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 split_huge_page(page
);
1633 if (PageDirty(page
))
1634 ClearPageDirty(page
);
1637 if (PageActive(page
))
1638 deactivate_page(page
);
1640 if (pmd_young(orig_pmd
) || pmd_dirty(orig_pmd
)) {
1641 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1643 orig_pmd
= pmd_mkold(orig_pmd
);
1644 orig_pmd
= pmd_mkclean(orig_pmd
);
1646 set_pmd_at(mm
, addr
, pmd
, orig_pmd
);
1647 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1656 int zap_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1657 pmd_t
*pmd
, unsigned long addr
)
1662 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1666 * For architectures like ppc64 we look at deposited pgtable
1667 * when calling pmdp_huge_get_and_clear. So do the
1668 * pgtable_trans_huge_withdraw after finishing pmdp related
1671 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1673 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1674 if (vma_is_dax(vma
)) {
1676 if (is_huge_zero_pmd(orig_pmd
))
1677 tlb_remove_page(tlb
, pmd_page(orig_pmd
));
1678 } else if (is_huge_zero_pmd(orig_pmd
)) {
1679 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1680 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1682 tlb_remove_page(tlb
, pmd_page(orig_pmd
));
1684 struct page
*page
= pmd_page(orig_pmd
);
1685 page_remove_rmap(page
, true);
1686 VM_BUG_ON_PAGE(page_mapcount(page
) < 0, page
);
1687 add_mm_counter(tlb
->mm
, MM_ANONPAGES
, -HPAGE_PMD_NR
);
1688 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1689 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1690 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1692 tlb_remove_page(tlb
, page
);
1697 bool move_huge_pmd(struct vm_area_struct
*vma
, unsigned long old_addr
,
1698 unsigned long new_addr
, unsigned long old_end
,
1699 pmd_t
*old_pmd
, pmd_t
*new_pmd
)
1701 spinlock_t
*old_ptl
, *new_ptl
;
1703 struct mm_struct
*mm
= vma
->vm_mm
;
1705 if ((old_addr
& ~HPAGE_PMD_MASK
) ||
1706 (new_addr
& ~HPAGE_PMD_MASK
) ||
1707 old_end
- old_addr
< HPAGE_PMD_SIZE
)
1711 * The destination pmd shouldn't be established, free_pgtables()
1712 * should have release it.
1714 if (WARN_ON(!pmd_none(*new_pmd
))) {
1715 VM_BUG_ON(pmd_trans_huge(*new_pmd
));
1720 * We don't have to worry about the ordering of src and dst
1721 * ptlocks because exclusive mmap_sem prevents deadlock.
1723 old_ptl
= __pmd_trans_huge_lock(old_pmd
, vma
);
1725 new_ptl
= pmd_lockptr(mm
, new_pmd
);
1726 if (new_ptl
!= old_ptl
)
1727 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
1728 pmd
= pmdp_huge_get_and_clear(mm
, old_addr
, old_pmd
);
1729 VM_BUG_ON(!pmd_none(*new_pmd
));
1731 if (pmd_move_must_withdraw(new_ptl
, old_ptl
) &&
1732 vma_is_anonymous(vma
)) {
1734 pgtable
= pgtable_trans_huge_withdraw(mm
, old_pmd
);
1735 pgtable_trans_huge_deposit(mm
, new_pmd
, pgtable
);
1737 set_pmd_at(mm
, new_addr
, new_pmd
, pmd_mksoft_dirty(pmd
));
1738 if (new_ptl
!= old_ptl
)
1739 spin_unlock(new_ptl
);
1740 spin_unlock(old_ptl
);
1748 * - 0 if PMD could not be locked
1749 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1750 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1752 int change_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1753 unsigned long addr
, pgprot_t newprot
, int prot_numa
)
1755 struct mm_struct
*mm
= vma
->vm_mm
;
1759 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1762 bool preserve_write
= prot_numa
&& pmd_write(*pmd
);
1766 * Avoid trapping faults against the zero page. The read-only
1767 * data is likely to be read-cached on the local CPU and
1768 * local/remote hits to the zero page are not interesting.
1770 if (prot_numa
&& is_huge_zero_pmd(*pmd
)) {
1775 if (!prot_numa
|| !pmd_protnone(*pmd
)) {
1776 entry
= pmdp_huge_get_and_clear_notify(mm
, addr
, pmd
);
1777 entry
= pmd_modify(entry
, newprot
);
1779 entry
= pmd_mkwrite(entry
);
1781 set_pmd_at(mm
, addr
, pmd
, entry
);
1782 BUG_ON(!preserve_write
&& pmd_write(entry
));
1791 * Returns true if a given pmd maps a thp, false otherwise.
1793 * Note that if it returns true, this routine returns without unlocking page
1794 * table lock. So callers must unlock it.
1796 spinlock_t
*__pmd_trans_huge_lock(pmd_t
*pmd
, struct vm_area_struct
*vma
)
1799 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1800 if (likely(pmd_trans_huge(*pmd
) || pmd_devmap(*pmd
)))
1806 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1808 int hugepage_madvise(struct vm_area_struct
*vma
,
1809 unsigned long *vm_flags
, int advice
)
1815 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1816 * can't handle this properly after s390_enable_sie, so we simply
1817 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1819 if (mm_has_pgste(vma
->vm_mm
))
1823 * Be somewhat over-protective like KSM for now!
1825 if (*vm_flags
& VM_NO_THP
)
1827 *vm_flags
&= ~VM_NOHUGEPAGE
;
1828 *vm_flags
|= VM_HUGEPAGE
;
1830 * If the vma become good for khugepaged to scan,
1831 * register it here without waiting a page fault that
1832 * may not happen any time soon.
1834 if (unlikely(khugepaged_enter_vma_merge(vma
, *vm_flags
)))
1837 case MADV_NOHUGEPAGE
:
1839 * Be somewhat over-protective like KSM for now!
1841 if (*vm_flags
& VM_NO_THP
)
1843 *vm_flags
&= ~VM_HUGEPAGE
;
1844 *vm_flags
|= VM_NOHUGEPAGE
;
1846 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1847 * this vma even if we leave the mm registered in khugepaged if
1848 * it got registered before VM_NOHUGEPAGE was set.
1856 static int __init
khugepaged_slab_init(void)
1858 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
1859 sizeof(struct mm_slot
),
1860 __alignof__(struct mm_slot
), 0, NULL
);
1867 static void __init
khugepaged_slab_exit(void)
1869 kmem_cache_destroy(mm_slot_cache
);
1872 static inline struct mm_slot
*alloc_mm_slot(void)
1874 if (!mm_slot_cache
) /* initialization failed */
1876 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
1879 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
1881 kmem_cache_free(mm_slot_cache
, mm_slot
);
1884 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
1886 struct mm_slot
*mm_slot
;
1888 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
1889 if (mm
== mm_slot
->mm
)
1895 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
1896 struct mm_slot
*mm_slot
)
1899 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
1902 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
1904 return atomic_read(&mm
->mm_users
) == 0;
1907 int __khugepaged_enter(struct mm_struct
*mm
)
1909 struct mm_slot
*mm_slot
;
1912 mm_slot
= alloc_mm_slot();
1916 /* __khugepaged_exit() must not run from under us */
1917 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
1918 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
1919 free_mm_slot(mm_slot
);
1923 spin_lock(&khugepaged_mm_lock
);
1924 insert_to_mm_slots_hash(mm
, mm_slot
);
1926 * Insert just behind the scanning cursor, to let the area settle
1929 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
1930 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
1931 spin_unlock(&khugepaged_mm_lock
);
1933 atomic_inc(&mm
->mm_count
);
1935 wake_up_interruptible(&khugepaged_wait
);
1940 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
1941 unsigned long vm_flags
)
1943 unsigned long hstart
, hend
;
1946 * Not yet faulted in so we will register later in the
1947 * page fault if needed.
1950 if (vma
->vm_ops
|| (vm_flags
& VM_NO_THP
))
1951 /* khugepaged not yet working on file or special mappings */
1953 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1954 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1956 return khugepaged_enter(vma
, vm_flags
);
1960 void __khugepaged_exit(struct mm_struct
*mm
)
1962 struct mm_slot
*mm_slot
;
1965 spin_lock(&khugepaged_mm_lock
);
1966 mm_slot
= get_mm_slot(mm
);
1967 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
1968 hash_del(&mm_slot
->hash
);
1969 list_del(&mm_slot
->mm_node
);
1972 spin_unlock(&khugepaged_mm_lock
);
1975 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
1976 free_mm_slot(mm_slot
);
1978 } else if (mm_slot
) {
1980 * This is required to serialize against
1981 * khugepaged_test_exit() (which is guaranteed to run
1982 * under mmap sem read mode). Stop here (after we
1983 * return all pagetables will be destroyed) until
1984 * khugepaged has finished working on the pagetables
1985 * under the mmap_sem.
1987 down_write(&mm
->mmap_sem
);
1988 up_write(&mm
->mmap_sem
);
1992 static void release_pte_page(struct page
*page
)
1994 /* 0 stands for page_is_file_cache(page) == false */
1995 dec_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
1997 putback_lru_page(page
);
2000 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
)
2002 while (--_pte
>= pte
) {
2003 pte_t pteval
= *_pte
;
2004 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)))
2005 release_pte_page(pte_page(pteval
));
2009 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
2010 unsigned long address
,
2013 struct page
*page
= NULL
;
2015 int none_or_zero
= 0, result
= 0;
2016 bool referenced
= false, writable
= false;
2018 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2019 _pte
++, address
+= PAGE_SIZE
) {
2020 pte_t pteval
= *_pte
;
2021 if (pte_none(pteval
) || (pte_present(pteval
) &&
2022 is_zero_pfn(pte_pfn(pteval
)))) {
2023 if (!userfaultfd_armed(vma
) &&
2024 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2027 result
= SCAN_EXCEED_NONE_PTE
;
2031 if (!pte_present(pteval
)) {
2032 result
= SCAN_PTE_NON_PRESENT
;
2035 page
= vm_normal_page(vma
, address
, pteval
);
2036 if (unlikely(!page
)) {
2037 result
= SCAN_PAGE_NULL
;
2041 VM_BUG_ON_PAGE(PageCompound(page
), page
);
2042 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
2043 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
2046 * We can do it before isolate_lru_page because the
2047 * page can't be freed from under us. NOTE: PG_lock
2048 * is needed to serialize against split_huge_page
2049 * when invoked from the VM.
2051 if (!trylock_page(page
)) {
2052 result
= SCAN_PAGE_LOCK
;
2057 * cannot use mapcount: can't collapse if there's a gup pin.
2058 * The page must only be referenced by the scanned process
2059 * and page swap cache.
2061 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2063 result
= SCAN_PAGE_COUNT
;
2066 if (pte_write(pteval
)) {
2069 if (PageSwapCache(page
) &&
2070 !reuse_swap_page(page
, NULL
)) {
2072 result
= SCAN_SWAP_CACHE_PAGE
;
2076 * Page is not in the swap cache. It can be collapsed
2082 * Isolate the page to avoid collapsing an hugepage
2083 * currently in use by the VM.
2085 if (isolate_lru_page(page
)) {
2087 result
= SCAN_DEL_PAGE_LRU
;
2090 /* 0 stands for page_is_file_cache(page) == false */
2091 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
2092 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
2093 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2095 /* If there is no mapped pte young don't collapse the page */
2096 if (pte_young(pteval
) ||
2097 page_is_young(page
) || PageReferenced(page
) ||
2098 mmu_notifier_test_young(vma
->vm_mm
, address
))
2101 if (likely(writable
)) {
2102 if (likely(referenced
)) {
2103 result
= SCAN_SUCCEED
;
2104 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
2105 referenced
, writable
, result
);
2109 result
= SCAN_PAGE_RO
;
2113 release_pte_pages(pte
, _pte
);
2114 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
2115 referenced
, writable
, result
);
2119 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
2120 struct vm_area_struct
*vma
,
2121 unsigned long address
,
2125 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
; _pte
++) {
2126 pte_t pteval
= *_pte
;
2127 struct page
*src_page
;
2129 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2130 clear_user_highpage(page
, address
);
2131 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
2132 if (is_zero_pfn(pte_pfn(pteval
))) {
2134 * ptl mostly unnecessary.
2138 * paravirt calls inside pte_clear here are
2141 pte_clear(vma
->vm_mm
, address
, _pte
);
2145 src_page
= pte_page(pteval
);
2146 copy_user_highpage(page
, src_page
, address
, vma
);
2147 VM_BUG_ON_PAGE(page_mapcount(src_page
) != 1, src_page
);
2148 release_pte_page(src_page
);
2150 * ptl mostly unnecessary, but preempt has to
2151 * be disabled to update the per-cpu stats
2152 * inside page_remove_rmap().
2156 * paravirt calls inside pte_clear here are
2159 pte_clear(vma
->vm_mm
, address
, _pte
);
2160 page_remove_rmap(src_page
, false);
2162 free_page_and_swap_cache(src_page
);
2165 address
+= PAGE_SIZE
;
2170 static void khugepaged_alloc_sleep(void)
2174 add_wait_queue(&khugepaged_wait
, &wait
);
2175 freezable_schedule_timeout_interruptible(
2176 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
2177 remove_wait_queue(&khugepaged_wait
, &wait
);
2180 static int khugepaged_node_load
[MAX_NUMNODES
];
2182 static bool khugepaged_scan_abort(int nid
)
2187 * If zone_reclaim_mode is disabled, then no extra effort is made to
2188 * allocate memory locally.
2190 if (!zone_reclaim_mode
)
2193 /* If there is a count for this node already, it must be acceptable */
2194 if (khugepaged_node_load
[nid
])
2197 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
2198 if (!khugepaged_node_load
[i
])
2200 if (node_distance(nid
, i
) > RECLAIM_DISTANCE
)
2207 static int khugepaged_find_target_node(void)
2209 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
2210 int nid
, target_node
= 0, max_value
= 0;
2212 /* find first node with max normal pages hit */
2213 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
2214 if (khugepaged_node_load
[nid
] > max_value
) {
2215 max_value
= khugepaged_node_load
[nid
];
2219 /* do some balance if several nodes have the same hit record */
2220 if (target_node
<= last_khugepaged_target_node
)
2221 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
2223 if (max_value
== khugepaged_node_load
[nid
]) {
2228 last_khugepaged_target_node
= target_node
;
2232 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2234 if (IS_ERR(*hpage
)) {
2240 khugepaged_alloc_sleep();
2241 } else if (*hpage
) {
2249 static struct page
*
2250 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2251 unsigned long address
, int node
)
2253 VM_BUG_ON_PAGE(*hpage
, *hpage
);
2256 * Before allocating the hugepage, release the mmap_sem read lock.
2257 * The allocation can take potentially a long time if it involves
2258 * sync compaction, and we do not need to hold the mmap_sem during
2259 * that. We will recheck the vma after taking it again in write mode.
2261 up_read(&mm
->mmap_sem
);
2263 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
2264 if (unlikely(!*hpage
)) {
2265 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2266 *hpage
= ERR_PTR(-ENOMEM
);
2270 prep_transhuge_page(*hpage
);
2271 count_vm_event(THP_COLLAPSE_ALLOC
);
2275 static int khugepaged_find_target_node(void)
2280 static inline struct page
*alloc_khugepaged_hugepage(void)
2284 page
= alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2287 prep_transhuge_page(page
);
2291 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
2296 hpage
= alloc_khugepaged_hugepage();
2298 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2303 khugepaged_alloc_sleep();
2305 count_vm_event(THP_COLLAPSE_ALLOC
);
2306 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
2311 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2314 *hpage
= khugepaged_alloc_hugepage(wait
);
2316 if (unlikely(!*hpage
))
2322 static struct page
*
2323 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2324 unsigned long address
, int node
)
2326 up_read(&mm
->mmap_sem
);
2333 static bool hugepage_vma_check(struct vm_area_struct
*vma
)
2335 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
2336 (vma
->vm_flags
& VM_NOHUGEPAGE
))
2338 if (!vma
->anon_vma
|| vma
->vm_ops
)
2340 if (is_vma_temporary_stack(vma
))
2342 return !(vma
->vm_flags
& VM_NO_THP
);
2345 static void collapse_huge_page(struct mm_struct
*mm
,
2346 unsigned long address
,
2347 struct page
**hpage
,
2348 struct vm_area_struct
*vma
,
2354 struct page
*new_page
;
2355 spinlock_t
*pmd_ptl
, *pte_ptl
;
2356 int isolated
= 0, result
= 0;
2357 unsigned long hstart
, hend
;
2358 struct mem_cgroup
*memcg
;
2359 unsigned long mmun_start
; /* For mmu_notifiers */
2360 unsigned long mmun_end
; /* For mmu_notifiers */
2363 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2365 /* Only allocate from the target node */
2366 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE
| __GFP_THISNODE
;
2368 /* release the mmap_sem read lock. */
2369 new_page
= khugepaged_alloc_page(hpage
, gfp
, mm
, address
, node
);
2371 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
2375 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, gfp
, &memcg
, true))) {
2376 result
= SCAN_CGROUP_CHARGE_FAIL
;
2381 * Prevent all access to pagetables with the exception of
2382 * gup_fast later hanlded by the ptep_clear_flush and the VM
2383 * handled by the anon_vma lock + PG_lock.
2385 down_write(&mm
->mmap_sem
);
2386 if (unlikely(khugepaged_test_exit(mm
))) {
2387 result
= SCAN_ANY_PROCESS
;
2391 vma
= find_vma(mm
, address
);
2393 result
= SCAN_VMA_NULL
;
2396 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2397 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2398 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
) {
2399 result
= SCAN_ADDRESS_RANGE
;
2402 if (!hugepage_vma_check(vma
)) {
2403 result
= SCAN_VMA_CHECK
;
2406 pmd
= mm_find_pmd(mm
, address
);
2408 result
= SCAN_PMD_NULL
;
2412 anon_vma_lock_write(vma
->anon_vma
);
2414 pte
= pte_offset_map(pmd
, address
);
2415 pte_ptl
= pte_lockptr(mm
, pmd
);
2417 mmun_start
= address
;
2418 mmun_end
= address
+ HPAGE_PMD_SIZE
;
2419 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
2420 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
2422 * After this gup_fast can't run anymore. This also removes
2423 * any huge TLB entry from the CPU so we won't allow
2424 * huge and small TLB entries for the same virtual address
2425 * to avoid the risk of CPU bugs in that area.
2427 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
2428 spin_unlock(pmd_ptl
);
2429 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
2432 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
);
2433 spin_unlock(pte_ptl
);
2435 if (unlikely(!isolated
)) {
2438 BUG_ON(!pmd_none(*pmd
));
2440 * We can only use set_pmd_at when establishing
2441 * hugepmds and never for establishing regular pmds that
2442 * points to regular pagetables. Use pmd_populate for that
2444 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
2445 spin_unlock(pmd_ptl
);
2446 anon_vma_unlock_write(vma
->anon_vma
);
2452 * All pages are isolated and locked so anon_vma rmap
2453 * can't run anymore.
2455 anon_vma_unlock_write(vma
->anon_vma
);
2457 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
);
2459 __SetPageUptodate(new_page
);
2460 pgtable
= pmd_pgtable(_pmd
);
2462 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
2463 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
2466 * spin_lock() below is not the equivalent of smp_wmb(), so
2467 * this is needed to avoid the copy_huge_page writes to become
2468 * visible after the set_pmd_at() write.
2473 BUG_ON(!pmd_none(*pmd
));
2474 page_add_new_anon_rmap(new_page
, vma
, address
, true);
2475 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
2476 lru_cache_add_active_or_unevictable(new_page
, vma
);
2477 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
2478 set_pmd_at(mm
, address
, pmd
, _pmd
);
2479 update_mmu_cache_pmd(vma
, address
, pmd
);
2480 spin_unlock(pmd_ptl
);
2484 khugepaged_pages_collapsed
++;
2485 result
= SCAN_SUCCEED
;
2487 up_write(&mm
->mmap_sem
);
2488 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2492 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2495 mem_cgroup_cancel_charge(new_page
, memcg
, true);
2499 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
2500 struct vm_area_struct
*vma
,
2501 unsigned long address
,
2502 struct page
**hpage
)
2506 int ret
= 0, none_or_zero
= 0, result
= 0;
2507 struct page
*page
= NULL
;
2508 unsigned long _address
;
2510 int node
= NUMA_NO_NODE
;
2511 bool writable
= false, referenced
= false;
2513 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2515 pmd
= mm_find_pmd(mm
, address
);
2517 result
= SCAN_PMD_NULL
;
2521 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
2522 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
2523 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2524 _pte
++, _address
+= PAGE_SIZE
) {
2525 pte_t pteval
= *_pte
;
2526 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2527 if (!userfaultfd_armed(vma
) &&
2528 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2531 result
= SCAN_EXCEED_NONE_PTE
;
2535 if (!pte_present(pteval
)) {
2536 result
= SCAN_PTE_NON_PRESENT
;
2539 if (pte_write(pteval
))
2542 page
= vm_normal_page(vma
, _address
, pteval
);
2543 if (unlikely(!page
)) {
2544 result
= SCAN_PAGE_NULL
;
2548 /* TODO: teach khugepaged to collapse THP mapped with pte */
2549 if (PageCompound(page
)) {
2550 result
= SCAN_PAGE_COMPOUND
;
2555 * Record which node the original page is from and save this
2556 * information to khugepaged_node_load[].
2557 * Khupaged will allocate hugepage from the node has the max
2560 node
= page_to_nid(page
);
2561 if (khugepaged_scan_abort(node
)) {
2562 result
= SCAN_SCAN_ABORT
;
2565 khugepaged_node_load
[node
]++;
2566 if (!PageLRU(page
)) {
2567 result
= SCAN_PAGE_LRU
;
2570 if (PageLocked(page
)) {
2571 result
= SCAN_PAGE_LOCK
;
2574 if (!PageAnon(page
)) {
2575 result
= SCAN_PAGE_ANON
;
2580 * cannot use mapcount: can't collapse if there's a gup pin.
2581 * The page must only be referenced by the scanned process
2582 * and page swap cache.
2584 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2585 result
= SCAN_PAGE_COUNT
;
2588 if (pte_young(pteval
) ||
2589 page_is_young(page
) || PageReferenced(page
) ||
2590 mmu_notifier_test_young(vma
->vm_mm
, address
))
2595 result
= SCAN_SUCCEED
;
2598 result
= SCAN_NO_REFERENCED_PAGE
;
2601 result
= SCAN_PAGE_RO
;
2604 pte_unmap_unlock(pte
, ptl
);
2606 node
= khugepaged_find_target_node();
2607 /* collapse_huge_page will return with the mmap_sem released */
2608 collapse_huge_page(mm
, address
, hpage
, vma
, node
);
2611 trace_mm_khugepaged_scan_pmd(mm
, page
, writable
, referenced
,
2612 none_or_zero
, result
);
2616 static void collect_mm_slot(struct mm_slot
*mm_slot
)
2618 struct mm_struct
*mm
= mm_slot
->mm
;
2620 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2622 if (khugepaged_test_exit(mm
)) {
2624 hash_del(&mm_slot
->hash
);
2625 list_del(&mm_slot
->mm_node
);
2628 * Not strictly needed because the mm exited already.
2630 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2633 /* khugepaged_mm_lock actually not necessary for the below */
2634 free_mm_slot(mm_slot
);
2639 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2640 struct page
**hpage
)
2641 __releases(&khugepaged_mm_lock
)
2642 __acquires(&khugepaged_mm_lock
)
2644 struct mm_slot
*mm_slot
;
2645 struct mm_struct
*mm
;
2646 struct vm_area_struct
*vma
;
2650 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2652 if (khugepaged_scan
.mm_slot
)
2653 mm_slot
= khugepaged_scan
.mm_slot
;
2655 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2656 struct mm_slot
, mm_node
);
2657 khugepaged_scan
.address
= 0;
2658 khugepaged_scan
.mm_slot
= mm_slot
;
2660 spin_unlock(&khugepaged_mm_lock
);
2663 down_read(&mm
->mmap_sem
);
2664 if (unlikely(khugepaged_test_exit(mm
)))
2667 vma
= find_vma(mm
, khugepaged_scan
.address
);
2670 for (; vma
; vma
= vma
->vm_next
) {
2671 unsigned long hstart
, hend
;
2674 if (unlikely(khugepaged_test_exit(mm
))) {
2678 if (!hugepage_vma_check(vma
)) {
2683 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2684 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2687 if (khugepaged_scan
.address
> hend
)
2689 if (khugepaged_scan
.address
< hstart
)
2690 khugepaged_scan
.address
= hstart
;
2691 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2693 while (khugepaged_scan
.address
< hend
) {
2696 if (unlikely(khugepaged_test_exit(mm
)))
2697 goto breakouterloop
;
2699 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2700 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2702 ret
= khugepaged_scan_pmd(mm
, vma
,
2703 khugepaged_scan
.address
,
2705 /* move to next address */
2706 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2707 progress
+= HPAGE_PMD_NR
;
2709 /* we released mmap_sem so break loop */
2710 goto breakouterloop_mmap_sem
;
2711 if (progress
>= pages
)
2712 goto breakouterloop
;
2716 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
2717 breakouterloop_mmap_sem
:
2719 spin_lock(&khugepaged_mm_lock
);
2720 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2722 * Release the current mm_slot if this mm is about to die, or
2723 * if we scanned all vmas of this mm.
2725 if (khugepaged_test_exit(mm
) || !vma
) {
2727 * Make sure that if mm_users is reaching zero while
2728 * khugepaged runs here, khugepaged_exit will find
2729 * mm_slot not pointing to the exiting mm.
2731 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2732 khugepaged_scan
.mm_slot
= list_entry(
2733 mm_slot
->mm_node
.next
,
2734 struct mm_slot
, mm_node
);
2735 khugepaged_scan
.address
= 0;
2737 khugepaged_scan
.mm_slot
= NULL
;
2738 khugepaged_full_scans
++;
2741 collect_mm_slot(mm_slot
);
2747 static int khugepaged_has_work(void)
2749 return !list_empty(&khugepaged_scan
.mm_head
) &&
2750 khugepaged_enabled();
2753 static int khugepaged_wait_event(void)
2755 return !list_empty(&khugepaged_scan
.mm_head
) ||
2756 kthread_should_stop();
2759 static void khugepaged_do_scan(void)
2761 struct page
*hpage
= NULL
;
2762 unsigned int progress
= 0, pass_through_head
= 0;
2763 unsigned int pages
= khugepaged_pages_to_scan
;
2766 barrier(); /* write khugepaged_pages_to_scan to local stack */
2768 while (progress
< pages
) {
2769 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2774 if (unlikely(kthread_should_stop() || try_to_freeze()))
2777 spin_lock(&khugepaged_mm_lock
);
2778 if (!khugepaged_scan
.mm_slot
)
2779 pass_through_head
++;
2780 if (khugepaged_has_work() &&
2781 pass_through_head
< 2)
2782 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2786 spin_unlock(&khugepaged_mm_lock
);
2789 if (!IS_ERR_OR_NULL(hpage
))
2793 static bool khugepaged_should_wakeup(void)
2795 return kthread_should_stop() ||
2796 time_after_eq(jiffies
, khugepaged_sleep_expire
);
2799 static void khugepaged_wait_work(void)
2801 if (khugepaged_has_work()) {
2802 const unsigned long scan_sleep_jiffies
=
2803 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
);
2805 if (!scan_sleep_jiffies
)
2808 khugepaged_sleep_expire
= jiffies
+ scan_sleep_jiffies
;
2809 wait_event_freezable_timeout(khugepaged_wait
,
2810 khugepaged_should_wakeup(),
2811 scan_sleep_jiffies
);
2815 if (khugepaged_enabled())
2816 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2819 static int khugepaged(void *none
)
2821 struct mm_slot
*mm_slot
;
2824 set_user_nice(current
, MAX_NICE
);
2826 while (!kthread_should_stop()) {
2827 khugepaged_do_scan();
2828 khugepaged_wait_work();
2831 spin_lock(&khugepaged_mm_lock
);
2832 mm_slot
= khugepaged_scan
.mm_slot
;
2833 khugepaged_scan
.mm_slot
= NULL
;
2835 collect_mm_slot(mm_slot
);
2836 spin_unlock(&khugepaged_mm_lock
);
2840 static void __split_huge_zero_page_pmd(struct vm_area_struct
*vma
,
2841 unsigned long haddr
, pmd_t
*pmd
)
2843 struct mm_struct
*mm
= vma
->vm_mm
;
2848 /* leave pmd empty until pte is filled */
2849 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2851 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2852 pmd_populate(mm
, &_pmd
, pgtable
);
2854 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2856 entry
= pfn_pte(my_zero_pfn(haddr
), vma
->vm_page_prot
);
2857 entry
= pte_mkspecial(entry
);
2858 pte
= pte_offset_map(&_pmd
, haddr
);
2859 VM_BUG_ON(!pte_none(*pte
));
2860 set_pte_at(mm
, haddr
, pte
, entry
);
2863 smp_wmb(); /* make pte visible before pmd */
2864 pmd_populate(mm
, pmd
, pgtable
);
2865 put_huge_zero_page();
2868 static void __split_huge_pmd_locked(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2869 unsigned long haddr
, bool freeze
)
2871 struct mm_struct
*mm
= vma
->vm_mm
;
2875 bool young
, write
, dirty
;
2879 VM_BUG_ON(haddr
& ~HPAGE_PMD_MASK
);
2880 VM_BUG_ON_VMA(vma
->vm_start
> haddr
, vma
);
2881 VM_BUG_ON_VMA(vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
, vma
);
2882 VM_BUG_ON(!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
));
2884 count_vm_event(THP_SPLIT_PMD
);
2886 if (vma_is_dax(vma
)) {
2887 pmd_t _pmd
= pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2888 if (is_huge_zero_pmd(_pmd
))
2889 put_huge_zero_page();
2891 } else if (is_huge_zero_pmd(*pmd
)) {
2892 return __split_huge_zero_page_pmd(vma
, haddr
, pmd
);
2895 page
= pmd_page(*pmd
);
2896 VM_BUG_ON_PAGE(!page_count(page
), page
);
2897 page_ref_add(page
, HPAGE_PMD_NR
- 1);
2898 write
= pmd_write(*pmd
);
2899 young
= pmd_young(*pmd
);
2900 dirty
= pmd_dirty(*pmd
);
2902 pmdp_huge_split_prepare(vma
, haddr
, pmd
);
2903 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2904 pmd_populate(mm
, &_pmd
, pgtable
);
2906 for (i
= 0, addr
= haddr
; i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
) {
2909 * Note that NUMA hinting access restrictions are not
2910 * transferred to avoid any possibility of altering
2911 * permissions across VMAs.
2914 swp_entry_t swp_entry
;
2915 swp_entry
= make_migration_entry(page
+ i
, write
);
2916 entry
= swp_entry_to_pte(swp_entry
);
2918 entry
= mk_pte(page
+ i
, vma
->vm_page_prot
);
2919 entry
= maybe_mkwrite(entry
, vma
);
2921 entry
= pte_wrprotect(entry
);
2923 entry
= pte_mkold(entry
);
2926 SetPageDirty(page
+ i
);
2927 pte
= pte_offset_map(&_pmd
, addr
);
2928 BUG_ON(!pte_none(*pte
));
2929 set_pte_at(mm
, addr
, pte
, entry
);
2930 atomic_inc(&page
[i
]._mapcount
);
2935 * Set PG_double_map before dropping compound_mapcount to avoid
2936 * false-negative page_mapped().
2938 if (compound_mapcount(page
) > 1 && !TestSetPageDoubleMap(page
)) {
2939 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2940 atomic_inc(&page
[i
]._mapcount
);
2943 if (atomic_add_negative(-1, compound_mapcount_ptr(page
))) {
2944 /* Last compound_mapcount is gone. */
2945 __dec_zone_page_state(page
, NR_ANON_TRANSPARENT_HUGEPAGES
);
2946 if (TestClearPageDoubleMap(page
)) {
2947 /* No need in mapcount reference anymore */
2948 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2949 atomic_dec(&page
[i
]._mapcount
);
2953 smp_wmb(); /* make pte visible before pmd */
2955 * Up to this point the pmd is present and huge and userland has the
2956 * whole access to the hugepage during the split (which happens in
2957 * place). If we overwrite the pmd with the not-huge version pointing
2958 * to the pte here (which of course we could if all CPUs were bug
2959 * free), userland could trigger a small page size TLB miss on the
2960 * small sized TLB while the hugepage TLB entry is still established in
2961 * the huge TLB. Some CPU doesn't like that.
2962 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2963 * 383 on page 93. Intel should be safe but is also warns that it's
2964 * only safe if the permission and cache attributes of the two entries
2965 * loaded in the two TLB is identical (which should be the case here).
2966 * But it is generally safer to never allow small and huge TLB entries
2967 * for the same virtual address to be loaded simultaneously. So instead
2968 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2969 * current pmd notpresent (atomically because here the pmd_trans_huge
2970 * and pmd_trans_splitting must remain set at all times on the pmd
2971 * until the split is complete for this pmd), then we flush the SMP TLB
2972 * and finally we write the non-huge version of the pmd entry with
2975 pmdp_invalidate(vma
, haddr
, pmd
);
2976 pmd_populate(mm
, pmd
, pgtable
);
2979 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
2980 page_remove_rmap(page
+ i
, false);
2986 void __split_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2987 unsigned long address
, bool freeze
, struct page
*page
)
2990 struct mm_struct
*mm
= vma
->vm_mm
;
2991 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
2993 mmu_notifier_invalidate_range_start(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
2994 ptl
= pmd_lock(mm
, pmd
);
2997 * If caller asks to setup a migration entries, we need a page to check
2998 * pmd against. Otherwise we can end up replacing wrong page.
3000 VM_BUG_ON(freeze
&& !page
);
3001 if (page
&& page
!= pmd_page(*pmd
))
3004 if (pmd_trans_huge(*pmd
)) {
3005 page
= pmd_page(*pmd
);
3006 if (PageMlocked(page
))
3007 clear_page_mlock(page
);
3008 } else if (!pmd_devmap(*pmd
))
3010 __split_huge_pmd_locked(vma
, pmd
, haddr
, freeze
);
3013 mmu_notifier_invalidate_range_end(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
3016 void split_huge_pmd_address(struct vm_area_struct
*vma
, unsigned long address
,
3017 bool freeze
, struct page
*page
)
3023 pgd
= pgd_offset(vma
->vm_mm
, address
);
3024 if (!pgd_present(*pgd
))
3027 pud
= pud_offset(pgd
, address
);
3028 if (!pud_present(*pud
))
3031 pmd
= pmd_offset(pud
, address
);
3033 __split_huge_pmd(vma
, pmd
, address
, freeze
, page
);
3036 void vma_adjust_trans_huge(struct vm_area_struct
*vma
,
3037 unsigned long start
,
3042 * If the new start address isn't hpage aligned and it could
3043 * previously contain an hugepage: check if we need to split
3046 if (start
& ~HPAGE_PMD_MASK
&&
3047 (start
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3048 (start
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3049 split_huge_pmd_address(vma
, start
, false, NULL
);
3052 * If the new end address isn't hpage aligned and it could
3053 * previously contain an hugepage: check if we need to split
3056 if (end
& ~HPAGE_PMD_MASK
&&
3057 (end
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3058 (end
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3059 split_huge_pmd_address(vma
, end
, false, NULL
);
3062 * If we're also updating the vma->vm_next->vm_start, if the new
3063 * vm_next->vm_start isn't page aligned and it could previously
3064 * contain an hugepage: check if we need to split an huge pmd.
3066 if (adjust_next
> 0) {
3067 struct vm_area_struct
*next
= vma
->vm_next
;
3068 unsigned long nstart
= next
->vm_start
;
3069 nstart
+= adjust_next
<< PAGE_SHIFT
;
3070 if (nstart
& ~HPAGE_PMD_MASK
&&
3071 (nstart
& HPAGE_PMD_MASK
) >= next
->vm_start
&&
3072 (nstart
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= next
->vm_end
)
3073 split_huge_pmd_address(next
, nstart
, false, NULL
);
3077 static void freeze_page(struct page
*page
)
3079 enum ttu_flags ttu_flags
= TTU_MIGRATION
| TTU_IGNORE_MLOCK
|
3080 TTU_IGNORE_ACCESS
| TTU_RMAP_LOCKED
;
3083 VM_BUG_ON_PAGE(!PageHead(page
), page
);
3085 /* We only need TTU_SPLIT_HUGE_PMD once */
3086 ret
= try_to_unmap(page
, ttu_flags
| TTU_SPLIT_HUGE_PMD
);
3087 for (i
= 1; !ret
&& i
< HPAGE_PMD_NR
; i
++) {
3088 /* Cut short if the page is unmapped */
3089 if (page_count(page
) == 1)
3092 ret
= try_to_unmap(page
+ i
, ttu_flags
);
3097 static void unfreeze_page(struct page
*page
)
3101 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3102 remove_migration_ptes(page
+ i
, page
+ i
, true);
3105 static void __split_huge_page_tail(struct page
*head
, int tail
,
3106 struct lruvec
*lruvec
, struct list_head
*list
)
3108 struct page
*page_tail
= head
+ tail
;
3110 VM_BUG_ON_PAGE(atomic_read(&page_tail
->_mapcount
) != -1, page_tail
);
3111 VM_BUG_ON_PAGE(page_ref_count(page_tail
) != 0, page_tail
);
3114 * tail_page->_refcount is zero and not changing from under us. But
3115 * get_page_unless_zero() may be running from under us on the
3116 * tail_page. If we used atomic_set() below instead of atomic_inc(), we
3117 * would then run atomic_set() concurrently with
3118 * get_page_unless_zero(), and atomic_set() is implemented in C not
3119 * using locked ops. spin_unlock on x86 sometime uses locked ops
3120 * because of PPro errata 66, 92, so unless somebody can guarantee
3121 * atomic_set() here would be safe on all archs (and not only on x86),
3122 * it's safer to use atomic_inc().
3124 page_ref_inc(page_tail
);
3126 page_tail
->flags
&= ~PAGE_FLAGS_CHECK_AT_PREP
;
3127 page_tail
->flags
|= (head
->flags
&
3128 ((1L << PG_referenced
) |
3129 (1L << PG_swapbacked
) |
3130 (1L << PG_mlocked
) |
3131 (1L << PG_uptodate
) |
3134 (1L << PG_unevictable
) |
3138 * After clearing PageTail the gup refcount can be released.
3139 * Page flags also must be visible before we make the page non-compound.
3143 clear_compound_head(page_tail
);
3145 if (page_is_young(head
))
3146 set_page_young(page_tail
);
3147 if (page_is_idle(head
))
3148 set_page_idle(page_tail
);
3150 /* ->mapping in first tail page is compound_mapcount */
3151 VM_BUG_ON_PAGE(tail
> 2 && page_tail
->mapping
!= TAIL_MAPPING
,
3153 page_tail
->mapping
= head
->mapping
;
3155 page_tail
->index
= head
->index
+ tail
;
3156 page_cpupid_xchg_last(page_tail
, page_cpupid_last(head
));
3157 lru_add_page_tail(head
, page_tail
, lruvec
, list
);
3160 static void __split_huge_page(struct page
*page
, struct list_head
*list
)
3162 struct page
*head
= compound_head(page
);
3163 struct zone
*zone
= page_zone(head
);
3164 struct lruvec
*lruvec
;
3167 /* prevent PageLRU to go away from under us, and freeze lru stats */
3168 spin_lock_irq(&zone
->lru_lock
);
3169 lruvec
= mem_cgroup_page_lruvec(head
, zone
);
3171 /* complete memcg works before add pages to LRU */
3172 mem_cgroup_split_huge_fixup(head
);
3174 for (i
= HPAGE_PMD_NR
- 1; i
>= 1; i
--)
3175 __split_huge_page_tail(head
, i
, lruvec
, list
);
3177 ClearPageCompound(head
);
3178 spin_unlock_irq(&zone
->lru_lock
);
3180 unfreeze_page(head
);
3182 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3183 struct page
*subpage
= head
+ i
;
3184 if (subpage
== page
)
3186 unlock_page(subpage
);
3189 * Subpages may be freed if there wasn't any mapping
3190 * like if add_to_swap() is running on a lru page that
3191 * had its mapping zapped. And freeing these pages
3192 * requires taking the lru_lock so we do the put_page
3193 * of the tail pages after the split is complete.
3199 int total_mapcount(struct page
*page
)
3203 VM_BUG_ON_PAGE(PageTail(page
), page
);
3205 if (likely(!PageCompound(page
)))
3206 return atomic_read(&page
->_mapcount
) + 1;
3208 ret
= compound_mapcount(page
);
3211 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3212 ret
+= atomic_read(&page
[i
]._mapcount
) + 1;
3213 if (PageDoubleMap(page
))
3214 ret
-= HPAGE_PMD_NR
;
3219 * This calculates accurately how many mappings a transparent hugepage
3220 * has (unlike page_mapcount() which isn't fully accurate). This full
3221 * accuracy is primarily needed to know if copy-on-write faults can
3222 * reuse the page and change the mapping to read-write instead of
3223 * copying them. At the same time this returns the total_mapcount too.
3225 * The function returns the highest mapcount any one of the subpages
3226 * has. If the return value is one, even if different processes are
3227 * mapping different subpages of the transparent hugepage, they can
3228 * all reuse it, because each process is reusing a different subpage.
3230 * The total_mapcount is instead counting all virtual mappings of the
3231 * subpages. If the total_mapcount is equal to "one", it tells the
3232 * caller all mappings belong to the same "mm" and in turn the
3233 * anon_vma of the transparent hugepage can become the vma->anon_vma
3234 * local one as no other process may be mapping any of the subpages.
3236 * It would be more accurate to replace page_mapcount() with
3237 * page_trans_huge_mapcount(), however we only use
3238 * page_trans_huge_mapcount() in the copy-on-write faults where we
3239 * need full accuracy to avoid breaking page pinning, because
3240 * page_trans_huge_mapcount() is slower than page_mapcount().
3242 int page_trans_huge_mapcount(struct page
*page
, int *total_mapcount
)
3244 int i
, ret
, _total_mapcount
, mapcount
;
3246 /* hugetlbfs shouldn't call it */
3247 VM_BUG_ON_PAGE(PageHuge(page
), page
);
3249 if (likely(!PageTransCompound(page
))) {
3250 mapcount
= atomic_read(&page
->_mapcount
) + 1;
3252 *total_mapcount
= mapcount
;
3256 page
= compound_head(page
);
3258 _total_mapcount
= ret
= 0;
3259 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3260 mapcount
= atomic_read(&page
[i
]._mapcount
) + 1;
3261 ret
= max(ret
, mapcount
);
3262 _total_mapcount
+= mapcount
;
3264 if (PageDoubleMap(page
)) {
3266 _total_mapcount
-= HPAGE_PMD_NR
;
3268 mapcount
= compound_mapcount(page
);
3270 _total_mapcount
+= mapcount
;
3272 *total_mapcount
= _total_mapcount
;
3277 * This function splits huge page into normal pages. @page can point to any
3278 * subpage of huge page to split. Split doesn't change the position of @page.
3280 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3281 * The huge page must be locked.
3283 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3285 * Both head page and tail pages will inherit mapping, flags, and so on from
3288 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3289 * they are not mapped.
3291 * Returns 0 if the hugepage is split successfully.
3292 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3295 int split_huge_page_to_list(struct page
*page
, struct list_head
*list
)
3297 struct page
*head
= compound_head(page
);
3298 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(head
));
3299 struct anon_vma
*anon_vma
;
3300 int count
, mapcount
, ret
;
3302 unsigned long flags
;
3304 VM_BUG_ON_PAGE(is_huge_zero_page(page
), page
);
3305 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
3306 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
3307 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
3308 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
3311 * The caller does not necessarily hold an mmap_sem that would prevent
3312 * the anon_vma disappearing so we first we take a reference to it
3313 * and then lock the anon_vma for write. This is similar to
3314 * page_lock_anon_vma_read except the write lock is taken to serialise
3315 * against parallel split or collapse operations.
3317 anon_vma
= page_get_anon_vma(head
);
3322 anon_vma_lock_write(anon_vma
);
3325 * Racy check if we can split the page, before freeze_page() will
3328 if (total_mapcount(head
) != page_count(head
) - 1) {
3333 mlocked
= PageMlocked(page
);
3335 VM_BUG_ON_PAGE(compound_mapcount(head
), head
);
3337 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3341 /* Prevent deferred_split_scan() touching ->_refcount */
3342 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3343 count
= page_count(head
);
3344 mapcount
= total_mapcount(head
);
3345 if (!mapcount
&& count
== 1) {
3346 if (!list_empty(page_deferred_list(head
))) {
3347 pgdata
->split_queue_len
--;
3348 list_del(page_deferred_list(head
));
3350 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3351 __split_huge_page(page
, list
);
3353 } else if (IS_ENABLED(CONFIG_DEBUG_VM
) && mapcount
) {
3354 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3355 pr_alert("total_mapcount: %u, page_count(): %u\n",
3358 dump_page(head
, NULL
);
3359 dump_page(page
, "total_mapcount(head) > 0");
3362 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3363 unfreeze_page(head
);
3368 anon_vma_unlock_write(anon_vma
);
3369 put_anon_vma(anon_vma
);
3371 count_vm_event(!ret
? THP_SPLIT_PAGE
: THP_SPLIT_PAGE_FAILED
);
3375 void free_transhuge_page(struct page
*page
)
3377 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
3378 unsigned long flags
;
3380 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3381 if (!list_empty(page_deferred_list(page
))) {
3382 pgdata
->split_queue_len
--;
3383 list_del(page_deferred_list(page
));
3385 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3386 free_compound_page(page
);
3389 void deferred_split_huge_page(struct page
*page
)
3391 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
3392 unsigned long flags
;
3394 VM_BUG_ON_PAGE(!PageTransHuge(page
), page
);
3396 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3397 if (list_empty(page_deferred_list(page
))) {
3398 count_vm_event(THP_DEFERRED_SPLIT_PAGE
);
3399 list_add_tail(page_deferred_list(page
), &pgdata
->split_queue
);
3400 pgdata
->split_queue_len
++;
3402 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3405 static unsigned long deferred_split_count(struct shrinker
*shrink
,
3406 struct shrink_control
*sc
)
3408 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
3409 return ACCESS_ONCE(pgdata
->split_queue_len
);
3412 static unsigned long deferred_split_scan(struct shrinker
*shrink
,
3413 struct shrink_control
*sc
)
3415 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
3416 unsigned long flags
;
3417 LIST_HEAD(list
), *pos
, *next
;
3421 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3422 /* Take pin on all head pages to avoid freeing them under us */
3423 list_for_each_safe(pos
, next
, &pgdata
->split_queue
) {
3424 page
= list_entry((void *)pos
, struct page
, mapping
);
3425 page
= compound_head(page
);
3426 if (get_page_unless_zero(page
)) {
3427 list_move(page_deferred_list(page
), &list
);
3429 /* We lost race with put_compound_page() */
3430 list_del_init(page_deferred_list(page
));
3431 pgdata
->split_queue_len
--;
3433 if (!--sc
->nr_to_scan
)
3436 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3438 list_for_each_safe(pos
, next
, &list
) {
3439 page
= list_entry((void *)pos
, struct page
, mapping
);
3441 /* split_huge_page() removes page from list on success */
3442 if (!split_huge_page(page
))
3448 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3449 list_splice_tail(&list
, &pgdata
->split_queue
);
3450 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3453 * Stop shrinker if we didn't split any page, but the queue is empty.
3454 * This can happen if pages were freed under us.
3456 if (!split
&& list_empty(&pgdata
->split_queue
))
3461 static struct shrinker deferred_split_shrinker
= {
3462 .count_objects
= deferred_split_count
,
3463 .scan_objects
= deferred_split_scan
,
3464 .seeks
= DEFAULT_SEEKS
,
3465 .flags
= SHRINKER_NUMA_AWARE
,
3468 #ifdef CONFIG_DEBUG_FS
3469 static int split_huge_pages_set(void *data
, u64 val
)
3473 unsigned long pfn
, max_zone_pfn
;
3474 unsigned long total
= 0, split
= 0;
3479 for_each_populated_zone(zone
) {
3480 max_zone_pfn
= zone_end_pfn(zone
);
3481 for (pfn
= zone
->zone_start_pfn
; pfn
< max_zone_pfn
; pfn
++) {
3482 if (!pfn_valid(pfn
))
3485 page
= pfn_to_page(pfn
);
3486 if (!get_page_unless_zero(page
))
3489 if (zone
!= page_zone(page
))
3492 if (!PageHead(page
) || !PageAnon(page
) ||
3498 if (!split_huge_page(page
))
3506 pr_info("%lu of %lu THP split\n", split
, total
);
3510 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops
, NULL
, split_huge_pages_set
,
3513 static int __init
split_huge_pages_debugfs(void)
3517 ret
= debugfs_create_file("split_huge_pages", 0200, NULL
, NULL
,
3518 &split_huge_pages_fops
);
3520 pr_warn("Failed to create split_huge_pages in debugfs");
3523 late_initcall(split_huge_pages_debugfs
);