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 = HPAGE_PMD_NR*8;
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 = HPAGE_PMD_NR-1;
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 to help transparent hugepage allocations\n",
172 min_free_kbytes, recommended_min);
174 min_free_kbytes = recommended_min;
176 setup_per_zone_wmarks();
179 static int start_stop_khugepaged(void)
182 if (khugepaged_enabled()) {
183 if (!khugepaged_thread)
184 khugepaged_thread = kthread_run(khugepaged, NULL,
186 if (IS_ERR(khugepaged_thread)) {
187 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
188 err = PTR_ERR(khugepaged_thread);
189 khugepaged_thread = NULL;
193 if (!list_empty(&khugepaged_scan.mm_head))
194 wake_up_interruptible(&khugepaged_wait);
196 set_recommended_min_free_kbytes();
197 } else if (khugepaged_thread) {
198 kthread_stop(khugepaged_thread);
199 khugepaged_thread = NULL;
205 static atomic_t huge_zero_refcount;
206 struct page *huge_zero_page __read_mostly;
208 struct page *get_huge_zero_page(void)
210 struct page *zero_page;
212 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
213 return READ_ONCE(huge_zero_page);
215 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
218 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
221 count_vm_event(THP_ZERO_PAGE_ALLOC);
223 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
225 __free_pages(zero_page, compound_order(zero_page));
229 /* We take additional reference here. It will be put back by shrinker */
230 atomic_set(&huge_zero_refcount, 2);
232 return READ_ONCE(huge_zero_page);
235 static void put_huge_zero_page(void)
238 * Counter should never go to zero here. Only shrinker can put
241 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
244 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
245 struct shrink_control *sc)
247 /* we can free zero page only if last reference remains */
248 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
251 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
252 struct shrink_control *sc)
254 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
255 struct page *zero_page = xchg(&huge_zero_page, NULL);
256 BUG_ON(zero_page == NULL);
257 __free_pages(zero_page, compound_order(zero_page));
264 static struct shrinker huge_zero_page_shrinker = {
265 .count_objects = shrink_huge_zero_page_count,
266 .scan_objects = shrink_huge_zero_page_scan,
267 .seeks = DEFAULT_SEEKS,
272 static ssize_t triple_flag_store(struct kobject *kobj,
273 struct kobj_attribute *attr,
274 const char *buf, size_t count,
275 enum transparent_hugepage_flag enabled,
276 enum transparent_hugepage_flag deferred,
277 enum transparent_hugepage_flag req_madv)
279 if (!memcmp("defer", buf,
280 min(sizeof("defer")-1, count))) {
281 if (enabled == deferred)
283 clear_bit(enabled, &transparent_hugepage_flags);
284 clear_bit(req_madv, &transparent_hugepage_flags);
285 set_bit(deferred, &transparent_hugepage_flags);
286 } else if (!memcmp("always", buf,
287 min(sizeof("always")-1, count))) {
288 clear_bit(deferred, &transparent_hugepage_flags);
289 clear_bit(req_madv, &transparent_hugepage_flags);
290 set_bit(enabled, &transparent_hugepage_flags);
291 } else if (!memcmp("madvise", buf,
292 min(sizeof("madvise")-1, count))) {
293 clear_bit(enabled, &transparent_hugepage_flags);
294 clear_bit(deferred, &transparent_hugepage_flags);
295 set_bit(req_madv, &transparent_hugepage_flags);
296 } else if (!memcmp("never", buf,
297 min(sizeof("never")-1, count))) {
298 clear_bit(enabled, &transparent_hugepage_flags);
299 clear_bit(req_madv, &transparent_hugepage_flags);
300 clear_bit(deferred, &transparent_hugepage_flags);
307 static ssize_t enabled_show(struct kobject *kobj,
308 struct kobj_attribute *attr, char *buf)
310 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
311 return sprintf(buf, "[always] madvise never\n");
312 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
313 return sprintf(buf, "always [madvise] never\n");
315 return sprintf(buf, "always madvise [never]\n");
318 static ssize_t enabled_store(struct kobject *kobj,
319 struct kobj_attribute *attr,
320 const char *buf, size_t count)
324 ret = triple_flag_store(kobj, attr, buf, count,
325 TRANSPARENT_HUGEPAGE_FLAG,
326 TRANSPARENT_HUGEPAGE_FLAG,
327 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
332 mutex_lock(&khugepaged_mutex);
333 err = start_stop_khugepaged();
334 mutex_unlock(&khugepaged_mutex);
342 static struct kobj_attribute enabled_attr =
343 __ATTR(enabled, 0644, enabled_show, enabled_store);
345 static ssize_t single_flag_show(struct kobject *kobj,
346 struct kobj_attribute *attr, char *buf,
347 enum transparent_hugepage_flag flag)
349 return sprintf(buf, "%d\n",
350 !!test_bit(flag, &transparent_hugepage_flags));
353 static ssize_t single_flag_store(struct kobject *kobj,
354 struct kobj_attribute *attr,
355 const char *buf, size_t count,
356 enum transparent_hugepage_flag flag)
361 ret = kstrtoul(buf, 10, &value);
368 set_bit(flag, &transparent_hugepage_flags);
370 clear_bit(flag, &transparent_hugepage_flags);
376 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
377 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
378 * memory just to allocate one more hugepage.
380 static ssize_t defrag_show(struct kobject *kobj,
381 struct kobj_attribute *attr, char *buf)
383 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
384 return sprintf(buf, "[always] defer madvise never\n");
385 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
386 return sprintf(buf, "always [defer] madvise never\n");
387 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
388 return sprintf(buf, "always defer [madvise] never\n");
390 return sprintf(buf, "always defer madvise [never]\n");
393 static ssize_t defrag_store(struct kobject *kobj,
394 struct kobj_attribute *attr,
395 const char *buf, size_t count)
397 return triple_flag_store(kobj, attr, buf, count,
398 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
399 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
400 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
402 static struct kobj_attribute defrag_attr =
403 __ATTR(defrag, 0644, defrag_show, defrag_store);
405 static ssize_t use_zero_page_show(struct kobject *kobj,
406 struct kobj_attribute *attr, char *buf)
408 return single_flag_show(kobj, attr, buf,
409 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
411 static ssize_t use_zero_page_store(struct kobject *kobj,
412 struct kobj_attribute *attr, const char *buf, size_t count)
414 return single_flag_store(kobj, attr, buf, count,
415 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
417 static struct kobj_attribute use_zero_page_attr =
418 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
419 #ifdef CONFIG_DEBUG_VM
420 static ssize_t debug_cow_show(struct kobject *kobj,
421 struct kobj_attribute *attr, char *buf)
423 return single_flag_show(kobj, attr, buf,
424 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
426 static ssize_t debug_cow_store(struct kobject *kobj,
427 struct kobj_attribute *attr,
428 const char *buf, size_t count)
430 return single_flag_store(kobj, attr, buf, count,
431 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
433 static struct kobj_attribute debug_cow_attr =
434 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
435 #endif /* CONFIG_DEBUG_VM */
437 static struct attribute *hugepage_attr[] = {
440 &use_zero_page_attr.attr,
441 #ifdef CONFIG_DEBUG_VM
442 &debug_cow_attr.attr,
447 static struct attribute_group hugepage_attr_group = {
448 .attrs = hugepage_attr,
451 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
452 struct kobj_attribute *attr,
455 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
458 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
459 struct kobj_attribute *attr,
460 const char *buf, size_t count)
465 err = kstrtoul(buf, 10, &msecs);
466 if (err || msecs > UINT_MAX)
469 khugepaged_scan_sleep_millisecs = msecs;
470 wake_up_interruptible(&khugepaged_wait);
474 static struct kobj_attribute scan_sleep_millisecs_attr =
475 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
476 scan_sleep_millisecs_store);
478 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
479 struct kobj_attribute *attr,
482 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
485 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
486 struct kobj_attribute *attr,
487 const char *buf, size_t count)
492 err = kstrtoul(buf, 10, &msecs);
493 if (err || msecs > UINT_MAX)
496 khugepaged_alloc_sleep_millisecs = msecs;
497 wake_up_interruptible(&khugepaged_wait);
501 static struct kobj_attribute alloc_sleep_millisecs_attr =
502 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
503 alloc_sleep_millisecs_store);
505 static ssize_t pages_to_scan_show(struct kobject *kobj,
506 struct kobj_attribute *attr,
509 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
511 static ssize_t pages_to_scan_store(struct kobject *kobj,
512 struct kobj_attribute *attr,
513 const char *buf, size_t count)
518 err = kstrtoul(buf, 10, &pages);
519 if (err || !pages || pages > UINT_MAX)
522 khugepaged_pages_to_scan = pages;
526 static struct kobj_attribute pages_to_scan_attr =
527 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
528 pages_to_scan_store);
530 static ssize_t pages_collapsed_show(struct kobject *kobj,
531 struct kobj_attribute *attr,
534 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
536 static struct kobj_attribute pages_collapsed_attr =
537 __ATTR_RO(pages_collapsed);
539 static ssize_t full_scans_show(struct kobject *kobj,
540 struct kobj_attribute *attr,
543 return sprintf(buf, "%u\n", khugepaged_full_scans);
545 static struct kobj_attribute full_scans_attr =
546 __ATTR_RO(full_scans);
548 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
549 struct kobj_attribute *attr, char *buf)
551 return single_flag_show(kobj, attr, buf,
552 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
554 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
555 struct kobj_attribute *attr,
556 const char *buf, size_t count)
558 return single_flag_store(kobj, attr, buf, count,
559 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
561 static struct kobj_attribute khugepaged_defrag_attr =
562 __ATTR(defrag, 0644, khugepaged_defrag_show,
563 khugepaged_defrag_store);
566 * max_ptes_none controls if khugepaged should collapse hugepages over
567 * any unmapped ptes in turn potentially increasing the memory
568 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
569 * reduce the available free memory in the system as it
570 * runs. Increasing max_ptes_none will instead potentially reduce the
571 * free memory in the system during the khugepaged scan.
573 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
574 struct kobj_attribute *attr,
577 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
579 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
580 struct kobj_attribute *attr,
581 const char *buf, size_t count)
584 unsigned long max_ptes_none;
586 err = kstrtoul(buf, 10, &max_ptes_none);
587 if (err || max_ptes_none > HPAGE_PMD_NR-1)
590 khugepaged_max_ptes_none = max_ptes_none;
594 static struct kobj_attribute khugepaged_max_ptes_none_attr =
595 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
596 khugepaged_max_ptes_none_store);
598 static struct attribute *khugepaged_attr[] = {
599 &khugepaged_defrag_attr.attr,
600 &khugepaged_max_ptes_none_attr.attr,
601 &pages_to_scan_attr.attr,
602 &pages_collapsed_attr.attr,
603 &full_scans_attr.attr,
604 &scan_sleep_millisecs_attr.attr,
605 &alloc_sleep_millisecs_attr.attr,
609 static struct attribute_group khugepaged_attr_group = {
610 .attrs = khugepaged_attr,
611 .name = "khugepaged",
614 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
618 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
619 if (unlikely(!*hugepage_kobj)) {
620 pr_err("failed to create transparent hugepage kobject\n");
624 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
626 pr_err("failed to register transparent hugepage group\n");
630 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
632 pr_err("failed to register transparent hugepage group\n");
633 goto remove_hp_group;
639 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
641 kobject_put(*hugepage_kobj);
645 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
647 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
648 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
649 kobject_put(hugepage_kobj);
652 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
657 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
660 #endif /* CONFIG_SYSFS */
662 static int __init hugepage_init(void)
665 struct kobject *hugepage_kobj;
667 if (!has_transparent_hugepage()) {
668 transparent_hugepage_flags = 0;
672 err = hugepage_init_sysfs(&hugepage_kobj);
676 err = khugepaged_slab_init();
680 err = register_shrinker(&huge_zero_page_shrinker);
682 goto err_hzp_shrinker;
683 err = register_shrinker(&deferred_split_shrinker);
685 goto err_split_shrinker;
688 * By default disable transparent hugepages on smaller systems,
689 * where the extra memory used could hurt more than TLB overhead
690 * is likely to save. The admin can still enable it through /sys.
692 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
693 transparent_hugepage_flags = 0;
697 err = start_stop_khugepaged();
703 unregister_shrinker(&deferred_split_shrinker);
705 unregister_shrinker(&huge_zero_page_shrinker);
707 khugepaged_slab_exit();
709 hugepage_exit_sysfs(hugepage_kobj);
713 subsys_initcall(hugepage_init);
715 static int __init setup_transparent_hugepage(char *str)
720 if (!strcmp(str, "always")) {
721 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
722 &transparent_hugepage_flags);
723 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
724 &transparent_hugepage_flags);
726 } else if (!strcmp(str, "madvise")) {
727 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
728 &transparent_hugepage_flags);
729 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
730 &transparent_hugepage_flags);
732 } else if (!strcmp(str, "never")) {
733 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
734 &transparent_hugepage_flags);
735 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
736 &transparent_hugepage_flags);
741 pr_warn("transparent_hugepage= cannot parse, ignored\n");
744 __setup("transparent_hugepage=", setup_transparent_hugepage);
746 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
748 if (likely(vma->vm_flags & VM_WRITE))
749 pmd = pmd_mkwrite(pmd);
753 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
756 entry = mk_pmd(page, prot);
757 entry = pmd_mkhuge(entry);
761 static inline struct list_head *page_deferred_list(struct page *page)
764 * ->lru in the tail pages is occupied by compound_head.
765 * Let's use ->mapping + ->index in the second tail page as list_head.
767 return (struct list_head *)&page[2].mapping;
770 void prep_transhuge_page(struct page *page)
773 * we use page->mapping and page->indexlru in second tail page
774 * as list_head: assuming THP order >= 2
776 BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
778 INIT_LIST_HEAD(page_deferred_list(page));
779 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
782 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
783 struct vm_area_struct *vma,
784 unsigned long address, pmd_t *pmd,
785 struct page *page, gfp_t gfp,
788 struct mem_cgroup *memcg;
791 unsigned long haddr = address & HPAGE_PMD_MASK;
793 VM_BUG_ON_PAGE(!PageCompound(page), page);
795 if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) {
797 count_vm_event(THP_FAULT_FALLBACK);
798 return VM_FAULT_FALLBACK;
801 pgtable = pte_alloc_one(mm, haddr);
802 if (unlikely(!pgtable)) {
803 mem_cgroup_cancel_charge(page, memcg, true);
808 clear_huge_page(page, haddr, HPAGE_PMD_NR);
810 * The memory barrier inside __SetPageUptodate makes sure that
811 * clear_huge_page writes become visible before the set_pmd_at()
814 __SetPageUptodate(page);
816 ptl = pmd_lock(mm, pmd);
817 if (unlikely(!pmd_none(*pmd))) {
819 mem_cgroup_cancel_charge(page, memcg, true);
821 pte_free(mm, pgtable);
825 /* Deliver the page fault to userland */
826 if (userfaultfd_missing(vma)) {
830 mem_cgroup_cancel_charge(page, memcg, true);
832 pte_free(mm, pgtable);
833 ret = handle_userfault(vma, address, flags,
835 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
839 entry = mk_huge_pmd(page, vma->vm_page_prot);
840 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
841 page_add_new_anon_rmap(page, vma, haddr, true);
842 mem_cgroup_commit_charge(page, memcg, false, true);
843 lru_cache_add_active_or_unevictable(page, vma);
844 pgtable_trans_huge_deposit(mm, pmd, pgtable);
845 set_pmd_at(mm, haddr, pmd, entry);
846 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
847 atomic_long_inc(&mm->nr_ptes);
849 count_vm_event(THP_FAULT_ALLOC);
856 * If THP is set to always then directly reclaim/compact as necessary
857 * If set to defer then do no reclaim and defer to khugepaged
858 * If set to madvise and the VMA is flagged then directly reclaim/compact
860 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
862 gfp_t reclaim_flags = 0;
864 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags) &&
865 (vma->vm_flags & VM_HUGEPAGE))
866 reclaim_flags = __GFP_DIRECT_RECLAIM;
867 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
868 reclaim_flags = __GFP_KSWAPD_RECLAIM;
869 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
870 reclaim_flags = __GFP_DIRECT_RECLAIM;
872 return GFP_TRANSHUGE | reclaim_flags;
875 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
876 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
878 return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0);
881 /* Caller must hold page table lock. */
882 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
883 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
884 struct page *zero_page)
889 entry = mk_pmd(zero_page, vma->vm_page_prot);
890 entry = pmd_mkhuge(entry);
892 pgtable_trans_huge_deposit(mm, pmd, pgtable);
893 set_pmd_at(mm, haddr, pmd, entry);
894 atomic_long_inc(&mm->nr_ptes);
898 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
899 unsigned long address, pmd_t *pmd,
904 unsigned long haddr = address & HPAGE_PMD_MASK;
906 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
907 return VM_FAULT_FALLBACK;
908 if (unlikely(anon_vma_prepare(vma)))
910 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
912 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
913 transparent_hugepage_use_zero_page()) {
916 struct page *zero_page;
919 pgtable = pte_alloc_one(mm, haddr);
920 if (unlikely(!pgtable))
922 zero_page = get_huge_zero_page();
923 if (unlikely(!zero_page)) {
924 pte_free(mm, pgtable);
925 count_vm_event(THP_FAULT_FALLBACK);
926 return VM_FAULT_FALLBACK;
928 ptl = pmd_lock(mm, pmd);
931 if (pmd_none(*pmd)) {
932 if (userfaultfd_missing(vma)) {
934 ret = handle_userfault(vma, address, flags,
936 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
938 set_huge_zero_page(pgtable, mm, vma,
947 pte_free(mm, pgtable);
948 put_huge_zero_page();
952 gfp = alloc_hugepage_direct_gfpmask(vma);
953 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
954 if (unlikely(!page)) {
955 count_vm_event(THP_FAULT_FALLBACK);
956 return VM_FAULT_FALLBACK;
958 prep_transhuge_page(page);
959 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
963 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
964 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
966 struct mm_struct *mm = vma->vm_mm;
970 ptl = pmd_lock(mm, pmd);
971 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
972 if (pfn_t_devmap(pfn))
973 entry = pmd_mkdevmap(entry);
975 entry = pmd_mkyoung(pmd_mkdirty(entry));
976 entry = maybe_pmd_mkwrite(entry, vma);
978 set_pmd_at(mm, addr, pmd, entry);
979 update_mmu_cache_pmd(vma, addr, pmd);
983 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
984 pmd_t *pmd, pfn_t pfn, bool write)
986 pgprot_t pgprot = vma->vm_page_prot;
988 * If we had pmd_special, we could avoid all these restrictions,
989 * but we need to be consistent with PTEs and architectures that
990 * can't support a 'special' bit.
992 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
993 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
994 (VM_PFNMAP|VM_MIXEDMAP));
995 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
996 BUG_ON(!pfn_t_devmap(pfn));
998 if (addr < vma->vm_start || addr >= vma->vm_end)
999 return VM_FAULT_SIGBUS;
1000 if (track_pfn_insert(vma, &pgprot, pfn))
1001 return VM_FAULT_SIGBUS;
1002 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
1003 return VM_FAULT_NOPAGE;
1006 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1012 * We should set the dirty bit only for FOLL_WRITE but for now
1013 * the dirty bit in the pmd is meaningless. And if the dirty
1014 * bit will become meaningful and we'll only set it with
1015 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
1016 * set the young bit, instead of the current set_pmd_at.
1018 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1019 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1021 update_mmu_cache_pmd(vma, addr, pmd);
1024 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1025 pmd_t *pmd, int flags)
1027 unsigned long pfn = pmd_pfn(*pmd);
1028 struct mm_struct *mm = vma->vm_mm;
1029 struct dev_pagemap *pgmap;
1032 assert_spin_locked(pmd_lockptr(mm, pmd));
1034 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1037 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1042 if (flags & FOLL_TOUCH)
1043 touch_pmd(vma, addr, pmd);
1046 * device mapped pages can only be returned if the
1047 * caller will manage the page reference count.
1049 if (!(flags & FOLL_GET))
1050 return ERR_PTR(-EEXIST);
1052 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1053 pgmap = get_dev_pagemap(pfn, NULL);
1055 return ERR_PTR(-EFAULT);
1056 page = pfn_to_page(pfn);
1058 put_dev_pagemap(pgmap);
1063 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1064 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1065 struct vm_area_struct *vma)
1067 spinlock_t *dst_ptl, *src_ptl;
1068 struct page *src_page;
1070 pgtable_t pgtable = NULL;
1073 if (!vma_is_dax(vma)) {
1075 pgtable = pte_alloc_one(dst_mm, addr);
1076 if (unlikely(!pgtable))
1080 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1081 src_ptl = pmd_lockptr(src_mm, src_pmd);
1082 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1086 if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
1087 pte_free(dst_mm, pgtable);
1091 * When page table lock is held, the huge zero pmd should not be
1092 * under splitting since we don't split the page itself, only pmd to
1095 if (is_huge_zero_pmd(pmd)) {
1096 struct page *zero_page;
1098 * get_huge_zero_page() will never allocate a new page here,
1099 * since we already have a zero page to copy. It just takes a
1102 zero_page = get_huge_zero_page();
1103 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1109 if (!vma_is_dax(vma)) {
1110 /* thp accounting separate from pmd_devmap accounting */
1111 src_page = pmd_page(pmd);
1112 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1114 page_dup_rmap(src_page, true);
1115 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1116 atomic_long_inc(&dst_mm->nr_ptes);
1117 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1120 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1121 pmd = pmd_mkold(pmd_wrprotect(pmd));
1122 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1126 spin_unlock(src_ptl);
1127 spin_unlock(dst_ptl);
1132 void huge_pmd_set_accessed(struct mm_struct *mm,
1133 struct vm_area_struct *vma,
1134 unsigned long address,
1135 pmd_t *pmd, pmd_t orig_pmd,
1140 unsigned long haddr;
1142 ptl = pmd_lock(mm, pmd);
1143 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1146 entry = pmd_mkyoung(orig_pmd);
1147 haddr = address & HPAGE_PMD_MASK;
1148 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1149 update_mmu_cache_pmd(vma, address, pmd);
1155 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1156 struct vm_area_struct *vma,
1157 unsigned long address,
1158 pmd_t *pmd, pmd_t orig_pmd,
1160 unsigned long haddr)
1162 struct mem_cgroup *memcg;
1167 struct page **pages;
1168 unsigned long mmun_start; /* For mmu_notifiers */
1169 unsigned long mmun_end; /* For mmu_notifiers */
1171 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1173 if (unlikely(!pages)) {
1174 ret |= VM_FAULT_OOM;
1178 for (i = 0; i < HPAGE_PMD_NR; i++) {
1179 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1181 vma, address, page_to_nid(page));
1182 if (unlikely(!pages[i] ||
1183 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1188 memcg = (void *)page_private(pages[i]);
1189 set_page_private(pages[i], 0);
1190 mem_cgroup_cancel_charge(pages[i], memcg,
1195 ret |= VM_FAULT_OOM;
1198 set_page_private(pages[i], (unsigned long)memcg);
1201 for (i = 0; i < HPAGE_PMD_NR; i++) {
1202 copy_user_highpage(pages[i], page + i,
1203 haddr + PAGE_SIZE * i, vma);
1204 __SetPageUptodate(pages[i]);
1209 mmun_end = haddr + HPAGE_PMD_SIZE;
1210 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1212 ptl = pmd_lock(mm, pmd);
1213 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1214 goto out_free_pages;
1215 VM_BUG_ON_PAGE(!PageHead(page), page);
1217 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1218 /* leave pmd empty until pte is filled */
1220 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1221 pmd_populate(mm, &_pmd, pgtable);
1223 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1225 entry = mk_pte(pages[i], vma->vm_page_prot);
1226 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1227 memcg = (void *)page_private(pages[i]);
1228 set_page_private(pages[i], 0);
1229 page_add_new_anon_rmap(pages[i], vma, haddr, false);
1230 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1231 lru_cache_add_active_or_unevictable(pages[i], vma);
1232 pte = pte_offset_map(&_pmd, haddr);
1233 VM_BUG_ON(!pte_none(*pte));
1234 set_pte_at(mm, haddr, pte, entry);
1239 smp_wmb(); /* make pte visible before pmd */
1240 pmd_populate(mm, pmd, pgtable);
1241 page_remove_rmap(page, true);
1244 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1246 ret |= VM_FAULT_WRITE;
1254 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1255 for (i = 0; i < HPAGE_PMD_NR; i++) {
1256 memcg = (void *)page_private(pages[i]);
1257 set_page_private(pages[i], 0);
1258 mem_cgroup_cancel_charge(pages[i], memcg, false);
1265 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1266 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1270 struct page *page = NULL, *new_page;
1271 struct mem_cgroup *memcg;
1272 unsigned long haddr;
1273 unsigned long mmun_start; /* For mmu_notifiers */
1274 unsigned long mmun_end; /* For mmu_notifiers */
1275 gfp_t huge_gfp; /* for allocation and charge */
1277 ptl = pmd_lockptr(mm, pmd);
1278 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1279 haddr = address & HPAGE_PMD_MASK;
1280 if (is_huge_zero_pmd(orig_pmd))
1283 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1286 page = pmd_page(orig_pmd);
1287 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1289 * We can only reuse the page if nobody else maps the huge page or it's
1290 * part. We can do it by checking page_mapcount() on each sub-page, but
1292 * The cheaper way is to check page_count() to be equal 1: every
1293 * mapcount takes page reference reference, so this way we can
1294 * guarantee, that the PMD is the only mapping.
1295 * This can give false negative if somebody pinned the page, but that's
1298 if (page_mapcount(page) == 1 && page_count(page) == 1) {
1300 entry = pmd_mkyoung(orig_pmd);
1301 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1302 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1303 update_mmu_cache_pmd(vma, address, pmd);
1304 ret |= VM_FAULT_WRITE;
1310 if (transparent_hugepage_enabled(vma) &&
1311 !transparent_hugepage_debug_cow()) {
1312 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1313 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1317 if (likely(new_page)) {
1318 prep_transhuge_page(new_page);
1321 split_huge_pmd(vma, pmd, address);
1322 ret |= VM_FAULT_FALLBACK;
1324 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1325 pmd, orig_pmd, page, haddr);
1326 if (ret & VM_FAULT_OOM) {
1327 split_huge_pmd(vma, pmd, address);
1328 ret |= VM_FAULT_FALLBACK;
1332 count_vm_event(THP_FAULT_FALLBACK);
1336 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg,
1340 split_huge_pmd(vma, pmd, address);
1343 split_huge_pmd(vma, pmd, address);
1344 ret |= VM_FAULT_FALLBACK;
1345 count_vm_event(THP_FAULT_FALLBACK);
1349 count_vm_event(THP_FAULT_ALLOC);
1352 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1354 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1355 __SetPageUptodate(new_page);
1358 mmun_end = haddr + HPAGE_PMD_SIZE;
1359 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1364 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1366 mem_cgroup_cancel_charge(new_page, memcg, true);
1371 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1372 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1373 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1374 page_add_new_anon_rmap(new_page, vma, haddr, true);
1375 mem_cgroup_commit_charge(new_page, memcg, false, true);
1376 lru_cache_add_active_or_unevictable(new_page, vma);
1377 set_pmd_at(mm, haddr, pmd, entry);
1378 update_mmu_cache_pmd(vma, address, pmd);
1380 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1381 put_huge_zero_page();
1383 VM_BUG_ON_PAGE(!PageHead(page), page);
1384 page_remove_rmap(page, true);
1387 ret |= VM_FAULT_WRITE;
1391 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1399 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1404 struct mm_struct *mm = vma->vm_mm;
1405 struct page *page = NULL;
1407 assert_spin_locked(pmd_lockptr(mm, pmd));
1409 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1412 /* Avoid dumping huge zero page */
1413 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1414 return ERR_PTR(-EFAULT);
1416 /* Full NUMA hinting faults to serialise migration in fault paths */
1417 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1420 page = pmd_page(*pmd);
1421 VM_BUG_ON_PAGE(!PageHead(page), page);
1422 if (flags & FOLL_TOUCH)
1423 touch_pmd(vma, addr, pmd);
1424 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1426 * We don't mlock() pte-mapped THPs. This way we can avoid
1427 * leaking mlocked pages into non-VM_LOCKED VMAs.
1429 * In most cases the pmd is the only mapping of the page as we
1430 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1431 * writable private mappings in populate_vma_page_range().
1433 * The only scenario when we have the page shared here is if we
1434 * mlocking read-only mapping shared over fork(). We skip
1435 * mlocking such pages.
1437 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) &&
1438 page->mapping && trylock_page(page)) {
1441 mlock_vma_page(page);
1445 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1446 VM_BUG_ON_PAGE(!PageCompound(page), page);
1447 if (flags & FOLL_GET)
1454 /* NUMA hinting page fault entry point for trans huge pmds */
1455 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1456 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1459 struct anon_vma *anon_vma = NULL;
1461 unsigned long haddr = addr & HPAGE_PMD_MASK;
1462 int page_nid = -1, this_nid = numa_node_id();
1463 int target_nid, last_cpupid = -1;
1465 bool migrated = false;
1469 /* A PROT_NONE fault should not end up here */
1470 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1472 ptl = pmd_lock(mm, pmdp);
1473 if (unlikely(!pmd_same(pmd, *pmdp)))
1477 * If there are potential migrations, wait for completion and retry
1478 * without disrupting NUMA hinting information. Do not relock and
1479 * check_same as the page may no longer be mapped.
1481 if (unlikely(pmd_trans_migrating(*pmdp))) {
1482 page = pmd_page(*pmdp);
1484 wait_on_page_locked(page);
1488 page = pmd_page(pmd);
1489 BUG_ON(is_huge_zero_page(page));
1490 page_nid = page_to_nid(page);
1491 last_cpupid = page_cpupid_last(page);
1492 count_vm_numa_event(NUMA_HINT_FAULTS);
1493 if (page_nid == this_nid) {
1494 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1495 flags |= TNF_FAULT_LOCAL;
1498 /* See similar comment in do_numa_page for explanation */
1499 if (!(vma->vm_flags & VM_WRITE))
1500 flags |= TNF_NO_GROUP;
1503 * Acquire the page lock to serialise THP migrations but avoid dropping
1504 * page_table_lock if at all possible
1506 page_locked = trylock_page(page);
1507 target_nid = mpol_misplaced(page, vma, haddr);
1508 if (target_nid == -1) {
1509 /* If the page was locked, there are no parallel migrations */
1514 /* Migration could have started since the pmd_trans_migrating check */
1517 wait_on_page_locked(page);
1523 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1524 * to serialises splits
1528 anon_vma = page_lock_anon_vma_read(page);
1530 /* Confirm the PMD did not change while page_table_lock was released */
1532 if (unlikely(!pmd_same(pmd, *pmdp))) {
1539 /* Bail if we fail to protect against THP splits for any reason */
1540 if (unlikely(!anon_vma)) {
1547 * Migrate the THP to the requested node, returns with page unlocked
1548 * and access rights restored.
1551 migrated = migrate_misplaced_transhuge_page(mm, vma,
1552 pmdp, pmd, addr, page, target_nid);
1554 flags |= TNF_MIGRATED;
1555 page_nid = target_nid;
1557 flags |= TNF_MIGRATE_FAIL;
1561 BUG_ON(!PageLocked(page));
1562 was_writable = pmd_write(pmd);
1563 pmd = pmd_modify(pmd, vma->vm_page_prot);
1564 pmd = pmd_mkyoung(pmd);
1566 pmd = pmd_mkwrite(pmd);
1567 set_pmd_at(mm, haddr, pmdp, pmd);
1568 update_mmu_cache_pmd(vma, addr, pmdp);
1575 page_unlock_anon_vma_read(anon_vma);
1578 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1583 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1584 pmd_t *pmd, unsigned long addr, unsigned long next)
1590 struct mm_struct *mm = tlb->mm;
1593 ptl = pmd_trans_huge_lock(pmd, vma);
1598 if (is_huge_zero_pmd(orig_pmd)) {
1603 page = pmd_page(orig_pmd);
1605 * If other processes are mapping this page, we couldn't discard
1606 * the page unless they all do MADV_FREE so let's skip the page.
1608 if (page_mapcount(page) != 1)
1611 if (!trylock_page(page))
1615 * If user want to discard part-pages of THP, split it so MADV_FREE
1616 * will deactivate only them.
1618 if (next - addr != HPAGE_PMD_SIZE) {
1621 if (split_huge_page(page)) {
1632 if (PageDirty(page))
1633 ClearPageDirty(page);
1636 if (PageActive(page))
1637 deactivate_page(page);
1639 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1640 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1642 orig_pmd = pmd_mkold(orig_pmd);
1643 orig_pmd = pmd_mkclean(orig_pmd);
1645 set_pmd_at(mm, addr, pmd, orig_pmd);
1646 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1655 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1656 pmd_t *pmd, unsigned long addr)
1661 ptl = __pmd_trans_huge_lock(pmd, vma);
1665 * For architectures like ppc64 we look at deposited pgtable
1666 * when calling pmdp_huge_get_and_clear. So do the
1667 * pgtable_trans_huge_withdraw after finishing pmdp related
1670 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1672 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1673 if (vma_is_dax(vma)) {
1675 if (is_huge_zero_pmd(orig_pmd))
1676 put_huge_zero_page();
1677 } else if (is_huge_zero_pmd(orig_pmd)) {
1678 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1679 atomic_long_dec(&tlb->mm->nr_ptes);
1681 put_huge_zero_page();
1683 struct page *page = pmd_page(orig_pmd);
1684 page_remove_rmap(page, true);
1685 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1686 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1687 VM_BUG_ON_PAGE(!PageHead(page), page);
1688 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1689 atomic_long_dec(&tlb->mm->nr_ptes);
1691 tlb_remove_page(tlb, page);
1696 bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1697 unsigned long old_addr,
1698 unsigned long new_addr, unsigned long old_end,
1699 pmd_t *old_pmd, pmd_t *new_pmd)
1701 spinlock_t *old_ptl, *new_ptl;
1704 struct mm_struct *mm = vma->vm_mm;
1706 if ((old_addr & ~HPAGE_PMD_MASK) ||
1707 (new_addr & ~HPAGE_PMD_MASK) ||
1708 old_end - old_addr < HPAGE_PMD_SIZE ||
1709 (new_vma->vm_flags & VM_NOHUGEPAGE))
1713 * The destination pmd shouldn't be established, free_pgtables()
1714 * should have release it.
1716 if (WARN_ON(!pmd_none(*new_pmd))) {
1717 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1722 * We don't have to worry about the ordering of src and dst
1723 * ptlocks because exclusive mmap_sem prevents deadlock.
1725 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1727 new_ptl = pmd_lockptr(mm, new_pmd);
1728 if (new_ptl != old_ptl)
1729 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1730 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1731 VM_BUG_ON(!pmd_none(*new_pmd));
1733 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1734 vma_is_anonymous(vma)) {
1736 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1737 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1739 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1740 if (new_ptl != old_ptl)
1741 spin_unlock(new_ptl);
1742 spin_unlock(old_ptl);
1750 * - 0 if PMD could not be locked
1751 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1752 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1754 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1755 unsigned long addr, pgprot_t newprot, int prot_numa)
1757 struct mm_struct *mm = vma->vm_mm;
1761 ptl = __pmd_trans_huge_lock(pmd, vma);
1764 bool preserve_write = prot_numa && pmd_write(*pmd);
1768 * Avoid trapping faults against the zero page. The read-only
1769 * data is likely to be read-cached on the local CPU and
1770 * local/remote hits to the zero page are not interesting.
1772 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1777 if (!prot_numa || !pmd_protnone(*pmd)) {
1778 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1779 entry = pmd_modify(entry, newprot);
1781 entry = pmd_mkwrite(entry);
1783 set_pmd_at(mm, addr, pmd, entry);
1784 BUG_ON(!preserve_write && pmd_write(entry));
1793 * Returns true if a given pmd maps a thp, false otherwise.
1795 * Note that if it returns true, this routine returns without unlocking page
1796 * table lock. So callers must unlock it.
1798 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1801 ptl = pmd_lock(vma->vm_mm, pmd);
1802 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1808 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1810 int hugepage_madvise(struct vm_area_struct *vma,
1811 unsigned long *vm_flags, int advice)
1817 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1818 * can't handle this properly after s390_enable_sie, so we simply
1819 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1821 if (mm_has_pgste(vma->vm_mm))
1825 * Be somewhat over-protective like KSM for now!
1827 if (*vm_flags & VM_NO_THP)
1829 *vm_flags &= ~VM_NOHUGEPAGE;
1830 *vm_flags |= VM_HUGEPAGE;
1832 * If the vma become good for khugepaged to scan,
1833 * register it here without waiting a page fault that
1834 * may not happen any time soon.
1836 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1839 case MADV_NOHUGEPAGE:
1841 * Be somewhat over-protective like KSM for now!
1843 if (*vm_flags & VM_NO_THP)
1845 *vm_flags &= ~VM_HUGEPAGE;
1846 *vm_flags |= VM_NOHUGEPAGE;
1848 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1849 * this vma even if we leave the mm registered in khugepaged if
1850 * it got registered before VM_NOHUGEPAGE was set.
1858 static int __init khugepaged_slab_init(void)
1860 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1861 sizeof(struct mm_slot),
1862 __alignof__(struct mm_slot), 0, NULL);
1869 static void __init khugepaged_slab_exit(void)
1871 kmem_cache_destroy(mm_slot_cache);
1874 static inline struct mm_slot *alloc_mm_slot(void)
1876 if (!mm_slot_cache) /* initialization failed */
1878 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1881 static inline void free_mm_slot(struct mm_slot *mm_slot)
1883 kmem_cache_free(mm_slot_cache, mm_slot);
1886 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1888 struct mm_slot *mm_slot;
1890 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1891 if (mm == mm_slot->mm)
1897 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1898 struct mm_slot *mm_slot)
1901 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1904 static inline int khugepaged_test_exit(struct mm_struct *mm)
1906 return atomic_read(&mm->mm_users) == 0;
1909 int __khugepaged_enter(struct mm_struct *mm)
1911 struct mm_slot *mm_slot;
1914 mm_slot = alloc_mm_slot();
1918 /* __khugepaged_exit() must not run from under us */
1919 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1920 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1921 free_mm_slot(mm_slot);
1925 spin_lock(&khugepaged_mm_lock);
1926 insert_to_mm_slots_hash(mm, mm_slot);
1928 * Insert just behind the scanning cursor, to let the area settle
1931 wakeup = list_empty(&khugepaged_scan.mm_head);
1932 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1933 spin_unlock(&khugepaged_mm_lock);
1935 atomic_inc(&mm->mm_count);
1937 wake_up_interruptible(&khugepaged_wait);
1942 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1943 unsigned long vm_flags)
1945 unsigned long hstart, hend;
1948 * Not yet faulted in so we will register later in the
1949 * page fault if needed.
1953 /* khugepaged not yet working on file or special mappings */
1955 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
1956 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1957 hend = vma->vm_end & HPAGE_PMD_MASK;
1959 return khugepaged_enter(vma, vm_flags);
1963 void __khugepaged_exit(struct mm_struct *mm)
1965 struct mm_slot *mm_slot;
1968 spin_lock(&khugepaged_mm_lock);
1969 mm_slot = get_mm_slot(mm);
1970 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1971 hash_del(&mm_slot->hash);
1972 list_del(&mm_slot->mm_node);
1975 spin_unlock(&khugepaged_mm_lock);
1978 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1979 free_mm_slot(mm_slot);
1981 } else if (mm_slot) {
1983 * This is required to serialize against
1984 * khugepaged_test_exit() (which is guaranteed to run
1985 * under mmap sem read mode). Stop here (after we
1986 * return all pagetables will be destroyed) until
1987 * khugepaged has finished working on the pagetables
1988 * under the mmap_sem.
1990 down_write(&mm->mmap_sem);
1991 up_write(&mm->mmap_sem);
1995 static void release_pte_page(struct page *page)
1997 /* 0 stands for page_is_file_cache(page) == false */
1998 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2000 putback_lru_page(page);
2003 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2005 while (--_pte >= pte) {
2006 pte_t pteval = *_pte;
2007 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2008 release_pte_page(pte_page(pteval));
2012 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2013 unsigned long address,
2016 struct page *page = NULL;
2018 int none_or_zero = 0, result = 0;
2019 bool referenced = false, writable = false;
2021 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2022 _pte++, address += PAGE_SIZE) {
2023 pte_t pteval = *_pte;
2024 if (pte_none(pteval) || (pte_present(pteval) &&
2025 is_zero_pfn(pte_pfn(pteval)))) {
2026 if (!userfaultfd_armed(vma) &&
2027 ++none_or_zero <= khugepaged_max_ptes_none) {
2030 result = SCAN_EXCEED_NONE_PTE;
2034 if (!pte_present(pteval)) {
2035 result = SCAN_PTE_NON_PRESENT;
2038 page = vm_normal_page(vma, address, pteval);
2039 if (unlikely(!page)) {
2040 result = SCAN_PAGE_NULL;
2044 VM_BUG_ON_PAGE(PageCompound(page), page);
2045 VM_BUG_ON_PAGE(!PageAnon(page), page);
2046 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2049 * We can do it before isolate_lru_page because the
2050 * page can't be freed from under us. NOTE: PG_lock
2051 * is needed to serialize against split_huge_page
2052 * when invoked from the VM.
2054 if (!trylock_page(page)) {
2055 result = SCAN_PAGE_LOCK;
2060 * cannot use mapcount: can't collapse if there's a gup pin.
2061 * The page must only be referenced by the scanned process
2062 * and page swap cache.
2064 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2066 result = SCAN_PAGE_COUNT;
2069 if (pte_write(pteval)) {
2072 if (PageSwapCache(page) && !reuse_swap_page(page)) {
2074 result = SCAN_SWAP_CACHE_PAGE;
2078 * Page is not in the swap cache. It can be collapsed
2084 * Isolate the page to avoid collapsing an hugepage
2085 * currently in use by the VM.
2087 if (isolate_lru_page(page)) {
2089 result = SCAN_DEL_PAGE_LRU;
2092 /* 0 stands for page_is_file_cache(page) == false */
2093 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2094 VM_BUG_ON_PAGE(!PageLocked(page), page);
2095 VM_BUG_ON_PAGE(PageLRU(page), page);
2097 /* If there is no mapped pte young don't collapse the page */
2098 if (pte_young(pteval) ||
2099 page_is_young(page) || PageReferenced(page) ||
2100 mmu_notifier_test_young(vma->vm_mm, address))
2103 if (likely(writable)) {
2104 if (likely(referenced)) {
2105 result = SCAN_SUCCEED;
2106 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2107 referenced, writable, result);
2111 result = SCAN_PAGE_RO;
2115 release_pte_pages(pte, _pte);
2116 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2117 referenced, writable, result);
2121 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2122 struct vm_area_struct *vma,
2123 unsigned long address,
2127 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2128 pte_t pteval = *_pte;
2129 struct page *src_page;
2131 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2132 clear_user_highpage(page, address);
2133 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2134 if (is_zero_pfn(pte_pfn(pteval))) {
2136 * ptl mostly unnecessary.
2140 * paravirt calls inside pte_clear here are
2143 pte_clear(vma->vm_mm, address, _pte);
2147 src_page = pte_page(pteval);
2148 copy_user_highpage(page, src_page, address, vma);
2149 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2150 release_pte_page(src_page);
2152 * ptl mostly unnecessary, but preempt has to
2153 * be disabled to update the per-cpu stats
2154 * inside page_remove_rmap().
2158 * paravirt calls inside pte_clear here are
2161 pte_clear(vma->vm_mm, address, _pte);
2162 page_remove_rmap(src_page, false);
2164 free_page_and_swap_cache(src_page);
2167 address += PAGE_SIZE;
2172 static void khugepaged_alloc_sleep(void)
2176 add_wait_queue(&khugepaged_wait, &wait);
2177 freezable_schedule_timeout_interruptible(
2178 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2179 remove_wait_queue(&khugepaged_wait, &wait);
2182 static int khugepaged_node_load[MAX_NUMNODES];
2184 static bool khugepaged_scan_abort(int nid)
2189 * If zone_reclaim_mode is disabled, then no extra effort is made to
2190 * allocate memory locally.
2192 if (!zone_reclaim_mode)
2195 /* If there is a count for this node already, it must be acceptable */
2196 if (khugepaged_node_load[nid])
2199 for (i = 0; i < MAX_NUMNODES; i++) {
2200 if (!khugepaged_node_load[i])
2202 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2209 static int khugepaged_find_target_node(void)
2211 static int last_khugepaged_target_node = NUMA_NO_NODE;
2212 int nid, target_node = 0, max_value = 0;
2214 /* find first node with max normal pages hit */
2215 for (nid = 0; nid < MAX_NUMNODES; nid++)
2216 if (khugepaged_node_load[nid] > max_value) {
2217 max_value = khugepaged_node_load[nid];
2221 /* do some balance if several nodes have the same hit record */
2222 if (target_node <= last_khugepaged_target_node)
2223 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2225 if (max_value == khugepaged_node_load[nid]) {
2230 last_khugepaged_target_node = target_node;
2234 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2236 if (IS_ERR(*hpage)) {
2242 khugepaged_alloc_sleep();
2243 } else if (*hpage) {
2251 static struct page *
2252 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2253 unsigned long address, int node)
2255 VM_BUG_ON_PAGE(*hpage, *hpage);
2258 * Before allocating the hugepage, release the mmap_sem read lock.
2259 * The allocation can take potentially a long time if it involves
2260 * sync compaction, and we do not need to hold the mmap_sem during
2261 * that. We will recheck the vma after taking it again in write mode.
2263 up_read(&mm->mmap_sem);
2265 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2266 if (unlikely(!*hpage)) {
2267 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2268 *hpage = ERR_PTR(-ENOMEM);
2272 prep_transhuge_page(*hpage);
2273 count_vm_event(THP_COLLAPSE_ALLOC);
2277 static int khugepaged_find_target_node(void)
2282 static inline struct page *alloc_khugepaged_hugepage(void)
2286 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2289 prep_transhuge_page(page);
2293 static struct page *khugepaged_alloc_hugepage(bool *wait)
2298 hpage = alloc_khugepaged_hugepage();
2300 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2305 khugepaged_alloc_sleep();
2307 count_vm_event(THP_COLLAPSE_ALLOC);
2308 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2313 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2316 *hpage = khugepaged_alloc_hugepage(wait);
2318 if (unlikely(!*hpage))
2324 static struct page *
2325 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2326 unsigned long address, int node)
2328 up_read(&mm->mmap_sem);
2335 static bool hugepage_vma_check(struct vm_area_struct *vma)
2337 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2338 (vma->vm_flags & VM_NOHUGEPAGE))
2340 if (!vma->anon_vma || vma->vm_ops)
2342 if (is_vma_temporary_stack(vma))
2344 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2348 static void collapse_huge_page(struct mm_struct *mm,
2349 unsigned long address,
2350 struct page **hpage,
2351 struct vm_area_struct *vma,
2357 struct page *new_page;
2358 spinlock_t *pmd_ptl, *pte_ptl;
2359 int isolated = 0, result = 0;
2360 unsigned long hstart, hend;
2361 struct mem_cgroup *memcg;
2362 unsigned long mmun_start; /* For mmu_notifiers */
2363 unsigned long mmun_end; /* For mmu_notifiers */
2366 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2368 /* Only allocate from the target node */
2369 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
2371 /* release the mmap_sem read lock. */
2372 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2374 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2378 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2379 result = SCAN_CGROUP_CHARGE_FAIL;
2384 * Prevent all access to pagetables with the exception of
2385 * gup_fast later hanlded by the ptep_clear_flush and the VM
2386 * handled by the anon_vma lock + PG_lock.
2388 down_write(&mm->mmap_sem);
2389 if (unlikely(khugepaged_test_exit(mm))) {
2390 result = SCAN_ANY_PROCESS;
2394 vma = find_vma(mm, address);
2396 result = SCAN_VMA_NULL;
2399 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2400 hend = vma->vm_end & HPAGE_PMD_MASK;
2401 if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
2402 result = SCAN_ADDRESS_RANGE;
2405 if (!hugepage_vma_check(vma)) {
2406 result = SCAN_VMA_CHECK;
2409 pmd = mm_find_pmd(mm, address);
2411 result = SCAN_PMD_NULL;
2415 anon_vma_lock_write(vma->anon_vma);
2417 pte = pte_offset_map(pmd, address);
2418 pte_ptl = pte_lockptr(mm, pmd);
2420 mmun_start = address;
2421 mmun_end = address + HPAGE_PMD_SIZE;
2422 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2423 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2425 * After this gup_fast can't run anymore. This also removes
2426 * any huge TLB entry from the CPU so we won't allow
2427 * huge and small TLB entries for the same virtual address
2428 * to avoid the risk of CPU bugs in that area.
2430 _pmd = pmdp_collapse_flush(vma, address, pmd);
2431 spin_unlock(pmd_ptl);
2432 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2435 isolated = __collapse_huge_page_isolate(vma, address, pte);
2436 spin_unlock(pte_ptl);
2438 if (unlikely(!isolated)) {
2441 BUG_ON(!pmd_none(*pmd));
2443 * We can only use set_pmd_at when establishing
2444 * hugepmds and never for establishing regular pmds that
2445 * points to regular pagetables. Use pmd_populate for that
2447 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2448 spin_unlock(pmd_ptl);
2449 anon_vma_unlock_write(vma->anon_vma);
2455 * All pages are isolated and locked so anon_vma rmap
2456 * can't run anymore.
2458 anon_vma_unlock_write(vma->anon_vma);
2460 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2462 __SetPageUptodate(new_page);
2463 pgtable = pmd_pgtable(_pmd);
2465 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2466 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2469 * spin_lock() below is not the equivalent of smp_wmb(), so
2470 * this is needed to avoid the copy_huge_page writes to become
2471 * visible after the set_pmd_at() write.
2476 BUG_ON(!pmd_none(*pmd));
2477 page_add_new_anon_rmap(new_page, vma, address, true);
2478 mem_cgroup_commit_charge(new_page, memcg, false, true);
2479 lru_cache_add_active_or_unevictable(new_page, vma);
2480 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2481 set_pmd_at(mm, address, pmd, _pmd);
2482 update_mmu_cache_pmd(vma, address, pmd);
2483 spin_unlock(pmd_ptl);
2487 khugepaged_pages_collapsed++;
2488 result = SCAN_SUCCEED;
2490 up_write(&mm->mmap_sem);
2491 trace_mm_collapse_huge_page(mm, isolated, result);
2495 trace_mm_collapse_huge_page(mm, isolated, result);
2498 mem_cgroup_cancel_charge(new_page, memcg, true);
2502 static int khugepaged_scan_pmd(struct mm_struct *mm,
2503 struct vm_area_struct *vma,
2504 unsigned long address,
2505 struct page **hpage)
2509 int ret = 0, none_or_zero = 0, result = 0;
2510 struct page *page = NULL;
2511 unsigned long _address;
2513 int node = NUMA_NO_NODE;
2514 bool writable = false, referenced = false;
2516 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2518 pmd = mm_find_pmd(mm, address);
2520 result = SCAN_PMD_NULL;
2524 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2525 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2526 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2527 _pte++, _address += PAGE_SIZE) {
2528 pte_t pteval = *_pte;
2529 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2530 if (!userfaultfd_armed(vma) &&
2531 ++none_or_zero <= khugepaged_max_ptes_none) {
2534 result = SCAN_EXCEED_NONE_PTE;
2538 if (!pte_present(pteval)) {
2539 result = SCAN_PTE_NON_PRESENT;
2542 if (pte_write(pteval))
2545 page = vm_normal_page(vma, _address, pteval);
2546 if (unlikely(!page)) {
2547 result = SCAN_PAGE_NULL;
2551 /* TODO: teach khugepaged to collapse THP mapped with pte */
2552 if (PageCompound(page)) {
2553 result = SCAN_PAGE_COMPOUND;
2558 * Record which node the original page is from and save this
2559 * information to khugepaged_node_load[].
2560 * Khupaged will allocate hugepage from the node has the max
2563 node = page_to_nid(page);
2564 if (khugepaged_scan_abort(node)) {
2565 result = SCAN_SCAN_ABORT;
2568 khugepaged_node_load[node]++;
2569 if (!PageLRU(page)) {
2570 result = SCAN_SCAN_ABORT;
2573 if (PageLocked(page)) {
2574 result = SCAN_PAGE_LOCK;
2577 if (!PageAnon(page)) {
2578 result = SCAN_PAGE_ANON;
2583 * cannot use mapcount: can't collapse if there's a gup pin.
2584 * The page must only be referenced by the scanned process
2585 * and page swap cache.
2587 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2588 result = SCAN_PAGE_COUNT;
2591 if (pte_young(pteval) ||
2592 page_is_young(page) || PageReferenced(page) ||
2593 mmu_notifier_test_young(vma->vm_mm, address))
2598 result = SCAN_SUCCEED;
2601 result = SCAN_NO_REFERENCED_PAGE;
2604 result = SCAN_PAGE_RO;
2607 pte_unmap_unlock(pte, ptl);
2609 node = khugepaged_find_target_node();
2610 /* collapse_huge_page will return with the mmap_sem released */
2611 collapse_huge_page(mm, address, hpage, vma, node);
2614 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
2615 none_or_zero, result);
2619 static void collect_mm_slot(struct mm_slot *mm_slot)
2621 struct mm_struct *mm = mm_slot->mm;
2623 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2625 if (khugepaged_test_exit(mm)) {
2627 hash_del(&mm_slot->hash);
2628 list_del(&mm_slot->mm_node);
2631 * Not strictly needed because the mm exited already.
2633 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2636 /* khugepaged_mm_lock actually not necessary for the below */
2637 free_mm_slot(mm_slot);
2642 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2643 struct page **hpage)
2644 __releases(&khugepaged_mm_lock)
2645 __acquires(&khugepaged_mm_lock)
2647 struct mm_slot *mm_slot;
2648 struct mm_struct *mm;
2649 struct vm_area_struct *vma;
2653 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2655 if (khugepaged_scan.mm_slot)
2656 mm_slot = khugepaged_scan.mm_slot;
2658 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2659 struct mm_slot, mm_node);
2660 khugepaged_scan.address = 0;
2661 khugepaged_scan.mm_slot = mm_slot;
2663 spin_unlock(&khugepaged_mm_lock);
2666 down_read(&mm->mmap_sem);
2667 if (unlikely(khugepaged_test_exit(mm)))
2670 vma = find_vma(mm, khugepaged_scan.address);
2673 for (; vma; vma = vma->vm_next) {
2674 unsigned long hstart, hend;
2677 if (unlikely(khugepaged_test_exit(mm))) {
2681 if (!hugepage_vma_check(vma)) {
2686 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2687 hend = vma->vm_end & HPAGE_PMD_MASK;
2690 if (khugepaged_scan.address > hend)
2692 if (khugepaged_scan.address < hstart)
2693 khugepaged_scan.address = hstart;
2694 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2696 while (khugepaged_scan.address < hend) {
2699 if (unlikely(khugepaged_test_exit(mm)))
2700 goto breakouterloop;
2702 VM_BUG_ON(khugepaged_scan.address < hstart ||
2703 khugepaged_scan.address + HPAGE_PMD_SIZE >
2705 ret = khugepaged_scan_pmd(mm, vma,
2706 khugepaged_scan.address,
2708 /* move to next address */
2709 khugepaged_scan.address += HPAGE_PMD_SIZE;
2710 progress += HPAGE_PMD_NR;
2712 /* we released mmap_sem so break loop */
2713 goto breakouterloop_mmap_sem;
2714 if (progress >= pages)
2715 goto breakouterloop;
2719 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2720 breakouterloop_mmap_sem:
2722 spin_lock(&khugepaged_mm_lock);
2723 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2725 * Release the current mm_slot if this mm is about to die, or
2726 * if we scanned all vmas of this mm.
2728 if (khugepaged_test_exit(mm) || !vma) {
2730 * Make sure that if mm_users is reaching zero while
2731 * khugepaged runs here, khugepaged_exit will find
2732 * mm_slot not pointing to the exiting mm.
2734 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2735 khugepaged_scan.mm_slot = list_entry(
2736 mm_slot->mm_node.next,
2737 struct mm_slot, mm_node);
2738 khugepaged_scan.address = 0;
2740 khugepaged_scan.mm_slot = NULL;
2741 khugepaged_full_scans++;
2744 collect_mm_slot(mm_slot);
2750 static int khugepaged_has_work(void)
2752 return !list_empty(&khugepaged_scan.mm_head) &&
2753 khugepaged_enabled();
2756 static int khugepaged_wait_event(void)
2758 return !list_empty(&khugepaged_scan.mm_head) ||
2759 kthread_should_stop();
2762 static void khugepaged_do_scan(void)
2764 struct page *hpage = NULL;
2765 unsigned int progress = 0, pass_through_head = 0;
2766 unsigned int pages = khugepaged_pages_to_scan;
2769 barrier(); /* write khugepaged_pages_to_scan to local stack */
2771 while (progress < pages) {
2772 if (!khugepaged_prealloc_page(&hpage, &wait))
2777 if (unlikely(kthread_should_stop() || try_to_freeze()))
2780 spin_lock(&khugepaged_mm_lock);
2781 if (!khugepaged_scan.mm_slot)
2782 pass_through_head++;
2783 if (khugepaged_has_work() &&
2784 pass_through_head < 2)
2785 progress += khugepaged_scan_mm_slot(pages - progress,
2789 spin_unlock(&khugepaged_mm_lock);
2792 if (!IS_ERR_OR_NULL(hpage))
2796 static void khugepaged_wait_work(void)
2798 if (khugepaged_has_work()) {
2799 if (!khugepaged_scan_sleep_millisecs)
2802 wait_event_freezable_timeout(khugepaged_wait,
2803 kthread_should_stop(),
2804 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2808 if (khugepaged_enabled())
2809 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2812 static int khugepaged(void *none)
2814 struct mm_slot *mm_slot;
2817 set_user_nice(current, MAX_NICE);
2819 while (!kthread_should_stop()) {
2820 khugepaged_do_scan();
2821 khugepaged_wait_work();
2824 spin_lock(&khugepaged_mm_lock);
2825 mm_slot = khugepaged_scan.mm_slot;
2826 khugepaged_scan.mm_slot = NULL;
2828 collect_mm_slot(mm_slot);
2829 spin_unlock(&khugepaged_mm_lock);
2833 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2834 unsigned long haddr, pmd_t *pmd)
2836 struct mm_struct *mm = vma->vm_mm;
2841 /* leave pmd empty until pte is filled */
2842 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2844 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2845 pmd_populate(mm, &_pmd, pgtable);
2847 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2849 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2850 entry = pte_mkspecial(entry);
2851 pte = pte_offset_map(&_pmd, haddr);
2852 VM_BUG_ON(!pte_none(*pte));
2853 set_pte_at(mm, haddr, pte, entry);
2856 smp_wmb(); /* make pte visible before pmd */
2857 pmd_populate(mm, pmd, pgtable);
2858 put_huge_zero_page();
2861 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2862 unsigned long haddr, bool freeze)
2864 struct mm_struct *mm = vma->vm_mm;
2868 bool young, write, dirty;
2872 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2873 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2874 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2875 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
2877 count_vm_event(THP_SPLIT_PMD);
2879 if (vma_is_dax(vma)) {
2880 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2881 if (is_huge_zero_pmd(_pmd))
2882 put_huge_zero_page();
2884 } else if (is_huge_zero_pmd(*pmd)) {
2885 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2888 page = pmd_page(*pmd);
2889 VM_BUG_ON_PAGE(!page_count(page), page);
2890 page_ref_add(page, HPAGE_PMD_NR - 1);
2891 write = pmd_write(*pmd);
2892 young = pmd_young(*pmd);
2893 dirty = pmd_dirty(*pmd);
2895 pmdp_huge_split_prepare(vma, haddr, pmd);
2896 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2897 pmd_populate(mm, &_pmd, pgtable);
2899 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2902 * Note that NUMA hinting access restrictions are not
2903 * transferred to avoid any possibility of altering
2904 * permissions across VMAs.
2907 swp_entry_t swp_entry;
2908 swp_entry = make_migration_entry(page + i, write);
2909 entry = swp_entry_to_pte(swp_entry);
2911 entry = mk_pte(page + i, vma->vm_page_prot);
2912 entry = maybe_mkwrite(entry, vma);
2914 entry = pte_wrprotect(entry);
2916 entry = pte_mkold(entry);
2919 SetPageDirty(page + i);
2920 pte = pte_offset_map(&_pmd, addr);
2921 BUG_ON(!pte_none(*pte));
2922 set_pte_at(mm, addr, pte, entry);
2923 atomic_inc(&page[i]._mapcount);
2928 * Set PG_double_map before dropping compound_mapcount to avoid
2929 * false-negative page_mapped().
2931 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2932 for (i = 0; i < HPAGE_PMD_NR; i++)
2933 atomic_inc(&page[i]._mapcount);
2936 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2937 /* Last compound_mapcount is gone. */
2938 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
2939 if (TestClearPageDoubleMap(page)) {
2940 /* No need in mapcount reference anymore */
2941 for (i = 0; i < HPAGE_PMD_NR; i++)
2942 atomic_dec(&page[i]._mapcount);
2946 smp_wmb(); /* make pte visible before pmd */
2948 * Up to this point the pmd is present and huge and userland has the
2949 * whole access to the hugepage during the split (which happens in
2950 * place). If we overwrite the pmd with the not-huge version pointing
2951 * to the pte here (which of course we could if all CPUs were bug
2952 * free), userland could trigger a small page size TLB miss on the
2953 * small sized TLB while the hugepage TLB entry is still established in
2954 * the huge TLB. Some CPU doesn't like that.
2955 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2956 * 383 on page 93. Intel should be safe but is also warns that it's
2957 * only safe if the permission and cache attributes of the two entries
2958 * loaded in the two TLB is identical (which should be the case here).
2959 * But it is generally safer to never allow small and huge TLB entries
2960 * for the same virtual address to be loaded simultaneously. So instead
2961 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2962 * current pmd notpresent (atomically because here the pmd_trans_huge
2963 * and pmd_trans_splitting must remain set at all times on the pmd
2964 * until the split is complete for this pmd), then we flush the SMP TLB
2965 * and finally we write the non-huge version of the pmd entry with
2968 pmdp_invalidate(vma, haddr, pmd);
2969 pmd_populate(mm, pmd, pgtable);
2972 for (i = 0; i < HPAGE_PMD_NR; i++) {
2973 page_remove_rmap(page + i, false);
2979 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2980 unsigned long address)
2983 struct mm_struct *mm = vma->vm_mm;
2984 struct page *page = NULL;
2985 unsigned long haddr = address & HPAGE_PMD_MASK;
2987 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2988 ptl = pmd_lock(mm, pmd);
2989 if (pmd_trans_huge(*pmd)) {
2990 page = pmd_page(*pmd);
2991 if (PageMlocked(page))
2995 } else if (!pmd_devmap(*pmd))
2997 __split_huge_pmd_locked(vma, pmd, haddr, false);
3000 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
3003 munlock_vma_page(page);
3009 static void split_huge_pmd_address(struct vm_area_struct *vma,
3010 unsigned long address)
3016 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
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)))
3030 * Caller holds the mmap_sem write mode, so a huge pmd cannot
3031 * materialize from under us.
3033 split_huge_pmd(vma, pmd, address);
3036 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3037 unsigned long start,
3042 * If the new start address isn't hpage aligned and it could
3043 * previously contain an hugepage: check if we need to split
3046 if (start & ~HPAGE_PMD_MASK &&
3047 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3048 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3049 split_huge_pmd_address(vma, start);
3052 * If the new end address isn't hpage aligned and it could
3053 * previously contain an hugepage: check if we need to split
3056 if (end & ~HPAGE_PMD_MASK &&
3057 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3058 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3059 split_huge_pmd_address(vma, end);
3062 * If we're also updating the vma->vm_next->vm_start, if the new
3063 * vm_next->vm_start isn't page aligned and it could previously
3064 * contain an hugepage: check if we need to split an huge pmd.
3066 if (adjust_next > 0) {
3067 struct vm_area_struct *next = vma->vm_next;
3068 unsigned long nstart = next->vm_start;
3069 nstart += adjust_next << PAGE_SHIFT;
3070 if (nstart & ~HPAGE_PMD_MASK &&
3071 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3072 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3073 split_huge_pmd_address(next, nstart);
3077 static void freeze_page_vma(struct vm_area_struct *vma, struct page *page,
3078 unsigned long address)
3080 unsigned long haddr = address & HPAGE_PMD_MASK;
3086 int i, nr = HPAGE_PMD_NR;
3088 /* Skip pages which doesn't belong to the VMA */
3089 if (address < vma->vm_start) {
3090 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3093 address = vma->vm_start;
3096 pgd = pgd_offset(vma->vm_mm, address);
3097 if (!pgd_present(*pgd))
3099 pud = pud_offset(pgd, address);
3100 if (!pud_present(*pud))
3102 pmd = pmd_offset(pud, address);
3103 ptl = pmd_lock(vma->vm_mm, pmd);
3104 if (!pmd_present(*pmd)) {
3108 if (pmd_trans_huge(*pmd)) {
3109 if (page == pmd_page(*pmd))
3110 __split_huge_pmd_locked(vma, pmd, haddr, true);
3116 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3117 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) {
3118 pte_t entry, swp_pte;
3119 swp_entry_t swp_entry;
3122 * We've just crossed page table boundary: need to map next one.
3123 * It can happen if THP was mremaped to non PMD-aligned address.
3125 if (unlikely(address == haddr + HPAGE_PMD_SIZE)) {
3126 pte_unmap_unlock(pte - 1, ptl);
3127 pmd = mm_find_pmd(vma->vm_mm, address);
3130 pte = pte_offset_map_lock(vma->vm_mm, pmd,
3134 if (!pte_present(*pte))
3136 if (page_to_pfn(page) != pte_pfn(*pte))
3138 flush_cache_page(vma, address, page_to_pfn(page));
3139 entry = ptep_clear_flush(vma, address, pte);
3140 if (pte_dirty(entry))
3142 swp_entry = make_migration_entry(page, pte_write(entry));
3143 swp_pte = swp_entry_to_pte(swp_entry);
3144 if (pte_soft_dirty(entry))
3145 swp_pte = pte_swp_mksoft_dirty(swp_pte);
3146 set_pte_at(vma->vm_mm, address, pte, swp_pte);
3147 page_remove_rmap(page, false);
3150 pte_unmap_unlock(pte - 1, ptl);
3153 static void freeze_page(struct anon_vma *anon_vma, struct page *page)
3155 struct anon_vma_chain *avc;
3156 pgoff_t pgoff = page_to_pgoff(page);
3158 VM_BUG_ON_PAGE(!PageHead(page), page);
3160 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff,
3161 pgoff + HPAGE_PMD_NR - 1) {
3162 unsigned long address = __vma_address(page, avc->vma);
3164 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3165 address, address + HPAGE_PMD_SIZE);
3166 freeze_page_vma(avc->vma, page, address);
3167 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3168 address, address + HPAGE_PMD_SIZE);
3172 static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page,
3173 unsigned long address)
3178 swp_entry_t swp_entry;
3179 unsigned long haddr = address & HPAGE_PMD_MASK;
3180 int i, nr = HPAGE_PMD_NR;
3182 /* Skip pages which doesn't belong to the VMA */
3183 if (address < vma->vm_start) {
3184 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3187 address = vma->vm_start;
3190 pmd = mm_find_pmd(vma->vm_mm, address);
3194 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3195 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) {
3197 * We've just crossed page table boundary: need to map next one.
3198 * It can happen if THP was mremaped to non-PMD aligned address.
3200 if (unlikely(address == haddr + HPAGE_PMD_SIZE)) {
3201 pte_unmap_unlock(pte - 1, ptl);
3202 pmd = mm_find_pmd(vma->vm_mm, address);
3205 pte = pte_offset_map_lock(vma->vm_mm, pmd,
3209 if (!is_swap_pte(*pte))
3212 swp_entry = pte_to_swp_entry(*pte);
3213 if (!is_migration_entry(swp_entry))
3215 if (migration_entry_to_page(swp_entry) != page)
3219 page_add_anon_rmap(page, vma, address, false);
3221 entry = pte_mkold(mk_pte(page, vma->vm_page_prot));
3222 if (PageDirty(page))
3223 entry = pte_mkdirty(entry);
3224 if (is_write_migration_entry(swp_entry))
3225 entry = maybe_mkwrite(entry, vma);
3227 flush_dcache_page(page);
3228 set_pte_at(vma->vm_mm, address, pte, entry);
3230 /* No need to invalidate - it was non-present before */
3231 update_mmu_cache(vma, address, pte);
3233 pte_unmap_unlock(pte - 1, ptl);
3236 static void unfreeze_page(struct anon_vma *anon_vma, struct page *page)
3238 struct anon_vma_chain *avc;
3239 pgoff_t pgoff = page_to_pgoff(page);
3241 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
3242 pgoff, pgoff + HPAGE_PMD_NR - 1) {
3243 unsigned long address = __vma_address(page, avc->vma);
3245 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3246 address, address + HPAGE_PMD_SIZE);
3247 unfreeze_page_vma(avc->vma, page, address);
3248 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3249 address, address + HPAGE_PMD_SIZE);
3253 static void __split_huge_page_tail(struct page *head, int tail,
3254 struct lruvec *lruvec, struct list_head *list)
3256 struct page *page_tail = head + tail;
3258 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
3259 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
3262 * tail_page->_count is zero and not changing from under us. But
3263 * get_page_unless_zero() may be running from under us on the
3264 * tail_page. If we used atomic_set() below instead of atomic_inc(), we
3265 * would then run atomic_set() concurrently with
3266 * get_page_unless_zero(), and atomic_set() is implemented in C not
3267 * using locked ops. spin_unlock on x86 sometime uses locked ops
3268 * because of PPro errata 66, 92, so unless somebody can guarantee
3269 * atomic_set() here would be safe on all archs (and not only on x86),
3270 * it's safer to use atomic_inc().
3272 page_ref_inc(page_tail);
3274 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3275 page_tail->flags |= (head->flags &
3276 ((1L << PG_referenced) |
3277 (1L << PG_swapbacked) |
3278 (1L << PG_mlocked) |
3279 (1L << PG_uptodate) |
3282 (1L << PG_unevictable) |
3286 * After clearing PageTail the gup refcount can be released.
3287 * Page flags also must be visible before we make the page non-compound.
3291 clear_compound_head(page_tail);
3293 if (page_is_young(head))
3294 set_page_young(page_tail);
3295 if (page_is_idle(head))
3296 set_page_idle(page_tail);
3298 /* ->mapping in first tail page is compound_mapcount */
3299 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3301 page_tail->mapping = head->mapping;
3303 page_tail->index = head->index + tail;
3304 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3305 lru_add_page_tail(head, page_tail, lruvec, list);
3308 static void __split_huge_page(struct page *page, struct list_head *list)
3310 struct page *head = compound_head(page);
3311 struct zone *zone = page_zone(head);
3312 struct lruvec *lruvec;
3315 /* prevent PageLRU to go away from under us, and freeze lru stats */
3316 spin_lock_irq(&zone->lru_lock);
3317 lruvec = mem_cgroup_page_lruvec(head, zone);
3319 /* complete memcg works before add pages to LRU */
3320 mem_cgroup_split_huge_fixup(head);
3322 for (i = HPAGE_PMD_NR - 1; i >= 1; i--)
3323 __split_huge_page_tail(head, i, lruvec, list);
3325 ClearPageCompound(head);
3326 spin_unlock_irq(&zone->lru_lock);
3328 unfreeze_page(page_anon_vma(head), head);
3330 for (i = 0; i < HPAGE_PMD_NR; i++) {
3331 struct page *subpage = head + i;
3332 if (subpage == page)
3334 unlock_page(subpage);
3337 * Subpages may be freed if there wasn't any mapping
3338 * like if add_to_swap() is running on a lru page that
3339 * had its mapping zapped. And freeing these pages
3340 * requires taking the lru_lock so we do the put_page
3341 * of the tail pages after the split is complete.
3347 int total_mapcount(struct page *page)
3351 VM_BUG_ON_PAGE(PageTail(page), page);
3353 if (likely(!PageCompound(page)))
3354 return atomic_read(&page->_mapcount) + 1;
3356 ret = compound_mapcount(page);
3359 for (i = 0; i < HPAGE_PMD_NR; i++)
3360 ret += atomic_read(&page[i]._mapcount) + 1;
3361 if (PageDoubleMap(page))
3362 ret -= HPAGE_PMD_NR;
3367 * This function splits huge page into normal pages. @page can point to any
3368 * subpage of huge page to split. Split doesn't change the position of @page.
3370 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3371 * The huge page must be locked.
3373 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3375 * Both head page and tail pages will inherit mapping, flags, and so on from
3378 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3379 * they are not mapped.
3381 * Returns 0 if the hugepage is split successfully.
3382 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3385 int split_huge_page_to_list(struct page *page, struct list_head *list)
3387 struct page *head = compound_head(page);
3388 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
3389 struct anon_vma *anon_vma;
3390 int count, mapcount, ret;
3392 unsigned long flags;
3394 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3395 VM_BUG_ON_PAGE(!PageAnon(page), page);
3396 VM_BUG_ON_PAGE(!PageLocked(page), page);
3397 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3398 VM_BUG_ON_PAGE(!PageCompound(page), page);
3401 * The caller does not necessarily hold an mmap_sem that would prevent
3402 * the anon_vma disappearing so we first we take a reference to it
3403 * and then lock the anon_vma for write. This is similar to
3404 * page_lock_anon_vma_read except the write lock is taken to serialise
3405 * against parallel split or collapse operations.
3407 anon_vma = page_get_anon_vma(head);
3412 anon_vma_lock_write(anon_vma);
3415 * Racy check if we can split the page, before freeze_page() will
3418 if (total_mapcount(head) != page_count(head) - 1) {
3423 mlocked = PageMlocked(page);
3424 freeze_page(anon_vma, head);
3425 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3427 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3431 /* Prevent deferred_split_scan() touching ->_count */
3432 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3433 count = page_count(head);
3434 mapcount = total_mapcount(head);
3435 if (!mapcount && count == 1) {
3436 if (!list_empty(page_deferred_list(head))) {
3437 pgdata->split_queue_len--;
3438 list_del(page_deferred_list(head));
3440 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3441 __split_huge_page(page, list);
3443 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
3444 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3445 pr_alert("total_mapcount: %u, page_count(): %u\n",
3448 dump_page(head, NULL);
3449 dump_page(page, "total_mapcount(head) > 0");
3452 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3453 unfreeze_page(anon_vma, head);
3458 anon_vma_unlock_write(anon_vma);
3459 put_anon_vma(anon_vma);
3461 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3465 void free_transhuge_page(struct page *page)
3467 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3468 unsigned long flags;
3470 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3471 if (!list_empty(page_deferred_list(page))) {
3472 pgdata->split_queue_len--;
3473 list_del(page_deferred_list(page));
3475 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3476 free_compound_page(page);
3479 void deferred_split_huge_page(struct page *page)
3481 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3482 unsigned long flags;
3484 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3486 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3487 if (list_empty(page_deferred_list(page))) {
3488 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
3489 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
3490 pgdata->split_queue_len++;
3492 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3495 static unsigned long deferred_split_count(struct shrinker *shrink,
3496 struct shrink_control *sc)
3498 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3499 return ACCESS_ONCE(pgdata->split_queue_len);
3502 static unsigned long deferred_split_scan(struct shrinker *shrink,
3503 struct shrink_control *sc)
3505 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3506 unsigned long flags;
3507 LIST_HEAD(list), *pos, *next;
3511 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3512 /* Take pin on all head pages to avoid freeing them under us */
3513 list_for_each_safe(pos, next, &pgdata->split_queue) {
3514 page = list_entry((void *)pos, struct page, mapping);
3515 page = compound_head(page);
3516 if (get_page_unless_zero(page)) {
3517 list_move(page_deferred_list(page), &list);
3519 /* We lost race with put_compound_page() */
3520 list_del_init(page_deferred_list(page));
3521 pgdata->split_queue_len--;
3523 if (!--sc->nr_to_scan)
3526 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3528 list_for_each_safe(pos, next, &list) {
3529 page = list_entry((void *)pos, struct page, mapping);
3531 /* split_huge_page() removes page from list on success */
3532 if (!split_huge_page(page))
3538 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3539 list_splice_tail(&list, &pgdata->split_queue);
3540 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3543 * Stop shrinker if we didn't split any page, but the queue is empty.
3544 * This can happen if pages were freed under us.
3546 if (!split && list_empty(&pgdata->split_queue))
3551 static struct shrinker deferred_split_shrinker = {
3552 .count_objects = deferred_split_count,
3553 .scan_objects = deferred_split_scan,
3554 .seeks = DEFAULT_SEEKS,
3555 .flags = SHRINKER_NUMA_AWARE,
3558 #ifdef CONFIG_DEBUG_FS
3559 static int split_huge_pages_set(void *data, u64 val)
3563 unsigned long pfn, max_zone_pfn;
3564 unsigned long total = 0, split = 0;
3569 for_each_populated_zone(zone) {
3570 max_zone_pfn = zone_end_pfn(zone);
3571 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3572 if (!pfn_valid(pfn))
3575 page = pfn_to_page(pfn);
3576 if (!get_page_unless_zero(page))
3579 if (zone != page_zone(page))
3582 if (!PageHead(page) || !PageAnon(page) ||
3588 if (!split_huge_page(page))
3596 pr_info("%lu of %lu THP split", split, total);
3600 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3603 static int __init split_huge_pages_debugfs(void)
3607 ret = debugfs_create_file("split_huge_pages", 0644, NULL, NULL,
3608 &split_huge_pages_fops);
3610 pr_warn("Failed to create split_huge_pages in debugfs");
3613 late_initcall(split_huge_pages_debugfs);