2 * Copyright (C) 2009 Red Hat, Inc.
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/sched.h>
12 #include <linux/highmem.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mmu_notifier.h>
15 #include <linux/rmap.h>
16 #include <linux/swap.h>
17 #include <linux/shrinker.h>
18 #include <linux/mm_inline.h>
19 #include <linux/swapops.h>
20 #include <linux/dax.h>
21 #include <linux/kthread.h>
22 #include <linux/khugepaged.h>
23 #include <linux/freezer.h>
24 #include <linux/pfn_t.h>
25 #include <linux/mman.h>
26 #include <linux/memremap.h>
27 #include <linux/pagemap.h>
28 #include <linux/debugfs.h>
29 #include <linux/migrate.h>
30 #include <linux/hashtable.h>
31 #include <linux/userfaultfd_k.h>
32 #include <linux/page_idle.h>
33 #include <linux/shmem_fs.h>
36 #include <asm/pgalloc.h>
46 SCAN_NO_REFERENCED_PAGE,
60 SCAN_ALLOC_HUGE_PAGE_FAIL,
61 SCAN_CGROUP_CHARGE_FAIL,
65 #define CREATE_TRACE_POINTS
66 #include <trace/events/huge_memory.h>
69 * By default transparent hugepage support is disabled in order that avoid
70 * to risk increase the memory footprint of applications without a guaranteed
71 * benefit. When transparent hugepage support is enabled, is for all mappings,
72 * and khugepaged scans all mappings.
73 * Defrag is invoked by khugepaged hugepage allocations and by page faults
74 * for all hugepage allocations.
76 unsigned long transparent_hugepage_flags __read_mostly =
77 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
78 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
80 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
81 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
83 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
84 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
85 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
87 /* default scan 8*512 pte (or vmas) every 30 second */
88 static unsigned int khugepaged_pages_to_scan __read_mostly;
89 static unsigned int khugepaged_pages_collapsed;
90 static unsigned int khugepaged_full_scans;
91 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
92 /* during fragmentation poll the hugepage allocator once every minute */
93 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
94 static unsigned long khugepaged_sleep_expire;
95 static struct task_struct *khugepaged_thread __read_mostly;
96 static DEFINE_MUTEX(khugepaged_mutex);
97 static DEFINE_SPINLOCK(khugepaged_mm_lock);
98 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
100 * default collapse hugepages if there is at least one pte mapped like
101 * it would have happened if the vma was large enough during page
104 static unsigned int khugepaged_max_ptes_none __read_mostly;
105 static unsigned int khugepaged_max_ptes_swap __read_mostly;
107 static int khugepaged(void *none);
108 static int khugepaged_slab_init(void);
109 static void khugepaged_slab_exit(void);
111 #define MM_SLOTS_HASH_BITS 10
112 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
114 static struct kmem_cache *mm_slot_cache __read_mostly;
117 * struct mm_slot - hash lookup from mm to mm_slot
118 * @hash: hash collision list
119 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
120 * @mm: the mm that this information is valid for
123 struct hlist_node hash;
124 struct list_head mm_node;
125 struct mm_struct *mm;
129 * struct khugepaged_scan - cursor for scanning
130 * @mm_head: the head of the mm list to scan
131 * @mm_slot: the current mm_slot we are scanning
132 * @address: the next address inside that to be scanned
134 * There is only the one khugepaged_scan instance of this cursor structure.
136 struct khugepaged_scan {
137 struct list_head mm_head;
138 struct mm_slot *mm_slot;
139 unsigned long address;
141 static struct khugepaged_scan khugepaged_scan = {
142 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
145 static struct shrinker deferred_split_shrinker;
147 static void set_recommended_min_free_kbytes(void)
151 unsigned long recommended_min;
153 for_each_populated_zone(zone)
156 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
157 recommended_min = pageblock_nr_pages * nr_zones * 2;
160 * Make sure that on average at least two pageblocks are almost free
161 * of another type, one for a migratetype to fall back to and a
162 * second to avoid subsequent fallbacks of other types There are 3
163 * MIGRATE_TYPES we care about.
165 recommended_min += pageblock_nr_pages * nr_zones *
166 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
168 /* don't ever allow to reserve more than 5% of the lowmem */
169 recommended_min = min(recommended_min,
170 (unsigned long) nr_free_buffer_pages() / 20);
171 recommended_min <<= (PAGE_SHIFT-10);
173 if (recommended_min > min_free_kbytes) {
174 if (user_min_free_kbytes >= 0)
175 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
176 min_free_kbytes, recommended_min);
178 min_free_kbytes = recommended_min;
180 setup_per_zone_wmarks();
183 static int start_stop_khugepaged(void)
186 if (khugepaged_enabled()) {
187 if (!khugepaged_thread)
188 khugepaged_thread = kthread_run(khugepaged, NULL,
190 if (IS_ERR(khugepaged_thread)) {
191 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
192 err = PTR_ERR(khugepaged_thread);
193 khugepaged_thread = NULL;
197 if (!list_empty(&khugepaged_scan.mm_head))
198 wake_up_interruptible(&khugepaged_wait);
200 set_recommended_min_free_kbytes();
201 } else if (khugepaged_thread) {
202 kthread_stop(khugepaged_thread);
203 khugepaged_thread = NULL;
209 static atomic_t huge_zero_refcount;
210 struct page *huge_zero_page __read_mostly;
212 struct page *get_huge_zero_page(void)
214 struct page *zero_page;
216 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
217 return READ_ONCE(huge_zero_page);
219 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
222 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
225 count_vm_event(THP_ZERO_PAGE_ALLOC);
227 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
229 __free_pages(zero_page, compound_order(zero_page));
233 /* We take additional reference here. It will be put back by shrinker */
234 atomic_set(&huge_zero_refcount, 2);
236 return READ_ONCE(huge_zero_page);
239 void put_huge_zero_page(void)
242 * Counter should never go to zero here. Only shrinker can put
245 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
248 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
249 struct shrink_control *sc)
251 /* we can free zero page only if last reference remains */
252 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
255 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
256 struct shrink_control *sc)
258 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
259 struct page *zero_page = xchg(&huge_zero_page, NULL);
260 BUG_ON(zero_page == NULL);
261 __free_pages(zero_page, compound_order(zero_page));
268 static struct shrinker huge_zero_page_shrinker = {
269 .count_objects = shrink_huge_zero_page_count,
270 .scan_objects = shrink_huge_zero_page_scan,
271 .seeks = DEFAULT_SEEKS,
276 static ssize_t triple_flag_store(struct kobject *kobj,
277 struct kobj_attribute *attr,
278 const char *buf, size_t count,
279 enum transparent_hugepage_flag enabled,
280 enum transparent_hugepage_flag deferred,
281 enum transparent_hugepage_flag req_madv)
283 if (!memcmp("defer", buf,
284 min(sizeof("defer")-1, count))) {
285 if (enabled == deferred)
287 clear_bit(enabled, &transparent_hugepage_flags);
288 clear_bit(req_madv, &transparent_hugepage_flags);
289 set_bit(deferred, &transparent_hugepage_flags);
290 } else if (!memcmp("always", buf,
291 min(sizeof("always")-1, count))) {
292 clear_bit(deferred, &transparent_hugepage_flags);
293 clear_bit(req_madv, &transparent_hugepage_flags);
294 set_bit(enabled, &transparent_hugepage_flags);
295 } else if (!memcmp("madvise", buf,
296 min(sizeof("madvise")-1, count))) {
297 clear_bit(enabled, &transparent_hugepage_flags);
298 clear_bit(deferred, &transparent_hugepage_flags);
299 set_bit(req_madv, &transparent_hugepage_flags);
300 } else if (!memcmp("never", buf,
301 min(sizeof("never")-1, count))) {
302 clear_bit(enabled, &transparent_hugepage_flags);
303 clear_bit(req_madv, &transparent_hugepage_flags);
304 clear_bit(deferred, &transparent_hugepage_flags);
311 static ssize_t enabled_show(struct kobject *kobj,
312 struct kobj_attribute *attr, char *buf)
314 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
315 return sprintf(buf, "[always] madvise never\n");
316 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
317 return sprintf(buf, "always [madvise] never\n");
319 return sprintf(buf, "always madvise [never]\n");
322 static ssize_t enabled_store(struct kobject *kobj,
323 struct kobj_attribute *attr,
324 const char *buf, size_t count)
328 ret = triple_flag_store(kobj, attr, buf, count,
329 TRANSPARENT_HUGEPAGE_FLAG,
330 TRANSPARENT_HUGEPAGE_FLAG,
331 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
336 mutex_lock(&khugepaged_mutex);
337 err = start_stop_khugepaged();
338 mutex_unlock(&khugepaged_mutex);
346 static struct kobj_attribute enabled_attr =
347 __ATTR(enabled, 0644, enabled_show, enabled_store);
349 static ssize_t single_flag_show(struct kobject *kobj,
350 struct kobj_attribute *attr, char *buf,
351 enum transparent_hugepage_flag flag)
353 return sprintf(buf, "%d\n",
354 !!test_bit(flag, &transparent_hugepage_flags));
357 static ssize_t single_flag_store(struct kobject *kobj,
358 struct kobj_attribute *attr,
359 const char *buf, size_t count,
360 enum transparent_hugepage_flag flag)
365 ret = kstrtoul(buf, 10, &value);
372 set_bit(flag, &transparent_hugepage_flags);
374 clear_bit(flag, &transparent_hugepage_flags);
380 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
381 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
382 * memory just to allocate one more hugepage.
384 static ssize_t defrag_show(struct kobject *kobj,
385 struct kobj_attribute *attr, char *buf)
387 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
388 return sprintf(buf, "[always] defer madvise never\n");
389 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
390 return sprintf(buf, "always [defer] madvise never\n");
391 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
392 return sprintf(buf, "always defer [madvise] never\n");
394 return sprintf(buf, "always defer madvise [never]\n");
397 static ssize_t defrag_store(struct kobject *kobj,
398 struct kobj_attribute *attr,
399 const char *buf, size_t count)
401 return triple_flag_store(kobj, attr, buf, count,
402 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
403 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
404 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
406 static struct kobj_attribute defrag_attr =
407 __ATTR(defrag, 0644, defrag_show, defrag_store);
409 static ssize_t use_zero_page_show(struct kobject *kobj,
410 struct kobj_attribute *attr, char *buf)
412 return single_flag_show(kobj, attr, buf,
413 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
415 static ssize_t use_zero_page_store(struct kobject *kobj,
416 struct kobj_attribute *attr, const char *buf, size_t count)
418 return single_flag_store(kobj, attr, buf, count,
419 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
421 static struct kobj_attribute use_zero_page_attr =
422 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
423 #ifdef CONFIG_DEBUG_VM
424 static ssize_t debug_cow_show(struct kobject *kobj,
425 struct kobj_attribute *attr, char *buf)
427 return single_flag_show(kobj, attr, buf,
428 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
430 static ssize_t debug_cow_store(struct kobject *kobj,
431 struct kobj_attribute *attr,
432 const char *buf, size_t count)
434 return single_flag_store(kobj, attr, buf, count,
435 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
437 static struct kobj_attribute debug_cow_attr =
438 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
439 #endif /* CONFIG_DEBUG_VM */
441 static struct attribute *hugepage_attr[] = {
444 &use_zero_page_attr.attr,
445 #ifdef CONFIG_DEBUG_VM
446 &debug_cow_attr.attr,
451 static struct attribute_group hugepage_attr_group = {
452 .attrs = hugepage_attr,
455 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
456 struct kobj_attribute *attr,
459 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
462 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
463 struct kobj_attribute *attr,
464 const char *buf, size_t count)
469 err = kstrtoul(buf, 10, &msecs);
470 if (err || msecs > UINT_MAX)
473 khugepaged_scan_sleep_millisecs = msecs;
474 khugepaged_sleep_expire = 0;
475 wake_up_interruptible(&khugepaged_wait);
479 static struct kobj_attribute scan_sleep_millisecs_attr =
480 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
481 scan_sleep_millisecs_store);
483 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
484 struct kobj_attribute *attr,
487 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
490 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
491 struct kobj_attribute *attr,
492 const char *buf, size_t count)
497 err = kstrtoul(buf, 10, &msecs);
498 if (err || msecs > UINT_MAX)
501 khugepaged_alloc_sleep_millisecs = msecs;
502 khugepaged_sleep_expire = 0;
503 wake_up_interruptible(&khugepaged_wait);
507 static struct kobj_attribute alloc_sleep_millisecs_attr =
508 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
509 alloc_sleep_millisecs_store);
511 static ssize_t pages_to_scan_show(struct kobject *kobj,
512 struct kobj_attribute *attr,
515 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
517 static ssize_t pages_to_scan_store(struct kobject *kobj,
518 struct kobj_attribute *attr,
519 const char *buf, size_t count)
524 err = kstrtoul(buf, 10, &pages);
525 if (err || !pages || pages > UINT_MAX)
528 khugepaged_pages_to_scan = pages;
532 static struct kobj_attribute pages_to_scan_attr =
533 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
534 pages_to_scan_store);
536 static ssize_t pages_collapsed_show(struct kobject *kobj,
537 struct kobj_attribute *attr,
540 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
542 static struct kobj_attribute pages_collapsed_attr =
543 __ATTR_RO(pages_collapsed);
545 static ssize_t full_scans_show(struct kobject *kobj,
546 struct kobj_attribute *attr,
549 return sprintf(buf, "%u\n", khugepaged_full_scans);
551 static struct kobj_attribute full_scans_attr =
552 __ATTR_RO(full_scans);
554 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
555 struct kobj_attribute *attr, char *buf)
557 return single_flag_show(kobj, attr, buf,
558 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
560 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
561 struct kobj_attribute *attr,
562 const char *buf, size_t count)
564 return single_flag_store(kobj, attr, buf, count,
565 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
567 static struct kobj_attribute khugepaged_defrag_attr =
568 __ATTR(defrag, 0644, khugepaged_defrag_show,
569 khugepaged_defrag_store);
572 * max_ptes_none controls if khugepaged should collapse hugepages over
573 * any unmapped ptes in turn potentially increasing the memory
574 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
575 * reduce the available free memory in the system as it
576 * runs. Increasing max_ptes_none will instead potentially reduce the
577 * free memory in the system during the khugepaged scan.
579 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
580 struct kobj_attribute *attr,
583 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
585 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
586 struct kobj_attribute *attr,
587 const char *buf, size_t count)
590 unsigned long max_ptes_none;
592 err = kstrtoul(buf, 10, &max_ptes_none);
593 if (err || max_ptes_none > HPAGE_PMD_NR-1)
596 khugepaged_max_ptes_none = max_ptes_none;
600 static struct kobj_attribute khugepaged_max_ptes_none_attr =
601 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
602 khugepaged_max_ptes_none_store);
604 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
605 struct kobj_attribute *attr,
608 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
611 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
612 struct kobj_attribute *attr,
613 const char *buf, size_t count)
616 unsigned long max_ptes_swap;
618 err = kstrtoul(buf, 10, &max_ptes_swap);
619 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
622 khugepaged_max_ptes_swap = max_ptes_swap;
627 static struct kobj_attribute khugepaged_max_ptes_swap_attr =
628 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
629 khugepaged_max_ptes_swap_store);
631 static struct attribute *khugepaged_attr[] = {
632 &khugepaged_defrag_attr.attr,
633 &khugepaged_max_ptes_none_attr.attr,
634 &pages_to_scan_attr.attr,
635 &pages_collapsed_attr.attr,
636 &full_scans_attr.attr,
637 &scan_sleep_millisecs_attr.attr,
638 &alloc_sleep_millisecs_attr.attr,
639 &khugepaged_max_ptes_swap_attr.attr,
643 static struct attribute_group khugepaged_attr_group = {
644 .attrs = khugepaged_attr,
645 .name = "khugepaged",
648 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
652 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
653 if (unlikely(!*hugepage_kobj)) {
654 pr_err("failed to create transparent hugepage kobject\n");
658 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
660 pr_err("failed to register transparent hugepage group\n");
664 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
666 pr_err("failed to register transparent hugepage group\n");
667 goto remove_hp_group;
673 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
675 kobject_put(*hugepage_kobj);
679 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
681 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
682 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
683 kobject_put(hugepage_kobj);
686 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
691 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
694 #endif /* CONFIG_SYSFS */
696 static int __init hugepage_init(void)
699 struct kobject *hugepage_kobj;
701 if (!has_transparent_hugepage()) {
702 transparent_hugepage_flags = 0;
706 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
707 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
708 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
710 * hugepages can't be allocated by the buddy allocator
712 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
714 * we use page->mapping and page->index in second tail page
715 * as list_head: assuming THP order >= 2
717 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
719 err = hugepage_init_sysfs(&hugepage_kobj);
723 err = khugepaged_slab_init();
727 err = register_shrinker(&huge_zero_page_shrinker);
729 goto err_hzp_shrinker;
730 err = register_shrinker(&deferred_split_shrinker);
732 goto err_split_shrinker;
735 * By default disable transparent hugepages on smaller systems,
736 * where the extra memory used could hurt more than TLB overhead
737 * is likely to save. The admin can still enable it through /sys.
739 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
740 transparent_hugepage_flags = 0;
744 err = start_stop_khugepaged();
750 unregister_shrinker(&deferred_split_shrinker);
752 unregister_shrinker(&huge_zero_page_shrinker);
754 khugepaged_slab_exit();
756 hugepage_exit_sysfs(hugepage_kobj);
760 subsys_initcall(hugepage_init);
762 static int __init setup_transparent_hugepage(char *str)
767 if (!strcmp(str, "always")) {
768 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
769 &transparent_hugepage_flags);
770 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
771 &transparent_hugepage_flags);
773 } else if (!strcmp(str, "madvise")) {
774 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
775 &transparent_hugepage_flags);
776 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
777 &transparent_hugepage_flags);
779 } else if (!strcmp(str, "never")) {
780 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
781 &transparent_hugepage_flags);
782 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
783 &transparent_hugepage_flags);
788 pr_warn("transparent_hugepage= cannot parse, ignored\n");
791 __setup("transparent_hugepage=", setup_transparent_hugepage);
793 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
795 if (likely(vma->vm_flags & VM_WRITE))
796 pmd = pmd_mkwrite(pmd);
800 static inline struct list_head *page_deferred_list(struct page *page)
803 * ->lru in the tail pages is occupied by compound_head.
804 * Let's use ->mapping + ->index in the second tail page as list_head.
806 return (struct list_head *)&page[2].mapping;
809 void prep_transhuge_page(struct page *page)
812 * we use page->mapping and page->indexlru in second tail page
813 * as list_head: assuming THP order >= 2
816 INIT_LIST_HEAD(page_deferred_list(page));
817 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
820 static int __do_huge_pmd_anonymous_page(struct fault_env *fe, struct page *page,
823 struct vm_area_struct *vma = fe->vma;
824 struct mem_cgroup *memcg;
826 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
828 VM_BUG_ON_PAGE(!PageCompound(page), page);
830 if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
832 count_vm_event(THP_FAULT_FALLBACK);
833 return VM_FAULT_FALLBACK;
836 pgtable = pte_alloc_one(vma->vm_mm, haddr);
837 if (unlikely(!pgtable)) {
838 mem_cgroup_cancel_charge(page, memcg, true);
843 clear_huge_page(page, haddr, HPAGE_PMD_NR);
845 * The memory barrier inside __SetPageUptodate makes sure that
846 * clear_huge_page writes become visible before the set_pmd_at()
849 __SetPageUptodate(page);
851 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
852 if (unlikely(!pmd_none(*fe->pmd))) {
853 spin_unlock(fe->ptl);
854 mem_cgroup_cancel_charge(page, memcg, true);
856 pte_free(vma->vm_mm, pgtable);
860 /* Deliver the page fault to userland */
861 if (userfaultfd_missing(vma)) {
864 spin_unlock(fe->ptl);
865 mem_cgroup_cancel_charge(page, memcg, true);
867 pte_free(vma->vm_mm, pgtable);
868 ret = handle_userfault(fe, VM_UFFD_MISSING);
869 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
873 entry = mk_huge_pmd(page, vma->vm_page_prot);
874 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
875 page_add_new_anon_rmap(page, vma, haddr, true);
876 mem_cgroup_commit_charge(page, memcg, false, true);
877 lru_cache_add_active_or_unevictable(page, vma);
878 pgtable_trans_huge_deposit(vma->vm_mm, fe->pmd, pgtable);
879 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
880 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
881 atomic_long_inc(&vma->vm_mm->nr_ptes);
882 spin_unlock(fe->ptl);
883 count_vm_event(THP_FAULT_ALLOC);
890 * If THP is set to always then directly reclaim/compact as necessary
891 * If set to defer then do no reclaim and defer to khugepaged
892 * If set to madvise and the VMA is flagged then directly reclaim/compact
894 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
896 gfp_t reclaim_flags = 0;
898 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags) &&
899 (vma->vm_flags & VM_HUGEPAGE))
900 reclaim_flags = __GFP_DIRECT_RECLAIM;
901 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
902 reclaim_flags = __GFP_KSWAPD_RECLAIM;
903 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
904 reclaim_flags = __GFP_DIRECT_RECLAIM;
906 return GFP_TRANSHUGE | reclaim_flags;
909 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
910 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
912 return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0);
915 /* Caller must hold page table lock. */
916 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
917 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
918 struct page *zero_page)
923 entry = mk_pmd(zero_page, vma->vm_page_prot);
924 entry = pmd_mkhuge(entry);
926 pgtable_trans_huge_deposit(mm, pmd, pgtable);
927 set_pmd_at(mm, haddr, pmd, entry);
928 atomic_long_inc(&mm->nr_ptes);
932 int do_huge_pmd_anonymous_page(struct fault_env *fe)
934 struct vm_area_struct *vma = fe->vma;
937 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
939 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
940 return VM_FAULT_FALLBACK;
941 if (unlikely(anon_vma_prepare(vma)))
943 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
945 if (!(fe->flags & FAULT_FLAG_WRITE) &&
946 !mm_forbids_zeropage(vma->vm_mm) &&
947 transparent_hugepage_use_zero_page()) {
949 struct page *zero_page;
952 pgtable = pte_alloc_one(vma->vm_mm, haddr);
953 if (unlikely(!pgtable))
955 zero_page = get_huge_zero_page();
956 if (unlikely(!zero_page)) {
957 pte_free(vma->vm_mm, pgtable);
958 count_vm_event(THP_FAULT_FALLBACK);
959 return VM_FAULT_FALLBACK;
961 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
964 if (pmd_none(*fe->pmd)) {
965 if (userfaultfd_missing(vma)) {
966 spin_unlock(fe->ptl);
967 ret = handle_userfault(fe, VM_UFFD_MISSING);
968 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
970 set_huge_zero_page(pgtable, vma->vm_mm, vma,
971 haddr, fe->pmd, zero_page);
972 spin_unlock(fe->ptl);
976 spin_unlock(fe->ptl);
978 pte_free(vma->vm_mm, pgtable);
979 put_huge_zero_page();
983 gfp = alloc_hugepage_direct_gfpmask(vma);
984 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
985 if (unlikely(!page)) {
986 count_vm_event(THP_FAULT_FALLBACK);
987 return VM_FAULT_FALLBACK;
989 prep_transhuge_page(page);
990 return __do_huge_pmd_anonymous_page(fe, page, gfp);
993 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
994 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
996 struct mm_struct *mm = vma->vm_mm;
1000 ptl = pmd_lock(mm, pmd);
1001 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
1002 if (pfn_t_devmap(pfn))
1003 entry = pmd_mkdevmap(entry);
1005 entry = pmd_mkyoung(pmd_mkdirty(entry));
1006 entry = maybe_pmd_mkwrite(entry, vma);
1008 set_pmd_at(mm, addr, pmd, entry);
1009 update_mmu_cache_pmd(vma, addr, pmd);
1013 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
1014 pmd_t *pmd, pfn_t pfn, bool write)
1016 pgprot_t pgprot = vma->vm_page_prot;
1018 * If we had pmd_special, we could avoid all these restrictions,
1019 * but we need to be consistent with PTEs and architectures that
1020 * can't support a 'special' bit.
1022 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1023 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1024 (VM_PFNMAP|VM_MIXEDMAP));
1025 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1026 BUG_ON(!pfn_t_devmap(pfn));
1028 if (addr < vma->vm_start || addr >= vma->vm_end)
1029 return VM_FAULT_SIGBUS;
1030 if (track_pfn_insert(vma, &pgprot, pfn))
1031 return VM_FAULT_SIGBUS;
1032 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
1033 return VM_FAULT_NOPAGE;
1035 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
1037 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1043 * We should set the dirty bit only for FOLL_WRITE but for now
1044 * the dirty bit in the pmd is meaningless. And if the dirty
1045 * bit will become meaningful and we'll only set it with
1046 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
1047 * set the young bit, instead of the current set_pmd_at.
1049 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1050 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1052 update_mmu_cache_pmd(vma, addr, pmd);
1055 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1056 pmd_t *pmd, int flags)
1058 unsigned long pfn = pmd_pfn(*pmd);
1059 struct mm_struct *mm = vma->vm_mm;
1060 struct dev_pagemap *pgmap;
1063 assert_spin_locked(pmd_lockptr(mm, pmd));
1065 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1068 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1073 if (flags & FOLL_TOUCH)
1074 touch_pmd(vma, addr, pmd);
1077 * device mapped pages can only be returned if the
1078 * caller will manage the page reference count.
1080 if (!(flags & FOLL_GET))
1081 return ERR_PTR(-EEXIST);
1083 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1084 pgmap = get_dev_pagemap(pfn, NULL);
1086 return ERR_PTR(-EFAULT);
1087 page = pfn_to_page(pfn);
1089 put_dev_pagemap(pgmap);
1094 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1095 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1096 struct vm_area_struct *vma)
1098 spinlock_t *dst_ptl, *src_ptl;
1099 struct page *src_page;
1101 pgtable_t pgtable = NULL;
1104 /* Skip if can be re-fill on fault */
1105 if (!vma_is_anonymous(vma))
1108 pgtable = pte_alloc_one(dst_mm, addr);
1109 if (unlikely(!pgtable))
1112 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1113 src_ptl = pmd_lockptr(src_mm, src_pmd);
1114 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1118 if (unlikely(!pmd_trans_huge(pmd))) {
1119 pte_free(dst_mm, pgtable);
1123 * When page table lock is held, the huge zero pmd should not be
1124 * under splitting since we don't split the page itself, only pmd to
1127 if (is_huge_zero_pmd(pmd)) {
1128 struct page *zero_page;
1130 * get_huge_zero_page() will never allocate a new page here,
1131 * since we already have a zero page to copy. It just takes a
1134 zero_page = get_huge_zero_page();
1135 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1141 src_page = pmd_page(pmd);
1142 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1144 page_dup_rmap(src_page, true);
1145 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1146 atomic_long_inc(&dst_mm->nr_ptes);
1147 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1149 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1150 pmd = pmd_mkold(pmd_wrprotect(pmd));
1151 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1155 spin_unlock(src_ptl);
1156 spin_unlock(dst_ptl);
1161 void huge_pmd_set_accessed(struct fault_env *fe, pmd_t orig_pmd)
1164 unsigned long haddr;
1166 fe->ptl = pmd_lock(fe->vma->vm_mm, fe->pmd);
1167 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1170 entry = pmd_mkyoung(orig_pmd);
1171 haddr = fe->address & HPAGE_PMD_MASK;
1172 if (pmdp_set_access_flags(fe->vma, haddr, fe->pmd, entry,
1173 fe->flags & FAULT_FLAG_WRITE))
1174 update_mmu_cache_pmd(fe->vma, fe->address, fe->pmd);
1177 spin_unlock(fe->ptl);
1180 static int do_huge_pmd_wp_page_fallback(struct fault_env *fe, pmd_t orig_pmd,
1183 struct vm_area_struct *vma = fe->vma;
1184 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1185 struct mem_cgroup *memcg;
1189 struct page **pages;
1190 unsigned long mmun_start; /* For mmu_notifiers */
1191 unsigned long mmun_end; /* For mmu_notifiers */
1193 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1195 if (unlikely(!pages)) {
1196 ret |= VM_FAULT_OOM;
1200 for (i = 0; i < HPAGE_PMD_NR; i++) {
1201 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1202 __GFP_OTHER_NODE, vma,
1203 fe->address, page_to_nid(page));
1204 if (unlikely(!pages[i] ||
1205 mem_cgroup_try_charge(pages[i], vma->vm_mm,
1206 GFP_KERNEL, &memcg, false))) {
1210 memcg = (void *)page_private(pages[i]);
1211 set_page_private(pages[i], 0);
1212 mem_cgroup_cancel_charge(pages[i], memcg,
1217 ret |= VM_FAULT_OOM;
1220 set_page_private(pages[i], (unsigned long)memcg);
1223 for (i = 0; i < HPAGE_PMD_NR; i++) {
1224 copy_user_highpage(pages[i], page + i,
1225 haddr + PAGE_SIZE * i, vma);
1226 __SetPageUptodate(pages[i]);
1231 mmun_end = haddr + HPAGE_PMD_SIZE;
1232 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1234 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
1235 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1236 goto out_free_pages;
1237 VM_BUG_ON_PAGE(!PageHead(page), page);
1239 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
1240 /* leave pmd empty until pte is filled */
1242 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, fe->pmd);
1243 pmd_populate(vma->vm_mm, &_pmd, pgtable);
1245 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1247 entry = mk_pte(pages[i], vma->vm_page_prot);
1248 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1249 memcg = (void *)page_private(pages[i]);
1250 set_page_private(pages[i], 0);
1251 page_add_new_anon_rmap(pages[i], fe->vma, haddr, false);
1252 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1253 lru_cache_add_active_or_unevictable(pages[i], vma);
1254 fe->pte = pte_offset_map(&_pmd, haddr);
1255 VM_BUG_ON(!pte_none(*fe->pte));
1256 set_pte_at(vma->vm_mm, haddr, fe->pte, entry);
1261 smp_wmb(); /* make pte visible before pmd */
1262 pmd_populate(vma->vm_mm, fe->pmd, pgtable);
1263 page_remove_rmap(page, true);
1264 spin_unlock(fe->ptl);
1266 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1268 ret |= VM_FAULT_WRITE;
1275 spin_unlock(fe->ptl);
1276 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1277 for (i = 0; i < HPAGE_PMD_NR; i++) {
1278 memcg = (void *)page_private(pages[i]);
1279 set_page_private(pages[i], 0);
1280 mem_cgroup_cancel_charge(pages[i], memcg, false);
1287 int do_huge_pmd_wp_page(struct fault_env *fe, pmd_t orig_pmd)
1289 struct vm_area_struct *vma = fe->vma;
1290 struct page *page = NULL, *new_page;
1291 struct mem_cgroup *memcg;
1292 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1293 unsigned long mmun_start; /* For mmu_notifiers */
1294 unsigned long mmun_end; /* For mmu_notifiers */
1295 gfp_t huge_gfp; /* for allocation and charge */
1298 fe->ptl = pmd_lockptr(vma->vm_mm, fe->pmd);
1299 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1300 if (is_huge_zero_pmd(orig_pmd))
1303 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1306 page = pmd_page(orig_pmd);
1307 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1309 * We can only reuse the page if nobody else maps the huge page or it's
1312 if (page_trans_huge_mapcount(page, NULL) == 1) {
1314 entry = pmd_mkyoung(orig_pmd);
1315 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1316 if (pmdp_set_access_flags(vma, haddr, fe->pmd, entry, 1))
1317 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1318 ret |= VM_FAULT_WRITE;
1322 spin_unlock(fe->ptl);
1324 if (transparent_hugepage_enabled(vma) &&
1325 !transparent_hugepage_debug_cow()) {
1326 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1327 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1331 if (likely(new_page)) {
1332 prep_transhuge_page(new_page);
1335 split_huge_pmd(vma, fe->pmd, fe->address);
1336 ret |= VM_FAULT_FALLBACK;
1338 ret = do_huge_pmd_wp_page_fallback(fe, orig_pmd, page);
1339 if (ret & VM_FAULT_OOM) {
1340 split_huge_pmd(vma, fe->pmd, fe->address);
1341 ret |= VM_FAULT_FALLBACK;
1345 count_vm_event(THP_FAULT_FALLBACK);
1349 if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1350 huge_gfp, &memcg, true))) {
1352 split_huge_pmd(vma, fe->pmd, fe->address);
1355 ret |= VM_FAULT_FALLBACK;
1356 count_vm_event(THP_FAULT_FALLBACK);
1360 count_vm_event(THP_FAULT_ALLOC);
1363 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1365 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1366 __SetPageUptodate(new_page);
1369 mmun_end = haddr + HPAGE_PMD_SIZE;
1370 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1375 if (unlikely(!pmd_same(*fe->pmd, orig_pmd))) {
1376 spin_unlock(fe->ptl);
1377 mem_cgroup_cancel_charge(new_page, memcg, true);
1382 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1383 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1384 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
1385 page_add_new_anon_rmap(new_page, vma, haddr, true);
1386 mem_cgroup_commit_charge(new_page, memcg, false, true);
1387 lru_cache_add_active_or_unevictable(new_page, vma);
1388 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
1389 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1391 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1392 put_huge_zero_page();
1394 VM_BUG_ON_PAGE(!PageHead(page), page);
1395 page_remove_rmap(page, true);
1398 ret |= VM_FAULT_WRITE;
1400 spin_unlock(fe->ptl);
1402 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1406 spin_unlock(fe->ptl);
1410 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1415 struct mm_struct *mm = vma->vm_mm;
1416 struct page *page = NULL;
1418 assert_spin_locked(pmd_lockptr(mm, pmd));
1420 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1423 /* Avoid dumping huge zero page */
1424 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1425 return ERR_PTR(-EFAULT);
1427 /* Full NUMA hinting faults to serialise migration in fault paths */
1428 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1431 page = pmd_page(*pmd);
1432 VM_BUG_ON_PAGE(!PageHead(page), page);
1433 if (flags & FOLL_TOUCH)
1434 touch_pmd(vma, addr, pmd);
1435 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1437 * We don't mlock() pte-mapped THPs. This way we can avoid
1438 * leaking mlocked pages into non-VM_LOCKED VMAs.
1442 * In most cases the pmd is the only mapping of the page as we
1443 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1444 * writable private mappings in populate_vma_page_range().
1446 * The only scenario when we have the page shared here is if we
1447 * mlocking read-only mapping shared over fork(). We skip
1448 * mlocking such pages.
1452 * We can expect PageDoubleMap() to be stable under page lock:
1453 * for file pages we set it in page_add_file_rmap(), which
1454 * requires page to be locked.
1457 if (PageAnon(page) && compound_mapcount(page) != 1)
1459 if (PageDoubleMap(page) || !page->mapping)
1461 if (!trylock_page(page))
1464 if (page->mapping && !PageDoubleMap(page))
1465 mlock_vma_page(page);
1469 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1470 VM_BUG_ON_PAGE(!PageCompound(page), page);
1471 if (flags & FOLL_GET)
1478 /* NUMA hinting page fault entry point for trans huge pmds */
1479 int do_huge_pmd_numa_page(struct fault_env *fe, pmd_t pmd)
1481 struct vm_area_struct *vma = fe->vma;
1482 struct anon_vma *anon_vma = NULL;
1484 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1485 int page_nid = -1, this_nid = numa_node_id();
1486 int target_nid, last_cpupid = -1;
1488 bool migrated = false;
1492 /* A PROT_NONE fault should not end up here */
1493 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1495 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
1496 if (unlikely(!pmd_same(pmd, *fe->pmd)))
1500 * If there are potential migrations, wait for completion and retry
1501 * without disrupting NUMA hinting information. Do not relock and
1502 * check_same as the page may no longer be mapped.
1504 if (unlikely(pmd_trans_migrating(*fe->pmd))) {
1505 page = pmd_page(*fe->pmd);
1506 spin_unlock(fe->ptl);
1507 wait_on_page_locked(page);
1511 page = pmd_page(pmd);
1512 BUG_ON(is_huge_zero_page(page));
1513 page_nid = page_to_nid(page);
1514 last_cpupid = page_cpupid_last(page);
1515 count_vm_numa_event(NUMA_HINT_FAULTS);
1516 if (page_nid == this_nid) {
1517 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1518 flags |= TNF_FAULT_LOCAL;
1521 /* See similar comment in do_numa_page for explanation */
1522 if (!(vma->vm_flags & VM_WRITE))
1523 flags |= TNF_NO_GROUP;
1526 * Acquire the page lock to serialise THP migrations but avoid dropping
1527 * page_table_lock if at all possible
1529 page_locked = trylock_page(page);
1530 target_nid = mpol_misplaced(page, vma, haddr);
1531 if (target_nid == -1) {
1532 /* If the page was locked, there are no parallel migrations */
1537 /* Migration could have started since the pmd_trans_migrating check */
1539 spin_unlock(fe->ptl);
1540 wait_on_page_locked(page);
1546 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1547 * to serialises splits
1550 spin_unlock(fe->ptl);
1551 anon_vma = page_lock_anon_vma_read(page);
1553 /* Confirm the PMD did not change while page_table_lock was released */
1555 if (unlikely(!pmd_same(pmd, *fe->pmd))) {
1562 /* Bail if we fail to protect against THP splits for any reason */
1563 if (unlikely(!anon_vma)) {
1570 * Migrate the THP to the requested node, returns with page unlocked
1571 * and access rights restored.
1573 spin_unlock(fe->ptl);
1574 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1575 fe->pmd, pmd, fe->address, page, target_nid);
1577 flags |= TNF_MIGRATED;
1578 page_nid = target_nid;
1580 flags |= TNF_MIGRATE_FAIL;
1584 BUG_ON(!PageLocked(page));
1585 was_writable = pmd_write(pmd);
1586 pmd = pmd_modify(pmd, vma->vm_page_prot);
1587 pmd = pmd_mkyoung(pmd);
1589 pmd = pmd_mkwrite(pmd);
1590 set_pmd_at(vma->vm_mm, haddr, fe->pmd, pmd);
1591 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1594 spin_unlock(fe->ptl);
1598 page_unlock_anon_vma_read(anon_vma);
1601 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, fe->flags);
1606 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1607 pmd_t *pmd, unsigned long addr, unsigned long next)
1613 struct mm_struct *mm = tlb->mm;
1616 ptl = pmd_trans_huge_lock(pmd, vma);
1621 if (is_huge_zero_pmd(orig_pmd)) {
1626 page = pmd_page(orig_pmd);
1628 * If other processes are mapping this page, we couldn't discard
1629 * the page unless they all do MADV_FREE so let's skip the page.
1631 if (page_mapcount(page) != 1)
1634 if (!trylock_page(page))
1638 * If user want to discard part-pages of THP, split it so MADV_FREE
1639 * will deactivate only them.
1641 if (next - addr != HPAGE_PMD_SIZE) {
1644 split_huge_page(page);
1650 if (PageDirty(page))
1651 ClearPageDirty(page);
1654 if (PageActive(page))
1655 deactivate_page(page);
1657 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1658 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1660 orig_pmd = pmd_mkold(orig_pmd);
1661 orig_pmd = pmd_mkclean(orig_pmd);
1663 set_pmd_at(mm, addr, pmd, orig_pmd);
1664 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1673 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1674 pmd_t *pmd, unsigned long addr)
1679 ptl = __pmd_trans_huge_lock(pmd, vma);
1683 * For architectures like ppc64 we look at deposited pgtable
1684 * when calling pmdp_huge_get_and_clear. So do the
1685 * pgtable_trans_huge_withdraw after finishing pmdp related
1688 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1690 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1691 if (vma_is_dax(vma)) {
1693 if (is_huge_zero_pmd(orig_pmd))
1694 tlb_remove_page(tlb, pmd_page(orig_pmd));
1695 } else if (is_huge_zero_pmd(orig_pmd)) {
1696 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1697 atomic_long_dec(&tlb->mm->nr_ptes);
1699 tlb_remove_page(tlb, pmd_page(orig_pmd));
1701 struct page *page = pmd_page(orig_pmd);
1702 page_remove_rmap(page, true);
1703 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1704 VM_BUG_ON_PAGE(!PageHead(page), page);
1705 if (PageAnon(page)) {
1707 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1708 pte_free(tlb->mm, pgtable);
1709 atomic_long_dec(&tlb->mm->nr_ptes);
1710 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1712 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1715 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1720 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1721 unsigned long new_addr, unsigned long old_end,
1722 pmd_t *old_pmd, pmd_t *new_pmd)
1724 spinlock_t *old_ptl, *new_ptl;
1726 struct mm_struct *mm = vma->vm_mm;
1728 if ((old_addr & ~HPAGE_PMD_MASK) ||
1729 (new_addr & ~HPAGE_PMD_MASK) ||
1730 old_end - old_addr < HPAGE_PMD_SIZE)
1734 * The destination pmd shouldn't be established, free_pgtables()
1735 * should have release it.
1737 if (WARN_ON(!pmd_none(*new_pmd))) {
1738 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1743 * We don't have to worry about the ordering of src and dst
1744 * ptlocks because exclusive mmap_sem prevents deadlock.
1746 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1748 new_ptl = pmd_lockptr(mm, new_pmd);
1749 if (new_ptl != old_ptl)
1750 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1751 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1752 VM_BUG_ON(!pmd_none(*new_pmd));
1754 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1755 vma_is_anonymous(vma)) {
1757 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1758 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1760 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1761 if (new_ptl != old_ptl)
1762 spin_unlock(new_ptl);
1763 spin_unlock(old_ptl);
1771 * - 0 if PMD could not be locked
1772 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1773 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1775 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1776 unsigned long addr, pgprot_t newprot, int prot_numa)
1778 struct mm_struct *mm = vma->vm_mm;
1782 ptl = __pmd_trans_huge_lock(pmd, vma);
1785 bool preserve_write = prot_numa && pmd_write(*pmd);
1789 * Avoid trapping faults against the zero page. The read-only
1790 * data is likely to be read-cached on the local CPU and
1791 * local/remote hits to the zero page are not interesting.
1793 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1798 if (!prot_numa || !pmd_protnone(*pmd)) {
1799 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1800 entry = pmd_modify(entry, newprot);
1802 entry = pmd_mkwrite(entry);
1804 set_pmd_at(mm, addr, pmd, entry);
1805 BUG_ON(vma_is_anonymous(vma) && !preserve_write &&
1815 * Returns true if a given pmd maps a thp, false otherwise.
1817 * Note that if it returns true, this routine returns without unlocking page
1818 * table lock. So callers must unlock it.
1820 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1823 ptl = pmd_lock(vma->vm_mm, pmd);
1824 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1830 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1832 int hugepage_madvise(struct vm_area_struct *vma,
1833 unsigned long *vm_flags, int advice)
1839 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1840 * can't handle this properly after s390_enable_sie, so we simply
1841 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1843 if (mm_has_pgste(vma->vm_mm))
1847 * Be somewhat over-protective like KSM for now!
1849 if (*vm_flags & VM_NO_THP)
1851 *vm_flags &= ~VM_NOHUGEPAGE;
1852 *vm_flags |= VM_HUGEPAGE;
1854 * If the vma become good for khugepaged to scan,
1855 * register it here without waiting a page fault that
1856 * may not happen any time soon.
1858 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1861 case MADV_NOHUGEPAGE:
1863 * Be somewhat over-protective like KSM for now!
1865 if (*vm_flags & VM_NO_THP)
1867 *vm_flags &= ~VM_HUGEPAGE;
1868 *vm_flags |= VM_NOHUGEPAGE;
1870 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1871 * this vma even if we leave the mm registered in khugepaged if
1872 * it got registered before VM_NOHUGEPAGE was set.
1880 static int __init khugepaged_slab_init(void)
1882 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1883 sizeof(struct mm_slot),
1884 __alignof__(struct mm_slot), 0, NULL);
1891 static void __init khugepaged_slab_exit(void)
1893 kmem_cache_destroy(mm_slot_cache);
1896 static inline struct mm_slot *alloc_mm_slot(void)
1898 if (!mm_slot_cache) /* initialization failed */
1900 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1903 static inline void free_mm_slot(struct mm_slot *mm_slot)
1905 kmem_cache_free(mm_slot_cache, mm_slot);
1908 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1910 struct mm_slot *mm_slot;
1912 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1913 if (mm == mm_slot->mm)
1919 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1920 struct mm_slot *mm_slot)
1923 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1926 static inline int khugepaged_test_exit(struct mm_struct *mm)
1928 return atomic_read(&mm->mm_users) == 0;
1931 int __khugepaged_enter(struct mm_struct *mm)
1933 struct mm_slot *mm_slot;
1936 mm_slot = alloc_mm_slot();
1940 /* __khugepaged_exit() must not run from under us */
1941 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1942 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1943 free_mm_slot(mm_slot);
1947 spin_lock(&khugepaged_mm_lock);
1948 insert_to_mm_slots_hash(mm, mm_slot);
1950 * Insert just behind the scanning cursor, to let the area settle
1953 wakeup = list_empty(&khugepaged_scan.mm_head);
1954 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1955 spin_unlock(&khugepaged_mm_lock);
1957 atomic_inc(&mm->mm_count);
1959 wake_up_interruptible(&khugepaged_wait);
1964 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1965 unsigned long vm_flags)
1967 unsigned long hstart, hend;
1970 * Not yet faulted in so we will register later in the
1971 * page fault if needed.
1974 if (vma->vm_ops || (vm_flags & VM_NO_THP))
1975 /* khugepaged not yet working on file or special mappings */
1977 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1978 hend = vma->vm_end & HPAGE_PMD_MASK;
1980 return khugepaged_enter(vma, vm_flags);
1984 void __khugepaged_exit(struct mm_struct *mm)
1986 struct mm_slot *mm_slot;
1989 spin_lock(&khugepaged_mm_lock);
1990 mm_slot = get_mm_slot(mm);
1991 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1992 hash_del(&mm_slot->hash);
1993 list_del(&mm_slot->mm_node);
1996 spin_unlock(&khugepaged_mm_lock);
1999 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2000 free_mm_slot(mm_slot);
2002 } else if (mm_slot) {
2004 * This is required to serialize against
2005 * khugepaged_test_exit() (which is guaranteed to run
2006 * under mmap sem read mode). Stop here (after we
2007 * return all pagetables will be destroyed) until
2008 * khugepaged has finished working on the pagetables
2009 * under the mmap_sem.
2011 down_write(&mm->mmap_sem);
2012 up_write(&mm->mmap_sem);
2016 static void release_pte_page(struct page *page)
2018 /* 0 stands for page_is_file_cache(page) == false */
2019 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2021 putback_lru_page(page);
2024 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2026 while (--_pte >= pte) {
2027 pte_t pteval = *_pte;
2028 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2029 release_pte_page(pte_page(pteval));
2033 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2034 unsigned long address,
2037 struct page *page = NULL;
2039 int none_or_zero = 0, result = 0;
2040 bool referenced = false, writable = false;
2042 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2043 _pte++, address += PAGE_SIZE) {
2044 pte_t pteval = *_pte;
2045 if (pte_none(pteval) || (pte_present(pteval) &&
2046 is_zero_pfn(pte_pfn(pteval)))) {
2047 if (!userfaultfd_armed(vma) &&
2048 ++none_or_zero <= khugepaged_max_ptes_none) {
2051 result = SCAN_EXCEED_NONE_PTE;
2055 if (!pte_present(pteval)) {
2056 result = SCAN_PTE_NON_PRESENT;
2059 page = vm_normal_page(vma, address, pteval);
2060 if (unlikely(!page)) {
2061 result = SCAN_PAGE_NULL;
2065 VM_BUG_ON_PAGE(PageCompound(page), page);
2066 VM_BUG_ON_PAGE(!PageAnon(page), page);
2067 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
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)) {
2076 result = SCAN_PAGE_LOCK;
2081 * cannot use mapcount: can't collapse if there's a gup pin.
2082 * The page must only be referenced by the scanned process
2083 * and page swap cache.
2085 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2087 result = SCAN_PAGE_COUNT;
2090 if (pte_write(pteval)) {
2093 if (PageSwapCache(page) &&
2094 !reuse_swap_page(page, NULL)) {
2096 result = SCAN_SWAP_CACHE_PAGE;
2100 * Page is not in the swap cache. It can be collapsed
2106 * Isolate the page to avoid collapsing an hugepage
2107 * currently in use by the VM.
2109 if (isolate_lru_page(page)) {
2111 result = SCAN_DEL_PAGE_LRU;
2114 /* 0 stands for page_is_file_cache(page) == false */
2115 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2116 VM_BUG_ON_PAGE(!PageLocked(page), page);
2117 VM_BUG_ON_PAGE(PageLRU(page), page);
2119 /* If there is no mapped pte young don't collapse the page */
2120 if (pte_young(pteval) ||
2121 page_is_young(page) || PageReferenced(page) ||
2122 mmu_notifier_test_young(vma->vm_mm, address))
2125 if (likely(writable)) {
2126 if (likely(referenced)) {
2127 result = SCAN_SUCCEED;
2128 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2129 referenced, writable, result);
2133 result = SCAN_PAGE_RO;
2137 release_pte_pages(pte, _pte);
2138 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2139 referenced, writable, result);
2143 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2144 struct vm_area_struct *vma,
2145 unsigned long address,
2149 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2150 pte_t pteval = *_pte;
2151 struct page *src_page;
2153 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2154 clear_user_highpage(page, address);
2155 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2156 if (is_zero_pfn(pte_pfn(pteval))) {
2158 * ptl mostly unnecessary.
2162 * paravirt calls inside pte_clear here are
2165 pte_clear(vma->vm_mm, address, _pte);
2169 src_page = pte_page(pteval);
2170 copy_user_highpage(page, src_page, address, vma);
2171 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2172 release_pte_page(src_page);
2174 * ptl mostly unnecessary, but preempt has to
2175 * be disabled to update the per-cpu stats
2176 * inside page_remove_rmap().
2180 * paravirt calls inside pte_clear here are
2183 pte_clear(vma->vm_mm, address, _pte);
2184 page_remove_rmap(src_page, false);
2186 free_page_and_swap_cache(src_page);
2189 address += PAGE_SIZE;
2194 static void khugepaged_alloc_sleep(void)
2198 add_wait_queue(&khugepaged_wait, &wait);
2199 freezable_schedule_timeout_interruptible(
2200 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2201 remove_wait_queue(&khugepaged_wait, &wait);
2204 static int khugepaged_node_load[MAX_NUMNODES];
2206 static bool khugepaged_scan_abort(int nid)
2211 * If zone_reclaim_mode is disabled, then no extra effort is made to
2212 * allocate memory locally.
2214 if (!zone_reclaim_mode)
2217 /* If there is a count for this node already, it must be acceptable */
2218 if (khugepaged_node_load[nid])
2221 for (i = 0; i < MAX_NUMNODES; i++) {
2222 if (!khugepaged_node_load[i])
2224 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2231 static int khugepaged_find_target_node(void)
2233 static int last_khugepaged_target_node = NUMA_NO_NODE;
2234 int nid, target_node = 0, max_value = 0;
2236 /* find first node with max normal pages hit */
2237 for (nid = 0; nid < MAX_NUMNODES; nid++)
2238 if (khugepaged_node_load[nid] > max_value) {
2239 max_value = khugepaged_node_load[nid];
2243 /* do some balance if several nodes have the same hit record */
2244 if (target_node <= last_khugepaged_target_node)
2245 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2247 if (max_value == khugepaged_node_load[nid]) {
2252 last_khugepaged_target_node = target_node;
2256 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2258 if (IS_ERR(*hpage)) {
2264 khugepaged_alloc_sleep();
2265 } else if (*hpage) {
2273 static struct page *
2274 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2275 unsigned long address, int node)
2277 VM_BUG_ON_PAGE(*hpage, *hpage);
2280 * Before allocating the hugepage, release the mmap_sem read lock.
2281 * The allocation can take potentially a long time if it involves
2282 * sync compaction, and we do not need to hold the mmap_sem during
2283 * that. We will recheck the vma after taking it again in write mode.
2285 up_read(&mm->mmap_sem);
2287 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2288 if (unlikely(!*hpage)) {
2289 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2290 *hpage = ERR_PTR(-ENOMEM);
2294 prep_transhuge_page(*hpage);
2295 count_vm_event(THP_COLLAPSE_ALLOC);
2299 static int khugepaged_find_target_node(void)
2304 static inline struct page *alloc_khugepaged_hugepage(void)
2308 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2311 prep_transhuge_page(page);
2315 static struct page *khugepaged_alloc_hugepage(bool *wait)
2320 hpage = alloc_khugepaged_hugepage();
2322 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2327 khugepaged_alloc_sleep();
2329 count_vm_event(THP_COLLAPSE_ALLOC);
2330 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2335 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2338 *hpage = khugepaged_alloc_hugepage(wait);
2340 if (unlikely(!*hpage))
2346 static struct page *
2347 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2348 unsigned long address, int node)
2350 up_read(&mm->mmap_sem);
2357 static bool hugepage_vma_check(struct vm_area_struct *vma)
2359 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2360 (vma->vm_flags & VM_NOHUGEPAGE))
2362 if (!vma->anon_vma || vma->vm_ops)
2364 if (is_vma_temporary_stack(vma))
2366 return !(vma->vm_flags & VM_NO_THP);
2370 * If mmap_sem temporarily dropped, revalidate vma
2371 * before taking mmap_sem.
2372 * Return 0 if succeeds, otherwise return none-zero
2373 * value (scan code).
2376 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address)
2378 struct vm_area_struct *vma;
2379 unsigned long hstart, hend;
2381 if (unlikely(khugepaged_test_exit(mm)))
2382 return SCAN_ANY_PROCESS;
2384 vma = find_vma(mm, address);
2386 return SCAN_VMA_NULL;
2388 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2389 hend = vma->vm_end & HPAGE_PMD_MASK;
2390 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2391 return SCAN_ADDRESS_RANGE;
2392 if (!hugepage_vma_check(vma))
2393 return SCAN_VMA_CHECK;
2398 * Bring missing pages in from swap, to complete THP collapse.
2399 * Only done if khugepaged_scan_pmd believes it is worthwhile.
2401 * Called and returns without pte mapped or spinlocks held,
2402 * but with mmap_sem held to protect against vma changes.
2405 static bool __collapse_huge_page_swapin(struct mm_struct *mm,
2406 struct vm_area_struct *vma,
2407 unsigned long address, pmd_t *pmd)
2410 int swapped_in = 0, ret = 0;
2411 struct fault_env fe = {
2414 .flags = FAULT_FLAG_ALLOW_RETRY,
2418 fe.pte = pte_offset_map(pmd, address);
2419 for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE;
2420 fe.pte++, fe.address += PAGE_SIZE) {
2422 if (!is_swap_pte(pteval))
2425 ret = do_swap_page(&fe, pteval);
2426 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
2427 if (ret & VM_FAULT_RETRY) {
2428 down_read(&mm->mmap_sem);
2429 /* vma is no longer available, don't continue to swapin */
2430 if (hugepage_vma_revalidate(mm, address))
2432 /* check if the pmd is still valid */
2433 if (mm_find_pmd(mm, address) != pmd)
2436 if (ret & VM_FAULT_ERROR) {
2437 trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);
2440 /* pte is unmapped now, we need to map it */
2441 fe.pte = pte_offset_map(pmd, fe.address);
2445 trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
2449 static void collapse_huge_page(struct mm_struct *mm,
2450 unsigned long address,
2451 struct page **hpage,
2452 struct vm_area_struct *vma,
2458 struct page *new_page;
2459 spinlock_t *pmd_ptl, *pte_ptl;
2460 int isolated = 0, result = 0;
2461 struct mem_cgroup *memcg;
2462 unsigned long mmun_start; /* For mmu_notifiers */
2463 unsigned long mmun_end; /* For mmu_notifiers */
2466 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2468 /* Only allocate from the target node */
2469 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
2471 /* release the mmap_sem read lock. */
2472 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2474 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2478 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2479 result = SCAN_CGROUP_CHARGE_FAIL;
2483 down_read(&mm->mmap_sem);
2484 result = hugepage_vma_revalidate(mm, address);
2486 mem_cgroup_cancel_charge(new_page, memcg, true);
2487 up_read(&mm->mmap_sem);
2491 pmd = mm_find_pmd(mm, address);
2493 result = SCAN_PMD_NULL;
2494 mem_cgroup_cancel_charge(new_page, memcg, true);
2495 up_read(&mm->mmap_sem);
2500 * __collapse_huge_page_swapin always returns with mmap_sem locked.
2501 * If it fails, release mmap_sem and jump directly out.
2502 * Continuing to collapse causes inconsistency.
2504 if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
2505 mem_cgroup_cancel_charge(new_page, memcg, true);
2506 up_read(&mm->mmap_sem);
2510 up_read(&mm->mmap_sem);
2512 * Prevent all access to pagetables with the exception of
2513 * gup_fast later handled by the ptep_clear_flush and the VM
2514 * handled by the anon_vma lock + PG_lock.
2516 down_write(&mm->mmap_sem);
2517 result = hugepage_vma_revalidate(mm, address);
2520 /* check if the pmd is still valid */
2521 if (mm_find_pmd(mm, address) != pmd)
2524 anon_vma_lock_write(vma->anon_vma);
2526 pte = pte_offset_map(pmd, address);
2527 pte_ptl = pte_lockptr(mm, pmd);
2529 mmun_start = address;
2530 mmun_end = address + HPAGE_PMD_SIZE;
2531 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2532 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2534 * After this gup_fast can't run anymore. This also removes
2535 * any huge TLB entry from the CPU so we won't allow
2536 * huge and small TLB entries for the same virtual address
2537 * to avoid the risk of CPU bugs in that area.
2539 _pmd = pmdp_collapse_flush(vma, address, pmd);
2540 spin_unlock(pmd_ptl);
2541 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2544 isolated = __collapse_huge_page_isolate(vma, address, pte);
2545 spin_unlock(pte_ptl);
2547 if (unlikely(!isolated)) {
2550 BUG_ON(!pmd_none(*pmd));
2552 * We can only use set_pmd_at when establishing
2553 * hugepmds and never for establishing regular pmds that
2554 * points to regular pagetables. Use pmd_populate for that
2556 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2557 spin_unlock(pmd_ptl);
2558 anon_vma_unlock_write(vma->anon_vma);
2564 * All pages are isolated and locked so anon_vma rmap
2565 * can't run anymore.
2567 anon_vma_unlock_write(vma->anon_vma);
2569 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2571 __SetPageUptodate(new_page);
2572 pgtable = pmd_pgtable(_pmd);
2574 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2575 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2578 * spin_lock() below is not the equivalent of smp_wmb(), so
2579 * this is needed to avoid the copy_huge_page writes to become
2580 * visible after the set_pmd_at() write.
2585 BUG_ON(!pmd_none(*pmd));
2586 page_add_new_anon_rmap(new_page, vma, address, true);
2587 mem_cgroup_commit_charge(new_page, memcg, false, true);
2588 lru_cache_add_active_or_unevictable(new_page, vma);
2589 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2590 set_pmd_at(mm, address, pmd, _pmd);
2591 update_mmu_cache_pmd(vma, address, pmd);
2592 spin_unlock(pmd_ptl);
2596 khugepaged_pages_collapsed++;
2597 result = SCAN_SUCCEED;
2599 up_write(&mm->mmap_sem);
2601 trace_mm_collapse_huge_page(mm, isolated, result);
2604 mem_cgroup_cancel_charge(new_page, memcg, true);
2608 static int khugepaged_scan_pmd(struct mm_struct *mm,
2609 struct vm_area_struct *vma,
2610 unsigned long address,
2611 struct page **hpage)
2615 int ret = 0, none_or_zero = 0, result = 0;
2616 struct page *page = NULL;
2617 unsigned long _address;
2619 int node = NUMA_NO_NODE, unmapped = 0;
2620 bool writable = false, referenced = false;
2622 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2624 pmd = mm_find_pmd(mm, address);
2626 result = SCAN_PMD_NULL;
2630 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2631 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2632 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2633 _pte++, _address += PAGE_SIZE) {
2634 pte_t pteval = *_pte;
2635 if (is_swap_pte(pteval)) {
2636 if (++unmapped <= khugepaged_max_ptes_swap) {
2639 result = SCAN_EXCEED_SWAP_PTE;
2643 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2644 if (!userfaultfd_armed(vma) &&
2645 ++none_or_zero <= khugepaged_max_ptes_none) {
2648 result = SCAN_EXCEED_NONE_PTE;
2652 if (!pte_present(pteval)) {
2653 result = SCAN_PTE_NON_PRESENT;
2656 if (pte_write(pteval))
2659 page = vm_normal_page(vma, _address, pteval);
2660 if (unlikely(!page)) {
2661 result = SCAN_PAGE_NULL;
2665 /* TODO: teach khugepaged to collapse THP mapped with pte */
2666 if (PageCompound(page)) {
2667 result = SCAN_PAGE_COMPOUND;
2672 * Record which node the original page is from and save this
2673 * information to khugepaged_node_load[].
2674 * Khupaged will allocate hugepage from the node has the max
2677 node = page_to_nid(page);
2678 if (khugepaged_scan_abort(node)) {
2679 result = SCAN_SCAN_ABORT;
2682 khugepaged_node_load[node]++;
2683 if (!PageLRU(page)) {
2684 result = SCAN_PAGE_LRU;
2687 if (PageLocked(page)) {
2688 result = SCAN_PAGE_LOCK;
2691 if (!PageAnon(page)) {
2692 result = SCAN_PAGE_ANON;
2697 * cannot use mapcount: can't collapse if there's a gup pin.
2698 * The page must only be referenced by the scanned process
2699 * and page swap cache.
2701 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2702 result = SCAN_PAGE_COUNT;
2705 if (pte_young(pteval) ||
2706 page_is_young(page) || PageReferenced(page) ||
2707 mmu_notifier_test_young(vma->vm_mm, address))
2712 result = SCAN_SUCCEED;
2715 result = SCAN_NO_REFERENCED_PAGE;
2718 result = SCAN_PAGE_RO;
2721 pte_unmap_unlock(pte, ptl);
2723 node = khugepaged_find_target_node();
2724 /* collapse_huge_page will return with the mmap_sem released */
2725 collapse_huge_page(mm, address, hpage, vma, node);
2728 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
2729 none_or_zero, result, unmapped);
2733 static void collect_mm_slot(struct mm_slot *mm_slot)
2735 struct mm_struct *mm = mm_slot->mm;
2737 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2739 if (khugepaged_test_exit(mm)) {
2741 hash_del(&mm_slot->hash);
2742 list_del(&mm_slot->mm_node);
2745 * Not strictly needed because the mm exited already.
2747 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2750 /* khugepaged_mm_lock actually not necessary for the below */
2751 free_mm_slot(mm_slot);
2756 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2757 struct page **hpage)
2758 __releases(&khugepaged_mm_lock)
2759 __acquires(&khugepaged_mm_lock)
2761 struct mm_slot *mm_slot;
2762 struct mm_struct *mm;
2763 struct vm_area_struct *vma;
2767 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2769 if (khugepaged_scan.mm_slot)
2770 mm_slot = khugepaged_scan.mm_slot;
2772 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2773 struct mm_slot, mm_node);
2774 khugepaged_scan.address = 0;
2775 khugepaged_scan.mm_slot = mm_slot;
2777 spin_unlock(&khugepaged_mm_lock);
2780 down_read(&mm->mmap_sem);
2781 if (unlikely(khugepaged_test_exit(mm)))
2784 vma = find_vma(mm, khugepaged_scan.address);
2787 for (; vma; vma = vma->vm_next) {
2788 unsigned long hstart, hend;
2791 if (unlikely(khugepaged_test_exit(mm))) {
2795 if (!hugepage_vma_check(vma)) {
2800 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2801 hend = vma->vm_end & HPAGE_PMD_MASK;
2804 if (khugepaged_scan.address > hend)
2806 if (khugepaged_scan.address < hstart)
2807 khugepaged_scan.address = hstart;
2808 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2810 while (khugepaged_scan.address < hend) {
2813 if (unlikely(khugepaged_test_exit(mm)))
2814 goto breakouterloop;
2816 VM_BUG_ON(khugepaged_scan.address < hstart ||
2817 khugepaged_scan.address + HPAGE_PMD_SIZE >
2819 ret = khugepaged_scan_pmd(mm, vma,
2820 khugepaged_scan.address,
2822 /* move to next address */
2823 khugepaged_scan.address += HPAGE_PMD_SIZE;
2824 progress += HPAGE_PMD_NR;
2826 /* we released mmap_sem so break loop */
2827 goto breakouterloop_mmap_sem;
2828 if (progress >= pages)
2829 goto breakouterloop;
2833 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2834 breakouterloop_mmap_sem:
2836 spin_lock(&khugepaged_mm_lock);
2837 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2839 * Release the current mm_slot if this mm is about to die, or
2840 * if we scanned all vmas of this mm.
2842 if (khugepaged_test_exit(mm) || !vma) {
2844 * Make sure that if mm_users is reaching zero while
2845 * khugepaged runs here, khugepaged_exit will find
2846 * mm_slot not pointing to the exiting mm.
2848 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2849 khugepaged_scan.mm_slot = list_entry(
2850 mm_slot->mm_node.next,
2851 struct mm_slot, mm_node);
2852 khugepaged_scan.address = 0;
2854 khugepaged_scan.mm_slot = NULL;
2855 khugepaged_full_scans++;
2858 collect_mm_slot(mm_slot);
2864 static int khugepaged_has_work(void)
2866 return !list_empty(&khugepaged_scan.mm_head) &&
2867 khugepaged_enabled();
2870 static int khugepaged_wait_event(void)
2872 return !list_empty(&khugepaged_scan.mm_head) ||
2873 kthread_should_stop();
2876 static void khugepaged_do_scan(void)
2878 struct page *hpage = NULL;
2879 unsigned int progress = 0, pass_through_head = 0;
2880 unsigned int pages = khugepaged_pages_to_scan;
2883 barrier(); /* write khugepaged_pages_to_scan to local stack */
2885 while (progress < pages) {
2886 if (!khugepaged_prealloc_page(&hpage, &wait))
2891 if (unlikely(kthread_should_stop() || try_to_freeze()))
2894 spin_lock(&khugepaged_mm_lock);
2895 if (!khugepaged_scan.mm_slot)
2896 pass_through_head++;
2897 if (khugepaged_has_work() &&
2898 pass_through_head < 2)
2899 progress += khugepaged_scan_mm_slot(pages - progress,
2903 spin_unlock(&khugepaged_mm_lock);
2906 if (!IS_ERR_OR_NULL(hpage))
2910 static bool khugepaged_should_wakeup(void)
2912 return kthread_should_stop() ||
2913 time_after_eq(jiffies, khugepaged_sleep_expire);
2916 static void khugepaged_wait_work(void)
2918 if (khugepaged_has_work()) {
2919 const unsigned long scan_sleep_jiffies =
2920 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
2922 if (!scan_sleep_jiffies)
2925 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
2926 wait_event_freezable_timeout(khugepaged_wait,
2927 khugepaged_should_wakeup(),
2928 scan_sleep_jiffies);
2932 if (khugepaged_enabled())
2933 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2936 static int khugepaged(void *none)
2938 struct mm_slot *mm_slot;
2941 set_user_nice(current, MAX_NICE);
2943 while (!kthread_should_stop()) {
2944 khugepaged_do_scan();
2945 khugepaged_wait_work();
2948 spin_lock(&khugepaged_mm_lock);
2949 mm_slot = khugepaged_scan.mm_slot;
2950 khugepaged_scan.mm_slot = NULL;
2952 collect_mm_slot(mm_slot);
2953 spin_unlock(&khugepaged_mm_lock);
2957 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2958 unsigned long haddr, pmd_t *pmd)
2960 struct mm_struct *mm = vma->vm_mm;
2965 /* leave pmd empty until pte is filled */
2966 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2968 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2969 pmd_populate(mm, &_pmd, pgtable);
2971 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2973 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2974 entry = pte_mkspecial(entry);
2975 pte = pte_offset_map(&_pmd, haddr);
2976 VM_BUG_ON(!pte_none(*pte));
2977 set_pte_at(mm, haddr, pte, entry);
2980 smp_wmb(); /* make pte visible before pmd */
2981 pmd_populate(mm, pmd, pgtable);
2982 put_huge_zero_page();
2985 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2986 unsigned long haddr, bool freeze)
2988 struct mm_struct *mm = vma->vm_mm;
2992 bool young, write, dirty;
2996 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2997 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2998 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2999 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
3001 count_vm_event(THP_SPLIT_PMD);
3003 if (!vma_is_anonymous(vma)) {
3004 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
3005 if (is_huge_zero_pmd(_pmd))
3006 put_huge_zero_page();
3007 if (vma_is_dax(vma))
3009 page = pmd_page(_pmd);
3010 if (!PageReferenced(page) && pmd_young(_pmd))
3011 SetPageReferenced(page);
3012 page_remove_rmap(page, true);
3014 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
3016 } else if (is_huge_zero_pmd(*pmd)) {
3017 return __split_huge_zero_page_pmd(vma, haddr, pmd);
3020 page = pmd_page(*pmd);
3021 VM_BUG_ON_PAGE(!page_count(page), page);
3022 page_ref_add(page, HPAGE_PMD_NR - 1);
3023 write = pmd_write(*pmd);
3024 young = pmd_young(*pmd);
3025 dirty = pmd_dirty(*pmd);
3027 pmdp_huge_split_prepare(vma, haddr, pmd);
3028 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
3029 pmd_populate(mm, &_pmd, pgtable);
3031 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
3034 * Note that NUMA hinting access restrictions are not
3035 * transferred to avoid any possibility of altering
3036 * permissions across VMAs.
3039 swp_entry_t swp_entry;
3040 swp_entry = make_migration_entry(page + i, write);
3041 entry = swp_entry_to_pte(swp_entry);
3043 entry = mk_pte(page + i, vma->vm_page_prot);
3044 entry = maybe_mkwrite(entry, vma);
3046 entry = pte_wrprotect(entry);
3048 entry = pte_mkold(entry);
3051 SetPageDirty(page + i);
3052 pte = pte_offset_map(&_pmd, addr);
3053 BUG_ON(!pte_none(*pte));
3054 set_pte_at(mm, addr, pte, entry);
3055 atomic_inc(&page[i]._mapcount);
3060 * Set PG_double_map before dropping compound_mapcount to avoid
3061 * false-negative page_mapped().
3063 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
3064 for (i = 0; i < HPAGE_PMD_NR; i++)
3065 atomic_inc(&page[i]._mapcount);
3068 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
3069 /* Last compound_mapcount is gone. */
3070 __dec_zone_page_state(page, NR_ANON_THPS);
3071 if (TestClearPageDoubleMap(page)) {
3072 /* No need in mapcount reference anymore */
3073 for (i = 0; i < HPAGE_PMD_NR; i++)
3074 atomic_dec(&page[i]._mapcount);
3078 smp_wmb(); /* make pte visible before pmd */
3080 * Up to this point the pmd is present and huge and userland has the
3081 * whole access to the hugepage during the split (which happens in
3082 * place). If we overwrite the pmd with the not-huge version pointing
3083 * to the pte here (which of course we could if all CPUs were bug
3084 * free), userland could trigger a small page size TLB miss on the
3085 * small sized TLB while the hugepage TLB entry is still established in
3086 * the huge TLB. Some CPU doesn't like that.
3087 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
3088 * 383 on page 93. Intel should be safe but is also warns that it's
3089 * only safe if the permission and cache attributes of the two entries
3090 * loaded in the two TLB is identical (which should be the case here).
3091 * But it is generally safer to never allow small and huge TLB entries
3092 * for the same virtual address to be loaded simultaneously. So instead
3093 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
3094 * current pmd notpresent (atomically because here the pmd_trans_huge
3095 * and pmd_trans_splitting must remain set at all times on the pmd
3096 * until the split is complete for this pmd), then we flush the SMP TLB
3097 * and finally we write the non-huge version of the pmd entry with
3100 pmdp_invalidate(vma, haddr, pmd);
3101 pmd_populate(mm, pmd, pgtable);
3104 for (i = 0; i < HPAGE_PMD_NR; i++) {
3105 page_remove_rmap(page + i, false);
3111 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
3112 unsigned long address, bool freeze, struct page *page)
3115 struct mm_struct *mm = vma->vm_mm;
3116 unsigned long haddr = address & HPAGE_PMD_MASK;
3118 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
3119 ptl = pmd_lock(mm, pmd);
3122 * If caller asks to setup a migration entries, we need a page to check
3123 * pmd against. Otherwise we can end up replacing wrong page.
3125 VM_BUG_ON(freeze && !page);
3126 if (page && page != pmd_page(*pmd))
3129 if (pmd_trans_huge(*pmd)) {
3130 page = pmd_page(*pmd);
3131 if (PageMlocked(page))
3132 clear_page_mlock(page);
3133 } else if (!pmd_devmap(*pmd))
3135 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
3138 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
3141 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
3142 bool freeze, struct page *page)
3148 pgd = pgd_offset(vma->vm_mm, address);
3149 if (!pgd_present(*pgd))
3152 pud = pud_offset(pgd, address);
3153 if (!pud_present(*pud))
3156 pmd = pmd_offset(pud, address);
3158 __split_huge_pmd(vma, pmd, address, freeze, page);
3161 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3162 unsigned long start,
3167 * If the new start address isn't hpage aligned and it could
3168 * previously contain an hugepage: check if we need to split
3171 if (start & ~HPAGE_PMD_MASK &&
3172 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3173 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3174 split_huge_pmd_address(vma, start, false, NULL);
3177 * If the new end address isn't hpage aligned and it could
3178 * previously contain an hugepage: check if we need to split
3181 if (end & ~HPAGE_PMD_MASK &&
3182 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3183 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3184 split_huge_pmd_address(vma, end, false, NULL);
3187 * If we're also updating the vma->vm_next->vm_start, if the new
3188 * vm_next->vm_start isn't page aligned and it could previously
3189 * contain an hugepage: check if we need to split an huge pmd.
3191 if (adjust_next > 0) {
3192 struct vm_area_struct *next = vma->vm_next;
3193 unsigned long nstart = next->vm_start;
3194 nstart += adjust_next << PAGE_SHIFT;
3195 if (nstart & ~HPAGE_PMD_MASK &&
3196 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3197 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3198 split_huge_pmd_address(next, nstart, false, NULL);
3202 static void freeze_page(struct page *page)
3204 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
3208 VM_BUG_ON_PAGE(!PageHead(page), page);
3211 ttu_flags |= TTU_MIGRATION;
3213 /* We only need TTU_SPLIT_HUGE_PMD once */
3214 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
3215 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) {
3216 /* Cut short if the page is unmapped */
3217 if (page_count(page) == 1)
3220 ret = try_to_unmap(page + i, ttu_flags);
3222 VM_BUG_ON_PAGE(ret, page + i - 1);
3225 static void unfreeze_page(struct page *page)
3229 for (i = 0; i < HPAGE_PMD_NR; i++)
3230 remove_migration_ptes(page + i, page + i, true);
3233 static void __split_huge_page_tail(struct page *head, int tail,
3234 struct lruvec *lruvec, struct list_head *list)
3236 struct page *page_tail = head + tail;
3238 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
3239 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
3242 * tail_page->_refcount is zero and not changing from under us. But
3243 * get_page_unless_zero() may be running from under us on the
3244 * tail_page. If we used atomic_set() below instead of atomic_inc() or
3245 * atomic_add(), we would then run atomic_set() concurrently with
3246 * get_page_unless_zero(), and atomic_set() is implemented in C not
3247 * using locked ops. spin_unlock on x86 sometime uses locked ops
3248 * because of PPro errata 66, 92, so unless somebody can guarantee
3249 * atomic_set() here would be safe on all archs (and not only on x86),
3250 * it's safer to use atomic_inc()/atomic_add().
3252 if (PageAnon(head)) {
3253 page_ref_inc(page_tail);
3255 /* Additional pin to radix tree */
3256 page_ref_add(page_tail, 2);
3259 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3260 page_tail->flags |= (head->flags &
3261 ((1L << PG_referenced) |
3262 (1L << PG_swapbacked) |
3263 (1L << PG_mlocked) |
3264 (1L << PG_uptodate) |
3267 (1L << PG_unevictable) |
3271 * After clearing PageTail the gup refcount can be released.
3272 * Page flags also must be visible before we make the page non-compound.
3276 clear_compound_head(page_tail);
3278 if (page_is_young(head))
3279 set_page_young(page_tail);
3280 if (page_is_idle(head))
3281 set_page_idle(page_tail);
3283 /* ->mapping in first tail page is compound_mapcount */
3284 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3286 page_tail->mapping = head->mapping;
3288 page_tail->index = head->index + tail;
3289 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3290 lru_add_page_tail(head, page_tail, lruvec, list);
3293 static void __split_huge_page(struct page *page, struct list_head *list,
3294 unsigned long flags)
3296 struct page *head = compound_head(page);
3297 struct zone *zone = page_zone(head);
3298 struct lruvec *lruvec;
3302 lruvec = mem_cgroup_page_lruvec(head, zone);
3304 /* complete memcg works before add pages to LRU */
3305 mem_cgroup_split_huge_fixup(head);
3307 if (!PageAnon(page))
3308 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
3310 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
3311 __split_huge_page_tail(head, i, lruvec, list);
3312 /* Some pages can be beyond i_size: drop them from page cache */
3313 if (head[i].index >= end) {
3314 __ClearPageDirty(head + i);
3315 __delete_from_page_cache(head + i, NULL);
3320 ClearPageCompound(head);
3321 /* See comment in __split_huge_page_tail() */
3322 if (PageAnon(head)) {
3325 /* Additional pin to radix tree */
3326 page_ref_add(head, 2);
3327 spin_unlock(&head->mapping->tree_lock);
3330 spin_unlock_irqrestore(&page_zone(head)->lru_lock, flags);
3332 unfreeze_page(head);
3334 for (i = 0; i < HPAGE_PMD_NR; i++) {
3335 struct page *subpage = head + i;
3336 if (subpage == page)
3338 unlock_page(subpage);
3341 * Subpages may be freed if there wasn't any mapping
3342 * like if add_to_swap() is running on a lru page that
3343 * had its mapping zapped. And freeing these pages
3344 * requires taking the lru_lock so we do the put_page
3345 * of the tail pages after the split is complete.
3351 int total_mapcount(struct page *page)
3353 int i, compound, ret;
3355 VM_BUG_ON_PAGE(PageTail(page), page);
3357 if (likely(!PageCompound(page)))
3358 return atomic_read(&page->_mapcount) + 1;
3360 compound = compound_mapcount(page);
3364 for (i = 0; i < HPAGE_PMD_NR; i++)
3365 ret += atomic_read(&page[i]._mapcount) + 1;
3366 /* File pages has compound_mapcount included in _mapcount */
3367 if (!PageAnon(page))
3368 return ret - compound * HPAGE_PMD_NR;
3369 if (PageDoubleMap(page))
3370 ret -= HPAGE_PMD_NR;
3375 * This calculates accurately how many mappings a transparent hugepage
3376 * has (unlike page_mapcount() which isn't fully accurate). This full
3377 * accuracy is primarily needed to know if copy-on-write faults can
3378 * reuse the page and change the mapping to read-write instead of
3379 * copying them. At the same time this returns the total_mapcount too.
3381 * The function returns the highest mapcount any one of the subpages
3382 * has. If the return value is one, even if different processes are
3383 * mapping different subpages of the transparent hugepage, they can
3384 * all reuse it, because each process is reusing a different subpage.
3386 * The total_mapcount is instead counting all virtual mappings of the
3387 * subpages. If the total_mapcount is equal to "one", it tells the
3388 * caller all mappings belong to the same "mm" and in turn the
3389 * anon_vma of the transparent hugepage can become the vma->anon_vma
3390 * local one as no other process may be mapping any of the subpages.
3392 * It would be more accurate to replace page_mapcount() with
3393 * page_trans_huge_mapcount(), however we only use
3394 * page_trans_huge_mapcount() in the copy-on-write faults where we
3395 * need full accuracy to avoid breaking page pinning, because
3396 * page_trans_huge_mapcount() is slower than page_mapcount().
3398 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
3400 int i, ret, _total_mapcount, mapcount;
3402 /* hugetlbfs shouldn't call it */
3403 VM_BUG_ON_PAGE(PageHuge(page), page);
3405 if (likely(!PageTransCompound(page))) {
3406 mapcount = atomic_read(&page->_mapcount) + 1;
3408 *total_mapcount = mapcount;
3412 page = compound_head(page);
3414 _total_mapcount = ret = 0;
3415 for (i = 0; i < HPAGE_PMD_NR; i++) {
3416 mapcount = atomic_read(&page[i]._mapcount) + 1;
3417 ret = max(ret, mapcount);
3418 _total_mapcount += mapcount;
3420 if (PageDoubleMap(page)) {
3422 _total_mapcount -= HPAGE_PMD_NR;
3424 mapcount = compound_mapcount(page);
3426 _total_mapcount += mapcount;
3428 *total_mapcount = _total_mapcount;
3433 * This function splits huge page into normal pages. @page can point to any
3434 * subpage of huge page to split. Split doesn't change the position of @page.
3436 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3437 * The huge page must be locked.
3439 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3441 * Both head page and tail pages will inherit mapping, flags, and so on from
3444 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3445 * they are not mapped.
3447 * Returns 0 if the hugepage is split successfully.
3448 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3451 int split_huge_page_to_list(struct page *page, struct list_head *list)
3453 struct page *head = compound_head(page);
3454 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
3455 struct anon_vma *anon_vma = NULL;
3456 struct address_space *mapping = NULL;
3457 int count, mapcount, extra_pins, ret;
3459 unsigned long flags;
3461 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3462 VM_BUG_ON_PAGE(!PageLocked(page), page);
3463 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3464 VM_BUG_ON_PAGE(!PageCompound(page), page);
3466 if (PageAnon(head)) {
3468 * The caller does not necessarily hold an mmap_sem that would
3469 * prevent the anon_vma disappearing so we first we take a
3470 * reference to it and then lock the anon_vma for write. This
3471 * is similar to page_lock_anon_vma_read except the write lock
3472 * is taken to serialise against parallel split or collapse
3475 anon_vma = page_get_anon_vma(head);
3482 anon_vma_lock_write(anon_vma);
3484 mapping = head->mapping;
3492 /* Addidional pins from radix tree */
3493 extra_pins = HPAGE_PMD_NR;
3495 i_mmap_lock_read(mapping);
3499 * Racy check if we can split the page, before freeze_page() will
3502 if (total_mapcount(head) != page_count(head) - extra_pins - 1) {
3507 mlocked = PageMlocked(page);
3509 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3511 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3515 /* prevent PageLRU to go away from under us, and freeze lru stats */
3516 spin_lock_irqsave(&page_zone(head)->lru_lock, flags);
3521 spin_lock(&mapping->tree_lock);
3522 pslot = radix_tree_lookup_slot(&mapping->page_tree,
3525 * Check if the head page is present in radix tree.
3526 * We assume all tail are present too, if head is there.
3528 if (radix_tree_deref_slot_protected(pslot,
3529 &mapping->tree_lock) != head)
3533 /* Prevent deferred_split_scan() touching ->_refcount */
3534 spin_lock(&pgdata->split_queue_lock);
3535 count = page_count(head);
3536 mapcount = total_mapcount(head);
3537 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
3538 if (!list_empty(page_deferred_list(head))) {
3539 pgdata->split_queue_len--;
3540 list_del(page_deferred_list(head));
3543 __dec_zone_page_state(page, NR_SHMEM_THPS);
3544 spin_unlock(&pgdata->split_queue_lock);
3545 __split_huge_page(page, list, flags);
3548 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
3549 pr_alert("total_mapcount: %u, page_count(): %u\n",
3552 dump_page(head, NULL);
3553 dump_page(page, "total_mapcount(head) > 0");
3556 spin_unlock(&pgdata->split_queue_lock);
3558 spin_unlock(&mapping->tree_lock);
3559 spin_unlock_irqrestore(&page_zone(head)->lru_lock, flags);
3560 unfreeze_page(head);
3566 anon_vma_unlock_write(anon_vma);
3567 put_anon_vma(anon_vma);
3570 i_mmap_unlock_read(mapping);
3572 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3576 void free_transhuge_page(struct page *page)
3578 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3579 unsigned long flags;
3581 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3582 if (!list_empty(page_deferred_list(page))) {
3583 pgdata->split_queue_len--;
3584 list_del(page_deferred_list(page));
3586 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3587 free_compound_page(page);
3590 void deferred_split_huge_page(struct page *page)
3592 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3593 unsigned long flags;
3595 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3597 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3598 if (list_empty(page_deferred_list(page))) {
3599 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
3600 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
3601 pgdata->split_queue_len++;
3603 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3606 static unsigned long deferred_split_count(struct shrinker *shrink,
3607 struct shrink_control *sc)
3609 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3610 return ACCESS_ONCE(pgdata->split_queue_len);
3613 static unsigned long deferred_split_scan(struct shrinker *shrink,
3614 struct shrink_control *sc)
3616 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3617 unsigned long flags;
3618 LIST_HEAD(list), *pos, *next;
3622 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3623 /* Take pin on all head pages to avoid freeing them under us */
3624 list_for_each_safe(pos, next, &pgdata->split_queue) {
3625 page = list_entry((void *)pos, struct page, mapping);
3626 page = compound_head(page);
3627 if (get_page_unless_zero(page)) {
3628 list_move(page_deferred_list(page), &list);
3630 /* We lost race with put_compound_page() */
3631 list_del_init(page_deferred_list(page));
3632 pgdata->split_queue_len--;
3634 if (!--sc->nr_to_scan)
3637 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3639 list_for_each_safe(pos, next, &list) {
3640 page = list_entry((void *)pos, struct page, mapping);
3642 /* split_huge_page() removes page from list on success */
3643 if (!split_huge_page(page))
3649 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3650 list_splice_tail(&list, &pgdata->split_queue);
3651 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3654 * Stop shrinker if we didn't split any page, but the queue is empty.
3655 * This can happen if pages were freed under us.
3657 if (!split && list_empty(&pgdata->split_queue))
3662 static struct shrinker deferred_split_shrinker = {
3663 .count_objects = deferred_split_count,
3664 .scan_objects = deferred_split_scan,
3665 .seeks = DEFAULT_SEEKS,
3666 .flags = SHRINKER_NUMA_AWARE,
3669 #ifdef CONFIG_DEBUG_FS
3670 static int split_huge_pages_set(void *data, u64 val)
3674 unsigned long pfn, max_zone_pfn;
3675 unsigned long total = 0, split = 0;
3680 for_each_populated_zone(zone) {
3681 max_zone_pfn = zone_end_pfn(zone);
3682 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3683 if (!pfn_valid(pfn))
3686 page = pfn_to_page(pfn);
3687 if (!get_page_unless_zero(page))
3690 if (zone != page_zone(page))
3693 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
3698 if (!split_huge_page(page))
3706 pr_info("%lu of %lu THP split\n", split, total);
3710 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3713 static int __init split_huge_pages_debugfs(void)
3717 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3718 &split_huge_pages_fops);
3720 pr_warn("Failed to create split_huge_pages in debugfs");
3723 late_initcall(split_huge_pages_debugfs);