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.
9 #include <linux/sched.h>
10 #include <linux/highmem.h>
11 #include <linux/hugetlb.h>
12 #include <linux/mmu_notifier.h>
13 #include <linux/rmap.h>
14 #include <linux/swap.h>
15 #include <linux/shrinker.h>
16 #include <linux/mm_inline.h>
17 #include <linux/kthread.h>
18 #include <linux/khugepaged.h>
19 #include <linux/freezer.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/migrate.h>
23 #include <linux/hashtable.h>
26 #include <asm/pgalloc.h>
30 * By default transparent hugepage support is enabled for all mappings
31 * and khugepaged scans all mappings. Defrag is only invoked by
32 * khugepaged hugepage allocations and by page faults inside
33 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
36 unsigned long transparent_hugepage_flags __read_mostly =
37 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
38 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
40 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
41 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
43 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
44 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
45 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
47 /* default scan 8*512 pte (or vmas) every 30 second */
48 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
49 static unsigned int khugepaged_pages_collapsed;
50 static unsigned int khugepaged_full_scans;
51 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
52 /* during fragmentation poll the hugepage allocator once every minute */
53 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
54 static struct task_struct *khugepaged_thread __read_mostly;
55 static DEFINE_MUTEX(khugepaged_mutex);
56 static DEFINE_SPINLOCK(khugepaged_mm_lock);
57 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
59 * default collapse hugepages if there is at least one pte mapped like
60 * it would have happened if the vma was large enough during page
63 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
65 static int khugepaged(void *none);
66 static int khugepaged_slab_init(void);
68 #define MM_SLOTS_HASH_BITS 10
69 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
71 static struct kmem_cache *mm_slot_cache __read_mostly;
74 * struct mm_slot - hash lookup from mm to mm_slot
75 * @hash: hash collision list
76 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
77 * @mm: the mm that this information is valid for
80 struct hlist_node hash;
81 struct list_head mm_node;
86 * struct khugepaged_scan - cursor for scanning
87 * @mm_head: the head of the mm list to scan
88 * @mm_slot: the current mm_slot we are scanning
89 * @address: the next address inside that to be scanned
91 * There is only the one khugepaged_scan instance of this cursor structure.
93 struct khugepaged_scan {
94 struct list_head mm_head;
95 struct mm_slot *mm_slot;
96 unsigned long address;
98 static struct khugepaged_scan khugepaged_scan = {
99 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
103 static int set_recommended_min_free_kbytes(void)
107 unsigned long recommended_min;
109 if (!khugepaged_enabled())
112 for_each_populated_zone(zone)
115 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
116 recommended_min = pageblock_nr_pages * nr_zones * 2;
119 * Make sure that on average at least two pageblocks are almost free
120 * of another type, one for a migratetype to fall back to and a
121 * second to avoid subsequent fallbacks of other types There are 3
122 * MIGRATE_TYPES we care about.
124 recommended_min += pageblock_nr_pages * nr_zones *
125 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
127 /* don't ever allow to reserve more than 5% of the lowmem */
128 recommended_min = min(recommended_min,
129 (unsigned long) nr_free_buffer_pages() / 20);
130 recommended_min <<= (PAGE_SHIFT-10);
132 if (recommended_min > min_free_kbytes)
133 min_free_kbytes = recommended_min;
134 setup_per_zone_wmarks();
137 late_initcall(set_recommended_min_free_kbytes);
139 static int start_khugepaged(void)
142 if (khugepaged_enabled()) {
143 if (!khugepaged_thread)
144 khugepaged_thread = kthread_run(khugepaged, NULL,
146 if (unlikely(IS_ERR(khugepaged_thread))) {
148 "khugepaged: kthread_run(khugepaged) failed\n");
149 err = PTR_ERR(khugepaged_thread);
150 khugepaged_thread = NULL;
153 if (!list_empty(&khugepaged_scan.mm_head))
154 wake_up_interruptible(&khugepaged_wait);
156 set_recommended_min_free_kbytes();
157 } else if (khugepaged_thread) {
158 kthread_stop(khugepaged_thread);
159 khugepaged_thread = NULL;
165 static atomic_t huge_zero_refcount;
166 static struct page *huge_zero_page __read_mostly;
168 static inline bool is_huge_zero_page(struct page *page)
170 return ACCESS_ONCE(huge_zero_page) == page;
173 static inline bool is_huge_zero_pmd(pmd_t pmd)
175 return is_huge_zero_page(pmd_page(pmd));
178 static struct page *get_huge_zero_page(void)
180 struct page *zero_page;
182 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
183 return ACCESS_ONCE(huge_zero_page);
185 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
188 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
191 count_vm_event(THP_ZERO_PAGE_ALLOC);
193 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
195 __free_page(zero_page);
199 /* We take additional reference here. It will be put back by shrinker */
200 atomic_set(&huge_zero_refcount, 2);
202 return ACCESS_ONCE(huge_zero_page);
205 static void put_huge_zero_page(void)
208 * Counter should never go to zero here. Only shrinker can put
211 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
214 static int shrink_huge_zero_page(struct shrinker *shrink,
215 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;
221 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
222 struct page *zero_page = xchg(&huge_zero_page, NULL);
223 BUG_ON(zero_page == NULL);
224 __free_page(zero_page);
230 static struct shrinker huge_zero_page_shrinker = {
231 .shrink = shrink_huge_zero_page,
232 .seeks = DEFAULT_SEEKS,
237 static ssize_t double_flag_show(struct kobject *kobj,
238 struct kobj_attribute *attr, char *buf,
239 enum transparent_hugepage_flag enabled,
240 enum transparent_hugepage_flag req_madv)
242 if (test_bit(enabled, &transparent_hugepage_flags)) {
243 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
244 return sprintf(buf, "[always] madvise never\n");
245 } else if (test_bit(req_madv, &transparent_hugepage_flags))
246 return sprintf(buf, "always [madvise] never\n");
248 return sprintf(buf, "always madvise [never]\n");
250 static ssize_t double_flag_store(struct kobject *kobj,
251 struct kobj_attribute *attr,
252 const char *buf, size_t count,
253 enum transparent_hugepage_flag enabled,
254 enum transparent_hugepage_flag req_madv)
256 if (!memcmp("always", buf,
257 min(sizeof("always")-1, count))) {
258 set_bit(enabled, &transparent_hugepage_flags);
259 clear_bit(req_madv, &transparent_hugepage_flags);
260 } else if (!memcmp("madvise", buf,
261 min(sizeof("madvise")-1, count))) {
262 clear_bit(enabled, &transparent_hugepage_flags);
263 set_bit(req_madv, &transparent_hugepage_flags);
264 } else if (!memcmp("never", buf,
265 min(sizeof("never")-1, count))) {
266 clear_bit(enabled, &transparent_hugepage_flags);
267 clear_bit(req_madv, &transparent_hugepage_flags);
274 static ssize_t enabled_show(struct kobject *kobj,
275 struct kobj_attribute *attr, char *buf)
277 return double_flag_show(kobj, attr, buf,
278 TRANSPARENT_HUGEPAGE_FLAG,
279 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
281 static ssize_t enabled_store(struct kobject *kobj,
282 struct kobj_attribute *attr,
283 const char *buf, size_t count)
287 ret = double_flag_store(kobj, attr, buf, count,
288 TRANSPARENT_HUGEPAGE_FLAG,
289 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
294 mutex_lock(&khugepaged_mutex);
295 err = start_khugepaged();
296 mutex_unlock(&khugepaged_mutex);
304 static struct kobj_attribute enabled_attr =
305 __ATTR(enabled, 0644, enabled_show, enabled_store);
307 static ssize_t single_flag_show(struct kobject *kobj,
308 struct kobj_attribute *attr, char *buf,
309 enum transparent_hugepage_flag flag)
311 return sprintf(buf, "%d\n",
312 !!test_bit(flag, &transparent_hugepage_flags));
315 static ssize_t single_flag_store(struct kobject *kobj,
316 struct kobj_attribute *attr,
317 const char *buf, size_t count,
318 enum transparent_hugepage_flag flag)
323 ret = kstrtoul(buf, 10, &value);
330 set_bit(flag, &transparent_hugepage_flags);
332 clear_bit(flag, &transparent_hugepage_flags);
338 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
339 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
340 * memory just to allocate one more hugepage.
342 static ssize_t defrag_show(struct kobject *kobj,
343 struct kobj_attribute *attr, char *buf)
345 return double_flag_show(kobj, attr, buf,
346 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
347 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
349 static ssize_t defrag_store(struct kobject *kobj,
350 struct kobj_attribute *attr,
351 const char *buf, size_t count)
353 return double_flag_store(kobj, attr, buf, count,
354 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
355 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
357 static struct kobj_attribute defrag_attr =
358 __ATTR(defrag, 0644, defrag_show, defrag_store);
360 static ssize_t use_zero_page_show(struct kobject *kobj,
361 struct kobj_attribute *attr, char *buf)
363 return single_flag_show(kobj, attr, buf,
364 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
366 static ssize_t use_zero_page_store(struct kobject *kobj,
367 struct kobj_attribute *attr, const char *buf, size_t count)
369 return single_flag_store(kobj, attr, buf, count,
370 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
372 static struct kobj_attribute use_zero_page_attr =
373 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
374 #ifdef CONFIG_DEBUG_VM
375 static ssize_t debug_cow_show(struct kobject *kobj,
376 struct kobj_attribute *attr, char *buf)
378 return single_flag_show(kobj, attr, buf,
379 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
381 static ssize_t debug_cow_store(struct kobject *kobj,
382 struct kobj_attribute *attr,
383 const char *buf, size_t count)
385 return single_flag_store(kobj, attr, buf, count,
386 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
388 static struct kobj_attribute debug_cow_attr =
389 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
390 #endif /* CONFIG_DEBUG_VM */
392 static struct attribute *hugepage_attr[] = {
395 &use_zero_page_attr.attr,
396 #ifdef CONFIG_DEBUG_VM
397 &debug_cow_attr.attr,
402 static struct attribute_group hugepage_attr_group = {
403 .attrs = hugepage_attr,
406 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
407 struct kobj_attribute *attr,
410 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
413 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
414 struct kobj_attribute *attr,
415 const char *buf, size_t count)
420 err = kstrtoul(buf, 10, &msecs);
421 if (err || msecs > UINT_MAX)
424 khugepaged_scan_sleep_millisecs = msecs;
425 wake_up_interruptible(&khugepaged_wait);
429 static struct kobj_attribute scan_sleep_millisecs_attr =
430 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
431 scan_sleep_millisecs_store);
433 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
434 struct kobj_attribute *attr,
437 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
440 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
441 struct kobj_attribute *attr,
442 const char *buf, size_t count)
447 err = kstrtoul(buf, 10, &msecs);
448 if (err || msecs > UINT_MAX)
451 khugepaged_alloc_sleep_millisecs = msecs;
452 wake_up_interruptible(&khugepaged_wait);
456 static struct kobj_attribute alloc_sleep_millisecs_attr =
457 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
458 alloc_sleep_millisecs_store);
460 static ssize_t pages_to_scan_show(struct kobject *kobj,
461 struct kobj_attribute *attr,
464 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
466 static ssize_t pages_to_scan_store(struct kobject *kobj,
467 struct kobj_attribute *attr,
468 const char *buf, size_t count)
473 err = kstrtoul(buf, 10, &pages);
474 if (err || !pages || pages > UINT_MAX)
477 khugepaged_pages_to_scan = pages;
481 static struct kobj_attribute pages_to_scan_attr =
482 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
483 pages_to_scan_store);
485 static ssize_t pages_collapsed_show(struct kobject *kobj,
486 struct kobj_attribute *attr,
489 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
491 static struct kobj_attribute pages_collapsed_attr =
492 __ATTR_RO(pages_collapsed);
494 static ssize_t full_scans_show(struct kobject *kobj,
495 struct kobj_attribute *attr,
498 return sprintf(buf, "%u\n", khugepaged_full_scans);
500 static struct kobj_attribute full_scans_attr =
501 __ATTR_RO(full_scans);
503 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
504 struct kobj_attribute *attr, char *buf)
506 return single_flag_show(kobj, attr, buf,
507 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
509 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
510 struct kobj_attribute *attr,
511 const char *buf, size_t count)
513 return single_flag_store(kobj, attr, buf, count,
514 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
516 static struct kobj_attribute khugepaged_defrag_attr =
517 __ATTR(defrag, 0644, khugepaged_defrag_show,
518 khugepaged_defrag_store);
521 * max_ptes_none controls if khugepaged should collapse hugepages over
522 * any unmapped ptes in turn potentially increasing the memory
523 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
524 * reduce the available free memory in the system as it
525 * runs. Increasing max_ptes_none will instead potentially reduce the
526 * free memory in the system during the khugepaged scan.
528 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
529 struct kobj_attribute *attr,
532 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
534 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
535 struct kobj_attribute *attr,
536 const char *buf, size_t count)
539 unsigned long max_ptes_none;
541 err = kstrtoul(buf, 10, &max_ptes_none);
542 if (err || max_ptes_none > HPAGE_PMD_NR-1)
545 khugepaged_max_ptes_none = max_ptes_none;
549 static struct kobj_attribute khugepaged_max_ptes_none_attr =
550 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
551 khugepaged_max_ptes_none_store);
553 static struct attribute *khugepaged_attr[] = {
554 &khugepaged_defrag_attr.attr,
555 &khugepaged_max_ptes_none_attr.attr,
556 &pages_to_scan_attr.attr,
557 &pages_collapsed_attr.attr,
558 &full_scans_attr.attr,
559 &scan_sleep_millisecs_attr.attr,
560 &alloc_sleep_millisecs_attr.attr,
564 static struct attribute_group khugepaged_attr_group = {
565 .attrs = khugepaged_attr,
566 .name = "khugepaged",
569 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
573 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
574 if (unlikely(!*hugepage_kobj)) {
575 printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n");
579 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
581 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
585 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
587 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
588 goto remove_hp_group;
594 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
596 kobject_put(*hugepage_kobj);
600 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
602 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
603 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
604 kobject_put(hugepage_kobj);
607 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
612 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
615 #endif /* CONFIG_SYSFS */
617 static int __init hugepage_init(void)
620 struct kobject *hugepage_kobj;
622 if (!has_transparent_hugepage()) {
623 transparent_hugepage_flags = 0;
627 err = hugepage_init_sysfs(&hugepage_kobj);
631 err = khugepaged_slab_init();
635 register_shrinker(&huge_zero_page_shrinker);
638 * By default disable transparent hugepages on smaller systems,
639 * where the extra memory used could hurt more than TLB overhead
640 * is likely to save. The admin can still enable it through /sys.
642 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
643 transparent_hugepage_flags = 0;
649 hugepage_exit_sysfs(hugepage_kobj);
652 module_init(hugepage_init)
654 static int __init setup_transparent_hugepage(char *str)
659 if (!strcmp(str, "always")) {
660 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
661 &transparent_hugepage_flags);
662 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
663 &transparent_hugepage_flags);
665 } else if (!strcmp(str, "madvise")) {
666 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
667 &transparent_hugepage_flags);
668 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
669 &transparent_hugepage_flags);
671 } else if (!strcmp(str, "never")) {
672 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
673 &transparent_hugepage_flags);
674 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
675 &transparent_hugepage_flags);
681 "transparent_hugepage= cannot parse, ignored\n");
684 __setup("transparent_hugepage=", setup_transparent_hugepage);
686 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
688 if (likely(vma->vm_flags & VM_WRITE))
689 pmd = pmd_mkwrite(pmd);
693 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
696 entry = mk_pmd(page, prot);
697 entry = pmd_mkhuge(entry);
701 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
702 struct vm_area_struct *vma,
703 unsigned long haddr, pmd_t *pmd,
708 VM_BUG_ON(!PageCompound(page));
709 pgtable = pte_alloc_one(mm, haddr);
710 if (unlikely(!pgtable))
713 clear_huge_page(page, haddr, HPAGE_PMD_NR);
715 * The memory barrier inside __SetPageUptodate makes sure that
716 * clear_huge_page writes become visible before the set_pmd_at()
719 __SetPageUptodate(page);
721 spin_lock(&mm->page_table_lock);
722 if (unlikely(!pmd_none(*pmd))) {
723 spin_unlock(&mm->page_table_lock);
724 mem_cgroup_uncharge_page(page);
726 pte_free(mm, pgtable);
729 entry = mk_huge_pmd(page, vma->vm_page_prot);
730 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
731 page_add_new_anon_rmap(page, vma, haddr);
732 pgtable_trans_huge_deposit(mm, pmd, pgtable);
733 set_pmd_at(mm, haddr, pmd, entry);
734 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
736 spin_unlock(&mm->page_table_lock);
742 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
744 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
747 static inline struct page *alloc_hugepage_vma(int defrag,
748 struct vm_area_struct *vma,
749 unsigned long haddr, int nd,
752 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
753 HPAGE_PMD_ORDER, vma, haddr, nd);
757 static inline struct page *alloc_hugepage(int defrag)
759 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
764 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
765 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
766 struct page *zero_page)
771 entry = mk_pmd(zero_page, vma->vm_page_prot);
772 entry = pmd_wrprotect(entry);
773 entry = pmd_mkhuge(entry);
774 pgtable_trans_huge_deposit(mm, pmd, pgtable);
775 set_pmd_at(mm, haddr, pmd, entry);
780 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
781 unsigned long address, pmd_t *pmd,
785 unsigned long haddr = address & HPAGE_PMD_MASK;
787 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
788 return VM_FAULT_FALLBACK;
789 if (unlikely(anon_vma_prepare(vma)))
791 if (unlikely(khugepaged_enter(vma)))
793 if (!(flags & FAULT_FLAG_WRITE) &&
794 transparent_hugepage_use_zero_page()) {
796 struct page *zero_page;
798 pgtable = pte_alloc_one(mm, haddr);
799 if (unlikely(!pgtable))
801 zero_page = get_huge_zero_page();
802 if (unlikely(!zero_page)) {
803 pte_free(mm, pgtable);
804 count_vm_event(THP_FAULT_FALLBACK);
805 return VM_FAULT_FALLBACK;
807 spin_lock(&mm->page_table_lock);
808 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
810 spin_unlock(&mm->page_table_lock);
812 pte_free(mm, pgtable);
813 put_huge_zero_page();
817 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
818 vma, haddr, numa_node_id(), 0);
819 if (unlikely(!page)) {
820 count_vm_event(THP_FAULT_FALLBACK);
821 return VM_FAULT_FALLBACK;
823 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
825 count_vm_event(THP_FAULT_FALLBACK);
826 return VM_FAULT_FALLBACK;
828 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) {
829 mem_cgroup_uncharge_page(page);
831 count_vm_event(THP_FAULT_FALLBACK);
832 return VM_FAULT_FALLBACK;
835 count_vm_event(THP_FAULT_ALLOC);
839 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
840 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
841 struct vm_area_struct *vma)
843 struct page *src_page;
849 pgtable = pte_alloc_one(dst_mm, addr);
850 if (unlikely(!pgtable))
853 spin_lock(&dst_mm->page_table_lock);
854 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
858 if (unlikely(!pmd_trans_huge(pmd))) {
859 pte_free(dst_mm, pgtable);
863 * mm->page_table_lock is enough to be sure that huge zero pmd is not
864 * under splitting since we don't split the page itself, only pmd to
867 if (is_huge_zero_pmd(pmd)) {
868 struct page *zero_page;
871 * get_huge_zero_page() will never allocate a new page here,
872 * since we already have a zero page to copy. It just takes a
875 zero_page = get_huge_zero_page();
876 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
878 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
882 if (unlikely(pmd_trans_splitting(pmd))) {
883 /* split huge page running from under us */
884 spin_unlock(&src_mm->page_table_lock);
885 spin_unlock(&dst_mm->page_table_lock);
886 pte_free(dst_mm, pgtable);
888 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
891 src_page = pmd_page(pmd);
892 VM_BUG_ON(!PageHead(src_page));
894 page_dup_rmap(src_page);
895 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
897 pmdp_set_wrprotect(src_mm, addr, src_pmd);
898 pmd = pmd_mkold(pmd_wrprotect(pmd));
899 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
900 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
905 spin_unlock(&src_mm->page_table_lock);
906 spin_unlock(&dst_mm->page_table_lock);
911 void huge_pmd_set_accessed(struct mm_struct *mm,
912 struct vm_area_struct *vma,
913 unsigned long address,
914 pmd_t *pmd, pmd_t orig_pmd,
920 spin_lock(&mm->page_table_lock);
921 if (unlikely(!pmd_same(*pmd, orig_pmd)))
924 entry = pmd_mkyoung(orig_pmd);
925 haddr = address & HPAGE_PMD_MASK;
926 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
927 update_mmu_cache_pmd(vma, address, pmd);
930 spin_unlock(&mm->page_table_lock);
933 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
934 struct vm_area_struct *vma, unsigned long address,
935 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
941 unsigned long mmun_start; /* For mmu_notifiers */
942 unsigned long mmun_end; /* For mmu_notifiers */
944 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
950 if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
956 clear_user_highpage(page, address);
957 __SetPageUptodate(page);
960 mmun_end = haddr + HPAGE_PMD_SIZE;
961 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
963 spin_lock(&mm->page_table_lock);
964 if (unlikely(!pmd_same(*pmd, orig_pmd)))
967 pmdp_clear_flush(vma, haddr, pmd);
968 /* leave pmd empty until pte is filled */
970 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
971 pmd_populate(mm, &_pmd, pgtable);
973 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
975 if (haddr == (address & PAGE_MASK)) {
976 entry = mk_pte(page, vma->vm_page_prot);
977 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
978 page_add_new_anon_rmap(page, vma, haddr);
980 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
981 entry = pte_mkspecial(entry);
983 pte = pte_offset_map(&_pmd, haddr);
984 VM_BUG_ON(!pte_none(*pte));
985 set_pte_at(mm, haddr, pte, entry);
988 smp_wmb(); /* make pte visible before pmd */
989 pmd_populate(mm, pmd, pgtable);
990 spin_unlock(&mm->page_table_lock);
991 put_huge_zero_page();
992 inc_mm_counter(mm, MM_ANONPAGES);
994 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
996 ret |= VM_FAULT_WRITE;
1000 spin_unlock(&mm->page_table_lock);
1001 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1002 mem_cgroup_uncharge_page(page);
1007 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1008 struct vm_area_struct *vma,
1009 unsigned long address,
1010 pmd_t *pmd, pmd_t orig_pmd,
1012 unsigned long haddr)
1017 struct page **pages;
1018 unsigned long mmun_start; /* For mmu_notifiers */
1019 unsigned long mmun_end; /* For mmu_notifiers */
1021 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1023 if (unlikely(!pages)) {
1024 ret |= VM_FAULT_OOM;
1028 for (i = 0; i < HPAGE_PMD_NR; i++) {
1029 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1031 vma, address, page_to_nid(page));
1032 if (unlikely(!pages[i] ||
1033 mem_cgroup_newpage_charge(pages[i], mm,
1037 mem_cgroup_uncharge_start();
1039 mem_cgroup_uncharge_page(pages[i]);
1042 mem_cgroup_uncharge_end();
1044 ret |= VM_FAULT_OOM;
1049 for (i = 0; i < HPAGE_PMD_NR; i++) {
1050 copy_user_highpage(pages[i], page + i,
1051 haddr + PAGE_SIZE * i, vma);
1052 __SetPageUptodate(pages[i]);
1057 mmun_end = haddr + HPAGE_PMD_SIZE;
1058 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1060 spin_lock(&mm->page_table_lock);
1061 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1062 goto out_free_pages;
1063 VM_BUG_ON(!PageHead(page));
1065 pmdp_clear_flush(vma, haddr, pmd);
1066 /* leave pmd empty until pte is filled */
1068 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1069 pmd_populate(mm, &_pmd, pgtable);
1071 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1073 entry = mk_pte(pages[i], vma->vm_page_prot);
1074 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1075 page_add_new_anon_rmap(pages[i], vma, haddr);
1076 pte = pte_offset_map(&_pmd, haddr);
1077 VM_BUG_ON(!pte_none(*pte));
1078 set_pte_at(mm, haddr, pte, entry);
1083 smp_wmb(); /* make pte visible before pmd */
1084 pmd_populate(mm, pmd, pgtable);
1085 page_remove_rmap(page);
1086 spin_unlock(&mm->page_table_lock);
1088 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1090 ret |= VM_FAULT_WRITE;
1097 spin_unlock(&mm->page_table_lock);
1098 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1099 mem_cgroup_uncharge_start();
1100 for (i = 0; i < HPAGE_PMD_NR; i++) {
1101 mem_cgroup_uncharge_page(pages[i]);
1104 mem_cgroup_uncharge_end();
1109 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1110 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1113 struct page *page = NULL, *new_page;
1114 unsigned long haddr;
1115 unsigned long mmun_start; /* For mmu_notifiers */
1116 unsigned long mmun_end; /* For mmu_notifiers */
1118 VM_BUG_ON(!vma->anon_vma);
1119 haddr = address & HPAGE_PMD_MASK;
1120 if (is_huge_zero_pmd(orig_pmd))
1122 spin_lock(&mm->page_table_lock);
1123 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1126 page = pmd_page(orig_pmd);
1127 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
1128 if (page_mapcount(page) == 1) {
1130 entry = pmd_mkyoung(orig_pmd);
1131 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1132 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1133 update_mmu_cache_pmd(vma, address, pmd);
1134 ret |= VM_FAULT_WRITE;
1138 spin_unlock(&mm->page_table_lock);
1140 if (transparent_hugepage_enabled(vma) &&
1141 !transparent_hugepage_debug_cow())
1142 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1143 vma, haddr, numa_node_id(), 0);
1147 if (unlikely(!new_page)) {
1148 if (is_huge_zero_pmd(orig_pmd)) {
1149 ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1150 address, pmd, orig_pmd, haddr);
1152 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1153 pmd, orig_pmd, page, haddr);
1154 if (ret & VM_FAULT_OOM)
1155 split_huge_page(page);
1158 count_vm_event(THP_FAULT_FALLBACK);
1162 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1165 split_huge_page(page);
1168 count_vm_event(THP_FAULT_FALLBACK);
1169 ret |= VM_FAULT_OOM;
1173 count_vm_event(THP_FAULT_ALLOC);
1175 if (is_huge_zero_pmd(orig_pmd))
1176 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1178 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1179 __SetPageUptodate(new_page);
1182 mmun_end = haddr + HPAGE_PMD_SIZE;
1183 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1185 spin_lock(&mm->page_table_lock);
1188 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1189 spin_unlock(&mm->page_table_lock);
1190 mem_cgroup_uncharge_page(new_page);
1195 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1196 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1197 pmdp_clear_flush(vma, haddr, pmd);
1198 page_add_new_anon_rmap(new_page, vma, haddr);
1199 set_pmd_at(mm, haddr, pmd, entry);
1200 update_mmu_cache_pmd(vma, address, pmd);
1201 if (is_huge_zero_pmd(orig_pmd)) {
1202 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1203 put_huge_zero_page();
1205 VM_BUG_ON(!PageHead(page));
1206 page_remove_rmap(page);
1209 ret |= VM_FAULT_WRITE;
1211 spin_unlock(&mm->page_table_lock);
1213 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1217 spin_unlock(&mm->page_table_lock);
1221 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1226 struct mm_struct *mm = vma->vm_mm;
1227 struct page *page = NULL;
1229 assert_spin_locked(&mm->page_table_lock);
1231 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1234 /* Avoid dumping huge zero page */
1235 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1236 return ERR_PTR(-EFAULT);
1238 page = pmd_page(*pmd);
1239 VM_BUG_ON(!PageHead(page));
1240 if (flags & FOLL_TOUCH) {
1243 * We should set the dirty bit only for FOLL_WRITE but
1244 * for now the dirty bit in the pmd is meaningless.
1245 * And if the dirty bit will become meaningful and
1246 * we'll only set it with FOLL_WRITE, an atomic
1247 * set_bit will be required on the pmd to set the
1248 * young bit, instead of the current set_pmd_at.
1250 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1251 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1253 update_mmu_cache_pmd(vma, addr, pmd);
1255 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1256 if (page->mapping && trylock_page(page)) {
1259 mlock_vma_page(page);
1263 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1264 VM_BUG_ON(!PageCompound(page));
1265 if (flags & FOLL_GET)
1266 get_page_foll(page);
1272 /* NUMA hinting page fault entry point for trans huge pmds */
1273 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1274 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1277 unsigned long haddr = addr & HPAGE_PMD_MASK;
1279 int current_nid = -1;
1282 spin_lock(&mm->page_table_lock);
1283 if (unlikely(!pmd_same(pmd, *pmdp)))
1286 page = pmd_page(pmd);
1288 current_nid = page_to_nid(page);
1289 count_vm_numa_event(NUMA_HINT_FAULTS);
1290 if (current_nid == numa_node_id())
1291 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1293 target_nid = mpol_misplaced(page, vma, haddr);
1294 if (target_nid == -1) {
1299 /* Acquire the page lock to serialise THP migrations */
1300 spin_unlock(&mm->page_table_lock);
1303 /* Confirm the PTE did not while locked */
1304 spin_lock(&mm->page_table_lock);
1305 if (unlikely(!pmd_same(pmd, *pmdp))) {
1310 spin_unlock(&mm->page_table_lock);
1312 /* Migrate the THP to the requested node */
1313 migrated = migrate_misplaced_transhuge_page(mm, vma,
1314 pmdp, pmd, addr, page, target_nid);
1318 task_numa_fault(target_nid, HPAGE_PMD_NR, true);
1322 spin_lock(&mm->page_table_lock);
1323 if (unlikely(!pmd_same(pmd, *pmdp)))
1326 pmd = pmd_mknonnuma(pmd);
1327 set_pmd_at(mm, haddr, pmdp, pmd);
1328 VM_BUG_ON(pmd_numa(*pmdp));
1329 update_mmu_cache_pmd(vma, addr, pmdp);
1331 spin_unlock(&mm->page_table_lock);
1332 if (current_nid != -1)
1333 task_numa_fault(current_nid, HPAGE_PMD_NR, false);
1337 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1338 pmd_t *pmd, unsigned long addr)
1342 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1347 * For architectures like ppc64 we look at deposited pgtable
1348 * when calling pmdp_get_and_clear. So do the
1349 * pgtable_trans_huge_withdraw after finishing pmdp related
1352 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1353 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1354 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1355 if (is_huge_zero_pmd(orig_pmd)) {
1357 spin_unlock(&tlb->mm->page_table_lock);
1358 put_huge_zero_page();
1360 page = pmd_page(orig_pmd);
1361 page_remove_rmap(page);
1362 VM_BUG_ON(page_mapcount(page) < 0);
1363 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1364 VM_BUG_ON(!PageHead(page));
1366 spin_unlock(&tlb->mm->page_table_lock);
1367 tlb_remove_page(tlb, page);
1369 pte_free(tlb->mm, pgtable);
1375 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1376 unsigned long addr, unsigned long end,
1381 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1383 * All logical pages in the range are present
1384 * if backed by a huge page.
1386 spin_unlock(&vma->vm_mm->page_table_lock);
1387 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1394 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1395 unsigned long old_addr,
1396 unsigned long new_addr, unsigned long old_end,
1397 pmd_t *old_pmd, pmd_t *new_pmd)
1402 struct mm_struct *mm = vma->vm_mm;
1404 if ((old_addr & ~HPAGE_PMD_MASK) ||
1405 (new_addr & ~HPAGE_PMD_MASK) ||
1406 old_end - old_addr < HPAGE_PMD_SIZE ||
1407 (new_vma->vm_flags & VM_NOHUGEPAGE))
1411 * The destination pmd shouldn't be established, free_pgtables()
1412 * should have release it.
1414 if (WARN_ON(!pmd_none(*new_pmd))) {
1415 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1419 ret = __pmd_trans_huge_lock(old_pmd, vma);
1421 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1422 VM_BUG_ON(!pmd_none(*new_pmd));
1423 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1424 spin_unlock(&mm->page_table_lock);
1430 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1431 unsigned long addr, pgprot_t newprot, int prot_numa)
1433 struct mm_struct *mm = vma->vm_mm;
1436 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1438 entry = pmdp_get_and_clear(mm, addr, pmd);
1440 entry = pmd_modify(entry, newprot);
1441 BUG_ON(pmd_write(entry));
1443 struct page *page = pmd_page(*pmd);
1445 /* only check non-shared pages */
1446 if (page_mapcount(page) == 1 &&
1448 entry = pmd_mknuma(entry);
1451 set_pmd_at(mm, addr, pmd, entry);
1452 spin_unlock(&vma->vm_mm->page_table_lock);
1460 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1461 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1463 * Note that if it returns 1, this routine returns without unlocking page
1464 * table locks. So callers must unlock them.
1466 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1468 spin_lock(&vma->vm_mm->page_table_lock);
1469 if (likely(pmd_trans_huge(*pmd))) {
1470 if (unlikely(pmd_trans_splitting(*pmd))) {
1471 spin_unlock(&vma->vm_mm->page_table_lock);
1472 wait_split_huge_page(vma->anon_vma, pmd);
1475 /* Thp mapped by 'pmd' is stable, so we can
1476 * handle it as it is. */
1480 spin_unlock(&vma->vm_mm->page_table_lock);
1484 pmd_t *page_check_address_pmd(struct page *page,
1485 struct mm_struct *mm,
1486 unsigned long address,
1487 enum page_check_address_pmd_flag flag)
1489 pmd_t *pmd, *ret = NULL;
1491 if (address & ~HPAGE_PMD_MASK)
1494 pmd = mm_find_pmd(mm, address);
1499 if (pmd_page(*pmd) != page)
1502 * split_vma() may create temporary aliased mappings. There is
1503 * no risk as long as all huge pmd are found and have their
1504 * splitting bit set before __split_huge_page_refcount
1505 * runs. Finding the same huge pmd more than once during the
1506 * same rmap walk is not a problem.
1508 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1509 pmd_trans_splitting(*pmd))
1511 if (pmd_trans_huge(*pmd)) {
1512 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1513 !pmd_trans_splitting(*pmd));
1520 static int __split_huge_page_splitting(struct page *page,
1521 struct vm_area_struct *vma,
1522 unsigned long address)
1524 struct mm_struct *mm = vma->vm_mm;
1527 /* For mmu_notifiers */
1528 const unsigned long mmun_start = address;
1529 const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
1531 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1532 spin_lock(&mm->page_table_lock);
1533 pmd = page_check_address_pmd(page, mm, address,
1534 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1537 * We can't temporarily set the pmd to null in order
1538 * to split it, the pmd must remain marked huge at all
1539 * times or the VM won't take the pmd_trans_huge paths
1540 * and it won't wait on the anon_vma->root->rwsem to
1541 * serialize against split_huge_page*.
1543 pmdp_splitting_flush(vma, address, pmd);
1546 spin_unlock(&mm->page_table_lock);
1547 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1552 static void __split_huge_page_refcount(struct page *page,
1553 struct list_head *list)
1556 struct zone *zone = page_zone(page);
1557 struct lruvec *lruvec;
1560 /* prevent PageLRU to go away from under us, and freeze lru stats */
1561 spin_lock_irq(&zone->lru_lock);
1562 lruvec = mem_cgroup_page_lruvec(page, zone);
1564 compound_lock(page);
1565 /* complete memcg works before add pages to LRU */
1566 mem_cgroup_split_huge_fixup(page);
1568 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1569 struct page *page_tail = page + i;
1571 /* tail_page->_mapcount cannot change */
1572 BUG_ON(page_mapcount(page_tail) < 0);
1573 tail_count += page_mapcount(page_tail);
1574 /* check for overflow */
1575 BUG_ON(tail_count < 0);
1576 BUG_ON(atomic_read(&page_tail->_count) != 0);
1578 * tail_page->_count is zero and not changing from
1579 * under us. But get_page_unless_zero() may be running
1580 * from under us on the tail_page. If we used
1581 * atomic_set() below instead of atomic_add(), we
1582 * would then run atomic_set() concurrently with
1583 * get_page_unless_zero(), and atomic_set() is
1584 * implemented in C not using locked ops. spin_unlock
1585 * on x86 sometime uses locked ops because of PPro
1586 * errata 66, 92, so unless somebody can guarantee
1587 * atomic_set() here would be safe on all archs (and
1588 * not only on x86), it's safer to use atomic_add().
1590 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1591 &page_tail->_count);
1593 /* after clearing PageTail the gup refcount can be released */
1597 * retain hwpoison flag of the poisoned tail page:
1598 * fix for the unsuitable process killed on Guest Machine(KVM)
1599 * by the memory-failure.
1601 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1602 page_tail->flags |= (page->flags &
1603 ((1L << PG_referenced) |
1604 (1L << PG_swapbacked) |
1605 (1L << PG_mlocked) |
1606 (1L << PG_uptodate) |
1608 (1L << PG_unevictable)));
1609 page_tail->flags |= (1L << PG_dirty);
1611 /* clear PageTail before overwriting first_page */
1615 * __split_huge_page_splitting() already set the
1616 * splitting bit in all pmd that could map this
1617 * hugepage, that will ensure no CPU can alter the
1618 * mapcount on the head page. The mapcount is only
1619 * accounted in the head page and it has to be
1620 * transferred to all tail pages in the below code. So
1621 * for this code to be safe, the split the mapcount
1622 * can't change. But that doesn't mean userland can't
1623 * keep changing and reading the page contents while
1624 * we transfer the mapcount, so the pmd splitting
1625 * status is achieved setting a reserved bit in the
1626 * pmd, not by clearing the present bit.
1628 page_tail->_mapcount = page->_mapcount;
1630 BUG_ON(page_tail->mapping);
1631 page_tail->mapping = page->mapping;
1633 page_tail->index = page->index + i;
1634 page_nid_xchg_last(page_tail, page_nid_last(page));
1636 BUG_ON(!PageAnon(page_tail));
1637 BUG_ON(!PageUptodate(page_tail));
1638 BUG_ON(!PageDirty(page_tail));
1639 BUG_ON(!PageSwapBacked(page_tail));
1641 lru_add_page_tail(page, page_tail, lruvec, list);
1643 atomic_sub(tail_count, &page->_count);
1644 BUG_ON(atomic_read(&page->_count) <= 0);
1646 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1648 ClearPageCompound(page);
1649 compound_unlock(page);
1650 spin_unlock_irq(&zone->lru_lock);
1652 for (i = 1; i < HPAGE_PMD_NR; i++) {
1653 struct page *page_tail = page + i;
1654 BUG_ON(page_count(page_tail) <= 0);
1656 * Tail pages may be freed if there wasn't any mapping
1657 * like if add_to_swap() is running on a lru page that
1658 * had its mapping zapped. And freeing these pages
1659 * requires taking the lru_lock so we do the put_page
1660 * of the tail pages after the split is complete.
1662 put_page(page_tail);
1666 * Only the head page (now become a regular page) is required
1667 * to be pinned by the caller.
1669 BUG_ON(page_count(page) <= 0);
1672 static int __split_huge_page_map(struct page *page,
1673 struct vm_area_struct *vma,
1674 unsigned long address)
1676 struct mm_struct *mm = vma->vm_mm;
1680 unsigned long haddr;
1682 spin_lock(&mm->page_table_lock);
1683 pmd = page_check_address_pmd(page, mm, address,
1684 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1686 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1687 pmd_populate(mm, &_pmd, pgtable);
1690 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1692 BUG_ON(PageCompound(page+i));
1693 entry = mk_pte(page + i, vma->vm_page_prot);
1694 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1695 if (!pmd_write(*pmd))
1696 entry = pte_wrprotect(entry);
1698 BUG_ON(page_mapcount(page) != 1);
1699 if (!pmd_young(*pmd))
1700 entry = pte_mkold(entry);
1702 entry = pte_mknuma(entry);
1703 pte = pte_offset_map(&_pmd, haddr);
1704 BUG_ON(!pte_none(*pte));
1705 set_pte_at(mm, haddr, pte, entry);
1709 smp_wmb(); /* make pte visible before pmd */
1711 * Up to this point the pmd is present and huge and
1712 * userland has the whole access to the hugepage
1713 * during the split (which happens in place). If we
1714 * overwrite the pmd with the not-huge version
1715 * pointing to the pte here (which of course we could
1716 * if all CPUs were bug free), userland could trigger
1717 * a small page size TLB miss on the small sized TLB
1718 * while the hugepage TLB entry is still established
1719 * in the huge TLB. Some CPU doesn't like that. See
1720 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1721 * Erratum 383 on page 93. Intel should be safe but is
1722 * also warns that it's only safe if the permission
1723 * and cache attributes of the two entries loaded in
1724 * the two TLB is identical (which should be the case
1725 * here). But it is generally safer to never allow
1726 * small and huge TLB entries for the same virtual
1727 * address to be loaded simultaneously. So instead of
1728 * doing "pmd_populate(); flush_tlb_range();" we first
1729 * mark the current pmd notpresent (atomically because
1730 * here the pmd_trans_huge and pmd_trans_splitting
1731 * must remain set at all times on the pmd until the
1732 * split is complete for this pmd), then we flush the
1733 * SMP TLB and finally we write the non-huge version
1734 * of the pmd entry with pmd_populate.
1736 pmdp_invalidate(vma, address, pmd);
1737 pmd_populate(mm, pmd, pgtable);
1740 spin_unlock(&mm->page_table_lock);
1745 /* must be called with anon_vma->root->rwsem held */
1746 static void __split_huge_page(struct page *page,
1747 struct anon_vma *anon_vma,
1748 struct list_head *list)
1750 int mapcount, mapcount2;
1751 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1752 struct anon_vma_chain *avc;
1754 BUG_ON(!PageHead(page));
1755 BUG_ON(PageTail(page));
1758 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1759 struct vm_area_struct *vma = avc->vma;
1760 unsigned long addr = vma_address(page, vma);
1761 BUG_ON(is_vma_temporary_stack(vma));
1762 mapcount += __split_huge_page_splitting(page, vma, addr);
1765 * It is critical that new vmas are added to the tail of the
1766 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1767 * and establishes a child pmd before
1768 * __split_huge_page_splitting() freezes the parent pmd (so if
1769 * we fail to prevent copy_huge_pmd() from running until the
1770 * whole __split_huge_page() is complete), we will still see
1771 * the newly established pmd of the child later during the
1772 * walk, to be able to set it as pmd_trans_splitting too.
1774 if (mapcount != page_mapcount(page))
1775 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1776 mapcount, page_mapcount(page));
1777 BUG_ON(mapcount != page_mapcount(page));
1779 __split_huge_page_refcount(page, list);
1782 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1783 struct vm_area_struct *vma = avc->vma;
1784 unsigned long addr = vma_address(page, vma);
1785 BUG_ON(is_vma_temporary_stack(vma));
1786 mapcount2 += __split_huge_page_map(page, vma, addr);
1788 if (mapcount != mapcount2)
1789 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1790 mapcount, mapcount2, page_mapcount(page));
1791 BUG_ON(mapcount != mapcount2);
1795 * Split a hugepage into normal pages. This doesn't change the position of head
1796 * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1797 * @list. Both head page and tail pages will inherit mapping, flags, and so on
1798 * from the hugepage.
1799 * Return 0 if the hugepage is split successfully otherwise return 1.
1801 int split_huge_page_to_list(struct page *page, struct list_head *list)
1803 struct anon_vma *anon_vma;
1806 BUG_ON(is_huge_zero_page(page));
1807 BUG_ON(!PageAnon(page));
1810 * The caller does not necessarily hold an mmap_sem that would prevent
1811 * the anon_vma disappearing so we first we take a reference to it
1812 * and then lock the anon_vma for write. This is similar to
1813 * page_lock_anon_vma_read except the write lock is taken to serialise
1814 * against parallel split or collapse operations.
1816 anon_vma = page_get_anon_vma(page);
1819 anon_vma_lock_write(anon_vma);
1822 if (!PageCompound(page))
1825 BUG_ON(!PageSwapBacked(page));
1826 __split_huge_page(page, anon_vma, list);
1827 count_vm_event(THP_SPLIT);
1829 BUG_ON(PageCompound(page));
1831 anon_vma_unlock_write(anon_vma);
1832 put_anon_vma(anon_vma);
1837 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1839 int hugepage_madvise(struct vm_area_struct *vma,
1840 unsigned long *vm_flags, int advice)
1842 struct mm_struct *mm = vma->vm_mm;
1847 * Be somewhat over-protective like KSM for now!
1849 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1851 if (mm->def_flags & VM_NOHUGEPAGE)
1853 *vm_flags &= ~VM_NOHUGEPAGE;
1854 *vm_flags |= VM_HUGEPAGE;
1856 * If the vma become good for khugepaged to scan,
1857 * register it here without waiting a page fault that
1858 * may not happen any time soon.
1860 if (unlikely(khugepaged_enter_vma_merge(vma)))
1863 case MADV_NOHUGEPAGE:
1865 * Be somewhat over-protective like KSM for now!
1867 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1869 *vm_flags &= ~VM_HUGEPAGE;
1870 *vm_flags |= VM_NOHUGEPAGE;
1872 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1873 * this vma even if we leave the mm registered in khugepaged if
1874 * it got registered before VM_NOHUGEPAGE was set.
1882 static int __init khugepaged_slab_init(void)
1884 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1885 sizeof(struct mm_slot),
1886 __alignof__(struct mm_slot), 0, NULL);
1893 static inline struct mm_slot *alloc_mm_slot(void)
1895 if (!mm_slot_cache) /* initialization failed */
1897 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1900 static inline void free_mm_slot(struct mm_slot *mm_slot)
1902 kmem_cache_free(mm_slot_cache, mm_slot);
1905 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1907 struct mm_slot *mm_slot;
1909 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1910 if (mm == mm_slot->mm)
1916 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1917 struct mm_slot *mm_slot)
1920 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1923 static inline int khugepaged_test_exit(struct mm_struct *mm)
1925 return atomic_read(&mm->mm_users) == 0;
1928 int __khugepaged_enter(struct mm_struct *mm)
1930 struct mm_slot *mm_slot;
1933 mm_slot = alloc_mm_slot();
1937 /* __khugepaged_exit() must not run from under us */
1938 VM_BUG_ON(khugepaged_test_exit(mm));
1939 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1940 free_mm_slot(mm_slot);
1944 spin_lock(&khugepaged_mm_lock);
1945 insert_to_mm_slots_hash(mm, mm_slot);
1947 * Insert just behind the scanning cursor, to let the area settle
1950 wakeup = list_empty(&khugepaged_scan.mm_head);
1951 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1952 spin_unlock(&khugepaged_mm_lock);
1954 atomic_inc(&mm->mm_count);
1956 wake_up_interruptible(&khugepaged_wait);
1961 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1963 unsigned long hstart, hend;
1966 * Not yet faulted in so we will register later in the
1967 * page fault if needed.
1971 /* khugepaged not yet working on file or special mappings */
1973 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1974 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1975 hend = vma->vm_end & HPAGE_PMD_MASK;
1977 return khugepaged_enter(vma);
1981 void __khugepaged_exit(struct mm_struct *mm)
1983 struct mm_slot *mm_slot;
1986 spin_lock(&khugepaged_mm_lock);
1987 mm_slot = get_mm_slot(mm);
1988 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1989 hash_del(&mm_slot->hash);
1990 list_del(&mm_slot->mm_node);
1993 spin_unlock(&khugepaged_mm_lock);
1996 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1997 free_mm_slot(mm_slot);
1999 } else if (mm_slot) {
2001 * This is required to serialize against
2002 * khugepaged_test_exit() (which is guaranteed to run
2003 * under mmap sem read mode). Stop here (after we
2004 * return all pagetables will be destroyed) until
2005 * khugepaged has finished working on the pagetables
2006 * under the mmap_sem.
2008 down_write(&mm->mmap_sem);
2009 up_write(&mm->mmap_sem);
2013 static void release_pte_page(struct page *page)
2015 /* 0 stands for page_is_file_cache(page) == false */
2016 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2018 putback_lru_page(page);
2021 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2023 while (--_pte >= pte) {
2024 pte_t pteval = *_pte;
2025 if (!pte_none(pteval))
2026 release_pte_page(pte_page(pteval));
2030 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2031 unsigned long address,
2036 int referenced = 0, none = 0;
2037 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2038 _pte++, address += PAGE_SIZE) {
2039 pte_t pteval = *_pte;
2040 if (pte_none(pteval)) {
2041 if (++none <= khugepaged_max_ptes_none)
2046 if (!pte_present(pteval) || !pte_write(pteval))
2048 page = vm_normal_page(vma, address, pteval);
2049 if (unlikely(!page))
2052 VM_BUG_ON(PageCompound(page));
2053 BUG_ON(!PageAnon(page));
2054 VM_BUG_ON(!PageSwapBacked(page));
2056 /* cannot use mapcount: can't collapse if there's a gup pin */
2057 if (page_count(page) != 1)
2060 * We can do it before isolate_lru_page because the
2061 * page can't be freed from under us. NOTE: PG_lock
2062 * is needed to serialize against split_huge_page
2063 * when invoked from the VM.
2065 if (!trylock_page(page))
2068 * Isolate the page to avoid collapsing an hugepage
2069 * currently in use by the VM.
2071 if (isolate_lru_page(page)) {
2075 /* 0 stands for page_is_file_cache(page) == false */
2076 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2077 VM_BUG_ON(!PageLocked(page));
2078 VM_BUG_ON(PageLRU(page));
2080 /* If there is no mapped pte young don't collapse the page */
2081 if (pte_young(pteval) || PageReferenced(page) ||
2082 mmu_notifier_test_young(vma->vm_mm, address))
2085 if (likely(referenced))
2088 release_pte_pages(pte, _pte);
2092 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2093 struct vm_area_struct *vma,
2094 unsigned long address,
2098 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2099 pte_t pteval = *_pte;
2100 struct page *src_page;
2102 if (pte_none(pteval)) {
2103 clear_user_highpage(page, address);
2104 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2106 src_page = pte_page(pteval);
2107 copy_user_highpage(page, src_page, address, vma);
2108 VM_BUG_ON(page_mapcount(src_page) != 1);
2109 release_pte_page(src_page);
2111 * ptl mostly unnecessary, but preempt has to
2112 * be disabled to update the per-cpu stats
2113 * inside page_remove_rmap().
2117 * paravirt calls inside pte_clear here are
2120 pte_clear(vma->vm_mm, address, _pte);
2121 page_remove_rmap(src_page);
2123 free_page_and_swap_cache(src_page);
2126 address += PAGE_SIZE;
2131 static void khugepaged_alloc_sleep(void)
2133 wait_event_freezable_timeout(khugepaged_wait, false,
2134 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2138 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2140 if (IS_ERR(*hpage)) {
2146 khugepaged_alloc_sleep();
2147 } else if (*hpage) {
2156 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2157 struct vm_area_struct *vma, unsigned long address,
2162 * Allocate the page while the vma is still valid and under
2163 * the mmap_sem read mode so there is no memory allocation
2164 * later when we take the mmap_sem in write mode. This is more
2165 * friendly behavior (OTOH it may actually hide bugs) to
2166 * filesystems in userland with daemons allocating memory in
2167 * the userland I/O paths. Allocating memory with the
2168 * mmap_sem in read mode is good idea also to allow greater
2171 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2172 node, __GFP_OTHER_NODE);
2175 * After allocating the hugepage, release the mmap_sem read lock in
2176 * preparation for taking it in write mode.
2178 up_read(&mm->mmap_sem);
2179 if (unlikely(!*hpage)) {
2180 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2181 *hpage = ERR_PTR(-ENOMEM);
2185 count_vm_event(THP_COLLAPSE_ALLOC);
2189 static struct page *khugepaged_alloc_hugepage(bool *wait)
2194 hpage = alloc_hugepage(khugepaged_defrag());
2196 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2201 khugepaged_alloc_sleep();
2203 count_vm_event(THP_COLLAPSE_ALLOC);
2204 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2209 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2212 *hpage = khugepaged_alloc_hugepage(wait);
2214 if (unlikely(!*hpage))
2221 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2222 struct vm_area_struct *vma, unsigned long address,
2225 up_read(&mm->mmap_sem);
2231 static bool hugepage_vma_check(struct vm_area_struct *vma)
2233 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2234 (vma->vm_flags & VM_NOHUGEPAGE))
2237 if (!vma->anon_vma || vma->vm_ops)
2239 if (is_vma_temporary_stack(vma))
2241 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2245 static void collapse_huge_page(struct mm_struct *mm,
2246 unsigned long address,
2247 struct page **hpage,
2248 struct vm_area_struct *vma,
2254 struct page *new_page;
2257 unsigned long hstart, hend;
2258 unsigned long mmun_start; /* For mmu_notifiers */
2259 unsigned long mmun_end; /* For mmu_notifiers */
2261 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2263 /* release the mmap_sem read lock. */
2264 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2268 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2272 * Prevent all access to pagetables with the exception of
2273 * gup_fast later hanlded by the ptep_clear_flush and the VM
2274 * handled by the anon_vma lock + PG_lock.
2276 down_write(&mm->mmap_sem);
2277 if (unlikely(khugepaged_test_exit(mm)))
2280 vma = find_vma(mm, address);
2283 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2284 hend = vma->vm_end & HPAGE_PMD_MASK;
2285 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2287 if (!hugepage_vma_check(vma))
2289 pmd = mm_find_pmd(mm, address);
2292 if (pmd_trans_huge(*pmd))
2295 anon_vma_lock_write(vma->anon_vma);
2297 pte = pte_offset_map(pmd, address);
2298 ptl = pte_lockptr(mm, pmd);
2300 mmun_start = address;
2301 mmun_end = address + HPAGE_PMD_SIZE;
2302 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2303 spin_lock(&mm->page_table_lock); /* probably unnecessary */
2305 * After this gup_fast can't run anymore. This also removes
2306 * any huge TLB entry from the CPU so we won't allow
2307 * huge and small TLB entries for the same virtual address
2308 * to avoid the risk of CPU bugs in that area.
2310 _pmd = pmdp_clear_flush(vma, address, pmd);
2311 spin_unlock(&mm->page_table_lock);
2312 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2315 isolated = __collapse_huge_page_isolate(vma, address, pte);
2318 if (unlikely(!isolated)) {
2320 spin_lock(&mm->page_table_lock);
2321 BUG_ON(!pmd_none(*pmd));
2323 * We can only use set_pmd_at when establishing
2324 * hugepmds and never for establishing regular pmds that
2325 * points to regular pagetables. Use pmd_populate for that
2327 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2328 spin_unlock(&mm->page_table_lock);
2329 anon_vma_unlock_write(vma->anon_vma);
2334 * All pages are isolated and locked so anon_vma rmap
2335 * can't run anymore.
2337 anon_vma_unlock_write(vma->anon_vma);
2339 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2341 __SetPageUptodate(new_page);
2342 pgtable = pmd_pgtable(_pmd);
2344 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2345 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2348 * spin_lock() below is not the equivalent of smp_wmb(), so
2349 * this is needed to avoid the copy_huge_page writes to become
2350 * visible after the set_pmd_at() write.
2354 spin_lock(&mm->page_table_lock);
2355 BUG_ON(!pmd_none(*pmd));
2356 page_add_new_anon_rmap(new_page, vma, address);
2357 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2358 set_pmd_at(mm, address, pmd, _pmd);
2359 update_mmu_cache_pmd(vma, address, pmd);
2360 spin_unlock(&mm->page_table_lock);
2364 khugepaged_pages_collapsed++;
2366 up_write(&mm->mmap_sem);
2370 mem_cgroup_uncharge_page(new_page);
2374 static int khugepaged_scan_pmd(struct mm_struct *mm,
2375 struct vm_area_struct *vma,
2376 unsigned long address,
2377 struct page **hpage)
2381 int ret = 0, referenced = 0, none = 0;
2383 unsigned long _address;
2385 int node = NUMA_NO_NODE;
2387 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2389 pmd = mm_find_pmd(mm, address);
2392 if (pmd_trans_huge(*pmd))
2395 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2396 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2397 _pte++, _address += PAGE_SIZE) {
2398 pte_t pteval = *_pte;
2399 if (pte_none(pteval)) {
2400 if (++none <= khugepaged_max_ptes_none)
2405 if (!pte_present(pteval) || !pte_write(pteval))
2407 page = vm_normal_page(vma, _address, pteval);
2408 if (unlikely(!page))
2411 * Chose the node of the first page. This could
2412 * be more sophisticated and look at more pages,
2413 * but isn't for now.
2415 if (node == NUMA_NO_NODE)
2416 node = page_to_nid(page);
2417 VM_BUG_ON(PageCompound(page));
2418 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2420 /* cannot use mapcount: can't collapse if there's a gup pin */
2421 if (page_count(page) != 1)
2423 if (pte_young(pteval) || PageReferenced(page) ||
2424 mmu_notifier_test_young(vma->vm_mm, address))
2430 pte_unmap_unlock(pte, ptl);
2432 /* collapse_huge_page will return with the mmap_sem released */
2433 collapse_huge_page(mm, address, hpage, vma, node);
2438 static void collect_mm_slot(struct mm_slot *mm_slot)
2440 struct mm_struct *mm = mm_slot->mm;
2442 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2444 if (khugepaged_test_exit(mm)) {
2446 hash_del(&mm_slot->hash);
2447 list_del(&mm_slot->mm_node);
2450 * Not strictly needed because the mm exited already.
2452 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2455 /* khugepaged_mm_lock actually not necessary for the below */
2456 free_mm_slot(mm_slot);
2461 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2462 struct page **hpage)
2463 __releases(&khugepaged_mm_lock)
2464 __acquires(&khugepaged_mm_lock)
2466 struct mm_slot *mm_slot;
2467 struct mm_struct *mm;
2468 struct vm_area_struct *vma;
2472 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2474 if (khugepaged_scan.mm_slot)
2475 mm_slot = khugepaged_scan.mm_slot;
2477 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2478 struct mm_slot, mm_node);
2479 khugepaged_scan.address = 0;
2480 khugepaged_scan.mm_slot = mm_slot;
2482 spin_unlock(&khugepaged_mm_lock);
2485 down_read(&mm->mmap_sem);
2486 if (unlikely(khugepaged_test_exit(mm)))
2489 vma = find_vma(mm, khugepaged_scan.address);
2492 for (; vma; vma = vma->vm_next) {
2493 unsigned long hstart, hend;
2496 if (unlikely(khugepaged_test_exit(mm))) {
2500 if (!hugepage_vma_check(vma)) {
2505 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2506 hend = vma->vm_end & HPAGE_PMD_MASK;
2509 if (khugepaged_scan.address > hend)
2511 if (khugepaged_scan.address < hstart)
2512 khugepaged_scan.address = hstart;
2513 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2515 while (khugepaged_scan.address < hend) {
2518 if (unlikely(khugepaged_test_exit(mm)))
2519 goto breakouterloop;
2521 VM_BUG_ON(khugepaged_scan.address < hstart ||
2522 khugepaged_scan.address + HPAGE_PMD_SIZE >
2524 ret = khugepaged_scan_pmd(mm, vma,
2525 khugepaged_scan.address,
2527 /* move to next address */
2528 khugepaged_scan.address += HPAGE_PMD_SIZE;
2529 progress += HPAGE_PMD_NR;
2531 /* we released mmap_sem so break loop */
2532 goto breakouterloop_mmap_sem;
2533 if (progress >= pages)
2534 goto breakouterloop;
2538 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2539 breakouterloop_mmap_sem:
2541 spin_lock(&khugepaged_mm_lock);
2542 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2544 * Release the current mm_slot if this mm is about to die, or
2545 * if we scanned all vmas of this mm.
2547 if (khugepaged_test_exit(mm) || !vma) {
2549 * Make sure that if mm_users is reaching zero while
2550 * khugepaged runs here, khugepaged_exit will find
2551 * mm_slot not pointing to the exiting mm.
2553 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2554 khugepaged_scan.mm_slot = list_entry(
2555 mm_slot->mm_node.next,
2556 struct mm_slot, mm_node);
2557 khugepaged_scan.address = 0;
2559 khugepaged_scan.mm_slot = NULL;
2560 khugepaged_full_scans++;
2563 collect_mm_slot(mm_slot);
2569 static int khugepaged_has_work(void)
2571 return !list_empty(&khugepaged_scan.mm_head) &&
2572 khugepaged_enabled();
2575 static int khugepaged_wait_event(void)
2577 return !list_empty(&khugepaged_scan.mm_head) ||
2578 kthread_should_stop();
2581 static void khugepaged_do_scan(void)
2583 struct page *hpage = NULL;
2584 unsigned int progress = 0, pass_through_head = 0;
2585 unsigned int pages = khugepaged_pages_to_scan;
2588 barrier(); /* write khugepaged_pages_to_scan to local stack */
2590 while (progress < pages) {
2591 if (!khugepaged_prealloc_page(&hpage, &wait))
2596 if (unlikely(kthread_should_stop() || freezing(current)))
2599 spin_lock(&khugepaged_mm_lock);
2600 if (!khugepaged_scan.mm_slot)
2601 pass_through_head++;
2602 if (khugepaged_has_work() &&
2603 pass_through_head < 2)
2604 progress += khugepaged_scan_mm_slot(pages - progress,
2608 spin_unlock(&khugepaged_mm_lock);
2611 if (!IS_ERR_OR_NULL(hpage))
2615 static void khugepaged_wait_work(void)
2619 if (khugepaged_has_work()) {
2620 if (!khugepaged_scan_sleep_millisecs)
2623 wait_event_freezable_timeout(khugepaged_wait,
2624 kthread_should_stop(),
2625 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2629 if (khugepaged_enabled())
2630 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2633 static int khugepaged(void *none)
2635 struct mm_slot *mm_slot;
2638 set_user_nice(current, 19);
2640 while (!kthread_should_stop()) {
2641 khugepaged_do_scan();
2642 khugepaged_wait_work();
2645 spin_lock(&khugepaged_mm_lock);
2646 mm_slot = khugepaged_scan.mm_slot;
2647 khugepaged_scan.mm_slot = NULL;
2649 collect_mm_slot(mm_slot);
2650 spin_unlock(&khugepaged_mm_lock);
2654 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2655 unsigned long haddr, pmd_t *pmd)
2657 struct mm_struct *mm = vma->vm_mm;
2662 pmdp_clear_flush(vma, haddr, pmd);
2663 /* leave pmd empty until pte is filled */
2665 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2666 pmd_populate(mm, &_pmd, pgtable);
2668 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2670 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2671 entry = pte_mkspecial(entry);
2672 pte = pte_offset_map(&_pmd, haddr);
2673 VM_BUG_ON(!pte_none(*pte));
2674 set_pte_at(mm, haddr, pte, entry);
2677 smp_wmb(); /* make pte visible before pmd */
2678 pmd_populate(mm, pmd, pgtable);
2679 put_huge_zero_page();
2682 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2686 struct mm_struct *mm = vma->vm_mm;
2687 unsigned long haddr = address & HPAGE_PMD_MASK;
2688 unsigned long mmun_start; /* For mmu_notifiers */
2689 unsigned long mmun_end; /* For mmu_notifiers */
2691 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2694 mmun_end = haddr + HPAGE_PMD_SIZE;
2695 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2696 spin_lock(&mm->page_table_lock);
2697 if (unlikely(!pmd_trans_huge(*pmd))) {
2698 spin_unlock(&mm->page_table_lock);
2699 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2702 if (is_huge_zero_pmd(*pmd)) {
2703 __split_huge_zero_page_pmd(vma, haddr, pmd);
2704 spin_unlock(&mm->page_table_lock);
2705 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2708 page = pmd_page(*pmd);
2709 VM_BUG_ON(!page_count(page));
2711 spin_unlock(&mm->page_table_lock);
2712 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2714 split_huge_page(page);
2717 BUG_ON(pmd_trans_huge(*pmd));
2720 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2723 struct vm_area_struct *vma;
2725 vma = find_vma(mm, address);
2726 BUG_ON(vma == NULL);
2727 split_huge_page_pmd(vma, address, pmd);
2730 static void split_huge_page_address(struct mm_struct *mm,
2731 unsigned long address)
2735 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2737 pmd = mm_find_pmd(mm, address);
2741 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2742 * materialize from under us.
2744 split_huge_page_pmd_mm(mm, address, pmd);
2747 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2748 unsigned long start,
2753 * If the new start address isn't hpage aligned and it could
2754 * previously contain an hugepage: check if we need to split
2757 if (start & ~HPAGE_PMD_MASK &&
2758 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2759 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2760 split_huge_page_address(vma->vm_mm, start);
2763 * If the new end address isn't hpage aligned and it could
2764 * previously contain an hugepage: check if we need to split
2767 if (end & ~HPAGE_PMD_MASK &&
2768 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2769 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2770 split_huge_page_address(vma->vm_mm, end);
2773 * If we're also updating the vma->vm_next->vm_start, if the new
2774 * vm_next->vm_start isn't page aligned and it could previously
2775 * contain an hugepage: check if we need to split an huge pmd.
2777 if (adjust_next > 0) {
2778 struct vm_area_struct *next = vma->vm_next;
2779 unsigned long nstart = next->vm_start;
2780 nstart += adjust_next << PAGE_SHIFT;
2781 if (nstart & ~HPAGE_PMD_MASK &&
2782 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2783 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2784 split_huge_page_address(next->vm_mm, nstart);