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>
35 #include <asm/pgalloc.h>
45 SCAN_NO_REFERENCED_PAGE
,
59 SCAN_ALLOC_HUGE_PAGE_FAIL
,
60 SCAN_CGROUP_CHARGE_FAIL
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/huge_memory.h>
67 * By default transparent hugepage support is disabled in order that avoid
68 * to risk increase the memory footprint of applications without a guaranteed
69 * benefit. When transparent hugepage support is enabled, is for all mappings,
70 * and khugepaged scans all mappings.
71 * Defrag is invoked by khugepaged hugepage allocations and by page faults
72 * for all hugepage allocations.
74 unsigned long transparent_hugepage_flags __read_mostly
=
75 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
76 (1<<TRANSPARENT_HUGEPAGE_FLAG
)|
78 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
79 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
)|
81 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
)|
82 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
)|
83 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
85 /* default scan 8*512 pte (or vmas) every 30 second */
86 static unsigned int khugepaged_pages_to_scan __read_mostly
;
87 static unsigned int khugepaged_pages_collapsed
;
88 static unsigned int khugepaged_full_scans
;
89 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly
= 10000;
90 /* during fragmentation poll the hugepage allocator once every minute */
91 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly
= 60000;
92 static unsigned long khugepaged_sleep_expire
;
93 static struct task_struct
*khugepaged_thread __read_mostly
;
94 static DEFINE_MUTEX(khugepaged_mutex
);
95 static DEFINE_SPINLOCK(khugepaged_mm_lock
);
96 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait
);
98 * default collapse hugepages if there is at least one pte mapped like
99 * it would have happened if the vma was large enough during page
102 static unsigned int khugepaged_max_ptes_none __read_mostly
;
104 static int khugepaged(void *none
);
105 static int khugepaged_slab_init(void);
106 static void khugepaged_slab_exit(void);
108 #define MM_SLOTS_HASH_BITS 10
109 static __read_mostly
DEFINE_HASHTABLE(mm_slots_hash
, MM_SLOTS_HASH_BITS
);
111 static struct kmem_cache
*mm_slot_cache __read_mostly
;
114 * struct mm_slot - hash lookup from mm to mm_slot
115 * @hash: hash collision list
116 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
117 * @mm: the mm that this information is valid for
120 struct hlist_node hash
;
121 struct list_head mm_node
;
122 struct mm_struct
*mm
;
126 * struct khugepaged_scan - cursor for scanning
127 * @mm_head: the head of the mm list to scan
128 * @mm_slot: the current mm_slot we are scanning
129 * @address: the next address inside that to be scanned
131 * There is only the one khugepaged_scan instance of this cursor structure.
133 struct khugepaged_scan
{
134 struct list_head mm_head
;
135 struct mm_slot
*mm_slot
;
136 unsigned long address
;
138 static struct khugepaged_scan khugepaged_scan
= {
139 .mm_head
= LIST_HEAD_INIT(khugepaged_scan
.mm_head
),
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 to help transparent hugepage allocations\n",
173 min_free_kbytes
, recommended_min
);
175 min_free_kbytes
= recommended_min
;
177 setup_per_zone_wmarks();
180 static int start_stop_khugepaged(void)
183 if (khugepaged_enabled()) {
184 if (!khugepaged_thread
)
185 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
187 if (IS_ERR(khugepaged_thread
)) {
188 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
189 err
= PTR_ERR(khugepaged_thread
);
190 khugepaged_thread
= NULL
;
194 if (!list_empty(&khugepaged_scan
.mm_head
))
195 wake_up_interruptible(&khugepaged_wait
);
197 set_recommended_min_free_kbytes();
198 } else if (khugepaged_thread
) {
199 kthread_stop(khugepaged_thread
);
200 khugepaged_thread
= NULL
;
206 static atomic_t huge_zero_refcount
;
207 struct page
*huge_zero_page __read_mostly
;
209 struct page
*get_huge_zero_page(void)
211 struct page
*zero_page
;
213 if (likely(atomic_inc_not_zero(&huge_zero_refcount
)))
214 return READ_ONCE(huge_zero_page
);
216 zero_page
= alloc_pages((GFP_TRANSHUGE
| __GFP_ZERO
) & ~__GFP_MOVABLE
,
219 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED
);
222 count_vm_event(THP_ZERO_PAGE_ALLOC
);
224 if (cmpxchg(&huge_zero_page
, NULL
, zero_page
)) {
226 __free_pages(zero_page
, compound_order(zero_page
));
230 /* We take additional reference here. It will be put back by shrinker */
231 atomic_set(&huge_zero_refcount
, 2);
233 return READ_ONCE(huge_zero_page
);
236 void put_huge_zero_page(void)
239 * Counter should never go to zero here. Only shrinker can put
242 BUG_ON(atomic_dec_and_test(&huge_zero_refcount
));
245 static unsigned long shrink_huge_zero_page_count(struct shrinker
*shrink
,
246 struct shrink_control
*sc
)
248 /* we can free zero page only if last reference remains */
249 return atomic_read(&huge_zero_refcount
) == 1 ? HPAGE_PMD_NR
: 0;
252 static unsigned long shrink_huge_zero_page_scan(struct shrinker
*shrink
,
253 struct shrink_control
*sc
)
255 if (atomic_cmpxchg(&huge_zero_refcount
, 1, 0) == 1) {
256 struct page
*zero_page
= xchg(&huge_zero_page
, NULL
);
257 BUG_ON(zero_page
== NULL
);
258 __free_pages(zero_page
, compound_order(zero_page
));
265 static struct shrinker huge_zero_page_shrinker
= {
266 .count_objects
= shrink_huge_zero_page_count
,
267 .scan_objects
= shrink_huge_zero_page_scan
,
268 .seeks
= DEFAULT_SEEKS
,
273 static ssize_t
triple_flag_store(struct kobject
*kobj
,
274 struct kobj_attribute
*attr
,
275 const char *buf
, size_t count
,
276 enum transparent_hugepage_flag enabled
,
277 enum transparent_hugepage_flag deferred
,
278 enum transparent_hugepage_flag req_madv
)
280 if (!memcmp("defer", buf
,
281 min(sizeof("defer")-1, count
))) {
282 if (enabled
== deferred
)
284 clear_bit(enabled
, &transparent_hugepage_flags
);
285 clear_bit(req_madv
, &transparent_hugepage_flags
);
286 set_bit(deferred
, &transparent_hugepage_flags
);
287 } else if (!memcmp("always", buf
,
288 min(sizeof("always")-1, count
))) {
289 clear_bit(deferred
, &transparent_hugepage_flags
);
290 clear_bit(req_madv
, &transparent_hugepage_flags
);
291 set_bit(enabled
, &transparent_hugepage_flags
);
292 } else if (!memcmp("madvise", buf
,
293 min(sizeof("madvise")-1, count
))) {
294 clear_bit(enabled
, &transparent_hugepage_flags
);
295 clear_bit(deferred
, &transparent_hugepage_flags
);
296 set_bit(req_madv
, &transparent_hugepage_flags
);
297 } else if (!memcmp("never", buf
,
298 min(sizeof("never")-1, count
))) {
299 clear_bit(enabled
, &transparent_hugepage_flags
);
300 clear_bit(req_madv
, &transparent_hugepage_flags
);
301 clear_bit(deferred
, &transparent_hugepage_flags
);
308 static ssize_t
enabled_show(struct kobject
*kobj
,
309 struct kobj_attribute
*attr
, char *buf
)
311 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG
, &transparent_hugepage_flags
))
312 return sprintf(buf
, "[always] madvise never\n");
313 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
, &transparent_hugepage_flags
))
314 return sprintf(buf
, "always [madvise] never\n");
316 return sprintf(buf
, "always madvise [never]\n");
319 static ssize_t
enabled_store(struct kobject
*kobj
,
320 struct kobj_attribute
*attr
,
321 const char *buf
, size_t count
)
325 ret
= triple_flag_store(kobj
, attr
, buf
, count
,
326 TRANSPARENT_HUGEPAGE_FLAG
,
327 TRANSPARENT_HUGEPAGE_FLAG
,
328 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
333 mutex_lock(&khugepaged_mutex
);
334 err
= start_stop_khugepaged();
335 mutex_unlock(&khugepaged_mutex
);
343 static struct kobj_attribute enabled_attr
=
344 __ATTR(enabled
, 0644, enabled_show
, enabled_store
);
346 static ssize_t
single_flag_show(struct kobject
*kobj
,
347 struct kobj_attribute
*attr
, char *buf
,
348 enum transparent_hugepage_flag flag
)
350 return sprintf(buf
, "%d\n",
351 !!test_bit(flag
, &transparent_hugepage_flags
));
354 static ssize_t
single_flag_store(struct kobject
*kobj
,
355 struct kobj_attribute
*attr
,
356 const char *buf
, size_t count
,
357 enum transparent_hugepage_flag flag
)
362 ret
= kstrtoul(buf
, 10, &value
);
369 set_bit(flag
, &transparent_hugepage_flags
);
371 clear_bit(flag
, &transparent_hugepage_flags
);
377 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
378 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
379 * memory just to allocate one more hugepage.
381 static ssize_t
defrag_show(struct kobject
*kobj
,
382 struct kobj_attribute
*attr
, char *buf
)
384 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
, &transparent_hugepage_flags
))
385 return sprintf(buf
, "[always] defer madvise never\n");
386 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
, &transparent_hugepage_flags
))
387 return sprintf(buf
, "always [defer] madvise never\n");
388 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
, &transparent_hugepage_flags
))
389 return sprintf(buf
, "always defer [madvise] never\n");
391 return sprintf(buf
, "always defer madvise [never]\n");
394 static ssize_t
defrag_store(struct kobject
*kobj
,
395 struct kobj_attribute
*attr
,
396 const char *buf
, size_t count
)
398 return triple_flag_store(kobj
, attr
, buf
, count
,
399 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
,
400 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
,
401 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
403 static struct kobj_attribute defrag_attr
=
404 __ATTR(defrag
, 0644, defrag_show
, defrag_store
);
406 static ssize_t
use_zero_page_show(struct kobject
*kobj
,
407 struct kobj_attribute
*attr
, char *buf
)
409 return single_flag_show(kobj
, attr
, buf
,
410 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
412 static ssize_t
use_zero_page_store(struct kobject
*kobj
,
413 struct kobj_attribute
*attr
, const char *buf
, size_t count
)
415 return single_flag_store(kobj
, attr
, buf
, count
,
416 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
418 static struct kobj_attribute use_zero_page_attr
=
419 __ATTR(use_zero_page
, 0644, use_zero_page_show
, use_zero_page_store
);
420 #ifdef CONFIG_DEBUG_VM
421 static ssize_t
debug_cow_show(struct kobject
*kobj
,
422 struct kobj_attribute
*attr
, char *buf
)
424 return single_flag_show(kobj
, attr
, buf
,
425 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
427 static ssize_t
debug_cow_store(struct kobject
*kobj
,
428 struct kobj_attribute
*attr
,
429 const char *buf
, size_t count
)
431 return single_flag_store(kobj
, attr
, buf
, count
,
432 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
434 static struct kobj_attribute debug_cow_attr
=
435 __ATTR(debug_cow
, 0644, debug_cow_show
, debug_cow_store
);
436 #endif /* CONFIG_DEBUG_VM */
438 static struct attribute
*hugepage_attr
[] = {
441 &use_zero_page_attr
.attr
,
442 #ifdef CONFIG_DEBUG_VM
443 &debug_cow_attr
.attr
,
448 static struct attribute_group hugepage_attr_group
= {
449 .attrs
= hugepage_attr
,
452 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
453 struct kobj_attribute
*attr
,
456 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
459 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
460 struct kobj_attribute
*attr
,
461 const char *buf
, size_t count
)
466 err
= kstrtoul(buf
, 10, &msecs
);
467 if (err
|| msecs
> UINT_MAX
)
470 khugepaged_scan_sleep_millisecs
= msecs
;
471 khugepaged_sleep_expire
= 0;
472 wake_up_interruptible(&khugepaged_wait
);
476 static struct kobj_attribute scan_sleep_millisecs_attr
=
477 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
478 scan_sleep_millisecs_store
);
480 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
481 struct kobj_attribute
*attr
,
484 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
487 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
488 struct kobj_attribute
*attr
,
489 const char *buf
, size_t count
)
494 err
= kstrtoul(buf
, 10, &msecs
);
495 if (err
|| msecs
> UINT_MAX
)
498 khugepaged_alloc_sleep_millisecs
= msecs
;
499 khugepaged_sleep_expire
= 0;
500 wake_up_interruptible(&khugepaged_wait
);
504 static struct kobj_attribute alloc_sleep_millisecs_attr
=
505 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
506 alloc_sleep_millisecs_store
);
508 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
509 struct kobj_attribute
*attr
,
512 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
514 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
515 struct kobj_attribute
*attr
,
516 const char *buf
, size_t count
)
521 err
= kstrtoul(buf
, 10, &pages
);
522 if (err
|| !pages
|| pages
> UINT_MAX
)
525 khugepaged_pages_to_scan
= pages
;
529 static struct kobj_attribute pages_to_scan_attr
=
530 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
531 pages_to_scan_store
);
533 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
534 struct kobj_attribute
*attr
,
537 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
539 static struct kobj_attribute pages_collapsed_attr
=
540 __ATTR_RO(pages_collapsed
);
542 static ssize_t
full_scans_show(struct kobject
*kobj
,
543 struct kobj_attribute
*attr
,
546 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
548 static struct kobj_attribute full_scans_attr
=
549 __ATTR_RO(full_scans
);
551 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
552 struct kobj_attribute
*attr
, char *buf
)
554 return single_flag_show(kobj
, attr
, buf
,
555 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
557 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
558 struct kobj_attribute
*attr
,
559 const char *buf
, size_t count
)
561 return single_flag_store(kobj
, attr
, buf
, count
,
562 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
564 static struct kobj_attribute khugepaged_defrag_attr
=
565 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
566 khugepaged_defrag_store
);
569 * max_ptes_none controls if khugepaged should collapse hugepages over
570 * any unmapped ptes in turn potentially increasing the memory
571 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
572 * reduce the available free memory in the system as it
573 * runs. Increasing max_ptes_none will instead potentially reduce the
574 * free memory in the system during the khugepaged scan.
576 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
577 struct kobj_attribute
*attr
,
580 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
582 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
583 struct kobj_attribute
*attr
,
584 const char *buf
, size_t count
)
587 unsigned long max_ptes_none
;
589 err
= kstrtoul(buf
, 10, &max_ptes_none
);
590 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
593 khugepaged_max_ptes_none
= max_ptes_none
;
597 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
598 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
599 khugepaged_max_ptes_none_store
);
601 static struct attribute
*khugepaged_attr
[] = {
602 &khugepaged_defrag_attr
.attr
,
603 &khugepaged_max_ptes_none_attr
.attr
,
604 &pages_to_scan_attr
.attr
,
605 &pages_collapsed_attr
.attr
,
606 &full_scans_attr
.attr
,
607 &scan_sleep_millisecs_attr
.attr
,
608 &alloc_sleep_millisecs_attr
.attr
,
612 static struct attribute_group khugepaged_attr_group
= {
613 .attrs
= khugepaged_attr
,
614 .name
= "khugepaged",
617 static int __init
hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
621 *hugepage_kobj
= kobject_create_and_add("transparent_hugepage", mm_kobj
);
622 if (unlikely(!*hugepage_kobj
)) {
623 pr_err("failed to create transparent hugepage kobject\n");
627 err
= sysfs_create_group(*hugepage_kobj
, &hugepage_attr_group
);
629 pr_err("failed to register transparent hugepage group\n");
633 err
= sysfs_create_group(*hugepage_kobj
, &khugepaged_attr_group
);
635 pr_err("failed to register transparent hugepage group\n");
636 goto remove_hp_group
;
642 sysfs_remove_group(*hugepage_kobj
, &hugepage_attr_group
);
644 kobject_put(*hugepage_kobj
);
648 static void __init
hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
650 sysfs_remove_group(hugepage_kobj
, &khugepaged_attr_group
);
651 sysfs_remove_group(hugepage_kobj
, &hugepage_attr_group
);
652 kobject_put(hugepage_kobj
);
655 static inline int hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
660 static inline void hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
663 #endif /* CONFIG_SYSFS */
665 static int __init
hugepage_init(void)
668 struct kobject
*hugepage_kobj
;
670 if (!has_transparent_hugepage()) {
671 transparent_hugepage_flags
= 0;
675 khugepaged_pages_to_scan
= HPAGE_PMD_NR
* 8;
676 khugepaged_max_ptes_none
= HPAGE_PMD_NR
- 1;
678 * hugepages can't be allocated by the buddy allocator
680 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER
>= MAX_ORDER
);
682 * we use page->mapping and page->index in second tail page
683 * as list_head: assuming THP order >= 2
685 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER
< 2);
687 err
= hugepage_init_sysfs(&hugepage_kobj
);
691 err
= khugepaged_slab_init();
695 err
= register_shrinker(&huge_zero_page_shrinker
);
697 goto err_hzp_shrinker
;
698 err
= register_shrinker(&deferred_split_shrinker
);
700 goto err_split_shrinker
;
703 * By default disable transparent hugepages on smaller systems,
704 * where the extra memory used could hurt more than TLB overhead
705 * is likely to save. The admin can still enable it through /sys.
707 if (totalram_pages
< (512 << (20 - PAGE_SHIFT
))) {
708 transparent_hugepage_flags
= 0;
712 err
= start_stop_khugepaged();
718 unregister_shrinker(&deferred_split_shrinker
);
720 unregister_shrinker(&huge_zero_page_shrinker
);
722 khugepaged_slab_exit();
724 hugepage_exit_sysfs(hugepage_kobj
);
728 subsys_initcall(hugepage_init
);
730 static int __init
setup_transparent_hugepage(char *str
)
735 if (!strcmp(str
, "always")) {
736 set_bit(TRANSPARENT_HUGEPAGE_FLAG
,
737 &transparent_hugepage_flags
);
738 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
739 &transparent_hugepage_flags
);
741 } else if (!strcmp(str
, "madvise")) {
742 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
743 &transparent_hugepage_flags
);
744 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
745 &transparent_hugepage_flags
);
747 } else if (!strcmp(str
, "never")) {
748 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
749 &transparent_hugepage_flags
);
750 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
751 &transparent_hugepage_flags
);
756 pr_warn("transparent_hugepage= cannot parse, ignored\n");
759 __setup("transparent_hugepage=", setup_transparent_hugepage
);
761 pmd_t
maybe_pmd_mkwrite(pmd_t pmd
, struct vm_area_struct
*vma
)
763 if (likely(vma
->vm_flags
& VM_WRITE
))
764 pmd
= pmd_mkwrite(pmd
);
768 static inline pmd_t
mk_huge_pmd(struct page
*page
, pgprot_t prot
)
770 return pmd_mkhuge(mk_pmd(page
, prot
));
773 static inline struct list_head
*page_deferred_list(struct page
*page
)
776 * ->lru in the tail pages is occupied by compound_head.
777 * Let's use ->mapping + ->index in the second tail page as list_head.
779 return (struct list_head
*)&page
[2].mapping
;
782 void prep_transhuge_page(struct page
*page
)
785 * we use page->mapping and page->indexlru in second tail page
786 * as list_head: assuming THP order >= 2
789 INIT_LIST_HEAD(page_deferred_list(page
));
790 set_compound_page_dtor(page
, TRANSHUGE_PAGE_DTOR
);
793 static int __do_huge_pmd_anonymous_page(struct mm_struct
*mm
,
794 struct vm_area_struct
*vma
,
795 unsigned long address
, pmd_t
*pmd
,
796 struct page
*page
, gfp_t gfp
,
799 struct mem_cgroup
*memcg
;
802 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
804 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
806 if (mem_cgroup_try_charge(page
, mm
, gfp
, &memcg
, true)) {
808 count_vm_event(THP_FAULT_FALLBACK
);
809 return VM_FAULT_FALLBACK
;
812 pgtable
= pte_alloc_one(mm
, haddr
);
813 if (unlikely(!pgtable
)) {
814 mem_cgroup_cancel_charge(page
, memcg
, true);
819 clear_huge_page(page
, haddr
, HPAGE_PMD_NR
);
821 * The memory barrier inside __SetPageUptodate makes sure that
822 * clear_huge_page writes become visible before the set_pmd_at()
825 __SetPageUptodate(page
);
827 ptl
= pmd_lock(mm
, pmd
);
828 if (unlikely(!pmd_none(*pmd
))) {
830 mem_cgroup_cancel_charge(page
, memcg
, true);
832 pte_free(mm
, pgtable
);
836 /* Deliver the page fault to userland */
837 if (userfaultfd_missing(vma
)) {
841 mem_cgroup_cancel_charge(page
, memcg
, true);
843 pte_free(mm
, pgtable
);
844 ret
= handle_userfault(vma
, address
, flags
,
846 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
850 entry
= mk_huge_pmd(page
, vma
->vm_page_prot
);
851 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
852 page_add_new_anon_rmap(page
, vma
, haddr
, true);
853 mem_cgroup_commit_charge(page
, memcg
, false, true);
854 lru_cache_add_active_or_unevictable(page
, vma
);
855 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
856 set_pmd_at(mm
, haddr
, pmd
, entry
);
857 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
858 atomic_long_inc(&mm
->nr_ptes
);
860 count_vm_event(THP_FAULT_ALLOC
);
867 * If THP is set to always then directly reclaim/compact as necessary
868 * If set to defer then do no reclaim and defer to khugepaged
869 * If set to madvise and the VMA is flagged then directly reclaim/compact
871 static inline gfp_t
alloc_hugepage_direct_gfpmask(struct vm_area_struct
*vma
)
873 gfp_t reclaim_flags
= 0;
875 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
, &transparent_hugepage_flags
) &&
876 (vma
->vm_flags
& VM_HUGEPAGE
))
877 reclaim_flags
= __GFP_DIRECT_RECLAIM
;
878 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
, &transparent_hugepage_flags
))
879 reclaim_flags
= __GFP_KSWAPD_RECLAIM
;
880 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
, &transparent_hugepage_flags
))
881 reclaim_flags
= __GFP_DIRECT_RECLAIM
;
883 return GFP_TRANSHUGE
| reclaim_flags
;
886 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
887 static inline gfp_t
alloc_hugepage_khugepaged_gfpmask(void)
889 return GFP_TRANSHUGE
| (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM
: 0);
892 /* Caller must hold page table lock. */
893 static bool set_huge_zero_page(pgtable_t pgtable
, struct mm_struct
*mm
,
894 struct vm_area_struct
*vma
, unsigned long haddr
, pmd_t
*pmd
,
895 struct page
*zero_page
)
900 entry
= mk_pmd(zero_page
, vma
->vm_page_prot
);
901 entry
= pmd_mkhuge(entry
);
903 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
904 set_pmd_at(mm
, haddr
, pmd
, entry
);
905 atomic_long_inc(&mm
->nr_ptes
);
909 int do_huge_pmd_anonymous_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
910 unsigned long address
, pmd_t
*pmd
,
915 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
917 if (haddr
< vma
->vm_start
|| haddr
+ HPAGE_PMD_SIZE
> vma
->vm_end
)
918 return VM_FAULT_FALLBACK
;
919 if (unlikely(anon_vma_prepare(vma
)))
921 if (unlikely(khugepaged_enter(vma
, vma
->vm_flags
)))
923 if (!(flags
& FAULT_FLAG_WRITE
) && !mm_forbids_zeropage(mm
) &&
924 transparent_hugepage_use_zero_page()) {
927 struct page
*zero_page
;
930 pgtable
= pte_alloc_one(mm
, haddr
);
931 if (unlikely(!pgtable
))
933 zero_page
= get_huge_zero_page();
934 if (unlikely(!zero_page
)) {
935 pte_free(mm
, pgtable
);
936 count_vm_event(THP_FAULT_FALLBACK
);
937 return VM_FAULT_FALLBACK
;
939 ptl
= pmd_lock(mm
, pmd
);
942 if (pmd_none(*pmd
)) {
943 if (userfaultfd_missing(vma
)) {
945 ret
= handle_userfault(vma
, address
, flags
,
947 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
949 set_huge_zero_page(pgtable
, mm
, vma
,
958 pte_free(mm
, pgtable
);
959 put_huge_zero_page();
963 gfp
= alloc_hugepage_direct_gfpmask(vma
);
964 page
= alloc_hugepage_vma(gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
965 if (unlikely(!page
)) {
966 count_vm_event(THP_FAULT_FALLBACK
);
967 return VM_FAULT_FALLBACK
;
969 prep_transhuge_page(page
);
970 return __do_huge_pmd_anonymous_page(mm
, vma
, address
, pmd
, page
, gfp
,
974 static void insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
975 pmd_t
*pmd
, pfn_t pfn
, pgprot_t prot
, bool write
)
977 struct mm_struct
*mm
= vma
->vm_mm
;
981 ptl
= pmd_lock(mm
, pmd
);
982 entry
= pmd_mkhuge(pfn_t_pmd(pfn
, prot
));
983 if (pfn_t_devmap(pfn
))
984 entry
= pmd_mkdevmap(entry
);
986 entry
= pmd_mkyoung(pmd_mkdirty(entry
));
987 entry
= maybe_pmd_mkwrite(entry
, vma
);
989 set_pmd_at(mm
, addr
, pmd
, entry
);
990 update_mmu_cache_pmd(vma
, addr
, pmd
);
994 int vmf_insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
995 pmd_t
*pmd
, pfn_t pfn
, bool write
)
997 pgprot_t pgprot
= vma
->vm_page_prot
;
999 * If we had pmd_special, we could avoid all these restrictions,
1000 * but we need to be consistent with PTEs and architectures that
1001 * can't support a 'special' bit.
1003 BUG_ON(!(vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)));
1004 BUG_ON((vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)) ==
1005 (VM_PFNMAP
|VM_MIXEDMAP
));
1006 BUG_ON((vma
->vm_flags
& VM_PFNMAP
) && is_cow_mapping(vma
->vm_flags
));
1007 BUG_ON(!pfn_t_devmap(pfn
));
1009 if (addr
< vma
->vm_start
|| addr
>= vma
->vm_end
)
1010 return VM_FAULT_SIGBUS
;
1011 if (track_pfn_insert(vma
, &pgprot
, pfn
))
1012 return VM_FAULT_SIGBUS
;
1013 insert_pfn_pmd(vma
, addr
, pmd
, pfn
, pgprot
, write
);
1014 return VM_FAULT_NOPAGE
;
1016 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd
);
1018 static void touch_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
1024 * We should set the dirty bit only for FOLL_WRITE but for now
1025 * the dirty bit in the pmd is meaningless. And if the dirty
1026 * bit will become meaningful and we'll only set it with
1027 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
1028 * set the young bit, instead of the current set_pmd_at.
1030 _pmd
= pmd_mkyoung(pmd_mkdirty(*pmd
));
1031 if (pmdp_set_access_flags(vma
, addr
& HPAGE_PMD_MASK
,
1033 update_mmu_cache_pmd(vma
, addr
, pmd
);
1036 struct page
*follow_devmap_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
1037 pmd_t
*pmd
, int flags
)
1039 unsigned long pfn
= pmd_pfn(*pmd
);
1040 struct mm_struct
*mm
= vma
->vm_mm
;
1041 struct dev_pagemap
*pgmap
;
1044 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1046 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1049 if (pmd_present(*pmd
) && pmd_devmap(*pmd
))
1054 if (flags
& FOLL_TOUCH
)
1055 touch_pmd(vma
, addr
, pmd
);
1058 * device mapped pages can only be returned if the
1059 * caller will manage the page reference count.
1061 if (!(flags
& FOLL_GET
))
1062 return ERR_PTR(-EEXIST
);
1064 pfn
+= (addr
& ~PMD_MASK
) >> PAGE_SHIFT
;
1065 pgmap
= get_dev_pagemap(pfn
, NULL
);
1067 return ERR_PTR(-EFAULT
);
1068 page
= pfn_to_page(pfn
);
1070 put_dev_pagemap(pgmap
);
1075 int copy_huge_pmd(struct mm_struct
*dst_mm
, struct mm_struct
*src_mm
,
1076 pmd_t
*dst_pmd
, pmd_t
*src_pmd
, unsigned long addr
,
1077 struct vm_area_struct
*vma
)
1079 spinlock_t
*dst_ptl
, *src_ptl
;
1080 struct page
*src_page
;
1082 pgtable_t pgtable
= NULL
;
1085 if (!vma_is_dax(vma
)) {
1087 pgtable
= pte_alloc_one(dst_mm
, addr
);
1088 if (unlikely(!pgtable
))
1092 dst_ptl
= pmd_lock(dst_mm
, dst_pmd
);
1093 src_ptl
= pmd_lockptr(src_mm
, src_pmd
);
1094 spin_lock_nested(src_ptl
, SINGLE_DEPTH_NESTING
);
1098 if (unlikely(!pmd_trans_huge(pmd
) && !pmd_devmap(pmd
))) {
1099 pte_free(dst_mm
, pgtable
);
1103 * When page table lock is held, the huge zero pmd should not be
1104 * under splitting since we don't split the page itself, only pmd to
1107 if (is_huge_zero_pmd(pmd
)) {
1108 struct page
*zero_page
;
1110 * get_huge_zero_page() will never allocate a new page here,
1111 * since we already have a zero page to copy. It just takes a
1114 zero_page
= get_huge_zero_page();
1115 set_huge_zero_page(pgtable
, dst_mm
, vma
, addr
, dst_pmd
,
1121 if (!vma_is_dax(vma
)) {
1122 /* thp accounting separate from pmd_devmap accounting */
1123 src_page
= pmd_page(pmd
);
1124 VM_BUG_ON_PAGE(!PageHead(src_page
), src_page
);
1126 page_dup_rmap(src_page
, true);
1127 add_mm_counter(dst_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1128 atomic_long_inc(&dst_mm
->nr_ptes
);
1129 pgtable_trans_huge_deposit(dst_mm
, dst_pmd
, pgtable
);
1132 pmdp_set_wrprotect(src_mm
, addr
, src_pmd
);
1133 pmd
= pmd_mkold(pmd_wrprotect(pmd
));
1134 set_pmd_at(dst_mm
, addr
, dst_pmd
, pmd
);
1138 spin_unlock(src_ptl
);
1139 spin_unlock(dst_ptl
);
1144 void huge_pmd_set_accessed(struct mm_struct
*mm
,
1145 struct vm_area_struct
*vma
,
1146 unsigned long address
,
1147 pmd_t
*pmd
, pmd_t orig_pmd
,
1152 unsigned long haddr
;
1154 ptl
= pmd_lock(mm
, pmd
);
1155 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1158 entry
= pmd_mkyoung(orig_pmd
);
1159 haddr
= address
& HPAGE_PMD_MASK
;
1160 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, dirty
))
1161 update_mmu_cache_pmd(vma
, address
, pmd
);
1167 static int do_huge_pmd_wp_page_fallback(struct mm_struct
*mm
,
1168 struct vm_area_struct
*vma
,
1169 unsigned long address
,
1170 pmd_t
*pmd
, pmd_t orig_pmd
,
1172 unsigned long haddr
)
1174 struct mem_cgroup
*memcg
;
1179 struct page
**pages
;
1180 unsigned long mmun_start
; /* For mmu_notifiers */
1181 unsigned long mmun_end
; /* For mmu_notifiers */
1183 pages
= kmalloc(sizeof(struct page
*) * HPAGE_PMD_NR
,
1185 if (unlikely(!pages
)) {
1186 ret
|= VM_FAULT_OOM
;
1190 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1191 pages
[i
] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE
|
1193 vma
, address
, page_to_nid(page
));
1194 if (unlikely(!pages
[i
] ||
1195 mem_cgroup_try_charge(pages
[i
], mm
, GFP_KERNEL
,
1200 memcg
= (void *)page_private(pages
[i
]);
1201 set_page_private(pages
[i
], 0);
1202 mem_cgroup_cancel_charge(pages
[i
], memcg
,
1207 ret
|= VM_FAULT_OOM
;
1210 set_page_private(pages
[i
], (unsigned long)memcg
);
1213 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1214 copy_user_highpage(pages
[i
], page
+ i
,
1215 haddr
+ PAGE_SIZE
* i
, vma
);
1216 __SetPageUptodate(pages
[i
]);
1221 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1222 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1224 ptl
= pmd_lock(mm
, pmd
);
1225 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1226 goto out_free_pages
;
1227 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1229 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1230 /* leave pmd empty until pte is filled */
1232 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
1233 pmd_populate(mm
, &_pmd
, pgtable
);
1235 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
1237 entry
= mk_pte(pages
[i
], vma
->vm_page_prot
);
1238 entry
= maybe_mkwrite(pte_mkdirty(entry
), vma
);
1239 memcg
= (void *)page_private(pages
[i
]);
1240 set_page_private(pages
[i
], 0);
1241 page_add_new_anon_rmap(pages
[i
], vma
, haddr
, false);
1242 mem_cgroup_commit_charge(pages
[i
], memcg
, false, false);
1243 lru_cache_add_active_or_unevictable(pages
[i
], vma
);
1244 pte
= pte_offset_map(&_pmd
, haddr
);
1245 VM_BUG_ON(!pte_none(*pte
));
1246 set_pte_at(mm
, haddr
, pte
, entry
);
1251 smp_wmb(); /* make pte visible before pmd */
1252 pmd_populate(mm
, pmd
, pgtable
);
1253 page_remove_rmap(page
, true);
1256 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1258 ret
|= VM_FAULT_WRITE
;
1266 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1267 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1268 memcg
= (void *)page_private(pages
[i
]);
1269 set_page_private(pages
[i
], 0);
1270 mem_cgroup_cancel_charge(pages
[i
], memcg
, false);
1277 int do_huge_pmd_wp_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1278 unsigned long address
, pmd_t
*pmd
, pmd_t orig_pmd
)
1282 struct page
*page
= NULL
, *new_page
;
1283 struct mem_cgroup
*memcg
;
1284 unsigned long haddr
;
1285 unsigned long mmun_start
; /* For mmu_notifiers */
1286 unsigned long mmun_end
; /* For mmu_notifiers */
1287 gfp_t huge_gfp
; /* for allocation and charge */
1289 ptl
= pmd_lockptr(mm
, pmd
);
1290 VM_BUG_ON_VMA(!vma
->anon_vma
, vma
);
1291 haddr
= address
& HPAGE_PMD_MASK
;
1292 if (is_huge_zero_pmd(orig_pmd
))
1295 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1298 page
= pmd_page(orig_pmd
);
1299 VM_BUG_ON_PAGE(!PageCompound(page
) || !PageHead(page
), page
);
1301 * We can only reuse the page if nobody else maps the huge page or it's
1304 if (page_trans_huge_mapcount(page
, NULL
) == 1) {
1306 entry
= pmd_mkyoung(orig_pmd
);
1307 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1308 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, 1))
1309 update_mmu_cache_pmd(vma
, address
, pmd
);
1310 ret
|= VM_FAULT_WRITE
;
1316 if (transparent_hugepage_enabled(vma
) &&
1317 !transparent_hugepage_debug_cow()) {
1318 huge_gfp
= alloc_hugepage_direct_gfpmask(vma
);
1319 new_page
= alloc_hugepage_vma(huge_gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
1323 if (likely(new_page
)) {
1324 prep_transhuge_page(new_page
);
1327 split_huge_pmd(vma
, pmd
, address
);
1328 ret
|= VM_FAULT_FALLBACK
;
1330 ret
= do_huge_pmd_wp_page_fallback(mm
, vma
, address
,
1331 pmd
, orig_pmd
, page
, haddr
);
1332 if (ret
& VM_FAULT_OOM
) {
1333 split_huge_pmd(vma
, pmd
, address
);
1334 ret
|= VM_FAULT_FALLBACK
;
1338 count_vm_event(THP_FAULT_FALLBACK
);
1342 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, huge_gfp
, &memcg
,
1346 split_huge_pmd(vma
, pmd
, address
);
1349 split_huge_pmd(vma
, pmd
, address
);
1350 ret
|= VM_FAULT_FALLBACK
;
1351 count_vm_event(THP_FAULT_FALLBACK
);
1355 count_vm_event(THP_FAULT_ALLOC
);
1358 clear_huge_page(new_page
, haddr
, HPAGE_PMD_NR
);
1360 copy_user_huge_page(new_page
, page
, haddr
, vma
, HPAGE_PMD_NR
);
1361 __SetPageUptodate(new_page
);
1364 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1365 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1370 if (unlikely(!pmd_same(*pmd
, orig_pmd
))) {
1372 mem_cgroup_cancel_charge(new_page
, memcg
, true);
1377 entry
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1378 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1379 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1380 page_add_new_anon_rmap(new_page
, vma
, haddr
, true);
1381 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
1382 lru_cache_add_active_or_unevictable(new_page
, vma
);
1383 set_pmd_at(mm
, haddr
, pmd
, entry
);
1384 update_mmu_cache_pmd(vma
, address
, pmd
);
1386 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1387 put_huge_zero_page();
1389 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1390 page_remove_rmap(page
, true);
1393 ret
|= VM_FAULT_WRITE
;
1397 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1405 struct page
*follow_trans_huge_pmd(struct vm_area_struct
*vma
,
1410 struct mm_struct
*mm
= vma
->vm_mm
;
1411 struct page
*page
= NULL
;
1413 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1415 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1418 /* Avoid dumping huge zero page */
1419 if ((flags
& FOLL_DUMP
) && is_huge_zero_pmd(*pmd
))
1420 return ERR_PTR(-EFAULT
);
1422 /* Full NUMA hinting faults to serialise migration in fault paths */
1423 if ((flags
& FOLL_NUMA
) && pmd_protnone(*pmd
))
1426 page
= pmd_page(*pmd
);
1427 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1428 if (flags
& FOLL_TOUCH
)
1429 touch_pmd(vma
, addr
, pmd
);
1430 if ((flags
& FOLL_MLOCK
) && (vma
->vm_flags
& VM_LOCKED
)) {
1432 * We don't mlock() pte-mapped THPs. This way we can avoid
1433 * leaking mlocked pages into non-VM_LOCKED VMAs.
1435 * In most cases the pmd is the only mapping of the page as we
1436 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1437 * writable private mappings in populate_vma_page_range().
1439 * The only scenario when we have the page shared here is if we
1440 * mlocking read-only mapping shared over fork(). We skip
1441 * mlocking such pages.
1443 if (compound_mapcount(page
) == 1 && !PageDoubleMap(page
) &&
1444 page
->mapping
&& trylock_page(page
)) {
1447 mlock_vma_page(page
);
1451 page
+= (addr
& ~HPAGE_PMD_MASK
) >> PAGE_SHIFT
;
1452 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
1453 if (flags
& FOLL_GET
)
1460 /* NUMA hinting page fault entry point for trans huge pmds */
1461 int do_huge_pmd_numa_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1462 unsigned long addr
, pmd_t pmd
, pmd_t
*pmdp
)
1465 struct anon_vma
*anon_vma
= NULL
;
1467 unsigned long haddr
= addr
& HPAGE_PMD_MASK
;
1468 int page_nid
= -1, this_nid
= numa_node_id();
1469 int target_nid
, last_cpupid
= -1;
1471 bool migrated
= false;
1475 /* A PROT_NONE fault should not end up here */
1476 BUG_ON(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)));
1478 ptl
= pmd_lock(mm
, pmdp
);
1479 if (unlikely(!pmd_same(pmd
, *pmdp
)))
1483 * If there are potential migrations, wait for completion and retry
1484 * without disrupting NUMA hinting information. Do not relock and
1485 * check_same as the page may no longer be mapped.
1487 if (unlikely(pmd_trans_migrating(*pmdp
))) {
1488 page
= pmd_page(*pmdp
);
1490 wait_on_page_locked(page
);
1494 page
= pmd_page(pmd
);
1495 BUG_ON(is_huge_zero_page(page
));
1496 page_nid
= page_to_nid(page
);
1497 last_cpupid
= page_cpupid_last(page
);
1498 count_vm_numa_event(NUMA_HINT_FAULTS
);
1499 if (page_nid
== this_nid
) {
1500 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL
);
1501 flags
|= TNF_FAULT_LOCAL
;
1504 /* See similar comment in do_numa_page for explanation */
1505 if (!(vma
->vm_flags
& VM_WRITE
))
1506 flags
|= TNF_NO_GROUP
;
1509 * Acquire the page lock to serialise THP migrations but avoid dropping
1510 * page_table_lock if at all possible
1512 page_locked
= trylock_page(page
);
1513 target_nid
= mpol_misplaced(page
, vma
, haddr
);
1514 if (target_nid
== -1) {
1515 /* If the page was locked, there are no parallel migrations */
1520 /* Migration could have started since the pmd_trans_migrating check */
1523 wait_on_page_locked(page
);
1529 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1530 * to serialises splits
1534 anon_vma
= page_lock_anon_vma_read(page
);
1536 /* Confirm the PMD did not change while page_table_lock was released */
1538 if (unlikely(!pmd_same(pmd
, *pmdp
))) {
1545 /* Bail if we fail to protect against THP splits for any reason */
1546 if (unlikely(!anon_vma
)) {
1553 * Migrate the THP to the requested node, returns with page unlocked
1554 * and access rights restored.
1557 migrated
= migrate_misplaced_transhuge_page(mm
, vma
,
1558 pmdp
, pmd
, addr
, page
, target_nid
);
1560 flags
|= TNF_MIGRATED
;
1561 page_nid
= target_nid
;
1563 flags
|= TNF_MIGRATE_FAIL
;
1567 BUG_ON(!PageLocked(page
));
1568 was_writable
= pmd_write(pmd
);
1569 pmd
= pmd_modify(pmd
, vma
->vm_page_prot
);
1570 pmd
= pmd_mkyoung(pmd
);
1572 pmd
= pmd_mkwrite(pmd
);
1573 set_pmd_at(mm
, haddr
, pmdp
, pmd
);
1574 update_mmu_cache_pmd(vma
, addr
, pmdp
);
1581 page_unlock_anon_vma_read(anon_vma
);
1584 task_numa_fault(last_cpupid
, page_nid
, HPAGE_PMD_NR
, flags
);
1589 int madvise_free_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1590 pmd_t
*pmd
, unsigned long addr
, unsigned long next
)
1596 struct mm_struct
*mm
= tlb
->mm
;
1599 ptl
= pmd_trans_huge_lock(pmd
, vma
);
1604 if (is_huge_zero_pmd(orig_pmd
)) {
1609 page
= pmd_page(orig_pmd
);
1611 * If other processes are mapping this page, we couldn't discard
1612 * the page unless they all do MADV_FREE so let's skip the page.
1614 if (page_mapcount(page
) != 1)
1617 if (!trylock_page(page
))
1621 * If user want to discard part-pages of THP, split it so MADV_FREE
1622 * will deactivate only them.
1624 if (next
- addr
!= HPAGE_PMD_SIZE
) {
1627 if (split_huge_page(page
)) {
1638 if (PageDirty(page
))
1639 ClearPageDirty(page
);
1642 if (PageActive(page
))
1643 deactivate_page(page
);
1645 if (pmd_young(orig_pmd
) || pmd_dirty(orig_pmd
)) {
1646 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1648 orig_pmd
= pmd_mkold(orig_pmd
);
1649 orig_pmd
= pmd_mkclean(orig_pmd
);
1651 set_pmd_at(mm
, addr
, pmd
, orig_pmd
);
1652 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1661 int zap_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1662 pmd_t
*pmd
, unsigned long addr
)
1667 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1671 * For architectures like ppc64 we look at deposited pgtable
1672 * when calling pmdp_huge_get_and_clear. So do the
1673 * pgtable_trans_huge_withdraw after finishing pmdp related
1676 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1678 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1679 if (vma_is_dax(vma
)) {
1681 if (is_huge_zero_pmd(orig_pmd
))
1682 tlb_remove_page(tlb
, pmd_page(orig_pmd
));
1683 } else if (is_huge_zero_pmd(orig_pmd
)) {
1684 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1685 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1687 tlb_remove_page(tlb
, pmd_page(orig_pmd
));
1689 struct page
*page
= pmd_page(orig_pmd
);
1690 page_remove_rmap(page
, true);
1691 VM_BUG_ON_PAGE(page_mapcount(page
) < 0, page
);
1692 add_mm_counter(tlb
->mm
, MM_ANONPAGES
, -HPAGE_PMD_NR
);
1693 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1694 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1695 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1697 tlb_remove_page(tlb
, page
);
1702 bool move_huge_pmd(struct vm_area_struct
*vma
, unsigned long old_addr
,
1703 unsigned long new_addr
, unsigned long old_end
,
1704 pmd_t
*old_pmd
, pmd_t
*new_pmd
)
1706 spinlock_t
*old_ptl
, *new_ptl
;
1708 struct mm_struct
*mm
= vma
->vm_mm
;
1710 if ((old_addr
& ~HPAGE_PMD_MASK
) ||
1711 (new_addr
& ~HPAGE_PMD_MASK
) ||
1712 old_end
- old_addr
< HPAGE_PMD_SIZE
)
1716 * The destination pmd shouldn't be established, free_pgtables()
1717 * should have release it.
1719 if (WARN_ON(!pmd_none(*new_pmd
))) {
1720 VM_BUG_ON(pmd_trans_huge(*new_pmd
));
1725 * We don't have to worry about the ordering of src and dst
1726 * ptlocks because exclusive mmap_sem prevents deadlock.
1728 old_ptl
= __pmd_trans_huge_lock(old_pmd
, vma
);
1730 new_ptl
= pmd_lockptr(mm
, new_pmd
);
1731 if (new_ptl
!= old_ptl
)
1732 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
1733 pmd
= pmdp_huge_get_and_clear(mm
, old_addr
, old_pmd
);
1734 VM_BUG_ON(!pmd_none(*new_pmd
));
1736 if (pmd_move_must_withdraw(new_ptl
, old_ptl
) &&
1737 vma_is_anonymous(vma
)) {
1739 pgtable
= pgtable_trans_huge_withdraw(mm
, old_pmd
);
1740 pgtable_trans_huge_deposit(mm
, new_pmd
, pgtable
);
1742 set_pmd_at(mm
, new_addr
, new_pmd
, pmd_mksoft_dirty(pmd
));
1743 if (new_ptl
!= old_ptl
)
1744 spin_unlock(new_ptl
);
1745 spin_unlock(old_ptl
);
1753 * - 0 if PMD could not be locked
1754 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1755 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1757 int change_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1758 unsigned long addr
, pgprot_t newprot
, int prot_numa
)
1760 struct mm_struct
*mm
= vma
->vm_mm
;
1764 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1767 bool preserve_write
= prot_numa
&& pmd_write(*pmd
);
1771 * Avoid trapping faults against the zero page. The read-only
1772 * data is likely to be read-cached on the local CPU and
1773 * local/remote hits to the zero page are not interesting.
1775 if (prot_numa
&& is_huge_zero_pmd(*pmd
)) {
1780 if (!prot_numa
|| !pmd_protnone(*pmd
)) {
1781 entry
= pmdp_huge_get_and_clear_notify(mm
, addr
, pmd
);
1782 entry
= pmd_modify(entry
, newprot
);
1784 entry
= pmd_mkwrite(entry
);
1786 set_pmd_at(mm
, addr
, pmd
, entry
);
1787 BUG_ON(!preserve_write
&& pmd_write(entry
));
1796 * Returns true if a given pmd maps a thp, false otherwise.
1798 * Note that if it returns true, this routine returns without unlocking page
1799 * table lock. So callers must unlock it.
1801 spinlock_t
*__pmd_trans_huge_lock(pmd_t
*pmd
, struct vm_area_struct
*vma
)
1804 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1805 if (likely(pmd_trans_huge(*pmd
) || pmd_devmap(*pmd
)))
1811 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1813 int hugepage_madvise(struct vm_area_struct
*vma
,
1814 unsigned long *vm_flags
, int advice
)
1820 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1821 * can't handle this properly after s390_enable_sie, so we simply
1822 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1824 if (mm_has_pgste(vma
->vm_mm
))
1828 * Be somewhat over-protective like KSM for now!
1830 if (*vm_flags
& VM_NO_THP
)
1832 *vm_flags
&= ~VM_NOHUGEPAGE
;
1833 *vm_flags
|= VM_HUGEPAGE
;
1835 * If the vma become good for khugepaged to scan,
1836 * register it here without waiting a page fault that
1837 * may not happen any time soon.
1839 if (unlikely(khugepaged_enter_vma_merge(vma
, *vm_flags
)))
1842 case MADV_NOHUGEPAGE
:
1844 * Be somewhat over-protective like KSM for now!
1846 if (*vm_flags
& VM_NO_THP
)
1848 *vm_flags
&= ~VM_HUGEPAGE
;
1849 *vm_flags
|= VM_NOHUGEPAGE
;
1851 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1852 * this vma even if we leave the mm registered in khugepaged if
1853 * it got registered before VM_NOHUGEPAGE was set.
1861 static int __init
khugepaged_slab_init(void)
1863 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
1864 sizeof(struct mm_slot
),
1865 __alignof__(struct mm_slot
), 0, NULL
);
1872 static void __init
khugepaged_slab_exit(void)
1874 kmem_cache_destroy(mm_slot_cache
);
1877 static inline struct mm_slot
*alloc_mm_slot(void)
1879 if (!mm_slot_cache
) /* initialization failed */
1881 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
1884 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
1886 kmem_cache_free(mm_slot_cache
, mm_slot
);
1889 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
1891 struct mm_slot
*mm_slot
;
1893 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
1894 if (mm
== mm_slot
->mm
)
1900 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
1901 struct mm_slot
*mm_slot
)
1904 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
1907 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
1909 return atomic_read(&mm
->mm_users
) == 0;
1912 int __khugepaged_enter(struct mm_struct
*mm
)
1914 struct mm_slot
*mm_slot
;
1917 mm_slot
= alloc_mm_slot();
1921 /* __khugepaged_exit() must not run from under us */
1922 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
1923 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
1924 free_mm_slot(mm_slot
);
1928 spin_lock(&khugepaged_mm_lock
);
1929 insert_to_mm_slots_hash(mm
, mm_slot
);
1931 * Insert just behind the scanning cursor, to let the area settle
1934 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
1935 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
1936 spin_unlock(&khugepaged_mm_lock
);
1938 atomic_inc(&mm
->mm_count
);
1940 wake_up_interruptible(&khugepaged_wait
);
1945 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
1946 unsigned long vm_flags
)
1948 unsigned long hstart
, hend
;
1951 * Not yet faulted in so we will register later in the
1952 * page fault if needed.
1955 if (vma
->vm_ops
|| (vm_flags
& VM_NO_THP
))
1956 /* khugepaged not yet working on file or special mappings */
1958 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1959 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1961 return khugepaged_enter(vma
, vm_flags
);
1965 void __khugepaged_exit(struct mm_struct
*mm
)
1967 struct mm_slot
*mm_slot
;
1970 spin_lock(&khugepaged_mm_lock
);
1971 mm_slot
= get_mm_slot(mm
);
1972 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
1973 hash_del(&mm_slot
->hash
);
1974 list_del(&mm_slot
->mm_node
);
1977 spin_unlock(&khugepaged_mm_lock
);
1980 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
1981 free_mm_slot(mm_slot
);
1983 } else if (mm_slot
) {
1985 * This is required to serialize against
1986 * khugepaged_test_exit() (which is guaranteed to run
1987 * under mmap sem read mode). Stop here (after we
1988 * return all pagetables will be destroyed) until
1989 * khugepaged has finished working on the pagetables
1990 * under the mmap_sem.
1992 down_write(&mm
->mmap_sem
);
1993 up_write(&mm
->mmap_sem
);
1997 static void release_pte_page(struct page
*page
)
1999 /* 0 stands for page_is_file_cache(page) == false */
2000 dec_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
2002 putback_lru_page(page
);
2005 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
)
2007 while (--_pte
>= pte
) {
2008 pte_t pteval
= *_pte
;
2009 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)))
2010 release_pte_page(pte_page(pteval
));
2014 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
2015 unsigned long address
,
2018 struct page
*page
= NULL
;
2020 int none_or_zero
= 0, result
= 0;
2021 bool referenced
= false, writable
= false;
2023 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2024 _pte
++, address
+= PAGE_SIZE
) {
2025 pte_t pteval
= *_pte
;
2026 if (pte_none(pteval
) || (pte_present(pteval
) &&
2027 is_zero_pfn(pte_pfn(pteval
)))) {
2028 if (!userfaultfd_armed(vma
) &&
2029 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2032 result
= SCAN_EXCEED_NONE_PTE
;
2036 if (!pte_present(pteval
)) {
2037 result
= SCAN_PTE_NON_PRESENT
;
2040 page
= vm_normal_page(vma
, address
, pteval
);
2041 if (unlikely(!page
)) {
2042 result
= SCAN_PAGE_NULL
;
2046 VM_BUG_ON_PAGE(PageCompound(page
), page
);
2047 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
2048 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
2051 * We can do it before isolate_lru_page because the
2052 * page can't be freed from under us. NOTE: PG_lock
2053 * is needed to serialize against split_huge_page
2054 * when invoked from the VM.
2056 if (!trylock_page(page
)) {
2057 result
= SCAN_PAGE_LOCK
;
2062 * cannot use mapcount: can't collapse if there's a gup pin.
2063 * The page must only be referenced by the scanned process
2064 * and page swap cache.
2066 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2068 result
= SCAN_PAGE_COUNT
;
2071 if (pte_write(pteval
)) {
2074 if (PageSwapCache(page
) &&
2075 !reuse_swap_page(page
, NULL
)) {
2077 result
= SCAN_SWAP_CACHE_PAGE
;
2081 * Page is not in the swap cache. It can be collapsed
2087 * Isolate the page to avoid collapsing an hugepage
2088 * currently in use by the VM.
2090 if (isolate_lru_page(page
)) {
2092 result
= SCAN_DEL_PAGE_LRU
;
2095 /* 0 stands for page_is_file_cache(page) == false */
2096 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
2097 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
2098 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2100 /* If there is no mapped pte young don't collapse the page */
2101 if (pte_young(pteval
) ||
2102 page_is_young(page
) || PageReferenced(page
) ||
2103 mmu_notifier_test_young(vma
->vm_mm
, address
))
2106 if (likely(writable
)) {
2107 if (likely(referenced
)) {
2108 result
= SCAN_SUCCEED
;
2109 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
2110 referenced
, writable
, result
);
2114 result
= SCAN_PAGE_RO
;
2118 release_pte_pages(pte
, _pte
);
2119 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
2120 referenced
, writable
, result
);
2124 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
2125 struct vm_area_struct
*vma
,
2126 unsigned long address
,
2130 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
; _pte
++) {
2131 pte_t pteval
= *_pte
;
2132 struct page
*src_page
;
2134 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2135 clear_user_highpage(page
, address
);
2136 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
2137 if (is_zero_pfn(pte_pfn(pteval
))) {
2139 * ptl mostly unnecessary.
2143 * paravirt calls inside pte_clear here are
2146 pte_clear(vma
->vm_mm
, address
, _pte
);
2150 src_page
= pte_page(pteval
);
2151 copy_user_highpage(page
, src_page
, address
, vma
);
2152 VM_BUG_ON_PAGE(page_mapcount(src_page
) != 1, src_page
);
2153 release_pte_page(src_page
);
2155 * ptl mostly unnecessary, but preempt has to
2156 * be disabled to update the per-cpu stats
2157 * inside page_remove_rmap().
2161 * paravirt calls inside pte_clear here are
2164 pte_clear(vma
->vm_mm
, address
, _pte
);
2165 page_remove_rmap(src_page
, false);
2167 free_page_and_swap_cache(src_page
);
2170 address
+= PAGE_SIZE
;
2175 static void khugepaged_alloc_sleep(void)
2179 add_wait_queue(&khugepaged_wait
, &wait
);
2180 freezable_schedule_timeout_interruptible(
2181 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
2182 remove_wait_queue(&khugepaged_wait
, &wait
);
2185 static int khugepaged_node_load
[MAX_NUMNODES
];
2187 static bool khugepaged_scan_abort(int nid
)
2192 * If zone_reclaim_mode is disabled, then no extra effort is made to
2193 * allocate memory locally.
2195 if (!zone_reclaim_mode
)
2198 /* If there is a count for this node already, it must be acceptable */
2199 if (khugepaged_node_load
[nid
])
2202 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
2203 if (!khugepaged_node_load
[i
])
2205 if (node_distance(nid
, i
) > RECLAIM_DISTANCE
)
2212 static int khugepaged_find_target_node(void)
2214 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
2215 int nid
, target_node
= 0, max_value
= 0;
2217 /* find first node with max normal pages hit */
2218 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
2219 if (khugepaged_node_load
[nid
] > max_value
) {
2220 max_value
= khugepaged_node_load
[nid
];
2224 /* do some balance if several nodes have the same hit record */
2225 if (target_node
<= last_khugepaged_target_node
)
2226 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
2228 if (max_value
== khugepaged_node_load
[nid
]) {
2233 last_khugepaged_target_node
= target_node
;
2237 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2239 if (IS_ERR(*hpage
)) {
2245 khugepaged_alloc_sleep();
2246 } else if (*hpage
) {
2254 static struct page
*
2255 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2256 unsigned long address
, int node
)
2258 VM_BUG_ON_PAGE(*hpage
, *hpage
);
2261 * Before allocating the hugepage, release the mmap_sem read lock.
2262 * The allocation can take potentially a long time if it involves
2263 * sync compaction, and we do not need to hold the mmap_sem during
2264 * that. We will recheck the vma after taking it again in write mode.
2266 up_read(&mm
->mmap_sem
);
2268 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
2269 if (unlikely(!*hpage
)) {
2270 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2271 *hpage
= ERR_PTR(-ENOMEM
);
2275 prep_transhuge_page(*hpage
);
2276 count_vm_event(THP_COLLAPSE_ALLOC
);
2280 static int khugepaged_find_target_node(void)
2285 static inline struct page
*alloc_khugepaged_hugepage(void)
2289 page
= alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2292 prep_transhuge_page(page
);
2296 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
2301 hpage
= alloc_khugepaged_hugepage();
2303 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2308 khugepaged_alloc_sleep();
2310 count_vm_event(THP_COLLAPSE_ALLOC
);
2311 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
2316 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2319 *hpage
= khugepaged_alloc_hugepage(wait
);
2321 if (unlikely(!*hpage
))
2327 static struct page
*
2328 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2329 unsigned long address
, int node
)
2331 up_read(&mm
->mmap_sem
);
2338 static bool hugepage_vma_check(struct vm_area_struct
*vma
)
2340 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
2341 (vma
->vm_flags
& VM_NOHUGEPAGE
))
2343 if (!vma
->anon_vma
|| vma
->vm_ops
)
2345 if (is_vma_temporary_stack(vma
))
2347 return !(vma
->vm_flags
& VM_NO_THP
);
2350 static void collapse_huge_page(struct mm_struct
*mm
,
2351 unsigned long address
,
2352 struct page
**hpage
,
2353 struct vm_area_struct
*vma
,
2359 struct page
*new_page
;
2360 spinlock_t
*pmd_ptl
, *pte_ptl
;
2361 int isolated
= 0, result
= 0;
2362 unsigned long hstart
, hend
;
2363 struct mem_cgroup
*memcg
;
2364 unsigned long mmun_start
; /* For mmu_notifiers */
2365 unsigned long mmun_end
; /* For mmu_notifiers */
2368 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2370 /* Only allocate from the target node */
2371 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE
| __GFP_THISNODE
;
2373 /* release the mmap_sem read lock. */
2374 new_page
= khugepaged_alloc_page(hpage
, gfp
, mm
, address
, node
);
2376 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
2380 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, gfp
, &memcg
, true))) {
2381 result
= SCAN_CGROUP_CHARGE_FAIL
;
2386 * Prevent all access to pagetables with the exception of
2387 * gup_fast later hanlded by the ptep_clear_flush and the VM
2388 * handled by the anon_vma lock + PG_lock.
2390 down_write(&mm
->mmap_sem
);
2391 if (unlikely(khugepaged_test_exit(mm
))) {
2392 result
= SCAN_ANY_PROCESS
;
2396 vma
= find_vma(mm
, address
);
2398 result
= SCAN_VMA_NULL
;
2401 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2402 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2403 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
) {
2404 result
= SCAN_ADDRESS_RANGE
;
2407 if (!hugepage_vma_check(vma
)) {
2408 result
= SCAN_VMA_CHECK
;
2411 pmd
= mm_find_pmd(mm
, address
);
2413 result
= SCAN_PMD_NULL
;
2417 anon_vma_lock_write(vma
->anon_vma
);
2419 pte
= pte_offset_map(pmd
, address
);
2420 pte_ptl
= pte_lockptr(mm
, pmd
);
2422 mmun_start
= address
;
2423 mmun_end
= address
+ HPAGE_PMD_SIZE
;
2424 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
2425 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
2427 * After this gup_fast can't run anymore. This also removes
2428 * any huge TLB entry from the CPU so we won't allow
2429 * huge and small TLB entries for the same virtual address
2430 * to avoid the risk of CPU bugs in that area.
2432 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
2433 spin_unlock(pmd_ptl
);
2434 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
2437 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
);
2438 spin_unlock(pte_ptl
);
2440 if (unlikely(!isolated
)) {
2443 BUG_ON(!pmd_none(*pmd
));
2445 * We can only use set_pmd_at when establishing
2446 * hugepmds and never for establishing regular pmds that
2447 * points to regular pagetables. Use pmd_populate for that
2449 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
2450 spin_unlock(pmd_ptl
);
2451 anon_vma_unlock_write(vma
->anon_vma
);
2457 * All pages are isolated and locked so anon_vma rmap
2458 * can't run anymore.
2460 anon_vma_unlock_write(vma
->anon_vma
);
2462 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
);
2464 __SetPageUptodate(new_page
);
2465 pgtable
= pmd_pgtable(_pmd
);
2467 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
2468 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
2471 * spin_lock() below is not the equivalent of smp_wmb(), so
2472 * this is needed to avoid the copy_huge_page writes to become
2473 * visible after the set_pmd_at() write.
2478 BUG_ON(!pmd_none(*pmd
));
2479 page_add_new_anon_rmap(new_page
, vma
, address
, true);
2480 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
2481 lru_cache_add_active_or_unevictable(new_page
, vma
);
2482 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
2483 set_pmd_at(mm
, address
, pmd
, _pmd
);
2484 update_mmu_cache_pmd(vma
, address
, pmd
);
2485 spin_unlock(pmd_ptl
);
2489 khugepaged_pages_collapsed
++;
2490 result
= SCAN_SUCCEED
;
2492 up_write(&mm
->mmap_sem
);
2493 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2497 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2500 mem_cgroup_cancel_charge(new_page
, memcg
, true);
2504 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
2505 struct vm_area_struct
*vma
,
2506 unsigned long address
,
2507 struct page
**hpage
)
2511 int ret
= 0, none_or_zero
= 0, result
= 0;
2512 struct page
*page
= NULL
;
2513 unsigned long _address
;
2515 int node
= NUMA_NO_NODE
;
2516 bool writable
= false, referenced
= false;
2518 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2520 pmd
= mm_find_pmd(mm
, address
);
2522 result
= SCAN_PMD_NULL
;
2526 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
2527 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
2528 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2529 _pte
++, _address
+= PAGE_SIZE
) {
2530 pte_t pteval
= *_pte
;
2531 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2532 if (!userfaultfd_armed(vma
) &&
2533 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2536 result
= SCAN_EXCEED_NONE_PTE
;
2540 if (!pte_present(pteval
)) {
2541 result
= SCAN_PTE_NON_PRESENT
;
2544 if (pte_write(pteval
))
2547 page
= vm_normal_page(vma
, _address
, pteval
);
2548 if (unlikely(!page
)) {
2549 result
= SCAN_PAGE_NULL
;
2553 /* TODO: teach khugepaged to collapse THP mapped with pte */
2554 if (PageCompound(page
)) {
2555 result
= SCAN_PAGE_COMPOUND
;
2560 * Record which node the original page is from and save this
2561 * information to khugepaged_node_load[].
2562 * Khupaged will allocate hugepage from the node has the max
2565 node
= page_to_nid(page
);
2566 if (khugepaged_scan_abort(node
)) {
2567 result
= SCAN_SCAN_ABORT
;
2570 khugepaged_node_load
[node
]++;
2571 if (!PageLRU(page
)) {
2572 result
= SCAN_PAGE_LRU
;
2575 if (PageLocked(page
)) {
2576 result
= SCAN_PAGE_LOCK
;
2579 if (!PageAnon(page
)) {
2580 result
= SCAN_PAGE_ANON
;
2585 * cannot use mapcount: can't collapse if there's a gup pin.
2586 * The page must only be referenced by the scanned process
2587 * and page swap cache.
2589 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2590 result
= SCAN_PAGE_COUNT
;
2593 if (pte_young(pteval
) ||
2594 page_is_young(page
) || PageReferenced(page
) ||
2595 mmu_notifier_test_young(vma
->vm_mm
, address
))
2600 result
= SCAN_SUCCEED
;
2603 result
= SCAN_NO_REFERENCED_PAGE
;
2606 result
= SCAN_PAGE_RO
;
2609 pte_unmap_unlock(pte
, ptl
);
2611 node
= khugepaged_find_target_node();
2612 /* collapse_huge_page will return with the mmap_sem released */
2613 collapse_huge_page(mm
, address
, hpage
, vma
, node
);
2616 trace_mm_khugepaged_scan_pmd(mm
, page
, writable
, referenced
,
2617 none_or_zero
, result
);
2621 static void collect_mm_slot(struct mm_slot
*mm_slot
)
2623 struct mm_struct
*mm
= mm_slot
->mm
;
2625 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2627 if (khugepaged_test_exit(mm
)) {
2629 hash_del(&mm_slot
->hash
);
2630 list_del(&mm_slot
->mm_node
);
2633 * Not strictly needed because the mm exited already.
2635 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2638 /* khugepaged_mm_lock actually not necessary for the below */
2639 free_mm_slot(mm_slot
);
2644 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2645 struct page
**hpage
)
2646 __releases(&khugepaged_mm_lock
)
2647 __acquires(&khugepaged_mm_lock
)
2649 struct mm_slot
*mm_slot
;
2650 struct mm_struct
*mm
;
2651 struct vm_area_struct
*vma
;
2655 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2657 if (khugepaged_scan
.mm_slot
)
2658 mm_slot
= khugepaged_scan
.mm_slot
;
2660 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2661 struct mm_slot
, mm_node
);
2662 khugepaged_scan
.address
= 0;
2663 khugepaged_scan
.mm_slot
= mm_slot
;
2665 spin_unlock(&khugepaged_mm_lock
);
2668 down_read(&mm
->mmap_sem
);
2669 if (unlikely(khugepaged_test_exit(mm
)))
2672 vma
= find_vma(mm
, khugepaged_scan
.address
);
2675 for (; vma
; vma
= vma
->vm_next
) {
2676 unsigned long hstart
, hend
;
2679 if (unlikely(khugepaged_test_exit(mm
))) {
2683 if (!hugepage_vma_check(vma
)) {
2688 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2689 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2692 if (khugepaged_scan
.address
> hend
)
2694 if (khugepaged_scan
.address
< hstart
)
2695 khugepaged_scan
.address
= hstart
;
2696 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2698 while (khugepaged_scan
.address
< hend
) {
2701 if (unlikely(khugepaged_test_exit(mm
)))
2702 goto breakouterloop
;
2704 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2705 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2707 ret
= khugepaged_scan_pmd(mm
, vma
,
2708 khugepaged_scan
.address
,
2710 /* move to next address */
2711 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2712 progress
+= HPAGE_PMD_NR
;
2714 /* we released mmap_sem so break loop */
2715 goto breakouterloop_mmap_sem
;
2716 if (progress
>= pages
)
2717 goto breakouterloop
;
2721 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
2722 breakouterloop_mmap_sem
:
2724 spin_lock(&khugepaged_mm_lock
);
2725 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2727 * Release the current mm_slot if this mm is about to die, or
2728 * if we scanned all vmas of this mm.
2730 if (khugepaged_test_exit(mm
) || !vma
) {
2732 * Make sure that if mm_users is reaching zero while
2733 * khugepaged runs here, khugepaged_exit will find
2734 * mm_slot not pointing to the exiting mm.
2736 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2737 khugepaged_scan
.mm_slot
= list_entry(
2738 mm_slot
->mm_node
.next
,
2739 struct mm_slot
, mm_node
);
2740 khugepaged_scan
.address
= 0;
2742 khugepaged_scan
.mm_slot
= NULL
;
2743 khugepaged_full_scans
++;
2746 collect_mm_slot(mm_slot
);
2752 static int khugepaged_has_work(void)
2754 return !list_empty(&khugepaged_scan
.mm_head
) &&
2755 khugepaged_enabled();
2758 static int khugepaged_wait_event(void)
2760 return !list_empty(&khugepaged_scan
.mm_head
) ||
2761 kthread_should_stop();
2764 static void khugepaged_do_scan(void)
2766 struct page
*hpage
= NULL
;
2767 unsigned int progress
= 0, pass_through_head
= 0;
2768 unsigned int pages
= khugepaged_pages_to_scan
;
2771 barrier(); /* write khugepaged_pages_to_scan to local stack */
2773 while (progress
< pages
) {
2774 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2779 if (unlikely(kthread_should_stop() || try_to_freeze()))
2782 spin_lock(&khugepaged_mm_lock
);
2783 if (!khugepaged_scan
.mm_slot
)
2784 pass_through_head
++;
2785 if (khugepaged_has_work() &&
2786 pass_through_head
< 2)
2787 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2791 spin_unlock(&khugepaged_mm_lock
);
2794 if (!IS_ERR_OR_NULL(hpage
))
2798 static bool khugepaged_should_wakeup(void)
2800 return kthread_should_stop() ||
2801 time_after_eq(jiffies
, khugepaged_sleep_expire
);
2804 static void khugepaged_wait_work(void)
2806 if (khugepaged_has_work()) {
2807 const unsigned long scan_sleep_jiffies
=
2808 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
);
2810 if (!scan_sleep_jiffies
)
2813 khugepaged_sleep_expire
= jiffies
+ scan_sleep_jiffies
;
2814 wait_event_freezable_timeout(khugepaged_wait
,
2815 khugepaged_should_wakeup(),
2816 scan_sleep_jiffies
);
2820 if (khugepaged_enabled())
2821 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2824 static int khugepaged(void *none
)
2826 struct mm_slot
*mm_slot
;
2829 set_user_nice(current
, MAX_NICE
);
2831 while (!kthread_should_stop()) {
2832 khugepaged_do_scan();
2833 khugepaged_wait_work();
2836 spin_lock(&khugepaged_mm_lock
);
2837 mm_slot
= khugepaged_scan
.mm_slot
;
2838 khugepaged_scan
.mm_slot
= NULL
;
2840 collect_mm_slot(mm_slot
);
2841 spin_unlock(&khugepaged_mm_lock
);
2845 static void __split_huge_zero_page_pmd(struct vm_area_struct
*vma
,
2846 unsigned long haddr
, pmd_t
*pmd
)
2848 struct mm_struct
*mm
= vma
->vm_mm
;
2853 /* leave pmd empty until pte is filled */
2854 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2856 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2857 pmd_populate(mm
, &_pmd
, pgtable
);
2859 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2861 entry
= pfn_pte(my_zero_pfn(haddr
), vma
->vm_page_prot
);
2862 entry
= pte_mkspecial(entry
);
2863 pte
= pte_offset_map(&_pmd
, haddr
);
2864 VM_BUG_ON(!pte_none(*pte
));
2865 set_pte_at(mm
, haddr
, pte
, entry
);
2868 smp_wmb(); /* make pte visible before pmd */
2869 pmd_populate(mm
, pmd
, pgtable
);
2870 put_huge_zero_page();
2873 static void __split_huge_pmd_locked(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2874 unsigned long haddr
, bool freeze
)
2876 struct mm_struct
*mm
= vma
->vm_mm
;
2880 bool young
, write
, dirty
;
2884 VM_BUG_ON(haddr
& ~HPAGE_PMD_MASK
);
2885 VM_BUG_ON_VMA(vma
->vm_start
> haddr
, vma
);
2886 VM_BUG_ON_VMA(vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
, vma
);
2887 VM_BUG_ON(!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
));
2889 count_vm_event(THP_SPLIT_PMD
);
2891 if (vma_is_dax(vma
)) {
2892 pmd_t _pmd
= pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2893 if (is_huge_zero_pmd(_pmd
))
2894 put_huge_zero_page();
2896 } else if (is_huge_zero_pmd(*pmd
)) {
2897 return __split_huge_zero_page_pmd(vma
, haddr
, pmd
);
2900 page
= pmd_page(*pmd
);
2901 VM_BUG_ON_PAGE(!page_count(page
), page
);
2902 page_ref_add(page
, HPAGE_PMD_NR
- 1);
2903 write
= pmd_write(*pmd
);
2904 young
= pmd_young(*pmd
);
2905 dirty
= pmd_dirty(*pmd
);
2907 pmdp_huge_split_prepare(vma
, haddr
, pmd
);
2908 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2909 pmd_populate(mm
, &_pmd
, pgtable
);
2911 for (i
= 0, addr
= haddr
; i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
) {
2914 * Note that NUMA hinting access restrictions are not
2915 * transferred to avoid any possibility of altering
2916 * permissions across VMAs.
2919 swp_entry_t swp_entry
;
2920 swp_entry
= make_migration_entry(page
+ i
, write
);
2921 entry
= swp_entry_to_pte(swp_entry
);
2923 entry
= mk_pte(page
+ i
, vma
->vm_page_prot
);
2924 entry
= maybe_mkwrite(entry
, vma
);
2926 entry
= pte_wrprotect(entry
);
2928 entry
= pte_mkold(entry
);
2931 SetPageDirty(page
+ i
);
2932 pte
= pte_offset_map(&_pmd
, addr
);
2933 BUG_ON(!pte_none(*pte
));
2934 set_pte_at(mm
, addr
, pte
, entry
);
2935 atomic_inc(&page
[i
]._mapcount
);
2940 * Set PG_double_map before dropping compound_mapcount to avoid
2941 * false-negative page_mapped().
2943 if (compound_mapcount(page
) > 1 && !TestSetPageDoubleMap(page
)) {
2944 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2945 atomic_inc(&page
[i
]._mapcount
);
2948 if (atomic_add_negative(-1, compound_mapcount_ptr(page
))) {
2949 /* Last compound_mapcount is gone. */
2950 __dec_zone_page_state(page
, NR_ANON_TRANSPARENT_HUGEPAGES
);
2951 if (TestClearPageDoubleMap(page
)) {
2952 /* No need in mapcount reference anymore */
2953 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2954 atomic_dec(&page
[i
]._mapcount
);
2958 smp_wmb(); /* make pte visible before pmd */
2960 * Up to this point the pmd is present and huge and userland has the
2961 * whole access to the hugepage during the split (which happens in
2962 * place). If we overwrite the pmd with the not-huge version pointing
2963 * to the pte here (which of course we could if all CPUs were bug
2964 * free), userland could trigger a small page size TLB miss on the
2965 * small sized TLB while the hugepage TLB entry is still established in
2966 * the huge TLB. Some CPU doesn't like that.
2967 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2968 * 383 on page 93. Intel should be safe but is also warns that it's
2969 * only safe if the permission and cache attributes of the two entries
2970 * loaded in the two TLB is identical (which should be the case here).
2971 * But it is generally safer to never allow small and huge TLB entries
2972 * for the same virtual address to be loaded simultaneously. So instead
2973 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2974 * current pmd notpresent (atomically because here the pmd_trans_huge
2975 * and pmd_trans_splitting must remain set at all times on the pmd
2976 * until the split is complete for this pmd), then we flush the SMP TLB
2977 * and finally we write the non-huge version of the pmd entry with
2980 pmdp_invalidate(vma
, haddr
, pmd
);
2981 pmd_populate(mm
, pmd
, pgtable
);
2984 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
2985 page_remove_rmap(page
+ i
, false);
2991 void __split_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2992 unsigned long address
, bool freeze
)
2995 struct mm_struct
*mm
= vma
->vm_mm
;
2996 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
2998 mmu_notifier_invalidate_range_start(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
2999 ptl
= pmd_lock(mm
, pmd
);
3000 if (pmd_trans_huge(*pmd
)) {
3001 struct page
*page
= pmd_page(*pmd
);
3002 if (PageMlocked(page
))
3003 clear_page_mlock(page
);
3004 } else if (!pmd_devmap(*pmd
))
3006 __split_huge_pmd_locked(vma
, pmd
, haddr
, freeze
);
3009 mmu_notifier_invalidate_range_end(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
3012 void split_huge_pmd_address(struct vm_area_struct
*vma
, unsigned long address
,
3013 bool freeze
, struct page
*page
)
3019 pgd
= pgd_offset(vma
->vm_mm
, address
);
3020 if (!pgd_present(*pgd
))
3023 pud
= pud_offset(pgd
, address
);
3024 if (!pud_present(*pud
))
3027 pmd
= pmd_offset(pud
, address
);
3028 if (!pmd_present(*pmd
) || (!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
)))
3032 * If caller asks to setup a migration entries, we need a page to check
3033 * pmd against. Otherwise we can end up replacing wrong page.
3035 VM_BUG_ON(freeze
&& !page
);
3036 if (page
&& page
!= pmd_page(*pmd
))
3040 * Caller holds the mmap_sem write mode or the anon_vma lock,
3041 * so a huge pmd cannot materialize from under us (khugepaged
3042 * holds both the mmap_sem write mode and the anon_vma lock
3045 __split_huge_pmd(vma
, pmd
, address
, freeze
);
3048 void vma_adjust_trans_huge(struct vm_area_struct
*vma
,
3049 unsigned long start
,
3054 * If the new start address isn't hpage aligned and it could
3055 * previously contain an hugepage: check if we need to split
3058 if (start
& ~HPAGE_PMD_MASK
&&
3059 (start
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3060 (start
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3061 split_huge_pmd_address(vma
, start
, false, NULL
);
3064 * If the new end address isn't hpage aligned and it could
3065 * previously contain an hugepage: check if we need to split
3068 if (end
& ~HPAGE_PMD_MASK
&&
3069 (end
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3070 (end
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3071 split_huge_pmd_address(vma
, end
, false, NULL
);
3074 * If we're also updating the vma->vm_next->vm_start, if the new
3075 * vm_next->vm_start isn't page aligned and it could previously
3076 * contain an hugepage: check if we need to split an huge pmd.
3078 if (adjust_next
> 0) {
3079 struct vm_area_struct
*next
= vma
->vm_next
;
3080 unsigned long nstart
= next
->vm_start
;
3081 nstart
+= adjust_next
<< PAGE_SHIFT
;
3082 if (nstart
& ~HPAGE_PMD_MASK
&&
3083 (nstart
& HPAGE_PMD_MASK
) >= next
->vm_start
&&
3084 (nstart
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= next
->vm_end
)
3085 split_huge_pmd_address(next
, nstart
, false, NULL
);
3089 static void freeze_page(struct page
*page
)
3091 enum ttu_flags ttu_flags
= TTU_MIGRATION
| TTU_IGNORE_MLOCK
|
3092 TTU_IGNORE_ACCESS
| TTU_RMAP_LOCKED
;
3095 VM_BUG_ON_PAGE(!PageHead(page
), page
);
3097 /* We only need TTU_SPLIT_HUGE_PMD once */
3098 ret
= try_to_unmap(page
, ttu_flags
| TTU_SPLIT_HUGE_PMD
);
3099 for (i
= 1; !ret
&& i
< HPAGE_PMD_NR
; i
++) {
3100 /* Cut short if the page is unmapped */
3101 if (page_count(page
) == 1)
3104 ret
= try_to_unmap(page
+ i
, ttu_flags
);
3109 static void unfreeze_page(struct page
*page
)
3113 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3114 remove_migration_ptes(page
+ i
, page
+ i
, true);
3117 static void __split_huge_page_tail(struct page
*head
, int tail
,
3118 struct lruvec
*lruvec
, struct list_head
*list
)
3120 struct page
*page_tail
= head
+ tail
;
3122 VM_BUG_ON_PAGE(atomic_read(&page_tail
->_mapcount
) != -1, page_tail
);
3123 VM_BUG_ON_PAGE(page_ref_count(page_tail
) != 0, page_tail
);
3126 * tail_page->_refcount is zero and not changing from under us. But
3127 * get_page_unless_zero() may be running from under us on the
3128 * tail_page. If we used atomic_set() below instead of atomic_inc(), we
3129 * would then run atomic_set() concurrently with
3130 * get_page_unless_zero(), and atomic_set() is implemented in C not
3131 * using locked ops. spin_unlock on x86 sometime uses locked ops
3132 * because of PPro errata 66, 92, so unless somebody can guarantee
3133 * atomic_set() here would be safe on all archs (and not only on x86),
3134 * it's safer to use atomic_inc().
3136 page_ref_inc(page_tail
);
3138 page_tail
->flags
&= ~PAGE_FLAGS_CHECK_AT_PREP
;
3139 page_tail
->flags
|= (head
->flags
&
3140 ((1L << PG_referenced
) |
3141 (1L << PG_swapbacked
) |
3142 (1L << PG_mlocked
) |
3143 (1L << PG_uptodate
) |
3146 (1L << PG_unevictable
) |
3150 * After clearing PageTail the gup refcount can be released.
3151 * Page flags also must be visible before we make the page non-compound.
3155 clear_compound_head(page_tail
);
3157 if (page_is_young(head
))
3158 set_page_young(page_tail
);
3159 if (page_is_idle(head
))
3160 set_page_idle(page_tail
);
3162 /* ->mapping in first tail page is compound_mapcount */
3163 VM_BUG_ON_PAGE(tail
> 2 && page_tail
->mapping
!= TAIL_MAPPING
,
3165 page_tail
->mapping
= head
->mapping
;
3167 page_tail
->index
= head
->index
+ tail
;
3168 page_cpupid_xchg_last(page_tail
, page_cpupid_last(head
));
3169 lru_add_page_tail(head
, page_tail
, lruvec
, list
);
3172 static void __split_huge_page(struct page
*page
, struct list_head
*list
)
3174 struct page
*head
= compound_head(page
);
3175 struct zone
*zone
= page_zone(head
);
3176 struct lruvec
*lruvec
;
3179 /* prevent PageLRU to go away from under us, and freeze lru stats */
3180 spin_lock_irq(&zone
->lru_lock
);
3181 lruvec
= mem_cgroup_page_lruvec(head
, zone
);
3183 /* complete memcg works before add pages to LRU */
3184 mem_cgroup_split_huge_fixup(head
);
3186 for (i
= HPAGE_PMD_NR
- 1; i
>= 1; i
--)
3187 __split_huge_page_tail(head
, i
, lruvec
, list
);
3189 ClearPageCompound(head
);
3190 spin_unlock_irq(&zone
->lru_lock
);
3192 unfreeze_page(head
);
3194 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3195 struct page
*subpage
= head
+ i
;
3196 if (subpage
== page
)
3198 unlock_page(subpage
);
3201 * Subpages may be freed if there wasn't any mapping
3202 * like if add_to_swap() is running on a lru page that
3203 * had its mapping zapped. And freeing these pages
3204 * requires taking the lru_lock so we do the put_page
3205 * of the tail pages after the split is complete.
3211 int total_mapcount(struct page
*page
)
3215 VM_BUG_ON_PAGE(PageTail(page
), page
);
3217 if (likely(!PageCompound(page
)))
3218 return atomic_read(&page
->_mapcount
) + 1;
3220 ret
= compound_mapcount(page
);
3223 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3224 ret
+= atomic_read(&page
[i
]._mapcount
) + 1;
3225 if (PageDoubleMap(page
))
3226 ret
-= HPAGE_PMD_NR
;
3231 * This calculates accurately how many mappings a transparent hugepage
3232 * has (unlike page_mapcount() which isn't fully accurate). This full
3233 * accuracy is primarily needed to know if copy-on-write faults can
3234 * reuse the page and change the mapping to read-write instead of
3235 * copying them. At the same time this returns the total_mapcount too.
3237 * The function returns the highest mapcount any one of the subpages
3238 * has. If the return value is one, even if different processes are
3239 * mapping different subpages of the transparent hugepage, they can
3240 * all reuse it, because each process is reusing a different subpage.
3242 * The total_mapcount is instead counting all virtual mappings of the
3243 * subpages. If the total_mapcount is equal to "one", it tells the
3244 * caller all mappings belong to the same "mm" and in turn the
3245 * anon_vma of the transparent hugepage can become the vma->anon_vma
3246 * local one as no other process may be mapping any of the subpages.
3248 * It would be more accurate to replace page_mapcount() with
3249 * page_trans_huge_mapcount(), however we only use
3250 * page_trans_huge_mapcount() in the copy-on-write faults where we
3251 * need full accuracy to avoid breaking page pinning, because
3252 * page_trans_huge_mapcount() is slower than page_mapcount().
3254 int page_trans_huge_mapcount(struct page
*page
, int *total_mapcount
)
3256 int i
, ret
, _total_mapcount
, mapcount
;
3258 /* hugetlbfs shouldn't call it */
3259 VM_BUG_ON_PAGE(PageHuge(page
), page
);
3261 if (likely(!PageTransCompound(page
))) {
3262 mapcount
= atomic_read(&page
->_mapcount
) + 1;
3264 *total_mapcount
= mapcount
;
3268 page
= compound_head(page
);
3270 _total_mapcount
= ret
= 0;
3271 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3272 mapcount
= atomic_read(&page
[i
]._mapcount
) + 1;
3273 ret
= max(ret
, mapcount
);
3274 _total_mapcount
+= mapcount
;
3276 if (PageDoubleMap(page
)) {
3278 _total_mapcount
-= HPAGE_PMD_NR
;
3280 mapcount
= compound_mapcount(page
);
3282 _total_mapcount
+= mapcount
;
3284 *total_mapcount
= _total_mapcount
;
3289 * This function splits huge page into normal pages. @page can point to any
3290 * subpage of huge page to split. Split doesn't change the position of @page.
3292 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3293 * The huge page must be locked.
3295 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3297 * Both head page and tail pages will inherit mapping, flags, and so on from
3300 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3301 * they are not mapped.
3303 * Returns 0 if the hugepage is split successfully.
3304 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3307 int split_huge_page_to_list(struct page
*page
, struct list_head
*list
)
3309 struct page
*head
= compound_head(page
);
3310 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(head
));
3311 struct anon_vma
*anon_vma
;
3312 int count
, mapcount
, ret
;
3314 unsigned long flags
;
3316 VM_BUG_ON_PAGE(is_huge_zero_page(page
), page
);
3317 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
3318 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
3319 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
3320 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
3323 * The caller does not necessarily hold an mmap_sem that would prevent
3324 * the anon_vma disappearing so we first we take a reference to it
3325 * and then lock the anon_vma for write. This is similar to
3326 * page_lock_anon_vma_read except the write lock is taken to serialise
3327 * against parallel split or collapse operations.
3329 anon_vma
= page_get_anon_vma(head
);
3334 anon_vma_lock_write(anon_vma
);
3337 * Racy check if we can split the page, before freeze_page() will
3340 if (total_mapcount(head
) != page_count(head
) - 1) {
3345 mlocked
= PageMlocked(page
);
3347 VM_BUG_ON_PAGE(compound_mapcount(head
), head
);
3349 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3353 /* Prevent deferred_split_scan() touching ->_refcount */
3354 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3355 count
= page_count(head
);
3356 mapcount
= total_mapcount(head
);
3357 if (!mapcount
&& count
== 1) {
3358 if (!list_empty(page_deferred_list(head
))) {
3359 pgdata
->split_queue_len
--;
3360 list_del(page_deferred_list(head
));
3362 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3363 __split_huge_page(page
, list
);
3365 } else if (IS_ENABLED(CONFIG_DEBUG_VM
) && mapcount
) {
3366 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3367 pr_alert("total_mapcount: %u, page_count(): %u\n",
3370 dump_page(head
, NULL
);
3371 dump_page(page
, "total_mapcount(head) > 0");
3374 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3375 unfreeze_page(head
);
3380 anon_vma_unlock_write(anon_vma
);
3381 put_anon_vma(anon_vma
);
3383 count_vm_event(!ret
? THP_SPLIT_PAGE
: THP_SPLIT_PAGE_FAILED
);
3387 void free_transhuge_page(struct page
*page
)
3389 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
3390 unsigned long flags
;
3392 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3393 if (!list_empty(page_deferred_list(page
))) {
3394 pgdata
->split_queue_len
--;
3395 list_del(page_deferred_list(page
));
3397 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3398 free_compound_page(page
);
3401 void deferred_split_huge_page(struct page
*page
)
3403 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
3404 unsigned long flags
;
3406 VM_BUG_ON_PAGE(!PageTransHuge(page
), page
);
3408 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3409 if (list_empty(page_deferred_list(page
))) {
3410 count_vm_event(THP_DEFERRED_SPLIT_PAGE
);
3411 list_add_tail(page_deferred_list(page
), &pgdata
->split_queue
);
3412 pgdata
->split_queue_len
++;
3414 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3417 static unsigned long deferred_split_count(struct shrinker
*shrink
,
3418 struct shrink_control
*sc
)
3420 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
3421 return ACCESS_ONCE(pgdata
->split_queue_len
);
3424 static unsigned long deferred_split_scan(struct shrinker
*shrink
,
3425 struct shrink_control
*sc
)
3427 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
3428 unsigned long flags
;
3429 LIST_HEAD(list
), *pos
, *next
;
3433 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3434 /* Take pin on all head pages to avoid freeing them under us */
3435 list_for_each_safe(pos
, next
, &pgdata
->split_queue
) {
3436 page
= list_entry((void *)pos
, struct page
, mapping
);
3437 page
= compound_head(page
);
3438 if (get_page_unless_zero(page
)) {
3439 list_move(page_deferred_list(page
), &list
);
3441 /* We lost race with put_compound_page() */
3442 list_del_init(page_deferred_list(page
));
3443 pgdata
->split_queue_len
--;
3445 if (!--sc
->nr_to_scan
)
3448 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3450 list_for_each_safe(pos
, next
, &list
) {
3451 page
= list_entry((void *)pos
, struct page
, mapping
);
3453 /* split_huge_page() removes page from list on success */
3454 if (!split_huge_page(page
))
3460 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3461 list_splice_tail(&list
, &pgdata
->split_queue
);
3462 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3465 * Stop shrinker if we didn't split any page, but the queue is empty.
3466 * This can happen if pages were freed under us.
3468 if (!split
&& list_empty(&pgdata
->split_queue
))
3473 static struct shrinker deferred_split_shrinker
= {
3474 .count_objects
= deferred_split_count
,
3475 .scan_objects
= deferred_split_scan
,
3476 .seeks
= DEFAULT_SEEKS
,
3477 .flags
= SHRINKER_NUMA_AWARE
,
3480 #ifdef CONFIG_DEBUG_FS
3481 static int split_huge_pages_set(void *data
, u64 val
)
3485 unsigned long pfn
, max_zone_pfn
;
3486 unsigned long total
= 0, split
= 0;
3491 for_each_populated_zone(zone
) {
3492 max_zone_pfn
= zone_end_pfn(zone
);
3493 for (pfn
= zone
->zone_start_pfn
; pfn
< max_zone_pfn
; pfn
++) {
3494 if (!pfn_valid(pfn
))
3497 page
= pfn_to_page(pfn
);
3498 if (!get_page_unless_zero(page
))
3501 if (zone
!= page_zone(page
))
3504 if (!PageHead(page
) || !PageAnon(page
) ||
3510 if (!split_huge_page(page
))
3518 pr_info("%lu of %lu THP split\n", split
, total
);
3522 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops
, NULL
, split_huge_pages_set
,
3525 static int __init
split_huge_pages_debugfs(void)
3529 ret
= debugfs_create_file("split_huge_pages", 0200, NULL
, NULL
,
3530 &split_huge_pages_fops
);
3532 pr_warn("Failed to create split_huge_pages in debugfs");
3535 late_initcall(split_huge_pages_debugfs
);