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 = strict_strtoul(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 = strict_strtoul(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 = strict_strtoul(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 = strict_strtoul(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, struct vm_area_struct *vma)
696 entry = mk_pmd(page, vma->vm_page_prot);
697 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
698 entry = pmd_mkhuge(entry);
702 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
703 struct vm_area_struct *vma,
704 unsigned long haddr, pmd_t *pmd,
709 VM_BUG_ON(!PageCompound(page));
710 pgtable = pte_alloc_one(mm, haddr);
711 if (unlikely(!pgtable))
714 clear_huge_page(page, haddr, HPAGE_PMD_NR);
716 * The memory barrier inside __SetPageUptodate makes sure that
717 * clear_huge_page writes become visible before the set_pmd_at()
720 __SetPageUptodate(page);
722 spin_lock(&mm->page_table_lock);
723 if (unlikely(!pmd_none(*pmd))) {
724 spin_unlock(&mm->page_table_lock);
725 mem_cgroup_uncharge_page(page);
727 pte_free(mm, pgtable);
730 entry = mk_huge_pmd(page, vma);
731 page_add_new_anon_rmap(page, vma, haddr);
732 set_pmd_at(mm, haddr, pmd, entry);
733 pgtable_trans_huge_deposit(mm, pmd, pgtable);
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 set_pmd_at(mm, haddr, pmd, entry);
775 pgtable_trans_huge_deposit(mm, pmd, pgtable);
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;
788 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
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);
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);
823 count_vm_event(THP_FAULT_ALLOC);
824 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
828 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
830 mem_cgroup_uncharge_page(page);
839 * Use __pte_alloc instead of pte_alloc_map, because we can't
840 * run pte_offset_map on the pmd, if an huge pmd could
841 * materialize from under us from a different thread.
843 if (unlikely(pmd_none(*pmd)) &&
844 unlikely(__pte_alloc(mm, vma, pmd, address)))
846 /* if an huge pmd materialized from under us just retry later */
847 if (unlikely(pmd_trans_huge(*pmd)))
850 * A regular pmd is established and it can't morph into a huge pmd
851 * from under us anymore at this point because we hold the mmap_sem
852 * read mode and khugepaged takes it in write mode. So now it's
853 * safe to run pte_offset_map().
855 pte = pte_offset_map(pmd, address);
856 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
859 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
860 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
861 struct vm_area_struct *vma)
863 struct page *src_page;
869 pgtable = pte_alloc_one(dst_mm, addr);
870 if (unlikely(!pgtable))
873 spin_lock(&dst_mm->page_table_lock);
874 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
878 if (unlikely(!pmd_trans_huge(pmd))) {
879 pte_free(dst_mm, pgtable);
883 * mm->page_table_lock is enough to be sure that huge zero pmd is not
884 * under splitting since we don't split the page itself, only pmd to
887 if (is_huge_zero_pmd(pmd)) {
888 struct page *zero_page;
891 * get_huge_zero_page() will never allocate a new page here,
892 * since we already have a zero page to copy. It just takes a
895 zero_page = get_huge_zero_page();
896 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
898 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
902 if (unlikely(pmd_trans_splitting(pmd))) {
903 /* split huge page running from under us */
904 spin_unlock(&src_mm->page_table_lock);
905 spin_unlock(&dst_mm->page_table_lock);
906 pte_free(dst_mm, pgtable);
908 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
911 src_page = pmd_page(pmd);
912 VM_BUG_ON(!PageHead(src_page));
914 page_dup_rmap(src_page);
915 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
917 pmdp_set_wrprotect(src_mm, addr, src_pmd);
918 pmd = pmd_mkold(pmd_wrprotect(pmd));
919 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
920 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
925 spin_unlock(&src_mm->page_table_lock);
926 spin_unlock(&dst_mm->page_table_lock);
931 void huge_pmd_set_accessed(struct mm_struct *mm,
932 struct vm_area_struct *vma,
933 unsigned long address,
934 pmd_t *pmd, pmd_t orig_pmd,
940 spin_lock(&mm->page_table_lock);
941 if (unlikely(!pmd_same(*pmd, orig_pmd)))
944 entry = pmd_mkyoung(orig_pmd);
945 haddr = address & HPAGE_PMD_MASK;
946 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
947 update_mmu_cache_pmd(vma, address, pmd);
950 spin_unlock(&mm->page_table_lock);
953 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
954 struct vm_area_struct *vma, unsigned long address,
955 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
961 unsigned long mmun_start; /* For mmu_notifiers */
962 unsigned long mmun_end; /* For mmu_notifiers */
964 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
970 if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
976 clear_user_highpage(page, address);
977 __SetPageUptodate(page);
980 mmun_end = haddr + HPAGE_PMD_SIZE;
981 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
983 spin_lock(&mm->page_table_lock);
984 if (unlikely(!pmd_same(*pmd, orig_pmd)))
987 pmdp_clear_flush(vma, haddr, pmd);
988 /* leave pmd empty until pte is filled */
990 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
991 pmd_populate(mm, &_pmd, pgtable);
993 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
995 if (haddr == (address & PAGE_MASK)) {
996 entry = mk_pte(page, vma->vm_page_prot);
997 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
998 page_add_new_anon_rmap(page, vma, haddr);
1000 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1001 entry = pte_mkspecial(entry);
1003 pte = pte_offset_map(&_pmd, haddr);
1004 VM_BUG_ON(!pte_none(*pte));
1005 set_pte_at(mm, haddr, pte, entry);
1008 smp_wmb(); /* make pte visible before pmd */
1009 pmd_populate(mm, pmd, pgtable);
1010 spin_unlock(&mm->page_table_lock);
1011 put_huge_zero_page();
1012 inc_mm_counter(mm, MM_ANONPAGES);
1014 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1016 ret |= VM_FAULT_WRITE;
1020 spin_unlock(&mm->page_table_lock);
1021 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1022 mem_cgroup_uncharge_page(page);
1027 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1028 struct vm_area_struct *vma,
1029 unsigned long address,
1030 pmd_t *pmd, pmd_t orig_pmd,
1032 unsigned long haddr)
1037 struct page **pages;
1038 unsigned long mmun_start; /* For mmu_notifiers */
1039 unsigned long mmun_end; /* For mmu_notifiers */
1041 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1043 if (unlikely(!pages)) {
1044 ret |= VM_FAULT_OOM;
1048 for (i = 0; i < HPAGE_PMD_NR; i++) {
1049 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1051 vma, address, page_to_nid(page));
1052 if (unlikely(!pages[i] ||
1053 mem_cgroup_newpage_charge(pages[i], mm,
1057 mem_cgroup_uncharge_start();
1059 mem_cgroup_uncharge_page(pages[i]);
1062 mem_cgroup_uncharge_end();
1064 ret |= VM_FAULT_OOM;
1069 for (i = 0; i < HPAGE_PMD_NR; i++) {
1070 copy_user_highpage(pages[i], page + i,
1071 haddr + PAGE_SIZE * i, vma);
1072 __SetPageUptodate(pages[i]);
1077 mmun_end = haddr + HPAGE_PMD_SIZE;
1078 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1080 spin_lock(&mm->page_table_lock);
1081 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1082 goto out_free_pages;
1083 VM_BUG_ON(!PageHead(page));
1085 pmdp_clear_flush(vma, haddr, pmd);
1086 /* leave pmd empty until pte is filled */
1088 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1089 pmd_populate(mm, &_pmd, pgtable);
1091 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1093 entry = mk_pte(pages[i], vma->vm_page_prot);
1094 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1095 page_add_new_anon_rmap(pages[i], vma, haddr);
1096 pte = pte_offset_map(&_pmd, haddr);
1097 VM_BUG_ON(!pte_none(*pte));
1098 set_pte_at(mm, haddr, pte, entry);
1103 smp_wmb(); /* make pte visible before pmd */
1104 pmd_populate(mm, pmd, pgtable);
1105 page_remove_rmap(page);
1106 spin_unlock(&mm->page_table_lock);
1108 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1110 ret |= VM_FAULT_WRITE;
1117 spin_unlock(&mm->page_table_lock);
1118 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1119 mem_cgroup_uncharge_start();
1120 for (i = 0; i < HPAGE_PMD_NR; i++) {
1121 mem_cgroup_uncharge_page(pages[i]);
1124 mem_cgroup_uncharge_end();
1129 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1130 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1133 struct page *page = NULL, *new_page;
1134 unsigned long haddr;
1135 unsigned long mmun_start; /* For mmu_notifiers */
1136 unsigned long mmun_end; /* For mmu_notifiers */
1138 VM_BUG_ON(!vma->anon_vma);
1139 haddr = address & HPAGE_PMD_MASK;
1140 if (is_huge_zero_pmd(orig_pmd))
1142 spin_lock(&mm->page_table_lock);
1143 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1146 page = pmd_page(orig_pmd);
1147 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
1148 if (page_mapcount(page) == 1) {
1150 entry = pmd_mkyoung(orig_pmd);
1151 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1152 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1153 update_mmu_cache_pmd(vma, address, pmd);
1154 ret |= VM_FAULT_WRITE;
1158 spin_unlock(&mm->page_table_lock);
1160 if (transparent_hugepage_enabled(vma) &&
1161 !transparent_hugepage_debug_cow())
1162 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1163 vma, haddr, numa_node_id(), 0);
1167 if (unlikely(!new_page)) {
1168 count_vm_event(THP_FAULT_FALLBACK);
1169 if (is_huge_zero_pmd(orig_pmd)) {
1170 ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1171 address, pmd, orig_pmd, haddr);
1173 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1174 pmd, orig_pmd, page, haddr);
1175 if (ret & VM_FAULT_OOM)
1176 split_huge_page(page);
1181 count_vm_event(THP_FAULT_ALLOC);
1183 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1186 split_huge_page(page);
1189 ret |= VM_FAULT_OOM;
1193 if (is_huge_zero_pmd(orig_pmd))
1194 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1196 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1197 __SetPageUptodate(new_page);
1200 mmun_end = haddr + HPAGE_PMD_SIZE;
1201 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1203 spin_lock(&mm->page_table_lock);
1206 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1207 spin_unlock(&mm->page_table_lock);
1208 mem_cgroup_uncharge_page(new_page);
1213 entry = mk_huge_pmd(new_page, vma);
1214 pmdp_clear_flush(vma, haddr, pmd);
1215 page_add_new_anon_rmap(new_page, vma, haddr);
1216 set_pmd_at(mm, haddr, pmd, entry);
1217 update_mmu_cache_pmd(vma, address, pmd);
1218 if (is_huge_zero_pmd(orig_pmd)) {
1219 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1220 put_huge_zero_page();
1222 VM_BUG_ON(!PageHead(page));
1223 page_remove_rmap(page);
1226 ret |= VM_FAULT_WRITE;
1228 spin_unlock(&mm->page_table_lock);
1230 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1234 spin_unlock(&mm->page_table_lock);
1238 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1243 struct mm_struct *mm = vma->vm_mm;
1244 struct page *page = NULL;
1246 assert_spin_locked(&mm->page_table_lock);
1248 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1251 /* Avoid dumping huge zero page */
1252 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1253 return ERR_PTR(-EFAULT);
1255 page = pmd_page(*pmd);
1256 VM_BUG_ON(!PageHead(page));
1257 if (flags & FOLL_TOUCH) {
1260 * We should set the dirty bit only for FOLL_WRITE but
1261 * for now the dirty bit in the pmd is meaningless.
1262 * And if the dirty bit will become meaningful and
1263 * we'll only set it with FOLL_WRITE, an atomic
1264 * set_bit will be required on the pmd to set the
1265 * young bit, instead of the current set_pmd_at.
1267 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1268 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1270 update_mmu_cache_pmd(vma, addr, pmd);
1272 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1273 if (page->mapping && trylock_page(page)) {
1276 mlock_vma_page(page);
1280 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1281 VM_BUG_ON(!PageCompound(page));
1282 if (flags & FOLL_GET)
1283 get_page_foll(page);
1289 /* NUMA hinting page fault entry point for trans huge pmds */
1290 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1291 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1294 unsigned long haddr = addr & HPAGE_PMD_MASK;
1296 int current_nid = -1;
1299 spin_lock(&mm->page_table_lock);
1300 if (unlikely(!pmd_same(pmd, *pmdp)))
1303 page = pmd_page(pmd);
1305 current_nid = page_to_nid(page);
1306 count_vm_numa_event(NUMA_HINT_FAULTS);
1307 if (current_nid == numa_node_id())
1308 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1310 target_nid = mpol_misplaced(page, vma, haddr);
1311 if (target_nid == -1) {
1316 /* Acquire the page lock to serialise THP migrations */
1317 spin_unlock(&mm->page_table_lock);
1320 /* Confirm the PTE did not while locked */
1321 spin_lock(&mm->page_table_lock);
1322 if (unlikely(!pmd_same(pmd, *pmdp))) {
1327 spin_unlock(&mm->page_table_lock);
1329 /* Migrate the THP to the requested node */
1330 migrated = migrate_misplaced_transhuge_page(mm, vma,
1331 pmdp, pmd, addr, page, target_nid);
1335 task_numa_fault(target_nid, HPAGE_PMD_NR, true);
1339 spin_lock(&mm->page_table_lock);
1340 if (unlikely(!pmd_same(pmd, *pmdp)))
1343 pmd = pmd_mknonnuma(pmd);
1344 set_pmd_at(mm, haddr, pmdp, pmd);
1345 VM_BUG_ON(pmd_numa(*pmdp));
1346 update_mmu_cache_pmd(vma, addr, pmdp);
1348 spin_unlock(&mm->page_table_lock);
1349 if (current_nid != -1)
1350 task_numa_fault(current_nid, HPAGE_PMD_NR, false);
1354 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1355 pmd_t *pmd, unsigned long addr)
1359 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1363 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1364 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1365 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1366 if (is_huge_zero_pmd(orig_pmd)) {
1368 spin_unlock(&tlb->mm->page_table_lock);
1369 put_huge_zero_page();
1371 page = pmd_page(orig_pmd);
1372 page_remove_rmap(page);
1373 VM_BUG_ON(page_mapcount(page) < 0);
1374 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1375 VM_BUG_ON(!PageHead(page));
1377 spin_unlock(&tlb->mm->page_table_lock);
1378 tlb_remove_page(tlb, page);
1380 pte_free(tlb->mm, pgtable);
1386 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1387 unsigned long addr, unsigned long end,
1392 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1394 * All logical pages in the range are present
1395 * if backed by a huge page.
1397 spin_unlock(&vma->vm_mm->page_table_lock);
1398 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1405 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1406 unsigned long old_addr,
1407 unsigned long new_addr, unsigned long old_end,
1408 pmd_t *old_pmd, pmd_t *new_pmd)
1413 struct mm_struct *mm = vma->vm_mm;
1415 if ((old_addr & ~HPAGE_PMD_MASK) ||
1416 (new_addr & ~HPAGE_PMD_MASK) ||
1417 old_end - old_addr < HPAGE_PMD_SIZE ||
1418 (new_vma->vm_flags & VM_NOHUGEPAGE))
1422 * The destination pmd shouldn't be established, free_pgtables()
1423 * should have release it.
1425 if (WARN_ON(!pmd_none(*new_pmd))) {
1426 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1430 ret = __pmd_trans_huge_lock(old_pmd, vma);
1432 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1433 VM_BUG_ON(!pmd_none(*new_pmd));
1434 set_pmd_at(mm, new_addr, new_pmd, pmd);
1435 spin_unlock(&mm->page_table_lock);
1441 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1442 unsigned long addr, pgprot_t newprot, int prot_numa)
1444 struct mm_struct *mm = vma->vm_mm;
1447 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1449 entry = pmdp_get_and_clear(mm, addr, pmd);
1451 entry = pmd_modify(entry, newprot);
1452 BUG_ON(pmd_write(entry));
1454 struct page *page = pmd_page(*pmd);
1456 /* only check non-shared pages */
1457 if (page_mapcount(page) == 1 &&
1459 entry = pmd_mknuma(entry);
1462 set_pmd_at(mm, addr, pmd, entry);
1463 spin_unlock(&vma->vm_mm->page_table_lock);
1471 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1472 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1474 * Note that if it returns 1, this routine returns without unlocking page
1475 * table locks. So callers must unlock them.
1477 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1479 spin_lock(&vma->vm_mm->page_table_lock);
1480 if (likely(pmd_trans_huge(*pmd))) {
1481 if (unlikely(pmd_trans_splitting(*pmd))) {
1482 spin_unlock(&vma->vm_mm->page_table_lock);
1483 wait_split_huge_page(vma->anon_vma, pmd);
1486 /* Thp mapped by 'pmd' is stable, so we can
1487 * handle it as it is. */
1491 spin_unlock(&vma->vm_mm->page_table_lock);
1495 pmd_t *page_check_address_pmd(struct page *page,
1496 struct mm_struct *mm,
1497 unsigned long address,
1498 enum page_check_address_pmd_flag flag)
1500 pmd_t *pmd, *ret = NULL;
1502 if (address & ~HPAGE_PMD_MASK)
1505 pmd = mm_find_pmd(mm, address);
1510 if (pmd_page(*pmd) != page)
1513 * split_vma() may create temporary aliased mappings. There is
1514 * no risk as long as all huge pmd are found and have their
1515 * splitting bit set before __split_huge_page_refcount
1516 * runs. Finding the same huge pmd more than once during the
1517 * same rmap walk is not a problem.
1519 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1520 pmd_trans_splitting(*pmd))
1522 if (pmd_trans_huge(*pmd)) {
1523 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1524 !pmd_trans_splitting(*pmd));
1531 static int __split_huge_page_splitting(struct page *page,
1532 struct vm_area_struct *vma,
1533 unsigned long address)
1535 struct mm_struct *mm = vma->vm_mm;
1538 /* For mmu_notifiers */
1539 const unsigned long mmun_start = address;
1540 const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
1542 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1543 spin_lock(&mm->page_table_lock);
1544 pmd = page_check_address_pmd(page, mm, address,
1545 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1548 * We can't temporarily set the pmd to null in order
1549 * to split it, the pmd must remain marked huge at all
1550 * times or the VM won't take the pmd_trans_huge paths
1551 * and it won't wait on the anon_vma->root->rwsem to
1552 * serialize against split_huge_page*.
1554 pmdp_splitting_flush(vma, address, pmd);
1557 spin_unlock(&mm->page_table_lock);
1558 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1563 static void __split_huge_page_refcount(struct page *page,
1564 struct list_head *list)
1567 struct zone *zone = page_zone(page);
1568 struct lruvec *lruvec;
1571 /* prevent PageLRU to go away from under us, and freeze lru stats */
1572 spin_lock_irq(&zone->lru_lock);
1573 lruvec = mem_cgroup_page_lruvec(page, zone);
1575 compound_lock(page);
1576 /* complete memcg works before add pages to LRU */
1577 mem_cgroup_split_huge_fixup(page);
1579 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1580 struct page *page_tail = page + i;
1582 /* tail_page->_mapcount cannot change */
1583 BUG_ON(page_mapcount(page_tail) < 0);
1584 tail_count += page_mapcount(page_tail);
1585 /* check for overflow */
1586 BUG_ON(tail_count < 0);
1587 BUG_ON(atomic_read(&page_tail->_count) != 0);
1589 * tail_page->_count is zero and not changing from
1590 * under us. But get_page_unless_zero() may be running
1591 * from under us on the tail_page. If we used
1592 * atomic_set() below instead of atomic_add(), we
1593 * would then run atomic_set() concurrently with
1594 * get_page_unless_zero(), and atomic_set() is
1595 * implemented in C not using locked ops. spin_unlock
1596 * on x86 sometime uses locked ops because of PPro
1597 * errata 66, 92, so unless somebody can guarantee
1598 * atomic_set() here would be safe on all archs (and
1599 * not only on x86), it's safer to use atomic_add().
1601 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1602 &page_tail->_count);
1604 /* after clearing PageTail the gup refcount can be released */
1608 * retain hwpoison flag of the poisoned tail page:
1609 * fix for the unsuitable process killed on Guest Machine(KVM)
1610 * by the memory-failure.
1612 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1613 page_tail->flags |= (page->flags &
1614 ((1L << PG_referenced) |
1615 (1L << PG_swapbacked) |
1616 (1L << PG_mlocked) |
1617 (1L << PG_uptodate)));
1618 page_tail->flags |= (1L << PG_dirty);
1620 /* clear PageTail before overwriting first_page */
1624 * __split_huge_page_splitting() already set the
1625 * splitting bit in all pmd that could map this
1626 * hugepage, that will ensure no CPU can alter the
1627 * mapcount on the head page. The mapcount is only
1628 * accounted in the head page and it has to be
1629 * transferred to all tail pages in the below code. So
1630 * for this code to be safe, the split the mapcount
1631 * can't change. But that doesn't mean userland can't
1632 * keep changing and reading the page contents while
1633 * we transfer the mapcount, so the pmd splitting
1634 * status is achieved setting a reserved bit in the
1635 * pmd, not by clearing the present bit.
1637 page_tail->_mapcount = page->_mapcount;
1639 BUG_ON(page_tail->mapping);
1640 page_tail->mapping = page->mapping;
1642 page_tail->index = page->index + i;
1643 page_nid_xchg_last(page_tail, page_nid_last(page));
1645 BUG_ON(!PageAnon(page_tail));
1646 BUG_ON(!PageUptodate(page_tail));
1647 BUG_ON(!PageDirty(page_tail));
1648 BUG_ON(!PageSwapBacked(page_tail));
1650 lru_add_page_tail(page, page_tail, lruvec, list);
1652 atomic_sub(tail_count, &page->_count);
1653 BUG_ON(atomic_read(&page->_count) <= 0);
1655 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1656 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1658 ClearPageCompound(page);
1659 compound_unlock(page);
1660 spin_unlock_irq(&zone->lru_lock);
1662 for (i = 1; i < HPAGE_PMD_NR; i++) {
1663 struct page *page_tail = page + i;
1664 BUG_ON(page_count(page_tail) <= 0);
1666 * Tail pages may be freed if there wasn't any mapping
1667 * like if add_to_swap() is running on a lru page that
1668 * had its mapping zapped. And freeing these pages
1669 * requires taking the lru_lock so we do the put_page
1670 * of the tail pages after the split is complete.
1672 put_page(page_tail);
1676 * Only the head page (now become a regular page) is required
1677 * to be pinned by the caller.
1679 BUG_ON(page_count(page) <= 0);
1682 static int __split_huge_page_map(struct page *page,
1683 struct vm_area_struct *vma,
1684 unsigned long address)
1686 struct mm_struct *mm = vma->vm_mm;
1690 unsigned long haddr;
1692 spin_lock(&mm->page_table_lock);
1693 pmd = page_check_address_pmd(page, mm, address,
1694 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1696 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1697 pmd_populate(mm, &_pmd, pgtable);
1700 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1702 BUG_ON(PageCompound(page+i));
1703 entry = mk_pte(page + i, vma->vm_page_prot);
1704 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1705 if (!pmd_write(*pmd))
1706 entry = pte_wrprotect(entry);
1708 BUG_ON(page_mapcount(page) != 1);
1709 if (!pmd_young(*pmd))
1710 entry = pte_mkold(entry);
1712 entry = pte_mknuma(entry);
1713 pte = pte_offset_map(&_pmd, haddr);
1714 BUG_ON(!pte_none(*pte));
1715 set_pte_at(mm, haddr, pte, entry);
1719 smp_wmb(); /* make pte visible before pmd */
1721 * Up to this point the pmd is present and huge and
1722 * userland has the whole access to the hugepage
1723 * during the split (which happens in place). If we
1724 * overwrite the pmd with the not-huge version
1725 * pointing to the pte here (which of course we could
1726 * if all CPUs were bug free), userland could trigger
1727 * a small page size TLB miss on the small sized TLB
1728 * while the hugepage TLB entry is still established
1729 * in the huge TLB. Some CPU doesn't like that. See
1730 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1731 * Erratum 383 on page 93. Intel should be safe but is
1732 * also warns that it's only safe if the permission
1733 * and cache attributes of the two entries loaded in
1734 * the two TLB is identical (which should be the case
1735 * here). But it is generally safer to never allow
1736 * small and huge TLB entries for the same virtual
1737 * address to be loaded simultaneously. So instead of
1738 * doing "pmd_populate(); flush_tlb_range();" we first
1739 * mark the current pmd notpresent (atomically because
1740 * here the pmd_trans_huge and pmd_trans_splitting
1741 * must remain set at all times on the pmd until the
1742 * split is complete for this pmd), then we flush the
1743 * SMP TLB and finally we write the non-huge version
1744 * of the pmd entry with pmd_populate.
1746 pmdp_invalidate(vma, address, pmd);
1747 pmd_populate(mm, pmd, pgtable);
1750 spin_unlock(&mm->page_table_lock);
1755 /* must be called with anon_vma->root->rwsem held */
1756 static void __split_huge_page(struct page *page,
1757 struct anon_vma *anon_vma,
1758 struct list_head *list)
1760 int mapcount, mapcount2;
1761 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1762 struct anon_vma_chain *avc;
1764 BUG_ON(!PageHead(page));
1765 BUG_ON(PageTail(page));
1768 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1769 struct vm_area_struct *vma = avc->vma;
1770 unsigned long addr = vma_address(page, vma);
1771 BUG_ON(is_vma_temporary_stack(vma));
1772 mapcount += __split_huge_page_splitting(page, vma, addr);
1775 * It is critical that new vmas are added to the tail of the
1776 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1777 * and establishes a child pmd before
1778 * __split_huge_page_splitting() freezes the parent pmd (so if
1779 * we fail to prevent copy_huge_pmd() from running until the
1780 * whole __split_huge_page() is complete), we will still see
1781 * the newly established pmd of the child later during the
1782 * walk, to be able to set it as pmd_trans_splitting too.
1784 if (mapcount != page_mapcount(page))
1785 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1786 mapcount, page_mapcount(page));
1787 BUG_ON(mapcount != page_mapcount(page));
1789 __split_huge_page_refcount(page, list);
1792 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1793 struct vm_area_struct *vma = avc->vma;
1794 unsigned long addr = vma_address(page, vma);
1795 BUG_ON(is_vma_temporary_stack(vma));
1796 mapcount2 += __split_huge_page_map(page, vma, addr);
1798 if (mapcount != mapcount2)
1799 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1800 mapcount, mapcount2, page_mapcount(page));
1801 BUG_ON(mapcount != mapcount2);
1805 * Split a hugepage into normal pages. This doesn't change the position of head
1806 * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1807 * @list. Both head page and tail pages will inherit mapping, flags, and so on
1808 * from the hugepage.
1809 * Return 0 if the hugepage is split successfully otherwise return 1.
1811 int split_huge_page_to_list(struct page *page, struct list_head *list)
1813 struct anon_vma *anon_vma;
1816 BUG_ON(is_huge_zero_page(page));
1817 BUG_ON(!PageAnon(page));
1820 * The caller does not necessarily hold an mmap_sem that would prevent
1821 * the anon_vma disappearing so we first we take a reference to it
1822 * and then lock the anon_vma for write. This is similar to
1823 * page_lock_anon_vma_read except the write lock is taken to serialise
1824 * against parallel split or collapse operations.
1826 anon_vma = page_get_anon_vma(page);
1829 anon_vma_lock_write(anon_vma);
1832 if (!PageCompound(page))
1835 BUG_ON(!PageSwapBacked(page));
1836 __split_huge_page(page, anon_vma, list);
1837 count_vm_event(THP_SPLIT);
1839 BUG_ON(PageCompound(page));
1841 anon_vma_unlock_write(anon_vma);
1842 put_anon_vma(anon_vma);
1847 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1849 int hugepage_madvise(struct vm_area_struct *vma,
1850 unsigned long *vm_flags, int advice)
1852 struct mm_struct *mm = vma->vm_mm;
1857 * Be somewhat over-protective like KSM for now!
1859 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1861 if (mm->def_flags & VM_NOHUGEPAGE)
1863 *vm_flags &= ~VM_NOHUGEPAGE;
1864 *vm_flags |= VM_HUGEPAGE;
1866 * If the vma become good for khugepaged to scan,
1867 * register it here without waiting a page fault that
1868 * may not happen any time soon.
1870 if (unlikely(khugepaged_enter_vma_merge(vma)))
1873 case MADV_NOHUGEPAGE:
1875 * Be somewhat over-protective like KSM for now!
1877 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1879 *vm_flags &= ~VM_HUGEPAGE;
1880 *vm_flags |= VM_NOHUGEPAGE;
1882 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1883 * this vma even if we leave the mm registered in khugepaged if
1884 * it got registered before VM_NOHUGEPAGE was set.
1892 static int __init khugepaged_slab_init(void)
1894 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1895 sizeof(struct mm_slot),
1896 __alignof__(struct mm_slot), 0, NULL);
1903 static inline struct mm_slot *alloc_mm_slot(void)
1905 if (!mm_slot_cache) /* initialization failed */
1907 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1910 static inline void free_mm_slot(struct mm_slot *mm_slot)
1912 kmem_cache_free(mm_slot_cache, mm_slot);
1915 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1917 struct mm_slot *mm_slot;
1919 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1920 if (mm == mm_slot->mm)
1926 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1927 struct mm_slot *mm_slot)
1930 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1933 static inline int khugepaged_test_exit(struct mm_struct *mm)
1935 return atomic_read(&mm->mm_users) == 0;
1938 int __khugepaged_enter(struct mm_struct *mm)
1940 struct mm_slot *mm_slot;
1943 mm_slot = alloc_mm_slot();
1947 /* __khugepaged_exit() must not run from under us */
1948 VM_BUG_ON(khugepaged_test_exit(mm));
1949 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1950 free_mm_slot(mm_slot);
1954 spin_lock(&khugepaged_mm_lock);
1955 insert_to_mm_slots_hash(mm, mm_slot);
1957 * Insert just behind the scanning cursor, to let the area settle
1960 wakeup = list_empty(&khugepaged_scan.mm_head);
1961 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1962 spin_unlock(&khugepaged_mm_lock);
1964 atomic_inc(&mm->mm_count);
1966 wake_up_interruptible(&khugepaged_wait);
1971 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1973 unsigned long hstart, hend;
1976 * Not yet faulted in so we will register later in the
1977 * page fault if needed.
1981 /* khugepaged not yet working on file or special mappings */
1983 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1984 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1985 hend = vma->vm_end & HPAGE_PMD_MASK;
1987 return khugepaged_enter(vma);
1991 void __khugepaged_exit(struct mm_struct *mm)
1993 struct mm_slot *mm_slot;
1996 spin_lock(&khugepaged_mm_lock);
1997 mm_slot = get_mm_slot(mm);
1998 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1999 hash_del(&mm_slot->hash);
2000 list_del(&mm_slot->mm_node);
2003 spin_unlock(&khugepaged_mm_lock);
2006 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2007 free_mm_slot(mm_slot);
2009 } else if (mm_slot) {
2011 * This is required to serialize against
2012 * khugepaged_test_exit() (which is guaranteed to run
2013 * under mmap sem read mode). Stop here (after we
2014 * return all pagetables will be destroyed) until
2015 * khugepaged has finished working on the pagetables
2016 * under the mmap_sem.
2018 down_write(&mm->mmap_sem);
2019 up_write(&mm->mmap_sem);
2023 static void release_pte_page(struct page *page)
2025 /* 0 stands for page_is_file_cache(page) == false */
2026 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2028 putback_lru_page(page);
2031 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2033 while (--_pte >= pte) {
2034 pte_t pteval = *_pte;
2035 if (!pte_none(pteval))
2036 release_pte_page(pte_page(pteval));
2040 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2041 unsigned long address,
2046 int referenced = 0, none = 0;
2047 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2048 _pte++, address += PAGE_SIZE) {
2049 pte_t pteval = *_pte;
2050 if (pte_none(pteval)) {
2051 if (++none <= khugepaged_max_ptes_none)
2056 if (!pte_present(pteval) || !pte_write(pteval))
2058 page = vm_normal_page(vma, address, pteval);
2059 if (unlikely(!page))
2062 VM_BUG_ON(PageCompound(page));
2063 BUG_ON(!PageAnon(page));
2064 VM_BUG_ON(!PageSwapBacked(page));
2066 /* cannot use mapcount: can't collapse if there's a gup pin */
2067 if (page_count(page) != 1)
2070 * We can do it before isolate_lru_page because the
2071 * page can't be freed from under us. NOTE: PG_lock
2072 * is needed to serialize against split_huge_page
2073 * when invoked from the VM.
2075 if (!trylock_page(page))
2078 * Isolate the page to avoid collapsing an hugepage
2079 * currently in use by the VM.
2081 if (isolate_lru_page(page)) {
2085 /* 0 stands for page_is_file_cache(page) == false */
2086 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2087 VM_BUG_ON(!PageLocked(page));
2088 VM_BUG_ON(PageLRU(page));
2090 /* If there is no mapped pte young don't collapse the page */
2091 if (pte_young(pteval) || PageReferenced(page) ||
2092 mmu_notifier_test_young(vma->vm_mm, address))
2095 if (likely(referenced))
2098 release_pte_pages(pte, _pte);
2102 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2103 struct vm_area_struct *vma,
2104 unsigned long address,
2108 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2109 pte_t pteval = *_pte;
2110 struct page *src_page;
2112 if (pte_none(pteval)) {
2113 clear_user_highpage(page, address);
2114 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2116 src_page = pte_page(pteval);
2117 copy_user_highpage(page, src_page, address, vma);
2118 VM_BUG_ON(page_mapcount(src_page) != 1);
2119 release_pte_page(src_page);
2121 * ptl mostly unnecessary, but preempt has to
2122 * be disabled to update the per-cpu stats
2123 * inside page_remove_rmap().
2127 * paravirt calls inside pte_clear here are
2130 pte_clear(vma->vm_mm, address, _pte);
2131 page_remove_rmap(src_page);
2133 free_page_and_swap_cache(src_page);
2136 address += PAGE_SIZE;
2141 static void khugepaged_alloc_sleep(void)
2143 wait_event_freezable_timeout(khugepaged_wait, false,
2144 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2148 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2150 if (IS_ERR(*hpage)) {
2156 khugepaged_alloc_sleep();
2157 } else if (*hpage) {
2166 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2167 struct vm_area_struct *vma, unsigned long address,
2172 * Allocate the page while the vma is still valid and under
2173 * the mmap_sem read mode so there is no memory allocation
2174 * later when we take the mmap_sem in write mode. This is more
2175 * friendly behavior (OTOH it may actually hide bugs) to
2176 * filesystems in userland with daemons allocating memory in
2177 * the userland I/O paths. Allocating memory with the
2178 * mmap_sem in read mode is good idea also to allow greater
2181 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2182 node, __GFP_OTHER_NODE);
2185 * After allocating the hugepage, release the mmap_sem read lock in
2186 * preparation for taking it in write mode.
2188 up_read(&mm->mmap_sem);
2189 if (unlikely(!*hpage)) {
2190 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2191 *hpage = ERR_PTR(-ENOMEM);
2195 count_vm_event(THP_COLLAPSE_ALLOC);
2199 static struct page *khugepaged_alloc_hugepage(bool *wait)
2204 hpage = alloc_hugepage(khugepaged_defrag());
2206 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2211 khugepaged_alloc_sleep();
2213 count_vm_event(THP_COLLAPSE_ALLOC);
2214 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2219 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2222 *hpage = khugepaged_alloc_hugepage(wait);
2224 if (unlikely(!*hpage))
2231 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2232 struct vm_area_struct *vma, unsigned long address,
2235 up_read(&mm->mmap_sem);
2241 static bool hugepage_vma_check(struct vm_area_struct *vma)
2243 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2244 (vma->vm_flags & VM_NOHUGEPAGE))
2247 if (!vma->anon_vma || vma->vm_ops)
2249 if (is_vma_temporary_stack(vma))
2251 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2255 static void collapse_huge_page(struct mm_struct *mm,
2256 unsigned long address,
2257 struct page **hpage,
2258 struct vm_area_struct *vma,
2264 struct page *new_page;
2267 unsigned long hstart, hend;
2268 unsigned long mmun_start; /* For mmu_notifiers */
2269 unsigned long mmun_end; /* For mmu_notifiers */
2271 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2273 /* release the mmap_sem read lock. */
2274 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2278 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2282 * Prevent all access to pagetables with the exception of
2283 * gup_fast later hanlded by the ptep_clear_flush and the VM
2284 * handled by the anon_vma lock + PG_lock.
2286 down_write(&mm->mmap_sem);
2287 if (unlikely(khugepaged_test_exit(mm)))
2290 vma = find_vma(mm, address);
2291 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2292 hend = vma->vm_end & HPAGE_PMD_MASK;
2293 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2295 if (!hugepage_vma_check(vma))
2297 pmd = mm_find_pmd(mm, address);
2300 if (pmd_trans_huge(*pmd))
2303 anon_vma_lock_write(vma->anon_vma);
2305 pte = pte_offset_map(pmd, address);
2306 ptl = pte_lockptr(mm, pmd);
2308 mmun_start = address;
2309 mmun_end = address + HPAGE_PMD_SIZE;
2310 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2311 spin_lock(&mm->page_table_lock); /* probably unnecessary */
2313 * After this gup_fast can't run anymore. This also removes
2314 * any huge TLB entry from the CPU so we won't allow
2315 * huge and small TLB entries for the same virtual address
2316 * to avoid the risk of CPU bugs in that area.
2318 _pmd = pmdp_clear_flush(vma, address, pmd);
2319 spin_unlock(&mm->page_table_lock);
2320 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2323 isolated = __collapse_huge_page_isolate(vma, address, pte);
2326 if (unlikely(!isolated)) {
2328 spin_lock(&mm->page_table_lock);
2329 BUG_ON(!pmd_none(*pmd));
2331 * We can only use set_pmd_at when establishing
2332 * hugepmds and never for establishing regular pmds that
2333 * points to regular pagetables. Use pmd_populate for that
2335 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2336 spin_unlock(&mm->page_table_lock);
2337 anon_vma_unlock_write(vma->anon_vma);
2342 * All pages are isolated and locked so anon_vma rmap
2343 * can't run anymore.
2345 anon_vma_unlock_write(vma->anon_vma);
2347 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2349 __SetPageUptodate(new_page);
2350 pgtable = pmd_pgtable(_pmd);
2352 _pmd = mk_huge_pmd(new_page, vma);
2355 * spin_lock() below is not the equivalent of smp_wmb(), so
2356 * this is needed to avoid the copy_huge_page writes to become
2357 * visible after the set_pmd_at() write.
2361 spin_lock(&mm->page_table_lock);
2362 BUG_ON(!pmd_none(*pmd));
2363 page_add_new_anon_rmap(new_page, vma, address);
2364 set_pmd_at(mm, address, pmd, _pmd);
2365 update_mmu_cache_pmd(vma, address, pmd);
2366 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2367 spin_unlock(&mm->page_table_lock);
2371 khugepaged_pages_collapsed++;
2373 up_write(&mm->mmap_sem);
2377 mem_cgroup_uncharge_page(new_page);
2381 static int khugepaged_scan_pmd(struct mm_struct *mm,
2382 struct vm_area_struct *vma,
2383 unsigned long address,
2384 struct page **hpage)
2388 int ret = 0, referenced = 0, none = 0;
2390 unsigned long _address;
2392 int node = NUMA_NO_NODE;
2394 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2396 pmd = mm_find_pmd(mm, address);
2399 if (pmd_trans_huge(*pmd))
2402 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2403 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2404 _pte++, _address += PAGE_SIZE) {
2405 pte_t pteval = *_pte;
2406 if (pte_none(pteval)) {
2407 if (++none <= khugepaged_max_ptes_none)
2412 if (!pte_present(pteval) || !pte_write(pteval))
2414 page = vm_normal_page(vma, _address, pteval);
2415 if (unlikely(!page))
2418 * Chose the node of the first page. This could
2419 * be more sophisticated and look at more pages,
2420 * but isn't for now.
2422 if (node == NUMA_NO_NODE)
2423 node = page_to_nid(page);
2424 VM_BUG_ON(PageCompound(page));
2425 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2427 /* cannot use mapcount: can't collapse if there's a gup pin */
2428 if (page_count(page) != 1)
2430 if (pte_young(pteval) || PageReferenced(page) ||
2431 mmu_notifier_test_young(vma->vm_mm, address))
2437 pte_unmap_unlock(pte, ptl);
2439 /* collapse_huge_page will return with the mmap_sem released */
2440 collapse_huge_page(mm, address, hpage, vma, node);
2445 static void collect_mm_slot(struct mm_slot *mm_slot)
2447 struct mm_struct *mm = mm_slot->mm;
2449 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2451 if (khugepaged_test_exit(mm)) {
2453 hash_del(&mm_slot->hash);
2454 list_del(&mm_slot->mm_node);
2457 * Not strictly needed because the mm exited already.
2459 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2462 /* khugepaged_mm_lock actually not necessary for the below */
2463 free_mm_slot(mm_slot);
2468 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2469 struct page **hpage)
2470 __releases(&khugepaged_mm_lock)
2471 __acquires(&khugepaged_mm_lock)
2473 struct mm_slot *mm_slot;
2474 struct mm_struct *mm;
2475 struct vm_area_struct *vma;
2479 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2481 if (khugepaged_scan.mm_slot)
2482 mm_slot = khugepaged_scan.mm_slot;
2484 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2485 struct mm_slot, mm_node);
2486 khugepaged_scan.address = 0;
2487 khugepaged_scan.mm_slot = mm_slot;
2489 spin_unlock(&khugepaged_mm_lock);
2492 down_read(&mm->mmap_sem);
2493 if (unlikely(khugepaged_test_exit(mm)))
2496 vma = find_vma(mm, khugepaged_scan.address);
2499 for (; vma; vma = vma->vm_next) {
2500 unsigned long hstart, hend;
2503 if (unlikely(khugepaged_test_exit(mm))) {
2507 if (!hugepage_vma_check(vma)) {
2512 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2513 hend = vma->vm_end & HPAGE_PMD_MASK;
2516 if (khugepaged_scan.address > hend)
2518 if (khugepaged_scan.address < hstart)
2519 khugepaged_scan.address = hstart;
2520 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2522 while (khugepaged_scan.address < hend) {
2525 if (unlikely(khugepaged_test_exit(mm)))
2526 goto breakouterloop;
2528 VM_BUG_ON(khugepaged_scan.address < hstart ||
2529 khugepaged_scan.address + HPAGE_PMD_SIZE >
2531 ret = khugepaged_scan_pmd(mm, vma,
2532 khugepaged_scan.address,
2534 /* move to next address */
2535 khugepaged_scan.address += HPAGE_PMD_SIZE;
2536 progress += HPAGE_PMD_NR;
2538 /* we released mmap_sem so break loop */
2539 goto breakouterloop_mmap_sem;
2540 if (progress >= pages)
2541 goto breakouterloop;
2545 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2546 breakouterloop_mmap_sem:
2548 spin_lock(&khugepaged_mm_lock);
2549 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2551 * Release the current mm_slot if this mm is about to die, or
2552 * if we scanned all vmas of this mm.
2554 if (khugepaged_test_exit(mm) || !vma) {
2556 * Make sure that if mm_users is reaching zero while
2557 * khugepaged runs here, khugepaged_exit will find
2558 * mm_slot not pointing to the exiting mm.
2560 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2561 khugepaged_scan.mm_slot = list_entry(
2562 mm_slot->mm_node.next,
2563 struct mm_slot, mm_node);
2564 khugepaged_scan.address = 0;
2566 khugepaged_scan.mm_slot = NULL;
2567 khugepaged_full_scans++;
2570 collect_mm_slot(mm_slot);
2576 static int khugepaged_has_work(void)
2578 return !list_empty(&khugepaged_scan.mm_head) &&
2579 khugepaged_enabled();
2582 static int khugepaged_wait_event(void)
2584 return !list_empty(&khugepaged_scan.mm_head) ||
2585 kthread_should_stop();
2588 static void khugepaged_do_scan(void)
2590 struct page *hpage = NULL;
2591 unsigned int progress = 0, pass_through_head = 0;
2592 unsigned int pages = khugepaged_pages_to_scan;
2595 barrier(); /* write khugepaged_pages_to_scan to local stack */
2597 while (progress < pages) {
2598 if (!khugepaged_prealloc_page(&hpage, &wait))
2603 if (unlikely(kthread_should_stop() || freezing(current)))
2606 spin_lock(&khugepaged_mm_lock);
2607 if (!khugepaged_scan.mm_slot)
2608 pass_through_head++;
2609 if (khugepaged_has_work() &&
2610 pass_through_head < 2)
2611 progress += khugepaged_scan_mm_slot(pages - progress,
2615 spin_unlock(&khugepaged_mm_lock);
2618 if (!IS_ERR_OR_NULL(hpage))
2622 static void khugepaged_wait_work(void)
2626 if (khugepaged_has_work()) {
2627 if (!khugepaged_scan_sleep_millisecs)
2630 wait_event_freezable_timeout(khugepaged_wait,
2631 kthread_should_stop(),
2632 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2636 if (khugepaged_enabled())
2637 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2640 static int khugepaged(void *none)
2642 struct mm_slot *mm_slot;
2645 set_user_nice(current, 19);
2647 while (!kthread_should_stop()) {
2648 khugepaged_do_scan();
2649 khugepaged_wait_work();
2652 spin_lock(&khugepaged_mm_lock);
2653 mm_slot = khugepaged_scan.mm_slot;
2654 khugepaged_scan.mm_slot = NULL;
2656 collect_mm_slot(mm_slot);
2657 spin_unlock(&khugepaged_mm_lock);
2661 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2662 unsigned long haddr, pmd_t *pmd)
2664 struct mm_struct *mm = vma->vm_mm;
2669 pmdp_clear_flush(vma, haddr, pmd);
2670 /* leave pmd empty until pte is filled */
2672 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2673 pmd_populate(mm, &_pmd, pgtable);
2675 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2677 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2678 entry = pte_mkspecial(entry);
2679 pte = pte_offset_map(&_pmd, haddr);
2680 VM_BUG_ON(!pte_none(*pte));
2681 set_pte_at(mm, haddr, pte, entry);
2684 smp_wmb(); /* make pte visible before pmd */
2685 pmd_populate(mm, pmd, pgtable);
2686 put_huge_zero_page();
2689 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2693 struct mm_struct *mm = vma->vm_mm;
2694 unsigned long haddr = address & HPAGE_PMD_MASK;
2695 unsigned long mmun_start; /* For mmu_notifiers */
2696 unsigned long mmun_end; /* For mmu_notifiers */
2698 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2701 mmun_end = haddr + HPAGE_PMD_SIZE;
2702 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2703 spin_lock(&mm->page_table_lock);
2704 if (unlikely(!pmd_trans_huge(*pmd))) {
2705 spin_unlock(&mm->page_table_lock);
2706 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2709 if (is_huge_zero_pmd(*pmd)) {
2710 __split_huge_zero_page_pmd(vma, haddr, pmd);
2711 spin_unlock(&mm->page_table_lock);
2712 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2715 page = pmd_page(*pmd);
2716 VM_BUG_ON(!page_count(page));
2718 spin_unlock(&mm->page_table_lock);
2719 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2721 split_huge_page(page);
2724 BUG_ON(pmd_trans_huge(*pmd));
2727 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2730 struct vm_area_struct *vma;
2732 vma = find_vma(mm, address);
2733 BUG_ON(vma == NULL);
2734 split_huge_page_pmd(vma, address, pmd);
2737 static void split_huge_page_address(struct mm_struct *mm,
2738 unsigned long address)
2742 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2744 pmd = mm_find_pmd(mm, address);
2748 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2749 * materialize from under us.
2751 split_huge_page_pmd_mm(mm, address, pmd);
2754 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2755 unsigned long start,
2760 * If the new start address isn't hpage aligned and it could
2761 * previously contain an hugepage: check if we need to split
2764 if (start & ~HPAGE_PMD_MASK &&
2765 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2766 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2767 split_huge_page_address(vma->vm_mm, start);
2770 * If the new end address isn't hpage aligned and it could
2771 * previously contain an hugepage: check if we need to split
2774 if (end & ~HPAGE_PMD_MASK &&
2775 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2776 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2777 split_huge_page_address(vma->vm_mm, end);
2780 * If we're also updating the vma->vm_next->vm_start, if the new
2781 * vm_next->vm_start isn't page aligned and it could previously
2782 * contain an hugepage: check if we need to split an huge pmd.
2784 if (adjust_next > 0) {
2785 struct vm_area_struct *next = vma->vm_next;
2786 unsigned long nstart = next->vm_start;
2787 nstart += adjust_next << PAGE_SHIFT;
2788 if (nstart & ~HPAGE_PMD_MASK &&
2789 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2790 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2791 split_huge_page_address(next->vm_mm, nstart);