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,
446 &shmem_enabled_attr.attr,
448 #ifdef CONFIG_DEBUG_VM
449 &debug_cow_attr.attr,
454 static struct attribute_group hugepage_attr_group = {
455 .attrs = hugepage_attr,
458 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
459 struct kobj_attribute *attr,
462 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
465 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
466 struct kobj_attribute *attr,
467 const char *buf, size_t count)
472 err = kstrtoul(buf, 10, &msecs);
473 if (err || msecs > UINT_MAX)
476 khugepaged_scan_sleep_millisecs = msecs;
477 khugepaged_sleep_expire = 0;
478 wake_up_interruptible(&khugepaged_wait);
482 static struct kobj_attribute scan_sleep_millisecs_attr =
483 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
484 scan_sleep_millisecs_store);
486 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
487 struct kobj_attribute *attr,
490 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
493 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
494 struct kobj_attribute *attr,
495 const char *buf, size_t count)
500 err = kstrtoul(buf, 10, &msecs);
501 if (err || msecs > UINT_MAX)
504 khugepaged_alloc_sleep_millisecs = msecs;
505 khugepaged_sleep_expire = 0;
506 wake_up_interruptible(&khugepaged_wait);
510 static struct kobj_attribute alloc_sleep_millisecs_attr =
511 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
512 alloc_sleep_millisecs_store);
514 static ssize_t pages_to_scan_show(struct kobject *kobj,
515 struct kobj_attribute *attr,
518 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
520 static ssize_t pages_to_scan_store(struct kobject *kobj,
521 struct kobj_attribute *attr,
522 const char *buf, size_t count)
527 err = kstrtoul(buf, 10, &pages);
528 if (err || !pages || pages > UINT_MAX)
531 khugepaged_pages_to_scan = pages;
535 static struct kobj_attribute pages_to_scan_attr =
536 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
537 pages_to_scan_store);
539 static ssize_t pages_collapsed_show(struct kobject *kobj,
540 struct kobj_attribute *attr,
543 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
545 static struct kobj_attribute pages_collapsed_attr =
546 __ATTR_RO(pages_collapsed);
548 static ssize_t full_scans_show(struct kobject *kobj,
549 struct kobj_attribute *attr,
552 return sprintf(buf, "%u\n", khugepaged_full_scans);
554 static struct kobj_attribute full_scans_attr =
555 __ATTR_RO(full_scans);
557 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
558 struct kobj_attribute *attr, char *buf)
560 return single_flag_show(kobj, attr, buf,
561 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
563 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
564 struct kobj_attribute *attr,
565 const char *buf, size_t count)
567 return single_flag_store(kobj, attr, buf, count,
568 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
570 static struct kobj_attribute khugepaged_defrag_attr =
571 __ATTR(defrag, 0644, khugepaged_defrag_show,
572 khugepaged_defrag_store);
575 * max_ptes_none controls if khugepaged should collapse hugepages over
576 * any unmapped ptes in turn potentially increasing the memory
577 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
578 * reduce the available free memory in the system as it
579 * runs. Increasing max_ptes_none will instead potentially reduce the
580 * free memory in the system during the khugepaged scan.
582 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
583 struct kobj_attribute *attr,
586 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
588 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
589 struct kobj_attribute *attr,
590 const char *buf, size_t count)
593 unsigned long max_ptes_none;
595 err = kstrtoul(buf, 10, &max_ptes_none);
596 if (err || max_ptes_none > HPAGE_PMD_NR-1)
599 khugepaged_max_ptes_none = max_ptes_none;
603 static struct kobj_attribute khugepaged_max_ptes_none_attr =
604 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
605 khugepaged_max_ptes_none_store);
607 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
608 struct kobj_attribute *attr,
611 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
614 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
615 struct kobj_attribute *attr,
616 const char *buf, size_t count)
619 unsigned long max_ptes_swap;
621 err = kstrtoul(buf, 10, &max_ptes_swap);
622 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
625 khugepaged_max_ptes_swap = max_ptes_swap;
630 static struct kobj_attribute khugepaged_max_ptes_swap_attr =
631 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
632 khugepaged_max_ptes_swap_store);
634 static struct attribute *khugepaged_attr[] = {
635 &khugepaged_defrag_attr.attr,
636 &khugepaged_max_ptes_none_attr.attr,
637 &pages_to_scan_attr.attr,
638 &pages_collapsed_attr.attr,
639 &full_scans_attr.attr,
640 &scan_sleep_millisecs_attr.attr,
641 &alloc_sleep_millisecs_attr.attr,
642 &khugepaged_max_ptes_swap_attr.attr,
646 static struct attribute_group khugepaged_attr_group = {
647 .attrs = khugepaged_attr,
648 .name = "khugepaged",
651 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
655 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
656 if (unlikely(!*hugepage_kobj)) {
657 pr_err("failed to create transparent hugepage kobject\n");
661 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
663 pr_err("failed to register transparent hugepage group\n");
667 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
669 pr_err("failed to register transparent hugepage group\n");
670 goto remove_hp_group;
676 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
678 kobject_put(*hugepage_kobj);
682 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
684 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
685 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
686 kobject_put(hugepage_kobj);
689 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
694 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
697 #endif /* CONFIG_SYSFS */
699 static int __init hugepage_init(void)
702 struct kobject *hugepage_kobj;
704 if (!has_transparent_hugepage()) {
705 transparent_hugepage_flags = 0;
709 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
710 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
711 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
713 * hugepages can't be allocated by the buddy allocator
715 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
717 * we use page->mapping and page->index in second tail page
718 * as list_head: assuming THP order >= 2
720 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
722 err = hugepage_init_sysfs(&hugepage_kobj);
726 err = khugepaged_slab_init();
730 err = register_shrinker(&huge_zero_page_shrinker);
732 goto err_hzp_shrinker;
733 err = register_shrinker(&deferred_split_shrinker);
735 goto err_split_shrinker;
738 * By default disable transparent hugepages on smaller systems,
739 * where the extra memory used could hurt more than TLB overhead
740 * is likely to save. The admin can still enable it through /sys.
742 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
743 transparent_hugepage_flags = 0;
747 err = start_stop_khugepaged();
753 unregister_shrinker(&deferred_split_shrinker);
755 unregister_shrinker(&huge_zero_page_shrinker);
757 khugepaged_slab_exit();
759 hugepage_exit_sysfs(hugepage_kobj);
763 subsys_initcall(hugepage_init);
765 static int __init setup_transparent_hugepage(char *str)
770 if (!strcmp(str, "always")) {
771 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
772 &transparent_hugepage_flags);
773 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
774 &transparent_hugepage_flags);
776 } else if (!strcmp(str, "madvise")) {
777 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
778 &transparent_hugepage_flags);
779 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
780 &transparent_hugepage_flags);
782 } else if (!strcmp(str, "never")) {
783 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
784 &transparent_hugepage_flags);
785 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
786 &transparent_hugepage_flags);
791 pr_warn("transparent_hugepage= cannot parse, ignored\n");
794 __setup("transparent_hugepage=", setup_transparent_hugepage);
796 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
798 if (likely(vma->vm_flags & VM_WRITE))
799 pmd = pmd_mkwrite(pmd);
803 static inline struct list_head *page_deferred_list(struct page *page)
806 * ->lru in the tail pages is occupied by compound_head.
807 * Let's use ->mapping + ->index in the second tail page as list_head.
809 return (struct list_head *)&page[2].mapping;
812 void prep_transhuge_page(struct page *page)
815 * we use page->mapping and page->indexlru in second tail page
816 * as list_head: assuming THP order >= 2
819 INIT_LIST_HEAD(page_deferred_list(page));
820 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
823 static int __do_huge_pmd_anonymous_page(struct fault_env *fe, struct page *page,
826 struct vm_area_struct *vma = fe->vma;
827 struct mem_cgroup *memcg;
829 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
831 VM_BUG_ON_PAGE(!PageCompound(page), page);
833 if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
835 count_vm_event(THP_FAULT_FALLBACK);
836 return VM_FAULT_FALLBACK;
839 pgtable = pte_alloc_one(vma->vm_mm, haddr);
840 if (unlikely(!pgtable)) {
841 mem_cgroup_cancel_charge(page, memcg, true);
846 clear_huge_page(page, haddr, HPAGE_PMD_NR);
848 * The memory barrier inside __SetPageUptodate makes sure that
849 * clear_huge_page writes become visible before the set_pmd_at()
852 __SetPageUptodate(page);
854 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
855 if (unlikely(!pmd_none(*fe->pmd))) {
856 spin_unlock(fe->ptl);
857 mem_cgroup_cancel_charge(page, memcg, true);
859 pte_free(vma->vm_mm, pgtable);
863 /* Deliver the page fault to userland */
864 if (userfaultfd_missing(vma)) {
867 spin_unlock(fe->ptl);
868 mem_cgroup_cancel_charge(page, memcg, true);
870 pte_free(vma->vm_mm, pgtable);
871 ret = handle_userfault(fe, VM_UFFD_MISSING);
872 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
876 entry = mk_huge_pmd(page, vma->vm_page_prot);
877 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
878 page_add_new_anon_rmap(page, vma, haddr, true);
879 mem_cgroup_commit_charge(page, memcg, false, true);
880 lru_cache_add_active_or_unevictable(page, vma);
881 pgtable_trans_huge_deposit(vma->vm_mm, fe->pmd, pgtable);
882 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
883 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
884 atomic_long_inc(&vma->vm_mm->nr_ptes);
885 spin_unlock(fe->ptl);
886 count_vm_event(THP_FAULT_ALLOC);
893 * If THP is set to always then directly reclaim/compact as necessary
894 * If set to defer then do no reclaim and defer to khugepaged
895 * If set to madvise and the VMA is flagged then directly reclaim/compact
897 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
899 gfp_t reclaim_flags = 0;
901 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags) &&
902 (vma->vm_flags & VM_HUGEPAGE))
903 reclaim_flags = __GFP_DIRECT_RECLAIM;
904 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
905 reclaim_flags = __GFP_KSWAPD_RECLAIM;
906 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
907 reclaim_flags = __GFP_DIRECT_RECLAIM;
909 return GFP_TRANSHUGE | reclaim_flags;
912 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
913 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
915 return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0);
918 /* Caller must hold page table lock. */
919 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
920 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
921 struct page *zero_page)
926 entry = mk_pmd(zero_page, vma->vm_page_prot);
927 entry = pmd_mkhuge(entry);
929 pgtable_trans_huge_deposit(mm, pmd, pgtable);
930 set_pmd_at(mm, haddr, pmd, entry);
931 atomic_long_inc(&mm->nr_ptes);
935 int do_huge_pmd_anonymous_page(struct fault_env *fe)
937 struct vm_area_struct *vma = fe->vma;
940 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
942 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
943 return VM_FAULT_FALLBACK;
944 if (unlikely(anon_vma_prepare(vma)))
946 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
948 if (!(fe->flags & FAULT_FLAG_WRITE) &&
949 !mm_forbids_zeropage(vma->vm_mm) &&
950 transparent_hugepage_use_zero_page()) {
952 struct page *zero_page;
955 pgtable = pte_alloc_one(vma->vm_mm, haddr);
956 if (unlikely(!pgtable))
958 zero_page = get_huge_zero_page();
959 if (unlikely(!zero_page)) {
960 pte_free(vma->vm_mm, pgtable);
961 count_vm_event(THP_FAULT_FALLBACK);
962 return VM_FAULT_FALLBACK;
964 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
967 if (pmd_none(*fe->pmd)) {
968 if (userfaultfd_missing(vma)) {
969 spin_unlock(fe->ptl);
970 ret = handle_userfault(fe, VM_UFFD_MISSING);
971 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
973 set_huge_zero_page(pgtable, vma->vm_mm, vma,
974 haddr, fe->pmd, zero_page);
975 spin_unlock(fe->ptl);
979 spin_unlock(fe->ptl);
981 pte_free(vma->vm_mm, pgtable);
982 put_huge_zero_page();
986 gfp = alloc_hugepage_direct_gfpmask(vma);
987 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
988 if (unlikely(!page)) {
989 count_vm_event(THP_FAULT_FALLBACK);
990 return VM_FAULT_FALLBACK;
992 prep_transhuge_page(page);
993 return __do_huge_pmd_anonymous_page(fe, page, gfp);
996 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
997 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
999 struct mm_struct *mm = vma->vm_mm;
1003 ptl = pmd_lock(mm, pmd);
1004 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
1005 if (pfn_t_devmap(pfn))
1006 entry = pmd_mkdevmap(entry);
1008 entry = pmd_mkyoung(pmd_mkdirty(entry));
1009 entry = maybe_pmd_mkwrite(entry, vma);
1011 set_pmd_at(mm, addr, pmd, entry);
1012 update_mmu_cache_pmd(vma, addr, pmd);
1016 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
1017 pmd_t *pmd, pfn_t pfn, bool write)
1019 pgprot_t pgprot = vma->vm_page_prot;
1021 * If we had pmd_special, we could avoid all these restrictions,
1022 * but we need to be consistent with PTEs and architectures that
1023 * can't support a 'special' bit.
1025 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1026 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1027 (VM_PFNMAP|VM_MIXEDMAP));
1028 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1029 BUG_ON(!pfn_t_devmap(pfn));
1031 if (addr < vma->vm_start || addr >= vma->vm_end)
1032 return VM_FAULT_SIGBUS;
1033 if (track_pfn_insert(vma, &pgprot, pfn))
1034 return VM_FAULT_SIGBUS;
1035 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
1036 return VM_FAULT_NOPAGE;
1038 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
1040 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1046 * We should set the dirty bit only for FOLL_WRITE but for now
1047 * the dirty bit in the pmd is meaningless. And if the dirty
1048 * bit will become meaningful and we'll only set it with
1049 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
1050 * set the young bit, instead of the current set_pmd_at.
1052 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1053 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1055 update_mmu_cache_pmd(vma, addr, pmd);
1058 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1059 pmd_t *pmd, int flags)
1061 unsigned long pfn = pmd_pfn(*pmd);
1062 struct mm_struct *mm = vma->vm_mm;
1063 struct dev_pagemap *pgmap;
1066 assert_spin_locked(pmd_lockptr(mm, pmd));
1068 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1071 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1076 if (flags & FOLL_TOUCH)
1077 touch_pmd(vma, addr, pmd);
1080 * device mapped pages can only be returned if the
1081 * caller will manage the page reference count.
1083 if (!(flags & FOLL_GET))
1084 return ERR_PTR(-EEXIST);
1086 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1087 pgmap = get_dev_pagemap(pfn, NULL);
1089 return ERR_PTR(-EFAULT);
1090 page = pfn_to_page(pfn);
1092 put_dev_pagemap(pgmap);
1097 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1098 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1099 struct vm_area_struct *vma)
1101 spinlock_t *dst_ptl, *src_ptl;
1102 struct page *src_page;
1104 pgtable_t pgtable = NULL;
1107 /* Skip if can be re-fill on fault */
1108 if (!vma_is_anonymous(vma))
1111 pgtable = pte_alloc_one(dst_mm, addr);
1112 if (unlikely(!pgtable))
1115 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1116 src_ptl = pmd_lockptr(src_mm, src_pmd);
1117 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1121 if (unlikely(!pmd_trans_huge(pmd))) {
1122 pte_free(dst_mm, pgtable);
1126 * When page table lock is held, the huge zero pmd should not be
1127 * under splitting since we don't split the page itself, only pmd to
1130 if (is_huge_zero_pmd(pmd)) {
1131 struct page *zero_page;
1133 * get_huge_zero_page() will never allocate a new page here,
1134 * since we already have a zero page to copy. It just takes a
1137 zero_page = get_huge_zero_page();
1138 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1144 src_page = pmd_page(pmd);
1145 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1147 page_dup_rmap(src_page, true);
1148 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1149 atomic_long_inc(&dst_mm->nr_ptes);
1150 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1152 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1153 pmd = pmd_mkold(pmd_wrprotect(pmd));
1154 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1158 spin_unlock(src_ptl);
1159 spin_unlock(dst_ptl);
1164 void huge_pmd_set_accessed(struct fault_env *fe, pmd_t orig_pmd)
1167 unsigned long haddr;
1169 fe->ptl = pmd_lock(fe->vma->vm_mm, fe->pmd);
1170 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1173 entry = pmd_mkyoung(orig_pmd);
1174 haddr = fe->address & HPAGE_PMD_MASK;
1175 if (pmdp_set_access_flags(fe->vma, haddr, fe->pmd, entry,
1176 fe->flags & FAULT_FLAG_WRITE))
1177 update_mmu_cache_pmd(fe->vma, fe->address, fe->pmd);
1180 spin_unlock(fe->ptl);
1183 static int do_huge_pmd_wp_page_fallback(struct fault_env *fe, pmd_t orig_pmd,
1186 struct vm_area_struct *vma = fe->vma;
1187 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1188 struct mem_cgroup *memcg;
1192 struct page **pages;
1193 unsigned long mmun_start; /* For mmu_notifiers */
1194 unsigned long mmun_end; /* For mmu_notifiers */
1196 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1198 if (unlikely(!pages)) {
1199 ret |= VM_FAULT_OOM;
1203 for (i = 0; i < HPAGE_PMD_NR; i++) {
1204 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1205 __GFP_OTHER_NODE, vma,
1206 fe->address, page_to_nid(page));
1207 if (unlikely(!pages[i] ||
1208 mem_cgroup_try_charge(pages[i], vma->vm_mm,
1209 GFP_KERNEL, &memcg, false))) {
1213 memcg = (void *)page_private(pages[i]);
1214 set_page_private(pages[i], 0);
1215 mem_cgroup_cancel_charge(pages[i], memcg,
1220 ret |= VM_FAULT_OOM;
1223 set_page_private(pages[i], (unsigned long)memcg);
1226 for (i = 0; i < HPAGE_PMD_NR; i++) {
1227 copy_user_highpage(pages[i], page + i,
1228 haddr + PAGE_SIZE * i, vma);
1229 __SetPageUptodate(pages[i]);
1234 mmun_end = haddr + HPAGE_PMD_SIZE;
1235 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1237 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
1238 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1239 goto out_free_pages;
1240 VM_BUG_ON_PAGE(!PageHead(page), page);
1242 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
1243 /* leave pmd empty until pte is filled */
1245 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, fe->pmd);
1246 pmd_populate(vma->vm_mm, &_pmd, pgtable);
1248 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1250 entry = mk_pte(pages[i], vma->vm_page_prot);
1251 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1252 memcg = (void *)page_private(pages[i]);
1253 set_page_private(pages[i], 0);
1254 page_add_new_anon_rmap(pages[i], fe->vma, haddr, false);
1255 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1256 lru_cache_add_active_or_unevictable(pages[i], vma);
1257 fe->pte = pte_offset_map(&_pmd, haddr);
1258 VM_BUG_ON(!pte_none(*fe->pte));
1259 set_pte_at(vma->vm_mm, haddr, fe->pte, entry);
1264 smp_wmb(); /* make pte visible before pmd */
1265 pmd_populate(vma->vm_mm, fe->pmd, pgtable);
1266 page_remove_rmap(page, true);
1267 spin_unlock(fe->ptl);
1269 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1271 ret |= VM_FAULT_WRITE;
1278 spin_unlock(fe->ptl);
1279 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1280 for (i = 0; i < HPAGE_PMD_NR; i++) {
1281 memcg = (void *)page_private(pages[i]);
1282 set_page_private(pages[i], 0);
1283 mem_cgroup_cancel_charge(pages[i], memcg, false);
1290 int do_huge_pmd_wp_page(struct fault_env *fe, pmd_t orig_pmd)
1292 struct vm_area_struct *vma = fe->vma;
1293 struct page *page = NULL, *new_page;
1294 struct mem_cgroup *memcg;
1295 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1296 unsigned long mmun_start; /* For mmu_notifiers */
1297 unsigned long mmun_end; /* For mmu_notifiers */
1298 gfp_t huge_gfp; /* for allocation and charge */
1301 fe->ptl = pmd_lockptr(vma->vm_mm, fe->pmd);
1302 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1303 if (is_huge_zero_pmd(orig_pmd))
1306 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1309 page = pmd_page(orig_pmd);
1310 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1312 * We can only reuse the page if nobody else maps the huge page or it's
1315 if (page_trans_huge_mapcount(page, NULL) == 1) {
1317 entry = pmd_mkyoung(orig_pmd);
1318 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1319 if (pmdp_set_access_flags(vma, haddr, fe->pmd, entry, 1))
1320 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1321 ret |= VM_FAULT_WRITE;
1325 spin_unlock(fe->ptl);
1327 if (transparent_hugepage_enabled(vma) &&
1328 !transparent_hugepage_debug_cow()) {
1329 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1330 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1334 if (likely(new_page)) {
1335 prep_transhuge_page(new_page);
1338 split_huge_pmd(vma, fe->pmd, fe->address);
1339 ret |= VM_FAULT_FALLBACK;
1341 ret = do_huge_pmd_wp_page_fallback(fe, orig_pmd, page);
1342 if (ret & VM_FAULT_OOM) {
1343 split_huge_pmd(vma, fe->pmd, fe->address);
1344 ret |= VM_FAULT_FALLBACK;
1348 count_vm_event(THP_FAULT_FALLBACK);
1352 if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1353 huge_gfp, &memcg, true))) {
1355 split_huge_pmd(vma, fe->pmd, fe->address);
1358 ret |= VM_FAULT_FALLBACK;
1359 count_vm_event(THP_FAULT_FALLBACK);
1363 count_vm_event(THP_FAULT_ALLOC);
1366 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1368 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1369 __SetPageUptodate(new_page);
1372 mmun_end = haddr + HPAGE_PMD_SIZE;
1373 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1378 if (unlikely(!pmd_same(*fe->pmd, orig_pmd))) {
1379 spin_unlock(fe->ptl);
1380 mem_cgroup_cancel_charge(new_page, memcg, true);
1385 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1386 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1387 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
1388 page_add_new_anon_rmap(new_page, vma, haddr, true);
1389 mem_cgroup_commit_charge(new_page, memcg, false, true);
1390 lru_cache_add_active_or_unevictable(new_page, vma);
1391 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
1392 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1394 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1395 put_huge_zero_page();
1397 VM_BUG_ON_PAGE(!PageHead(page), page);
1398 page_remove_rmap(page, true);
1401 ret |= VM_FAULT_WRITE;
1403 spin_unlock(fe->ptl);
1405 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1409 spin_unlock(fe->ptl);
1413 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1418 struct mm_struct *mm = vma->vm_mm;
1419 struct page *page = NULL;
1421 assert_spin_locked(pmd_lockptr(mm, pmd));
1423 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1426 /* Avoid dumping huge zero page */
1427 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1428 return ERR_PTR(-EFAULT);
1430 /* Full NUMA hinting faults to serialise migration in fault paths */
1431 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1434 page = pmd_page(*pmd);
1435 VM_BUG_ON_PAGE(!PageHead(page), page);
1436 if (flags & FOLL_TOUCH)
1437 touch_pmd(vma, addr, pmd);
1438 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1440 * We don't mlock() pte-mapped THPs. This way we can avoid
1441 * leaking mlocked pages into non-VM_LOCKED VMAs.
1445 * In most cases the pmd is the only mapping of the page as we
1446 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1447 * writable private mappings in populate_vma_page_range().
1449 * The only scenario when we have the page shared here is if we
1450 * mlocking read-only mapping shared over fork(). We skip
1451 * mlocking such pages.
1455 * We can expect PageDoubleMap() to be stable under page lock:
1456 * for file pages we set it in page_add_file_rmap(), which
1457 * requires page to be locked.
1460 if (PageAnon(page) && compound_mapcount(page) != 1)
1462 if (PageDoubleMap(page) || !page->mapping)
1464 if (!trylock_page(page))
1467 if (page->mapping && !PageDoubleMap(page))
1468 mlock_vma_page(page);
1472 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1473 VM_BUG_ON_PAGE(!PageCompound(page), page);
1474 if (flags & FOLL_GET)
1481 /* NUMA hinting page fault entry point for trans huge pmds */
1482 int do_huge_pmd_numa_page(struct fault_env *fe, pmd_t pmd)
1484 struct vm_area_struct *vma = fe->vma;
1485 struct anon_vma *anon_vma = NULL;
1487 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1488 int page_nid = -1, this_nid = numa_node_id();
1489 int target_nid, last_cpupid = -1;
1491 bool migrated = false;
1495 /* A PROT_NONE fault should not end up here */
1496 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1498 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
1499 if (unlikely(!pmd_same(pmd, *fe->pmd)))
1503 * If there are potential migrations, wait for completion and retry
1504 * without disrupting NUMA hinting information. Do not relock and
1505 * check_same as the page may no longer be mapped.
1507 if (unlikely(pmd_trans_migrating(*fe->pmd))) {
1508 page = pmd_page(*fe->pmd);
1509 spin_unlock(fe->ptl);
1510 wait_on_page_locked(page);
1514 page = pmd_page(pmd);
1515 BUG_ON(is_huge_zero_page(page));
1516 page_nid = page_to_nid(page);
1517 last_cpupid = page_cpupid_last(page);
1518 count_vm_numa_event(NUMA_HINT_FAULTS);
1519 if (page_nid == this_nid) {
1520 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1521 flags |= TNF_FAULT_LOCAL;
1524 /* See similar comment in do_numa_page for explanation */
1525 if (!(vma->vm_flags & VM_WRITE))
1526 flags |= TNF_NO_GROUP;
1529 * Acquire the page lock to serialise THP migrations but avoid dropping
1530 * page_table_lock if at all possible
1532 page_locked = trylock_page(page);
1533 target_nid = mpol_misplaced(page, vma, haddr);
1534 if (target_nid == -1) {
1535 /* If the page was locked, there are no parallel migrations */
1540 /* Migration could have started since the pmd_trans_migrating check */
1542 spin_unlock(fe->ptl);
1543 wait_on_page_locked(page);
1549 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1550 * to serialises splits
1553 spin_unlock(fe->ptl);
1554 anon_vma = page_lock_anon_vma_read(page);
1556 /* Confirm the PMD did not change while page_table_lock was released */
1558 if (unlikely(!pmd_same(pmd, *fe->pmd))) {
1565 /* Bail if we fail to protect against THP splits for any reason */
1566 if (unlikely(!anon_vma)) {
1573 * Migrate the THP to the requested node, returns with page unlocked
1574 * and access rights restored.
1576 spin_unlock(fe->ptl);
1577 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1578 fe->pmd, pmd, fe->address, page, target_nid);
1580 flags |= TNF_MIGRATED;
1581 page_nid = target_nid;
1583 flags |= TNF_MIGRATE_FAIL;
1587 BUG_ON(!PageLocked(page));
1588 was_writable = pmd_write(pmd);
1589 pmd = pmd_modify(pmd, vma->vm_page_prot);
1590 pmd = pmd_mkyoung(pmd);
1592 pmd = pmd_mkwrite(pmd);
1593 set_pmd_at(vma->vm_mm, haddr, fe->pmd, pmd);
1594 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1597 spin_unlock(fe->ptl);
1601 page_unlock_anon_vma_read(anon_vma);
1604 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, fe->flags);
1609 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1610 pmd_t *pmd, unsigned long addr, unsigned long next)
1616 struct mm_struct *mm = tlb->mm;
1619 ptl = pmd_trans_huge_lock(pmd, vma);
1624 if (is_huge_zero_pmd(orig_pmd)) {
1629 page = pmd_page(orig_pmd);
1631 * If other processes are mapping this page, we couldn't discard
1632 * the page unless they all do MADV_FREE so let's skip the page.
1634 if (page_mapcount(page) != 1)
1637 if (!trylock_page(page))
1641 * If user want to discard part-pages of THP, split it so MADV_FREE
1642 * will deactivate only them.
1644 if (next - addr != HPAGE_PMD_SIZE) {
1647 split_huge_page(page);
1653 if (PageDirty(page))
1654 ClearPageDirty(page);
1657 if (PageActive(page))
1658 deactivate_page(page);
1660 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1661 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1663 orig_pmd = pmd_mkold(orig_pmd);
1664 orig_pmd = pmd_mkclean(orig_pmd);
1666 set_pmd_at(mm, addr, pmd, orig_pmd);
1667 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1676 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1677 pmd_t *pmd, unsigned long addr)
1682 ptl = __pmd_trans_huge_lock(pmd, vma);
1686 * For architectures like ppc64 we look at deposited pgtable
1687 * when calling pmdp_huge_get_and_clear. So do the
1688 * pgtable_trans_huge_withdraw after finishing pmdp related
1691 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1693 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1694 if (vma_is_dax(vma)) {
1696 if (is_huge_zero_pmd(orig_pmd))
1697 tlb_remove_page(tlb, pmd_page(orig_pmd));
1698 } else if (is_huge_zero_pmd(orig_pmd)) {
1699 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1700 atomic_long_dec(&tlb->mm->nr_ptes);
1702 tlb_remove_page(tlb, pmd_page(orig_pmd));
1704 struct page *page = pmd_page(orig_pmd);
1705 page_remove_rmap(page, true);
1706 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1707 VM_BUG_ON_PAGE(!PageHead(page), page);
1708 if (PageAnon(page)) {
1710 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1711 pte_free(tlb->mm, pgtable);
1712 atomic_long_dec(&tlb->mm->nr_ptes);
1713 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1715 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1718 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1723 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1724 unsigned long new_addr, unsigned long old_end,
1725 pmd_t *old_pmd, pmd_t *new_pmd)
1727 spinlock_t *old_ptl, *new_ptl;
1729 struct mm_struct *mm = vma->vm_mm;
1731 if ((old_addr & ~HPAGE_PMD_MASK) ||
1732 (new_addr & ~HPAGE_PMD_MASK) ||
1733 old_end - old_addr < HPAGE_PMD_SIZE)
1737 * The destination pmd shouldn't be established, free_pgtables()
1738 * should have release it.
1740 if (WARN_ON(!pmd_none(*new_pmd))) {
1741 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1746 * We don't have to worry about the ordering of src and dst
1747 * ptlocks because exclusive mmap_sem prevents deadlock.
1749 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1751 new_ptl = pmd_lockptr(mm, new_pmd);
1752 if (new_ptl != old_ptl)
1753 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1754 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1755 VM_BUG_ON(!pmd_none(*new_pmd));
1757 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1758 vma_is_anonymous(vma)) {
1760 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1761 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1763 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1764 if (new_ptl != old_ptl)
1765 spin_unlock(new_ptl);
1766 spin_unlock(old_ptl);
1774 * - 0 if PMD could not be locked
1775 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1776 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1778 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1779 unsigned long addr, pgprot_t newprot, int prot_numa)
1781 struct mm_struct *mm = vma->vm_mm;
1785 ptl = __pmd_trans_huge_lock(pmd, vma);
1788 bool preserve_write = prot_numa && pmd_write(*pmd);
1792 * Avoid trapping faults against the zero page. The read-only
1793 * data is likely to be read-cached on the local CPU and
1794 * local/remote hits to the zero page are not interesting.
1796 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1801 if (!prot_numa || !pmd_protnone(*pmd)) {
1802 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1803 entry = pmd_modify(entry, newprot);
1805 entry = pmd_mkwrite(entry);
1807 set_pmd_at(mm, addr, pmd, entry);
1808 BUG_ON(vma_is_anonymous(vma) && !preserve_write &&
1818 * Returns true if a given pmd maps a thp, false otherwise.
1820 * Note that if it returns true, this routine returns without unlocking page
1821 * table lock. So callers must unlock it.
1823 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1826 ptl = pmd_lock(vma->vm_mm, pmd);
1827 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1833 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1835 int hugepage_madvise(struct vm_area_struct *vma,
1836 unsigned long *vm_flags, int advice)
1842 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1843 * can't handle this properly after s390_enable_sie, so we simply
1844 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1846 if (mm_has_pgste(vma->vm_mm))
1850 * Be somewhat over-protective like KSM for now!
1852 if (*vm_flags & VM_NO_THP)
1854 *vm_flags &= ~VM_NOHUGEPAGE;
1855 *vm_flags |= VM_HUGEPAGE;
1857 * If the vma become good for khugepaged to scan,
1858 * register it here without waiting a page fault that
1859 * may not happen any time soon.
1861 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1864 case MADV_NOHUGEPAGE:
1866 * Be somewhat over-protective like KSM for now!
1868 if (*vm_flags & VM_NO_THP)
1870 *vm_flags &= ~VM_HUGEPAGE;
1871 *vm_flags |= VM_NOHUGEPAGE;
1873 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1874 * this vma even if we leave the mm registered in khugepaged if
1875 * it got registered before VM_NOHUGEPAGE was set.
1883 static int __init khugepaged_slab_init(void)
1885 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1886 sizeof(struct mm_slot),
1887 __alignof__(struct mm_slot), 0, NULL);
1894 static void __init khugepaged_slab_exit(void)
1896 kmem_cache_destroy(mm_slot_cache);
1899 static inline struct mm_slot *alloc_mm_slot(void)
1901 if (!mm_slot_cache) /* initialization failed */
1903 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1906 static inline void free_mm_slot(struct mm_slot *mm_slot)
1908 kmem_cache_free(mm_slot_cache, mm_slot);
1911 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1913 struct mm_slot *mm_slot;
1915 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1916 if (mm == mm_slot->mm)
1922 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1923 struct mm_slot *mm_slot)
1926 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1929 static inline int khugepaged_test_exit(struct mm_struct *mm)
1931 return atomic_read(&mm->mm_users) == 0;
1934 int __khugepaged_enter(struct mm_struct *mm)
1936 struct mm_slot *mm_slot;
1939 mm_slot = alloc_mm_slot();
1943 /* __khugepaged_exit() must not run from under us */
1944 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1945 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1946 free_mm_slot(mm_slot);
1950 spin_lock(&khugepaged_mm_lock);
1951 insert_to_mm_slots_hash(mm, mm_slot);
1953 * Insert just behind the scanning cursor, to let the area settle
1956 wakeup = list_empty(&khugepaged_scan.mm_head);
1957 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1958 spin_unlock(&khugepaged_mm_lock);
1960 atomic_inc(&mm->mm_count);
1962 wake_up_interruptible(&khugepaged_wait);
1967 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1968 unsigned long vm_flags)
1970 unsigned long hstart, hend;
1973 * Not yet faulted in so we will register later in the
1974 * page fault if needed.
1977 if (vma->vm_ops || (vm_flags & VM_NO_THP))
1978 /* khugepaged not yet working on file or special mappings */
1980 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1981 hend = vma->vm_end & HPAGE_PMD_MASK;
1983 return khugepaged_enter(vma, vm_flags);
1987 void __khugepaged_exit(struct mm_struct *mm)
1989 struct mm_slot *mm_slot;
1992 spin_lock(&khugepaged_mm_lock);
1993 mm_slot = get_mm_slot(mm);
1994 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1995 hash_del(&mm_slot->hash);
1996 list_del(&mm_slot->mm_node);
1999 spin_unlock(&khugepaged_mm_lock);
2002 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2003 free_mm_slot(mm_slot);
2005 } else if (mm_slot) {
2007 * This is required to serialize against
2008 * khugepaged_test_exit() (which is guaranteed to run
2009 * under mmap sem read mode). Stop here (after we
2010 * return all pagetables will be destroyed) until
2011 * khugepaged has finished working on the pagetables
2012 * under the mmap_sem.
2014 down_write(&mm->mmap_sem);
2015 up_write(&mm->mmap_sem);
2019 static void release_pte_page(struct page *page)
2021 /* 0 stands for page_is_file_cache(page) == false */
2022 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2024 putback_lru_page(page);
2027 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2029 while (--_pte >= pte) {
2030 pte_t pteval = *_pte;
2031 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2032 release_pte_page(pte_page(pteval));
2036 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2037 unsigned long address,
2040 struct page *page = NULL;
2042 int none_or_zero = 0, result = 0;
2043 bool referenced = false, writable = false;
2045 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2046 _pte++, address += PAGE_SIZE) {
2047 pte_t pteval = *_pte;
2048 if (pte_none(pteval) || (pte_present(pteval) &&
2049 is_zero_pfn(pte_pfn(pteval)))) {
2050 if (!userfaultfd_armed(vma) &&
2051 ++none_or_zero <= khugepaged_max_ptes_none) {
2054 result = SCAN_EXCEED_NONE_PTE;
2058 if (!pte_present(pteval)) {
2059 result = SCAN_PTE_NON_PRESENT;
2062 page = vm_normal_page(vma, address, pteval);
2063 if (unlikely(!page)) {
2064 result = SCAN_PAGE_NULL;
2068 VM_BUG_ON_PAGE(PageCompound(page), page);
2069 VM_BUG_ON_PAGE(!PageAnon(page), page);
2070 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2073 * We can do it before isolate_lru_page because the
2074 * page can't be freed from under us. NOTE: PG_lock
2075 * is needed to serialize against split_huge_page
2076 * when invoked from the VM.
2078 if (!trylock_page(page)) {
2079 result = SCAN_PAGE_LOCK;
2084 * cannot use mapcount: can't collapse if there's a gup pin.
2085 * The page must only be referenced by the scanned process
2086 * and page swap cache.
2088 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2090 result = SCAN_PAGE_COUNT;
2093 if (pte_write(pteval)) {
2096 if (PageSwapCache(page) &&
2097 !reuse_swap_page(page, NULL)) {
2099 result = SCAN_SWAP_CACHE_PAGE;
2103 * Page is not in the swap cache. It can be collapsed
2109 * Isolate the page to avoid collapsing an hugepage
2110 * currently in use by the VM.
2112 if (isolate_lru_page(page)) {
2114 result = SCAN_DEL_PAGE_LRU;
2117 /* 0 stands for page_is_file_cache(page) == false */
2118 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2119 VM_BUG_ON_PAGE(!PageLocked(page), page);
2120 VM_BUG_ON_PAGE(PageLRU(page), page);
2122 /* If there is no mapped pte young don't collapse the page */
2123 if (pte_young(pteval) ||
2124 page_is_young(page) || PageReferenced(page) ||
2125 mmu_notifier_test_young(vma->vm_mm, address))
2128 if (likely(writable)) {
2129 if (likely(referenced)) {
2130 result = SCAN_SUCCEED;
2131 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2132 referenced, writable, result);
2136 result = SCAN_PAGE_RO;
2140 release_pte_pages(pte, _pte);
2141 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2142 referenced, writable, result);
2146 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2147 struct vm_area_struct *vma,
2148 unsigned long address,
2152 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2153 pte_t pteval = *_pte;
2154 struct page *src_page;
2156 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2157 clear_user_highpage(page, address);
2158 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2159 if (is_zero_pfn(pte_pfn(pteval))) {
2161 * ptl mostly unnecessary.
2165 * paravirt calls inside pte_clear here are
2168 pte_clear(vma->vm_mm, address, _pte);
2172 src_page = pte_page(pteval);
2173 copy_user_highpage(page, src_page, address, vma);
2174 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2175 release_pte_page(src_page);
2177 * ptl mostly unnecessary, but preempt has to
2178 * be disabled to update the per-cpu stats
2179 * inside page_remove_rmap().
2183 * paravirt calls inside pte_clear here are
2186 pte_clear(vma->vm_mm, address, _pte);
2187 page_remove_rmap(src_page, false);
2189 free_page_and_swap_cache(src_page);
2192 address += PAGE_SIZE;
2197 static void khugepaged_alloc_sleep(void)
2201 add_wait_queue(&khugepaged_wait, &wait);
2202 freezable_schedule_timeout_interruptible(
2203 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2204 remove_wait_queue(&khugepaged_wait, &wait);
2207 static int khugepaged_node_load[MAX_NUMNODES];
2209 static bool khugepaged_scan_abort(int nid)
2214 * If zone_reclaim_mode is disabled, then no extra effort is made to
2215 * allocate memory locally.
2217 if (!zone_reclaim_mode)
2220 /* If there is a count for this node already, it must be acceptable */
2221 if (khugepaged_node_load[nid])
2224 for (i = 0; i < MAX_NUMNODES; i++) {
2225 if (!khugepaged_node_load[i])
2227 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2234 static int khugepaged_find_target_node(void)
2236 static int last_khugepaged_target_node = NUMA_NO_NODE;
2237 int nid, target_node = 0, max_value = 0;
2239 /* find first node with max normal pages hit */
2240 for (nid = 0; nid < MAX_NUMNODES; nid++)
2241 if (khugepaged_node_load[nid] > max_value) {
2242 max_value = khugepaged_node_load[nid];
2246 /* do some balance if several nodes have the same hit record */
2247 if (target_node <= last_khugepaged_target_node)
2248 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2250 if (max_value == khugepaged_node_load[nid]) {
2255 last_khugepaged_target_node = target_node;
2259 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2261 if (IS_ERR(*hpage)) {
2267 khugepaged_alloc_sleep();
2268 } else if (*hpage) {
2276 static struct page *
2277 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2278 unsigned long address, int node)
2280 VM_BUG_ON_PAGE(*hpage, *hpage);
2283 * Before allocating the hugepage, release the mmap_sem read lock.
2284 * The allocation can take potentially a long time if it involves
2285 * sync compaction, and we do not need to hold the mmap_sem during
2286 * that. We will recheck the vma after taking it again in write mode.
2288 up_read(&mm->mmap_sem);
2290 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2291 if (unlikely(!*hpage)) {
2292 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2293 *hpage = ERR_PTR(-ENOMEM);
2297 prep_transhuge_page(*hpage);
2298 count_vm_event(THP_COLLAPSE_ALLOC);
2302 static int khugepaged_find_target_node(void)
2307 static inline struct page *alloc_khugepaged_hugepage(void)
2311 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2314 prep_transhuge_page(page);
2318 static struct page *khugepaged_alloc_hugepage(bool *wait)
2323 hpage = alloc_khugepaged_hugepage();
2325 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2330 khugepaged_alloc_sleep();
2332 count_vm_event(THP_COLLAPSE_ALLOC);
2333 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2338 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2341 *hpage = khugepaged_alloc_hugepage(wait);
2343 if (unlikely(!*hpage))
2349 static struct page *
2350 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2351 unsigned long address, int node)
2353 up_read(&mm->mmap_sem);
2360 static bool hugepage_vma_check(struct vm_area_struct *vma)
2362 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2363 (vma->vm_flags & VM_NOHUGEPAGE))
2365 if (!vma->anon_vma || vma->vm_ops)
2367 if (is_vma_temporary_stack(vma))
2369 return !(vma->vm_flags & VM_NO_THP);
2373 * If mmap_sem temporarily dropped, revalidate vma
2374 * before taking mmap_sem.
2375 * Return 0 if succeeds, otherwise return none-zero
2376 * value (scan code).
2379 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address)
2381 struct vm_area_struct *vma;
2382 unsigned long hstart, hend;
2384 if (unlikely(khugepaged_test_exit(mm)))
2385 return SCAN_ANY_PROCESS;
2387 vma = find_vma(mm, address);
2389 return SCAN_VMA_NULL;
2391 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2392 hend = vma->vm_end & HPAGE_PMD_MASK;
2393 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2394 return SCAN_ADDRESS_RANGE;
2395 if (!hugepage_vma_check(vma))
2396 return SCAN_VMA_CHECK;
2401 * Bring missing pages in from swap, to complete THP collapse.
2402 * Only done if khugepaged_scan_pmd believes it is worthwhile.
2404 * Called and returns without pte mapped or spinlocks held,
2405 * but with mmap_sem held to protect against vma changes.
2408 static bool __collapse_huge_page_swapin(struct mm_struct *mm,
2409 struct vm_area_struct *vma,
2410 unsigned long address, pmd_t *pmd)
2413 int swapped_in = 0, ret = 0;
2414 struct fault_env fe = {
2417 .flags = FAULT_FLAG_ALLOW_RETRY,
2421 fe.pte = pte_offset_map(pmd, address);
2422 for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE;
2423 fe.pte++, fe.address += PAGE_SIZE) {
2425 if (!is_swap_pte(pteval))
2428 ret = do_swap_page(&fe, pteval);
2429 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
2430 if (ret & VM_FAULT_RETRY) {
2431 down_read(&mm->mmap_sem);
2432 /* vma is no longer available, don't continue to swapin */
2433 if (hugepage_vma_revalidate(mm, address))
2435 /* check if the pmd is still valid */
2436 if (mm_find_pmd(mm, address) != pmd)
2439 if (ret & VM_FAULT_ERROR) {
2440 trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);
2443 /* pte is unmapped now, we need to map it */
2444 fe.pte = pte_offset_map(pmd, fe.address);
2448 trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);
2452 static void collapse_huge_page(struct mm_struct *mm,
2453 unsigned long address,
2454 struct page **hpage,
2455 struct vm_area_struct *vma,
2461 struct page *new_page;
2462 spinlock_t *pmd_ptl, *pte_ptl;
2463 int isolated = 0, result = 0;
2464 struct mem_cgroup *memcg;
2465 unsigned long mmun_start; /* For mmu_notifiers */
2466 unsigned long mmun_end; /* For mmu_notifiers */
2469 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2471 /* Only allocate from the target node */
2472 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
2474 /* release the mmap_sem read lock. */
2475 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2477 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2481 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2482 result = SCAN_CGROUP_CHARGE_FAIL;
2486 down_read(&mm->mmap_sem);
2487 result = hugepage_vma_revalidate(mm, address);
2489 mem_cgroup_cancel_charge(new_page, memcg, true);
2490 up_read(&mm->mmap_sem);
2494 pmd = mm_find_pmd(mm, address);
2496 result = SCAN_PMD_NULL;
2497 mem_cgroup_cancel_charge(new_page, memcg, true);
2498 up_read(&mm->mmap_sem);
2503 * __collapse_huge_page_swapin always returns with mmap_sem locked.
2504 * If it fails, release mmap_sem and jump directly out.
2505 * Continuing to collapse causes inconsistency.
2507 if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
2508 mem_cgroup_cancel_charge(new_page, memcg, true);
2509 up_read(&mm->mmap_sem);
2513 up_read(&mm->mmap_sem);
2515 * Prevent all access to pagetables with the exception of
2516 * gup_fast later handled by the ptep_clear_flush and the VM
2517 * handled by the anon_vma lock + PG_lock.
2519 down_write(&mm->mmap_sem);
2520 result = hugepage_vma_revalidate(mm, address);
2523 /* check if the pmd is still valid */
2524 if (mm_find_pmd(mm, address) != pmd)
2527 anon_vma_lock_write(vma->anon_vma);
2529 pte = pte_offset_map(pmd, address);
2530 pte_ptl = pte_lockptr(mm, pmd);
2532 mmun_start = address;
2533 mmun_end = address + HPAGE_PMD_SIZE;
2534 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2535 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2537 * After this gup_fast can't run anymore. This also removes
2538 * any huge TLB entry from the CPU so we won't allow
2539 * huge and small TLB entries for the same virtual address
2540 * to avoid the risk of CPU bugs in that area.
2542 _pmd = pmdp_collapse_flush(vma, address, pmd);
2543 spin_unlock(pmd_ptl);
2544 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2547 isolated = __collapse_huge_page_isolate(vma, address, pte);
2548 spin_unlock(pte_ptl);
2550 if (unlikely(!isolated)) {
2553 BUG_ON(!pmd_none(*pmd));
2555 * We can only use set_pmd_at when establishing
2556 * hugepmds and never for establishing regular pmds that
2557 * points to regular pagetables. Use pmd_populate for that
2559 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2560 spin_unlock(pmd_ptl);
2561 anon_vma_unlock_write(vma->anon_vma);
2567 * All pages are isolated and locked so anon_vma rmap
2568 * can't run anymore.
2570 anon_vma_unlock_write(vma->anon_vma);
2572 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2574 __SetPageUptodate(new_page);
2575 pgtable = pmd_pgtable(_pmd);
2577 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2578 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2581 * spin_lock() below is not the equivalent of smp_wmb(), so
2582 * this is needed to avoid the copy_huge_page writes to become
2583 * visible after the set_pmd_at() write.
2588 BUG_ON(!pmd_none(*pmd));
2589 page_add_new_anon_rmap(new_page, vma, address, true);
2590 mem_cgroup_commit_charge(new_page, memcg, false, true);
2591 lru_cache_add_active_or_unevictable(new_page, vma);
2592 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2593 set_pmd_at(mm, address, pmd, _pmd);
2594 update_mmu_cache_pmd(vma, address, pmd);
2595 spin_unlock(pmd_ptl);
2599 khugepaged_pages_collapsed++;
2600 result = SCAN_SUCCEED;
2602 up_write(&mm->mmap_sem);
2604 trace_mm_collapse_huge_page(mm, isolated, result);
2607 mem_cgroup_cancel_charge(new_page, memcg, true);
2611 static int khugepaged_scan_pmd(struct mm_struct *mm,
2612 struct vm_area_struct *vma,
2613 unsigned long address,
2614 struct page **hpage)
2618 int ret = 0, none_or_zero = 0, result = 0;
2619 struct page *page = NULL;
2620 unsigned long _address;
2622 int node = NUMA_NO_NODE, unmapped = 0;
2623 bool writable = false, referenced = false;
2625 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2627 pmd = mm_find_pmd(mm, address);
2629 result = SCAN_PMD_NULL;
2633 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2634 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2635 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2636 _pte++, _address += PAGE_SIZE) {
2637 pte_t pteval = *_pte;
2638 if (is_swap_pte(pteval)) {
2639 if (++unmapped <= khugepaged_max_ptes_swap) {
2642 result = SCAN_EXCEED_SWAP_PTE;
2646 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2647 if (!userfaultfd_armed(vma) &&
2648 ++none_or_zero <= khugepaged_max_ptes_none) {
2651 result = SCAN_EXCEED_NONE_PTE;
2655 if (!pte_present(pteval)) {
2656 result = SCAN_PTE_NON_PRESENT;
2659 if (pte_write(pteval))
2662 page = vm_normal_page(vma, _address, pteval);
2663 if (unlikely(!page)) {
2664 result = SCAN_PAGE_NULL;
2668 /* TODO: teach khugepaged to collapse THP mapped with pte */
2669 if (PageCompound(page)) {
2670 result = SCAN_PAGE_COMPOUND;
2675 * Record which node the original page is from and save this
2676 * information to khugepaged_node_load[].
2677 * Khupaged will allocate hugepage from the node has the max
2680 node = page_to_nid(page);
2681 if (khugepaged_scan_abort(node)) {
2682 result = SCAN_SCAN_ABORT;
2685 khugepaged_node_load[node]++;
2686 if (!PageLRU(page)) {
2687 result = SCAN_PAGE_LRU;
2690 if (PageLocked(page)) {
2691 result = SCAN_PAGE_LOCK;
2694 if (!PageAnon(page)) {
2695 result = SCAN_PAGE_ANON;
2700 * cannot use mapcount: can't collapse if there's a gup pin.
2701 * The page must only be referenced by the scanned process
2702 * and page swap cache.
2704 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2705 result = SCAN_PAGE_COUNT;
2708 if (pte_young(pteval) ||
2709 page_is_young(page) || PageReferenced(page) ||
2710 mmu_notifier_test_young(vma->vm_mm, address))
2715 result = SCAN_SUCCEED;
2718 result = SCAN_NO_REFERENCED_PAGE;
2721 result = SCAN_PAGE_RO;
2724 pte_unmap_unlock(pte, ptl);
2726 node = khugepaged_find_target_node();
2727 /* collapse_huge_page will return with the mmap_sem released */
2728 collapse_huge_page(mm, address, hpage, vma, node);
2731 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
2732 none_or_zero, result, unmapped);
2736 static void collect_mm_slot(struct mm_slot *mm_slot)
2738 struct mm_struct *mm = mm_slot->mm;
2740 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2742 if (khugepaged_test_exit(mm)) {
2744 hash_del(&mm_slot->hash);
2745 list_del(&mm_slot->mm_node);
2748 * Not strictly needed because the mm exited already.
2750 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2753 /* khugepaged_mm_lock actually not necessary for the below */
2754 free_mm_slot(mm_slot);
2759 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2760 struct page **hpage)
2761 __releases(&khugepaged_mm_lock)
2762 __acquires(&khugepaged_mm_lock)
2764 struct mm_slot *mm_slot;
2765 struct mm_struct *mm;
2766 struct vm_area_struct *vma;
2770 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2772 if (khugepaged_scan.mm_slot)
2773 mm_slot = khugepaged_scan.mm_slot;
2775 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2776 struct mm_slot, mm_node);
2777 khugepaged_scan.address = 0;
2778 khugepaged_scan.mm_slot = mm_slot;
2780 spin_unlock(&khugepaged_mm_lock);
2783 down_read(&mm->mmap_sem);
2784 if (unlikely(khugepaged_test_exit(mm)))
2787 vma = find_vma(mm, khugepaged_scan.address);
2790 for (; vma; vma = vma->vm_next) {
2791 unsigned long hstart, hend;
2794 if (unlikely(khugepaged_test_exit(mm))) {
2798 if (!hugepage_vma_check(vma)) {
2803 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2804 hend = vma->vm_end & HPAGE_PMD_MASK;
2807 if (khugepaged_scan.address > hend)
2809 if (khugepaged_scan.address < hstart)
2810 khugepaged_scan.address = hstart;
2811 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2813 while (khugepaged_scan.address < hend) {
2816 if (unlikely(khugepaged_test_exit(mm)))
2817 goto breakouterloop;
2819 VM_BUG_ON(khugepaged_scan.address < hstart ||
2820 khugepaged_scan.address + HPAGE_PMD_SIZE >
2822 ret = khugepaged_scan_pmd(mm, vma,
2823 khugepaged_scan.address,
2825 /* move to next address */
2826 khugepaged_scan.address += HPAGE_PMD_SIZE;
2827 progress += HPAGE_PMD_NR;
2829 /* we released mmap_sem so break loop */
2830 goto breakouterloop_mmap_sem;
2831 if (progress >= pages)
2832 goto breakouterloop;
2836 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2837 breakouterloop_mmap_sem:
2839 spin_lock(&khugepaged_mm_lock);
2840 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2842 * Release the current mm_slot if this mm is about to die, or
2843 * if we scanned all vmas of this mm.
2845 if (khugepaged_test_exit(mm) || !vma) {
2847 * Make sure that if mm_users is reaching zero while
2848 * khugepaged runs here, khugepaged_exit will find
2849 * mm_slot not pointing to the exiting mm.
2851 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2852 khugepaged_scan.mm_slot = list_entry(
2853 mm_slot->mm_node.next,
2854 struct mm_slot, mm_node);
2855 khugepaged_scan.address = 0;
2857 khugepaged_scan.mm_slot = NULL;
2858 khugepaged_full_scans++;
2861 collect_mm_slot(mm_slot);
2867 static int khugepaged_has_work(void)
2869 return !list_empty(&khugepaged_scan.mm_head) &&
2870 khugepaged_enabled();
2873 static int khugepaged_wait_event(void)
2875 return !list_empty(&khugepaged_scan.mm_head) ||
2876 kthread_should_stop();
2879 static void khugepaged_do_scan(void)
2881 struct page *hpage = NULL;
2882 unsigned int progress = 0, pass_through_head = 0;
2883 unsigned int pages = khugepaged_pages_to_scan;
2886 barrier(); /* write khugepaged_pages_to_scan to local stack */
2888 while (progress < pages) {
2889 if (!khugepaged_prealloc_page(&hpage, &wait))
2894 if (unlikely(kthread_should_stop() || try_to_freeze()))
2897 spin_lock(&khugepaged_mm_lock);
2898 if (!khugepaged_scan.mm_slot)
2899 pass_through_head++;
2900 if (khugepaged_has_work() &&
2901 pass_through_head < 2)
2902 progress += khugepaged_scan_mm_slot(pages - progress,
2906 spin_unlock(&khugepaged_mm_lock);
2909 if (!IS_ERR_OR_NULL(hpage))
2913 static bool khugepaged_should_wakeup(void)
2915 return kthread_should_stop() ||
2916 time_after_eq(jiffies, khugepaged_sleep_expire);
2919 static void khugepaged_wait_work(void)
2921 if (khugepaged_has_work()) {
2922 const unsigned long scan_sleep_jiffies =
2923 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
2925 if (!scan_sleep_jiffies)
2928 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
2929 wait_event_freezable_timeout(khugepaged_wait,
2930 khugepaged_should_wakeup(),
2931 scan_sleep_jiffies);
2935 if (khugepaged_enabled())
2936 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2939 static int khugepaged(void *none)
2941 struct mm_slot *mm_slot;
2944 set_user_nice(current, MAX_NICE);
2946 while (!kthread_should_stop()) {
2947 khugepaged_do_scan();
2948 khugepaged_wait_work();
2951 spin_lock(&khugepaged_mm_lock);
2952 mm_slot = khugepaged_scan.mm_slot;
2953 khugepaged_scan.mm_slot = NULL;
2955 collect_mm_slot(mm_slot);
2956 spin_unlock(&khugepaged_mm_lock);
2960 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2961 unsigned long haddr, pmd_t *pmd)
2963 struct mm_struct *mm = vma->vm_mm;
2968 /* leave pmd empty until pte is filled */
2969 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2971 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2972 pmd_populate(mm, &_pmd, pgtable);
2974 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2976 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2977 entry = pte_mkspecial(entry);
2978 pte = pte_offset_map(&_pmd, haddr);
2979 VM_BUG_ON(!pte_none(*pte));
2980 set_pte_at(mm, haddr, pte, entry);
2983 smp_wmb(); /* make pte visible before pmd */
2984 pmd_populate(mm, pmd, pgtable);
2985 put_huge_zero_page();
2988 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2989 unsigned long haddr, bool freeze)
2991 struct mm_struct *mm = vma->vm_mm;
2995 bool young, write, dirty;
2999 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
3000 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
3001 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
3002 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
3004 count_vm_event(THP_SPLIT_PMD);
3006 if (!vma_is_anonymous(vma)) {
3007 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
3008 if (is_huge_zero_pmd(_pmd))
3009 put_huge_zero_page();
3010 if (vma_is_dax(vma))
3012 page = pmd_page(_pmd);
3013 if (!PageReferenced(page) && pmd_young(_pmd))
3014 SetPageReferenced(page);
3015 page_remove_rmap(page, true);
3017 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
3019 } else if (is_huge_zero_pmd(*pmd)) {
3020 return __split_huge_zero_page_pmd(vma, haddr, pmd);
3023 page = pmd_page(*pmd);
3024 VM_BUG_ON_PAGE(!page_count(page), page);
3025 page_ref_add(page, HPAGE_PMD_NR - 1);
3026 write = pmd_write(*pmd);
3027 young = pmd_young(*pmd);
3028 dirty = pmd_dirty(*pmd);
3030 pmdp_huge_split_prepare(vma, haddr, pmd);
3031 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
3032 pmd_populate(mm, &_pmd, pgtable);
3034 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
3037 * Note that NUMA hinting access restrictions are not
3038 * transferred to avoid any possibility of altering
3039 * permissions across VMAs.
3042 swp_entry_t swp_entry;
3043 swp_entry = make_migration_entry(page + i, write);
3044 entry = swp_entry_to_pte(swp_entry);
3046 entry = mk_pte(page + i, vma->vm_page_prot);
3047 entry = maybe_mkwrite(entry, vma);
3049 entry = pte_wrprotect(entry);
3051 entry = pte_mkold(entry);
3054 SetPageDirty(page + i);
3055 pte = pte_offset_map(&_pmd, addr);
3056 BUG_ON(!pte_none(*pte));
3057 set_pte_at(mm, addr, pte, entry);
3058 atomic_inc(&page[i]._mapcount);
3063 * Set PG_double_map before dropping compound_mapcount to avoid
3064 * false-negative page_mapped().
3066 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
3067 for (i = 0; i < HPAGE_PMD_NR; i++)
3068 atomic_inc(&page[i]._mapcount);
3071 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
3072 /* Last compound_mapcount is gone. */
3073 __dec_zone_page_state(page, NR_ANON_THPS);
3074 if (TestClearPageDoubleMap(page)) {
3075 /* No need in mapcount reference anymore */
3076 for (i = 0; i < HPAGE_PMD_NR; i++)
3077 atomic_dec(&page[i]._mapcount);
3081 smp_wmb(); /* make pte visible before pmd */
3083 * Up to this point the pmd is present and huge and userland has the
3084 * whole access to the hugepage during the split (which happens in
3085 * place). If we overwrite the pmd with the not-huge version pointing
3086 * to the pte here (which of course we could if all CPUs were bug
3087 * free), userland could trigger a small page size TLB miss on the
3088 * small sized TLB while the hugepage TLB entry is still established in
3089 * the huge TLB. Some CPU doesn't like that.
3090 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
3091 * 383 on page 93. Intel should be safe but is also warns that it's
3092 * only safe if the permission and cache attributes of the two entries
3093 * loaded in the two TLB is identical (which should be the case here).
3094 * But it is generally safer to never allow small and huge TLB entries
3095 * for the same virtual address to be loaded simultaneously. So instead
3096 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
3097 * current pmd notpresent (atomically because here the pmd_trans_huge
3098 * and pmd_trans_splitting must remain set at all times on the pmd
3099 * until the split is complete for this pmd), then we flush the SMP TLB
3100 * and finally we write the non-huge version of the pmd entry with
3103 pmdp_invalidate(vma, haddr, pmd);
3104 pmd_populate(mm, pmd, pgtable);
3107 for (i = 0; i < HPAGE_PMD_NR; i++) {
3108 page_remove_rmap(page + i, false);
3114 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
3115 unsigned long address, bool freeze, struct page *page)
3118 struct mm_struct *mm = vma->vm_mm;
3119 unsigned long haddr = address & HPAGE_PMD_MASK;
3121 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
3122 ptl = pmd_lock(mm, pmd);
3125 * If caller asks to setup a migration entries, we need a page to check
3126 * pmd against. Otherwise we can end up replacing wrong page.
3128 VM_BUG_ON(freeze && !page);
3129 if (page && page != pmd_page(*pmd))
3132 if (pmd_trans_huge(*pmd)) {
3133 page = pmd_page(*pmd);
3134 if (PageMlocked(page))
3135 clear_page_mlock(page);
3136 } else if (!pmd_devmap(*pmd))
3138 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
3141 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
3144 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
3145 bool freeze, struct page *page)
3151 pgd = pgd_offset(vma->vm_mm, address);
3152 if (!pgd_present(*pgd))
3155 pud = pud_offset(pgd, address);
3156 if (!pud_present(*pud))
3159 pmd = pmd_offset(pud, address);
3161 __split_huge_pmd(vma, pmd, address, freeze, page);
3164 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3165 unsigned long start,
3170 * If the new start address isn't hpage aligned and it could
3171 * previously contain an hugepage: check if we need to split
3174 if (start & ~HPAGE_PMD_MASK &&
3175 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3176 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3177 split_huge_pmd_address(vma, start, false, NULL);
3180 * If the new end address isn't hpage aligned and it could
3181 * previously contain an hugepage: check if we need to split
3184 if (end & ~HPAGE_PMD_MASK &&
3185 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3186 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3187 split_huge_pmd_address(vma, end, false, NULL);
3190 * If we're also updating the vma->vm_next->vm_start, if the new
3191 * vm_next->vm_start isn't page aligned and it could previously
3192 * contain an hugepage: check if we need to split an huge pmd.
3194 if (adjust_next > 0) {
3195 struct vm_area_struct *next = vma->vm_next;
3196 unsigned long nstart = next->vm_start;
3197 nstart += adjust_next << PAGE_SHIFT;
3198 if (nstart & ~HPAGE_PMD_MASK &&
3199 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3200 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3201 split_huge_pmd_address(next, nstart, false, NULL);
3205 static void freeze_page(struct page *page)
3207 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
3211 VM_BUG_ON_PAGE(!PageHead(page), page);
3214 ttu_flags |= TTU_MIGRATION;
3216 /* We only need TTU_SPLIT_HUGE_PMD once */
3217 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
3218 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) {
3219 /* Cut short if the page is unmapped */
3220 if (page_count(page) == 1)
3223 ret = try_to_unmap(page + i, ttu_flags);
3225 VM_BUG_ON_PAGE(ret, page + i - 1);
3228 static void unfreeze_page(struct page *page)
3232 for (i = 0; i < HPAGE_PMD_NR; i++)
3233 remove_migration_ptes(page + i, page + i, true);
3236 static void __split_huge_page_tail(struct page *head, int tail,
3237 struct lruvec *lruvec, struct list_head *list)
3239 struct page *page_tail = head + tail;
3241 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
3242 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
3245 * tail_page->_refcount is zero and not changing from under us. But
3246 * get_page_unless_zero() may be running from under us on the
3247 * tail_page. If we used atomic_set() below instead of atomic_inc() or
3248 * atomic_add(), we would then run atomic_set() concurrently with
3249 * get_page_unless_zero(), and atomic_set() is implemented in C not
3250 * using locked ops. spin_unlock on x86 sometime uses locked ops
3251 * because of PPro errata 66, 92, so unless somebody can guarantee
3252 * atomic_set() here would be safe on all archs (and not only on x86),
3253 * it's safer to use atomic_inc()/atomic_add().
3255 if (PageAnon(head)) {
3256 page_ref_inc(page_tail);
3258 /* Additional pin to radix tree */
3259 page_ref_add(page_tail, 2);
3262 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3263 page_tail->flags |= (head->flags &
3264 ((1L << PG_referenced) |
3265 (1L << PG_swapbacked) |
3266 (1L << PG_mlocked) |
3267 (1L << PG_uptodate) |
3270 (1L << PG_unevictable) |
3274 * After clearing PageTail the gup refcount can be released.
3275 * Page flags also must be visible before we make the page non-compound.
3279 clear_compound_head(page_tail);
3281 if (page_is_young(head))
3282 set_page_young(page_tail);
3283 if (page_is_idle(head))
3284 set_page_idle(page_tail);
3286 /* ->mapping in first tail page is compound_mapcount */
3287 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3289 page_tail->mapping = head->mapping;
3291 page_tail->index = head->index + tail;
3292 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3293 lru_add_page_tail(head, page_tail, lruvec, list);
3296 static void __split_huge_page(struct page *page, struct list_head *list,
3297 unsigned long flags)
3299 struct page *head = compound_head(page);
3300 struct zone *zone = page_zone(head);
3301 struct lruvec *lruvec;
3305 lruvec = mem_cgroup_page_lruvec(head, zone);
3307 /* complete memcg works before add pages to LRU */
3308 mem_cgroup_split_huge_fixup(head);
3310 if (!PageAnon(page))
3311 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
3313 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
3314 __split_huge_page_tail(head, i, lruvec, list);
3315 /* Some pages can be beyond i_size: drop them from page cache */
3316 if (head[i].index >= end) {
3317 __ClearPageDirty(head + i);
3318 __delete_from_page_cache(head + i, NULL);
3319 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
3320 shmem_uncharge(head->mapping->host, 1);
3325 ClearPageCompound(head);
3326 /* See comment in __split_huge_page_tail() */
3327 if (PageAnon(head)) {
3330 /* Additional pin to radix tree */
3331 page_ref_add(head, 2);
3332 spin_unlock(&head->mapping->tree_lock);
3335 spin_unlock_irqrestore(&page_zone(head)->lru_lock, flags);
3337 unfreeze_page(head);
3339 for (i = 0; i < HPAGE_PMD_NR; i++) {
3340 struct page *subpage = head + i;
3341 if (subpage == page)
3343 unlock_page(subpage);
3346 * Subpages may be freed if there wasn't any mapping
3347 * like if add_to_swap() is running on a lru page that
3348 * had its mapping zapped. And freeing these pages
3349 * requires taking the lru_lock so we do the put_page
3350 * of the tail pages after the split is complete.
3356 int total_mapcount(struct page *page)
3358 int i, compound, ret;
3360 VM_BUG_ON_PAGE(PageTail(page), page);
3362 if (likely(!PageCompound(page)))
3363 return atomic_read(&page->_mapcount) + 1;
3365 compound = compound_mapcount(page);
3369 for (i = 0; i < HPAGE_PMD_NR; i++)
3370 ret += atomic_read(&page[i]._mapcount) + 1;
3371 /* File pages has compound_mapcount included in _mapcount */
3372 if (!PageAnon(page))
3373 return ret - compound * HPAGE_PMD_NR;
3374 if (PageDoubleMap(page))
3375 ret -= HPAGE_PMD_NR;
3380 * This calculates accurately how many mappings a transparent hugepage
3381 * has (unlike page_mapcount() which isn't fully accurate). This full
3382 * accuracy is primarily needed to know if copy-on-write faults can
3383 * reuse the page and change the mapping to read-write instead of
3384 * copying them. At the same time this returns the total_mapcount too.
3386 * The function returns the highest mapcount any one of the subpages
3387 * has. If the return value is one, even if different processes are
3388 * mapping different subpages of the transparent hugepage, they can
3389 * all reuse it, because each process is reusing a different subpage.
3391 * The total_mapcount is instead counting all virtual mappings of the
3392 * subpages. If the total_mapcount is equal to "one", it tells the
3393 * caller all mappings belong to the same "mm" and in turn the
3394 * anon_vma of the transparent hugepage can become the vma->anon_vma
3395 * local one as no other process may be mapping any of the subpages.
3397 * It would be more accurate to replace page_mapcount() with
3398 * page_trans_huge_mapcount(), however we only use
3399 * page_trans_huge_mapcount() in the copy-on-write faults where we
3400 * need full accuracy to avoid breaking page pinning, because
3401 * page_trans_huge_mapcount() is slower than page_mapcount().
3403 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
3405 int i, ret, _total_mapcount, mapcount;
3407 /* hugetlbfs shouldn't call it */
3408 VM_BUG_ON_PAGE(PageHuge(page), page);
3410 if (likely(!PageTransCompound(page))) {
3411 mapcount = atomic_read(&page->_mapcount) + 1;
3413 *total_mapcount = mapcount;
3417 page = compound_head(page);
3419 _total_mapcount = ret = 0;
3420 for (i = 0; i < HPAGE_PMD_NR; i++) {
3421 mapcount = atomic_read(&page[i]._mapcount) + 1;
3422 ret = max(ret, mapcount);
3423 _total_mapcount += mapcount;
3425 if (PageDoubleMap(page)) {
3427 _total_mapcount -= HPAGE_PMD_NR;
3429 mapcount = compound_mapcount(page);
3431 _total_mapcount += mapcount;
3433 *total_mapcount = _total_mapcount;
3438 * This function splits huge page into normal pages. @page can point to any
3439 * subpage of huge page to split. Split doesn't change the position of @page.
3441 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3442 * The huge page must be locked.
3444 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3446 * Both head page and tail pages will inherit mapping, flags, and so on from
3449 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3450 * they are not mapped.
3452 * Returns 0 if the hugepage is split successfully.
3453 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3456 int split_huge_page_to_list(struct page *page, struct list_head *list)
3458 struct page *head = compound_head(page);
3459 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
3460 struct anon_vma *anon_vma = NULL;
3461 struct address_space *mapping = NULL;
3462 int count, mapcount, extra_pins, ret;
3464 unsigned long flags;
3466 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3467 VM_BUG_ON_PAGE(!PageLocked(page), page);
3468 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3469 VM_BUG_ON_PAGE(!PageCompound(page), page);
3471 if (PageAnon(head)) {
3473 * The caller does not necessarily hold an mmap_sem that would
3474 * prevent the anon_vma disappearing so we first we take a
3475 * reference to it and then lock the anon_vma for write. This
3476 * is similar to page_lock_anon_vma_read except the write lock
3477 * is taken to serialise against parallel split or collapse
3480 anon_vma = page_get_anon_vma(head);
3487 anon_vma_lock_write(anon_vma);
3489 mapping = head->mapping;
3497 /* Addidional pins from radix tree */
3498 extra_pins = HPAGE_PMD_NR;
3500 i_mmap_lock_read(mapping);
3504 * Racy check if we can split the page, before freeze_page() will
3507 if (total_mapcount(head) != page_count(head) - extra_pins - 1) {
3512 mlocked = PageMlocked(page);
3514 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3516 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3520 /* prevent PageLRU to go away from under us, and freeze lru stats */
3521 spin_lock_irqsave(&page_zone(head)->lru_lock, flags);
3526 spin_lock(&mapping->tree_lock);
3527 pslot = radix_tree_lookup_slot(&mapping->page_tree,
3530 * Check if the head page is present in radix tree.
3531 * We assume all tail are present too, if head is there.
3533 if (radix_tree_deref_slot_protected(pslot,
3534 &mapping->tree_lock) != head)
3538 /* Prevent deferred_split_scan() touching ->_refcount */
3539 spin_lock(&pgdata->split_queue_lock);
3540 count = page_count(head);
3541 mapcount = total_mapcount(head);
3542 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
3543 if (!list_empty(page_deferred_list(head))) {
3544 pgdata->split_queue_len--;
3545 list_del(page_deferred_list(head));
3548 __dec_zone_page_state(page, NR_SHMEM_THPS);
3549 spin_unlock(&pgdata->split_queue_lock);
3550 __split_huge_page(page, list, flags);
3553 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
3554 pr_alert("total_mapcount: %u, page_count(): %u\n",
3557 dump_page(head, NULL);
3558 dump_page(page, "total_mapcount(head) > 0");
3561 spin_unlock(&pgdata->split_queue_lock);
3563 spin_unlock(&mapping->tree_lock);
3564 spin_unlock_irqrestore(&page_zone(head)->lru_lock, flags);
3565 unfreeze_page(head);
3571 anon_vma_unlock_write(anon_vma);
3572 put_anon_vma(anon_vma);
3575 i_mmap_unlock_read(mapping);
3577 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3581 void free_transhuge_page(struct page *page)
3583 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3584 unsigned long flags;
3586 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3587 if (!list_empty(page_deferred_list(page))) {
3588 pgdata->split_queue_len--;
3589 list_del(page_deferred_list(page));
3591 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3592 free_compound_page(page);
3595 void deferred_split_huge_page(struct page *page)
3597 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3598 unsigned long flags;
3600 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3602 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3603 if (list_empty(page_deferred_list(page))) {
3604 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
3605 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
3606 pgdata->split_queue_len++;
3608 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3611 static unsigned long deferred_split_count(struct shrinker *shrink,
3612 struct shrink_control *sc)
3614 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3615 return ACCESS_ONCE(pgdata->split_queue_len);
3618 static unsigned long deferred_split_scan(struct shrinker *shrink,
3619 struct shrink_control *sc)
3621 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3622 unsigned long flags;
3623 LIST_HEAD(list), *pos, *next;
3627 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3628 /* Take pin on all head pages to avoid freeing them under us */
3629 list_for_each_safe(pos, next, &pgdata->split_queue) {
3630 page = list_entry((void *)pos, struct page, mapping);
3631 page = compound_head(page);
3632 if (get_page_unless_zero(page)) {
3633 list_move(page_deferred_list(page), &list);
3635 /* We lost race with put_compound_page() */
3636 list_del_init(page_deferred_list(page));
3637 pgdata->split_queue_len--;
3639 if (!--sc->nr_to_scan)
3642 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3644 list_for_each_safe(pos, next, &list) {
3645 page = list_entry((void *)pos, struct page, mapping);
3647 /* split_huge_page() removes page from list on success */
3648 if (!split_huge_page(page))
3654 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3655 list_splice_tail(&list, &pgdata->split_queue);
3656 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3659 * Stop shrinker if we didn't split any page, but the queue is empty.
3660 * This can happen if pages were freed under us.
3662 if (!split && list_empty(&pgdata->split_queue))
3667 static struct shrinker deferred_split_shrinker = {
3668 .count_objects = deferred_split_count,
3669 .scan_objects = deferred_split_scan,
3670 .seeks = DEFAULT_SEEKS,
3671 .flags = SHRINKER_NUMA_AWARE,
3674 #ifdef CONFIG_DEBUG_FS
3675 static int split_huge_pages_set(void *data, u64 val)
3679 unsigned long pfn, max_zone_pfn;
3680 unsigned long total = 0, split = 0;
3685 for_each_populated_zone(zone) {
3686 max_zone_pfn = zone_end_pfn(zone);
3687 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3688 if (!pfn_valid(pfn))
3691 page = pfn_to_page(pfn);
3692 if (!get_page_unless_zero(page))
3695 if (zone != page_zone(page))
3698 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
3703 if (!split_huge_page(page))
3711 pr_info("%lu of %lu THP split\n", split, total);
3715 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3718 static int __init split_huge_pages_debugfs(void)
3722 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3723 &split_huge_pages_fops);
3725 pr_warn("Failed to create split_huge_pages in debugfs");
3728 late_initcall(split_huge_pages_debugfs);