlikely(!pgtable))
903 zero_page = get_huge_zero_page();
904 if (unlikely(!zero_page)) {
905 pte_free(mm, pgtable);
906 count_vm_event(THP_FAULT_FALLBACK);
907 return VM_FAULT_FALLBACK;
909 ptl = pmd_lock(mm, pmd);
912 if (pmd_none(*pmd)) {
913 if (userfaultfd_missing(vma)) {
915 ret = handle_userfault(vma, address, flags,
917 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
919 set_huge_zero_page(pgtable, mm, vma,
928 pte_free(mm, pgtable);
929 put_huge_zero_page();
933 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
934 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
935 if (unlikely(!page)) {
936 count_vm_event(THP_FAULT_FALLBACK);
937 return VM_FAULT_FALLBACK;
939 prep_transhuge_page(page);
940 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
944 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
945 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
947 struct mm_struct *mm = vma->vm_mm;
951 ptl = pmd_lock(mm, pmd);
952 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
953 if (pfn_t_devmap(pfn))
954 entry = pmd_mkdevmap(entry);
956 entry = pmd_mkyoung(pmd_mkdirty(entry));
957 entry = maybe_pmd_mkwrite(entry, vma);
959 set_pmd_at(mm, addr, pmd, entry);
960 update_mmu_cache_pmd(vma, addr, pmd);
964 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
965 pmd_t *pmd, pfn_t pfn, bool write)
967 pgprot_t pgprot = vma->vm_page_prot;
969 * If we had pmd_special, we could avoid all these restrictions,
970 * but we need to be consistent with PTEs and architectures that
971 * can't support a 'special' bit.
973 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
974 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
975 (VM_PFNMAP|VM_MIXEDMAP));
976 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
977 BUG_ON(!pfn_t_devmap(pfn));
979 if (addr < vma->vm_start || addr >= vma->vm_end)
980 return VM_FAULT_SIGBUS;
981 if (track_pfn_insert(vma, &pgprot, pfn))
982 return VM_FAULT_SIGBUS;
983 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
984 return VM_FAULT_NOPAGE;
987 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
993 * We should set the dirty bit only for FOLL_WRITE but for now
994 * the dirty bit in the pmd is meaningless. And if the dirty
995 * bit will become meaningful and we'll only set it with
996 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
997 * set the young bit, instead of the current set_pmd_at.
999 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1000 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1002 update_mmu_cache_pmd(vma, addr, pmd);
1005 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1006 pmd_t *pmd, int flags)
1008 unsigned long pfn = pmd_pfn(*pmd);
1009 struct mm_struct *mm = vma->vm_mm;
1010 struct dev_pagemap *pgmap;
1013 assert_spin_locked(pmd_lockptr(mm, pmd));
1015 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1018 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1023 if (flags & FOLL_TOUCH)
1024 touch_pmd(vma, addr, pmd);
1027 * device mapped pages can only be returned if the
1028 * caller will manage the page reference count.
1030 if (!(flags & FOLL_GET))
1031 return ERR_PTR(-EEXIST);
1033 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1034 pgmap = get_dev_pagemap(pfn, NULL);
1036 return ERR_PTR(-EFAULT);
1037 page = pfn_to_page(pfn);
1039 put_dev_pagemap(pgmap);
1044 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1045 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1046 struct vm_area_struct *vma)
1048 spinlock_t *dst_ptl, *src_ptl;
1049 struct page *src_page;
1051 pgtable_t pgtable = NULL;
1054 if (!vma_is_dax(vma)) {
1056 pgtable = pte_alloc_one(dst_mm, addr);
1057 if (unlikely(!pgtable))
1061 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1062 src_ptl = pmd_lockptr(src_mm, src_pmd);
1063 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1067 if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
1068 pte_free(dst_mm, pgtable);
1072 * When page table lock is held, the huge zero pmd should not be
1073 * under splitting since we don't split the page itself, only pmd to
1076 if (is_huge_zero_pmd(pmd)) {
1077 struct page *zero_page;
1079 * get_huge_zero_page() will never allocate a new page here,
1080 * since we already have a zero page to copy. It just takes a
1083 zero_page = get_huge_zero_page();
1084 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1090 if (!vma_is_dax(vma)) {
1091 /* thp accounting separate from pmd_devmap accounting */
1092 src_page = pmd_page(pmd);
1093 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1095 page_dup_rmap(src_page, true);
1096 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1097 atomic_long_inc(&dst_mm->nr_ptes);
1098 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1101 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1102 pmd = pmd_mkold(pmd_wrprotect(pmd));
1103 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1107 spin_unlock(src_ptl);
1108 spin_unlock(dst_ptl);
1113 void huge_pmd_set_accessed(struct mm_struct *mm,
1114 struct vm_area_struct *vma,
1115 unsigned long address,
1116 pmd_t *pmd, pmd_t orig_pmd,
1121 unsigned long haddr;
1123 ptl = pmd_lock(mm, pmd);
1124 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1127 entry = pmd_mkyoung(orig_pmd);
1128 haddr = address & HPAGE_PMD_MASK;
1129 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1130 update_mmu_cache_pmd(vma, address, pmd);
1136 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1137 struct vm_area_struct *vma,
1138 unsigned long address,
1139 pmd_t *pmd, pmd_t orig_pmd,
1141 unsigned long haddr)
1143 struct mem_cgroup *memcg;
1148 struct page **pages;
1149 unsigned long mmun_start; /* For mmu_notifiers */
1150 unsigned long mmun_end; /* For mmu_notifiers */
1152 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1154 if (unlikely(!pages)) {
1155 ret |= VM_FAULT_OOM;
1159 for (i = 0; i < HPAGE_PMD_NR; i++) {
1160 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1162 vma, address, page_to_nid(page));
1163 if (unlikely(!pages[i] ||
1164 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1169 memcg = (void *)page_private(pages[i]);
1170 set_page_private(pages[i], 0);
1171 mem_cgroup_cancel_charge(pages[i], memcg,
1176 ret |= VM_FAULT_OOM;
1179 set_page_private(pages[i], (unsigned long)memcg);
1182 for (i = 0; i < HPAGE_PMD_NR; i++) {
1183 copy_user_highpage(pages[i], page + i,
1184 haddr + PAGE_SIZE * i, vma);
1185 __SetPageUptodate(pages[i]);
1190 mmun_end = haddr + HPAGE_PMD_SIZE;
1191 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1193 ptl = pmd_lock(mm, pmd);
1194 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1195 goto out_free_pages;
1196 VM_BUG_ON_PAGE(!PageHead(page), page);
1198 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1199 /* leave pmd empty until pte is filled */
1201 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1202 pmd_populate(mm, &_pmd, pgtable);
1204 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1206 entry = mk_pte(pages[i], vma->vm_page_prot);
1207 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1208 memcg = (void *)page_private(pages[i]);
1209 set_page_private(pages[i], 0);
1210 page_add_new_anon_rmap(pages[i], vma, haddr, false);
1211 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1212 lru_cache_add_active_or_unevictable(pages[i], vma);
1213 pte = pte_offset_map(&_pmd, haddr);
1214 VM_BUG_ON(!pte_none(*pte));
1215 set_pte_at(mm, haddr, pte, entry);
1220 smp_wmb(); /* make pte visible before pmd */
1221 pmd_populate(mm, pmd, pgtable);
1222 page_remove_rmap(page, true);
1225 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1227 ret |= VM_FAULT_WRITE;
1235 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1236 for (i = 0; i < HPAGE_PMD_NR; i++) {
1237 memcg = (void *)page_private(pages[i]);
1238 set_page_private(pages[i], 0);
1239 mem_cgroup_cancel_charge(pages[i], memcg, false);
1246 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1247 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1251 struct page *page = NULL, *new_page;
1252 struct mem_cgroup *memcg;
1253 unsigned long haddr;
1254 unsigned long mmun_start; /* For mmu_notifiers */
1255 unsigned long mmun_end; /* For mmu_notifiers */
1256 gfp_t huge_gfp; /* for allocation and charge */
1258 ptl = pmd_lockptr(mm, pmd);
1259 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1260 haddr = address & HPAGE_PMD_MASK;
1261 if (is_huge_zero_pmd(orig_pmd))
1264 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1267 page = pmd_page(orig_pmd);
1268 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1270 * We can only reuse the page if nobody else maps the huge page or it's
1271 * part. We can do it by checking page_mapcount() on each sub-page, but
1273 * The cheaper way is to check page_count() to be equal 1: every
1274 * mapcount takes page reference reference, so this way we can
1275 * guarantee, that the PMD is the only mapping.
1276 * This can give false negative if somebody pinned the page, but that's
1279 if (page_mapcount(page) == 1 && page_count(page) == 1) {
1281 entry = pmd_mkyoung(orig_pmd);
1282 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1283 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1284 update_mmu_cache_pmd(vma, address, pmd);
1285 ret |= VM_FAULT_WRITE;
1291 if (transparent_hugepage_enabled(vma) &&
1292 !transparent_hugepage_debug_cow()) {
1293 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1294 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1298 if (likely(new_page)) {
1299 prep_transhuge_page(new_page);
1302 split_huge_pmd(vma, pmd, address);
1303 ret |= VM_FAULT_FALLBACK;
1305 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1306 pmd, orig_pmd, page, haddr);
1307 if (ret & VM_FAULT_OOM) {
1308 split_huge_pmd(vma, pmd, address);
1309 ret |= VM_FAULT_FALLBACK;
1313 count_vm_event(THP_FAULT_FALLBACK);
1317 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg,
1321 split_huge_pmd(vma, pmd, address);
1324 split_huge_pmd(vma, pmd, address);
1325 ret |= VM_FAULT_FALLBACK;
1326 count_vm_event(THP_FAULT_FALLBACK);
1330 count_vm_event(THP_FAULT_ALLOC);
1333 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1335 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1336 __SetPageUptodate(new_page);
1339 mmun_end = haddr + HPAGE_PMD_SIZE;
1340 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1345 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1347 mem_cgroup_cancel_charge(new_page, memcg, true);
1352 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1353 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1354 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1355 page_add_new_anon_rmap(new_page, vma, haddr, true);
1356 mem_cgroup_commit_charge(new_page, memcg, false, true);
1357 lru_cache_add_active_or_unevictable(new_page, vma);
1358 set_pmd_at(mm, haddr, pmd, entry);
1359 update_mmu_cache_pmd(vma, address, pmd);
1361 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1362 put_huge_zero_page();
1364 VM_BUG_ON_PAGE(!PageHead(page), page);
1365 page_remove_rmap(page, true);
1368 ret |= VM_FAULT_WRITE;
1372 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1380 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1385 struct mm_struct *mm = vma->vm_mm;
1386 struct page *page = NULL;
1388 assert_spin_locked(pmd_lockptr(mm, pmd));
1390 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1393 /* Avoid dumping huge zero page */
1394 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1395 return ERR_PTR(-EFAULT);
1397 /* Full NUMA hinting faults to serialise migration in fault paths */
1398 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1401 page = pmd_page(*pmd);
1402 VM_BUG_ON_PAGE(!PageHead(page), page);
1403 if (flags & FOLL_TOUCH)
1404 touch_pmd(vma, addr, pmd);
1405 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1407 * We don't mlock() pte-mapped THPs. This way we can avoid
1408 * leaking mlocked pages into non-VM_LOCKED VMAs.
1410 * In most cases the pmd is the only mapping of the page as we
1411 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1412 * writable private mappings in populate_vma_page_range().
1414 * The only scenario when we have the page shared here is if we
1415 * mlocking read-only mapping shared over fork(). We skip
1416 * mlocking such pages.
1418 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) &&
1419 page->mapping && trylock_page(page)) {
1422 mlock_vma_page(page);
1426 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1427 VM_BUG_ON_PAGE(!PageCompound(page), page);
1428 if (flags & FOLL_GET)
1435 /* NUMA hinting page fault entry point for trans huge pmds */
1436 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1437 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1440 struct anon_vma *anon_vma = NULL;
1442 unsigned long haddr = addr & HPAGE_PMD_MASK;
1443 int page_nid = -1, this_nid = numa_node_id();
1444 int target_nid, last_cpupid = -1;
1446 bool migrated = false;
1450 /* A PROT_NONE fault should not end up here */
1451 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1453 ptl = pmd_lock(mm, pmdp);
1454 if (unlikely(!pmd_same(pmd, *pmdp)))
1458 * If there are potential migrations, wait for completion and retry
1459 * without disrupting NUMA hinting information. Do not relock and
1460 * check_same as the page may no longer be mapped.
1462 if (unlikely(pmd_trans_migrating(*pmdp))) {
1463 page = pmd_page(*pmdp);
1465 wait_on_page_locked(page);
1469 page = pmd_page(pmd);
1470 BUG_ON(is_huge_zero_page(page));
1471 page_nid = page_to_nid(page);
1472 last_cpupid = page_cpupid_last(page);
1473 count_vm_numa_event(NUMA_HINT_FAULTS);
1474 if (page_nid == this_nid) {
1475 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1476 flags |= TNF_FAULT_LOCAL;
1479 /* See similar comment in do_numa_page for explanation */
1480 if (!(vma->vm_flags & VM_WRITE))
1481 flags |= TNF_NO_GROUP;
1484 * Acquire the page lock to serialise THP migrations but avoid dropping
1485 * page_table_lock if at all possible
1487 page_locked = trylock_page(page);
1488 target_nid = mpol_misplaced(page, vma, haddr);
1489 if (target_nid == -1) {
1490 /* If the page was locked, there are no parallel migrations */
1495 /* Migration could have started since the pmd_trans_migrating check */
1498 wait_on_page_locked(page);
1504 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1505 * to serialises splits
1509 anon_vma = page_lock_anon_vma_read(page);
1511 /* Confirm the PMD did not change while page_table_lock was released */
1513 if (unlikely(!pmd_same(pmd, *pmdp))) {
1520 /* Bail if we fail to protect against THP splits for any reason */
1521 if (unlikely(!anon_vma)) {
1528 * Migrate the THP to the requested node, returns with page unlocked
1529 * and access rights restored.
1532 migrated = migrate_misplaced_transhuge_page(mm, vma,
1533 pmdp, pmd, addr, page, target_nid);
1535 flags |= TNF_MIGRATED;
1536 page_nid = target_nid;
1538 flags |= TNF_MIGRATE_FAIL;
1542 BUG_ON(!PageLocked(page));
1543 was_writable = pmd_write(pmd);
1544 pmd = pmd_modify(pmd, vma->vm_page_prot);
1545 pmd = pmd_mkyoung(pmd);
1547 pmd = pmd_mkwrite(pmd);
1548 set_pmd_at(mm, haddr, pmdp, pmd);
1549 update_mmu_cache_pmd(vma, addr, pmdp);
1556 page_unlock_anon_vma_read(anon_vma);
1559 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1564 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1565 pmd_t *pmd, unsigned long addr, unsigned long next)
1571 struct mm_struct *mm = tlb->mm;
1574 ptl = pmd_trans_huge_lock(pmd, vma);
1579 if (is_huge_zero_pmd(orig_pmd)) {
1584 page = pmd_page(orig_pmd);
1586 * If other processes are mapping this page, we couldn't discard
1587 * the page unless they all do MADV_FREE so let's skip the page.
1589 if (page_mapcount(page) != 1)
1592 if (!trylock_page(page))
1596 * If user want to discard part-pages of THP, split it so MADV_FREE
1597 * will deactivate only them.
1599 if (next - addr != HPAGE_PMD_SIZE) {
1602 if (split_huge_page(page)) {
1613 if (PageDirty(page))
1614 ClearPageDirty(page);
1617 if (PageActive(page))
1618 deactivate_page(page);
1620 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1621 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1623 orig_pmd = pmd_mkold(orig_pmd);
1624 orig_pmd = pmd_mkclean(orig_pmd);
1626 set_pmd_at(mm, addr, pmd, orig_pmd);
1627 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1636 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1637 pmd_t *pmd, unsigned long addr)
1642 ptl = __pmd_trans_huge_lock(pmd, vma);
1646 * For architectures like ppc64 we look at deposited pgtable
1647 * when calling pmdp_huge_get_and_clear. So do the
1648 * pgtable_trans_huge_withdraw after finishing pmdp related
1651 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1653 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1654 if (vma_is_dax(vma)) {
1656 if (is_huge_zero_pmd(orig_pmd))
1657 put_huge_zero_page();
1658 } else if (is_huge_zero_pmd(orig_pmd)) {
1659 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1660 atomic_long_dec(&tlb->mm->nr_ptes);
1662 put_huge_zero_page();
1664 struct page *page = pmd_page(orig_pmd);
1665 page_remove_rmap(page, true);
1666 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1667 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1668 VM_BUG_ON_PAGE(!PageHead(page), page);
1669 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1670 atomic_long_dec(&tlb->mm->nr_ptes);
1672 tlb_remove_page(tlb, page);
1677 bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1678 unsigned long old_addr,
1679 unsigned long new_addr, unsigned long old_end,
1680 pmd_t *old_pmd, pmd_t *new_pmd)
1682 spinlock_t *old_ptl, *new_ptl;
1685 struct mm_struct *mm = vma->vm_mm;
1687 if ((old_addr & ~HPAGE_PMD_MASK) ||
1688 (new_addr & ~HPAGE_PMD_MASK) ||
1689 old_end - old_addr < HPAGE_PMD_SIZE ||
1690 (new_vma->vm_flags & VM_NOHUGEPAGE))
1694 * The destination pmd shouldn't be established, free_pgtables()
1695 * should have release it.
1697 if (WARN_ON(!pmd_none(*new_pmd))) {
1698 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1703 * We don't have to worry about the ordering of src and dst
1704 * ptlocks because exclusive mmap_sem prevents deadlock.
1706 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1708 new_ptl = pmd_lockptr(mm, new_pmd);
1709 if (new_ptl != old_ptl)
1710 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1711 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1712 VM_BUG_ON(!pmd_none(*new_pmd));
1714 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1715 vma_is_anonymous(vma)) {
1717 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1718 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1720 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1721 if (new_ptl != old_ptl)
1722 spin_unlock(new_ptl);
1723 spin_unlock(old_ptl);
1731 * - 0 if PMD could not be locked
1732 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1733 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1735 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1736 unsigned long addr, pgprot_t newprot, int prot_numa)
1738 struct mm_struct *mm = vma->vm_mm;
1742 ptl = __pmd_trans_huge_lock(pmd, vma);
1745 bool preserve_write = prot_numa && pmd_write(*pmd);
1749 * Avoid trapping faults against the zero page. The read-only
1750 * data is likely to be read-cached on the local CPU and
1751 * local/remote hits to the zero page are not interesting.
1753 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1758 if (!prot_numa || !pmd_protnone(*pmd)) {
1759 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1760 entry = pmd_modify(entry, newprot);
1762 entry = pmd_mkwrite(entry);
1764 set_pmd_at(mm, addr, pmd, entry);
1765 BUG_ON(!preserve_write && pmd_write(entry));
1774 * Returns true if a given pmd maps a thp, false otherwise.
1776 * Note that if it returns true, this routine returns without unlocking page
1777 * table lock. So callers must unlock it.
1779 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1782 ptl = pmd_lock(vma->vm_mm, pmd);
1783 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1789 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1791 int hugepage_madvise(struct vm_area_struct *vma,
1792 unsigned long *vm_flags, int advice)
1798 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1799 * can't handle this properly after s390_enable_sie, so we simply
1800 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1802 if (mm_has_pgste(vma->vm_mm))
1806 * Be somewhat over-protective like KSM for now!
1808 if (*vm_flags & VM_NO_THP)
1810 *vm_flags &= ~VM_NOHUGEPAGE;
1811 *vm_flags |= VM_HUGEPAGE;
1813 * If the vma become good for khugepaged to scan,
1814 * register it here without waiting a page fault that
1815 * may not happen any time soon.
1817 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1820 case MADV_NOHUGEPAGE:
1822 * Be somewhat over-protective like KSM for now!
1824 if (*vm_flags & VM_NO_THP)
1826 *vm_flags &= ~VM_HUGEPAGE;
1827 *vm_flags |= VM_NOHUGEPAGE;
1829 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1830 * this vma even if we leave the mm registered in khugepaged if
1831 * it got registered before VM_NOHUGEPAGE was set.
1839 static int __init khugepaged_slab_init(void)
1841 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1842 sizeof(struct mm_slot),
1843 __alignof__(struct mm_slot), 0, NULL);
1850 static void __init khugepaged_slab_exit(void)
1852 kmem_cache_destroy(mm_slot_cache);
1855 static inline struct mm_slot *alloc_mm_slot(void)
1857 if (!mm_slot_cache) /* initialization failed */
1859 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1862 static inline void free_mm_slot(struct mm_slot *mm_slot)
1864 kmem_cache_free(mm_slot_cache, mm_slot);
1867 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1869 struct mm_slot *mm_slot;
1871 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1872 if (mm == mm_slot->mm)
1878 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1879 struct mm_slot *mm_slot)
1882 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1885 static inline int khugepaged_test_exit(struct mm_struct *mm)
1887 return atomic_read(&mm->mm_users) == 0;
1890 int __khugepaged_enter(struct mm_struct *mm)
1892 struct mm_slot *mm_slot;
1895 mm_slot = alloc_mm_slot();
1899 /* __khugepaged_exit() must not run from under us */
1900 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1901 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1902 free_mm_slot(mm_slot);
1906 spin_lock(&khugepaged_mm_lock);
1907 insert_to_mm_slots_hash(mm, mm_slot);
1909 * Insert just behind the scanning cursor, to let the area settle
1912 wakeup = list_empty(&khugepaged_scan.mm_head);
1913 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1914 spin_unlock(&khugepaged_mm_lock);
1916 atomic_inc(&mm->mm_count);
1918 wake_up_interruptible(&khugepaged_wait);
1923 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1924 unsigned long vm_flags)
1926 unsigned long hstart, hend;
1929 * Not yet faulted in so we will register later in the
1930 * page fault if needed.
1934 /* khugepaged not yet working on file or special mappings */
1936 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
1937 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1938 hend = vma->vm_end & HPAGE_PMD_MASK;
1940 return khugepaged_enter(vma, vm_flags);
1944 void __khugepaged_exit(struct mm_struct *mm)
1946 struct mm_slot *mm_slot;
1949 spin_lock(&khugepaged_mm_lock);
1950 mm_slot = get_mm_slot(mm);
1951 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1952 hash_del(&mm_slot->hash);
1953 list_del(&mm_slot->mm_node);
1956 spin_unlock(&khugepaged_mm_lock);
1959 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1960 free_mm_slot(mm_slot);
1962 } else if (mm_slot) {
1964 * This is required to serialize against
1965 * khugepaged_test_exit() (which is guaranteed to run
1966 * under mmap sem read mode). Stop here (after we
1967 * return all pagetables will be destroyed) until
1968 * khugepaged has finished working on the pagetables
1969 * under the mmap_sem.
1971 down_write(&mm->mmap_sem);
1972 up_write(&mm->mmap_sem);
1976 static void release_pte_page(struct page *page)
1978 /* 0 stands for page_is_file_cache(page) == false */
1979 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1981 putback_lru_page(page);
1984 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1986 while (--_pte >= pte) {
1987 pte_t pteval = *_pte;
1988 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
1989 release_pte_page(pte_page(pteval));
1993 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1994 unsigned long address,
1997 struct page *page = NULL;
1999 int none_or_zero = 0, result = 0;
2000 bool referenced = false, writable = false;
2002 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2003 _pte++, address += PAGE_SIZE) {
2004 pte_t pteval = *_pte;
2005 if (pte_none(pteval) || (pte_present(pteval) &&
2006 is_zero_pfn(pte_pfn(pteval)))) {
2007 if (!userfaultfd_armed(vma) &&
2008 ++none_or_zero <= khugepaged_max_ptes_none) {
2011 result = SCAN_EXCEED_NONE_PTE;
2015 if (!pte_present(pteval)) {
2016 result = SCAN_PTE_NON_PRESENT;
2019 page = vm_normal_page(vma, address, pteval);
2020 if (unlikely(!page)) {
2021 result = SCAN_PAGE_NULL;
2025 VM_BUG_ON_PAGE(PageCompound(page), page);
2026 VM_BUG_ON_PAGE(!PageAnon(page), page);
2027 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2030 * We can do it before isolate_lru_page because the
2031 * page can't be freed from under us. NOTE: PG_lock
2032 * is needed to serialize against split_huge_page
2033 * when invoked from the VM.
2035 if (!trylock_page(page)) {
2036 result = SCAN_PAGE_LOCK;
2041 * cannot use mapcount: can't collapse if there's a gup pin.
2042 * The page must only be referenced by the scanned process
2043 * and page swap cache.
2045 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2047 result = SCAN_PAGE_COUNT;
2050 if (pte_write(pteval)) {
2053 if (PageSwapCache(page) && !reuse_swap_page(page)) {
2055 result = SCAN_SWAP_CACHE_PAGE;
2059 * Page is not in the swap cache. It can be collapsed
2065 * Isolate the page to avoid collapsing an hugepage
2066 * currently in use by the VM.
2068 if (isolate_lru_page(page)) {
2070 result = SCAN_DEL_PAGE_LRU;
2073 /* 0 stands for page_is_file_cache(page) == false */
2074 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2075 VM_BUG_ON_PAGE(!PageLocked(page), page);
2076 VM_BUG_ON_PAGE(PageLRU(page), page);
2078 /* If there is no mapped pte young don't collapse the page */
2079 if (pte_young(pteval) ||
2080 page_is_young(page) || PageReferenced(page) ||
2081 mmu_notifier_test_young(vma->vm_mm, address))
2084 if (likely(writable)) {
2085 if (likely(referenced)) {
2086 result = SCAN_SUCCEED;
2087 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2088 referenced, writable, result);
2092 result = SCAN_PAGE_RO;
2096 release_pte_pages(pte, _pte);
2097 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2098 referenced, writable, result);
2102 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2103 struct vm_area_struct *vma,
2104 unsigned long address,
2108 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2109 pte_t pteval = *_pte;
2110 struct page *src_page;
2112 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2113 clear_user_highpage(page, address);
2114 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2115 if (is_zero_pfn(pte_pfn(pteval))) {
2117 * ptl mostly unnecessary.
2121 * paravirt calls inside pte_clear here are
2124 pte_clear(vma->vm_mm, address, _pte);
2128 src_page = pte_page(pteval);
2129 copy_user_highpage(page, src_page, address, vma);
2130 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2131 release_pte_page(src_page);
2133 * ptl mostly unnecessary, but preempt has to
2134 * be disabled to update the per-cpu stats
2135 * inside page_remove_rmap().
2139 * paravirt calls inside pte_clear here are
2142 pte_clear(vma->vm_mm, address, _pte);
2143 page_remove_rmap(src_page, false);
2145 free_page_and_swap_cache(src_page);
2148 address += PAGE_SIZE;
2153 static void khugepaged_alloc_sleep(void)
2157 add_wait_queue(&khugepaged_wait, &wait);
2158 freezable_schedule_timeout_interruptible(
2159 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2160 remove_wait_queue(&khugepaged_wait, &wait);
2163 static int khugepaged_node_load[MAX_NUMNODES];
2165 static bool khugepaged_scan_abort(int nid)
2170 * If zone_reclaim_mode is disabled, then no extra effort is made to
2171 * allocate memory locally.
2173 if (!zone_reclaim_mode)
2176 /* If there is a count for this node already, it must be acceptable */
2177 if (khugepaged_node_load[nid])
2180 for (i = 0; i < MAX_NUMNODES; i++) {
2181 if (!khugepaged_node_load[i])
2183 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2190 static int khugepaged_find_target_node(void)
2192 static int last_khugepaged_target_node = NUMA_NO_NODE;
2193 int nid, target_node = 0, max_value = 0;
2195 /* find first node with max normal pages hit */
2196 for (nid = 0; nid < MAX_NUMNODES; nid++)
2197 if (khugepaged_node_load[nid] > max_value) {
2198 max_value = khugepaged_node_load[nid];
2202 /* do some balance if several nodes have the same hit record */
2203 if (target_node <= last_khugepaged_target_node)
2204 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2206 if (max_value == khugepaged_node_load[nid]) {
2211 last_khugepaged_target_node = target_node;
2215 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2217 if (IS_ERR(*hpage)) {
2223 khugepaged_alloc_sleep();
2224 } else if (*hpage) {
2232 static struct page *
2233 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2234 unsigned long address, int node)
2236 VM_BUG_ON_PAGE(*hpage, *hpage);
2239 * Before allocating the hugepage, release the mmap_sem read lock.
2240 * The allocation can take potentially a long time if it involves
2241 * sync compaction, and we do not need to hold the mmap_sem during
2242 * that. We will recheck the vma after taking it again in write mode.
2244 up_read(&mm->mmap_sem);
2246 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2247 if (unlikely(!*hpage)) {
2248 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2249 *hpage = ERR_PTR(-ENOMEM);
2253 prep_transhuge_page(*hpage);
2254 count_vm_event(THP_COLLAPSE_ALLOC);
2258 static int khugepaged_find_target_node(void)
2263 static inline struct page *alloc_hugepage(int defrag)
2267 page = alloc_pages(alloc_hugepage_gfpmask(defrag, 0), HPAGE_PMD_ORDER);
2269 prep_transhuge_page(page);
2273 static struct page *khugepaged_alloc_hugepage(bool *wait)
2278 hpage = alloc_hugepage(khugepaged_defrag());
2280 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2285 khugepaged_alloc_sleep();
2287 count_vm_event(THP_COLLAPSE_ALLOC);
2288 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2293 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2296 *hpage = khugepaged_alloc_hugepage(wait);
2298 if (unlikely(!*hpage))
2304 static struct page *
2305 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2306 unsigned long address, int node)
2308 up_read(&mm->mmap_sem);
2315 static bool hugepage_vma_check(struct vm_area_struct *vma)
2317 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2318 (vma->vm_flags & VM_NOHUGEPAGE))
2320 if (!vma->anon_vma || vma->vm_ops)
2322 if (is_vma_temporary_stack(vma))
2324 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2328 static void collapse_huge_page(struct mm_struct *mm,
2329 unsigned long address,
2330 struct page **hpage,
2331 struct vm_area_struct *vma,
2337 struct page *new_page;
2338 spinlock_t *pmd_ptl, *pte_ptl;
2339 int isolated = 0, result = 0;
2340 unsigned long hstart, hend;
2341 struct mem_cgroup *memcg;
2342 unsigned long mmun_start; /* For mmu_notifiers */
2343 unsigned long mmun_end; /* For mmu_notifiers */
2346 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2348 /* Only allocate from the target node */
2349 gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2352 /* release the mmap_sem read lock. */
2353 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2355 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2359 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2360 result = SCAN_CGROUP_CHARGE_FAIL;
2365 * Prevent all access to pagetables with the exception of
2366 * gup_fast later hanlded by the ptep_clear_flush and the VM
2367 * handled by the anon_vma lock + PG_lock.
2369 down_write(&mm->mmap_sem);
2370 if (unlikely(khugepaged_test_exit(mm))) {
2371 result = SCAN_ANY_PROCESS;
2375 vma = find_vma(mm, address);
2377 result = SCAN_VMA_NULL;
2380 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2381 hend = vma->vm_end & HPAGE_PMD_MASK;
2382 if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
2383 result = SCAN_ADDRESS_RANGE;
2386 if (!hugepage_vma_check(vma)) {
2387 result = SCAN_VMA_CHECK;
2390 pmd = mm_find_pmd(mm, address);
2392 result = SCAN_PMD_NULL;
2396 anon_vma_lock_write(vma->anon_vma);
2398 pte = pte_offset_map(pmd, address);
2399 pte_ptl = pte_lockptr(mm, pmd);
2401 mmun_start = address;
2402 mmun_end = address + HPAGE_PMD_SIZE;
2403 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2404 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2406 * After this gup_fast can't run anymore. This also removes
2407 * any huge TLB entry from the CPU so we won't allow
2408 * huge and small TLB entries for the same virtual address
2409 * to avoid the risk of CPU bugs in that area.
2411 _pmd = pmdp_collapse_flush(vma, address, pmd);
2412 spin_unlock(pmd_ptl);
2413 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2416 isolated = __collapse_huge_page_isolate(vma, address, pte);
2417 spin_unlock(pte_ptl);
2419 if (unlikely(!isolated)) {
2422 BUG_ON(!pmd_none(*pmd));
2424 * We can only use set_pmd_at when establishing
2425 * hugepmds and never for establishing regular pmds that
2426 * points to regular pagetables. Use pmd_populate for that
2428 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2429 spin_unlock(pmd_ptl);
2430 anon_vma_unlock_write(vma->anon_vma);
2436 * All pages are isolated and locked so anon_vma rmap
2437 * can't run anymore.
2439 anon_vma_unlock_write(vma->anon_vma);
2441 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2443 __SetPageUptodate(new_page);
2444 pgtable = pmd_pgtable(_pmd);
2446 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2447 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2450 * spin_lock() below is not the equivalent of smp_wmb(), so
2451 * this is needed to avoid the copy_huge_page writes to become
2452 * visible after the set_pmd_at() write.
2457 BUG_ON(!pmd_none(*pmd));
2458 page_add_new_anon_rmap(new_page, vma, address, true);
2459 mem_cgroup_commit_charge(new_page, memcg, false, true);
2460 lru_cache_add_active_or_unevictable(new_page, vma);
2461 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2462 set_pmd_at(mm, address, pmd, _pmd);
2463 update_mmu_cache_pmd(vma, address, pmd);
2464 spin_unlock(pmd_ptl);
2468 khugepaged_pages_collapsed++;
2469 result = SCAN_SUCCEED;
2471 up_write(&mm->mmap_sem);
2472 trace_mm_collapse_huge_page(mm, isolated, result);
2476 trace_mm_collapse_huge_page(mm, isolated, result);
2479 mem_cgroup_cancel_charge(new_page, memcg, true);
2483 static int khugepaged_scan_pmd(struct mm_struct *mm,
2484 struct vm_area_struct *vma,
2485 unsigned long address,
2486 struct page **hpage)
2490 int ret = 0, none_or_zero = 0, result = 0;
2491 struct page *page = NULL;
2492 unsigned long _address;
2494 int node = NUMA_NO_NODE;
2495 bool writable = false, referenced = false;
2497 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2499 pmd = mm_find_pmd(mm, address);
2501 result = SCAN_PMD_NULL;
2505 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2506 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2507 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2508 _pte++, _address += PAGE_SIZE) {
2509 pte_t pteval = *_pte;
2510 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2511 if (!userfaultfd_armed(vma) &&
2512 ++none_or_zero <= khugepaged_max_ptes_none) {
2515 result = SCAN_EXCEED_NONE_PTE;
2519 if (!pte_present(pteval)) {
2520 result = SCAN_PTE_NON_PRESENT;
2523 if (pte_write(pteval))
2526 page = vm_normal_page(vma, _address, pteval);
2527 if (unlikely(!page)) {
2528 result = SCAN_PAGE_NULL;
2532 /* TODO: teach khugepaged to collapse THP mapped with pte */
2533 if (PageCompound(page)) {
2534 result = SCAN_PAGE_COMPOUND;
2539 * Record which node the original page is from and save this
2540 * information to khugepaged_node_load[].
2541 * Khupaged will allocate hugepage from the node has the max
2544 node = page_to_nid(page);
2545 if (khugepaged_scan_abort(node)) {
2546 result = SCAN_SCAN_ABORT;
2549 khugepaged_node_load[node]++;
2550 if (!PageLRU(page)) {
2551 result = SCAN_SCAN_ABORT;
2554 if (PageLocked(page)) {
2555 result = SCAN_PAGE_LOCK;
2558 if (!PageAnon(page)) {
2559 result = SCAN_PAGE_ANON;
2564 * cannot use mapcount: can't collapse if there's a gup pin.
2565 * The page must only be referenced by the scanned process
2566 * and page swap cache.
2568 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2569 result = SCAN_PAGE_COUNT;
2572 if (pte_young(pteval) ||
2573 page_is_young(page) || PageReferenced(page) ||
2574 mmu_notifier_test_young(vma->vm_mm, address))
2579 result = SCAN_SUCCEED;
2582 result = SCAN_NO_REFERENCED_PAGE;
2585 result = SCAN_PAGE_RO;
2588 pte_unmap_unlock(pte, ptl);
2590 node = khugepaged_find_target_node();
2591 /* collapse_huge_page will return with the mmap_sem released */
2592 collapse_huge_page(mm, address, hpage, vma, node);
2595 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
2596 none_or_zero, result);
2600 static void collect_mm_slot(struct mm_slot *mm_slot)
2602 struct mm_struct *mm = mm_slot->mm;
2604 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2606 if (khugepaged_test_exit(mm)) {
2608 hash_del(&mm_slot->hash);
2609 list_del(&mm_slot->mm_node);
2612 * Not strictly needed because the mm exited already.
2614 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2617 /* khugepaged_mm_lock actually not necessary for the below */
2618 free_mm_slot(mm_slot);
2623 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2624 struct page **hpage)
2625 __releases(&khugepaged_mm_lock)
2626 __acquires(&khugepaged_mm_lock)
2628 struct mm_slot *mm_slot;
2629 struct mm_struct *mm;
2630 struct vm_area_struct *vma;
2634 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2636 if (khugepaged_scan.mm_slot)
2637 mm_slot = khugepaged_scan.mm_slot;
2639 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2640 struct mm_slot, mm_node);
2641 khugepaged_scan.address = 0;
2642 khugepaged_scan.mm_slot = mm_slot;
2644 spin_unlock(&khugepaged_mm_lock);
2647 down_read(&mm->mmap_sem);
2648 if (unlikely(khugepaged_test_exit(mm)))
2651 vma = find_vma(mm, khugepaged_scan.address);
2654 for (; vma; vma = vma->vm_next) {
2655 unsigned long hstart, hend;
2658 if (unlikely(khugepaged_test_exit(mm))) {
2662 if (!hugepage_vma_check(vma)) {
2667 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2668 hend = vma->vm_end & HPAGE_PMD_MASK;
2671 if (khugepaged_scan.address > hend)
2673 if (khugepaged_scan.address < hstart)
2674 khugepaged_scan.address = hstart;
2675 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2677 while (khugepaged_scan.address < hend) {
2680 if (unlikely(khugepaged_test_exit(mm)))
2681 goto breakouterloop;
2683 VM_BUG_ON(khugepaged_scan.address < hstart ||
2684 khugepaged_scan.address + HPAGE_PMD_SIZE >
2686 ret = khugepaged_scan_pmd(mm, vma,
2687 khugepaged_scan.address,
2689 /* move to next address */
2690 khugepaged_scan.address += HPAGE_PMD_SIZE;
2691 progress += HPAGE_PMD_NR;
2693 /* we released mmap_sem so break loop */
2694 goto breakouterloop_mmap_sem;
2695 if (progress >= pages)
2696 goto breakouterloop;
2700 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2701 breakouterloop_mmap_sem:
2703 spin_lock(&khugepaged_mm_lock);
2704 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2706 * Release the current mm_slot if this mm is about to die, or
2707 * if we scanned all vmas of this mm.
2709 if (khugepaged_test_exit(mm) || !vma) {
2711 * Make sure that if mm_users is reaching zero while
2712 * khugepaged runs here, khugepaged_exit will find
2713 * mm_slot not pointing to the exiting mm.
2715 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2716 khugepaged_scan.mm_slot = list_entry(
2717 mm_slot->mm_node.next,
2718 struct mm_slot, mm_node);
2719 khugepaged_scan.address = 0;
2721 khugepaged_scan.mm_slot = NULL;
2722 khugepaged_full_scans++;
2725 collect_mm_slot(mm_slot);
2731 static int khugepaged_has_work(void)
2733 return !list_empty(&khugepaged_scan.mm_head) &&
2734 khugepaged_enabled();
2737 static int khugepaged_wait_event(void)
2739 return !list_empty(&khugepaged_scan.mm_head) ||
2740 kthread_should_stop();
2743 static void khugepaged_do_scan(void)
2745 struct page *hpage = NULL;
2746 unsigned int progress = 0, pass_through_head = 0;
2747 unsigned int pages = khugepaged_pages_to_scan;
2750 barrier(); /* write khugepaged_pages_to_scan to local stack */
2752 while (progress < pages) {
2753 if (!khugepaged_prealloc_page(&hpage, &wait))
2758 if (unlikely(kthread_should_stop() || try_to_freeze()))
2761 spin_lock(&khugepaged_mm_lock);
2762 if (!khugepaged_scan.mm_slot)
2763 pass_through_head++;
2764 if (khugepaged_has_work() &&
2765 pass_through_head < 2)
2766 progress += khugepaged_scan_mm_slot(pages - progress,
2770 spin_unlock(&khugepaged_mm_lock);
2773 if (!IS_ERR_OR_NULL(hpage))
2777 static void khugepaged_wait_work(void)
2779 if (khugepaged_has_work()) {
2780 if (!khugepaged_scan_sleep_millisecs)
2783 wait_event_freezable_timeout(khugepaged_wait,
2784 kthread_should_stop(),
2785 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2789 if (khugepaged_enabled())
2790 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2793 static int khugepaged(void *none)
2795 struct mm_slot *mm_slot;
2798 set_user_nice(current, MAX_NICE);
2800 while (!kthread_should_stop()) {
2801 khugepaged_do_scan();
2802 khugepaged_wait_work();
2805 spin_lock(&khugepaged_mm_lock);
2806 mm_slot = khugepaged_scan.mm_slot;
2807 khugepaged_scan.mm_slot = NULL;
2809 collect_mm_slot(mm_slot);
2810 spin_unlock(&khugepaged_mm_lock);
2814 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2815 unsigned long haddr, pmd_t *pmd)
2817 struct mm_struct *mm = vma->vm_mm;
2822 /* leave pmd empty until pte is filled */
2823 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2825 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2826 pmd_populate(mm, &_pmd, pgtable);
2828 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2830 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2831 entry = pte_mkspecial(entry);
2832 pte = pte_offset_map(&_pmd, haddr);
2833 VM_BUG_ON(!pte_none(*pte));
2834 set_pte_at(mm, haddr, pte, entry);
2837 smp_wmb(); /* make pte visible before pmd */
2838 pmd_populate(mm, pmd, pgtable);
2839 put_huge_zero_page();
2842 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2843 unsigned long haddr, bool freeze)
2845 struct mm_struct *mm = vma->vm_mm;
2849 bool young, write, dirty;
2853 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2854 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2855 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2856 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
2858 count_vm_event(THP_SPLIT_PMD);
2860 if (vma_is_dax(vma)) {
2861 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2862 if (is_huge_zero_pmd(_pmd))
2863 put_huge_zero_page();
2865 } else if (is_huge_zero_pmd(*pmd)) {
2866 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2869 page = pmd_page(*pmd);
2870 VM_BUG_ON_PAGE(!page_count(page), page);
2871 atomic_add(HPAGE_PMD_NR - 1, &page->_count);
2872 write = pmd_write(*pmd);
2873 young = pmd_young(*pmd);
2874 dirty = pmd_dirty(*pmd);
2876 pmdp_huge_split_prepare(vma, haddr, pmd);
2877 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2878 pmd_populate(mm, &_pmd, pgtable);
2880 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2883 * Note that NUMA hinting access restrictions are not
2884 * transferred to avoid any possibility of altering
2885 * permissions across VMAs.
2888 swp_entry_t swp_entry;
2889 swp_entry = make_migration_entry(page + i, write);
2890 entry = swp_entry_to_pte(swp_entry);
2892 entry = mk_pte(page + i, vma->vm_page_prot);
2893 entry = maybe_mkwrite(entry, vma);
2895 entry = pte_wrprotect(entry);
2897 entry = pte_mkold(entry);
2900 SetPageDirty(page + i);
2901 pte = pte_offset_map(&_pmd, addr);
2902 BUG_ON(!pte_none(*pte));
2903 set_pte_at(mm, addr, pte, entry);
2904 atomic_inc(&page[i]._mapcount);
2909 * Set PG_double_map before dropping compound_mapcount to avoid
2910 * false-negative page_mapped().
2912 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2913 for (i = 0; i < HPAGE_PMD_NR; i++)
2914 atomic_inc(&page[i]._mapcount);
2917 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2918 /* Last compound_mapcount is gone. */
2919 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
2920 if (TestClearPageDoubleMap(page)) {
2921 /* No need in mapcount reference anymore */
2922 for (i = 0; i < HPAGE_PMD_NR; i++)
2923 atomic_dec(&page[i]._mapcount);
2927 smp_wmb(); /* make pte visible before pmd */
2929 * Up to this point the pmd is present and huge and userland has the
2930 * whole access to the hugepage during the split (which happens in
2931 * place). If we overwrite the pmd with the not-huge version pointing
2932 * to the pte here (which of course we could if all CPUs were bug
2933 * free), userland could trigger a small page size TLB miss on the
2934 * small sized TLB while the hugepage TLB entry is still established in
2935 * the huge TLB. Some CPU doesn't like that.
2936 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2937 * 383 on page 93. Intel should be safe but is also warns that it's
2938 * only safe if the permission and cache attributes of the two entries
2939 * loaded in the two TLB is identical (which should be the case here).
2940 * But it is generally safer to never allow small and huge TLB entries
2941 * for the same virtual address to be loaded simultaneously. So instead
2942 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2943 * current pmd notpresent (atomically because here the pmd_trans_huge
2944 * and pmd_trans_splitting must remain set at all times on the pmd
2945 * until the split is complete for this pmd), then we flush the SMP TLB
2946 * and finally we write the non-huge version of the pmd entry with
2949 pmdp_invalidate(vma, haddr, pmd);
2950 pmd_populate(mm, pmd, pgtable);
2953 for (i = 0; i < HPAGE_PMD_NR; i++) {
2954 page_remove_rmap(page + i, false);
2960 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2961 unsigned long address)
2964 struct mm_struct *mm = vma->vm_mm;
2965 struct page *page = NULL;
2966 unsigned long haddr = address & HPAGE_PMD_MASK;
2968 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2969 ptl = pmd_lock(mm, pmd);
2970 if (pmd_trans_huge(*pmd)) {
2971 page = pmd_page(*pmd);
2972 if (PageMlocked(page))
2976 } else if (!pmd_devmap(*pmd))
2978 __split_huge_pmd_locked(vma, pmd, haddr, false);
2981 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
2984 munlock_vma_page(page);
2990 static void split_huge_pmd_address(struct vm_area_struct *vma,
2991 unsigned long address)
2997 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2999 pgd = pgd_offset(vma->vm_mm, address);
3000 if (!pgd_present(*pgd))
3003 pud = pud_offset(pgd, address);
3004 if (!pud_present(*pud))
3007 pmd = pmd_offset(pud, address);
3008 if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)))
3011 * Caller holds the mmap_sem write mode, so a huge pmd cannot
3012 * materialize from under us.
3014 split_huge_pmd(vma, pmd, address);
3017 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3018 unsigned long start,
3023 * If the new start address isn't hpage aligned and it could
3024 * previously contain an hugepage: check if we need to split
3027 if (start & ~HPAGE_PMD_MASK &&
3028 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3029 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3030 split_huge_pmd_address(vma, start);
3033 * If the new end address isn't hpage aligned and it could
3034 * previously contain an hugepage: check if we need to split
3037 if (end & ~HPAGE_PMD_MASK &&
3038 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3039 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3040 split_huge_pmd_address(vma, end);
3043 * If we're also updating the vma->vm_next->vm_start, if the new
3044 * vm_next->vm_start isn't page aligned and it could previously
3045 * contain an hugepage: check if we need to split an huge pmd.
3047 if (adjust_next > 0) {
3048 struct vm_area_struct *next = vma->vm_next;
3049 unsigned long nstart = next->vm_start;
3050 nstart += adjust_next << PAGE_SHIFT;
3051 if (nstart & ~HPAGE_PMD_MASK &&
3052 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3053 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3054 split_huge_pmd_address(next, nstart);
3058 static void freeze_page_vma(struct vm_area_struct *vma, struct page *page,
3059 unsigned long address)
3061 unsigned long haddr = address & HPAGE_PMD_MASK;
3067 int i, nr = HPAGE_PMD_NR;
3069 /* Skip pages which doesn't belong to the VMA */
3070 if (address < vma->vm_start) {
3071 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3074 address = vma->vm_start;
3077 pgd = pgd_offset(vma->vm_mm, address);
3078 if (!pgd_present(*pgd))
3080 pud = pud_offset(pgd, address);
3081 if (!pud_present(*pud))
3083 pmd = pmd_offset(pud, address);
3084 ptl = pmd_lock(vma->vm_mm, pmd);
3085 if (!pmd_present(*pmd)) {
3089 if (pmd_trans_huge(*pmd)) {
3090 if (page == pmd_page(*pmd))
3091 __split_huge_pmd_locked(vma, pmd, haddr, true);
3097 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3098 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) {
3099 pte_t entry, swp_pte;
3100 swp_entry_t swp_entry;
3103 * We've just crossed page table boundary: need to map next one.
3104 * It can happen if THP was mremaped to non PMD-aligned address.
3106 if (unlikely(address == haddr + HPAGE_PMD_SIZE)) {
3107 pte_unmap_unlock(pte - 1, ptl);
3108 pmd = mm_find_pmd(vma->vm_mm, address);
3111 pte = pte_offset_map_lock(vma->vm_mm, pmd,
3115 if (!pte_present(*pte))
3117 if (page_to_pfn(page) != pte_pfn(*pte))
3119 flush_cache_page(vma, address, page_to_pfn(page));
3120 entry = ptep_clear_flush(vma, address, pte);
3121 if (pte_dirty(entry))
3123 swp_entry = make_migration_entry(page, pte_write(entry));
3124 swp_pte = swp_entry_to_pte(swp_entry);
3125 if (pte_soft_dirty(entry))
3126 swp_pte = pte_swp_mksoft_dirty(swp_pte);
3127 set_pte_at(vma->vm_mm, address, pte, swp_pte);
3128 page_remove_rmap(page, false);
3131 pte_unmap_unlock(pte - 1, ptl);
3134 static void freeze_page(struct anon_vma *anon_vma, struct page *page)
3136 struct anon_vma_chain *avc;
3137 pgoff_t pgoff = page_to_pgoff(page);
3139 VM_BUG_ON_PAGE(!PageHead(page), page);
3141 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff,
3142 pgoff + HPAGE_PMD_NR - 1) {
3143 unsigned long address = __vma_address(page, avc->vma);
3145 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3146 address, address + HPAGE_PMD_SIZE);
3147 freeze_page_vma(avc->vma, page, address);
3148 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3149 address, address + HPAGE_PMD_SIZE);
3153 static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page,
3154 unsigned long address)
3159 swp_entry_t swp_entry;
3160 unsigned long haddr = address & HPAGE_PMD_MASK;
3161 int i, nr = HPAGE_PMD_NR;
3163 /* Skip pages which doesn't belong to the VMA */
3164 if (address < vma->vm_start) {
3165 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3168 address = vma->vm_start;
3171 pmd = mm_find_pmd(vma->vm_mm, address);
3175 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3176 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) {
3178 * We've just crossed page table boundary: need to map next one.
3179 * It can happen if THP was mremaped to non-PMD aligned address.
3181 if (unlikely(address == haddr + HPAGE_PMD_SIZE)) {
3182 pte_unmap_unlock(pte - 1, ptl);
3183 pmd = mm_find_pmd(vma->vm_mm, address);
3186 pte = pte_offset_map_lock(vma->vm_mm, pmd,
3190 if (!is_swap_pte(*pte))
3193 swp_entry = pte_to_swp_entry(*pte);
3194 if (!is_migration_entry(swp_entry))
3196 if (migration_entry_to_page(swp_entry) != page)
3200 page_add_anon_rmap(page, vma, address, false);
3202 entry = pte_mkold(mk_pte(page, vma->vm_page_prot));
3203 if (PageDirty(page))
3204 entry = pte_mkdirty(entry);
3205 if (is_write_migration_entry(swp_entry))
3206 entry = maybe_mkwrite(entry, vma);
3208 flush_dcache_page(page);
3209 set_pte_at(vma->vm_mm, address, pte, entry);
3211 /* No need to invalidate - it was non-present before */
3212 update_mmu_cache(vma, address, pte);
3214 pte_unmap_unlock(pte - 1, ptl);
3217 static void unfreeze_page(struct anon_vma *anon_vma, struct page *page)
3219 struct anon_vma_chain *avc;
3220 pgoff_t pgoff = page_to_pgoff(page);
3222 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
3223 pgoff, pgoff + HPAGE_PMD_NR - 1) {
3224 unsigned long address = __vma_address(page, avc->vma);
3226 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3227 address, address + HPAGE_PMD_SIZE);
3228 unfreeze_page_vma(avc->vma, page, address);
3229 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3230 address, address + HPAGE_PMD_SIZE);
3234 static int __split_huge_page_tail(struct page *head, int tail,
3235 struct lruvec *lruvec, struct list_head *list)
3238 struct page *page_tail = head + tail;
3240 mapcount = atomic_read(&page_tail->_mapcount) + 1;
3241 VM_BUG_ON_PAGE(atomic_read(&page_tail->_count) != 0, page_tail);
3244 * tail_page->_count is zero and not changing from under us. But
3245 * get_page_unless_zero() may be running from under us on the
3246 * tail_page. If we used atomic_set() below instead of atomic_add(), we
3247 * would then run atomic_set() concurrently with
3248 * get_page_unless_zero(), and atomic_set() is implemented in C not
3249 * using locked ops. spin_unlock on x86 sometime uses locked ops
3250 * because of PPro errata 66, 92, so unless somebody can guarantee
3251 * atomic_set() here would be safe on all archs (and not only on x86),
3252 * it's safer to use atomic_add().
3254 atomic_add(mapcount + 1, &page_tail->_count);
3257 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3258 page_tail->flags |= (head->flags &
3259 ((1L << PG_referenced) |
3260 (1L << PG_swapbacked) |
3261 (1L << PG_mlocked) |
3262 (1L << PG_uptodate) |
3265 (1L << PG_unevictable) |
3269 * After clearing PageTail the gup refcount can be released.
3270 * Page flags also must be visible before we make the page non-compound.
3274 clear_compound_head(page_tail);
3276 if (page_is_young(head))
3277 set_page_young(page_tail);
3278 if (page_is_idle(head))
3279 set_page_idle(page_tail);
3281 /* ->mapping in first tail page is compound_mapcount */
3282 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3284 page_tail->mapping = head->mapping;
3286 page_tail->index = head->index + tail;
3287 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3288 lru_add_page_tail(head, page_tail, lruvec, list);
3293 static void __split_huge_page(struct page *page, struct list_head *list)
3295 struct page *head = compound_head(page);
3296 struct zone *zone = page_zone(head);
3297 struct lruvec *lruvec;
3298 int i, tail_mapcount;
3300 /* prevent PageLRU to go away from under us, and freeze lru stats */
3301 spin_lock_irq(&zone->lru_lock);
3302 lruvec = mem_cgroup_page_lruvec(head, zone);
3304 /* complete memcg works before add pages to LRU */
3305 mem_cgroup_split_huge_fixup(head);
3308 for (i = HPAGE_PMD_NR - 1; i >= 1; i--)
3309 tail_mapcount += __split_huge_page_tail(head, i, lruvec, list);
3310 atomic_sub(tail_mapcount, &head->_count);
3312 ClearPageCompound(head);
3313 spin_unlock_irq(&zone->lru_lock);
3315 unfreeze_page(page_anon_vma(head), head);
3317 for (i = 0; i < HPAGE_PMD_NR; i++) {
3318 struct page *subpage = head + i;
3319 if (subpage == page)
3321 unlock_page(subpage);
3324 * Subpages may be freed if there wasn't any mapping
3325 * like if add_to_swap() is running on a lru page that
3326 * had its mapping zapped. And freeing these pages
3327 * requires taking the lru_lock so we do the put_page
3328 * of the tail pages after the split is complete.
3334 int total_mapcount(struct page *page)
3338 VM_BUG_ON_PAGE(PageTail(page), page);
3340 if (likely(!PageCompound(page)))
3341 return atomic_read(&page->_mapcount) + 1;
3343 ret = compound_mapcount(page);
3346 for (i = 0; i < HPAGE_PMD_NR; i++)
3347 ret += atomic_read(&page[i]._mapcount) + 1;
3348 if (PageDoubleMap(page))
3349 ret -= HPAGE_PMD_NR;
3354 * This function splits huge page into normal pages. @page can point to any
3355 * subpage of huge page to split. Split doesn't change the position of @page.
3357 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3358 * The huge page must be locked.
3360 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3362 * Both head page and tail pages will inherit mapping, flags, and so on from
3365 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3366 * they are not mapped.
3368 * Returns 0 if the hugepage is split successfully.
3369 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3372 int split_huge_page_to_list(struct page *page, struct list_head *list)
3374 struct page *head = compound_head(page);
3375 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
3376 struct anon_vma *anon_vma;
3377 int count, mapcount, ret;
3379 unsigned long flags;
3381 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3382 VM_BUG_ON_PAGE(!PageAnon(page), page);
3383 VM_BUG_ON_PAGE(!PageLocked(page), page);
3384 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3385 VM_BUG_ON_PAGE(!PageCompound(page), page);
3388 * The caller does not necessarily hold an mmap_sem that would prevent
3389 * the anon_vma disappearing so we first we take a reference to it
3390 * and then lock the anon_vma for write. This is similar to
3391 * page_lock_anon_vma_read except the write lock is taken to serialise
3392 * against parallel split or collapse operations.
3394 anon_vma = page_get_anon_vma(head);
3399 anon_vma_lock_write(anon_vma);
3402 * Racy check if we can split the page, before freeze_page() will
3405 if (total_mapcount(head) != page_count(head) - 1) {
3410 mlocked = PageMlocked(page);
3411 freeze_page(anon_vma, head);
3412 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3414 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3418 /* Prevent deferred_split_scan() touching ->_count */
3419 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3420 count = page_count(head);
3421 mapcount = total_mapcount(head);
3422 if (!mapcount && count == 1) {
3423 if (!list_empty(page_deferred_list(head))) {
3424 pgdata->split_queue_len--;
3425 list_del(page_deferred_list(head));
3427 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3428 __split_huge_page(page, list);
3430 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
3431 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3432 pr_alert("total_mapcount: %u, page_count(): %u\n",
3435 dump_page(head, NULL);
3436 dump_page(page, "total_mapcount(head) > 0");
3439 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3440 unfreeze_page(anon_vma, head);
3445 anon_vma_unlock_write(anon_vma);
3446 put_anon_vma(anon_vma);
3448 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3452 void free_transhuge_page(struct page *page)
3454 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3455 unsigned long flags;
3457 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3458 if (!list_empty(page_deferred_list(page))) {
3459 pgdata->split_queue_len--;
3460 list_del(page_deferred_list(page));
3462 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3463 free_compound_page(page);
3466 void deferred_split_huge_page(struct page *page)
3468 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3469 unsigned long flags;
3471 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3473 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3474 if (list_empty(page_deferred_list(page))) {
3475 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
3476 pgdata->split_queue_len++;
3478 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3481 static unsigned long deferred_split_count(struct shrinker *shrink,
3482 struct shrink_control *sc)
3484 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3485 return ACCESS_ONCE(pgdata->split_queue_len);
3488 static unsigned long deferred_split_scan(struct shrinker *shrink,
3489 struct shrink_control *sc)
3491 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3492 unsigned long flags;
3493 LIST_HEAD(list), *pos, *next;
3497 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3498 /* Take pin on all head pages to avoid freeing them under us */
3499 list_for_each_safe(pos, next, &pgdata->split_queue) {
3500 page = list_entry((void *)pos, struct page, mapping);
3501 page = compound_head(page);
3502 if (get_page_unless_zero(page)) {
3503 list_move(page_deferred_list(page), &list);
3505 /* We lost race with put_compound_page() */
3506 list_del_init(page_deferred_list(page));
3507 pgdata->split_queue_len--;
3509 if (!--sc->nr_to_scan)
3512 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3514 list_for_each_safe(pos, next, &list) {
3515 page = list_entry((void *)pos, struct page, mapping);
3517 /* split_huge_page() removes page from list on success */
3518 if (!split_huge_page(page))
3524 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3525 list_splice_tail(&list, &pgdata->split_queue);
3526 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3529 * Stop shrinker if we didn't split any page, but the queue is empty.
3530 * This can happen if pages were freed under us.
3532 if (!split && list_empty(&pgdata->split_queue))
3537 static struct shrinker deferred_split_shrinker = {
3538 .count_objects = deferred_split_count,
3539 .scan_objects = deferred_split_scan,
3540 .seeks = DEFAULT_SEEKS,
3541 .flags = SHRINKER_NUMA_AWARE,
3544 #ifdef CONFIG_DEBUG_FS
3545 static int split_huge_pages_set(void *data, u64 val)
3549 unsigned long pfn, max_zone_pfn;
3550 unsigned long total = 0, split = 0;
3555 for_each_populated_zone(zone) {
3556 max_zone_pfn = zone_end_pfn(zone);
3557 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3558 if (!pfn_valid(pfn))
3561 page = pfn_to_page(pfn);
3562 if (!get_page_unless_zero(page))
3565 if (zone != page_zone(page))
3568 if (!PageHead(page) || !PageAnon(page) ||
3574 if (!split_huge_page(page))
3582 pr_info("%lu of %lu THP split", split, total);
3586 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3589 static int __init split_huge_pages_debugfs(void)
3593 ret = debugfs_create_file("split_huge_pages", 0644, NULL, NULL,
3594 &split_huge_pages_fops);
3596 pr_warn("Failed to create split_huge_pages in debugfs");
3599 late_initcall(split_huge_pages_debugfs);