2 * Copyright (C) 2009 Red Hat, Inc.
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/sched.h>
12 #include <linux/highmem.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mmu_notifier.h>
15 #include <linux/rmap.h>
16 #include <linux/swap.h>
17 #include <linux/shrinker.h>
18 #include <linux/mm_inline.h>
19 #include <linux/kthread.h>
20 #include <linux/khugepaged.h>
21 #include <linux/freezer.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/migrate.h>
25 #include <linux/hashtable.h>
26 #include <linux/userfaultfd_k.h>
29 #include <asm/pgalloc.h>
33 * By default transparent hugepage support is disabled in order that avoid
34 * to risk increase the memory footprint of applications without a guaranteed
35 * benefit. When transparent hugepage support is enabled, is for all mappings,
36 * and khugepaged scans all mappings.
37 * Defrag is invoked by khugepaged hugepage allocations and by page faults
38 * for all hugepage allocations.
40 unsigned long transparent_hugepage_flags __read_mostly =
41 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
42 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
44 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
45 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
47 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
48 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
49 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
51 /* default scan 8*512 pte (or vmas) every 30 second */
52 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
53 static unsigned int khugepaged_pages_collapsed;
54 static unsigned int khugepaged_full_scans;
55 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
56 /* during fragmentation poll the hugepage allocator once every minute */
57 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
58 static struct task_struct *khugepaged_thread __read_mostly;
59 static DEFINE_MUTEX(khugepaged_mutex);
60 static DEFINE_SPINLOCK(khugepaged_mm_lock);
61 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
63 * default collapse hugepages if there is at least one pte mapped like
64 * it would have happened if the vma was large enough during page
67 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
69 static int khugepaged(void *none);
70 static int khugepaged_slab_init(void);
71 static void khugepaged_slab_exit(void);
73 #define MM_SLOTS_HASH_BITS 10
74 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
76 static struct kmem_cache *mm_slot_cache __read_mostly;
79 * struct mm_slot - hash lookup from mm to mm_slot
80 * @hash: hash collision list
81 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
82 * @mm: the mm that this information is valid for
85 struct hlist_node hash;
86 struct list_head mm_node;
91 * struct khugepaged_scan - cursor for scanning
92 * @mm_head: the head of the mm list to scan
93 * @mm_slot: the current mm_slot we are scanning
94 * @address: the next address inside that to be scanned
96 * There is only the one khugepaged_scan instance of this cursor structure.
98 struct khugepaged_scan {
99 struct list_head mm_head;
100 struct mm_slot *mm_slot;
101 unsigned long address;
103 static struct khugepaged_scan khugepaged_scan = {
104 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
108 static int set_recommended_min_free_kbytes(void)
112 unsigned long recommended_min;
114 for_each_populated_zone(zone)
117 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
118 recommended_min = pageblock_nr_pages * nr_zones * 2;
121 * Make sure that on average at least two pageblocks are almost free
122 * of another type, one for a migratetype to fall back to and a
123 * second to avoid subsequent fallbacks of other types There are 3
124 * MIGRATE_TYPES we care about.
126 recommended_min += pageblock_nr_pages * nr_zones *
127 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
129 /* don't ever allow to reserve more than 5% of the lowmem */
130 recommended_min = min(recommended_min,
131 (unsigned long) nr_free_buffer_pages() / 20);
132 recommended_min <<= (PAGE_SHIFT-10);
134 if (recommended_min > min_free_kbytes) {
135 if (user_min_free_kbytes >= 0)
136 pr_info("raising min_free_kbytes from %d to %lu "
137 "to help transparent hugepage allocations\n",
138 min_free_kbytes, recommended_min);
140 min_free_kbytes = recommended_min;
142 setup_per_zone_wmarks();
146 static int start_stop_khugepaged(void)
149 if (khugepaged_enabled()) {
150 if (!khugepaged_thread)
151 khugepaged_thread = kthread_run(khugepaged, NULL,
153 if (unlikely(IS_ERR(khugepaged_thread))) {
154 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
155 err = PTR_ERR(khugepaged_thread);
156 khugepaged_thread = NULL;
160 if (!list_empty(&khugepaged_scan.mm_head))
161 wake_up_interruptible(&khugepaged_wait);
163 set_recommended_min_free_kbytes();
164 } else if (khugepaged_thread) {
165 kthread_stop(khugepaged_thread);
166 khugepaged_thread = NULL;
172 static atomic_t huge_zero_refcount;
173 struct page *huge_zero_page __read_mostly;
175 static inline bool is_huge_zero_pmd(pmd_t pmd)
177 return is_huge_zero_page(pmd_page(pmd));
180 static struct page *get_huge_zero_page(void)
182 struct page *zero_page;
184 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
185 return READ_ONCE(huge_zero_page);
187 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
190 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
193 count_vm_event(THP_ZERO_PAGE_ALLOC);
195 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
197 __free_pages(zero_page, compound_order(zero_page));
201 /* We take additional reference here. It will be put back by shrinker */
202 atomic_set(&huge_zero_refcount, 2);
204 return READ_ONCE(huge_zero_page);
207 static void put_huge_zero_page(void)
210 * Counter should never go to zero here. Only shrinker can put
213 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
216 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
217 struct shrink_control *sc)
219 /* we can free zero page only if last reference remains */
220 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
223 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
224 struct shrink_control *sc)
226 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
227 struct page *zero_page = xchg(&huge_zero_page, NULL);
228 BUG_ON(zero_page == NULL);
229 __free_pages(zero_page, compound_order(zero_page));
236 static struct shrinker huge_zero_page_shrinker = {
237 .count_objects = shrink_huge_zero_page_count,
238 .scan_objects = shrink_huge_zero_page_scan,
239 .seeks = DEFAULT_SEEKS,
244 static ssize_t double_flag_show(struct kobject *kobj,
245 struct kobj_attribute *attr, char *buf,
246 enum transparent_hugepage_flag enabled,
247 enum transparent_hugepage_flag req_madv)
249 if (test_bit(enabled, &transparent_hugepage_flags)) {
250 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
251 return sprintf(buf, "[always] madvise never\n");
252 } else if (test_bit(req_madv, &transparent_hugepage_flags))
253 return sprintf(buf, "always [madvise] never\n");
255 return sprintf(buf, "always madvise [never]\n");
257 static ssize_t double_flag_store(struct kobject *kobj,
258 struct kobj_attribute *attr,
259 const char *buf, size_t count,
260 enum transparent_hugepage_flag enabled,
261 enum transparent_hugepage_flag req_madv)
263 if (!memcmp("always", buf,
264 min(sizeof("always")-1, count))) {
265 set_bit(enabled, &transparent_hugepage_flags);
266 clear_bit(req_madv, &transparent_hugepage_flags);
267 } else if (!memcmp("madvise", buf,
268 min(sizeof("madvise")-1, count))) {
269 clear_bit(enabled, &transparent_hugepage_flags);
270 set_bit(req_madv, &transparent_hugepage_flags);
271 } else if (!memcmp("never", buf,
272 min(sizeof("never")-1, count))) {
273 clear_bit(enabled, &transparent_hugepage_flags);
274 clear_bit(req_madv, &transparent_hugepage_flags);
281 static ssize_t enabled_show(struct kobject *kobj,
282 struct kobj_attribute *attr, char *buf)
284 return double_flag_show(kobj, attr, buf,
285 TRANSPARENT_HUGEPAGE_FLAG,
286 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
288 static ssize_t enabled_store(struct kobject *kobj,
289 struct kobj_attribute *attr,
290 const char *buf, size_t count)
294 ret = double_flag_store(kobj, attr, buf, count,
295 TRANSPARENT_HUGEPAGE_FLAG,
296 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
301 mutex_lock(&khugepaged_mutex);
302 err = start_stop_khugepaged();
303 mutex_unlock(&khugepaged_mutex);
311 static struct kobj_attribute enabled_attr =
312 __ATTR(enabled, 0644, enabled_show, enabled_store);
314 static ssize_t single_flag_show(struct kobject *kobj,
315 struct kobj_attribute *attr, char *buf,
316 enum transparent_hugepage_flag flag)
318 return sprintf(buf, "%d\n",
319 !!test_bit(flag, &transparent_hugepage_flags));
322 static ssize_t single_flag_store(struct kobject *kobj,
323 struct kobj_attribute *attr,
324 const char *buf, size_t count,
325 enum transparent_hugepage_flag flag)
330 ret = kstrtoul(buf, 10, &value);
337 set_bit(flag, &transparent_hugepage_flags);
339 clear_bit(flag, &transparent_hugepage_flags);
345 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
346 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
347 * memory just to allocate one more hugepage.
349 static ssize_t defrag_show(struct kobject *kobj,
350 struct kobj_attribute *attr, char *buf)
352 return double_flag_show(kobj, attr, buf,
353 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
354 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
356 static ssize_t defrag_store(struct kobject *kobj,
357 struct kobj_attribute *attr,
358 const char *buf, size_t count)
360 return double_flag_store(kobj, attr, buf, count,
361 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
362 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
364 static struct kobj_attribute defrag_attr =
365 __ATTR(defrag, 0644, defrag_show, defrag_store);
367 static ssize_t use_zero_page_show(struct kobject *kobj,
368 struct kobj_attribute *attr, char *buf)
370 return single_flag_show(kobj, attr, buf,
371 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
373 static ssize_t use_zero_page_store(struct kobject *kobj,
374 struct kobj_attribute *attr, const char *buf, size_t count)
376 return single_flag_store(kobj, attr, buf, count,
377 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
379 static struct kobj_attribute use_zero_page_attr =
380 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
381 #ifdef CONFIG_DEBUG_VM
382 static ssize_t debug_cow_show(struct kobject *kobj,
383 struct kobj_attribute *attr, char *buf)
385 return single_flag_show(kobj, attr, buf,
386 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
388 static ssize_t debug_cow_store(struct kobject *kobj,
389 struct kobj_attribute *attr,
390 const char *buf, size_t count)
392 return single_flag_store(kobj, attr, buf, count,
393 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
395 static struct kobj_attribute debug_cow_attr =
396 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
397 #endif /* CONFIG_DEBUG_VM */
399 static struct attribute *hugepage_attr[] = {
402 &use_zero_page_attr.attr,
403 #ifdef CONFIG_DEBUG_VM
404 &debug_cow_attr.attr,
409 static struct attribute_group hugepage_attr_group = {
410 .attrs = hugepage_attr,
413 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
414 struct kobj_attribute *attr,
417 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
420 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
421 struct kobj_attribute *attr,
422 const char *buf, size_t count)
427 err = kstrtoul(buf, 10, &msecs);
428 if (err || msecs > UINT_MAX)
431 khugepaged_scan_sleep_millisecs = msecs;
432 wake_up_interruptible(&khugepaged_wait);
436 static struct kobj_attribute scan_sleep_millisecs_attr =
437 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
438 scan_sleep_millisecs_store);
440 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
441 struct kobj_attribute *attr,
444 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
447 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
448 struct kobj_attribute *attr,
449 const char *buf, size_t count)
454 err = kstrtoul(buf, 10, &msecs);
455 if (err || msecs > UINT_MAX)
458 khugepaged_alloc_sleep_millisecs = msecs;
459 wake_up_interruptible(&khugepaged_wait);
463 static struct kobj_attribute alloc_sleep_millisecs_attr =
464 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
465 alloc_sleep_millisecs_store);
467 static ssize_t pages_to_scan_show(struct kobject *kobj,
468 struct kobj_attribute *attr,
471 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
473 static ssize_t pages_to_scan_store(struct kobject *kobj,
474 struct kobj_attribute *attr,
475 const char *buf, size_t count)
480 err = kstrtoul(buf, 10, &pages);
481 if (err || !pages || pages > UINT_MAX)
484 khugepaged_pages_to_scan = pages;
488 static struct kobj_attribute pages_to_scan_attr =
489 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
490 pages_to_scan_store);
492 static ssize_t pages_collapsed_show(struct kobject *kobj,
493 struct kobj_attribute *attr,
496 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
498 static struct kobj_attribute pages_collapsed_attr =
499 __ATTR_RO(pages_collapsed);
501 static ssize_t full_scans_show(struct kobject *kobj,
502 struct kobj_attribute *attr,
505 return sprintf(buf, "%u\n", khugepaged_full_scans);
507 static struct kobj_attribute full_scans_attr =
508 __ATTR_RO(full_scans);
510 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
511 struct kobj_attribute *attr, char *buf)
513 return single_flag_show(kobj, attr, buf,
514 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
516 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
517 struct kobj_attribute *attr,
518 const char *buf, size_t count)
520 return single_flag_store(kobj, attr, buf, count,
521 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
523 static struct kobj_attribute khugepaged_defrag_attr =
524 __ATTR(defrag, 0644, khugepaged_defrag_show,
525 khugepaged_defrag_store);
528 * max_ptes_none controls if khugepaged should collapse hugepages over
529 * any unmapped ptes in turn potentially increasing the memory
530 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
531 * reduce the available free memory in the system as it
532 * runs. Increasing max_ptes_none will instead potentially reduce the
533 * free memory in the system during the khugepaged scan.
535 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
536 struct kobj_attribute *attr,
539 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
541 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
542 struct kobj_attribute *attr,
543 const char *buf, size_t count)
546 unsigned long max_ptes_none;
548 err = kstrtoul(buf, 10, &max_ptes_none);
549 if (err || max_ptes_none > HPAGE_PMD_NR-1)
552 khugepaged_max_ptes_none = max_ptes_none;
556 static struct kobj_attribute khugepaged_max_ptes_none_attr =
557 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
558 khugepaged_max_ptes_none_store);
560 static struct attribute *khugepaged_attr[] = {
561 &khugepaged_defrag_attr.attr,
562 &khugepaged_max_ptes_none_attr.attr,
563 &pages_to_scan_attr.attr,
564 &pages_collapsed_attr.attr,
565 &full_scans_attr.attr,
566 &scan_sleep_millisecs_attr.attr,
567 &alloc_sleep_millisecs_attr.attr,
571 static struct attribute_group khugepaged_attr_group = {
572 .attrs = khugepaged_attr,
573 .name = "khugepaged",
576 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
580 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
581 if (unlikely(!*hugepage_kobj)) {
582 pr_err("failed to create transparent hugepage kobject\n");
586 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
588 pr_err("failed to register transparent hugepage group\n");
592 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
594 pr_err("failed to register transparent hugepage group\n");
595 goto remove_hp_group;
601 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
603 kobject_put(*hugepage_kobj);
607 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
609 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
610 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
611 kobject_put(hugepage_kobj);
614 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
619 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
622 #endif /* CONFIG_SYSFS */
624 static int __init hugepage_init(void)
627 struct kobject *hugepage_kobj;
629 if (!has_transparent_hugepage()) {
630 transparent_hugepage_flags = 0;
634 err = hugepage_init_sysfs(&hugepage_kobj);
638 err = khugepaged_slab_init();
642 err = register_shrinker(&huge_zero_page_shrinker);
644 goto err_hzp_shrinker;
647 * By default disable transparent hugepages on smaller systems,
648 * where the extra memory used could hurt more than TLB overhead
649 * is likely to save. The admin can still enable it through /sys.
651 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
652 transparent_hugepage_flags = 0;
656 err = start_stop_khugepaged();
662 unregister_shrinker(&huge_zero_page_shrinker);
664 khugepaged_slab_exit();
666 hugepage_exit_sysfs(hugepage_kobj);
670 subsys_initcall(hugepage_init);
672 static int __init setup_transparent_hugepage(char *str)
677 if (!strcmp(str, "always")) {
678 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
679 &transparent_hugepage_flags);
680 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
681 &transparent_hugepage_flags);
683 } else if (!strcmp(str, "madvise")) {
684 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
685 &transparent_hugepage_flags);
686 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
687 &transparent_hugepage_flags);
689 } else if (!strcmp(str, "never")) {
690 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
691 &transparent_hugepage_flags);
692 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
693 &transparent_hugepage_flags);
698 pr_warn("transparent_hugepage= cannot parse, ignored\n");
701 __setup("transparent_hugepage=", setup_transparent_hugepage);
703 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
705 if (likely(vma->vm_flags & VM_WRITE))
706 pmd = pmd_mkwrite(pmd);
710 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
713 entry = mk_pmd(page, prot);
714 entry = pmd_mkhuge(entry);
718 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
719 struct vm_area_struct *vma,
720 unsigned long address, pmd_t *pmd,
721 struct page *page, gfp_t gfp,
724 struct mem_cgroup *memcg;
727 unsigned long haddr = address & HPAGE_PMD_MASK;
729 VM_BUG_ON_PAGE(!PageCompound(page), page);
731 if (mem_cgroup_try_charge(page, mm, gfp, &memcg)) {
733 count_vm_event(THP_FAULT_FALLBACK);
734 return VM_FAULT_FALLBACK;
737 pgtable = pte_alloc_one(mm, haddr);
738 if (unlikely(!pgtable)) {
739 mem_cgroup_cancel_charge(page, memcg);
744 clear_huge_page(page, haddr, HPAGE_PMD_NR);
746 * The memory barrier inside __SetPageUptodate makes sure that
747 * clear_huge_page writes become visible before the set_pmd_at()
750 __SetPageUptodate(page);
752 ptl = pmd_lock(mm, pmd);
753 if (unlikely(!pmd_none(*pmd))) {
755 mem_cgroup_cancel_charge(page, memcg);
757 pte_free(mm, pgtable);
761 /* Deliver the page fault to userland */
762 if (userfaultfd_missing(vma)) {
766 mem_cgroup_cancel_charge(page, memcg);
768 pte_free(mm, pgtable);
769 ret = handle_userfault(vma, address, flags,
771 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
775 entry = mk_huge_pmd(page, vma->vm_page_prot);
776 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
777 page_add_new_anon_rmap(page, vma, haddr);
778 mem_cgroup_commit_charge(page, memcg, false);
779 lru_cache_add_active_or_unevictable(page, vma);
780 pgtable_trans_huge_deposit(mm, pmd, pgtable);
781 set_pmd_at(mm, haddr, pmd, entry);
782 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
783 atomic_long_inc(&mm->nr_ptes);
785 count_vm_event(THP_FAULT_ALLOC);
791 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
793 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
796 /* Caller must hold page table lock. */
797 static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
798 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
799 struct page *zero_page)
802 entry = mk_pmd(zero_page, vma->vm_page_prot);
803 entry = pmd_mkhuge(entry);
804 pgtable_trans_huge_deposit(mm, pmd, pgtable);
805 set_pmd_at(mm, haddr, pmd, entry);
806 atomic_long_inc(&mm->nr_ptes);
809 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
810 unsigned long address, pmd_t *pmd,
815 unsigned long haddr = address & HPAGE_PMD_MASK;
817 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
818 return VM_FAULT_FALLBACK;
819 if (unlikely(anon_vma_prepare(vma)))
821 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
823 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
824 transparent_hugepage_use_zero_page()) {
827 struct page *zero_page;
830 pgtable = pte_alloc_one(mm, haddr);
831 if (unlikely(!pgtable))
833 zero_page = get_huge_zero_page();
834 if (unlikely(!zero_page)) {
835 pte_free(mm, pgtable);
836 count_vm_event(THP_FAULT_FALLBACK);
837 return VM_FAULT_FALLBACK;
839 ptl = pmd_lock(mm, pmd);
842 if (pmd_none(*pmd)) {
843 if (userfaultfd_missing(vma)) {
845 ret = handle_userfault(vma, address, flags,
847 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
849 set_huge_zero_page(pgtable, mm, vma,
858 pte_free(mm, pgtable);
859 put_huge_zero_page();
863 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
864 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
865 if (unlikely(!page)) {
866 count_vm_event(THP_FAULT_FALLBACK);
867 return VM_FAULT_FALLBACK;
869 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
873 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
874 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
875 struct vm_area_struct *vma)
877 spinlock_t *dst_ptl, *src_ptl;
878 struct page *src_page;
884 pgtable = pte_alloc_one(dst_mm, addr);
885 if (unlikely(!pgtable))
888 dst_ptl = pmd_lock(dst_mm, dst_pmd);
889 src_ptl = pmd_lockptr(src_mm, src_pmd);
890 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
894 if (unlikely(!pmd_trans_huge(pmd))) {
895 pte_free(dst_mm, pgtable);
899 * When page table lock is held, the huge zero pmd should not be
900 * under splitting since we don't split the page itself, only pmd to
903 if (is_huge_zero_pmd(pmd)) {
904 struct page *zero_page;
906 * get_huge_zero_page() will never allocate a new page here,
907 * since we already have a zero page to copy. It just takes a
910 zero_page = get_huge_zero_page();
911 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
917 if (unlikely(pmd_trans_splitting(pmd))) {
918 /* split huge page running from under us */
919 spin_unlock(src_ptl);
920 spin_unlock(dst_ptl);
921 pte_free(dst_mm, pgtable);
923 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
926 src_page = pmd_page(pmd);
927 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
929 page_dup_rmap(src_page);
930 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
932 pmdp_set_wrprotect(src_mm, addr, src_pmd);
933 pmd = pmd_mkold(pmd_wrprotect(pmd));
934 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
935 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
936 atomic_long_inc(&dst_mm->nr_ptes);
940 spin_unlock(src_ptl);
941 spin_unlock(dst_ptl);
946 void huge_pmd_set_accessed(struct mm_struct *mm,
947 struct vm_area_struct *vma,
948 unsigned long address,
949 pmd_t *pmd, pmd_t orig_pmd,
956 ptl = pmd_lock(mm, pmd);
957 if (unlikely(!pmd_same(*pmd, orig_pmd)))
960 entry = pmd_mkyoung(orig_pmd);
961 haddr = address & HPAGE_PMD_MASK;
962 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
963 update_mmu_cache_pmd(vma, address, pmd);
970 * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages
971 * during copy_user_huge_page()'s copy_page_rep(): in the case when
972 * the source page gets split and a tail freed before copy completes.
973 * Called under pmd_lock of checked pmd, so safe from splitting itself.
975 static void get_user_huge_page(struct page *page)
977 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
978 struct page *endpage = page + HPAGE_PMD_NR;
980 atomic_add(HPAGE_PMD_NR, &page->_count);
981 while (++page < endpage)
982 get_huge_page_tail(page);
988 static void put_user_huge_page(struct page *page)
990 if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
991 struct page *endpage = page + HPAGE_PMD_NR;
993 while (page < endpage)
1000 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1001 struct vm_area_struct *vma,
1002 unsigned long address,
1003 pmd_t *pmd, pmd_t orig_pmd,
1005 unsigned long haddr)
1007 struct mem_cgroup *memcg;
1012 struct page **pages;
1013 unsigned long mmun_start; /* For mmu_notifiers */
1014 unsigned long mmun_end; /* For mmu_notifiers */
1016 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1018 if (unlikely(!pages)) {
1019 ret |= VM_FAULT_OOM;
1023 for (i = 0; i < HPAGE_PMD_NR; i++) {
1024 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1026 vma, address, page_to_nid(page));
1027 if (unlikely(!pages[i] ||
1028 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1033 memcg = (void *)page_private(pages[i]);
1034 set_page_private(pages[i], 0);
1035 mem_cgroup_cancel_charge(pages[i], memcg);
1039 ret |= VM_FAULT_OOM;
1042 set_page_private(pages[i], (unsigned long)memcg);
1045 for (i = 0; i < HPAGE_PMD_NR; i++) {
1046 copy_user_highpage(pages[i], page + i,
1047 haddr + PAGE_SIZE * i, vma);
1048 __SetPageUptodate(pages[i]);
1053 mmun_end = haddr + HPAGE_PMD_SIZE;
1054 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1056 ptl = pmd_lock(mm, pmd);
1057 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1058 goto out_free_pages;
1059 VM_BUG_ON_PAGE(!PageHead(page), page);
1061 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1062 /* leave pmd empty until pte is filled */
1064 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1065 pmd_populate(mm, &_pmd, pgtable);
1067 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1069 entry = mk_pte(pages[i], vma->vm_page_prot);
1070 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1071 memcg = (void *)page_private(pages[i]);
1072 set_page_private(pages[i], 0);
1073 page_add_new_anon_rmap(pages[i], vma, haddr);
1074 mem_cgroup_commit_charge(pages[i], memcg, false);
1075 lru_cache_add_active_or_unevictable(pages[i], vma);
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);
1088 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1090 ret |= VM_FAULT_WRITE;
1098 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1099 for (i = 0; i < HPAGE_PMD_NR; i++) {
1100 memcg = (void *)page_private(pages[i]);
1101 set_page_private(pages[i], 0);
1102 mem_cgroup_cancel_charge(pages[i], memcg);
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)
1114 struct page *page = NULL, *new_page;
1115 struct mem_cgroup *memcg;
1116 unsigned long haddr;
1117 unsigned long mmun_start; /* For mmu_notifiers */
1118 unsigned long mmun_end; /* For mmu_notifiers */
1119 gfp_t huge_gfp; /* for allocation and charge */
1121 ptl = pmd_lockptr(mm, pmd);
1122 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1123 haddr = address & HPAGE_PMD_MASK;
1124 if (is_huge_zero_pmd(orig_pmd))
1127 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1130 page = pmd_page(orig_pmd);
1131 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1132 if (page_mapcount(page) == 1) {
1134 entry = pmd_mkyoung(orig_pmd);
1135 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1136 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1137 update_mmu_cache_pmd(vma, address, pmd);
1138 ret |= VM_FAULT_WRITE;
1141 get_user_huge_page(page);
1144 if (transparent_hugepage_enabled(vma) &&
1145 !transparent_hugepage_debug_cow()) {
1146 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1147 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1151 if (unlikely(!new_page)) {
1153 split_huge_page_pmd(vma, address, pmd);
1154 ret |= VM_FAULT_FALLBACK;
1156 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1157 pmd, orig_pmd, page, haddr);
1158 if (ret & VM_FAULT_OOM) {
1159 split_huge_page(page);
1160 ret |= VM_FAULT_FALLBACK;
1162 put_user_huge_page(page);
1164 count_vm_event(THP_FAULT_FALLBACK);
1168 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) {
1171 split_huge_page(page);
1172 put_user_huge_page(page);
1174 split_huge_page_pmd(vma, address, pmd);
1175 ret |= VM_FAULT_FALLBACK;
1176 count_vm_event(THP_FAULT_FALLBACK);
1180 count_vm_event(THP_FAULT_ALLOC);
1183 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1185 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1186 __SetPageUptodate(new_page);
1189 mmun_end = haddr + HPAGE_PMD_SIZE;
1190 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1194 put_user_huge_page(page);
1195 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1197 mem_cgroup_cancel_charge(new_page, memcg);
1202 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1203 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1204 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1205 page_add_new_anon_rmap(new_page, vma, haddr);
1206 mem_cgroup_commit_charge(new_page, memcg, false);
1207 lru_cache_add_active_or_unevictable(new_page, vma);
1208 set_pmd_at(mm, haddr, pmd, entry);
1209 update_mmu_cache_pmd(vma, address, pmd);
1211 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1212 put_huge_zero_page();
1214 VM_BUG_ON_PAGE(!PageHead(page), page);
1215 page_remove_rmap(page);
1218 ret |= VM_FAULT_WRITE;
1222 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1230 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1235 struct mm_struct *mm = vma->vm_mm;
1236 struct page *page = NULL;
1238 assert_spin_locked(pmd_lockptr(mm, pmd));
1240 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1243 /* Avoid dumping huge zero page */
1244 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1245 return ERR_PTR(-EFAULT);
1247 /* Full NUMA hinting faults to serialise migration in fault paths */
1248 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1251 page = pmd_page(*pmd);
1252 VM_BUG_ON_PAGE(!PageHead(page), page);
1253 if (flags & FOLL_TOUCH) {
1256 * We should set the dirty bit only for FOLL_WRITE but
1257 * for now the dirty bit in the pmd is meaningless.
1258 * And if the dirty bit will become meaningful and
1259 * we'll only set it with FOLL_WRITE, an atomic
1260 * set_bit will be required on the pmd to set the
1261 * young bit, instead of the current set_pmd_at.
1263 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1264 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1266 update_mmu_cache_pmd(vma, addr, pmd);
1268 if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) {
1269 if (page->mapping && trylock_page(page)) {
1272 mlock_vma_page(page);
1276 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1277 VM_BUG_ON_PAGE(!PageCompound(page), page);
1278 if (flags & FOLL_GET)
1279 get_page_foll(page);
1285 /* NUMA hinting page fault entry point for trans huge pmds */
1286 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1287 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1290 struct anon_vma *anon_vma = NULL;
1292 unsigned long haddr = addr & HPAGE_PMD_MASK;
1293 int page_nid = -1, this_nid = numa_node_id();
1294 int target_nid, last_cpupid = -1;
1296 bool migrated = false;
1300 /* A PROT_NONE fault should not end up here */
1301 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1303 ptl = pmd_lock(mm, pmdp);
1304 if (unlikely(!pmd_same(pmd, *pmdp)))
1308 * If there are potential migrations, wait for completion and retry
1309 * without disrupting NUMA hinting information. Do not relock and
1310 * check_same as the page may no longer be mapped.
1312 if (unlikely(pmd_trans_migrating(*pmdp))) {
1313 page = pmd_page(*pmdp);
1315 wait_on_page_locked(page);
1319 page = pmd_page(pmd);
1320 BUG_ON(is_huge_zero_page(page));
1321 page_nid = page_to_nid(page);
1322 last_cpupid = page_cpupid_last(page);
1323 count_vm_numa_event(NUMA_HINT_FAULTS);
1324 if (page_nid == this_nid) {
1325 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1326 flags |= TNF_FAULT_LOCAL;
1329 /* See similar comment in do_numa_page for explanation */
1330 if (!(vma->vm_flags & VM_WRITE))
1331 flags |= TNF_NO_GROUP;
1334 * Acquire the page lock to serialise THP migrations but avoid dropping
1335 * page_table_lock if at all possible
1337 page_locked = trylock_page(page);
1338 target_nid = mpol_misplaced(page, vma, haddr);
1339 if (target_nid == -1) {
1340 /* If the page was locked, there are no parallel migrations */
1345 /* Migration could have started since the pmd_trans_migrating check */
1348 wait_on_page_locked(page);
1354 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1355 * to serialises splits
1359 anon_vma = page_lock_anon_vma_read(page);
1361 /* Confirm the PMD did not change while page_table_lock was released */
1363 if (unlikely(!pmd_same(pmd, *pmdp))) {
1370 /* Bail if we fail to protect against THP splits for any reason */
1371 if (unlikely(!anon_vma)) {
1378 * Migrate the THP to the requested node, returns with page unlocked
1379 * and access rights restored.
1382 migrated = migrate_misplaced_transhuge_page(mm, vma,
1383 pmdp, pmd, addr, page, target_nid);
1385 flags |= TNF_MIGRATED;
1386 page_nid = target_nid;
1388 flags |= TNF_MIGRATE_FAIL;
1392 BUG_ON(!PageLocked(page));
1393 was_writable = pmd_write(pmd);
1394 pmd = pmd_modify(pmd, vma->vm_page_prot);
1395 pmd = pmd_mkyoung(pmd);
1397 pmd = pmd_mkwrite(pmd);
1398 set_pmd_at(mm, haddr, pmdp, pmd);
1399 update_mmu_cache_pmd(vma, addr, pmdp);
1406 page_unlock_anon_vma_read(anon_vma);
1409 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1414 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1415 pmd_t *pmd, unsigned long addr)
1420 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1425 * For architectures like ppc64 we look at deposited pgtable
1426 * when calling pmdp_huge_get_and_clear. So do the
1427 * pgtable_trans_huge_withdraw after finishing pmdp related
1430 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1432 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1433 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1434 if (is_huge_zero_pmd(orig_pmd)) {
1435 atomic_long_dec(&tlb->mm->nr_ptes);
1437 put_huge_zero_page();
1439 page = pmd_page(orig_pmd);
1440 page_remove_rmap(page);
1441 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1442 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1443 VM_BUG_ON_PAGE(!PageHead(page), page);
1444 atomic_long_dec(&tlb->mm->nr_ptes);
1446 tlb_remove_page(tlb, page);
1448 pte_free(tlb->mm, pgtable);
1454 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1455 unsigned long old_addr,
1456 unsigned long new_addr, unsigned long old_end,
1457 pmd_t *old_pmd, pmd_t *new_pmd)
1459 spinlock_t *old_ptl, *new_ptl;
1463 struct mm_struct *mm = vma->vm_mm;
1465 if ((old_addr & ~HPAGE_PMD_MASK) ||
1466 (new_addr & ~HPAGE_PMD_MASK) ||
1467 old_end - old_addr < HPAGE_PMD_SIZE ||
1468 (new_vma->vm_flags & VM_NOHUGEPAGE))
1472 * The destination pmd shouldn't be established, free_pgtables()
1473 * should have release it.
1475 if (WARN_ON(!pmd_none(*new_pmd))) {
1476 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1481 * We don't have to worry about the ordering of src and dst
1482 * ptlocks because exclusive mmap_sem prevents deadlock.
1484 ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
1486 new_ptl = pmd_lockptr(mm, new_pmd);
1487 if (new_ptl != old_ptl)
1488 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1489 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1490 VM_BUG_ON(!pmd_none(*new_pmd));
1492 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1494 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1495 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1497 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1498 if (new_ptl != old_ptl)
1499 spin_unlock(new_ptl);
1500 spin_unlock(old_ptl);
1508 * - 0 if PMD could not be locked
1509 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1510 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1512 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1513 unsigned long addr, pgprot_t newprot, int prot_numa)
1515 struct mm_struct *mm = vma->vm_mm;
1519 if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1521 bool preserve_write = prot_numa && pmd_write(*pmd);
1525 * Avoid trapping faults against the zero page. The read-only
1526 * data is likely to be read-cached on the local CPU and
1527 * local/remote hits to the zero page are not interesting.
1529 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1534 if (!prot_numa || !pmd_protnone(*pmd)) {
1535 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1536 entry = pmd_modify(entry, newprot);
1538 entry = pmd_mkwrite(entry);
1540 set_pmd_at(mm, addr, pmd, entry);
1541 BUG_ON(!preserve_write && pmd_write(entry));
1550 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1551 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1553 * Note that if it returns 1, this routine returns without unlocking page
1554 * table locks. So callers must unlock them.
1556 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1559 *ptl = pmd_lock(vma->vm_mm, pmd);
1560 if (likely(pmd_trans_huge(*pmd))) {
1561 if (unlikely(pmd_trans_splitting(*pmd))) {
1563 wait_split_huge_page(vma->anon_vma, pmd);
1566 /* Thp mapped by 'pmd' is stable, so we can
1567 * handle it as it is. */
1576 * This function returns whether a given @page is mapped onto the @address
1577 * in the virtual space of @mm.
1579 * When it's true, this function returns *pmd with holding the page table lock
1580 * and passing it back to the caller via @ptl.
1581 * If it's false, returns NULL without holding the page table lock.
1583 pmd_t *page_check_address_pmd(struct page *page,
1584 struct mm_struct *mm,
1585 unsigned long address,
1586 enum page_check_address_pmd_flag flag,
1593 if (address & ~HPAGE_PMD_MASK)
1596 pgd = pgd_offset(mm, address);
1597 if (!pgd_present(*pgd))
1599 pud = pud_offset(pgd, address);
1600 if (!pud_present(*pud))
1602 pmd = pmd_offset(pud, address);
1604 *ptl = pmd_lock(mm, pmd);
1605 if (!pmd_present(*pmd))
1607 if (pmd_page(*pmd) != page)
1610 * split_vma() may create temporary aliased mappings. There is
1611 * no risk as long as all huge pmd are found and have their
1612 * splitting bit set before __split_huge_page_refcount
1613 * runs. Finding the same huge pmd more than once during the
1614 * same rmap walk is not a problem.
1616 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1617 pmd_trans_splitting(*pmd))
1619 if (pmd_trans_huge(*pmd)) {
1620 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1621 !pmd_trans_splitting(*pmd));
1629 static int __split_huge_page_splitting(struct page *page,
1630 struct vm_area_struct *vma,
1631 unsigned long address)
1633 struct mm_struct *mm = vma->vm_mm;
1637 /* For mmu_notifiers */
1638 const unsigned long mmun_start = address;
1639 const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
1641 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1642 pmd = page_check_address_pmd(page, mm, address,
1643 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl);
1646 * We can't temporarily set the pmd to null in order
1647 * to split it, the pmd must remain marked huge at all
1648 * times or the VM won't take the pmd_trans_huge paths
1649 * and it won't wait on the anon_vma->root->rwsem to
1650 * serialize against split_huge_page*.
1652 pmdp_splitting_flush(vma, address, pmd);
1657 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1662 static void __split_huge_page_refcount(struct page *page,
1663 struct list_head *list)
1666 struct zone *zone = page_zone(page);
1667 struct lruvec *lruvec;
1670 /* prevent PageLRU to go away from under us, and freeze lru stats */
1671 spin_lock_irq(&zone->lru_lock);
1672 lruvec = mem_cgroup_page_lruvec(page, zone);
1674 compound_lock(page);
1675 /* complete memcg works before add pages to LRU */
1676 mem_cgroup_split_huge_fixup(page);
1678 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1679 struct page *page_tail = page + i;
1681 /* tail_page->_mapcount cannot change */
1682 BUG_ON(page_mapcount(page_tail) < 0);
1683 tail_count += page_mapcount(page_tail);
1684 /* check for overflow */
1685 BUG_ON(tail_count < 0);
1686 BUG_ON(atomic_read(&page_tail->_count) != 0);
1688 * tail_page->_count is zero and not changing from
1689 * under us. But get_page_unless_zero() may be running
1690 * from under us on the tail_page. If we used
1691 * atomic_set() below instead of atomic_add(), we
1692 * would then run atomic_set() concurrently with
1693 * get_page_unless_zero(), and atomic_set() is
1694 * implemented in C not using locked ops. spin_unlock
1695 * on x86 sometime uses locked ops because of PPro
1696 * errata 66, 92, so unless somebody can guarantee
1697 * atomic_set() here would be safe on all archs (and
1698 * not only on x86), it's safer to use atomic_add().
1700 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1701 &page_tail->_count);
1703 /* after clearing PageTail the gup refcount can be released */
1704 smp_mb__after_atomic();
1706 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1707 page_tail->flags |= (page->flags &
1708 ((1L << PG_referenced) |
1709 (1L << PG_swapbacked) |
1710 (1L << PG_mlocked) |
1711 (1L << PG_uptodate) |
1713 (1L << PG_unevictable)));
1714 page_tail->flags |= (1L << PG_dirty);
1716 /* clear PageTail before overwriting first_page */
1720 * __split_huge_page_splitting() already set the
1721 * splitting bit in all pmd that could map this
1722 * hugepage, that will ensure no CPU can alter the
1723 * mapcount on the head page. The mapcount is only
1724 * accounted in the head page and it has to be
1725 * transferred to all tail pages in the below code. So
1726 * for this code to be safe, the split the mapcount
1727 * can't change. But that doesn't mean userland can't
1728 * keep changing and reading the page contents while
1729 * we transfer the mapcount, so the pmd splitting
1730 * status is achieved setting a reserved bit in the
1731 * pmd, not by clearing the present bit.
1733 page_tail->_mapcount = page->_mapcount;
1735 BUG_ON(page_tail->mapping);
1736 page_tail->mapping = page->mapping;
1738 page_tail->index = page->index + i;
1739 page_cpupid_xchg_last(page_tail, page_cpupid_last(page));
1741 BUG_ON(!PageAnon(page_tail));
1742 BUG_ON(!PageUptodate(page_tail));
1743 BUG_ON(!PageDirty(page_tail));
1744 BUG_ON(!PageSwapBacked(page_tail));
1746 lru_add_page_tail(page, page_tail, lruvec, list);
1748 atomic_sub(tail_count, &page->_count);
1749 BUG_ON(atomic_read(&page->_count) <= 0);
1751 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1753 ClearPageCompound(page);
1754 compound_unlock(page);
1755 spin_unlock_irq(&zone->lru_lock);
1757 for (i = 1; i < HPAGE_PMD_NR; i++) {
1758 struct page *page_tail = page + i;
1759 BUG_ON(page_count(page_tail) <= 0);
1761 * Tail pages may be freed if there wasn't any mapping
1762 * like if add_to_swap() is running on a lru page that
1763 * had its mapping zapped. And freeing these pages
1764 * requires taking the lru_lock so we do the put_page
1765 * of the tail pages after the split is complete.
1767 put_page(page_tail);
1771 * Only the head page (now become a regular page) is required
1772 * to be pinned by the caller.
1774 BUG_ON(page_count(page) <= 0);
1777 static int __split_huge_page_map(struct page *page,
1778 struct vm_area_struct *vma,
1779 unsigned long address)
1781 struct mm_struct *mm = vma->vm_mm;
1786 unsigned long haddr;
1788 pmd = page_check_address_pmd(page, mm, address,
1789 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl);
1791 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1792 pmd_populate(mm, &_pmd, pgtable);
1793 if (pmd_write(*pmd))
1794 BUG_ON(page_mapcount(page) != 1);
1797 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1799 BUG_ON(PageCompound(page+i));
1801 * Note that NUMA hinting access restrictions are not
1802 * transferred to avoid any possibility of altering
1803 * permissions across VMAs.
1805 entry = mk_pte(page + i, vma->vm_page_prot);
1806 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1807 if (!pmd_write(*pmd))
1808 entry = pte_wrprotect(entry);
1809 if (!pmd_young(*pmd))
1810 entry = pte_mkold(entry);
1811 pte = pte_offset_map(&_pmd, haddr);
1812 BUG_ON(!pte_none(*pte));
1813 set_pte_at(mm, haddr, pte, entry);
1817 smp_wmb(); /* make pte visible before pmd */
1819 * Up to this point the pmd is present and huge and
1820 * userland has the whole access to the hugepage
1821 * during the split (which happens in place). If we
1822 * overwrite the pmd with the not-huge version
1823 * pointing to the pte here (which of course we could
1824 * if all CPUs were bug free), userland could trigger
1825 * a small page size TLB miss on the small sized TLB
1826 * while the hugepage TLB entry is still established
1827 * in the huge TLB. Some CPU doesn't like that. See
1828 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1829 * Erratum 383 on page 93. Intel should be safe but is
1830 * also warns that it's only safe if the permission
1831 * and cache attributes of the two entries loaded in
1832 * the two TLB is identical (which should be the case
1833 * here). But it is generally safer to never allow
1834 * small and huge TLB entries for the same virtual
1835 * address to be loaded simultaneously. So instead of
1836 * doing "pmd_populate(); flush_tlb_range();" we first
1837 * mark the current pmd notpresent (atomically because
1838 * here the pmd_trans_huge and pmd_trans_splitting
1839 * must remain set at all times on the pmd until the
1840 * split is complete for this pmd), then we flush the
1841 * SMP TLB and finally we write the non-huge version
1842 * of the pmd entry with pmd_populate.
1844 pmdp_invalidate(vma, address, pmd);
1845 pmd_populate(mm, pmd, pgtable);
1853 /* must be called with anon_vma->root->rwsem held */
1854 static void __split_huge_page(struct page *page,
1855 struct anon_vma *anon_vma,
1856 struct list_head *list)
1858 int mapcount, mapcount2;
1859 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1860 struct anon_vma_chain *avc;
1862 BUG_ON(!PageHead(page));
1863 BUG_ON(PageTail(page));
1866 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1867 struct vm_area_struct *vma = avc->vma;
1868 unsigned long addr = vma_address(page, vma);
1869 BUG_ON(is_vma_temporary_stack(vma));
1870 mapcount += __split_huge_page_splitting(page, vma, addr);
1873 * It is critical that new vmas are added to the tail of the
1874 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1875 * and establishes a child pmd before
1876 * __split_huge_page_splitting() freezes the parent pmd (so if
1877 * we fail to prevent copy_huge_pmd() from running until the
1878 * whole __split_huge_page() is complete), we will still see
1879 * the newly established pmd of the child later during the
1880 * walk, to be able to set it as pmd_trans_splitting too.
1882 if (mapcount != page_mapcount(page)) {
1883 pr_err("mapcount %d page_mapcount %d\n",
1884 mapcount, page_mapcount(page));
1888 __split_huge_page_refcount(page, list);
1891 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1892 struct vm_area_struct *vma = avc->vma;
1893 unsigned long addr = vma_address(page, vma);
1894 BUG_ON(is_vma_temporary_stack(vma));
1895 mapcount2 += __split_huge_page_map(page, vma, addr);
1897 if (mapcount != mapcount2) {
1898 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n",
1899 mapcount, mapcount2, page_mapcount(page));
1905 * Split a hugepage into normal pages. This doesn't change the position of head
1906 * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1907 * @list. Both head page and tail pages will inherit mapping, flags, and so on
1908 * from the hugepage.
1909 * Return 0 if the hugepage is split successfully otherwise return 1.
1911 int split_huge_page_to_list(struct page *page, struct list_head *list)
1913 struct anon_vma *anon_vma;
1916 BUG_ON(is_huge_zero_page(page));
1917 BUG_ON(!PageAnon(page));
1920 * The caller does not necessarily hold an mmap_sem that would prevent
1921 * the anon_vma disappearing so we first we take a reference to it
1922 * and then lock the anon_vma for write. This is similar to
1923 * page_lock_anon_vma_read except the write lock is taken to serialise
1924 * against parallel split or collapse operations.
1926 anon_vma = page_get_anon_vma(page);
1929 anon_vma_lock_write(anon_vma);
1932 if (!PageCompound(page))
1935 BUG_ON(!PageSwapBacked(page));
1936 __split_huge_page(page, anon_vma, list);
1937 count_vm_event(THP_SPLIT);
1939 BUG_ON(PageCompound(page));
1941 anon_vma_unlock_write(anon_vma);
1942 put_anon_vma(anon_vma);
1947 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1949 int hugepage_madvise(struct vm_area_struct *vma,
1950 unsigned long *vm_flags, int advice)
1956 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1957 * can't handle this properly after s390_enable_sie, so we simply
1958 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1960 if (mm_has_pgste(vma->vm_mm))
1964 * Be somewhat over-protective like KSM for now!
1966 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1968 *vm_flags &= ~VM_NOHUGEPAGE;
1969 *vm_flags |= VM_HUGEPAGE;
1971 * If the vma become good for khugepaged to scan,
1972 * register it here without waiting a page fault that
1973 * may not happen any time soon.
1975 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1978 case MADV_NOHUGEPAGE:
1980 * Be somewhat over-protective like KSM for now!
1982 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1984 *vm_flags &= ~VM_HUGEPAGE;
1985 *vm_flags |= VM_NOHUGEPAGE;
1987 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1988 * this vma even if we leave the mm registered in khugepaged if
1989 * it got registered before VM_NOHUGEPAGE was set.
1997 static int __init khugepaged_slab_init(void)
1999 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
2000 sizeof(struct mm_slot),
2001 __alignof__(struct mm_slot), 0, NULL);
2008 static void __init khugepaged_slab_exit(void)
2010 kmem_cache_destroy(mm_slot_cache);
2013 static inline struct mm_slot *alloc_mm_slot(void)
2015 if (!mm_slot_cache) /* initialization failed */
2017 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
2020 static inline void free_mm_slot(struct mm_slot *mm_slot)
2022 kmem_cache_free(mm_slot_cache, mm_slot);
2025 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
2027 struct mm_slot *mm_slot;
2029 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
2030 if (mm == mm_slot->mm)
2036 static void insert_to_mm_slots_hash(struct mm_struct *mm,
2037 struct mm_slot *mm_slot)
2040 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
2043 static inline int khugepaged_test_exit(struct mm_struct *mm)
2045 return atomic_read(&mm->mm_users) == 0;
2048 int __khugepaged_enter(struct mm_struct *mm)
2050 struct mm_slot *mm_slot;
2053 mm_slot = alloc_mm_slot();
2057 /* __khugepaged_exit() must not run from under us */
2058 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
2059 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
2060 free_mm_slot(mm_slot);
2064 spin_lock(&khugepaged_mm_lock);
2065 insert_to_mm_slots_hash(mm, mm_slot);
2067 * Insert just behind the scanning cursor, to let the area settle
2070 wakeup = list_empty(&khugepaged_scan.mm_head);
2071 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
2072 spin_unlock(&khugepaged_mm_lock);
2074 atomic_inc(&mm->mm_count);
2076 wake_up_interruptible(&khugepaged_wait);
2081 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
2082 unsigned long vm_flags)
2084 unsigned long hstart, hend;
2087 * Not yet faulted in so we will register later in the
2088 * page fault if needed.
2092 /* khugepaged not yet working on file or special mappings */
2094 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
2095 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2096 hend = vma->vm_end & HPAGE_PMD_MASK;
2098 return khugepaged_enter(vma, vm_flags);
2102 void __khugepaged_exit(struct mm_struct *mm)
2104 struct mm_slot *mm_slot;
2107 spin_lock(&khugepaged_mm_lock);
2108 mm_slot = get_mm_slot(mm);
2109 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2110 hash_del(&mm_slot->hash);
2111 list_del(&mm_slot->mm_node);
2114 spin_unlock(&khugepaged_mm_lock);
2117 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2118 free_mm_slot(mm_slot);
2120 } else if (mm_slot) {
2122 * This is required to serialize against
2123 * khugepaged_test_exit() (which is guaranteed to run
2124 * under mmap sem read mode). Stop here (after we
2125 * return all pagetables will be destroyed) until
2126 * khugepaged has finished working on the pagetables
2127 * under the mmap_sem.
2129 down_write(&mm->mmap_sem);
2130 up_write(&mm->mmap_sem);
2134 static void release_pte_page(struct page *page)
2136 /* 0 stands for page_is_file_cache(page) == false */
2137 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2139 putback_lru_page(page);
2142 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2144 while (--_pte >= pte) {
2145 pte_t pteval = *_pte;
2146 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2147 release_pte_page(pte_page(pteval));
2151 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2152 unsigned long address,
2157 int none_or_zero = 0;
2158 bool referenced = false, writable = false;
2159 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2160 _pte++, address += PAGE_SIZE) {
2161 pte_t pteval = *_pte;
2162 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2163 if (!userfaultfd_armed(vma) &&
2164 ++none_or_zero <= khugepaged_max_ptes_none)
2169 if (!pte_present(pteval))
2171 page = vm_normal_page(vma, address, pteval);
2172 if (unlikely(!page))
2175 VM_BUG_ON_PAGE(PageCompound(page), page);
2176 VM_BUG_ON_PAGE(!PageAnon(page), page);
2177 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2180 * We can do it before isolate_lru_page because the
2181 * page can't be freed from under us. NOTE: PG_lock
2182 * is needed to serialize against split_huge_page
2183 * when invoked from the VM.
2185 if (!trylock_page(page))
2189 * cannot use mapcount: can't collapse if there's a gup pin.
2190 * The page must only be referenced by the scanned process
2191 * and page swap cache.
2193 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2197 if (pte_write(pteval)) {
2200 if (PageSwapCache(page) && !reuse_swap_page(page)) {
2205 * Page is not in the swap cache. It can be collapsed
2211 * Isolate the page to avoid collapsing an hugepage
2212 * currently in use by the VM.
2214 if (isolate_lru_page(page)) {
2218 /* 0 stands for page_is_file_cache(page) == false */
2219 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2220 VM_BUG_ON_PAGE(!PageLocked(page), page);
2221 VM_BUG_ON_PAGE(PageLRU(page), page);
2223 /* If there is no mapped pte young don't collapse the page */
2224 if (pte_young(pteval) || PageReferenced(page) ||
2225 mmu_notifier_test_young(vma->vm_mm, address))
2228 if (likely(referenced && writable))
2231 release_pte_pages(pte, _pte);
2235 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2236 struct vm_area_struct *vma,
2237 unsigned long address,
2241 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2242 pte_t pteval = *_pte;
2243 struct page *src_page;
2245 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2246 clear_user_highpage(page, address);
2247 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2248 if (is_zero_pfn(pte_pfn(pteval))) {
2250 * ptl mostly unnecessary.
2254 * paravirt calls inside pte_clear here are
2257 pte_clear(vma->vm_mm, address, _pte);
2261 src_page = pte_page(pteval);
2262 copy_user_highpage(page, src_page, address, vma);
2263 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2264 release_pte_page(src_page);
2266 * ptl mostly unnecessary, but preempt has to
2267 * be disabled to update the per-cpu stats
2268 * inside page_remove_rmap().
2272 * paravirt calls inside pte_clear here are
2275 pte_clear(vma->vm_mm, address, _pte);
2276 page_remove_rmap(src_page);
2278 free_page_and_swap_cache(src_page);
2281 address += PAGE_SIZE;
2286 static void khugepaged_alloc_sleep(void)
2288 wait_event_freezable_timeout(khugepaged_wait, false,
2289 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2292 static int khugepaged_node_load[MAX_NUMNODES];
2294 static bool khugepaged_scan_abort(int nid)
2299 * If zone_reclaim_mode is disabled, then no extra effort is made to
2300 * allocate memory locally.
2302 if (!zone_reclaim_mode)
2305 /* If there is a count for this node already, it must be acceptable */
2306 if (khugepaged_node_load[nid])
2309 for (i = 0; i < MAX_NUMNODES; i++) {
2310 if (!khugepaged_node_load[i])
2312 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2319 static int khugepaged_find_target_node(void)
2321 static int last_khugepaged_target_node = NUMA_NO_NODE;
2322 int nid, target_node = 0, max_value = 0;
2324 /* find first node with max normal pages hit */
2325 for (nid = 0; nid < MAX_NUMNODES; nid++)
2326 if (khugepaged_node_load[nid] > max_value) {
2327 max_value = khugepaged_node_load[nid];
2331 /* do some balance if several nodes have the same hit record */
2332 if (target_node <= last_khugepaged_target_node)
2333 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2335 if (max_value == khugepaged_node_load[nid]) {
2340 last_khugepaged_target_node = target_node;
2344 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2346 if (IS_ERR(*hpage)) {
2352 khugepaged_alloc_sleep();
2353 } else if (*hpage) {
2361 static struct page *
2362 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2363 struct vm_area_struct *vma, unsigned long address,
2366 VM_BUG_ON_PAGE(*hpage, *hpage);
2369 * Before allocating the hugepage, release the mmap_sem read lock.
2370 * The allocation can take potentially a long time if it involves
2371 * sync compaction, and we do not need to hold the mmap_sem during
2372 * that. We will recheck the vma after taking it again in write mode.
2374 up_read(&mm->mmap_sem);
2376 *hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER);
2377 if (unlikely(!*hpage)) {
2378 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2379 *hpage = ERR_PTR(-ENOMEM);
2383 count_vm_event(THP_COLLAPSE_ALLOC);
2387 static int khugepaged_find_target_node(void)
2392 static inline struct page *alloc_hugepage(int defrag)
2394 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
2398 static struct page *khugepaged_alloc_hugepage(bool *wait)
2403 hpage = alloc_hugepage(khugepaged_defrag());
2405 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2410 khugepaged_alloc_sleep();
2412 count_vm_event(THP_COLLAPSE_ALLOC);
2413 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2418 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2421 *hpage = khugepaged_alloc_hugepage(wait);
2423 if (unlikely(!*hpage))
2429 static struct page *
2430 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2431 struct vm_area_struct *vma, unsigned long address,
2434 up_read(&mm->mmap_sem);
2441 static bool hugepage_vma_check(struct vm_area_struct *vma)
2443 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2444 (vma->vm_flags & VM_NOHUGEPAGE))
2447 if (!vma->anon_vma || vma->vm_ops)
2449 if (is_vma_temporary_stack(vma))
2451 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2455 static void collapse_huge_page(struct mm_struct *mm,
2456 unsigned long address,
2457 struct page **hpage,
2458 struct vm_area_struct *vma,
2464 struct page *new_page;
2465 spinlock_t *pmd_ptl, *pte_ptl;
2467 unsigned long hstart, hend;
2468 struct mem_cgroup *memcg;
2469 unsigned long mmun_start; /* For mmu_notifiers */
2470 unsigned long mmun_end; /* For mmu_notifiers */
2473 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2475 /* Only allocate from the target node */
2476 gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2479 /* release the mmap_sem read lock. */
2480 new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node);
2484 if (unlikely(mem_cgroup_try_charge(new_page, mm,
2489 * Prevent all access to pagetables with the exception of
2490 * gup_fast later hanlded by the ptep_clear_flush and the VM
2491 * handled by the anon_vma lock + PG_lock.
2493 down_write(&mm->mmap_sem);
2494 if (unlikely(khugepaged_test_exit(mm)))
2497 vma = find_vma(mm, address);
2500 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2501 hend = vma->vm_end & HPAGE_PMD_MASK;
2502 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2504 if (!hugepage_vma_check(vma))
2506 pmd = mm_find_pmd(mm, address);
2510 anon_vma_lock_write(vma->anon_vma);
2512 pte = pte_offset_map(pmd, address);
2513 pte_ptl = pte_lockptr(mm, pmd);
2515 mmun_start = address;
2516 mmun_end = address + HPAGE_PMD_SIZE;
2517 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2518 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2520 * After this gup_fast can't run anymore. This also removes
2521 * any huge TLB entry from the CPU so we won't allow
2522 * huge and small TLB entries for the same virtual address
2523 * to avoid the risk of CPU bugs in that area.
2525 _pmd = pmdp_collapse_flush(vma, address, pmd);
2526 spin_unlock(pmd_ptl);
2527 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2530 isolated = __collapse_huge_page_isolate(vma, address, pte);
2531 spin_unlock(pte_ptl);
2533 if (unlikely(!isolated)) {
2536 BUG_ON(!pmd_none(*pmd));
2538 * We can only use set_pmd_at when establishing
2539 * hugepmds and never for establishing regular pmds that
2540 * points to regular pagetables. Use pmd_populate for that
2542 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2543 spin_unlock(pmd_ptl);
2544 anon_vma_unlock_write(vma->anon_vma);
2549 * All pages are isolated and locked so anon_vma rmap
2550 * can't run anymore.
2552 anon_vma_unlock_write(vma->anon_vma);
2554 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2556 __SetPageUptodate(new_page);
2557 pgtable = pmd_pgtable(_pmd);
2559 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2560 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2563 * spin_lock() below is not the equivalent of smp_wmb(), so
2564 * this is needed to avoid the copy_huge_page writes to become
2565 * visible after the set_pmd_at() write.
2570 BUG_ON(!pmd_none(*pmd));
2571 page_add_new_anon_rmap(new_page, vma, address);
2572 mem_cgroup_commit_charge(new_page, memcg, false);
2573 lru_cache_add_active_or_unevictable(new_page, vma);
2574 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2575 set_pmd_at(mm, address, pmd, _pmd);
2576 update_mmu_cache_pmd(vma, address, pmd);
2577 spin_unlock(pmd_ptl);
2581 khugepaged_pages_collapsed++;
2583 up_write(&mm->mmap_sem);
2587 mem_cgroup_cancel_charge(new_page, memcg);
2591 static int khugepaged_scan_pmd(struct mm_struct *mm,
2592 struct vm_area_struct *vma,
2593 unsigned long address,
2594 struct page **hpage)
2598 int ret = 0, none_or_zero = 0;
2600 unsigned long _address;
2602 int node = NUMA_NO_NODE;
2603 bool writable = false, referenced = false;
2605 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2607 pmd = mm_find_pmd(mm, address);
2611 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2612 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2613 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2614 _pte++, _address += PAGE_SIZE) {
2615 pte_t pteval = *_pte;
2616 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2617 if (!userfaultfd_armed(vma) &&
2618 ++none_or_zero <= khugepaged_max_ptes_none)
2623 if (!pte_present(pteval))
2625 if (pte_write(pteval))
2628 page = vm_normal_page(vma, _address, pteval);
2629 if (unlikely(!page))
2632 * Record which node the original page is from and save this
2633 * information to khugepaged_node_load[].
2634 * Khupaged will allocate hugepage from the node has the max
2637 node = page_to_nid(page);
2638 if (khugepaged_scan_abort(node))
2640 khugepaged_node_load[node]++;
2641 VM_BUG_ON_PAGE(PageCompound(page), page);
2642 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2645 * cannot use mapcount: can't collapse if there's a gup pin.
2646 * The page must only be referenced by the scanned process
2647 * and page swap cache.
2649 if (page_count(page) != 1 + !!PageSwapCache(page))
2651 if (pte_young(pteval) || PageReferenced(page) ||
2652 mmu_notifier_test_young(vma->vm_mm, address))
2655 if (referenced && writable)
2658 pte_unmap_unlock(pte, ptl);
2660 node = khugepaged_find_target_node();
2661 /* collapse_huge_page will return with the mmap_sem released */
2662 collapse_huge_page(mm, address, hpage, vma, node);
2668 static void collect_mm_slot(struct mm_slot *mm_slot)
2670 struct mm_struct *mm = mm_slot->mm;
2672 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2674 if (khugepaged_test_exit(mm)) {
2676 hash_del(&mm_slot->hash);
2677 list_del(&mm_slot->mm_node);
2680 * Not strictly needed because the mm exited already.
2682 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2685 /* khugepaged_mm_lock actually not necessary for the below */
2686 free_mm_slot(mm_slot);
2691 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2692 struct page **hpage)
2693 __releases(&khugepaged_mm_lock)
2694 __acquires(&khugepaged_mm_lock)
2696 struct mm_slot *mm_slot;
2697 struct mm_struct *mm;
2698 struct vm_area_struct *vma;
2702 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2704 if (khugepaged_scan.mm_slot)
2705 mm_slot = khugepaged_scan.mm_slot;
2707 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2708 struct mm_slot, mm_node);
2709 khugepaged_scan.address = 0;
2710 khugepaged_scan.mm_slot = mm_slot;
2712 spin_unlock(&khugepaged_mm_lock);
2715 down_read(&mm->mmap_sem);
2716 if (unlikely(khugepaged_test_exit(mm)))
2719 vma = find_vma(mm, khugepaged_scan.address);
2722 for (; vma; vma = vma->vm_next) {
2723 unsigned long hstart, hend;
2726 if (unlikely(khugepaged_test_exit(mm))) {
2730 if (!hugepage_vma_check(vma)) {
2735 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2736 hend = vma->vm_end & HPAGE_PMD_MASK;
2739 if (khugepaged_scan.address > hend)
2741 if (khugepaged_scan.address < hstart)
2742 khugepaged_scan.address = hstart;
2743 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2745 while (khugepaged_scan.address < hend) {
2748 if (unlikely(khugepaged_test_exit(mm)))
2749 goto breakouterloop;
2751 VM_BUG_ON(khugepaged_scan.address < hstart ||
2752 khugepaged_scan.address + HPAGE_PMD_SIZE >
2754 ret = khugepaged_scan_pmd(mm, vma,
2755 khugepaged_scan.address,
2757 /* move to next address */
2758 khugepaged_scan.address += HPAGE_PMD_SIZE;
2759 progress += HPAGE_PMD_NR;
2761 /* we released mmap_sem so break loop */
2762 goto breakouterloop_mmap_sem;
2763 if (progress >= pages)
2764 goto breakouterloop;
2768 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2769 breakouterloop_mmap_sem:
2771 spin_lock(&khugepaged_mm_lock);
2772 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2774 * Release the current mm_slot if this mm is about to die, or
2775 * if we scanned all vmas of this mm.
2777 if (khugepaged_test_exit(mm) || !vma) {
2779 * Make sure that if mm_users is reaching zero while
2780 * khugepaged runs here, khugepaged_exit will find
2781 * mm_slot not pointing to the exiting mm.
2783 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2784 khugepaged_scan.mm_slot = list_entry(
2785 mm_slot->mm_node.next,
2786 struct mm_slot, mm_node);
2787 khugepaged_scan.address = 0;
2789 khugepaged_scan.mm_slot = NULL;
2790 khugepaged_full_scans++;
2793 collect_mm_slot(mm_slot);
2799 static int khugepaged_has_work(void)
2801 return !list_empty(&khugepaged_scan.mm_head) &&
2802 khugepaged_enabled();
2805 static int khugepaged_wait_event(void)
2807 return !list_empty(&khugepaged_scan.mm_head) ||
2808 kthread_should_stop();
2811 static void khugepaged_do_scan(void)
2813 struct page *hpage = NULL;
2814 unsigned int progress = 0, pass_through_head = 0;
2815 unsigned int pages = khugepaged_pages_to_scan;
2818 barrier(); /* write khugepaged_pages_to_scan to local stack */
2820 while (progress < pages) {
2821 if (!khugepaged_prealloc_page(&hpage, &wait))
2826 if (unlikely(kthread_should_stop() || try_to_freeze()))
2829 spin_lock(&khugepaged_mm_lock);
2830 if (!khugepaged_scan.mm_slot)
2831 pass_through_head++;
2832 if (khugepaged_has_work() &&
2833 pass_through_head < 2)
2834 progress += khugepaged_scan_mm_slot(pages - progress,
2838 spin_unlock(&khugepaged_mm_lock);
2841 if (!IS_ERR_OR_NULL(hpage))
2845 static void khugepaged_wait_work(void)
2847 if (khugepaged_has_work()) {
2848 if (!khugepaged_scan_sleep_millisecs)
2851 wait_event_freezable_timeout(khugepaged_wait,
2852 kthread_should_stop(),
2853 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2857 if (khugepaged_enabled())
2858 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2861 static int khugepaged(void *none)
2863 struct mm_slot *mm_slot;
2866 set_user_nice(current, MAX_NICE);
2868 while (!kthread_should_stop()) {
2869 khugepaged_do_scan();
2870 khugepaged_wait_work();
2873 spin_lock(&khugepaged_mm_lock);
2874 mm_slot = khugepaged_scan.mm_slot;
2875 khugepaged_scan.mm_slot = NULL;
2877 collect_mm_slot(mm_slot);
2878 spin_unlock(&khugepaged_mm_lock);
2882 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2883 unsigned long haddr, pmd_t *pmd)
2885 struct mm_struct *mm = vma->vm_mm;
2890 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2891 /* leave pmd empty until pte is filled */
2893 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2894 pmd_populate(mm, &_pmd, pgtable);
2896 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2898 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2899 entry = pte_mkspecial(entry);
2900 pte = pte_offset_map(&_pmd, haddr);
2901 VM_BUG_ON(!pte_none(*pte));
2902 set_pte_at(mm, haddr, pte, entry);
2905 smp_wmb(); /* make pte visible before pmd */
2906 pmd_populate(mm, pmd, pgtable);
2907 put_huge_zero_page();
2910 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2915 struct mm_struct *mm = vma->vm_mm;
2916 unsigned long haddr = address & HPAGE_PMD_MASK;
2917 unsigned long mmun_start; /* For mmu_notifiers */
2918 unsigned long mmun_end; /* For mmu_notifiers */
2920 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2923 mmun_end = haddr + HPAGE_PMD_SIZE;
2925 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2926 ptl = pmd_lock(mm, pmd);
2927 if (unlikely(!pmd_trans_huge(*pmd))) {
2929 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2932 if (is_huge_zero_pmd(*pmd)) {
2933 __split_huge_zero_page_pmd(vma, haddr, pmd);
2935 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2938 page = pmd_page(*pmd);
2939 VM_BUG_ON_PAGE(!page_count(page), page);
2942 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2944 split_huge_page(page);
2949 * We don't always have down_write of mmap_sem here: a racing
2950 * do_huge_pmd_wp_page() might have copied-on-write to another
2951 * huge page before our split_huge_page() got the anon_vma lock.
2953 if (unlikely(pmd_trans_huge(*pmd)))
2957 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2960 struct vm_area_struct *vma;
2962 vma = find_vma(mm, address);
2963 BUG_ON(vma == NULL);
2964 split_huge_page_pmd(vma, address, pmd);
2967 static void split_huge_page_address(struct mm_struct *mm,
2968 unsigned long address)
2974 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2976 pgd = pgd_offset(mm, address);
2977 if (!pgd_present(*pgd))
2980 pud = pud_offset(pgd, address);
2981 if (!pud_present(*pud))
2984 pmd = pmd_offset(pud, address);
2985 if (!pmd_present(*pmd))
2988 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2989 * materialize from under us.
2991 split_huge_page_pmd_mm(mm, address, pmd);
2994 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2995 unsigned long start,
3000 * If the new start address isn't hpage aligned and it could
3001 * previously contain an hugepage: check if we need to split
3004 if (start & ~HPAGE_PMD_MASK &&
3005 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3006 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3007 split_huge_page_address(vma->vm_mm, start);
3010 * If the new end address isn't hpage aligned and it could
3011 * previously contain an hugepage: check if we need to split
3014 if (end & ~HPAGE_PMD_MASK &&
3015 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3016 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3017 split_huge_page_address(vma->vm_mm, end);
3020 * If we're also updating the vma->vm_next->vm_start, if the new
3021 * vm_next->vm_start isn't page aligned and it could previously
3022 * contain an hugepage: check if we need to split an huge pmd.
3024 if (adjust_next > 0) {
3025 struct vm_area_struct *next = vma->vm_next;
3026 unsigned long nstart = next->vm_start;
3027 nstart += adjust_next << PAGE_SHIFT;
3028 if (nstart & ~HPAGE_PMD_MASK &&
3029 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3030 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3031 split_huge_page_address(next->vm_mm, nstart);