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/mman.h>
25 #include <linux/pagemap.h>
26 #include <linux/debugfs.h>
27 #include <linux/migrate.h>
28 #include <linux/hashtable.h>
29 #include <linux/userfaultfd_k.h>
30 #include <linux/page_idle.h>
33 #include <asm/pgalloc.h>
43 SCAN_NO_REFERENCED_PAGE
,
57 SCAN_ALLOC_HUGE_PAGE_FAIL
,
58 SCAN_CGROUP_CHARGE_FAIL
61 #define CREATE_TRACE_POINTS
62 #include <trace/events/huge_memory.h>
65 * By default transparent hugepage support is disabled in order that avoid
66 * to risk increase the memory footprint of applications without a guaranteed
67 * benefit. When transparent hugepage support is enabled, is for all mappings,
68 * and khugepaged scans all mappings.
69 * Defrag is invoked by khugepaged hugepage allocations and by page faults
70 * for all hugepage allocations.
72 unsigned long transparent_hugepage_flags __read_mostly
=
73 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
74 (1<<TRANSPARENT_HUGEPAGE_FLAG
)|
76 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
77 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
)|
79 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
)|
80 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
)|
81 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
83 /* default scan 8*512 pte (or vmas) every 30 second */
84 static unsigned int khugepaged_pages_to_scan __read_mostly
= HPAGE_PMD_NR
*8;
85 static unsigned int khugepaged_pages_collapsed
;
86 static unsigned int khugepaged_full_scans
;
87 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly
= 10000;
88 /* during fragmentation poll the hugepage allocator once every minute */
89 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly
= 60000;
90 static struct task_struct
*khugepaged_thread __read_mostly
;
91 static DEFINE_MUTEX(khugepaged_mutex
);
92 static DEFINE_SPINLOCK(khugepaged_mm_lock
);
93 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait
);
95 * default collapse hugepages if there is at least one pte mapped like
96 * it would have happened if the vma was large enough during page
99 static unsigned int khugepaged_max_ptes_none __read_mostly
= HPAGE_PMD_NR
-1;
101 static int khugepaged(void *none
);
102 static int khugepaged_slab_init(void);
103 static void khugepaged_slab_exit(void);
105 #define MM_SLOTS_HASH_BITS 10
106 static __read_mostly
DEFINE_HASHTABLE(mm_slots_hash
, MM_SLOTS_HASH_BITS
);
108 static struct kmem_cache
*mm_slot_cache __read_mostly
;
111 * struct mm_slot - hash lookup from mm to mm_slot
112 * @hash: hash collision list
113 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
114 * @mm: the mm that this information is valid for
117 struct hlist_node hash
;
118 struct list_head mm_node
;
119 struct mm_struct
*mm
;
123 * struct khugepaged_scan - cursor for scanning
124 * @mm_head: the head of the mm list to scan
125 * @mm_slot: the current mm_slot we are scanning
126 * @address: the next address inside that to be scanned
128 * There is only the one khugepaged_scan instance of this cursor structure.
130 struct khugepaged_scan
{
131 struct list_head mm_head
;
132 struct mm_slot
*mm_slot
;
133 unsigned long address
;
135 static struct khugepaged_scan khugepaged_scan
= {
136 .mm_head
= LIST_HEAD_INIT(khugepaged_scan
.mm_head
),
139 static DEFINE_SPINLOCK(split_queue_lock
);
140 static LIST_HEAD(split_queue
);
141 static unsigned long split_queue_len
;
142 static struct shrinker deferred_split_shrinker
;
144 static void set_recommended_min_free_kbytes(void)
148 unsigned long recommended_min
;
150 for_each_populated_zone(zone
)
153 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
154 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
157 * Make sure that on average at least two pageblocks are almost free
158 * of another type, one for a migratetype to fall back to and a
159 * second to avoid subsequent fallbacks of other types There are 3
160 * MIGRATE_TYPES we care about.
162 recommended_min
+= pageblock_nr_pages
* nr_zones
*
163 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
165 /* don't ever allow to reserve more than 5% of the lowmem */
166 recommended_min
= min(recommended_min
,
167 (unsigned long) nr_free_buffer_pages() / 20);
168 recommended_min
<<= (PAGE_SHIFT
-10);
170 if (recommended_min
> min_free_kbytes
) {
171 if (user_min_free_kbytes
>= 0)
172 pr_info("raising min_free_kbytes from %d to %lu "
173 "to help transparent hugepage allocations\n",
174 min_free_kbytes
, recommended_min
);
176 min_free_kbytes
= recommended_min
;
178 setup_per_zone_wmarks();
181 static int start_stop_khugepaged(void)
184 if (khugepaged_enabled()) {
185 if (!khugepaged_thread
)
186 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
188 if (IS_ERR(khugepaged_thread
)) {
189 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
190 err
= PTR_ERR(khugepaged_thread
);
191 khugepaged_thread
= NULL
;
195 if (!list_empty(&khugepaged_scan
.mm_head
))
196 wake_up_interruptible(&khugepaged_wait
);
198 set_recommended_min_free_kbytes();
199 } else if (khugepaged_thread
) {
200 kthread_stop(khugepaged_thread
);
201 khugepaged_thread
= NULL
;
207 static atomic_t huge_zero_refcount
;
208 struct page
*huge_zero_page __read_mostly
;
210 struct page
*get_huge_zero_page(void)
212 struct page
*zero_page
;
214 if (likely(atomic_inc_not_zero(&huge_zero_refcount
)))
215 return READ_ONCE(huge_zero_page
);
217 zero_page
= alloc_pages((GFP_TRANSHUGE
| __GFP_ZERO
) & ~__GFP_MOVABLE
,
220 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED
);
223 count_vm_event(THP_ZERO_PAGE_ALLOC
);
225 if (cmpxchg(&huge_zero_page
, NULL
, zero_page
)) {
227 __free_pages(zero_page
, compound_order(zero_page
));
231 /* We take additional reference here. It will be put back by shrinker */
232 atomic_set(&huge_zero_refcount
, 2);
234 return READ_ONCE(huge_zero_page
);
237 static void put_huge_zero_page(void)
240 * Counter should never go to zero here. Only shrinker can put
243 BUG_ON(atomic_dec_and_test(&huge_zero_refcount
));
246 static unsigned long shrink_huge_zero_page_count(struct shrinker
*shrink
,
247 struct shrink_control
*sc
)
249 /* we can free zero page only if last reference remains */
250 return atomic_read(&huge_zero_refcount
) == 1 ? HPAGE_PMD_NR
: 0;
253 static unsigned long shrink_huge_zero_page_scan(struct shrinker
*shrink
,
254 struct shrink_control
*sc
)
256 if (atomic_cmpxchg(&huge_zero_refcount
, 1, 0) == 1) {
257 struct page
*zero_page
= xchg(&huge_zero_page
, NULL
);
258 BUG_ON(zero_page
== NULL
);
259 __free_pages(zero_page
, compound_order(zero_page
));
266 static struct shrinker huge_zero_page_shrinker
= {
267 .count_objects
= shrink_huge_zero_page_count
,
268 .scan_objects
= shrink_huge_zero_page_scan
,
269 .seeks
= DEFAULT_SEEKS
,
274 static ssize_t
double_flag_show(struct kobject
*kobj
,
275 struct kobj_attribute
*attr
, char *buf
,
276 enum transparent_hugepage_flag enabled
,
277 enum transparent_hugepage_flag req_madv
)
279 if (test_bit(enabled
, &transparent_hugepage_flags
)) {
280 VM_BUG_ON(test_bit(req_madv
, &transparent_hugepage_flags
));
281 return sprintf(buf
, "[always] madvise never\n");
282 } else if (test_bit(req_madv
, &transparent_hugepage_flags
))
283 return sprintf(buf
, "always [madvise] never\n");
285 return sprintf(buf
, "always madvise [never]\n");
287 static ssize_t
double_flag_store(struct kobject
*kobj
,
288 struct kobj_attribute
*attr
,
289 const char *buf
, size_t count
,
290 enum transparent_hugepage_flag enabled
,
291 enum transparent_hugepage_flag req_madv
)
293 if (!memcmp("always", buf
,
294 min(sizeof("always")-1, count
))) {
295 set_bit(enabled
, &transparent_hugepage_flags
);
296 clear_bit(req_madv
, &transparent_hugepage_flags
);
297 } else if (!memcmp("madvise", buf
,
298 min(sizeof("madvise")-1, count
))) {
299 clear_bit(enabled
, &transparent_hugepage_flags
);
300 set_bit(req_madv
, &transparent_hugepage_flags
);
301 } else if (!memcmp("never", buf
,
302 min(sizeof("never")-1, count
))) {
303 clear_bit(enabled
, &transparent_hugepage_flags
);
304 clear_bit(req_madv
, &transparent_hugepage_flags
);
311 static ssize_t
enabled_show(struct kobject
*kobj
,
312 struct kobj_attribute
*attr
, char *buf
)
314 return double_flag_show(kobj
, attr
, buf
,
315 TRANSPARENT_HUGEPAGE_FLAG
,
316 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
318 static ssize_t
enabled_store(struct kobject
*kobj
,
319 struct kobj_attribute
*attr
,
320 const char *buf
, size_t count
)
324 ret
= double_flag_store(kobj
, attr
, buf
, count
,
325 TRANSPARENT_HUGEPAGE_FLAG
,
326 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
331 mutex_lock(&khugepaged_mutex
);
332 err
= start_stop_khugepaged();
333 mutex_unlock(&khugepaged_mutex
);
341 static struct kobj_attribute enabled_attr
=
342 __ATTR(enabled
, 0644, enabled_show
, enabled_store
);
344 static ssize_t
single_flag_show(struct kobject
*kobj
,
345 struct kobj_attribute
*attr
, char *buf
,
346 enum transparent_hugepage_flag flag
)
348 return sprintf(buf
, "%d\n",
349 !!test_bit(flag
, &transparent_hugepage_flags
));
352 static ssize_t
single_flag_store(struct kobject
*kobj
,
353 struct kobj_attribute
*attr
,
354 const char *buf
, size_t count
,
355 enum transparent_hugepage_flag flag
)
360 ret
= kstrtoul(buf
, 10, &value
);
367 set_bit(flag
, &transparent_hugepage_flags
);
369 clear_bit(flag
, &transparent_hugepage_flags
);
375 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
376 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
377 * memory just to allocate one more hugepage.
379 static ssize_t
defrag_show(struct kobject
*kobj
,
380 struct kobj_attribute
*attr
, char *buf
)
382 return double_flag_show(kobj
, attr
, buf
,
383 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
,
384 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
386 static ssize_t
defrag_store(struct kobject
*kobj
,
387 struct kobj_attribute
*attr
,
388 const char *buf
, size_t count
)
390 return double_flag_store(kobj
, attr
, buf
, count
,
391 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
,
392 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
394 static struct kobj_attribute defrag_attr
=
395 __ATTR(defrag
, 0644, defrag_show
, defrag_store
);
397 static ssize_t
use_zero_page_show(struct kobject
*kobj
,
398 struct kobj_attribute
*attr
, char *buf
)
400 return single_flag_show(kobj
, attr
, buf
,
401 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
403 static ssize_t
use_zero_page_store(struct kobject
*kobj
,
404 struct kobj_attribute
*attr
, const char *buf
, size_t count
)
406 return single_flag_store(kobj
, attr
, buf
, count
,
407 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
409 static struct kobj_attribute use_zero_page_attr
=
410 __ATTR(use_zero_page
, 0644, use_zero_page_show
, use_zero_page_store
);
411 #ifdef CONFIG_DEBUG_VM
412 static ssize_t
debug_cow_show(struct kobject
*kobj
,
413 struct kobj_attribute
*attr
, char *buf
)
415 return single_flag_show(kobj
, attr
, buf
,
416 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
418 static ssize_t
debug_cow_store(struct kobject
*kobj
,
419 struct kobj_attribute
*attr
,
420 const char *buf
, size_t count
)
422 return single_flag_store(kobj
, attr
, buf
, count
,
423 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
425 static struct kobj_attribute debug_cow_attr
=
426 __ATTR(debug_cow
, 0644, debug_cow_show
, debug_cow_store
);
427 #endif /* CONFIG_DEBUG_VM */
429 static struct attribute
*hugepage_attr
[] = {
432 &use_zero_page_attr
.attr
,
433 #ifdef CONFIG_DEBUG_VM
434 &debug_cow_attr
.attr
,
439 static struct attribute_group hugepage_attr_group
= {
440 .attrs
= hugepage_attr
,
443 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
444 struct kobj_attribute
*attr
,
447 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
450 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
451 struct kobj_attribute
*attr
,
452 const char *buf
, size_t count
)
457 err
= kstrtoul(buf
, 10, &msecs
);
458 if (err
|| msecs
> UINT_MAX
)
461 khugepaged_scan_sleep_millisecs
= msecs
;
462 wake_up_interruptible(&khugepaged_wait
);
466 static struct kobj_attribute scan_sleep_millisecs_attr
=
467 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
468 scan_sleep_millisecs_store
);
470 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
471 struct kobj_attribute
*attr
,
474 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
477 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
478 struct kobj_attribute
*attr
,
479 const char *buf
, size_t count
)
484 err
= kstrtoul(buf
, 10, &msecs
);
485 if (err
|| msecs
> UINT_MAX
)
488 khugepaged_alloc_sleep_millisecs
= msecs
;
489 wake_up_interruptible(&khugepaged_wait
);
493 static struct kobj_attribute alloc_sleep_millisecs_attr
=
494 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
495 alloc_sleep_millisecs_store
);
497 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
498 struct kobj_attribute
*attr
,
501 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
503 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
504 struct kobj_attribute
*attr
,
505 const char *buf
, size_t count
)
510 err
= kstrtoul(buf
, 10, &pages
);
511 if (err
|| !pages
|| pages
> UINT_MAX
)
514 khugepaged_pages_to_scan
= pages
;
518 static struct kobj_attribute pages_to_scan_attr
=
519 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
520 pages_to_scan_store
);
522 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
523 struct kobj_attribute
*attr
,
526 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
528 static struct kobj_attribute pages_collapsed_attr
=
529 __ATTR_RO(pages_collapsed
);
531 static ssize_t
full_scans_show(struct kobject
*kobj
,
532 struct kobj_attribute
*attr
,
535 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
537 static struct kobj_attribute full_scans_attr
=
538 __ATTR_RO(full_scans
);
540 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
541 struct kobj_attribute
*attr
, char *buf
)
543 return single_flag_show(kobj
, attr
, buf
,
544 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
546 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
547 struct kobj_attribute
*attr
,
548 const char *buf
, size_t count
)
550 return single_flag_store(kobj
, attr
, buf
, count
,
551 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
553 static struct kobj_attribute khugepaged_defrag_attr
=
554 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
555 khugepaged_defrag_store
);
558 * max_ptes_none controls if khugepaged should collapse hugepages over
559 * any unmapped ptes in turn potentially increasing the memory
560 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
561 * reduce the available free memory in the system as it
562 * runs. Increasing max_ptes_none will instead potentially reduce the
563 * free memory in the system during the khugepaged scan.
565 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
566 struct kobj_attribute
*attr
,
569 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
571 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
572 struct kobj_attribute
*attr
,
573 const char *buf
, size_t count
)
576 unsigned long max_ptes_none
;
578 err
= kstrtoul(buf
, 10, &max_ptes_none
);
579 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
582 khugepaged_max_ptes_none
= max_ptes_none
;
586 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
587 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
588 khugepaged_max_ptes_none_store
);
590 static struct attribute
*khugepaged_attr
[] = {
591 &khugepaged_defrag_attr
.attr
,
592 &khugepaged_max_ptes_none_attr
.attr
,
593 &pages_to_scan_attr
.attr
,
594 &pages_collapsed_attr
.attr
,
595 &full_scans_attr
.attr
,
596 &scan_sleep_millisecs_attr
.attr
,
597 &alloc_sleep_millisecs_attr
.attr
,
601 static struct attribute_group khugepaged_attr_group
= {
602 .attrs
= khugepaged_attr
,
603 .name
= "khugepaged",
606 static int __init
hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
610 *hugepage_kobj
= kobject_create_and_add("transparent_hugepage", mm_kobj
);
611 if (unlikely(!*hugepage_kobj
)) {
612 pr_err("failed to create transparent hugepage kobject\n");
616 err
= sysfs_create_group(*hugepage_kobj
, &hugepage_attr_group
);
618 pr_err("failed to register transparent hugepage group\n");
622 err
= sysfs_create_group(*hugepage_kobj
, &khugepaged_attr_group
);
624 pr_err("failed to register transparent hugepage group\n");
625 goto remove_hp_group
;
631 sysfs_remove_group(*hugepage_kobj
, &hugepage_attr_group
);
633 kobject_put(*hugepage_kobj
);
637 static void __init
hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
639 sysfs_remove_group(hugepage_kobj
, &khugepaged_attr_group
);
640 sysfs_remove_group(hugepage_kobj
, &hugepage_attr_group
);
641 kobject_put(hugepage_kobj
);
644 static inline int hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
649 static inline void hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
652 #endif /* CONFIG_SYSFS */
654 static int __init
hugepage_init(void)
657 struct kobject
*hugepage_kobj
;
659 if (!has_transparent_hugepage()) {
660 transparent_hugepage_flags
= 0;
664 err
= hugepage_init_sysfs(&hugepage_kobj
);
668 err
= khugepaged_slab_init();
672 err
= register_shrinker(&huge_zero_page_shrinker
);
674 goto err_hzp_shrinker
;
675 err
= register_shrinker(&deferred_split_shrinker
);
677 goto err_split_shrinker
;
680 * By default disable transparent hugepages on smaller systems,
681 * where the extra memory used could hurt more than TLB overhead
682 * is likely to save. The admin can still enable it through /sys.
684 if (totalram_pages
< (512 << (20 - PAGE_SHIFT
))) {
685 transparent_hugepage_flags
= 0;
689 err
= start_stop_khugepaged();
695 unregister_shrinker(&deferred_split_shrinker
);
697 unregister_shrinker(&huge_zero_page_shrinker
);
699 khugepaged_slab_exit();
701 hugepage_exit_sysfs(hugepage_kobj
);
705 subsys_initcall(hugepage_init
);
707 static int __init
setup_transparent_hugepage(char *str
)
712 if (!strcmp(str
, "always")) {
713 set_bit(TRANSPARENT_HUGEPAGE_FLAG
,
714 &transparent_hugepage_flags
);
715 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
716 &transparent_hugepage_flags
);
718 } else if (!strcmp(str
, "madvise")) {
719 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
720 &transparent_hugepage_flags
);
721 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
722 &transparent_hugepage_flags
);
724 } else if (!strcmp(str
, "never")) {
725 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
726 &transparent_hugepage_flags
);
727 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
728 &transparent_hugepage_flags
);
733 pr_warn("transparent_hugepage= cannot parse, ignored\n");
736 __setup("transparent_hugepage=", setup_transparent_hugepage
);
738 pmd_t
maybe_pmd_mkwrite(pmd_t pmd
, struct vm_area_struct
*vma
)
740 if (likely(vma
->vm_flags
& VM_WRITE
))
741 pmd
= pmd_mkwrite(pmd
);
745 static inline pmd_t
mk_huge_pmd(struct page
*page
, pgprot_t prot
)
748 entry
= mk_pmd(page
, prot
);
749 entry
= pmd_mkhuge(entry
);
753 static inline struct list_head
*page_deferred_list(struct page
*page
)
756 * ->lru in the tail pages is occupied by compound_head.
757 * Let's use ->mapping + ->index in the second tail page as list_head.
759 return (struct list_head
*)&page
[2].mapping
;
762 void prep_transhuge_page(struct page
*page
)
765 * we use page->mapping and page->indexlru in second tail page
766 * as list_head: assuming THP order >= 2
768 BUILD_BUG_ON(HPAGE_PMD_ORDER
< 2);
770 INIT_LIST_HEAD(page_deferred_list(page
));
771 set_compound_page_dtor(page
, TRANSHUGE_PAGE_DTOR
);
774 static int __do_huge_pmd_anonymous_page(struct mm_struct
*mm
,
775 struct vm_area_struct
*vma
,
776 unsigned long address
, pmd_t
*pmd
,
777 struct page
*page
, gfp_t gfp
,
780 struct mem_cgroup
*memcg
;
783 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
785 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
787 if (mem_cgroup_try_charge(page
, mm
, gfp
, &memcg
, true)) {
789 count_vm_event(THP_FAULT_FALLBACK
);
790 return VM_FAULT_FALLBACK
;
793 pgtable
= pte_alloc_one(mm
, haddr
);
794 if (unlikely(!pgtable
)) {
795 mem_cgroup_cancel_charge(page
, memcg
, true);
800 clear_huge_page(page
, haddr
, HPAGE_PMD_NR
);
802 * The memory barrier inside __SetPageUptodate makes sure that
803 * clear_huge_page writes become visible before the set_pmd_at()
806 __SetPageUptodate(page
);
808 ptl
= pmd_lock(mm
, pmd
);
809 if (unlikely(!pmd_none(*pmd
))) {
811 mem_cgroup_cancel_charge(page
, memcg
, true);
813 pte_free(mm
, pgtable
);
817 /* Deliver the page fault to userland */
818 if (userfaultfd_missing(vma
)) {
822 mem_cgroup_cancel_charge(page
, memcg
, true);
824 pte_free(mm
, pgtable
);
825 ret
= handle_userfault(vma
, address
, flags
,
827 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
831 entry
= mk_huge_pmd(page
, vma
->vm_page_prot
);
832 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
833 page_add_new_anon_rmap(page
, vma
, haddr
, true);
834 mem_cgroup_commit_charge(page
, memcg
, false, true);
835 lru_cache_add_active_or_unevictable(page
, vma
);
836 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
837 set_pmd_at(mm
, haddr
, pmd
, entry
);
838 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
839 atomic_long_inc(&mm
->nr_ptes
);
841 count_vm_event(THP_FAULT_ALLOC
);
847 static inline gfp_t
alloc_hugepage_gfpmask(int defrag
, gfp_t extra_gfp
)
849 return (GFP_TRANSHUGE
& ~(defrag
? 0 : __GFP_RECLAIM
)) | extra_gfp
;
852 /* Caller must hold page table lock. */
853 static bool set_huge_zero_page(pgtable_t pgtable
, struct mm_struct
*mm
,
854 struct vm_area_struct
*vma
, unsigned long haddr
, pmd_t
*pmd
,
855 struct page
*zero_page
)
860 entry
= mk_pmd(zero_page
, vma
->vm_page_prot
);
861 entry
= pmd_mkhuge(entry
);
862 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
863 set_pmd_at(mm
, haddr
, pmd
, entry
);
864 atomic_long_inc(&mm
->nr_ptes
);
868 int do_huge_pmd_anonymous_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
869 unsigned long address
, pmd_t
*pmd
,
874 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
876 if (haddr
< vma
->vm_start
|| haddr
+ HPAGE_PMD_SIZE
> vma
->vm_end
)
877 return VM_FAULT_FALLBACK
;
878 if (unlikely(anon_vma_prepare(vma
)))
880 if (unlikely(khugepaged_enter(vma
, vma
->vm_flags
)))
882 if (!(flags
& FAULT_FLAG_WRITE
) && !mm_forbids_zeropage(mm
) &&
883 transparent_hugepage_use_zero_page()) {
886 struct page
*zero_page
;
889 pgtable
= pte_alloc_one(mm
, haddr
);
890 if (unlikely(!pgtable
))
892 zero_page
= get_huge_zero_page();
893 if (unlikely(!zero_page
)) {
894 pte_free(mm
, pgtable
);
895 count_vm_event(THP_FAULT_FALLBACK
);
896 return VM_FAULT_FALLBACK
;
898 ptl
= pmd_lock(mm
, pmd
);
901 if (pmd_none(*pmd
)) {
902 if (userfaultfd_missing(vma
)) {
904 ret
= handle_userfault(vma
, address
, flags
,
906 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
908 set_huge_zero_page(pgtable
, mm
, vma
,
917 pte_free(mm
, pgtable
);
918 put_huge_zero_page();
922 gfp
= alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma
), 0);
923 page
= alloc_hugepage_vma(gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
924 if (unlikely(!page
)) {
925 count_vm_event(THP_FAULT_FALLBACK
);
926 return VM_FAULT_FALLBACK
;
928 prep_transhuge_page(page
);
929 return __do_huge_pmd_anonymous_page(mm
, vma
, address
, pmd
, page
, gfp
,
933 static void insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
934 pmd_t
*pmd
, unsigned long pfn
, pgprot_t prot
, bool write
)
936 struct mm_struct
*mm
= vma
->vm_mm
;
940 ptl
= pmd_lock(mm
, pmd
);
941 entry
= pmd_mkhuge(pfn_pmd(pfn
, prot
));
943 entry
= pmd_mkyoung(pmd_mkdirty(entry
));
944 entry
= maybe_pmd_mkwrite(entry
, vma
);
946 set_pmd_at(mm
, addr
, pmd
, entry
);
947 update_mmu_cache_pmd(vma
, addr
, pmd
);
951 int vmf_insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
952 pmd_t
*pmd
, unsigned long pfn
, bool write
)
954 pgprot_t pgprot
= vma
->vm_page_prot
;
956 * If we had pmd_special, we could avoid all these restrictions,
957 * but we need to be consistent with PTEs and architectures that
958 * can't support a 'special' bit.
960 BUG_ON(!(vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)));
961 BUG_ON((vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)) ==
962 (VM_PFNMAP
|VM_MIXEDMAP
));
963 BUG_ON((vma
->vm_flags
& VM_PFNMAP
) && is_cow_mapping(vma
->vm_flags
));
964 BUG_ON((vma
->vm_flags
& VM_MIXEDMAP
) && pfn_valid(pfn
));
966 if (addr
< vma
->vm_start
|| addr
>= vma
->vm_end
)
967 return VM_FAULT_SIGBUS
;
968 if (track_pfn_insert(vma
, &pgprot
, pfn
))
969 return VM_FAULT_SIGBUS
;
970 insert_pfn_pmd(vma
, addr
, pmd
, pfn
, pgprot
, write
);
971 return VM_FAULT_NOPAGE
;
974 int copy_huge_pmd(struct mm_struct
*dst_mm
, struct mm_struct
*src_mm
,
975 pmd_t
*dst_pmd
, pmd_t
*src_pmd
, unsigned long addr
,
976 struct vm_area_struct
*vma
)
978 spinlock_t
*dst_ptl
, *src_ptl
;
979 struct page
*src_page
;
985 pgtable
= pte_alloc_one(dst_mm
, addr
);
986 if (unlikely(!pgtable
))
989 dst_ptl
= pmd_lock(dst_mm
, dst_pmd
);
990 src_ptl
= pmd_lockptr(src_mm
, src_pmd
);
991 spin_lock_nested(src_ptl
, SINGLE_DEPTH_NESTING
);
995 if (unlikely(!pmd_trans_huge(pmd
))) {
996 pte_free(dst_mm
, pgtable
);
1000 * When page table lock is held, the huge zero pmd should not be
1001 * under splitting since we don't split the page itself, only pmd to
1004 if (is_huge_zero_pmd(pmd
)) {
1005 struct page
*zero_page
;
1007 * get_huge_zero_page() will never allocate a new page here,
1008 * since we already have a zero page to copy. It just takes a
1011 zero_page
= get_huge_zero_page();
1012 set_huge_zero_page(pgtable
, dst_mm
, vma
, addr
, dst_pmd
,
1018 src_page
= pmd_page(pmd
);
1019 VM_BUG_ON_PAGE(!PageHead(src_page
), src_page
);
1021 page_dup_rmap(src_page
, true);
1022 add_mm_counter(dst_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1024 pmdp_set_wrprotect(src_mm
, addr
, src_pmd
);
1025 pmd
= pmd_mkold(pmd_wrprotect(pmd
));
1026 pgtable_trans_huge_deposit(dst_mm
, dst_pmd
, pgtable
);
1027 set_pmd_at(dst_mm
, addr
, dst_pmd
, pmd
);
1028 atomic_long_inc(&dst_mm
->nr_ptes
);
1032 spin_unlock(src_ptl
);
1033 spin_unlock(dst_ptl
);
1038 void huge_pmd_set_accessed(struct mm_struct
*mm
,
1039 struct vm_area_struct
*vma
,
1040 unsigned long address
,
1041 pmd_t
*pmd
, pmd_t orig_pmd
,
1046 unsigned long haddr
;
1048 ptl
= pmd_lock(mm
, pmd
);
1049 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1052 entry
= pmd_mkyoung(orig_pmd
);
1053 haddr
= address
& HPAGE_PMD_MASK
;
1054 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, dirty
))
1055 update_mmu_cache_pmd(vma
, address
, pmd
);
1061 static int do_huge_pmd_wp_page_fallback(struct mm_struct
*mm
,
1062 struct vm_area_struct
*vma
,
1063 unsigned long address
,
1064 pmd_t
*pmd
, pmd_t orig_pmd
,
1066 unsigned long haddr
)
1068 struct mem_cgroup
*memcg
;
1073 struct page
**pages
;
1074 unsigned long mmun_start
; /* For mmu_notifiers */
1075 unsigned long mmun_end
; /* For mmu_notifiers */
1077 pages
= kmalloc(sizeof(struct page
*) * HPAGE_PMD_NR
,
1079 if (unlikely(!pages
)) {
1080 ret
|= VM_FAULT_OOM
;
1084 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1085 pages
[i
] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE
|
1087 vma
, address
, page_to_nid(page
));
1088 if (unlikely(!pages
[i
] ||
1089 mem_cgroup_try_charge(pages
[i
], mm
, GFP_KERNEL
,
1094 memcg
= (void *)page_private(pages
[i
]);
1095 set_page_private(pages
[i
], 0);
1096 mem_cgroup_cancel_charge(pages
[i
], memcg
,
1101 ret
|= VM_FAULT_OOM
;
1104 set_page_private(pages
[i
], (unsigned long)memcg
);
1107 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1108 copy_user_highpage(pages
[i
], page
+ i
,
1109 haddr
+ PAGE_SIZE
* i
, vma
);
1110 __SetPageUptodate(pages
[i
]);
1115 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1116 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1118 ptl
= pmd_lock(mm
, pmd
);
1119 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1120 goto out_free_pages
;
1121 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1123 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1124 /* leave pmd empty until pte is filled */
1126 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
1127 pmd_populate(mm
, &_pmd
, pgtable
);
1129 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
1131 entry
= mk_pte(pages
[i
], vma
->vm_page_prot
);
1132 entry
= maybe_mkwrite(pte_mkdirty(entry
), vma
);
1133 memcg
= (void *)page_private(pages
[i
]);
1134 set_page_private(pages
[i
], 0);
1135 page_add_new_anon_rmap(pages
[i
], vma
, haddr
, false);
1136 mem_cgroup_commit_charge(pages
[i
], memcg
, false, false);
1137 lru_cache_add_active_or_unevictable(pages
[i
], vma
);
1138 pte
= pte_offset_map(&_pmd
, haddr
);
1139 VM_BUG_ON(!pte_none(*pte
));
1140 set_pte_at(mm
, haddr
, pte
, entry
);
1145 smp_wmb(); /* make pte visible before pmd */
1146 pmd_populate(mm
, pmd
, pgtable
);
1147 page_remove_rmap(page
, true);
1150 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1152 ret
|= VM_FAULT_WRITE
;
1160 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1161 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1162 memcg
= (void *)page_private(pages
[i
]);
1163 set_page_private(pages
[i
], 0);
1164 mem_cgroup_cancel_charge(pages
[i
], memcg
, false);
1171 int do_huge_pmd_wp_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1172 unsigned long address
, pmd_t
*pmd
, pmd_t orig_pmd
)
1176 struct page
*page
= NULL
, *new_page
;
1177 struct mem_cgroup
*memcg
;
1178 unsigned long haddr
;
1179 unsigned long mmun_start
; /* For mmu_notifiers */
1180 unsigned long mmun_end
; /* For mmu_notifiers */
1181 gfp_t huge_gfp
; /* for allocation and charge */
1183 ptl
= pmd_lockptr(mm
, pmd
);
1184 VM_BUG_ON_VMA(!vma
->anon_vma
, vma
);
1185 haddr
= address
& HPAGE_PMD_MASK
;
1186 if (is_huge_zero_pmd(orig_pmd
))
1189 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1192 page
= pmd_page(orig_pmd
);
1193 VM_BUG_ON_PAGE(!PageCompound(page
) || !PageHead(page
), page
);
1195 * We can only reuse the page if nobody else maps the huge page or it's
1196 * part. We can do it by checking page_mapcount() on each sub-page, but
1198 * The cheaper way is to check page_count() to be equal 1: every
1199 * mapcount takes page reference reference, so this way we can
1200 * guarantee, that the PMD is the only mapping.
1201 * This can give false negative if somebody pinned the page, but that's
1204 if (page_mapcount(page
) == 1 && page_count(page
) == 1) {
1206 entry
= pmd_mkyoung(orig_pmd
);
1207 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1208 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, 1))
1209 update_mmu_cache_pmd(vma
, address
, pmd
);
1210 ret
|= VM_FAULT_WRITE
;
1216 if (transparent_hugepage_enabled(vma
) &&
1217 !transparent_hugepage_debug_cow()) {
1218 huge_gfp
= alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma
), 0);
1219 new_page
= alloc_hugepage_vma(huge_gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
1223 if (likely(new_page
)) {
1224 prep_transhuge_page(new_page
);
1227 split_huge_pmd(vma
, pmd
, address
);
1228 ret
|= VM_FAULT_FALLBACK
;
1230 ret
= do_huge_pmd_wp_page_fallback(mm
, vma
, address
,
1231 pmd
, orig_pmd
, page
, haddr
);
1232 if (ret
& VM_FAULT_OOM
) {
1233 split_huge_pmd(vma
, pmd
, address
);
1234 ret
|= VM_FAULT_FALLBACK
;
1238 count_vm_event(THP_FAULT_FALLBACK
);
1242 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, huge_gfp
, &memcg
,
1246 split_huge_pmd(vma
, pmd
, address
);
1249 split_huge_pmd(vma
, pmd
, address
);
1250 ret
|= VM_FAULT_FALLBACK
;
1251 count_vm_event(THP_FAULT_FALLBACK
);
1255 count_vm_event(THP_FAULT_ALLOC
);
1258 clear_huge_page(new_page
, haddr
, HPAGE_PMD_NR
);
1260 copy_user_huge_page(new_page
, page
, haddr
, vma
, HPAGE_PMD_NR
);
1261 __SetPageUptodate(new_page
);
1264 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1265 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1270 if (unlikely(!pmd_same(*pmd
, orig_pmd
))) {
1272 mem_cgroup_cancel_charge(new_page
, memcg
, true);
1277 entry
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1278 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1279 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1280 page_add_new_anon_rmap(new_page
, vma
, haddr
, true);
1281 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
1282 lru_cache_add_active_or_unevictable(new_page
, vma
);
1283 set_pmd_at(mm
, haddr
, pmd
, entry
);
1284 update_mmu_cache_pmd(vma
, address
, pmd
);
1286 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1287 put_huge_zero_page();
1289 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1290 page_remove_rmap(page
, true);
1293 ret
|= VM_FAULT_WRITE
;
1297 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1305 struct page
*follow_trans_huge_pmd(struct vm_area_struct
*vma
,
1310 struct mm_struct
*mm
= vma
->vm_mm
;
1311 struct page
*page
= NULL
;
1313 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1315 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1318 /* Avoid dumping huge zero page */
1319 if ((flags
& FOLL_DUMP
) && is_huge_zero_pmd(*pmd
))
1320 return ERR_PTR(-EFAULT
);
1322 /* Full NUMA hinting faults to serialise migration in fault paths */
1323 if ((flags
& FOLL_NUMA
) && pmd_protnone(*pmd
))
1326 page
= pmd_page(*pmd
);
1327 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1328 if (flags
& FOLL_TOUCH
) {
1331 * We should set the dirty bit only for FOLL_WRITE but
1332 * for now the dirty bit in the pmd is meaningless.
1333 * And if the dirty bit will become meaningful and
1334 * we'll only set it with FOLL_WRITE, an atomic
1335 * set_bit will be required on the pmd to set the
1336 * young bit, instead of the current set_pmd_at.
1338 _pmd
= pmd_mkyoung(pmd_mkdirty(*pmd
));
1339 if (pmdp_set_access_flags(vma
, addr
& HPAGE_PMD_MASK
,
1341 update_mmu_cache_pmd(vma
, addr
, pmd
);
1343 if ((flags
& FOLL_MLOCK
) && (vma
->vm_flags
& VM_LOCKED
)) {
1345 * We don't mlock() pte-mapped THPs. This way we can avoid
1346 * leaking mlocked pages into non-VM_LOCKED VMAs.
1348 * In most cases the pmd is the only mapping of the page as we
1349 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1350 * writable private mappings in populate_vma_page_range().
1352 * The only scenario when we have the page shared here is if we
1353 * mlocking read-only mapping shared over fork(). We skip
1354 * mlocking such pages.
1356 if (compound_mapcount(page
) == 1 && !PageDoubleMap(page
) &&
1357 page
->mapping
&& trylock_page(page
)) {
1360 mlock_vma_page(page
);
1364 page
+= (addr
& ~HPAGE_PMD_MASK
) >> PAGE_SHIFT
;
1365 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
1366 if (flags
& FOLL_GET
)
1373 /* NUMA hinting page fault entry point for trans huge pmds */
1374 int do_huge_pmd_numa_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1375 unsigned long addr
, pmd_t pmd
, pmd_t
*pmdp
)
1378 struct anon_vma
*anon_vma
= NULL
;
1380 unsigned long haddr
= addr
& HPAGE_PMD_MASK
;
1381 int page_nid
= -1, this_nid
= numa_node_id();
1382 int target_nid
, last_cpupid
= -1;
1384 bool migrated
= false;
1388 /* A PROT_NONE fault should not end up here */
1389 BUG_ON(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)));
1391 ptl
= pmd_lock(mm
, pmdp
);
1392 if (unlikely(!pmd_same(pmd
, *pmdp
)))
1396 * If there are potential migrations, wait for completion and retry
1397 * without disrupting NUMA hinting information. Do not relock and
1398 * check_same as the page may no longer be mapped.
1400 if (unlikely(pmd_trans_migrating(*pmdp
))) {
1401 page
= pmd_page(*pmdp
);
1403 wait_on_page_locked(page
);
1407 page
= pmd_page(pmd
);
1408 BUG_ON(is_huge_zero_page(page
));
1409 page_nid
= page_to_nid(page
);
1410 last_cpupid
= page_cpupid_last(page
);
1411 count_vm_numa_event(NUMA_HINT_FAULTS
);
1412 if (page_nid
== this_nid
) {
1413 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL
);
1414 flags
|= TNF_FAULT_LOCAL
;
1417 /* See similar comment in do_numa_page for explanation */
1418 if (!(vma
->vm_flags
& VM_WRITE
))
1419 flags
|= TNF_NO_GROUP
;
1422 * Acquire the page lock to serialise THP migrations but avoid dropping
1423 * page_table_lock if at all possible
1425 page_locked
= trylock_page(page
);
1426 target_nid
= mpol_misplaced(page
, vma
, haddr
);
1427 if (target_nid
== -1) {
1428 /* If the page was locked, there are no parallel migrations */
1433 /* Migration could have started since the pmd_trans_migrating check */
1436 wait_on_page_locked(page
);
1442 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1443 * to serialises splits
1447 anon_vma
= page_lock_anon_vma_read(page
);
1449 /* Confirm the PMD did not change while page_table_lock was released */
1451 if (unlikely(!pmd_same(pmd
, *pmdp
))) {
1458 /* Bail if we fail to protect against THP splits for any reason */
1459 if (unlikely(!anon_vma
)) {
1466 * Migrate the THP to the requested node, returns with page unlocked
1467 * and access rights restored.
1470 migrated
= migrate_misplaced_transhuge_page(mm
, vma
,
1471 pmdp
, pmd
, addr
, page
, target_nid
);
1473 flags
|= TNF_MIGRATED
;
1474 page_nid
= target_nid
;
1476 flags
|= TNF_MIGRATE_FAIL
;
1480 BUG_ON(!PageLocked(page
));
1481 was_writable
= pmd_write(pmd
);
1482 pmd
= pmd_modify(pmd
, vma
->vm_page_prot
);
1483 pmd
= pmd_mkyoung(pmd
);
1485 pmd
= pmd_mkwrite(pmd
);
1486 set_pmd_at(mm
, haddr
, pmdp
, pmd
);
1487 update_mmu_cache_pmd(vma
, addr
, pmdp
);
1494 page_unlock_anon_vma_read(anon_vma
);
1497 task_numa_fault(last_cpupid
, page_nid
, HPAGE_PMD_NR
, flags
);
1502 int madvise_free_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1503 pmd_t
*pmd
, unsigned long addr
, unsigned long next
)
1509 struct mm_struct
*mm
= tlb
->mm
;
1512 if (!pmd_trans_huge_lock(pmd
, vma
, &ptl
))
1516 if (is_huge_zero_pmd(orig_pmd
)) {
1521 page
= pmd_page(orig_pmd
);
1523 * If other processes are mapping this page, we couldn't discard
1524 * the page unless they all do MADV_FREE so let's skip the page.
1526 if (page_mapcount(page
) != 1)
1529 if (!trylock_page(page
))
1533 * If user want to discard part-pages of THP, split it so MADV_FREE
1534 * will deactivate only them.
1536 if (next
- addr
!= HPAGE_PMD_SIZE
) {
1539 if (split_huge_page(page
)) {
1550 if (PageDirty(page
))
1551 ClearPageDirty(page
);
1554 if (PageActive(page
))
1555 deactivate_page(page
);
1557 if (pmd_young(orig_pmd
) || pmd_dirty(orig_pmd
)) {
1558 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1560 orig_pmd
= pmd_mkold(orig_pmd
);
1561 orig_pmd
= pmd_mkclean(orig_pmd
);
1563 set_pmd_at(mm
, addr
, pmd
, orig_pmd
);
1564 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1573 int zap_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1574 pmd_t
*pmd
, unsigned long addr
)
1579 if (!__pmd_trans_huge_lock(pmd
, vma
, &ptl
))
1582 * For architectures like ppc64 we look at deposited pgtable
1583 * when calling pmdp_huge_get_and_clear. So do the
1584 * pgtable_trans_huge_withdraw after finishing pmdp related
1587 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1589 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1590 if (vma_is_dax(vma
)) {
1592 if (is_huge_zero_pmd(orig_pmd
))
1593 put_huge_zero_page();
1594 } else if (is_huge_zero_pmd(orig_pmd
)) {
1595 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1596 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1598 put_huge_zero_page();
1600 struct page
*page
= pmd_page(orig_pmd
);
1601 page_remove_rmap(page
, true);
1602 VM_BUG_ON_PAGE(page_mapcount(page
) < 0, page
);
1603 add_mm_counter(tlb
->mm
, MM_ANONPAGES
, -HPAGE_PMD_NR
);
1604 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1605 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1606 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1608 tlb_remove_page(tlb
, page
);
1613 bool move_huge_pmd(struct vm_area_struct
*vma
, struct vm_area_struct
*new_vma
,
1614 unsigned long old_addr
,
1615 unsigned long new_addr
, unsigned long old_end
,
1616 pmd_t
*old_pmd
, pmd_t
*new_pmd
)
1618 spinlock_t
*old_ptl
, *new_ptl
;
1621 struct mm_struct
*mm
= vma
->vm_mm
;
1623 if ((old_addr
& ~HPAGE_PMD_MASK
) ||
1624 (new_addr
& ~HPAGE_PMD_MASK
) ||
1625 old_end
- old_addr
< HPAGE_PMD_SIZE
||
1626 (new_vma
->vm_flags
& VM_NOHUGEPAGE
))
1630 * The destination pmd shouldn't be established, free_pgtables()
1631 * should have release it.
1633 if (WARN_ON(!pmd_none(*new_pmd
))) {
1634 VM_BUG_ON(pmd_trans_huge(*new_pmd
));
1639 * We don't have to worry about the ordering of src and dst
1640 * ptlocks because exclusive mmap_sem prevents deadlock.
1642 if (__pmd_trans_huge_lock(old_pmd
, vma
, &old_ptl
)) {
1643 new_ptl
= pmd_lockptr(mm
, new_pmd
);
1644 if (new_ptl
!= old_ptl
)
1645 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
1646 pmd
= pmdp_huge_get_and_clear(mm
, old_addr
, old_pmd
);
1647 VM_BUG_ON(!pmd_none(*new_pmd
));
1649 if (pmd_move_must_withdraw(new_ptl
, old_ptl
)) {
1651 pgtable
= pgtable_trans_huge_withdraw(mm
, old_pmd
);
1652 pgtable_trans_huge_deposit(mm
, new_pmd
, pgtable
);
1654 set_pmd_at(mm
, new_addr
, new_pmd
, pmd_mksoft_dirty(pmd
));
1655 if (new_ptl
!= old_ptl
)
1656 spin_unlock(new_ptl
);
1657 spin_unlock(old_ptl
);
1665 * - 0 if PMD could not be locked
1666 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1667 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1669 int change_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1670 unsigned long addr
, pgprot_t newprot
, int prot_numa
)
1672 struct mm_struct
*mm
= vma
->vm_mm
;
1676 if (__pmd_trans_huge_lock(pmd
, vma
, &ptl
)) {
1678 bool preserve_write
= prot_numa
&& pmd_write(*pmd
);
1682 * Avoid trapping faults against the zero page. The read-only
1683 * data is likely to be read-cached on the local CPU and
1684 * local/remote hits to the zero page are not interesting.
1686 if (prot_numa
&& is_huge_zero_pmd(*pmd
)) {
1691 if (!prot_numa
|| !pmd_protnone(*pmd
)) {
1692 entry
= pmdp_huge_get_and_clear_notify(mm
, addr
, pmd
);
1693 entry
= pmd_modify(entry
, newprot
);
1695 entry
= pmd_mkwrite(entry
);
1697 set_pmd_at(mm
, addr
, pmd
, entry
);
1698 BUG_ON(!preserve_write
&& pmd_write(entry
));
1707 * Returns true if a given pmd maps a thp, false otherwise.
1709 * Note that if it returns true, this routine returns without unlocking page
1710 * table lock. So callers must unlock it.
1712 bool __pmd_trans_huge_lock(pmd_t
*pmd
, struct vm_area_struct
*vma
,
1715 *ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1716 if (likely(pmd_trans_huge(*pmd
)))
1722 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1724 int hugepage_madvise(struct vm_area_struct
*vma
,
1725 unsigned long *vm_flags
, int advice
)
1731 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1732 * can't handle this properly after s390_enable_sie, so we simply
1733 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1735 if (mm_has_pgste(vma
->vm_mm
))
1739 * Be somewhat over-protective like KSM for now!
1741 if (*vm_flags
& VM_NO_THP
)
1743 *vm_flags
&= ~VM_NOHUGEPAGE
;
1744 *vm_flags
|= VM_HUGEPAGE
;
1746 * If the vma become good for khugepaged to scan,
1747 * register it here without waiting a page fault that
1748 * may not happen any time soon.
1750 if (unlikely(khugepaged_enter_vma_merge(vma
, *vm_flags
)))
1753 case MADV_NOHUGEPAGE
:
1755 * Be somewhat over-protective like KSM for now!
1757 if (*vm_flags
& VM_NO_THP
)
1759 *vm_flags
&= ~VM_HUGEPAGE
;
1760 *vm_flags
|= VM_NOHUGEPAGE
;
1762 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1763 * this vma even if we leave the mm registered in khugepaged if
1764 * it got registered before VM_NOHUGEPAGE was set.
1772 static int __init
khugepaged_slab_init(void)
1774 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
1775 sizeof(struct mm_slot
),
1776 __alignof__(struct mm_slot
), 0, NULL
);
1783 static void __init
khugepaged_slab_exit(void)
1785 kmem_cache_destroy(mm_slot_cache
);
1788 static inline struct mm_slot
*alloc_mm_slot(void)
1790 if (!mm_slot_cache
) /* initialization failed */
1792 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
1795 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
1797 kmem_cache_free(mm_slot_cache
, mm_slot
);
1800 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
1802 struct mm_slot
*mm_slot
;
1804 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
1805 if (mm
== mm_slot
->mm
)
1811 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
1812 struct mm_slot
*mm_slot
)
1815 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
1818 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
1820 return atomic_read(&mm
->mm_users
) == 0;
1823 int __khugepaged_enter(struct mm_struct
*mm
)
1825 struct mm_slot
*mm_slot
;
1828 mm_slot
= alloc_mm_slot();
1832 /* __khugepaged_exit() must not run from under us */
1833 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
1834 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
1835 free_mm_slot(mm_slot
);
1839 spin_lock(&khugepaged_mm_lock
);
1840 insert_to_mm_slots_hash(mm
, mm_slot
);
1842 * Insert just behind the scanning cursor, to let the area settle
1845 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
1846 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
1847 spin_unlock(&khugepaged_mm_lock
);
1849 atomic_inc(&mm
->mm_count
);
1851 wake_up_interruptible(&khugepaged_wait
);
1856 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
1857 unsigned long vm_flags
)
1859 unsigned long hstart
, hend
;
1862 * Not yet faulted in so we will register later in the
1863 * page fault if needed.
1867 /* khugepaged not yet working on file or special mappings */
1869 VM_BUG_ON_VMA(vm_flags
& VM_NO_THP
, vma
);
1870 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1871 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1873 return khugepaged_enter(vma
, vm_flags
);
1877 void __khugepaged_exit(struct mm_struct
*mm
)
1879 struct mm_slot
*mm_slot
;
1882 spin_lock(&khugepaged_mm_lock
);
1883 mm_slot
= get_mm_slot(mm
);
1884 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
1885 hash_del(&mm_slot
->hash
);
1886 list_del(&mm_slot
->mm_node
);
1889 spin_unlock(&khugepaged_mm_lock
);
1892 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
1893 free_mm_slot(mm_slot
);
1895 } else if (mm_slot
) {
1897 * This is required to serialize against
1898 * khugepaged_test_exit() (which is guaranteed to run
1899 * under mmap sem read mode). Stop here (after we
1900 * return all pagetables will be destroyed) until
1901 * khugepaged has finished working on the pagetables
1902 * under the mmap_sem.
1904 down_write(&mm
->mmap_sem
);
1905 up_write(&mm
->mmap_sem
);
1909 static void release_pte_page(struct page
*page
)
1911 /* 0 stands for page_is_file_cache(page) == false */
1912 dec_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
1914 putback_lru_page(page
);
1917 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
)
1919 while (--_pte
>= pte
) {
1920 pte_t pteval
= *_pte
;
1921 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)))
1922 release_pte_page(pte_page(pteval
));
1926 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
1927 unsigned long address
,
1930 struct page
*page
= NULL
;
1932 int none_or_zero
= 0, result
= 0;
1933 bool referenced
= false, writable
= false;
1935 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
1936 _pte
++, address
+= PAGE_SIZE
) {
1937 pte_t pteval
= *_pte
;
1938 if (pte_none(pteval
) || (pte_present(pteval
) &&
1939 is_zero_pfn(pte_pfn(pteval
)))) {
1940 if (!userfaultfd_armed(vma
) &&
1941 ++none_or_zero
<= khugepaged_max_ptes_none
) {
1944 result
= SCAN_EXCEED_NONE_PTE
;
1948 if (!pte_present(pteval
)) {
1949 result
= SCAN_PTE_NON_PRESENT
;
1952 page
= vm_normal_page(vma
, address
, pteval
);
1953 if (unlikely(!page
)) {
1954 result
= SCAN_PAGE_NULL
;
1958 VM_BUG_ON_PAGE(PageCompound(page
), page
);
1959 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
1960 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
1963 * We can do it before isolate_lru_page because the
1964 * page can't be freed from under us. NOTE: PG_lock
1965 * is needed to serialize against split_huge_page
1966 * when invoked from the VM.
1968 if (!trylock_page(page
)) {
1969 result
= SCAN_PAGE_LOCK
;
1974 * cannot use mapcount: can't collapse if there's a gup pin.
1975 * The page must only be referenced by the scanned process
1976 * and page swap cache.
1978 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
1980 result
= SCAN_PAGE_COUNT
;
1983 if (pte_write(pteval
)) {
1986 if (PageSwapCache(page
) && !reuse_swap_page(page
)) {
1988 result
= SCAN_SWAP_CACHE_PAGE
;
1992 * Page is not in the swap cache. It can be collapsed
1998 * Isolate the page to avoid collapsing an hugepage
1999 * currently in use by the VM.
2001 if (isolate_lru_page(page
)) {
2003 result
= SCAN_DEL_PAGE_LRU
;
2006 /* 0 stands for page_is_file_cache(page) == false */
2007 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
2008 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
2009 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2011 /* If there is no mapped pte young don't collapse the page */
2012 if (pte_young(pteval
) ||
2013 page_is_young(page
) || PageReferenced(page
) ||
2014 mmu_notifier_test_young(vma
->vm_mm
, address
))
2017 if (likely(writable
)) {
2018 if (likely(referenced
)) {
2019 result
= SCAN_SUCCEED
;
2020 trace_mm_collapse_huge_page_isolate(page_to_pfn(page
), none_or_zero
,
2021 referenced
, writable
, result
);
2025 result
= SCAN_PAGE_RO
;
2029 release_pte_pages(pte
, _pte
);
2030 trace_mm_collapse_huge_page_isolate(page_to_pfn(page
), none_or_zero
,
2031 referenced
, writable
, result
);
2035 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
2036 struct vm_area_struct
*vma
,
2037 unsigned long address
,
2041 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
; _pte
++) {
2042 pte_t pteval
= *_pte
;
2043 struct page
*src_page
;
2045 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2046 clear_user_highpage(page
, address
);
2047 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
2048 if (is_zero_pfn(pte_pfn(pteval
))) {
2050 * ptl mostly unnecessary.
2054 * paravirt calls inside pte_clear here are
2057 pte_clear(vma
->vm_mm
, address
, _pte
);
2061 src_page
= pte_page(pteval
);
2062 copy_user_highpage(page
, src_page
, address
, vma
);
2063 VM_BUG_ON_PAGE(page_mapcount(src_page
) != 1, src_page
);
2064 release_pte_page(src_page
);
2066 * ptl mostly unnecessary, but preempt has to
2067 * be disabled to update the per-cpu stats
2068 * inside page_remove_rmap().
2072 * paravirt calls inside pte_clear here are
2075 pte_clear(vma
->vm_mm
, address
, _pte
);
2076 page_remove_rmap(src_page
, false);
2078 free_page_and_swap_cache(src_page
);
2081 address
+= PAGE_SIZE
;
2086 static void khugepaged_alloc_sleep(void)
2090 add_wait_queue(&khugepaged_wait
, &wait
);
2091 freezable_schedule_timeout_interruptible(
2092 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
2093 remove_wait_queue(&khugepaged_wait
, &wait
);
2096 static int khugepaged_node_load
[MAX_NUMNODES
];
2098 static bool khugepaged_scan_abort(int nid
)
2103 * If zone_reclaim_mode is disabled, then no extra effort is made to
2104 * allocate memory locally.
2106 if (!zone_reclaim_mode
)
2109 /* If there is a count for this node already, it must be acceptable */
2110 if (khugepaged_node_load
[nid
])
2113 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
2114 if (!khugepaged_node_load
[i
])
2116 if (node_distance(nid
, i
) > RECLAIM_DISTANCE
)
2123 static int khugepaged_find_target_node(void)
2125 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
2126 int nid
, target_node
= 0, max_value
= 0;
2128 /* find first node with max normal pages hit */
2129 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
2130 if (khugepaged_node_load
[nid
] > max_value
) {
2131 max_value
= khugepaged_node_load
[nid
];
2135 /* do some balance if several nodes have the same hit record */
2136 if (target_node
<= last_khugepaged_target_node
)
2137 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
2139 if (max_value
== khugepaged_node_load
[nid
]) {
2144 last_khugepaged_target_node
= target_node
;
2148 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2150 if (IS_ERR(*hpage
)) {
2156 khugepaged_alloc_sleep();
2157 } else if (*hpage
) {
2165 static struct page
*
2166 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2167 unsigned long address
, int node
)
2169 VM_BUG_ON_PAGE(*hpage
, *hpage
);
2172 * Before allocating the hugepage, release the mmap_sem read lock.
2173 * The allocation can take potentially a long time if it involves
2174 * sync compaction, and we do not need to hold the mmap_sem during
2175 * that. We will recheck the vma after taking it again in write mode.
2177 up_read(&mm
->mmap_sem
);
2179 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
2180 if (unlikely(!*hpage
)) {
2181 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2182 *hpage
= ERR_PTR(-ENOMEM
);
2186 prep_transhuge_page(*hpage
);
2187 count_vm_event(THP_COLLAPSE_ALLOC
);
2191 static int khugepaged_find_target_node(void)
2196 static inline struct page
*alloc_hugepage(int defrag
)
2200 page
= alloc_pages(alloc_hugepage_gfpmask(defrag
, 0), HPAGE_PMD_ORDER
);
2202 prep_transhuge_page(page
);
2206 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
2211 hpage
= alloc_hugepage(khugepaged_defrag());
2213 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2218 khugepaged_alloc_sleep();
2220 count_vm_event(THP_COLLAPSE_ALLOC
);
2221 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
2226 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2229 *hpage
= khugepaged_alloc_hugepage(wait
);
2231 if (unlikely(!*hpage
))
2237 static struct page
*
2238 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2239 unsigned long address
, int node
)
2241 up_read(&mm
->mmap_sem
);
2248 static bool hugepage_vma_check(struct vm_area_struct
*vma
)
2250 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
2251 (vma
->vm_flags
& VM_NOHUGEPAGE
))
2253 if (!vma
->anon_vma
|| vma
->vm_ops
)
2255 if (is_vma_temporary_stack(vma
))
2257 VM_BUG_ON_VMA(vma
->vm_flags
& VM_NO_THP
, vma
);
2261 static void collapse_huge_page(struct mm_struct
*mm
,
2262 unsigned long address
,
2263 struct page
**hpage
,
2264 struct vm_area_struct
*vma
,
2270 struct page
*new_page
;
2271 spinlock_t
*pmd_ptl
, *pte_ptl
;
2272 int isolated
, result
= 0;
2273 unsigned long hstart
, hend
;
2274 struct mem_cgroup
*memcg
;
2275 unsigned long mmun_start
; /* For mmu_notifiers */
2276 unsigned long mmun_end
; /* For mmu_notifiers */
2279 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2281 /* Only allocate from the target node */
2282 gfp
= alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE
) |
2285 /* release the mmap_sem read lock. */
2286 new_page
= khugepaged_alloc_page(hpage
, gfp
, mm
, address
, node
);
2288 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
2292 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, gfp
, &memcg
, true))) {
2293 result
= SCAN_CGROUP_CHARGE_FAIL
;
2298 * Prevent all access to pagetables with the exception of
2299 * gup_fast later hanlded by the ptep_clear_flush and the VM
2300 * handled by the anon_vma lock + PG_lock.
2302 down_write(&mm
->mmap_sem
);
2303 if (unlikely(khugepaged_test_exit(mm
))) {
2304 result
= SCAN_ANY_PROCESS
;
2308 vma
= find_vma(mm
, address
);
2310 result
= SCAN_VMA_NULL
;
2313 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2314 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2315 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
) {
2316 result
= SCAN_ADDRESS_RANGE
;
2319 if (!hugepage_vma_check(vma
)) {
2320 result
= SCAN_VMA_CHECK
;
2323 pmd
= mm_find_pmd(mm
, address
);
2325 result
= SCAN_PMD_NULL
;
2329 anon_vma_lock_write(vma
->anon_vma
);
2331 pte
= pte_offset_map(pmd
, address
);
2332 pte_ptl
= pte_lockptr(mm
, pmd
);
2334 mmun_start
= address
;
2335 mmun_end
= address
+ HPAGE_PMD_SIZE
;
2336 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
2337 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
2339 * After this gup_fast can't run anymore. This also removes
2340 * any huge TLB entry from the CPU so we won't allow
2341 * huge and small TLB entries for the same virtual address
2342 * to avoid the risk of CPU bugs in that area.
2344 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
2345 spin_unlock(pmd_ptl
);
2346 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
2349 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
);
2350 spin_unlock(pte_ptl
);
2352 if (unlikely(!isolated
)) {
2355 BUG_ON(!pmd_none(*pmd
));
2357 * We can only use set_pmd_at when establishing
2358 * hugepmds and never for establishing regular pmds that
2359 * points to regular pagetables. Use pmd_populate for that
2361 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
2362 spin_unlock(pmd_ptl
);
2363 anon_vma_unlock_write(vma
->anon_vma
);
2369 * All pages are isolated and locked so anon_vma rmap
2370 * can't run anymore.
2372 anon_vma_unlock_write(vma
->anon_vma
);
2374 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
);
2376 __SetPageUptodate(new_page
);
2377 pgtable
= pmd_pgtable(_pmd
);
2379 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
2380 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
2383 * spin_lock() below is not the equivalent of smp_wmb(), so
2384 * this is needed to avoid the copy_huge_page writes to become
2385 * visible after the set_pmd_at() write.
2390 BUG_ON(!pmd_none(*pmd
));
2391 page_add_new_anon_rmap(new_page
, vma
, address
, true);
2392 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
2393 lru_cache_add_active_or_unevictable(new_page
, vma
);
2394 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
2395 set_pmd_at(mm
, address
, pmd
, _pmd
);
2396 update_mmu_cache_pmd(vma
, address
, pmd
);
2397 spin_unlock(pmd_ptl
);
2401 khugepaged_pages_collapsed
++;
2402 result
= SCAN_SUCCEED
;
2404 up_write(&mm
->mmap_sem
);
2405 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2409 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2412 mem_cgroup_cancel_charge(new_page
, memcg
, true);
2416 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
2417 struct vm_area_struct
*vma
,
2418 unsigned long address
,
2419 struct page
**hpage
)
2423 int ret
= 0, none_or_zero
= 0, result
= 0;
2424 struct page
*page
= NULL
;
2425 unsigned long _address
;
2427 int node
= NUMA_NO_NODE
;
2428 bool writable
= false, referenced
= false;
2430 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2432 pmd
= mm_find_pmd(mm
, address
);
2434 result
= SCAN_PMD_NULL
;
2438 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
2439 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
2440 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2441 _pte
++, _address
+= PAGE_SIZE
) {
2442 pte_t pteval
= *_pte
;
2443 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2444 if (!userfaultfd_armed(vma
) &&
2445 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2448 result
= SCAN_EXCEED_NONE_PTE
;
2452 if (!pte_present(pteval
)) {
2453 result
= SCAN_PTE_NON_PRESENT
;
2456 if (pte_write(pteval
))
2459 page
= vm_normal_page(vma
, _address
, pteval
);
2460 if (unlikely(!page
)) {
2461 result
= SCAN_PAGE_NULL
;
2465 /* TODO: teach khugepaged to collapse THP mapped with pte */
2466 if (PageCompound(page
)) {
2467 result
= SCAN_PAGE_COMPOUND
;
2472 * Record which node the original page is from and save this
2473 * information to khugepaged_node_load[].
2474 * Khupaged will allocate hugepage from the node has the max
2477 node
= page_to_nid(page
);
2478 if (khugepaged_scan_abort(node
)) {
2479 result
= SCAN_SCAN_ABORT
;
2482 khugepaged_node_load
[node
]++;
2483 if (!PageLRU(page
)) {
2484 result
= SCAN_SCAN_ABORT
;
2487 if (PageLocked(page
)) {
2488 result
= SCAN_PAGE_LOCK
;
2491 if (!PageAnon(page
)) {
2492 result
= SCAN_PAGE_ANON
;
2497 * cannot use mapcount: can't collapse if there's a gup pin.
2498 * The page must only be referenced by the scanned process
2499 * and page swap cache.
2501 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2502 result
= SCAN_PAGE_COUNT
;
2505 if (pte_young(pteval
) ||
2506 page_is_young(page
) || PageReferenced(page
) ||
2507 mmu_notifier_test_young(vma
->vm_mm
, address
))
2512 result
= SCAN_SUCCEED
;
2515 result
= SCAN_NO_REFERENCED_PAGE
;
2518 result
= SCAN_PAGE_RO
;
2521 pte_unmap_unlock(pte
, ptl
);
2523 node
= khugepaged_find_target_node();
2524 /* collapse_huge_page will return with the mmap_sem released */
2525 collapse_huge_page(mm
, address
, hpage
, vma
, node
);
2528 trace_mm_khugepaged_scan_pmd(mm
, page_to_pfn(page
), writable
, referenced
,
2529 none_or_zero
, result
);
2533 static void collect_mm_slot(struct mm_slot
*mm_slot
)
2535 struct mm_struct
*mm
= mm_slot
->mm
;
2537 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2539 if (khugepaged_test_exit(mm
)) {
2541 hash_del(&mm_slot
->hash
);
2542 list_del(&mm_slot
->mm_node
);
2545 * Not strictly needed because the mm exited already.
2547 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2550 /* khugepaged_mm_lock actually not necessary for the below */
2551 free_mm_slot(mm_slot
);
2556 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2557 struct page
**hpage
)
2558 __releases(&khugepaged_mm_lock
)
2559 __acquires(&khugepaged_mm_lock
)
2561 struct mm_slot
*mm_slot
;
2562 struct mm_struct
*mm
;
2563 struct vm_area_struct
*vma
;
2567 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2569 if (khugepaged_scan
.mm_slot
)
2570 mm_slot
= khugepaged_scan
.mm_slot
;
2572 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2573 struct mm_slot
, mm_node
);
2574 khugepaged_scan
.address
= 0;
2575 khugepaged_scan
.mm_slot
= mm_slot
;
2577 spin_unlock(&khugepaged_mm_lock
);
2580 down_read(&mm
->mmap_sem
);
2581 if (unlikely(khugepaged_test_exit(mm
)))
2584 vma
= find_vma(mm
, khugepaged_scan
.address
);
2587 for (; vma
; vma
= vma
->vm_next
) {
2588 unsigned long hstart
, hend
;
2591 if (unlikely(khugepaged_test_exit(mm
))) {
2595 if (!hugepage_vma_check(vma
)) {
2600 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2601 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2604 if (khugepaged_scan
.address
> hend
)
2606 if (khugepaged_scan
.address
< hstart
)
2607 khugepaged_scan
.address
= hstart
;
2608 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2610 while (khugepaged_scan
.address
< hend
) {
2613 if (unlikely(khugepaged_test_exit(mm
)))
2614 goto breakouterloop
;
2616 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2617 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2619 ret
= khugepaged_scan_pmd(mm
, vma
,
2620 khugepaged_scan
.address
,
2622 /* move to next address */
2623 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2624 progress
+= HPAGE_PMD_NR
;
2626 /* we released mmap_sem so break loop */
2627 goto breakouterloop_mmap_sem
;
2628 if (progress
>= pages
)
2629 goto breakouterloop
;
2633 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
2634 breakouterloop_mmap_sem
:
2636 spin_lock(&khugepaged_mm_lock
);
2637 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2639 * Release the current mm_slot if this mm is about to die, or
2640 * if we scanned all vmas of this mm.
2642 if (khugepaged_test_exit(mm
) || !vma
) {
2644 * Make sure that if mm_users is reaching zero while
2645 * khugepaged runs here, khugepaged_exit will find
2646 * mm_slot not pointing to the exiting mm.
2648 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2649 khugepaged_scan
.mm_slot
= list_entry(
2650 mm_slot
->mm_node
.next
,
2651 struct mm_slot
, mm_node
);
2652 khugepaged_scan
.address
= 0;
2654 khugepaged_scan
.mm_slot
= NULL
;
2655 khugepaged_full_scans
++;
2658 collect_mm_slot(mm_slot
);
2664 static int khugepaged_has_work(void)
2666 return !list_empty(&khugepaged_scan
.mm_head
) &&
2667 khugepaged_enabled();
2670 static int khugepaged_wait_event(void)
2672 return !list_empty(&khugepaged_scan
.mm_head
) ||
2673 kthread_should_stop();
2676 static void khugepaged_do_scan(void)
2678 struct page
*hpage
= NULL
;
2679 unsigned int progress
= 0, pass_through_head
= 0;
2680 unsigned int pages
= khugepaged_pages_to_scan
;
2683 barrier(); /* write khugepaged_pages_to_scan to local stack */
2685 while (progress
< pages
) {
2686 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2691 if (unlikely(kthread_should_stop() || try_to_freeze()))
2694 spin_lock(&khugepaged_mm_lock
);
2695 if (!khugepaged_scan
.mm_slot
)
2696 pass_through_head
++;
2697 if (khugepaged_has_work() &&
2698 pass_through_head
< 2)
2699 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2703 spin_unlock(&khugepaged_mm_lock
);
2706 if (!IS_ERR_OR_NULL(hpage
))
2710 static void khugepaged_wait_work(void)
2712 if (khugepaged_has_work()) {
2713 if (!khugepaged_scan_sleep_millisecs
)
2716 wait_event_freezable_timeout(khugepaged_wait
,
2717 kthread_should_stop(),
2718 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
));
2722 if (khugepaged_enabled())
2723 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2726 static int khugepaged(void *none
)
2728 struct mm_slot
*mm_slot
;
2731 set_user_nice(current
, MAX_NICE
);
2733 while (!kthread_should_stop()) {
2734 khugepaged_do_scan();
2735 khugepaged_wait_work();
2738 spin_lock(&khugepaged_mm_lock
);
2739 mm_slot
= khugepaged_scan
.mm_slot
;
2740 khugepaged_scan
.mm_slot
= NULL
;
2742 collect_mm_slot(mm_slot
);
2743 spin_unlock(&khugepaged_mm_lock
);
2747 static void __split_huge_zero_page_pmd(struct vm_area_struct
*vma
,
2748 unsigned long haddr
, pmd_t
*pmd
)
2750 struct mm_struct
*mm
= vma
->vm_mm
;
2755 /* leave pmd empty until pte is filled */
2756 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2758 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2759 pmd_populate(mm
, &_pmd
, pgtable
);
2761 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2763 entry
= pfn_pte(my_zero_pfn(haddr
), vma
->vm_page_prot
);
2764 entry
= pte_mkspecial(entry
);
2765 pte
= pte_offset_map(&_pmd
, haddr
);
2766 VM_BUG_ON(!pte_none(*pte
));
2767 set_pte_at(mm
, haddr
, pte
, entry
);
2770 smp_wmb(); /* make pte visible before pmd */
2771 pmd_populate(mm
, pmd
, pgtable
);
2772 put_huge_zero_page();
2775 static void __split_huge_pmd_locked(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2776 unsigned long haddr
, bool freeze
)
2778 struct mm_struct
*mm
= vma
->vm_mm
;
2782 bool young
, write
, dirty
;
2785 VM_BUG_ON(haddr
& ~HPAGE_PMD_MASK
);
2786 VM_BUG_ON_VMA(vma
->vm_start
> haddr
, vma
);
2787 VM_BUG_ON_VMA(vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
, vma
);
2788 VM_BUG_ON(!pmd_trans_huge(*pmd
));
2790 count_vm_event(THP_SPLIT_PMD
);
2792 if (vma_is_dax(vma
)) {
2793 pmd_t _pmd
= pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2794 if (is_huge_zero_pmd(_pmd
))
2795 put_huge_zero_page();
2797 } else if (is_huge_zero_pmd(*pmd
)) {
2798 return __split_huge_zero_page_pmd(vma
, haddr
, pmd
);
2801 page
= pmd_page(*pmd
);
2802 VM_BUG_ON_PAGE(!page_count(page
), page
);
2803 atomic_add(HPAGE_PMD_NR
- 1, &page
->_count
);
2804 write
= pmd_write(*pmd
);
2805 young
= pmd_young(*pmd
);
2806 dirty
= pmd_dirty(*pmd
);
2808 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2809 pmd_populate(mm
, &_pmd
, pgtable
);
2811 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2814 * Note that NUMA hinting access restrictions are not
2815 * transferred to avoid any possibility of altering
2816 * permissions across VMAs.
2819 swp_entry_t swp_entry
;
2820 swp_entry
= make_migration_entry(page
+ i
, write
);
2821 entry
= swp_entry_to_pte(swp_entry
);
2823 entry
= mk_pte(page
+ i
, vma
->vm_page_prot
);
2824 entry
= maybe_mkwrite(entry
, vma
);
2826 entry
= pte_wrprotect(entry
);
2828 entry
= pte_mkold(entry
);
2831 SetPageDirty(page
+ i
);
2832 pte
= pte_offset_map(&_pmd
, haddr
);
2833 BUG_ON(!pte_none(*pte
));
2834 set_pte_at(mm
, haddr
, pte
, entry
);
2835 atomic_inc(&page
[i
]._mapcount
);
2840 * Set PG_double_map before dropping compound_mapcount to avoid
2841 * false-negative page_mapped().
2843 if (compound_mapcount(page
) > 1 && !TestSetPageDoubleMap(page
)) {
2844 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2845 atomic_inc(&page
[i
]._mapcount
);
2848 if (atomic_add_negative(-1, compound_mapcount_ptr(page
))) {
2849 /* Last compound_mapcount is gone. */
2850 __dec_zone_page_state(page
, NR_ANON_TRANSPARENT_HUGEPAGES
);
2851 if (TestClearPageDoubleMap(page
)) {
2852 /* No need in mapcount reference anymore */
2853 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2854 atomic_dec(&page
[i
]._mapcount
);
2858 smp_wmb(); /* make pte visible before pmd */
2860 * Up to this point the pmd is present and huge and userland has the
2861 * whole access to the hugepage during the split (which happens in
2862 * place). If we overwrite the pmd with the not-huge version pointing
2863 * to the pte here (which of course we could if all CPUs were bug
2864 * free), userland could trigger a small page size TLB miss on the
2865 * small sized TLB while the hugepage TLB entry is still established in
2866 * the huge TLB. Some CPU doesn't like that.
2867 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2868 * 383 on page 93. Intel should be safe but is also warns that it's
2869 * only safe if the permission and cache attributes of the two entries
2870 * loaded in the two TLB is identical (which should be the case here).
2871 * But it is generally safer to never allow small and huge TLB entries
2872 * for the same virtual address to be loaded simultaneously. So instead
2873 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2874 * current pmd notpresent (atomically because here the pmd_trans_huge
2875 * and pmd_trans_splitting must remain set at all times on the pmd
2876 * until the split is complete for this pmd), then we flush the SMP TLB
2877 * and finally we write the non-huge version of the pmd entry with
2880 pmdp_invalidate(vma
, haddr
, pmd
);
2881 pmd_populate(mm
, pmd
, pgtable
);
2884 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2885 page_remove_rmap(page
+ i
, false);
2891 void __split_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2892 unsigned long address
)
2895 struct mm_struct
*mm
= vma
->vm_mm
;
2896 struct page
*page
= NULL
;
2897 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
2899 mmu_notifier_invalidate_range_start(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
2900 ptl
= pmd_lock(mm
, pmd
);
2901 if (unlikely(!pmd_trans_huge(*pmd
)))
2903 page
= pmd_page(*pmd
);
2904 __split_huge_pmd_locked(vma
, pmd
, haddr
, false);
2905 if (PageMlocked(page
))
2911 mmu_notifier_invalidate_range_end(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
2914 munlock_vma_page(page
);
2920 static void split_huge_pmd_address(struct vm_area_struct
*vma
,
2921 unsigned long address
)
2927 VM_BUG_ON(!(address
& ~HPAGE_PMD_MASK
));
2929 pgd
= pgd_offset(vma
->vm_mm
, address
);
2930 if (!pgd_present(*pgd
))
2933 pud
= pud_offset(pgd
, address
);
2934 if (!pud_present(*pud
))
2937 pmd
= pmd_offset(pud
, address
);
2938 if (!pmd_present(*pmd
) || !pmd_trans_huge(*pmd
))
2941 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2942 * materialize from under us.
2944 split_huge_pmd(vma
, pmd
, address
);
2947 void vma_adjust_trans_huge(struct vm_area_struct
*vma
,
2948 unsigned long start
,
2953 * If the new start address isn't hpage aligned and it could
2954 * previously contain an hugepage: check if we need to split
2957 if (start
& ~HPAGE_PMD_MASK
&&
2958 (start
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
2959 (start
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
2960 split_huge_pmd_address(vma
, start
);
2963 * If the new end address isn't hpage aligned and it could
2964 * previously contain an hugepage: check if we need to split
2967 if (end
& ~HPAGE_PMD_MASK
&&
2968 (end
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
2969 (end
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
2970 split_huge_pmd_address(vma
, end
);
2973 * If we're also updating the vma->vm_next->vm_start, if the new
2974 * vm_next->vm_start isn't page aligned and it could previously
2975 * contain an hugepage: check if we need to split an huge pmd.
2977 if (adjust_next
> 0) {
2978 struct vm_area_struct
*next
= vma
->vm_next
;
2979 unsigned long nstart
= next
->vm_start
;
2980 nstart
+= adjust_next
<< PAGE_SHIFT
;
2981 if (nstart
& ~HPAGE_PMD_MASK
&&
2982 (nstart
& HPAGE_PMD_MASK
) >= next
->vm_start
&&
2983 (nstart
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= next
->vm_end
)
2984 split_huge_pmd_address(next
, nstart
);
2988 static void freeze_page_vma(struct vm_area_struct
*vma
, struct page
*page
,
2989 unsigned long address
)
2991 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
2997 int i
, nr
= HPAGE_PMD_NR
;
2999 /* Skip pages which doesn't belong to the VMA */
3000 if (address
< vma
->vm_start
) {
3001 int off
= (vma
->vm_start
- address
) >> PAGE_SHIFT
;
3004 address
= vma
->vm_start
;
3007 pgd
= pgd_offset(vma
->vm_mm
, address
);
3008 if (!pgd_present(*pgd
))
3010 pud
= pud_offset(pgd
, address
);
3011 if (!pud_present(*pud
))
3013 pmd
= pmd_offset(pud
, address
);
3014 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
3015 if (!pmd_present(*pmd
)) {
3019 if (pmd_trans_huge(*pmd
)) {
3020 if (page
== pmd_page(*pmd
))
3021 __split_huge_pmd_locked(vma
, pmd
, haddr
, true);
3027 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, address
, &ptl
);
3028 for (i
= 0; i
< nr
; i
++, address
+= PAGE_SIZE
, page
++, pte
++) {
3029 pte_t entry
, swp_pte
;
3030 swp_entry_t swp_entry
;
3033 * We've just crossed page table boundary: need to map next one.
3034 * It can happen if THP was mremaped to non PMD-aligned address.
3036 if (unlikely(address
== haddr
+ HPAGE_PMD_SIZE
)) {
3037 pte_unmap_unlock(pte
- 1, ptl
);
3038 pmd
= mm_find_pmd(vma
->vm_mm
, address
);
3041 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
,
3045 if (!pte_present(*pte
))
3047 if (page_to_pfn(page
) != pte_pfn(*pte
))
3049 flush_cache_page(vma
, address
, page_to_pfn(page
));
3050 entry
= ptep_clear_flush(vma
, address
, pte
);
3051 if (pte_dirty(entry
))
3053 swp_entry
= make_migration_entry(page
, pte_write(entry
));
3054 swp_pte
= swp_entry_to_pte(swp_entry
);
3055 if (pte_soft_dirty(entry
))
3056 swp_pte
= pte_swp_mksoft_dirty(swp_pte
);
3057 set_pte_at(vma
->vm_mm
, address
, pte
, swp_pte
);
3058 page_remove_rmap(page
, false);
3061 pte_unmap_unlock(pte
- 1, ptl
);
3064 static void freeze_page(struct anon_vma
*anon_vma
, struct page
*page
)
3066 struct anon_vma_chain
*avc
;
3067 pgoff_t pgoff
= page_to_pgoff(page
);
3069 VM_BUG_ON_PAGE(!PageHead(page
), page
);
3071 anon_vma_interval_tree_foreach(avc
, &anon_vma
->rb_root
, pgoff
,
3072 pgoff
+ HPAGE_PMD_NR
- 1) {
3073 unsigned long address
= __vma_address(page
, avc
->vma
);
3075 mmu_notifier_invalidate_range_start(avc
->vma
->vm_mm
,
3076 address
, address
+ HPAGE_PMD_SIZE
);
3077 freeze_page_vma(avc
->vma
, page
, address
);
3078 mmu_notifier_invalidate_range_end(avc
->vma
->vm_mm
,
3079 address
, address
+ HPAGE_PMD_SIZE
);
3083 static void unfreeze_page_vma(struct vm_area_struct
*vma
, struct page
*page
,
3084 unsigned long address
)
3089 swp_entry_t swp_entry
;
3090 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
3091 int i
, nr
= HPAGE_PMD_NR
;
3093 /* Skip pages which doesn't belong to the VMA */
3094 if (address
< vma
->vm_start
) {
3095 int off
= (vma
->vm_start
- address
) >> PAGE_SHIFT
;
3098 address
= vma
->vm_start
;
3101 pmd
= mm_find_pmd(vma
->vm_mm
, address
);
3105 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, address
, &ptl
);
3106 for (i
= 0; i
< nr
; i
++, address
+= PAGE_SIZE
, page
++, pte
++) {
3108 * We've just crossed page table boundary: need to map next one.
3109 * It can happen if THP was mremaped to non-PMD aligned address.
3111 if (unlikely(address
== haddr
+ HPAGE_PMD_SIZE
)) {
3112 pte_unmap_unlock(pte
- 1, ptl
);
3113 pmd
= mm_find_pmd(vma
->vm_mm
, address
);
3116 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
,
3120 if (!is_swap_pte(*pte
))
3123 swp_entry
= pte_to_swp_entry(*pte
);
3124 if (!is_migration_entry(swp_entry
))
3126 if (migration_entry_to_page(swp_entry
) != page
)
3130 page_add_anon_rmap(page
, vma
, address
, false);
3132 entry
= pte_mkold(mk_pte(page
, vma
->vm_page_prot
));
3133 if (PageDirty(page
))
3134 entry
= pte_mkdirty(entry
);
3135 if (is_write_migration_entry(swp_entry
))
3136 entry
= maybe_mkwrite(entry
, vma
);
3138 flush_dcache_page(page
);
3139 set_pte_at(vma
->vm_mm
, address
, pte
, entry
);
3141 /* No need to invalidate - it was non-present before */
3142 update_mmu_cache(vma
, address
, pte
);
3144 pte_unmap_unlock(pte
- 1, ptl
);
3147 static void unfreeze_page(struct anon_vma
*anon_vma
, struct page
*page
)
3149 struct anon_vma_chain
*avc
;
3150 pgoff_t pgoff
= page_to_pgoff(page
);
3152 anon_vma_interval_tree_foreach(avc
, &anon_vma
->rb_root
,
3153 pgoff
, pgoff
+ HPAGE_PMD_NR
- 1) {
3154 unsigned long address
= __vma_address(page
, avc
->vma
);
3156 mmu_notifier_invalidate_range_start(avc
->vma
->vm_mm
,
3157 address
, address
+ HPAGE_PMD_SIZE
);
3158 unfreeze_page_vma(avc
->vma
, page
, address
);
3159 mmu_notifier_invalidate_range_end(avc
->vma
->vm_mm
,
3160 address
, address
+ HPAGE_PMD_SIZE
);
3164 static int __split_huge_page_tail(struct page
*head
, int tail
,
3165 struct lruvec
*lruvec
, struct list_head
*list
)
3168 struct page
*page_tail
= head
+ tail
;
3170 mapcount
= atomic_read(&page_tail
->_mapcount
) + 1;
3171 VM_BUG_ON_PAGE(atomic_read(&page_tail
->_count
) != 0, page_tail
);
3174 * tail_page->_count is zero and not changing from under us. But
3175 * get_page_unless_zero() may be running from under us on the
3176 * tail_page. If we used atomic_set() below instead of atomic_add(), we
3177 * would then run atomic_set() concurrently with
3178 * get_page_unless_zero(), and atomic_set() is implemented in C not
3179 * using locked ops. spin_unlock on x86 sometime uses locked ops
3180 * because of PPro errata 66, 92, so unless somebody can guarantee
3181 * atomic_set() here would be safe on all archs (and not only on x86),
3182 * it's safer to use atomic_add().
3184 atomic_add(mapcount
+ 1, &page_tail
->_count
);
3187 page_tail
->flags
&= ~PAGE_FLAGS_CHECK_AT_PREP
;
3188 page_tail
->flags
|= (head
->flags
&
3189 ((1L << PG_referenced
) |
3190 (1L << PG_swapbacked
) |
3191 (1L << PG_mlocked
) |
3192 (1L << PG_uptodate
) |
3195 (1L << PG_unevictable
) |
3199 * After clearing PageTail the gup refcount can be released.
3200 * Page flags also must be visible before we make the page non-compound.
3204 clear_compound_head(page_tail
);
3206 if (page_is_young(head
))
3207 set_page_young(page_tail
);
3208 if (page_is_idle(head
))
3209 set_page_idle(page_tail
);
3211 /* ->mapping in first tail page is compound_mapcount */
3212 VM_BUG_ON_PAGE(tail
> 2 && page_tail
->mapping
!= TAIL_MAPPING
,
3214 page_tail
->mapping
= head
->mapping
;
3216 page_tail
->index
= head
->index
+ tail
;
3217 page_cpupid_xchg_last(page_tail
, page_cpupid_last(head
));
3218 lru_add_page_tail(head
, page_tail
, lruvec
, list
);
3223 static void __split_huge_page(struct page
*page
, struct list_head
*list
)
3225 struct page
*head
= compound_head(page
);
3226 struct zone
*zone
= page_zone(head
);
3227 struct lruvec
*lruvec
;
3228 int i
, tail_mapcount
;
3230 /* prevent PageLRU to go away from under us, and freeze lru stats */
3231 spin_lock_irq(&zone
->lru_lock
);
3232 lruvec
= mem_cgroup_page_lruvec(head
, zone
);
3234 /* complete memcg works before add pages to LRU */
3235 mem_cgroup_split_huge_fixup(head
);
3238 for (i
= HPAGE_PMD_NR
- 1; i
>= 1; i
--)
3239 tail_mapcount
+= __split_huge_page_tail(head
, i
, lruvec
, list
);
3240 atomic_sub(tail_mapcount
, &head
->_count
);
3242 ClearPageCompound(head
);
3243 spin_unlock_irq(&zone
->lru_lock
);
3245 unfreeze_page(page_anon_vma(head
), head
);
3247 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3248 struct page
*subpage
= head
+ i
;
3249 if (subpage
== page
)
3251 unlock_page(subpage
);
3254 * Subpages may be freed if there wasn't any mapping
3255 * like if add_to_swap() is running on a lru page that
3256 * had its mapping zapped. And freeing these pages
3257 * requires taking the lru_lock so we do the put_page
3258 * of the tail pages after the split is complete.
3264 int total_mapcount(struct page
*page
)
3268 VM_BUG_ON_PAGE(PageTail(page
), page
);
3270 if (likely(!PageCompound(page
)))
3271 return atomic_read(&page
->_mapcount
) + 1;
3273 ret
= compound_mapcount(page
);
3276 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3277 ret
+= atomic_read(&page
[i
]._mapcount
) + 1;
3278 if (PageDoubleMap(page
))
3279 ret
-= HPAGE_PMD_NR
;
3284 * This function splits huge page into normal pages. @page can point to any
3285 * subpage of huge page to split. Split doesn't change the position of @page.
3287 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3288 * The huge page must be locked.
3290 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3292 * Both head page and tail pages will inherit mapping, flags, and so on from
3295 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3296 * they are not mapped.
3298 * Returns 0 if the hugepage is split successfully.
3299 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3302 int split_huge_page_to_list(struct page
*page
, struct list_head
*list
)
3304 struct page
*head
= compound_head(page
);
3305 struct anon_vma
*anon_vma
;
3306 int count
, mapcount
, ret
;
3309 VM_BUG_ON_PAGE(is_huge_zero_page(page
), page
);
3310 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
3311 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
3312 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
3313 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
3316 * The caller does not necessarily hold an mmap_sem that would prevent
3317 * the anon_vma disappearing so we first we take a reference to it
3318 * and then lock the anon_vma for write. This is similar to
3319 * page_lock_anon_vma_read except the write lock is taken to serialise
3320 * against parallel split or collapse operations.
3322 anon_vma
= page_get_anon_vma(head
);
3327 anon_vma_lock_write(anon_vma
);
3330 * Racy check if we can split the page, before freeze_page() will
3333 if (total_mapcount(head
) != page_count(head
) - 1) {
3338 mlocked
= PageMlocked(page
);
3339 freeze_page(anon_vma
, head
);
3340 VM_BUG_ON_PAGE(compound_mapcount(head
), head
);
3342 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3346 /* Prevent deferred_split_scan() touching ->_count */
3347 spin_lock(&split_queue_lock
);
3348 count
= page_count(head
);
3349 mapcount
= total_mapcount(head
);
3350 if (!mapcount
&& count
== 1) {
3351 if (!list_empty(page_deferred_list(head
))) {
3353 list_del(page_deferred_list(head
));
3355 spin_unlock(&split_queue_lock
);
3356 __split_huge_page(page
, list
);
3358 } else if (IS_ENABLED(CONFIG_DEBUG_VM
) && mapcount
) {
3359 spin_unlock(&split_queue_lock
);
3360 pr_alert("total_mapcount: %u, page_count(): %u\n",
3363 dump_page(head
, NULL
);
3364 dump_page(page
, "total_mapcount(head) > 0");
3367 spin_unlock(&split_queue_lock
);
3368 unfreeze_page(anon_vma
, head
);
3373 anon_vma_unlock_write(anon_vma
);
3374 put_anon_vma(anon_vma
);
3376 count_vm_event(!ret
? THP_SPLIT_PAGE
: THP_SPLIT_PAGE_FAILED
);
3380 void free_transhuge_page(struct page
*page
)
3382 unsigned long flags
;
3384 spin_lock_irqsave(&split_queue_lock
, flags
);
3385 if (!list_empty(page_deferred_list(page
))) {
3387 list_del(page_deferred_list(page
));
3389 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3390 free_compound_page(page
);
3393 void deferred_split_huge_page(struct page
*page
)
3395 unsigned long flags
;
3397 VM_BUG_ON_PAGE(!PageTransHuge(page
), page
);
3399 spin_lock_irqsave(&split_queue_lock
, flags
);
3400 if (list_empty(page_deferred_list(page
))) {
3401 list_add_tail(page_deferred_list(page
), &split_queue
);
3404 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3407 static unsigned long deferred_split_count(struct shrinker
*shrink
,
3408 struct shrink_control
*sc
)
3411 * Split a page from split_queue will free up at least one page,
3412 * at most HPAGE_PMD_NR - 1. We don't track exact number.
3413 * Let's use HPAGE_PMD_NR / 2 as ballpark.
3415 return ACCESS_ONCE(split_queue_len
) * HPAGE_PMD_NR
/ 2;
3418 static unsigned long deferred_split_scan(struct shrinker
*shrink
,
3419 struct shrink_control
*sc
)
3421 unsigned long flags
;
3422 LIST_HEAD(list
), *pos
, *next
;
3426 spin_lock_irqsave(&split_queue_lock
, flags
);
3427 list_splice_init(&split_queue
, &list
);
3429 /* Take pin on all head pages to avoid freeing them under us */
3430 list_for_each_safe(pos
, next
, &list
) {
3431 page
= list_entry((void *)pos
, struct page
, mapping
);
3432 page
= compound_head(page
);
3433 /* race with put_compound_page() */
3434 if (!get_page_unless_zero(page
)) {
3435 list_del_init(page_deferred_list(page
));
3439 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3441 list_for_each_safe(pos
, next
, &list
) {
3442 page
= list_entry((void *)pos
, struct page
, mapping
);
3444 /* split_huge_page() removes page from list on success */
3445 if (!split_huge_page(page
))
3451 spin_lock_irqsave(&split_queue_lock
, flags
);
3452 list_splice_tail(&list
, &split_queue
);
3453 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3455 return split
* HPAGE_PMD_NR
/ 2;
3458 static struct shrinker deferred_split_shrinker
= {
3459 .count_objects
= deferred_split_count
,
3460 .scan_objects
= deferred_split_scan
,
3461 .seeks
= DEFAULT_SEEKS
,
3464 #ifdef CONFIG_DEBUG_FS
3465 static int split_huge_pages_set(void *data
, u64 val
)
3469 unsigned long pfn
, max_zone_pfn
;
3470 unsigned long total
= 0, split
= 0;
3475 for_each_populated_zone(zone
) {
3476 max_zone_pfn
= zone_end_pfn(zone
);
3477 for (pfn
= zone
->zone_start_pfn
; pfn
< max_zone_pfn
; pfn
++) {
3478 if (!pfn_valid(pfn
))
3481 page
= pfn_to_page(pfn
);
3482 if (!get_page_unless_zero(page
))
3485 if (zone
!= page_zone(page
))
3488 if (!PageHead(page
) || !PageAnon(page
) ||
3494 if (!split_huge_page(page
))
3502 pr_info("%lu of %lu THP split", split
, total
);
3506 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops
, NULL
, split_huge_pages_set
,
3509 static int __init
split_huge_pages_debugfs(void)
3513 ret
= debugfs_create_file("split_huge_pages", 0644, NULL
, NULL
,
3514 &split_huge_pages_fops
);
3516 pr_warn("Failed to create split_huge_pages in debugfs");
3519 late_initcall(split_huge_pages_debugfs
);