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/kthread.h>
20 #include <linux/khugepaged.h>
21 #include <linux/freezer.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/migrate.h>
25 #include <linux/hashtable.h>
28 #include <asm/pgalloc.h>
32 * By default transparent hugepage support is disabled in order that avoid
33 * to risk increase the memory footprint of applications without a guaranteed
34 * benefit. When transparent hugepage support is enabled, is for all mappings,
35 * and khugepaged scans all mappings.
36 * Defrag is invoked by khugepaged hugepage allocations and by page faults
37 * for all hugepage allocations.
39 unsigned long transparent_hugepage_flags __read_mostly =
40 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
41 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
43 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
44 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
46 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
47 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
48 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
50 /* default scan 8*512 pte (or vmas) every 30 second */
51 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
52 static unsigned int khugepaged_pages_collapsed;
53 static unsigned int khugepaged_full_scans;
54 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
55 /* during fragmentation poll the hugepage allocator once every minute */
56 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
57 static struct task_struct *khugepaged_thread __read_mostly;
58 static DEFINE_MUTEX(khugepaged_mutex);
59 static DEFINE_SPINLOCK(khugepaged_mm_lock);
60 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
62 * default collapse hugepages if there is at least one pte mapped like
63 * it would have happened if the vma was large enough during page
66 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
68 static int khugepaged(void *none);
69 static int khugepaged_slab_init(void);
70 static void khugepaged_slab_exit(void);
72 #define MM_SLOTS_HASH_BITS 10
73 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
75 static struct kmem_cache *mm_slot_cache __read_mostly;
78 * struct mm_slot - hash lookup from mm to mm_slot
79 * @hash: hash collision list
80 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
81 * @mm: the mm that this information is valid for
84 struct hlist_node hash;
85 struct list_head mm_node;
90 * struct khugepaged_scan - cursor for scanning
91 * @mm_head: the head of the mm list to scan
92 * @mm_slot: the current mm_slot we are scanning
93 * @address: the next address inside that to be scanned
95 * There is only the one khugepaged_scan instance of this cursor structure.
97 struct khugepaged_scan {
98 struct list_head mm_head;
99 struct mm_slot *mm_slot;
100 unsigned long address;
102 static struct khugepaged_scan khugepaged_scan = {
103 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
107 static int set_recommended_min_free_kbytes(void)
111 unsigned long recommended_min;
113 for_each_populated_zone(zone)
116 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
117 recommended_min = pageblock_nr_pages * nr_zones * 2;
120 * Make sure that on average at least two pageblocks are almost free
121 * of another type, one for a migratetype to fall back to and a
122 * second to avoid subsequent fallbacks of other types There are 3
123 * MIGRATE_TYPES we care about.
125 recommended_min += pageblock_nr_pages * nr_zones *
126 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
128 /* don't ever allow to reserve more than 5% of the lowmem */
129 recommended_min = min(recommended_min,
130 (unsigned long) nr_free_buffer_pages() / 20);
131 recommended_min <<= (PAGE_SHIFT-10);
133 if (recommended_min > min_free_kbytes) {
134 if (user_min_free_kbytes >= 0)
135 pr_info("raising min_free_kbytes from %d to %lu "
136 "to help transparent hugepage allocations\n",
137 min_free_kbytes, recommended_min);
139 min_free_kbytes = recommended_min;
141 setup_per_zone_wmarks();
145 static int start_stop_khugepaged(void)
148 if (khugepaged_enabled()) {
149 if (!khugepaged_thread)
150 khugepaged_thread = kthread_run(khugepaged, NULL,
152 if (unlikely(IS_ERR(khugepaged_thread))) {
153 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
154 err = PTR_ERR(khugepaged_thread);
155 khugepaged_thread = NULL;
159 if (!list_empty(&khugepaged_scan.mm_head))
160 wake_up_interruptible(&khugepaged_wait);
162 set_recommended_min_free_kbytes();
163 } else if (khugepaged_thread) {
164 kthread_stop(khugepaged_thread);
165 khugepaged_thread = NULL;
171 static atomic_t huge_zero_refcount;
172 struct page *huge_zero_page __read_mostly;
174 static inline bool is_huge_zero_pmd(pmd_t pmd)
176 return is_huge_zero_page(pmd_page(pmd));
179 static struct page *get_huge_zero_page(void)
181 struct page *zero_page;
183 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
184 return READ_ONCE(huge_zero_page);
186 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
189 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
192 count_vm_event(THP_ZERO_PAGE_ALLOC);
194 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
196 __free_pages(zero_page, compound_order(zero_page));
200 /* We take additional reference here. It will be put back by shrinker */
201 atomic_set(&huge_zero_refcount, 2);
203 return READ_ONCE(huge_zero_page);
206 static void put_huge_zero_page(void)
209 * Counter should never go to zero here. Only shrinker can put
212 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
215 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
216 struct shrink_control *sc)
218 /* we can free zero page only if last reference remains */
219 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
222 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
223 struct shrink_control *sc)
225 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
226 struct page *zero_page = xchg(&huge_zero_page, NULL);
227 BUG_ON(zero_page == NULL);
228 __free_pages(zero_page, compound_order(zero_page));
235 static struct shrinker huge_zero_page_shrinker = {
236 .count_objects = shrink_huge_zero_page_count,
237 .scan_objects = shrink_huge_zero_page_scan,
238 .seeks = DEFAULT_SEEKS,
243 static ssize_t double_flag_show(struct kobject *kobj,
244 struct kobj_attribute *attr, char *buf,
245 enum transparent_hugepage_flag enabled,
246 enum transparent_hugepage_flag req_madv)
248 if (test_bit(enabled, &transparent_hugepage_flags)) {
249 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
250 return sprintf(buf, "[always] madvise never\n");
251 } else if (test_bit(req_madv, &transparent_hugepage_flags))
252 return sprintf(buf, "always [madvise] never\n");
254 return sprintf(buf, "always madvise [never]\n");
256 static ssize_t double_flag_store(struct kobject *kobj,
257 struct kobj_attribute *attr,
258 const char *buf, size_t count,
259 enum transparent_hugepage_flag enabled,
260 enum transparent_hugepage_flag req_madv)
262 if (!memcmp("always", buf,
263 min(sizeof("always")-1, count))) {
264 set_bit(enabled, &transparent_hugepage_flags);
265 clear_bit(req_madv, &transparent_hugepage_flags);
266 } else if (!memcmp("madvise", buf,
267 min(sizeof("madvise")-1, count))) {
268 clear_bit(enabled, &transparent_hugepage_flags);
269 set_bit(req_madv, &transparent_hugepage_flags);
270 } else if (!memcmp("never", buf,
271 min(sizeof("never")-1, count))) {
272 clear_bit(enabled, &transparent_hugepage_flags);
273 clear_bit(req_madv, &transparent_hugepage_flags);
280 static ssize_t enabled_show(struct kobject *kobj,
281 struct kobj_attribute *attr, char *buf)
283 return double_flag_show(kobj, attr, buf,
284 TRANSPARENT_HUGEPAGE_FLAG,
285 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
287 static ssize_t enabled_store(struct kobject *kobj,
288 struct kobj_attribute *attr,
289 const char *buf, size_t count)
293 ret = double_flag_store(kobj, attr, buf, count,
294 TRANSPARENT_HUGEPAGE_FLAG,
295 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
300 mutex_lock(&khugepaged_mutex);
301 err = start_stop_khugepaged();
302 mutex_unlock(&khugepaged_mutex);
310 static struct kobj_attribute enabled_attr =
311 __ATTR(enabled, 0644, enabled_show, enabled_store);
313 static ssize_t single_flag_show(struct kobject *kobj,
314 struct kobj_attribute *attr, char *buf,
315 enum transparent_hugepage_flag flag)
317 return sprintf(buf, "%d\n",
318 !!test_bit(flag, &transparent_hugepage_flags));
321 static ssize_t single_flag_store(struct kobject *kobj,
322 struct kobj_attribute *attr,
323 const char *buf, size_t count,
324 enum transparent_hugepage_flag flag)
329 ret = kstrtoul(buf, 10, &value);
336 set_bit(flag, &transparent_hugepage_flags);
338 clear_bit(flag, &transparent_hugepage_flags);
344 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
345 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
346 * memory just to allocate one more hugepage.
348 static ssize_t defrag_show(struct kobject *kobj,
349 struct kobj_attribute *attr, char *buf)
351 return double_flag_show(kobj, attr, buf,
352 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
353 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
355 static ssize_t defrag_store(struct kobject *kobj,
356 struct kobj_attribute *attr,
357 const char *buf, size_t count)
359 return double_flag_store(kobj, attr, buf, count,
360 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
361 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
363 static struct kobj_attribute defrag_attr =
364 __ATTR(defrag, 0644, defrag_show, defrag_store);
366 static ssize_t use_zero_page_show(struct kobject *kobj,
367 struct kobj_attribute *attr, char *buf)
369 return single_flag_show(kobj, attr, buf,
370 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
372 static ssize_t use_zero_page_store(struct kobject *kobj,
373 struct kobj_attribute *attr, const char *buf, size_t count)
375 return single_flag_store(kobj, attr, buf, count,
376 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
378 static struct kobj_attribute use_zero_page_attr =
379 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
380 #ifdef CONFIG_DEBUG_VM
381 static ssize_t debug_cow_show(struct kobject *kobj,
382 struct kobj_attribute *attr, char *buf)
384 return single_flag_show(kobj, attr, buf,
385 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
387 static ssize_t debug_cow_store(struct kobject *kobj,
388 struct kobj_attribute *attr,
389 const char *buf, size_t count)
391 return single_flag_store(kobj, attr, buf, count,
392 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
394 static struct kobj_attribute debug_cow_attr =
395 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
396 #endif /* CONFIG_DEBUG_VM */
398 static struct attribute *hugepage_attr[] = {
401 &use_zero_page_attr.attr,
402 #ifdef CONFIG_DEBUG_VM
403 &debug_cow_attr.attr,
408 static struct attribute_group hugepage_attr_group = {
409 .attrs = hugepage_attr,
412 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
413 struct kobj_attribute *attr,
416 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
419 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
420 struct kobj_attribute *attr,
421 const char *buf, size_t count)
426 err = kstrtoul(buf, 10, &msecs);
427 if (err || msecs > UINT_MAX)
430 khugepaged_scan_sleep_millisecs = msecs;
431 wake_up_interruptible(&khugepaged_wait);
435 static struct kobj_attribute scan_sleep_millisecs_attr =
436 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
437 scan_sleep_millisecs_store);
439 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
440 struct kobj_attribute *attr,
443 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
446 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
447 struct kobj_attribute *attr,
448 const char *buf, size_t count)
453 err = kstrtoul(buf, 10, &msecs);
454 if (err || msecs > UINT_MAX)
457 khugepaged_alloc_sleep_millisecs = msecs;
458 wake_up_interruptible(&khugepaged_wait);
462 static struct kobj_attribute alloc_sleep_millisecs_attr =
463 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
464 alloc_sleep_millisecs_store);
466 static ssize_t pages_to_scan_show(struct kobject *kobj,
467 struct kobj_attribute *attr,
470 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
472 static ssize_t pages_to_scan_store(struct kobject *kobj,
473 struct kobj_attribute *attr,
474 const char *buf, size_t count)
479 err = kstrtoul(buf, 10, &pages);
480 if (err || !pages || pages > UINT_MAX)
483 khugepaged_pages_to_scan = pages;
487 static struct kobj_attribute pages_to_scan_attr =
488 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
489 pages_to_scan_store);
491 static ssize_t pages_collapsed_show(struct kobject *kobj,
492 struct kobj_attribute *attr,
495 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
497 static struct kobj_attribute pages_collapsed_attr =
498 __ATTR_RO(pages_collapsed);
500 static ssize_t full_scans_show(struct kobject *kobj,
501 struct kobj_attribute *attr,
504 return sprintf(buf, "%u\n", khugepaged_full_scans);
506 static struct kobj_attribute full_scans_attr =
507 __ATTR_RO(full_scans);
509 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
510 struct kobj_attribute *attr, char *buf)
512 return single_flag_show(kobj, attr, buf,
513 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
515 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
516 struct kobj_attribute *attr,
517 const char *buf, size_t count)
519 return single_flag_store(kobj, attr, buf, count,
520 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
522 static struct kobj_attribute khugepaged_defrag_attr =
523 __ATTR(defrag, 0644, khugepaged_defrag_show,
524 khugepaged_defrag_store);
527 * max_ptes_none controls if khugepaged should collapse hugepages over
528 * any unmapped ptes in turn potentially increasing the memory
529 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
530 * reduce the available free memory in the system as it
531 * runs. Increasing max_ptes_none will instead potentially reduce the
532 * free memory in the system during the khugepaged scan.
534 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
535 struct kobj_attribute *attr,
538 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
540 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
541 struct kobj_attribute *attr,
542 const char *buf, size_t count)
545 unsigned long max_ptes_none;
547 err = kstrtoul(buf, 10, &max_ptes_none);
548 if (err || max_ptes_none > HPAGE_PMD_NR-1)
551 khugepaged_max_ptes_none = max_ptes_none;
555 static struct kobj_attribute khugepaged_max_ptes_none_attr =
556 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
557 khugepaged_max_ptes_none_store);
559 static struct attribute *khugepaged_attr[] = {
560 &khugepaged_defrag_attr.attr,
561 &khugepaged_max_ptes_none_attr.attr,
562 &pages_to_scan_attr.attr,
563 &pages_collapsed_attr.attr,
564 &full_scans_attr.attr,
565 &scan_sleep_millisecs_attr.attr,
566 &alloc_sleep_millisecs_attr.attr,
570 static struct attribute_group khugepaged_attr_group = {
571 .attrs = khugepaged_attr,
572 .name = "khugepaged",
575 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
579 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
580 if (unlikely(!*hugepage_kobj)) {
581 pr_err("failed to create transparent hugepage kobject\n");
585 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
587 pr_err("failed to register transparent hugepage group\n");
591 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
593 pr_err("failed to register transparent hugepage group\n");
594 goto remove_hp_group;
600 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
602 kobject_put(*hugepage_kobj);
606 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
608 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
609 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
610 kobject_put(hugepage_kobj);
613 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
618 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
621 #endif /* CONFIG_SYSFS */
623 static int __init hugepage_init(void)
626 struct kobject *hugepage_kobj;
628 if (!has_transparent_hugepage()) {
629 transparent_hugepage_flags = 0;
633 err = hugepage_init_sysfs(&hugepage_kobj);
637 err = khugepaged_slab_init();
641 err = register_shrinker(&huge_zero_page_shrinker);
643 goto err_hzp_shrinker;
646 * By default disable transparent hugepages on smaller systems,
647 * where the extra memory used could hurt more than TLB overhead
648 * is likely to save. The admin can still enable it through /sys.
650 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
651 transparent_hugepage_flags = 0;
655 err = start_stop_khugepaged();
661 unregister_shrinker(&huge_zero_page_shrinker);
663 khugepaged_slab_exit();
665 hugepage_exit_sysfs(hugepage_kobj);
669 subsys_initcall(hugepage_init);
671 static int __init setup_transparent_hugepage(char *str)
676 if (!strcmp(str, "always")) {
677 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
678 &transparent_hugepage_flags);
679 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
680 &transparent_hugepage_flags);
682 } else if (!strcmp(str, "madvise")) {
683 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
684 &transparent_hugepage_flags);
685 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
686 &transparent_hugepage_flags);
688 } else if (!strcmp(str, "never")) {
689 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
690 &transparent_hugepage_flags);
691 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
692 &transparent_hugepage_flags);
697 pr_warn("transparent_hugepage= cannot parse, ignored\n");
700 __setup("transparent_hugepage=", setup_transparent_hugepage);
702 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
704 if (likely(vma->vm_flags & VM_WRITE))
705 pmd = pmd_mkwrite(pmd);
709 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
712 entry = mk_pmd(page, prot);
713 entry = pmd_mkhuge(entry);
717 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
718 struct vm_area_struct *vma,
719 unsigned long haddr, pmd_t *pmd,
720 struct page *page, gfp_t gfp)
722 struct mem_cgroup *memcg;
726 VM_BUG_ON_PAGE(!PageCompound(page), page);
728 if (mem_cgroup_try_charge(page, mm, gfp, &memcg))
731 pgtable = pte_alloc_one(mm, haddr);
732 if (unlikely(!pgtable)) {
733 mem_cgroup_cancel_charge(page, memcg);
737 clear_huge_page(page, haddr, HPAGE_PMD_NR);
739 * The memory barrier inside __SetPageUptodate makes sure that
740 * clear_huge_page writes become visible before the set_pmd_at()
743 __SetPageUptodate(page);
745 ptl = pmd_lock(mm, pmd);
746 if (unlikely(!pmd_none(*pmd))) {
748 mem_cgroup_cancel_charge(page, memcg);
750 pte_free(mm, pgtable);
753 entry = mk_huge_pmd(page, vma->vm_page_prot);
754 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
755 page_add_new_anon_rmap(page, vma, haddr);
756 mem_cgroup_commit_charge(page, memcg, false);
757 lru_cache_add_active_or_unevictable(page, vma);
758 pgtable_trans_huge_deposit(mm, pmd, pgtable);
759 set_pmd_at(mm, haddr, pmd, entry);
760 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
761 atomic_long_inc(&mm->nr_ptes);
768 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
770 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
773 /* Caller must hold page table lock. */
774 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
775 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
776 struct page *zero_page)
781 entry = mk_pmd(zero_page, vma->vm_page_prot);
782 entry = pmd_mkhuge(entry);
783 pgtable_trans_huge_deposit(mm, pmd, pgtable);
784 set_pmd_at(mm, haddr, pmd, entry);
785 atomic_long_inc(&mm->nr_ptes);
789 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
790 unsigned long address, pmd_t *pmd,
795 unsigned long haddr = address & HPAGE_PMD_MASK;
797 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
798 return VM_FAULT_FALLBACK;
799 if (unlikely(anon_vma_prepare(vma)))
801 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
803 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
804 transparent_hugepage_use_zero_page()) {
807 struct page *zero_page;
809 pgtable = pte_alloc_one(mm, haddr);
810 if (unlikely(!pgtable))
812 zero_page = get_huge_zero_page();
813 if (unlikely(!zero_page)) {
814 pte_free(mm, pgtable);
815 count_vm_event(THP_FAULT_FALLBACK);
816 return VM_FAULT_FALLBACK;
818 ptl = pmd_lock(mm, pmd);
819 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
823 pte_free(mm, pgtable);
824 put_huge_zero_page();
828 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
829 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
830 if (unlikely(!page)) {
831 count_vm_event(THP_FAULT_FALLBACK);
832 return VM_FAULT_FALLBACK;
834 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page, gfp))) {
836 count_vm_event(THP_FAULT_FALLBACK);
837 return VM_FAULT_FALLBACK;
840 count_vm_event(THP_FAULT_ALLOC);
844 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
845 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
846 struct vm_area_struct *vma)
848 spinlock_t *dst_ptl, *src_ptl;
849 struct page *src_page;
855 pgtable = pte_alloc_one(dst_mm, addr);
856 if (unlikely(!pgtable))
859 dst_ptl = pmd_lock(dst_mm, dst_pmd);
860 src_ptl = pmd_lockptr(src_mm, src_pmd);
861 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
865 if (unlikely(!pmd_trans_huge(pmd))) {
866 pte_free(dst_mm, pgtable);
870 * When page table lock is held, the huge zero pmd should not be
871 * under splitting since we don't split the page itself, only pmd to
874 if (is_huge_zero_pmd(pmd)) {
875 struct page *zero_page;
878 * get_huge_zero_page() will never allocate a new page here,
879 * since we already have a zero page to copy. It just takes a
882 zero_page = get_huge_zero_page();
883 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
885 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
890 if (unlikely(pmd_trans_splitting(pmd))) {
891 /* split huge page running from under us */
892 spin_unlock(src_ptl);
893 spin_unlock(dst_ptl);
894 pte_free(dst_mm, pgtable);
896 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
899 src_page = pmd_page(pmd);
900 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
902 page_dup_rmap(src_page);
903 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
905 pmdp_set_wrprotect(src_mm, addr, src_pmd);
906 pmd = pmd_mkold(pmd_wrprotect(pmd));
907 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
908 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
909 atomic_long_inc(&dst_mm->nr_ptes);
913 spin_unlock(src_ptl);
914 spin_unlock(dst_ptl);
919 void huge_pmd_set_accessed(struct mm_struct *mm,
920 struct vm_area_struct *vma,
921 unsigned long address,
922 pmd_t *pmd, pmd_t orig_pmd,
929 ptl = pmd_lock(mm, pmd);
930 if (unlikely(!pmd_same(*pmd, orig_pmd)))
933 entry = pmd_mkyoung(orig_pmd);
934 haddr = address & HPAGE_PMD_MASK;
935 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
936 update_mmu_cache_pmd(vma, address, pmd);
943 * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages
944 * during copy_user_huge_page()'s copy_page_rep(): in the case when
945 * the source page gets split and a tail freed before copy completes.
946 * Called under pmd_lock of checked pmd, so safe from splitting itself.
948 static void get_user_huge_page(struct page *page)
950 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
951 struct page *endpage = page + HPAGE_PMD_NR;
953 atomic_add(HPAGE_PMD_NR, &page->_count);
954 while (++page < endpage)
955 get_huge_page_tail(page);
961 static void put_user_huge_page(struct page *page)
963 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
964 struct page *endpage = page + HPAGE_PMD_NR;
966 while (page < endpage)
973 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
974 struct vm_area_struct *vma,
975 unsigned long address,
976 pmd_t *pmd, pmd_t orig_pmd,
980 struct mem_cgroup *memcg;
986 unsigned long mmun_start; /* For mmu_notifiers */
987 unsigned long mmun_end; /* For mmu_notifiers */
989 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
991 if (unlikely(!pages)) {
996 for (i = 0; i < HPAGE_PMD_NR; i++) {
997 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
999 vma, address, page_to_nid(page));
1000 if (unlikely(!pages[i] ||
1001 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1006 memcg = (void *)page_private(pages[i]);
1007 set_page_private(pages[i], 0);
1008 mem_cgroup_cancel_charge(pages[i], memcg);
1012 ret |= VM_FAULT_OOM;
1015 set_page_private(pages[i], (unsigned long)memcg);
1018 for (i = 0; i < HPAGE_PMD_NR; i++) {
1019 copy_user_highpage(pages[i], page + i,
1020 haddr + PAGE_SIZE * i, vma);
1021 __SetPageUptodate(pages[i]);
1026 mmun_end = haddr + HPAGE_PMD_SIZE;
1027 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1029 ptl = pmd_lock(mm, pmd);
1030 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1031 goto out_free_pages;
1032 VM_BUG_ON_PAGE(!PageHead(page), page);
1034 pmdp_clear_flush_notify(vma, haddr, pmd);
1035 /* leave pmd empty until pte is filled */
1037 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1038 pmd_populate(mm, &_pmd, pgtable);
1040 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1042 entry = mk_pte(pages[i], vma->vm_page_prot);
1043 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1044 memcg = (void *)page_private(pages[i]);
1045 set_page_private(pages[i], 0);
1046 page_add_new_anon_rmap(pages[i], vma, haddr);
1047 mem_cgroup_commit_charge(pages[i], memcg, false);
1048 lru_cache_add_active_or_unevictable(pages[i], vma);
1049 pte = pte_offset_map(&_pmd, haddr);
1050 VM_BUG_ON(!pte_none(*pte));
1051 set_pte_at(mm, haddr, pte, entry);
1056 smp_wmb(); /* make pte visible before pmd */
1057 pmd_populate(mm, pmd, pgtable);
1058 page_remove_rmap(page);
1061 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1063 ret |= VM_FAULT_WRITE;
1071 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1072 for (i = 0; i < HPAGE_PMD_NR; i++) {
1073 memcg = (void *)page_private(pages[i]);
1074 set_page_private(pages[i], 0);
1075 mem_cgroup_cancel_charge(pages[i], memcg);
1082 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1083 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1087 struct page *page = NULL, *new_page;
1088 struct mem_cgroup *memcg;
1089 unsigned long haddr;
1090 unsigned long mmun_start; /* For mmu_notifiers */
1091 unsigned long mmun_end; /* For mmu_notifiers */
1092 gfp_t huge_gfp; /* for allocation and charge */
1094 ptl = pmd_lockptr(mm, pmd);
1095 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1096 haddr = address & HPAGE_PMD_MASK;
1097 if (is_huge_zero_pmd(orig_pmd))
1100 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1103 page = pmd_page(orig_pmd);
1104 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1105 if (page_mapcount(page) == 1) {
1107 entry = pmd_mkyoung(orig_pmd);
1108 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1109 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1110 update_mmu_cache_pmd(vma, address, pmd);
1111 ret |= VM_FAULT_WRITE;
1114 get_user_huge_page(page);
1117 if (transparent_hugepage_enabled(vma) &&
1118 !transparent_hugepage_debug_cow()) {
1119 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1120 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1124 if (unlikely(!new_page)) {
1126 split_huge_page_pmd(vma, address, pmd);
1127 ret |= VM_FAULT_FALLBACK;
1129 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1130 pmd, orig_pmd, page, haddr);
1131 if (ret & VM_FAULT_OOM) {
1132 split_huge_page(page);
1133 ret |= VM_FAULT_FALLBACK;
1135 put_user_huge_page(page);
1137 count_vm_event(THP_FAULT_FALLBACK);
1141 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) {
1144 split_huge_page(page);
1145 put_user_huge_page(page);
1147 split_huge_page_pmd(vma, address, pmd);
1148 ret |= VM_FAULT_FALLBACK;
1149 count_vm_event(THP_FAULT_FALLBACK);
1153 count_vm_event(THP_FAULT_ALLOC);
1156 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1158 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1159 __SetPageUptodate(new_page);
1162 mmun_end = haddr + HPAGE_PMD_SIZE;
1163 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1167 put_user_huge_page(page);
1168 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1170 mem_cgroup_cancel_charge(new_page, memcg);
1175 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1176 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1177 pmdp_clear_flush_notify(vma, haddr, pmd);
1178 page_add_new_anon_rmap(new_page, vma, haddr);
1179 mem_cgroup_commit_charge(new_page, memcg, false);
1180 lru_cache_add_active_or_unevictable(new_page, vma);
1181 set_pmd_at(mm, haddr, pmd, entry);
1182 update_mmu_cache_pmd(vma, address, pmd);
1184 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1185 put_huge_zero_page();
1187 VM_BUG_ON_PAGE(!PageHead(page), page);
1188 page_remove_rmap(page);
1191 ret |= VM_FAULT_WRITE;
1195 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1203 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1208 struct mm_struct *mm = vma->vm_mm;
1209 struct page *page = NULL;
1211 assert_spin_locked(pmd_lockptr(mm, pmd));
1213 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1216 /* Avoid dumping huge zero page */
1217 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1218 return ERR_PTR(-EFAULT);
1220 /* Full NUMA hinting faults to serialise migration in fault paths */
1221 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1224 page = pmd_page(*pmd);
1225 VM_BUG_ON_PAGE(!PageHead(page), page);
1226 if (flags & FOLL_TOUCH) {
1229 * We should set the dirty bit only for FOLL_WRITE but
1230 * for now the dirty bit in the pmd is meaningless.
1231 * And if the dirty bit will become meaningful and
1232 * we'll only set it with FOLL_WRITE, an atomic
1233 * set_bit will be required on the pmd to set the
1234 * young bit, instead of the current set_pmd_at.
1236 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1237 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1239 update_mmu_cache_pmd(vma, addr, pmd);
1241 if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
1242 if (page->mapping && trylock_page(page)) {
1245 mlock_vma_page(page);
1249 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1250 VM_BUG_ON_PAGE(!PageCompound(page), page);
1251 if (flags & FOLL_GET)
1252 get_page_foll(page);
1258 /* NUMA hinting page fault entry point for trans huge pmds */
1259 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1260 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1263 struct anon_vma *anon_vma = NULL;
1265 unsigned long haddr = addr & HPAGE_PMD_MASK;
1266 int page_nid = -1, this_nid = numa_node_id();
1267 int target_nid, last_cpupid = -1;
1269 bool migrated = false;
1273 /* A PROT_NONE fault should not end up here */
1274 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1276 ptl = pmd_lock(mm, pmdp);
1277 if (unlikely(!pmd_same(pmd, *pmdp)))
1281 * If there are potential migrations, wait for completion and retry
1282 * without disrupting NUMA hinting information. Do not relock and
1283 * check_same as the page may no longer be mapped.
1285 if (unlikely(pmd_trans_migrating(*pmdp))) {
1286 page = pmd_page(*pmdp);
1288 wait_on_page_locked(page);
1292 page = pmd_page(pmd);
1293 BUG_ON(is_huge_zero_page(page));
1294 page_nid = page_to_nid(page);
1295 last_cpupid = page_cpupid_last(page);
1296 count_vm_numa_event(NUMA_HINT_FAULTS);
1297 if (page_nid == this_nid) {
1298 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1299 flags |= TNF_FAULT_LOCAL;
1302 /* See similar comment in do_numa_page for explanation */
1303 if (!(vma->vm_flags & VM_WRITE))
1304 flags |= TNF_NO_GROUP;
1307 * Acquire the page lock to serialise THP migrations but avoid dropping
1308 * page_table_lock if at all possible
1310 page_locked = trylock_page(page);
1311 target_nid = mpol_misplaced(page, vma, haddr);
1312 if (target_nid == -1) {
1313 /* If the page was locked, there are no parallel migrations */
1318 /* Migration could have started since the pmd_trans_migrating check */
1321 wait_on_page_locked(page);
1327 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1328 * to serialises splits
1332 anon_vma = page_lock_anon_vma_read(page);
1334 /* Confirm the PMD did not change while page_table_lock was released */
1336 if (unlikely(!pmd_same(pmd, *pmdp))) {
1343 /* Bail if we fail to protect against THP splits for any reason */
1344 if (unlikely(!anon_vma)) {
1351 * Migrate the THP to the requested node, returns with page unlocked
1352 * and access rights restored.
1355 migrated = migrate_misplaced_transhuge_page(mm, vma,
1356 pmdp, pmd, addr, page, target_nid);
1358 flags |= TNF_MIGRATED;
1359 page_nid = target_nid;
1361 flags |= TNF_MIGRATE_FAIL;
1365 BUG_ON(!PageLocked(page));
1366 was_writable = pmd_write(pmd);
1367 pmd = pmd_modify(pmd, vma->vm_page_prot);
1368 pmd = pmd_mkyoung(pmd);
1370 pmd = pmd_mkwrite(pmd);
1371 set_pmd_at(mm, haddr, pmdp, pmd);
1372 update_mmu_cache_pmd(vma, addr, pmdp);
1379 page_unlock_anon_vma_read(anon_vma);
1382 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1387 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1388 pmd_t *pmd, unsigned long addr)
1393 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1398 * For architectures like ppc64 we look at deposited pgtable
1399 * when calling pmdp_get_and_clear. So do the
1400 * pgtable_trans_huge_withdraw after finishing pmdp related
1403 orig_pmd = pmdp_get_and_clear_full(tlb->mm, addr, pmd,
1405 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1406 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1407 if (is_huge_zero_pmd(orig_pmd)) {
1408 atomic_long_dec(&tlb->mm->nr_ptes);
1410 put_huge_zero_page();
1412 page = pmd_page(orig_pmd);
1413 page_remove_rmap(page);
1414 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1415 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1416 VM_BUG_ON_PAGE(!PageHead(page), page);
1417 atomic_long_dec(&tlb->mm->nr_ptes);
1419 tlb_remove_page(tlb, page);
1421 pte_free(tlb->mm, pgtable);
1427 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1428 unsigned long old_addr,
1429 unsigned long new_addr, unsigned long old_end,
1430 pmd_t *old_pmd, pmd_t *new_pmd)
1432 spinlock_t *old_ptl, *new_ptl;
1436 struct mm_struct *mm = vma->vm_mm;
1438 if ((old_addr & ~HPAGE_PMD_MASK) ||
1439 (new_addr & ~HPAGE_PMD_MASK) ||
1440 old_end - old_addr < HPAGE_PMD_SIZE ||
1441 (new_vma->vm_flags & VM_NOHUGEPAGE))
1445 * The destination pmd shouldn't be established, free_pgtables()
1446 * should have release it.
1448 if (WARN_ON(!pmd_none(*new_pmd))) {
1449 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1454 * We don't have to worry about the ordering of src and dst
1455 * ptlocks because exclusive mmap_sem prevents deadlock.
1457 ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
1459 new_ptl = pmd_lockptr(mm, new_pmd);
1460 if (new_ptl != old_ptl)
1461 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1462 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1463 VM_BUG_ON(!pmd_none(*new_pmd));
1465 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1467 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1468 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1470 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1471 if (new_ptl != old_ptl)
1472 spin_unlock(new_ptl);
1473 spin_unlock(old_ptl);
1481 * - 0 if PMD could not be locked
1482 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1483 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1485 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1486 unsigned long addr, pgprot_t newprot, int prot_numa)
1488 struct mm_struct *mm = vma->vm_mm;
1492 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1494 bool preserve_write = prot_numa && pmd_write(*pmd);
1498 * Avoid trapping faults against the zero page. The read-only
1499 * data is likely to be read-cached on the local CPU and
1500 * local/remote hits to the zero page are not interesting.
1502 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1507 if (!prot_numa || !pmd_protnone(*pmd)) {
1508 entry = pmdp_get_and_clear_notify(mm, addr, pmd);
1509 entry = pmd_modify(entry, newprot);
1511 entry = pmd_mkwrite(entry);
1513 set_pmd_at(mm, addr, pmd, entry);
1514 BUG_ON(!preserve_write && pmd_write(entry));
1523 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1524 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1526 * Note that if it returns 1, this routine returns without unlocking page
1527 * table locks. So callers must unlock them.
1529 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1532 *ptl = pmd_lock(vma->vm_mm, pmd);
1533 if (likely(pmd_trans_huge(*pmd))) {
1534 if (unlikely(pmd_trans_splitting(*pmd))) {
1536 wait_split_huge_page(vma->anon_vma, pmd);
1539 /* Thp mapped by 'pmd' is stable, so we can
1540 * handle it as it is. */
1549 * This function returns whether a given @page is mapped onto the @address
1550 * in the virtual space of @mm.
1552 * When it's true, this function returns *pmd with holding the page table lock
1553 * and passing it back to the caller via @ptl.
1554 * If it's false, returns NULL without holding the page table lock.
1556 pmd_t *page_check_address_pmd(struct page *page,
1557 struct mm_struct *mm,
1558 unsigned long address,
1559 enum page_check_address_pmd_flag flag,
1566 if (address & ~HPAGE_PMD_MASK)
1569 pgd = pgd_offset(mm, address);
1570 if (!pgd_present(*pgd))
1572 pud = pud_offset(pgd, address);
1573 if (!pud_present(*pud))
1575 pmd = pmd_offset(pud, address);
1577 *ptl = pmd_lock(mm, pmd);
1578 if (!pmd_present(*pmd))
1580 if (pmd_page(*pmd) != page)
1583 * split_vma() may create temporary aliased mappings. There is
1584 * no risk as long as all huge pmd are found and have their
1585 * splitting bit set before __split_huge_page_refcount
1586 * runs. Finding the same huge pmd more than once during the
1587 * same rmap walk is not a problem.
1589 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1590 pmd_trans_splitting(*pmd))
1592 if (pmd_trans_huge(*pmd)) {
1593 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1594 !pmd_trans_splitting(*pmd));
1602 static int __split_huge_page_splitting(struct page *page,
1603 struct vm_area_struct *vma,
1604 unsigned long address)
1606 struct mm_struct *mm = vma->vm_mm;
1610 /* For mmu_notifiers */
1611 const unsigned long mmun_start = address;
1612 const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
1614 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1615 pmd = page_check_address_pmd(page, mm, address,
1616 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl);
1619 * We can't temporarily set the pmd to null in order
1620 * to split it, the pmd must remain marked huge at all
1621 * times or the VM won't take the pmd_trans_huge paths
1622 * and it won't wait on the anon_vma->root->rwsem to
1623 * serialize against split_huge_page*.
1625 pmdp_splitting_flush(vma, address, pmd);
1630 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1635 static void __split_huge_page_refcount(struct page *page,
1636 struct list_head *list)
1639 struct zone *zone = page_zone(page);
1640 struct lruvec *lruvec;
1643 /* prevent PageLRU to go away from under us, and freeze lru stats */
1644 spin_lock_irq(&zone->lru_lock);
1645 lruvec = mem_cgroup_page_lruvec(page, zone);
1647 compound_lock(page);
1648 /* complete memcg works before add pages to LRU */
1649 mem_cgroup_split_huge_fixup(page);
1651 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1652 struct page *page_tail = page + i;
1654 /* tail_page->_mapcount cannot change */
1655 BUG_ON(page_mapcount(page_tail) < 0);
1656 tail_count += page_mapcount(page_tail);
1657 /* check for overflow */
1658 BUG_ON(tail_count < 0);
1659 BUG_ON(atomic_read(&page_tail->_count) != 0);
1661 * tail_page->_count is zero and not changing from
1662 * under us. But get_page_unless_zero() may be running
1663 * from under us on the tail_page. If we used
1664 * atomic_set() below instead of atomic_add(), we
1665 * would then run atomic_set() concurrently with
1666 * get_page_unless_zero(), and atomic_set() is
1667 * implemented in C not using locked ops. spin_unlock
1668 * on x86 sometime uses locked ops because of PPro
1669 * errata 66, 92, so unless somebody can guarantee
1670 * atomic_set() here would be safe on all archs (and
1671 * not only on x86), it's safer to use atomic_add().
1673 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1674 &page_tail->_count);
1676 /* after clearing PageTail the gup refcount can be released */
1677 smp_mb__after_atomic();
1680 * retain hwpoison flag of the poisoned tail page:
1681 * fix for the unsuitable process killed on Guest Machine(KVM)
1682 * by the memory-failure.
1684 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1685 page_tail->flags |= (page->flags &
1686 ((1L << PG_referenced) |
1687 (1L << PG_swapbacked) |
1688 (1L << PG_mlocked) |
1689 (1L << PG_uptodate) |
1691 (1L << PG_unevictable)));
1692 page_tail->flags |= (1L << PG_dirty);
1694 /* clear PageTail before overwriting first_page */
1698 * __split_huge_page_splitting() already set the
1699 * splitting bit in all pmd that could map this
1700 * hugepage, that will ensure no CPU can alter the
1701 * mapcount on the head page. The mapcount is only
1702 * accounted in the head page and it has to be
1703 * transferred to all tail pages in the below code. So
1704 * for this code to be safe, the split the mapcount
1705 * can't change. But that doesn't mean userland can't
1706 * keep changing and reading the page contents while
1707 * we transfer the mapcount, so the pmd splitting
1708 * status is achieved setting a reserved bit in the
1709 * pmd, not by clearing the present bit.
1711 page_tail->_mapcount = page->_mapcount;
1713 BUG_ON(page_tail->mapping);
1714 page_tail->mapping = page->mapping;
1716 page_tail->index = page->index + i;
1717 page_cpupid_xchg_last(page_tail, page_cpupid_last(page));
1719 BUG_ON(!PageAnon(page_tail));
1720 BUG_ON(!PageUptodate(page_tail));
1721 BUG_ON(!PageDirty(page_tail));
1722 BUG_ON(!PageSwapBacked(page_tail));
1724 lru_add_page_tail(page, page_tail, lruvec, list);
1726 atomic_sub(tail_count, &page->_count);
1727 BUG_ON(atomic_read(&page->_count) <= 0);
1729 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1731 ClearPageCompound(page);
1732 compound_unlock(page);
1733 spin_unlock_irq(&zone->lru_lock);
1735 for (i = 1; i < HPAGE_PMD_NR; i++) {
1736 struct page *page_tail = page + i;
1737 BUG_ON(page_count(page_tail) <= 0);
1739 * Tail pages may be freed if there wasn't any mapping
1740 * like if add_to_swap() is running on a lru page that
1741 * had its mapping zapped. And freeing these pages
1742 * requires taking the lru_lock so we do the put_page
1743 * of the tail pages after the split is complete.
1745 put_page(page_tail);
1749 * Only the head page (now become a regular page) is required
1750 * to be pinned by the caller.
1752 BUG_ON(page_count(page) <= 0);
1755 static int __split_huge_page_map(struct page *page,
1756 struct vm_area_struct *vma,
1757 unsigned long address)
1759 struct mm_struct *mm = vma->vm_mm;
1764 unsigned long haddr;
1766 pmd = page_check_address_pmd(page, mm, address,
1767 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl);
1769 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1770 pmd_populate(mm, &_pmd, pgtable);
1771 if (pmd_write(*pmd))
1772 BUG_ON(page_mapcount(page) != 1);
1775 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1777 BUG_ON(PageCompound(page+i));
1779 * Note that NUMA hinting access restrictions are not
1780 * transferred to avoid any possibility of altering
1781 * permissions across VMAs.
1783 entry = mk_pte(page + i, vma->vm_page_prot);
1784 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1785 if (!pmd_write(*pmd))
1786 entry = pte_wrprotect(entry);
1787 if (!pmd_young(*pmd))
1788 entry = pte_mkold(entry);
1789 pte = pte_offset_map(&_pmd, haddr);
1790 BUG_ON(!pte_none(*pte));
1791 set_pte_at(mm, haddr, pte, entry);
1795 smp_wmb(); /* make pte visible before pmd */
1797 * Up to this point the pmd is present and huge and
1798 * userland has the whole access to the hugepage
1799 * during the split (which happens in place). If we
1800 * overwrite the pmd with the not-huge version
1801 * pointing to the pte here (which of course we could
1802 * if all CPUs were bug free), userland could trigger
1803 * a small page size TLB miss on the small sized TLB
1804 * while the hugepage TLB entry is still established
1805 * in the huge TLB. Some CPU doesn't like that. See
1806 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1807 * Erratum 383 on page 93. Intel should be safe but is
1808 * also warns that it's only safe if the permission
1809 * and cache attributes of the two entries loaded in
1810 * the two TLB is identical (which should be the case
1811 * here). But it is generally safer to never allow
1812 * small and huge TLB entries for the same virtual
1813 * address to be loaded simultaneously. So instead of
1814 * doing "pmd_populate(); flush_tlb_range();" we first
1815 * mark the current pmd notpresent (atomically because
1816 * here the pmd_trans_huge and pmd_trans_splitting
1817 * must remain set at all times on the pmd until the
1818 * split is complete for this pmd), then we flush the
1819 * SMP TLB and finally we write the non-huge version
1820 * of the pmd entry with pmd_populate.
1822 pmdp_invalidate(vma, address, pmd);
1823 pmd_populate(mm, pmd, pgtable);
1831 /* must be called with anon_vma->root->rwsem held */
1832 static void __split_huge_page(struct page *page,
1833 struct anon_vma *anon_vma,
1834 struct list_head *list)
1836 int mapcount, mapcount2;
1837 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1838 struct anon_vma_chain *avc;
1840 BUG_ON(!PageHead(page));
1841 BUG_ON(PageTail(page));
1844 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1845 struct vm_area_struct *vma = avc->vma;
1846 unsigned long addr = vma_address(page, vma);
1847 BUG_ON(is_vma_temporary_stack(vma));
1848 mapcount += __split_huge_page_splitting(page, vma, addr);
1851 * It is critical that new vmas are added to the tail of the
1852 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1853 * and establishes a child pmd before
1854 * __split_huge_page_splitting() freezes the parent pmd (so if
1855 * we fail to prevent copy_huge_pmd() from running until the
1856 * whole __split_huge_page() is complete), we will still see
1857 * the newly established pmd of the child later during the
1858 * walk, to be able to set it as pmd_trans_splitting too.
1860 if (mapcount != page_mapcount(page)) {
1861 pr_err("mapcount %d page_mapcount %d\n",
1862 mapcount, page_mapcount(page));
1866 __split_huge_page_refcount(page, list);
1869 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1870 struct vm_area_struct *vma = avc->vma;
1871 unsigned long addr = vma_address(page, vma);
1872 BUG_ON(is_vma_temporary_stack(vma));
1873 mapcount2 += __split_huge_page_map(page, vma, addr);
1875 if (mapcount != mapcount2) {
1876 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n",
1877 mapcount, mapcount2, page_mapcount(page));
1883 * Split a hugepage into normal pages. This doesn't change the position of head
1884 * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1885 * @list. Both head page and tail pages will inherit mapping, flags, and so on
1886 * from the hugepage.
1887 * Return 0 if the hugepage is split successfully otherwise return 1.
1889 int split_huge_page_to_list(struct page *page, struct list_head *list)
1891 struct anon_vma *anon_vma;
1894 BUG_ON(is_huge_zero_page(page));
1895 BUG_ON(!PageAnon(page));
1898 * The caller does not necessarily hold an mmap_sem that would prevent
1899 * the anon_vma disappearing so we first we take a reference to it
1900 * and then lock the anon_vma for write. This is similar to
1901 * page_lock_anon_vma_read except the write lock is taken to serialise
1902 * against parallel split or collapse operations.
1904 anon_vma = page_get_anon_vma(page);
1907 anon_vma_lock_write(anon_vma);
1910 if (!PageCompound(page))
1913 BUG_ON(!PageSwapBacked(page));
1914 __split_huge_page(page, anon_vma, list);
1915 count_vm_event(THP_SPLIT);
1917 BUG_ON(PageCompound(page));
1919 anon_vma_unlock_write(anon_vma);
1920 put_anon_vma(anon_vma);
1925 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1927 int hugepage_madvise(struct vm_area_struct *vma,
1928 unsigned long *vm_flags, int advice)
1934 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1935 * can't handle this properly after s390_enable_sie, so we simply
1936 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1938 if (mm_has_pgste(vma->vm_mm))
1942 * Be somewhat over-protective like KSM for now!
1944 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1946 *vm_flags &= ~VM_NOHUGEPAGE;
1947 *vm_flags |= VM_HUGEPAGE;
1949 * If the vma become good for khugepaged to scan,
1950 * register it here without waiting a page fault that
1951 * may not happen any time soon.
1953 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1956 case MADV_NOHUGEPAGE:
1958 * Be somewhat over-protective like KSM for now!
1960 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1962 *vm_flags &= ~VM_HUGEPAGE;
1963 *vm_flags |= VM_NOHUGEPAGE;
1965 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1966 * this vma even if we leave the mm registered in khugepaged if
1967 * it got registered before VM_NOHUGEPAGE was set.
1975 static int __init khugepaged_slab_init(void)
1977 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1978 sizeof(struct mm_slot),
1979 __alignof__(struct mm_slot), 0, NULL);
1986 static void __init khugepaged_slab_exit(void)
1988 kmem_cache_destroy(mm_slot_cache);
1991 static inline struct mm_slot *alloc_mm_slot(void)
1993 if (!mm_slot_cache) /* initialization failed */
1995 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1998 static inline void free_mm_slot(struct mm_slot *mm_slot)
2000 kmem_cache_free(mm_slot_cache, mm_slot);
2003 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
2005 struct mm_slot *mm_slot;
2007 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
2008 if (mm == mm_slot->mm)
2014 static void insert_to_mm_slots_hash(struct mm_struct *mm,
2015 struct mm_slot *mm_slot)
2018 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
2021 static inline int khugepaged_test_exit(struct mm_struct *mm)
2023 return atomic_read(&mm->mm_users) == 0;
2026 int __khugepaged_enter(struct mm_struct *mm)
2028 struct mm_slot *mm_slot;
2031 mm_slot = alloc_mm_slot();
2035 /* __khugepaged_exit() must not run from under us */
2036 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
2037 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
2038 free_mm_slot(mm_slot);
2042 spin_lock(&khugepaged_mm_lock);
2043 insert_to_mm_slots_hash(mm, mm_slot);
2045 * Insert just behind the scanning cursor, to let the area settle
2048 wakeup = list_empty(&khugepaged_scan.mm_head);
2049 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
2050 spin_unlock(&khugepaged_mm_lock);
2052 atomic_inc(&mm->mm_count);
2054 wake_up_interruptible(&khugepaged_wait);
2059 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
2060 unsigned long vm_flags)
2062 unsigned long hstart, hend;
2065 * Not yet faulted in so we will register later in the
2066 * page fault if needed.
2070 /* khugepaged not yet working on file or special mappings */
2072 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
2073 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2074 hend = vma->vm_end & HPAGE_PMD_MASK;
2076 return khugepaged_enter(vma, vm_flags);
2080 void __khugepaged_exit(struct mm_struct *mm)
2082 struct mm_slot *mm_slot;
2085 spin_lock(&khugepaged_mm_lock);
2086 mm_slot = get_mm_slot(mm);
2087 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2088 hash_del(&mm_slot->hash);
2089 list_del(&mm_slot->mm_node);
2092 spin_unlock(&khugepaged_mm_lock);
2095 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2096 free_mm_slot(mm_slot);
2098 } else if (mm_slot) {
2100 * This is required to serialize against
2101 * khugepaged_test_exit() (which is guaranteed to run
2102 * under mmap sem read mode). Stop here (after we
2103 * return all pagetables will be destroyed) until
2104 * khugepaged has finished working on the pagetables
2105 * under the mmap_sem.
2107 down_write(&mm->mmap_sem);
2108 up_write(&mm->mmap_sem);
2112 static void release_pte_page(struct page *page)
2114 /* 0 stands for page_is_file_cache(page) == false */
2115 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2117 putback_lru_page(page);
2120 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2122 while (--_pte >= pte) {
2123 pte_t pteval = *_pte;
2124 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2125 release_pte_page(pte_page(pteval));
2129 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2130 unsigned long address,
2135 int none_or_zero = 0;
2136 bool referenced = false, writable = false;
2137 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2138 _pte++, address += PAGE_SIZE) {
2139 pte_t pteval = *_pte;
2140 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2141 if (++none_or_zero <= khugepaged_max_ptes_none)
2146 if (!pte_present(pteval))
2148 page = vm_normal_page(vma, address, pteval);
2149 if (unlikely(!page))
2152 VM_BUG_ON_PAGE(PageCompound(page), page);
2153 VM_BUG_ON_PAGE(!PageAnon(page), page);
2154 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2157 * We can do it before isolate_lru_page because the
2158 * page can't be freed from under us. NOTE: PG_lock
2159 * is needed to serialize against split_huge_page
2160 * when invoked from the VM.
2162 if (!trylock_page(page))
2166 * cannot use mapcount: can't collapse if there's a gup pin.
2167 * The page must only be referenced by the scanned process
2168 * and page swap cache.
2170 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2174 if (pte_write(pteval)) {
2177 if (PageSwapCache(page) && !reuse_swap_page(page)) {
2182 * Page is not in the swap cache. It can be collapsed
2188 * Isolate the page to avoid collapsing an hugepage
2189 * currently in use by the VM.
2191 if (isolate_lru_page(page)) {
2195 /* 0 stands for page_is_file_cache(page) == false */
2196 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2197 VM_BUG_ON_PAGE(!PageLocked(page), page);
2198 VM_BUG_ON_PAGE(PageLRU(page), page);
2200 /* If there is no mapped pte young don't collapse the page */
2201 if (pte_young(pteval) || PageReferenced(page) ||
2202 mmu_notifier_test_young(vma->vm_mm, address))
2205 if (likely(referenced && writable))
2208 release_pte_pages(pte, _pte);
2212 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2213 struct vm_area_struct *vma,
2214 unsigned long address,
2218 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2219 pte_t pteval = *_pte;
2220 struct page *src_page;
2222 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2223 clear_user_highpage(page, address);
2224 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2225 if (is_zero_pfn(pte_pfn(pteval))) {
2227 * ptl mostly unnecessary.
2231 * paravirt calls inside pte_clear here are
2234 pte_clear(vma->vm_mm, address, _pte);
2238 src_page = pte_page(pteval);
2239 copy_user_highpage(page, src_page, address, vma);
2240 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2241 release_pte_page(src_page);
2243 * ptl mostly unnecessary, but preempt has to
2244 * be disabled to update the per-cpu stats
2245 * inside page_remove_rmap().
2249 * paravirt calls inside pte_clear here are
2252 pte_clear(vma->vm_mm, address, _pte);
2253 page_remove_rmap(src_page);
2255 free_page_and_swap_cache(src_page);
2258 address += PAGE_SIZE;
2263 static void khugepaged_alloc_sleep(void)
2265 wait_event_freezable_timeout(khugepaged_wait, false,
2266 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2269 static int khugepaged_node_load[MAX_NUMNODES];
2271 static bool khugepaged_scan_abort(int nid)
2276 * If zone_reclaim_mode is disabled, then no extra effort is made to
2277 * allocate memory locally.
2279 if (!zone_reclaim_mode)
2282 /* If there is a count for this node already, it must be acceptable */
2283 if (khugepaged_node_load[nid])
2286 for (i = 0; i < MAX_NUMNODES; i++) {
2287 if (!khugepaged_node_load[i])
2289 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2296 static int khugepaged_find_target_node(void)
2298 static int last_khugepaged_target_node = NUMA_NO_NODE;
2299 int nid, target_node = 0, max_value = 0;
2301 /* find first node with max normal pages hit */
2302 for (nid = 0; nid < MAX_NUMNODES; nid++)
2303 if (khugepaged_node_load[nid] > max_value) {
2304 max_value = khugepaged_node_load[nid];
2308 /* do some balance if several nodes have the same hit record */
2309 if (target_node <= last_khugepaged_target_node)
2310 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2312 if (max_value == khugepaged_node_load[nid]) {
2317 last_khugepaged_target_node = target_node;
2321 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2323 if (IS_ERR(*hpage)) {
2329 khugepaged_alloc_sleep();
2330 } else if (*hpage) {
2338 static struct page *
2339 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2340 struct vm_area_struct *vma, unsigned long address,
2343 VM_BUG_ON_PAGE(*hpage, *hpage);
2346 * Before allocating the hugepage, release the mmap_sem read lock.
2347 * The allocation can take potentially a long time if it involves
2348 * sync compaction, and we do not need to hold the mmap_sem during
2349 * that. We will recheck the vma after taking it again in write mode.
2351 up_read(&mm->mmap_sem);
2353 *hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER);
2354 if (unlikely(!*hpage)) {
2355 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2356 *hpage = ERR_PTR(-ENOMEM);
2360 count_vm_event(THP_COLLAPSE_ALLOC);
2364 static int khugepaged_find_target_node(void)
2369 static inline struct page *alloc_hugepage(int defrag)
2371 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
2375 static struct page *khugepaged_alloc_hugepage(bool *wait)
2380 hpage = alloc_hugepage(khugepaged_defrag());
2382 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2387 khugepaged_alloc_sleep();
2389 count_vm_event(THP_COLLAPSE_ALLOC);
2390 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2395 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2398 *hpage = khugepaged_alloc_hugepage(wait);
2400 if (unlikely(!*hpage))
2406 static struct page *
2407 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2408 struct vm_area_struct *vma, unsigned long address,
2411 up_read(&mm->mmap_sem);
2418 static bool hugepage_vma_check(struct vm_area_struct *vma)
2420 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2421 (vma->vm_flags & VM_NOHUGEPAGE))
2424 if (!vma->anon_vma || vma->vm_ops)
2426 if (is_vma_temporary_stack(vma))
2428 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2432 static void collapse_huge_page(struct mm_struct *mm,
2433 unsigned long address,
2434 struct page **hpage,
2435 struct vm_area_struct *vma,
2441 struct page *new_page;
2442 spinlock_t *pmd_ptl, *pte_ptl;
2444 unsigned long hstart, hend;
2445 struct mem_cgroup *memcg;
2446 unsigned long mmun_start; /* For mmu_notifiers */
2447 unsigned long mmun_end; /* For mmu_notifiers */
2450 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2452 /* Only allocate from the target node */
2453 gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2456 /* release the mmap_sem read lock. */
2457 new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node);
2461 if (unlikely(mem_cgroup_try_charge(new_page, mm,
2466 * Prevent all access to pagetables with the exception of
2467 * gup_fast later hanlded by the ptep_clear_flush and the VM
2468 * handled by the anon_vma lock + PG_lock.
2470 down_write(&mm->mmap_sem);
2471 if (unlikely(khugepaged_test_exit(mm)))
2474 vma = find_vma(mm, address);
2477 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2478 hend = vma->vm_end & HPAGE_PMD_MASK;
2479 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2481 if (!hugepage_vma_check(vma))
2483 pmd = mm_find_pmd(mm, address);
2487 anon_vma_lock_write(vma->anon_vma);
2489 pte = pte_offset_map(pmd, address);
2490 pte_ptl = pte_lockptr(mm, pmd);
2492 mmun_start = address;
2493 mmun_end = address + HPAGE_PMD_SIZE;
2494 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2495 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2497 * After this gup_fast can't run anymore. This also removes
2498 * any huge TLB entry from the CPU so we won't allow
2499 * huge and small TLB entries for the same virtual address
2500 * to avoid the risk of CPU bugs in that area.
2502 _pmd = pmdp_collapse_flush(vma, address, pmd);
2503 spin_unlock(pmd_ptl);
2504 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2507 isolated = __collapse_huge_page_isolate(vma, address, pte);
2508 spin_unlock(pte_ptl);
2510 if (unlikely(!isolated)) {
2513 BUG_ON(!pmd_none(*pmd));
2515 * We can only use set_pmd_at when establishing
2516 * hugepmds and never for establishing regular pmds that
2517 * points to regular pagetables. Use pmd_populate for that
2519 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2520 spin_unlock(pmd_ptl);
2521 anon_vma_unlock_write(vma->anon_vma);
2526 * All pages are isolated and locked so anon_vma rmap
2527 * can't run anymore.
2529 anon_vma_unlock_write(vma->anon_vma);
2531 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2533 __SetPageUptodate(new_page);
2534 pgtable = pmd_pgtable(_pmd);
2536 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2537 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2540 * spin_lock() below is not the equivalent of smp_wmb(), so
2541 * this is needed to avoid the copy_huge_page writes to become
2542 * visible after the set_pmd_at() write.
2547 BUG_ON(!pmd_none(*pmd));
2548 page_add_new_anon_rmap(new_page, vma, address);
2549 mem_cgroup_commit_charge(new_page, memcg, false);
2550 lru_cache_add_active_or_unevictable(new_page, vma);
2551 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2552 set_pmd_at(mm, address, pmd, _pmd);
2553 update_mmu_cache_pmd(vma, address, pmd);
2554 spin_unlock(pmd_ptl);
2558 khugepaged_pages_collapsed++;
2560 up_write(&mm->mmap_sem);
2564 mem_cgroup_cancel_charge(new_page, memcg);
2568 static int khugepaged_scan_pmd(struct mm_struct *mm,
2569 struct vm_area_struct *vma,
2570 unsigned long address,
2571 struct page **hpage)
2575 int ret = 0, none_or_zero = 0;
2577 unsigned long _address;
2579 int node = NUMA_NO_NODE;
2580 bool writable = false, referenced = false;
2582 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2584 pmd = mm_find_pmd(mm, address);
2588 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2589 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2590 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2591 _pte++, _address += PAGE_SIZE) {
2592 pte_t pteval = *_pte;
2593 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2594 if (++none_or_zero <= khugepaged_max_ptes_none)
2599 if (!pte_present(pteval))
2601 if (pte_write(pteval))
2604 page = vm_normal_page(vma, _address, pteval);
2605 if (unlikely(!page))
2608 * Record which node the original page is from and save this
2609 * information to khugepaged_node_load[].
2610 * Khupaged will allocate hugepage from the node has the max
2613 node = page_to_nid(page);
2614 if (khugepaged_scan_abort(node))
2616 khugepaged_node_load[node]++;
2617 VM_BUG_ON_PAGE(PageCompound(page), page);
2618 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2621 * cannot use mapcount: can't collapse if there's a gup pin.
2622 * The page must only be referenced by the scanned process
2623 * and page swap cache.
2625 if (page_count(page) != 1 + !!PageSwapCache(page))
2627 if (pte_young(pteval) || PageReferenced(page) ||
2628 mmu_notifier_test_young(vma->vm_mm, address))
2631 if (referenced && writable)
2634 pte_unmap_unlock(pte, ptl);
2636 node = khugepaged_find_target_node();
2637 /* collapse_huge_page will return with the mmap_sem released */
2638 collapse_huge_page(mm, address, hpage, vma, node);
2644 static void collect_mm_slot(struct mm_slot *mm_slot)
2646 struct mm_struct *mm = mm_slot->mm;
2648 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2650 if (khugepaged_test_exit(mm)) {
2652 hash_del(&mm_slot->hash);
2653 list_del(&mm_slot->mm_node);
2656 * Not strictly needed because the mm exited already.
2658 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2661 /* khugepaged_mm_lock actually not necessary for the below */
2662 free_mm_slot(mm_slot);
2667 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2668 struct page **hpage)
2669 __releases(&khugepaged_mm_lock)
2670 __acquires(&khugepaged_mm_lock)
2672 struct mm_slot *mm_slot;
2673 struct mm_struct *mm;
2674 struct vm_area_struct *vma;
2678 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2680 if (khugepaged_scan.mm_slot)
2681 mm_slot = khugepaged_scan.mm_slot;
2683 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2684 struct mm_slot, mm_node);
2685 khugepaged_scan.address = 0;
2686 khugepaged_scan.mm_slot = mm_slot;
2688 spin_unlock(&khugepaged_mm_lock);
2691 down_read(&mm->mmap_sem);
2692 if (unlikely(khugepaged_test_exit(mm)))
2695 vma = find_vma(mm, khugepaged_scan.address);
2698 for (; vma; vma = vma->vm_next) {
2699 unsigned long hstart, hend;
2702 if (unlikely(khugepaged_test_exit(mm))) {
2706 if (!hugepage_vma_check(vma)) {
2711 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2712 hend = vma->vm_end & HPAGE_PMD_MASK;
2715 if (khugepaged_scan.address > hend)
2717 if (khugepaged_scan.address < hstart)
2718 khugepaged_scan.address = hstart;
2719 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2721 while (khugepaged_scan.address < hend) {
2724 if (unlikely(khugepaged_test_exit(mm)))
2725 goto breakouterloop;
2727 VM_BUG_ON(khugepaged_scan.address < hstart ||
2728 khugepaged_scan.address + HPAGE_PMD_SIZE >
2730 ret = khugepaged_scan_pmd(mm, vma,
2731 khugepaged_scan.address,
2733 /* move to next address */
2734 khugepaged_scan.address += HPAGE_PMD_SIZE;
2735 progress += HPAGE_PMD_NR;
2737 /* we released mmap_sem so break loop */
2738 goto breakouterloop_mmap_sem;
2739 if (progress >= pages)
2740 goto breakouterloop;
2744 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2745 breakouterloop_mmap_sem:
2747 spin_lock(&khugepaged_mm_lock);
2748 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2750 * Release the current mm_slot if this mm is about to die, or
2751 * if we scanned all vmas of this mm.
2753 if (khugepaged_test_exit(mm) || !vma) {
2755 * Make sure that if mm_users is reaching zero while
2756 * khugepaged runs here, khugepaged_exit will find
2757 * mm_slot not pointing to the exiting mm.
2759 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2760 khugepaged_scan.mm_slot = list_entry(
2761 mm_slot->mm_node.next,
2762 struct mm_slot, mm_node);
2763 khugepaged_scan.address = 0;
2765 khugepaged_scan.mm_slot = NULL;
2766 khugepaged_full_scans++;
2769 collect_mm_slot(mm_slot);
2775 static int khugepaged_has_work(void)
2777 return !list_empty(&khugepaged_scan.mm_head) &&
2778 khugepaged_enabled();
2781 static int khugepaged_wait_event(void)
2783 return !list_empty(&khugepaged_scan.mm_head) ||
2784 kthread_should_stop();
2787 static void khugepaged_do_scan(void)
2789 struct page *hpage = NULL;
2790 unsigned int progress = 0, pass_through_head = 0;
2791 unsigned int pages = khugepaged_pages_to_scan;
2794 barrier(); /* write khugepaged_pages_to_scan to local stack */
2796 while (progress < pages) {
2797 if (!khugepaged_prealloc_page(&hpage, &wait))
2802 if (unlikely(kthread_should_stop() || try_to_freeze()))
2805 spin_lock(&khugepaged_mm_lock);
2806 if (!khugepaged_scan.mm_slot)
2807 pass_through_head++;
2808 if (khugepaged_has_work() &&
2809 pass_through_head < 2)
2810 progress += khugepaged_scan_mm_slot(pages - progress,
2814 spin_unlock(&khugepaged_mm_lock);
2817 if (!IS_ERR_OR_NULL(hpage))
2821 static void khugepaged_wait_work(void)
2823 if (khugepaged_has_work()) {
2824 if (!khugepaged_scan_sleep_millisecs)
2827 wait_event_freezable_timeout(khugepaged_wait,
2828 kthread_should_stop(),
2829 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2833 if (khugepaged_enabled())
2834 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2837 static int khugepaged(void *none)
2839 struct mm_slot *mm_slot;
2842 set_user_nice(current, MAX_NICE);
2844 while (!kthread_should_stop()) {
2845 khugepaged_do_scan();
2846 khugepaged_wait_work();
2849 spin_lock(&khugepaged_mm_lock);
2850 mm_slot = khugepaged_scan.mm_slot;
2851 khugepaged_scan.mm_slot = NULL;
2853 collect_mm_slot(mm_slot);
2854 spin_unlock(&khugepaged_mm_lock);
2858 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2859 unsigned long haddr, pmd_t *pmd)
2861 struct mm_struct *mm = vma->vm_mm;
2866 pmdp_clear_flush_notify(vma, haddr, pmd);
2867 /* leave pmd empty until pte is filled */
2869 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2870 pmd_populate(mm, &_pmd, pgtable);
2872 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2874 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2875 entry = pte_mkspecial(entry);
2876 pte = pte_offset_map(&_pmd, haddr);
2877 VM_BUG_ON(!pte_none(*pte));
2878 set_pte_at(mm, haddr, pte, entry);
2881 smp_wmb(); /* make pte visible before pmd */
2882 pmd_populate(mm, pmd, pgtable);
2883 put_huge_zero_page();
2886 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2891 struct mm_struct *mm = vma->vm_mm;
2892 unsigned long haddr = address & HPAGE_PMD_MASK;
2893 unsigned long mmun_start; /* For mmu_notifiers */
2894 unsigned long mmun_end; /* For mmu_notifiers */
2896 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2899 mmun_end = haddr + HPAGE_PMD_SIZE;
2901 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2902 ptl = pmd_lock(mm, pmd);
2903 if (unlikely(!pmd_trans_huge(*pmd))) {
2905 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2908 if (is_huge_zero_pmd(*pmd)) {
2909 __split_huge_zero_page_pmd(vma, haddr, pmd);
2911 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2914 page = pmd_page(*pmd);
2915 VM_BUG_ON_PAGE(!page_count(page), page);
2918 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2920 split_huge_page(page);
2925 * We don't always have down_write of mmap_sem here: a racing
2926 * do_huge_pmd_wp_page() might have copied-on-write to another
2927 * huge page before our split_huge_page() got the anon_vma lock.
2929 if (unlikely(pmd_trans_huge(*pmd)))
2933 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2936 struct vm_area_struct *vma;
2938 vma = find_vma(mm, address);
2939 BUG_ON(vma == NULL);
2940 split_huge_page_pmd(vma, address, pmd);
2943 static void split_huge_page_address(struct mm_struct *mm,
2944 unsigned long address)
2950 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2952 pgd = pgd_offset(mm, address);
2953 if (!pgd_present(*pgd))
2956 pud = pud_offset(pgd, address);
2957 if (!pud_present(*pud))
2960 pmd = pmd_offset(pud, address);
2961 if (!pmd_present(*pmd))
2964 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2965 * materialize from under us.
2967 split_huge_page_pmd_mm(mm, address, pmd);
2970 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2971 unsigned long start,
2976 * If the new start address isn't hpage aligned and it could
2977 * previously contain an hugepage: check if we need to split
2980 if (start & ~HPAGE_PMD_MASK &&
2981 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2982 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2983 split_huge_page_address(vma->vm_mm, start);
2986 * If the new end address isn't hpage aligned and it could
2987 * previously contain an hugepage: check if we need to split
2990 if (end & ~HPAGE_PMD_MASK &&
2991 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2992 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2993 split_huge_page_address(vma->vm_mm, end);
2996 * If we're also updating the vma->vm_next->vm_start, if the new
2997 * vm_next->vm_start isn't page aligned and it could previously
2998 * contain an hugepage: check if we need to split an huge pmd.
3000 if (adjust_next > 0) {
3001 struct vm_area_struct *next = vma->vm_next;
3002 unsigned long nstart = next->vm_start;
3003 nstart += adjust_next << PAGE_SHIFT;
3004 if (nstart & ~HPAGE_PMD_MASK &&
3005 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3006 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3007 split_huge_page_address(next->vm_mm, nstart);