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 struct task_struct
*khugepaged_thread __read_mostly
;
93 static DEFINE_MUTEX(khugepaged_mutex
);
94 static DEFINE_SPINLOCK(khugepaged_mm_lock
);
95 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait
);
97 * default collapse hugepages if there is at least one pte mapped like
98 * it would have happened if the vma was large enough during page
101 static unsigned int khugepaged_max_ptes_none __read_mostly
;
103 static int khugepaged(void *none
);
104 static int khugepaged_slab_init(void);
105 static void khugepaged_slab_exit(void);
107 #define MM_SLOTS_HASH_BITS 10
108 static __read_mostly
DEFINE_HASHTABLE(mm_slots_hash
, MM_SLOTS_HASH_BITS
);
110 static struct kmem_cache
*mm_slot_cache __read_mostly
;
113 * struct mm_slot - hash lookup from mm to mm_slot
114 * @hash: hash collision list
115 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
116 * @mm: the mm that this information is valid for
119 struct hlist_node hash
;
120 struct list_head mm_node
;
121 struct mm_struct
*mm
;
125 * struct khugepaged_scan - cursor for scanning
126 * @mm_head: the head of the mm list to scan
127 * @mm_slot: the current mm_slot we are scanning
128 * @address: the next address inside that to be scanned
130 * There is only the one khugepaged_scan instance of this cursor structure.
132 struct khugepaged_scan
{
133 struct list_head mm_head
;
134 struct mm_slot
*mm_slot
;
135 unsigned long address
;
137 static struct khugepaged_scan khugepaged_scan
= {
138 .mm_head
= LIST_HEAD_INIT(khugepaged_scan
.mm_head
),
141 static struct shrinker deferred_split_shrinker
;
143 static void set_recommended_min_free_kbytes(void)
147 unsigned long recommended_min
;
149 for_each_populated_zone(zone
)
152 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
153 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
156 * Make sure that on average at least two pageblocks are almost free
157 * of another type, one for a migratetype to fall back to and a
158 * second to avoid subsequent fallbacks of other types There are 3
159 * MIGRATE_TYPES we care about.
161 recommended_min
+= pageblock_nr_pages
* nr_zones
*
162 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
164 /* don't ever allow to reserve more than 5% of the lowmem */
165 recommended_min
= min(recommended_min
,
166 (unsigned long) nr_free_buffer_pages() / 20);
167 recommended_min
<<= (PAGE_SHIFT
-10);
169 if (recommended_min
> min_free_kbytes
) {
170 if (user_min_free_kbytes
>= 0)
171 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
172 min_free_kbytes
, recommended_min
);
174 min_free_kbytes
= recommended_min
;
176 setup_per_zone_wmarks();
179 static int start_stop_khugepaged(void)
182 if (khugepaged_enabled()) {
183 if (!khugepaged_thread
)
184 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
186 if (IS_ERR(khugepaged_thread
)) {
187 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
188 err
= PTR_ERR(khugepaged_thread
);
189 khugepaged_thread
= NULL
;
193 if (!list_empty(&khugepaged_scan
.mm_head
))
194 wake_up_interruptible(&khugepaged_wait
);
196 set_recommended_min_free_kbytes();
197 } else if (khugepaged_thread
) {
198 kthread_stop(khugepaged_thread
);
199 khugepaged_thread
= NULL
;
205 static atomic_t huge_zero_refcount
;
206 struct page
*huge_zero_page __read_mostly
;
208 struct page
*get_huge_zero_page(void)
210 struct page
*zero_page
;
212 if (likely(atomic_inc_not_zero(&huge_zero_refcount
)))
213 return READ_ONCE(huge_zero_page
);
215 zero_page
= alloc_pages((GFP_TRANSHUGE
| __GFP_ZERO
) & ~__GFP_MOVABLE
,
218 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED
);
221 count_vm_event(THP_ZERO_PAGE_ALLOC
);
223 if (cmpxchg(&huge_zero_page
, NULL
, zero_page
)) {
225 __free_pages(zero_page
, compound_order(zero_page
));
229 /* We take additional reference here. It will be put back by shrinker */
230 atomic_set(&huge_zero_refcount
, 2);
232 return READ_ONCE(huge_zero_page
);
235 void put_huge_zero_page(void)
238 * Counter should never go to zero here. Only shrinker can put
241 BUG_ON(atomic_dec_and_test(&huge_zero_refcount
));
244 static unsigned long shrink_huge_zero_page_count(struct shrinker
*shrink
,
245 struct shrink_control
*sc
)
247 /* we can free zero page only if last reference remains */
248 return atomic_read(&huge_zero_refcount
) == 1 ? HPAGE_PMD_NR
: 0;
251 static unsigned long shrink_huge_zero_page_scan(struct shrinker
*shrink
,
252 struct shrink_control
*sc
)
254 if (atomic_cmpxchg(&huge_zero_refcount
, 1, 0) == 1) {
255 struct page
*zero_page
= xchg(&huge_zero_page
, NULL
);
256 BUG_ON(zero_page
== NULL
);
257 __free_pages(zero_page
, compound_order(zero_page
));
264 static struct shrinker huge_zero_page_shrinker
= {
265 .count_objects
= shrink_huge_zero_page_count
,
266 .scan_objects
= shrink_huge_zero_page_scan
,
267 .seeks
= DEFAULT_SEEKS
,
272 static ssize_t
triple_flag_store(struct kobject
*kobj
,
273 struct kobj_attribute
*attr
,
274 const char *buf
, size_t count
,
275 enum transparent_hugepage_flag enabled
,
276 enum transparent_hugepage_flag deferred
,
277 enum transparent_hugepage_flag req_madv
)
279 if (!memcmp("defer", buf
,
280 min(sizeof("defer")-1, count
))) {
281 if (enabled
== deferred
)
283 clear_bit(enabled
, &transparent_hugepage_flags
);
284 clear_bit(req_madv
, &transparent_hugepage_flags
);
285 set_bit(deferred
, &transparent_hugepage_flags
);
286 } else if (!memcmp("always", buf
,
287 min(sizeof("always")-1, count
))) {
288 clear_bit(deferred
, &transparent_hugepage_flags
);
289 clear_bit(req_madv
, &transparent_hugepage_flags
);
290 set_bit(enabled
, &transparent_hugepage_flags
);
291 } else if (!memcmp("madvise", buf
,
292 min(sizeof("madvise")-1, count
))) {
293 clear_bit(enabled
, &transparent_hugepage_flags
);
294 clear_bit(deferred
, &transparent_hugepage_flags
);
295 set_bit(req_madv
, &transparent_hugepage_flags
);
296 } else if (!memcmp("never", buf
,
297 min(sizeof("never")-1, count
))) {
298 clear_bit(enabled
, &transparent_hugepage_flags
);
299 clear_bit(req_madv
, &transparent_hugepage_flags
);
300 clear_bit(deferred
, &transparent_hugepage_flags
);
307 static ssize_t
enabled_show(struct kobject
*kobj
,
308 struct kobj_attribute
*attr
, char *buf
)
310 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG
, &transparent_hugepage_flags
))
311 return sprintf(buf
, "[always] madvise never\n");
312 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
, &transparent_hugepage_flags
))
313 return sprintf(buf
, "always [madvise] never\n");
315 return sprintf(buf
, "always madvise [never]\n");
318 static ssize_t
enabled_store(struct kobject
*kobj
,
319 struct kobj_attribute
*attr
,
320 const char *buf
, size_t count
)
324 ret
= triple_flag_store(kobj
, attr
, buf
, count
,
325 TRANSPARENT_HUGEPAGE_FLAG
,
326 TRANSPARENT_HUGEPAGE_FLAG
,
327 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
332 mutex_lock(&khugepaged_mutex
);
333 err
= start_stop_khugepaged();
334 mutex_unlock(&khugepaged_mutex
);
342 static struct kobj_attribute enabled_attr
=
343 __ATTR(enabled
, 0644, enabled_show
, enabled_store
);
345 static ssize_t
single_flag_show(struct kobject
*kobj
,
346 struct kobj_attribute
*attr
, char *buf
,
347 enum transparent_hugepage_flag flag
)
349 return sprintf(buf
, "%d\n",
350 !!test_bit(flag
, &transparent_hugepage_flags
));
353 static ssize_t
single_flag_store(struct kobject
*kobj
,
354 struct kobj_attribute
*attr
,
355 const char *buf
, size_t count
,
356 enum transparent_hugepage_flag flag
)
361 ret
= kstrtoul(buf
, 10, &value
);
368 set_bit(flag
, &transparent_hugepage_flags
);
370 clear_bit(flag
, &transparent_hugepage_flags
);
376 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
377 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
378 * memory just to allocate one more hugepage.
380 static ssize_t
defrag_show(struct kobject
*kobj
,
381 struct kobj_attribute
*attr
, char *buf
)
383 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
, &transparent_hugepage_flags
))
384 return sprintf(buf
, "[always] defer madvise never\n");
385 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
, &transparent_hugepage_flags
))
386 return sprintf(buf
, "always [defer] madvise never\n");
387 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
, &transparent_hugepage_flags
))
388 return sprintf(buf
, "always defer [madvise] never\n");
390 return sprintf(buf
, "always defer madvise [never]\n");
393 static ssize_t
defrag_store(struct kobject
*kobj
,
394 struct kobj_attribute
*attr
,
395 const char *buf
, size_t count
)
397 return triple_flag_store(kobj
, attr
, buf
, count
,
398 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
,
399 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
,
400 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
402 static struct kobj_attribute defrag_attr
=
403 __ATTR(defrag
, 0644, defrag_show
, defrag_store
);
405 static ssize_t
use_zero_page_show(struct kobject
*kobj
,
406 struct kobj_attribute
*attr
, char *buf
)
408 return single_flag_show(kobj
, attr
, buf
,
409 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
411 static ssize_t
use_zero_page_store(struct kobject
*kobj
,
412 struct kobj_attribute
*attr
, const char *buf
, size_t count
)
414 return single_flag_store(kobj
, attr
, buf
, count
,
415 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
417 static struct kobj_attribute use_zero_page_attr
=
418 __ATTR(use_zero_page
, 0644, use_zero_page_show
, use_zero_page_store
);
419 #ifdef CONFIG_DEBUG_VM
420 static ssize_t
debug_cow_show(struct kobject
*kobj
,
421 struct kobj_attribute
*attr
, char *buf
)
423 return single_flag_show(kobj
, attr
, buf
,
424 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
426 static ssize_t
debug_cow_store(struct kobject
*kobj
,
427 struct kobj_attribute
*attr
,
428 const char *buf
, size_t count
)
430 return single_flag_store(kobj
, attr
, buf
, count
,
431 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
433 static struct kobj_attribute debug_cow_attr
=
434 __ATTR(debug_cow
, 0644, debug_cow_show
, debug_cow_store
);
435 #endif /* CONFIG_DEBUG_VM */
437 static struct attribute
*hugepage_attr
[] = {
440 &use_zero_page_attr
.attr
,
441 #ifdef CONFIG_DEBUG_VM
442 &debug_cow_attr
.attr
,
447 static struct attribute_group hugepage_attr_group
= {
448 .attrs
= hugepage_attr
,
451 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
452 struct kobj_attribute
*attr
,
455 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
458 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
459 struct kobj_attribute
*attr
,
460 const char *buf
, size_t count
)
465 err
= kstrtoul(buf
, 10, &msecs
);
466 if (err
|| msecs
> UINT_MAX
)
469 khugepaged_scan_sleep_millisecs
= msecs
;
470 wake_up_interruptible(&khugepaged_wait
);
474 static struct kobj_attribute scan_sleep_millisecs_attr
=
475 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
476 scan_sleep_millisecs_store
);
478 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
479 struct kobj_attribute
*attr
,
482 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
485 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
486 struct kobj_attribute
*attr
,
487 const char *buf
, size_t count
)
492 err
= kstrtoul(buf
, 10, &msecs
);
493 if (err
|| msecs
> UINT_MAX
)
496 khugepaged_alloc_sleep_millisecs
= msecs
;
497 wake_up_interruptible(&khugepaged_wait
);
501 static struct kobj_attribute alloc_sleep_millisecs_attr
=
502 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
503 alloc_sleep_millisecs_store
);
505 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
506 struct kobj_attribute
*attr
,
509 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
511 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
512 struct kobj_attribute
*attr
,
513 const char *buf
, size_t count
)
518 err
= kstrtoul(buf
, 10, &pages
);
519 if (err
|| !pages
|| pages
> UINT_MAX
)
522 khugepaged_pages_to_scan
= pages
;
526 static struct kobj_attribute pages_to_scan_attr
=
527 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
528 pages_to_scan_store
);
530 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
531 struct kobj_attribute
*attr
,
534 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
536 static struct kobj_attribute pages_collapsed_attr
=
537 __ATTR_RO(pages_collapsed
);
539 static ssize_t
full_scans_show(struct kobject
*kobj
,
540 struct kobj_attribute
*attr
,
543 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
545 static struct kobj_attribute full_scans_attr
=
546 __ATTR_RO(full_scans
);
548 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
549 struct kobj_attribute
*attr
, char *buf
)
551 return single_flag_show(kobj
, attr
, buf
,
552 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
554 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
555 struct kobj_attribute
*attr
,
556 const char *buf
, size_t count
)
558 return single_flag_store(kobj
, attr
, buf
, count
,
559 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
561 static struct kobj_attribute khugepaged_defrag_attr
=
562 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
563 khugepaged_defrag_store
);
566 * max_ptes_none controls if khugepaged should collapse hugepages over
567 * any unmapped ptes in turn potentially increasing the memory
568 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
569 * reduce the available free memory in the system as it
570 * runs. Increasing max_ptes_none will instead potentially reduce the
571 * free memory in the system during the khugepaged scan.
573 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
574 struct kobj_attribute
*attr
,
577 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
579 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
580 struct kobj_attribute
*attr
,
581 const char *buf
, size_t count
)
584 unsigned long max_ptes_none
;
586 err
= kstrtoul(buf
, 10, &max_ptes_none
);
587 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
590 khugepaged_max_ptes_none
= max_ptes_none
;
594 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
595 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
596 khugepaged_max_ptes_none_store
);
598 static struct attribute
*khugepaged_attr
[] = {
599 &khugepaged_defrag_attr
.attr
,
600 &khugepaged_max_ptes_none_attr
.attr
,
601 &pages_to_scan_attr
.attr
,
602 &pages_collapsed_attr
.attr
,
603 &full_scans_attr
.attr
,
604 &scan_sleep_millisecs_attr
.attr
,
605 &alloc_sleep_millisecs_attr
.attr
,
609 static struct attribute_group khugepaged_attr_group
= {
610 .attrs
= khugepaged_attr
,
611 .name
= "khugepaged",
614 static int __init
hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
618 *hugepage_kobj
= kobject_create_and_add("transparent_hugepage", mm_kobj
);
619 if (unlikely(!*hugepage_kobj
)) {
620 pr_err("failed to create transparent hugepage kobject\n");
624 err
= sysfs_create_group(*hugepage_kobj
, &hugepage_attr_group
);
626 pr_err("failed to register transparent hugepage group\n");
630 err
= sysfs_create_group(*hugepage_kobj
, &khugepaged_attr_group
);
632 pr_err("failed to register transparent hugepage group\n");
633 goto remove_hp_group
;
639 sysfs_remove_group(*hugepage_kobj
, &hugepage_attr_group
);
641 kobject_put(*hugepage_kobj
);
645 static void __init
hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
647 sysfs_remove_group(hugepage_kobj
, &khugepaged_attr_group
);
648 sysfs_remove_group(hugepage_kobj
, &hugepage_attr_group
);
649 kobject_put(hugepage_kobj
);
652 static inline int hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
657 static inline void hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
660 #endif /* CONFIG_SYSFS */
662 static int __init
hugepage_init(void)
665 struct kobject
*hugepage_kobj
;
667 if (!has_transparent_hugepage()) {
668 transparent_hugepage_flags
= 0;
672 khugepaged_pages_to_scan
= HPAGE_PMD_NR
* 8;
673 khugepaged_max_ptes_none
= HPAGE_PMD_NR
- 1;
675 * hugepages can't be allocated by the buddy allocator
677 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER
>= MAX_ORDER
);
679 * we use page->mapping and page->index in second tail page
680 * as list_head: assuming THP order >= 2
682 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER
< 2);
684 err
= hugepage_init_sysfs(&hugepage_kobj
);
688 err
= khugepaged_slab_init();
692 err
= register_shrinker(&huge_zero_page_shrinker
);
694 goto err_hzp_shrinker
;
695 err
= register_shrinker(&deferred_split_shrinker
);
697 goto err_split_shrinker
;
700 * By default disable transparent hugepages on smaller systems,
701 * where the extra memory used could hurt more than TLB overhead
702 * is likely to save. The admin can still enable it through /sys.
704 if (totalram_pages
< (512 << (20 - PAGE_SHIFT
))) {
705 transparent_hugepage_flags
= 0;
709 err
= start_stop_khugepaged();
715 unregister_shrinker(&deferred_split_shrinker
);
717 unregister_shrinker(&huge_zero_page_shrinker
);
719 khugepaged_slab_exit();
721 hugepage_exit_sysfs(hugepage_kobj
);
725 subsys_initcall(hugepage_init
);
727 static int __init
setup_transparent_hugepage(char *str
)
732 if (!strcmp(str
, "always")) {
733 set_bit(TRANSPARENT_HUGEPAGE_FLAG
,
734 &transparent_hugepage_flags
);
735 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
736 &transparent_hugepage_flags
);
738 } else if (!strcmp(str
, "madvise")) {
739 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
740 &transparent_hugepage_flags
);
741 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
742 &transparent_hugepage_flags
);
744 } else if (!strcmp(str
, "never")) {
745 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
746 &transparent_hugepage_flags
);
747 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
748 &transparent_hugepage_flags
);
753 pr_warn("transparent_hugepage= cannot parse, ignored\n");
756 __setup("transparent_hugepage=", setup_transparent_hugepage
);
758 pmd_t
maybe_pmd_mkwrite(pmd_t pmd
, struct vm_area_struct
*vma
)
760 if (likely(vma
->vm_flags
& VM_WRITE
))
761 pmd
= pmd_mkwrite(pmd
);
765 static inline pmd_t
mk_huge_pmd(struct page
*page
, pgprot_t prot
)
768 entry
= mk_pmd(page
, prot
);
769 entry
= pmd_mkhuge(entry
);
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
;
1017 static void touch_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
1023 * We should set the dirty bit only for FOLL_WRITE but for now
1024 * the dirty bit in the pmd is meaningless. And if the dirty
1025 * bit will become meaningful and we'll only set it with
1026 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
1027 * set the young bit, instead of the current set_pmd_at.
1029 _pmd
= pmd_mkyoung(pmd_mkdirty(*pmd
));
1030 if (pmdp_set_access_flags(vma
, addr
& HPAGE_PMD_MASK
,
1032 update_mmu_cache_pmd(vma
, addr
, pmd
);
1035 struct page
*follow_devmap_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
1036 pmd_t
*pmd
, int flags
)
1038 unsigned long pfn
= pmd_pfn(*pmd
);
1039 struct mm_struct
*mm
= vma
->vm_mm
;
1040 struct dev_pagemap
*pgmap
;
1043 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1045 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1048 if (pmd_present(*pmd
) && pmd_devmap(*pmd
))
1053 if (flags
& FOLL_TOUCH
)
1054 touch_pmd(vma
, addr
, pmd
);
1057 * device mapped pages can only be returned if the
1058 * caller will manage the page reference count.
1060 if (!(flags
& FOLL_GET
))
1061 return ERR_PTR(-EEXIST
);
1063 pfn
+= (addr
& ~PMD_MASK
) >> PAGE_SHIFT
;
1064 pgmap
= get_dev_pagemap(pfn
, NULL
);
1066 return ERR_PTR(-EFAULT
);
1067 page
= pfn_to_page(pfn
);
1069 put_dev_pagemap(pgmap
);
1074 int copy_huge_pmd(struct mm_struct
*dst_mm
, struct mm_struct
*src_mm
,
1075 pmd_t
*dst_pmd
, pmd_t
*src_pmd
, unsigned long addr
,
1076 struct vm_area_struct
*vma
)
1078 spinlock_t
*dst_ptl
, *src_ptl
;
1079 struct page
*src_page
;
1081 pgtable_t pgtable
= NULL
;
1084 if (!vma_is_dax(vma
)) {
1086 pgtable
= pte_alloc_one(dst_mm
, addr
);
1087 if (unlikely(!pgtable
))
1091 dst_ptl
= pmd_lock(dst_mm
, dst_pmd
);
1092 src_ptl
= pmd_lockptr(src_mm
, src_pmd
);
1093 spin_lock_nested(src_ptl
, SINGLE_DEPTH_NESTING
);
1097 if (unlikely(!pmd_trans_huge(pmd
) && !pmd_devmap(pmd
))) {
1098 pte_free(dst_mm
, pgtable
);
1102 * When page table lock is held, the huge zero pmd should not be
1103 * under splitting since we don't split the page itself, only pmd to
1106 if (is_huge_zero_pmd(pmd
)) {
1107 struct page
*zero_page
;
1109 * get_huge_zero_page() will never allocate a new page here,
1110 * since we already have a zero page to copy. It just takes a
1113 zero_page
= get_huge_zero_page();
1114 set_huge_zero_page(pgtable
, dst_mm
, vma
, addr
, dst_pmd
,
1120 if (!vma_is_dax(vma
)) {
1121 /* thp accounting separate from pmd_devmap accounting */
1122 src_page
= pmd_page(pmd
);
1123 VM_BUG_ON_PAGE(!PageHead(src_page
), src_page
);
1125 page_dup_rmap(src_page
, true);
1126 add_mm_counter(dst_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1127 atomic_long_inc(&dst_mm
->nr_ptes
);
1128 pgtable_trans_huge_deposit(dst_mm
, dst_pmd
, pgtable
);
1131 pmdp_set_wrprotect(src_mm
, addr
, src_pmd
);
1132 pmd
= pmd_mkold(pmd_wrprotect(pmd
));
1133 set_pmd_at(dst_mm
, addr
, dst_pmd
, pmd
);
1137 spin_unlock(src_ptl
);
1138 spin_unlock(dst_ptl
);
1143 void huge_pmd_set_accessed(struct mm_struct
*mm
,
1144 struct vm_area_struct
*vma
,
1145 unsigned long address
,
1146 pmd_t
*pmd
, pmd_t orig_pmd
,
1151 unsigned long haddr
;
1153 ptl
= pmd_lock(mm
, pmd
);
1154 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1157 entry
= pmd_mkyoung(orig_pmd
);
1158 haddr
= address
& HPAGE_PMD_MASK
;
1159 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, dirty
))
1160 update_mmu_cache_pmd(vma
, address
, pmd
);
1166 static int do_huge_pmd_wp_page_fallback(struct mm_struct
*mm
,
1167 struct vm_area_struct
*vma
,
1168 unsigned long address
,
1169 pmd_t
*pmd
, pmd_t orig_pmd
,
1171 unsigned long haddr
)
1173 struct mem_cgroup
*memcg
;
1178 struct page
**pages
;
1179 unsigned long mmun_start
; /* For mmu_notifiers */
1180 unsigned long mmun_end
; /* For mmu_notifiers */
1182 pages
= kmalloc(sizeof(struct page
*) * HPAGE_PMD_NR
,
1184 if (unlikely(!pages
)) {
1185 ret
|= VM_FAULT_OOM
;
1189 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1190 pages
[i
] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE
|
1192 vma
, address
, page_to_nid(page
));
1193 if (unlikely(!pages
[i
] ||
1194 mem_cgroup_try_charge(pages
[i
], mm
, GFP_KERNEL
,
1199 memcg
= (void *)page_private(pages
[i
]);
1200 set_page_private(pages
[i
], 0);
1201 mem_cgroup_cancel_charge(pages
[i
], memcg
,
1206 ret
|= VM_FAULT_OOM
;
1209 set_page_private(pages
[i
], (unsigned long)memcg
);
1212 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1213 copy_user_highpage(pages
[i
], page
+ i
,
1214 haddr
+ PAGE_SIZE
* i
, vma
);
1215 __SetPageUptodate(pages
[i
]);
1220 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1221 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1223 ptl
= pmd_lock(mm
, pmd
);
1224 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1225 goto out_free_pages
;
1226 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1228 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1229 /* leave pmd empty until pte is filled */
1231 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
1232 pmd_populate(mm
, &_pmd
, pgtable
);
1234 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
1236 entry
= mk_pte(pages
[i
], vma
->vm_page_prot
);
1237 entry
= maybe_mkwrite(pte_mkdirty(entry
), vma
);
1238 memcg
= (void *)page_private(pages
[i
]);
1239 set_page_private(pages
[i
], 0);
1240 page_add_new_anon_rmap(pages
[i
], vma
, haddr
, false);
1241 mem_cgroup_commit_charge(pages
[i
], memcg
, false, false);
1242 lru_cache_add_active_or_unevictable(pages
[i
], vma
);
1243 pte
= pte_offset_map(&_pmd
, haddr
);
1244 VM_BUG_ON(!pte_none(*pte
));
1245 set_pte_at(mm
, haddr
, pte
, entry
);
1250 smp_wmb(); /* make pte visible before pmd */
1251 pmd_populate(mm
, pmd
, pgtable
);
1252 page_remove_rmap(page
, true);
1255 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1257 ret
|= VM_FAULT_WRITE
;
1265 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1266 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1267 memcg
= (void *)page_private(pages
[i
]);
1268 set_page_private(pages
[i
], 0);
1269 mem_cgroup_cancel_charge(pages
[i
], memcg
, false);
1276 int do_huge_pmd_wp_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1277 unsigned long address
, pmd_t
*pmd
, pmd_t orig_pmd
)
1281 struct page
*page
= NULL
, *new_page
;
1282 struct mem_cgroup
*memcg
;
1283 unsigned long haddr
;
1284 unsigned long mmun_start
; /* For mmu_notifiers */
1285 unsigned long mmun_end
; /* For mmu_notifiers */
1286 gfp_t huge_gfp
; /* for allocation and charge */
1288 ptl
= pmd_lockptr(mm
, pmd
);
1289 VM_BUG_ON_VMA(!vma
->anon_vma
, vma
);
1290 haddr
= address
& HPAGE_PMD_MASK
;
1291 if (is_huge_zero_pmd(orig_pmd
))
1294 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1297 page
= pmd_page(orig_pmd
);
1298 VM_BUG_ON_PAGE(!PageCompound(page
) || !PageHead(page
), page
);
1300 * We can only reuse the page if nobody else maps the huge page or it's
1303 if (page_trans_huge_mapcount(page
, NULL
) == 1) {
1305 entry
= pmd_mkyoung(orig_pmd
);
1306 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1307 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, 1))
1308 update_mmu_cache_pmd(vma
, address
, pmd
);
1309 ret
|= VM_FAULT_WRITE
;
1315 if (transparent_hugepage_enabled(vma
) &&
1316 !transparent_hugepage_debug_cow()) {
1317 huge_gfp
= alloc_hugepage_direct_gfpmask(vma
);
1318 new_page
= alloc_hugepage_vma(huge_gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
1322 if (likely(new_page
)) {
1323 prep_transhuge_page(new_page
);
1326 split_huge_pmd(vma
, pmd
, address
);
1327 ret
|= VM_FAULT_FALLBACK
;
1329 ret
= do_huge_pmd_wp_page_fallback(mm
, vma
, address
,
1330 pmd
, orig_pmd
, page
, haddr
);
1331 if (ret
& VM_FAULT_OOM
) {
1332 split_huge_pmd(vma
, pmd
, address
);
1333 ret
|= VM_FAULT_FALLBACK
;
1337 count_vm_event(THP_FAULT_FALLBACK
);
1341 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, huge_gfp
, &memcg
,
1345 split_huge_pmd(vma
, pmd
, address
);
1348 split_huge_pmd(vma
, pmd
, address
);
1349 ret
|= VM_FAULT_FALLBACK
;
1350 count_vm_event(THP_FAULT_FALLBACK
);
1354 count_vm_event(THP_FAULT_ALLOC
);
1357 clear_huge_page(new_page
, haddr
, HPAGE_PMD_NR
);
1359 copy_user_huge_page(new_page
, page
, haddr
, vma
, HPAGE_PMD_NR
);
1360 __SetPageUptodate(new_page
);
1363 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1364 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1369 if (unlikely(!pmd_same(*pmd
, orig_pmd
))) {
1371 mem_cgroup_cancel_charge(new_page
, memcg
, true);
1376 entry
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1377 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1378 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1379 page_add_new_anon_rmap(new_page
, vma
, haddr
, true);
1380 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
1381 lru_cache_add_active_or_unevictable(new_page
, vma
);
1382 set_pmd_at(mm
, haddr
, pmd
, entry
);
1383 update_mmu_cache_pmd(vma
, address
, pmd
);
1385 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1386 put_huge_zero_page();
1388 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1389 page_remove_rmap(page
, true);
1392 ret
|= VM_FAULT_WRITE
;
1396 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1404 struct page
*follow_trans_huge_pmd(struct vm_area_struct
*vma
,
1409 struct mm_struct
*mm
= vma
->vm_mm
;
1410 struct page
*page
= NULL
;
1412 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1414 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1417 /* Avoid dumping huge zero page */
1418 if ((flags
& FOLL_DUMP
) && is_huge_zero_pmd(*pmd
))
1419 return ERR_PTR(-EFAULT
);
1421 /* Full NUMA hinting faults to serialise migration in fault paths */
1422 if ((flags
& FOLL_NUMA
) && pmd_protnone(*pmd
))
1425 page
= pmd_page(*pmd
);
1426 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1427 if (flags
& FOLL_TOUCH
)
1428 touch_pmd(vma
, addr
, pmd
);
1429 if ((flags
& FOLL_MLOCK
) && (vma
->vm_flags
& VM_LOCKED
)) {
1431 * We don't mlock() pte-mapped THPs. This way we can avoid
1432 * leaking mlocked pages into non-VM_LOCKED VMAs.
1434 * In most cases the pmd is the only mapping of the page as we
1435 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1436 * writable private mappings in populate_vma_page_range().
1438 * The only scenario when we have the page shared here is if we
1439 * mlocking read-only mapping shared over fork(). We skip
1440 * mlocking such pages.
1442 if (compound_mapcount(page
) == 1 && !PageDoubleMap(page
) &&
1443 page
->mapping
&& trylock_page(page
)) {
1446 mlock_vma_page(page
);
1450 page
+= (addr
& ~HPAGE_PMD_MASK
) >> PAGE_SHIFT
;
1451 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
1452 if (flags
& FOLL_GET
)
1459 /* NUMA hinting page fault entry point for trans huge pmds */
1460 int do_huge_pmd_numa_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1461 unsigned long addr
, pmd_t pmd
, pmd_t
*pmdp
)
1464 struct anon_vma
*anon_vma
= NULL
;
1466 unsigned long haddr
= addr
& HPAGE_PMD_MASK
;
1467 int page_nid
= -1, this_nid
= numa_node_id();
1468 int target_nid
, last_cpupid
= -1;
1470 bool migrated
= false;
1474 /* A PROT_NONE fault should not end up here */
1475 BUG_ON(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)));
1477 ptl
= pmd_lock(mm
, pmdp
);
1478 if (unlikely(!pmd_same(pmd
, *pmdp
)))
1482 * If there are potential migrations, wait for completion and retry
1483 * without disrupting NUMA hinting information. Do not relock and
1484 * check_same as the page may no longer be mapped.
1486 if (unlikely(pmd_trans_migrating(*pmdp
))) {
1487 page
= pmd_page(*pmdp
);
1489 wait_on_page_locked(page
);
1493 page
= pmd_page(pmd
);
1494 BUG_ON(is_huge_zero_page(page
));
1495 page_nid
= page_to_nid(page
);
1496 last_cpupid
= page_cpupid_last(page
);
1497 count_vm_numa_event(NUMA_HINT_FAULTS
);
1498 if (page_nid
== this_nid
) {
1499 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL
);
1500 flags
|= TNF_FAULT_LOCAL
;
1503 /* See similar comment in do_numa_page for explanation */
1504 if (!(vma
->vm_flags
& VM_WRITE
))
1505 flags
|= TNF_NO_GROUP
;
1508 * Acquire the page lock to serialise THP migrations but avoid dropping
1509 * page_table_lock if at all possible
1511 page_locked
= trylock_page(page
);
1512 target_nid
= mpol_misplaced(page
, vma
, haddr
);
1513 if (target_nid
== -1) {
1514 /* If the page was locked, there are no parallel migrations */
1519 /* Migration could have started since the pmd_trans_migrating check */
1522 wait_on_page_locked(page
);
1528 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1529 * to serialises splits
1533 anon_vma
= page_lock_anon_vma_read(page
);
1535 /* Confirm the PMD did not change while page_table_lock was released */
1537 if (unlikely(!pmd_same(pmd
, *pmdp
))) {
1544 /* Bail if we fail to protect against THP splits for any reason */
1545 if (unlikely(!anon_vma
)) {
1552 * Migrate the THP to the requested node, returns with page unlocked
1553 * and access rights restored.
1556 migrated
= migrate_misplaced_transhuge_page(mm
, vma
,
1557 pmdp
, pmd
, addr
, page
, target_nid
);
1559 flags
|= TNF_MIGRATED
;
1560 page_nid
= target_nid
;
1562 flags
|= TNF_MIGRATE_FAIL
;
1566 BUG_ON(!PageLocked(page
));
1567 was_writable
= pmd_write(pmd
);
1568 pmd
= pmd_modify(pmd
, vma
->vm_page_prot
);
1569 pmd
= pmd_mkyoung(pmd
);
1571 pmd
= pmd_mkwrite(pmd
);
1572 set_pmd_at(mm
, haddr
, pmdp
, pmd
);
1573 update_mmu_cache_pmd(vma
, addr
, pmdp
);
1580 page_unlock_anon_vma_read(anon_vma
);
1583 task_numa_fault(last_cpupid
, page_nid
, HPAGE_PMD_NR
, flags
);
1588 int madvise_free_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1589 pmd_t
*pmd
, unsigned long addr
, unsigned long next
)
1595 struct mm_struct
*mm
= tlb
->mm
;
1598 ptl
= pmd_trans_huge_lock(pmd
, vma
);
1603 if (is_huge_zero_pmd(orig_pmd
)) {
1608 page
= pmd_page(orig_pmd
);
1610 * If other processes are mapping this page, we couldn't discard
1611 * the page unless they all do MADV_FREE so let's skip the page.
1613 if (page_mapcount(page
) != 1)
1616 if (!trylock_page(page
))
1620 * If user want to discard part-pages of THP, split it so MADV_FREE
1621 * will deactivate only them.
1623 if (next
- addr
!= HPAGE_PMD_SIZE
) {
1626 if (split_huge_page(page
)) {
1637 if (PageDirty(page
))
1638 ClearPageDirty(page
);
1641 if (PageActive(page
))
1642 deactivate_page(page
);
1644 if (pmd_young(orig_pmd
) || pmd_dirty(orig_pmd
)) {
1645 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1647 orig_pmd
= pmd_mkold(orig_pmd
);
1648 orig_pmd
= pmd_mkclean(orig_pmd
);
1650 set_pmd_at(mm
, addr
, pmd
, orig_pmd
);
1651 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1660 int zap_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1661 pmd_t
*pmd
, unsigned long addr
)
1666 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1670 * For architectures like ppc64 we look at deposited pgtable
1671 * when calling pmdp_huge_get_and_clear. So do the
1672 * pgtable_trans_huge_withdraw after finishing pmdp related
1675 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1677 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1678 if (vma_is_dax(vma
)) {
1680 if (is_huge_zero_pmd(orig_pmd
))
1681 tlb_remove_page(tlb
, pmd_page(orig_pmd
));
1682 } else if (is_huge_zero_pmd(orig_pmd
)) {
1683 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1684 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1686 tlb_remove_page(tlb
, pmd_page(orig_pmd
));
1688 struct page
*page
= pmd_page(orig_pmd
);
1689 page_remove_rmap(page
, true);
1690 VM_BUG_ON_PAGE(page_mapcount(page
) < 0, page
);
1691 add_mm_counter(tlb
->mm
, MM_ANONPAGES
, -HPAGE_PMD_NR
);
1692 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1693 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1694 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1696 tlb_remove_page(tlb
, page
);
1701 bool move_huge_pmd(struct vm_area_struct
*vma
, struct vm_area_struct
*new_vma
,
1702 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
;
1709 struct mm_struct
*mm
= vma
->vm_mm
;
1711 if ((old_addr
& ~HPAGE_PMD_MASK
) ||
1712 (new_addr
& ~HPAGE_PMD_MASK
) ||
1713 old_end
- old_addr
< HPAGE_PMD_SIZE
||
1714 (new_vma
->vm_flags
& VM_NOHUGEPAGE
))
1718 * The destination pmd shouldn't be established, free_pgtables()
1719 * should have release it.
1721 if (WARN_ON(!pmd_none(*new_pmd
))) {
1722 VM_BUG_ON(pmd_trans_huge(*new_pmd
));
1727 * We don't have to worry about the ordering of src and dst
1728 * ptlocks because exclusive mmap_sem prevents deadlock.
1730 old_ptl
= __pmd_trans_huge_lock(old_pmd
, vma
);
1732 new_ptl
= pmd_lockptr(mm
, new_pmd
);
1733 if (new_ptl
!= old_ptl
)
1734 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
1735 pmd
= pmdp_huge_get_and_clear(mm
, old_addr
, old_pmd
);
1736 VM_BUG_ON(!pmd_none(*new_pmd
));
1738 if (pmd_move_must_withdraw(new_ptl
, old_ptl
) &&
1739 vma_is_anonymous(vma
)) {
1741 pgtable
= pgtable_trans_huge_withdraw(mm
, old_pmd
);
1742 pgtable_trans_huge_deposit(mm
, new_pmd
, pgtable
);
1744 set_pmd_at(mm
, new_addr
, new_pmd
, pmd_mksoft_dirty(pmd
));
1745 if (new_ptl
!= old_ptl
)
1746 spin_unlock(new_ptl
);
1747 spin_unlock(old_ptl
);
1755 * - 0 if PMD could not be locked
1756 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1757 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1759 int change_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1760 unsigned long addr
, pgprot_t newprot
, int prot_numa
)
1762 struct mm_struct
*mm
= vma
->vm_mm
;
1766 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1769 bool preserve_write
= prot_numa
&& pmd_write(*pmd
);
1773 * Avoid trapping faults against the zero page. The read-only
1774 * data is likely to be read-cached on the local CPU and
1775 * local/remote hits to the zero page are not interesting.
1777 if (prot_numa
&& is_huge_zero_pmd(*pmd
)) {
1782 if (!prot_numa
|| !pmd_protnone(*pmd
)) {
1783 entry
= pmdp_huge_get_and_clear_notify(mm
, addr
, pmd
);
1784 entry
= pmd_modify(entry
, newprot
);
1786 entry
= pmd_mkwrite(entry
);
1788 set_pmd_at(mm
, addr
, pmd
, entry
);
1789 BUG_ON(!preserve_write
&& pmd_write(entry
));
1798 * Returns true if a given pmd maps a thp, false otherwise.
1800 * Note that if it returns true, this routine returns without unlocking page
1801 * table lock. So callers must unlock it.
1803 spinlock_t
*__pmd_trans_huge_lock(pmd_t
*pmd
, struct vm_area_struct
*vma
)
1806 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1807 if (likely(pmd_trans_huge(*pmd
) || pmd_devmap(*pmd
)))
1813 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1815 int hugepage_madvise(struct vm_area_struct
*vma
,
1816 unsigned long *vm_flags
, int advice
)
1822 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1823 * can't handle this properly after s390_enable_sie, so we simply
1824 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1826 if (mm_has_pgste(vma
->vm_mm
))
1830 * Be somewhat over-protective like KSM for now!
1832 if (*vm_flags
& VM_NO_THP
)
1834 *vm_flags
&= ~VM_NOHUGEPAGE
;
1835 *vm_flags
|= VM_HUGEPAGE
;
1837 * If the vma become good for khugepaged to scan,
1838 * register it here without waiting a page fault that
1839 * may not happen any time soon.
1841 if (unlikely(khugepaged_enter_vma_merge(vma
, *vm_flags
)))
1844 case MADV_NOHUGEPAGE
:
1846 * Be somewhat over-protective like KSM for now!
1848 if (*vm_flags
& VM_NO_THP
)
1850 *vm_flags
&= ~VM_HUGEPAGE
;
1851 *vm_flags
|= VM_NOHUGEPAGE
;
1853 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1854 * this vma even if we leave the mm registered in khugepaged if
1855 * it got registered before VM_NOHUGEPAGE was set.
1863 static int __init
khugepaged_slab_init(void)
1865 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
1866 sizeof(struct mm_slot
),
1867 __alignof__(struct mm_slot
), 0, NULL
);
1874 static void __init
khugepaged_slab_exit(void)
1876 kmem_cache_destroy(mm_slot_cache
);
1879 static inline struct mm_slot
*alloc_mm_slot(void)
1881 if (!mm_slot_cache
) /* initialization failed */
1883 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
1886 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
1888 kmem_cache_free(mm_slot_cache
, mm_slot
);
1891 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
1893 struct mm_slot
*mm_slot
;
1895 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
1896 if (mm
== mm_slot
->mm
)
1902 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
1903 struct mm_slot
*mm_slot
)
1906 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
1909 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
1911 return atomic_read(&mm
->mm_users
) == 0;
1914 int __khugepaged_enter(struct mm_struct
*mm
)
1916 struct mm_slot
*mm_slot
;
1919 mm_slot
= alloc_mm_slot();
1923 /* __khugepaged_exit() must not run from under us */
1924 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
1925 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
1926 free_mm_slot(mm_slot
);
1930 spin_lock(&khugepaged_mm_lock
);
1931 insert_to_mm_slots_hash(mm
, mm_slot
);
1933 * Insert just behind the scanning cursor, to let the area settle
1936 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
1937 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
1938 spin_unlock(&khugepaged_mm_lock
);
1940 atomic_inc(&mm
->mm_count
);
1942 wake_up_interruptible(&khugepaged_wait
);
1947 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
1948 unsigned long vm_flags
)
1950 unsigned long hstart
, hend
;
1953 * Not yet faulted in so we will register later in the
1954 * page fault if needed.
1957 if (vma
->vm_ops
|| (vm_flags
& VM_NO_THP
))
1958 /* khugepaged not yet working on file or special mappings */
1960 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1961 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1963 return khugepaged_enter(vma
, vm_flags
);
1967 void __khugepaged_exit(struct mm_struct
*mm
)
1969 struct mm_slot
*mm_slot
;
1972 spin_lock(&khugepaged_mm_lock
);
1973 mm_slot
= get_mm_slot(mm
);
1974 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
1975 hash_del(&mm_slot
->hash
);
1976 list_del(&mm_slot
->mm_node
);
1979 spin_unlock(&khugepaged_mm_lock
);
1982 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
1983 free_mm_slot(mm_slot
);
1985 } else if (mm_slot
) {
1987 * This is required to serialize against
1988 * khugepaged_test_exit() (which is guaranteed to run
1989 * under mmap sem read mode). Stop here (after we
1990 * return all pagetables will be destroyed) until
1991 * khugepaged has finished working on the pagetables
1992 * under the mmap_sem.
1994 down_write(&mm
->mmap_sem
);
1995 up_write(&mm
->mmap_sem
);
1999 static void release_pte_page(struct page
*page
)
2001 /* 0 stands for page_is_file_cache(page) == false */
2002 dec_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
2004 putback_lru_page(page
);
2007 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
)
2009 while (--_pte
>= pte
) {
2010 pte_t pteval
= *_pte
;
2011 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)))
2012 release_pte_page(pte_page(pteval
));
2016 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
2017 unsigned long address
,
2020 struct page
*page
= NULL
;
2022 int none_or_zero
= 0, result
= 0;
2023 bool referenced
= false, writable
= false;
2025 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2026 _pte
++, address
+= PAGE_SIZE
) {
2027 pte_t pteval
= *_pte
;
2028 if (pte_none(pteval
) || (pte_present(pteval
) &&
2029 is_zero_pfn(pte_pfn(pteval
)))) {
2030 if (!userfaultfd_armed(vma
) &&
2031 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2034 result
= SCAN_EXCEED_NONE_PTE
;
2038 if (!pte_present(pteval
)) {
2039 result
= SCAN_PTE_NON_PRESENT
;
2042 page
= vm_normal_page(vma
, address
, pteval
);
2043 if (unlikely(!page
)) {
2044 result
= SCAN_PAGE_NULL
;
2048 VM_BUG_ON_PAGE(PageCompound(page
), page
);
2049 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
2050 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
2053 * We can do it before isolate_lru_page because the
2054 * page can't be freed from under us. NOTE: PG_lock
2055 * is needed to serialize against split_huge_page
2056 * when invoked from the VM.
2058 if (!trylock_page(page
)) {
2059 result
= SCAN_PAGE_LOCK
;
2064 * cannot use mapcount: can't collapse if there's a gup pin.
2065 * The page must only be referenced by the scanned process
2066 * and page swap cache.
2068 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2070 result
= SCAN_PAGE_COUNT
;
2073 if (pte_write(pteval
)) {
2076 if (PageSwapCache(page
) &&
2077 !reuse_swap_page(page
, NULL
)) {
2079 result
= SCAN_SWAP_CACHE_PAGE
;
2083 * Page is not in the swap cache. It can be collapsed
2089 * Isolate the page to avoid collapsing an hugepage
2090 * currently in use by the VM.
2092 if (isolate_lru_page(page
)) {
2094 result
= SCAN_DEL_PAGE_LRU
;
2097 /* 0 stands for page_is_file_cache(page) == false */
2098 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
2099 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
2100 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2102 /* If there is no mapped pte young don't collapse the page */
2103 if (pte_young(pteval
) ||
2104 page_is_young(page
) || PageReferenced(page
) ||
2105 mmu_notifier_test_young(vma
->vm_mm
, address
))
2108 if (likely(writable
)) {
2109 if (likely(referenced
)) {
2110 result
= SCAN_SUCCEED
;
2111 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
2112 referenced
, writable
, result
);
2116 result
= SCAN_PAGE_RO
;
2120 release_pte_pages(pte
, _pte
);
2121 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
2122 referenced
, writable
, result
);
2126 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
2127 struct vm_area_struct
*vma
,
2128 unsigned long address
,
2132 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
; _pte
++) {
2133 pte_t pteval
= *_pte
;
2134 struct page
*src_page
;
2136 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2137 clear_user_highpage(page
, address
);
2138 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
2139 if (is_zero_pfn(pte_pfn(pteval
))) {
2141 * ptl mostly unnecessary.
2145 * paravirt calls inside pte_clear here are
2148 pte_clear(vma
->vm_mm
, address
, _pte
);
2152 src_page
= pte_page(pteval
);
2153 copy_user_highpage(page
, src_page
, address
, vma
);
2154 VM_BUG_ON_PAGE(page_mapcount(src_page
) != 1, src_page
);
2155 release_pte_page(src_page
);
2157 * ptl mostly unnecessary, but preempt has to
2158 * be disabled to update the per-cpu stats
2159 * inside page_remove_rmap().
2163 * paravirt calls inside pte_clear here are
2166 pte_clear(vma
->vm_mm
, address
, _pte
);
2167 page_remove_rmap(src_page
, false);
2169 free_page_and_swap_cache(src_page
);
2172 address
+= PAGE_SIZE
;
2177 static void khugepaged_alloc_sleep(void)
2181 add_wait_queue(&khugepaged_wait
, &wait
);
2182 freezable_schedule_timeout_interruptible(
2183 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
2184 remove_wait_queue(&khugepaged_wait
, &wait
);
2187 static int khugepaged_node_load
[MAX_NUMNODES
];
2189 static bool khugepaged_scan_abort(int nid
)
2194 * If zone_reclaim_mode is disabled, then no extra effort is made to
2195 * allocate memory locally.
2197 if (!zone_reclaim_mode
)
2200 /* If there is a count for this node already, it must be acceptable */
2201 if (khugepaged_node_load
[nid
])
2204 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
2205 if (!khugepaged_node_load
[i
])
2207 if (node_distance(nid
, i
) > RECLAIM_DISTANCE
)
2214 static int khugepaged_find_target_node(void)
2216 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
2217 int nid
, target_node
= 0, max_value
= 0;
2219 /* find first node with max normal pages hit */
2220 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
2221 if (khugepaged_node_load
[nid
] > max_value
) {
2222 max_value
= khugepaged_node_load
[nid
];
2226 /* do some balance if several nodes have the same hit record */
2227 if (target_node
<= last_khugepaged_target_node
)
2228 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
2230 if (max_value
== khugepaged_node_load
[nid
]) {
2235 last_khugepaged_target_node
= target_node
;
2239 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2241 if (IS_ERR(*hpage
)) {
2247 khugepaged_alloc_sleep();
2248 } else if (*hpage
) {
2256 static struct page
*
2257 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2258 unsigned long address
, int node
)
2260 VM_BUG_ON_PAGE(*hpage
, *hpage
);
2263 * Before allocating the hugepage, release the mmap_sem read lock.
2264 * The allocation can take potentially a long time if it involves
2265 * sync compaction, and we do not need to hold the mmap_sem during
2266 * that. We will recheck the vma after taking it again in write mode.
2268 up_read(&mm
->mmap_sem
);
2270 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
2271 if (unlikely(!*hpage
)) {
2272 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2273 *hpage
= ERR_PTR(-ENOMEM
);
2277 prep_transhuge_page(*hpage
);
2278 count_vm_event(THP_COLLAPSE_ALLOC
);
2282 static int khugepaged_find_target_node(void)
2287 static inline struct page
*alloc_khugepaged_hugepage(void)
2291 page
= alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2294 prep_transhuge_page(page
);
2298 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
2303 hpage
= alloc_khugepaged_hugepage();
2305 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2310 khugepaged_alloc_sleep();
2312 count_vm_event(THP_COLLAPSE_ALLOC
);
2313 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
2318 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2321 *hpage
= khugepaged_alloc_hugepage(wait
);
2323 if (unlikely(!*hpage
))
2329 static struct page
*
2330 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2331 unsigned long address
, int node
)
2333 up_read(&mm
->mmap_sem
);
2340 static bool hugepage_vma_check(struct vm_area_struct
*vma
)
2342 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
2343 (vma
->vm_flags
& VM_NOHUGEPAGE
))
2345 if (!vma
->anon_vma
|| vma
->vm_ops
)
2347 if (is_vma_temporary_stack(vma
))
2349 return !(vma
->vm_flags
& VM_NO_THP
);
2352 static void collapse_huge_page(struct mm_struct
*mm
,
2353 unsigned long address
,
2354 struct page
**hpage
,
2355 struct vm_area_struct
*vma
,
2361 struct page
*new_page
;
2362 spinlock_t
*pmd_ptl
, *pte_ptl
;
2363 int isolated
= 0, result
= 0;
2364 unsigned long hstart
, hend
;
2365 struct mem_cgroup
*memcg
;
2366 unsigned long mmun_start
; /* For mmu_notifiers */
2367 unsigned long mmun_end
; /* For mmu_notifiers */
2370 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2372 /* Only allocate from the target node */
2373 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE
| __GFP_THISNODE
;
2375 /* release the mmap_sem read lock. */
2376 new_page
= khugepaged_alloc_page(hpage
, gfp
, mm
, address
, node
);
2378 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
2382 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, gfp
, &memcg
, true))) {
2383 result
= SCAN_CGROUP_CHARGE_FAIL
;
2388 * Prevent all access to pagetables with the exception of
2389 * gup_fast later hanlded by the ptep_clear_flush and the VM
2390 * handled by the anon_vma lock + PG_lock.
2392 down_write(&mm
->mmap_sem
);
2393 if (unlikely(khugepaged_test_exit(mm
))) {
2394 result
= SCAN_ANY_PROCESS
;
2398 vma
= find_vma(mm
, address
);
2400 result
= SCAN_VMA_NULL
;
2403 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2404 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2405 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
) {
2406 result
= SCAN_ADDRESS_RANGE
;
2409 if (!hugepage_vma_check(vma
)) {
2410 result
= SCAN_VMA_CHECK
;
2413 pmd
= mm_find_pmd(mm
, address
);
2415 result
= SCAN_PMD_NULL
;
2419 anon_vma_lock_write(vma
->anon_vma
);
2421 pte
= pte_offset_map(pmd
, address
);
2422 pte_ptl
= pte_lockptr(mm
, pmd
);
2424 mmun_start
= address
;
2425 mmun_end
= address
+ HPAGE_PMD_SIZE
;
2426 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
2427 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
2429 * After this gup_fast can't run anymore. This also removes
2430 * any huge TLB entry from the CPU so we won't allow
2431 * huge and small TLB entries for the same virtual address
2432 * to avoid the risk of CPU bugs in that area.
2434 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
2435 spin_unlock(pmd_ptl
);
2436 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
2439 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
);
2440 spin_unlock(pte_ptl
);
2442 if (unlikely(!isolated
)) {
2445 BUG_ON(!pmd_none(*pmd
));
2447 * We can only use set_pmd_at when establishing
2448 * hugepmds and never for establishing regular pmds that
2449 * points to regular pagetables. Use pmd_populate for that
2451 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
2452 spin_unlock(pmd_ptl
);
2453 anon_vma_unlock_write(vma
->anon_vma
);
2459 * All pages are isolated and locked so anon_vma rmap
2460 * can't run anymore.
2462 anon_vma_unlock_write(vma
->anon_vma
);
2464 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
);
2466 __SetPageUptodate(new_page
);
2467 pgtable
= pmd_pgtable(_pmd
);
2469 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
2470 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
2473 * spin_lock() below is not the equivalent of smp_wmb(), so
2474 * this is needed to avoid the copy_huge_page writes to become
2475 * visible after the set_pmd_at() write.
2480 BUG_ON(!pmd_none(*pmd
));
2481 page_add_new_anon_rmap(new_page
, vma
, address
, true);
2482 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
2483 lru_cache_add_active_or_unevictable(new_page
, vma
);
2484 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
2485 set_pmd_at(mm
, address
, pmd
, _pmd
);
2486 update_mmu_cache_pmd(vma
, address
, pmd
);
2487 spin_unlock(pmd_ptl
);
2491 khugepaged_pages_collapsed
++;
2492 result
= SCAN_SUCCEED
;
2494 up_write(&mm
->mmap_sem
);
2495 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2499 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2502 mem_cgroup_cancel_charge(new_page
, memcg
, true);
2506 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
2507 struct vm_area_struct
*vma
,
2508 unsigned long address
,
2509 struct page
**hpage
)
2513 int ret
= 0, none_or_zero
= 0, result
= 0;
2514 struct page
*page
= NULL
;
2515 unsigned long _address
;
2517 int node
= NUMA_NO_NODE
;
2518 bool writable
= false, referenced
= false;
2520 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2522 pmd
= mm_find_pmd(mm
, address
);
2524 result
= SCAN_PMD_NULL
;
2528 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
2529 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
2530 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2531 _pte
++, _address
+= PAGE_SIZE
) {
2532 pte_t pteval
= *_pte
;
2533 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2534 if (!userfaultfd_armed(vma
) &&
2535 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2538 result
= SCAN_EXCEED_NONE_PTE
;
2542 if (!pte_present(pteval
)) {
2543 result
= SCAN_PTE_NON_PRESENT
;
2546 if (pte_write(pteval
))
2549 page
= vm_normal_page(vma
, _address
, pteval
);
2550 if (unlikely(!page
)) {
2551 result
= SCAN_PAGE_NULL
;
2555 /* TODO: teach khugepaged to collapse THP mapped with pte */
2556 if (PageCompound(page
)) {
2557 result
= SCAN_PAGE_COMPOUND
;
2562 * Record which node the original page is from and save this
2563 * information to khugepaged_node_load[].
2564 * Khupaged will allocate hugepage from the node has the max
2567 node
= page_to_nid(page
);
2568 if (khugepaged_scan_abort(node
)) {
2569 result
= SCAN_SCAN_ABORT
;
2572 khugepaged_node_load
[node
]++;
2573 if (!PageLRU(page
)) {
2574 result
= SCAN_PAGE_LRU
;
2577 if (PageLocked(page
)) {
2578 result
= SCAN_PAGE_LOCK
;
2581 if (!PageAnon(page
)) {
2582 result
= SCAN_PAGE_ANON
;
2587 * cannot use mapcount: can't collapse if there's a gup pin.
2588 * The page must only be referenced by the scanned process
2589 * and page swap cache.
2591 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2592 result
= SCAN_PAGE_COUNT
;
2595 if (pte_young(pteval
) ||
2596 page_is_young(page
) || PageReferenced(page
) ||
2597 mmu_notifier_test_young(vma
->vm_mm
, address
))
2602 result
= SCAN_SUCCEED
;
2605 result
= SCAN_NO_REFERENCED_PAGE
;
2608 result
= SCAN_PAGE_RO
;
2611 pte_unmap_unlock(pte
, ptl
);
2613 node
= khugepaged_find_target_node();
2614 /* collapse_huge_page will return with the mmap_sem released */
2615 collapse_huge_page(mm
, address
, hpage
, vma
, node
);
2618 trace_mm_khugepaged_scan_pmd(mm
, page
, writable
, referenced
,
2619 none_or_zero
, result
);
2623 static void collect_mm_slot(struct mm_slot
*mm_slot
)
2625 struct mm_struct
*mm
= mm_slot
->mm
;
2627 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2629 if (khugepaged_test_exit(mm
)) {
2631 hash_del(&mm_slot
->hash
);
2632 list_del(&mm_slot
->mm_node
);
2635 * Not strictly needed because the mm exited already.
2637 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2640 /* khugepaged_mm_lock actually not necessary for the below */
2641 free_mm_slot(mm_slot
);
2646 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2647 struct page
**hpage
)
2648 __releases(&khugepaged_mm_lock
)
2649 __acquires(&khugepaged_mm_lock
)
2651 struct mm_slot
*mm_slot
;
2652 struct mm_struct
*mm
;
2653 struct vm_area_struct
*vma
;
2657 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2659 if (khugepaged_scan
.mm_slot
)
2660 mm_slot
= khugepaged_scan
.mm_slot
;
2662 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2663 struct mm_slot
, mm_node
);
2664 khugepaged_scan
.address
= 0;
2665 khugepaged_scan
.mm_slot
= mm_slot
;
2667 spin_unlock(&khugepaged_mm_lock
);
2670 down_read(&mm
->mmap_sem
);
2671 if (unlikely(khugepaged_test_exit(mm
)))
2674 vma
= find_vma(mm
, khugepaged_scan
.address
);
2677 for (; vma
; vma
= vma
->vm_next
) {
2678 unsigned long hstart
, hend
;
2681 if (unlikely(khugepaged_test_exit(mm
))) {
2685 if (!hugepage_vma_check(vma
)) {
2690 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2691 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2694 if (khugepaged_scan
.address
> hend
)
2696 if (khugepaged_scan
.address
< hstart
)
2697 khugepaged_scan
.address
= hstart
;
2698 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2700 while (khugepaged_scan
.address
< hend
) {
2703 if (unlikely(khugepaged_test_exit(mm
)))
2704 goto breakouterloop
;
2706 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2707 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2709 ret
= khugepaged_scan_pmd(mm
, vma
,
2710 khugepaged_scan
.address
,
2712 /* move to next address */
2713 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2714 progress
+= HPAGE_PMD_NR
;
2716 /* we released mmap_sem so break loop */
2717 goto breakouterloop_mmap_sem
;
2718 if (progress
>= pages
)
2719 goto breakouterloop
;
2723 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
2724 breakouterloop_mmap_sem
:
2726 spin_lock(&khugepaged_mm_lock
);
2727 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2729 * Release the current mm_slot if this mm is about to die, or
2730 * if we scanned all vmas of this mm.
2732 if (khugepaged_test_exit(mm
) || !vma
) {
2734 * Make sure that if mm_users is reaching zero while
2735 * khugepaged runs here, khugepaged_exit will find
2736 * mm_slot not pointing to the exiting mm.
2738 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2739 khugepaged_scan
.mm_slot
= list_entry(
2740 mm_slot
->mm_node
.next
,
2741 struct mm_slot
, mm_node
);
2742 khugepaged_scan
.address
= 0;
2744 khugepaged_scan
.mm_slot
= NULL
;
2745 khugepaged_full_scans
++;
2748 collect_mm_slot(mm_slot
);
2754 static int khugepaged_has_work(void)
2756 return !list_empty(&khugepaged_scan
.mm_head
) &&
2757 khugepaged_enabled();
2760 static int khugepaged_wait_event(void)
2762 return !list_empty(&khugepaged_scan
.mm_head
) ||
2763 kthread_should_stop();
2766 static void khugepaged_do_scan(void)
2768 struct page
*hpage
= NULL
;
2769 unsigned int progress
= 0, pass_through_head
= 0;
2770 unsigned int pages
= khugepaged_pages_to_scan
;
2773 barrier(); /* write khugepaged_pages_to_scan to local stack */
2775 while (progress
< pages
) {
2776 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2781 if (unlikely(kthread_should_stop() || try_to_freeze()))
2784 spin_lock(&khugepaged_mm_lock
);
2785 if (!khugepaged_scan
.mm_slot
)
2786 pass_through_head
++;
2787 if (khugepaged_has_work() &&
2788 pass_through_head
< 2)
2789 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2793 spin_unlock(&khugepaged_mm_lock
);
2796 if (!IS_ERR_OR_NULL(hpage
))
2800 static void khugepaged_wait_work(void)
2802 if (khugepaged_has_work()) {
2803 if (!khugepaged_scan_sleep_millisecs
)
2806 wait_event_freezable_timeout(khugepaged_wait
,
2807 kthread_should_stop(),
2808 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
));
2812 if (khugepaged_enabled())
2813 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2816 static int khugepaged(void *none
)
2818 struct mm_slot
*mm_slot
;
2821 set_user_nice(current
, MAX_NICE
);
2823 while (!kthread_should_stop()) {
2824 khugepaged_do_scan();
2825 khugepaged_wait_work();
2828 spin_lock(&khugepaged_mm_lock
);
2829 mm_slot
= khugepaged_scan
.mm_slot
;
2830 khugepaged_scan
.mm_slot
= NULL
;
2832 collect_mm_slot(mm_slot
);
2833 spin_unlock(&khugepaged_mm_lock
);
2837 static void __split_huge_zero_page_pmd(struct vm_area_struct
*vma
,
2838 unsigned long haddr
, pmd_t
*pmd
)
2840 struct mm_struct
*mm
= vma
->vm_mm
;
2845 /* leave pmd empty until pte is filled */
2846 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2848 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2849 pmd_populate(mm
, &_pmd
, pgtable
);
2851 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2853 entry
= pfn_pte(my_zero_pfn(haddr
), vma
->vm_page_prot
);
2854 entry
= pte_mkspecial(entry
);
2855 pte
= pte_offset_map(&_pmd
, haddr
);
2856 VM_BUG_ON(!pte_none(*pte
));
2857 set_pte_at(mm
, haddr
, pte
, entry
);
2860 smp_wmb(); /* make pte visible before pmd */
2861 pmd_populate(mm
, pmd
, pgtable
);
2862 put_huge_zero_page();
2865 static void __split_huge_pmd_locked(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2866 unsigned long haddr
, bool freeze
)
2868 struct mm_struct
*mm
= vma
->vm_mm
;
2872 bool young
, write
, dirty
;
2876 VM_BUG_ON(haddr
& ~HPAGE_PMD_MASK
);
2877 VM_BUG_ON_VMA(vma
->vm_start
> haddr
, vma
);
2878 VM_BUG_ON_VMA(vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
, vma
);
2879 VM_BUG_ON(!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
));
2881 count_vm_event(THP_SPLIT_PMD
);
2883 if (vma_is_dax(vma
)) {
2884 pmd_t _pmd
= pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2885 if (is_huge_zero_pmd(_pmd
))
2886 put_huge_zero_page();
2888 } else if (is_huge_zero_pmd(*pmd
)) {
2889 return __split_huge_zero_page_pmd(vma
, haddr
, pmd
);
2892 page
= pmd_page(*pmd
);
2893 VM_BUG_ON_PAGE(!page_count(page
), page
);
2894 page_ref_add(page
, HPAGE_PMD_NR
- 1);
2895 write
= pmd_write(*pmd
);
2896 young
= pmd_young(*pmd
);
2897 dirty
= pmd_dirty(*pmd
);
2899 pmdp_huge_split_prepare(vma
, haddr
, pmd
);
2900 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2901 pmd_populate(mm
, &_pmd
, pgtable
);
2903 for (i
= 0, addr
= haddr
; i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
) {
2906 * Note that NUMA hinting access restrictions are not
2907 * transferred to avoid any possibility of altering
2908 * permissions across VMAs.
2911 swp_entry_t swp_entry
;
2912 swp_entry
= make_migration_entry(page
+ i
, write
);
2913 entry
= swp_entry_to_pte(swp_entry
);
2915 entry
= mk_pte(page
+ i
, vma
->vm_page_prot
);
2916 entry
= maybe_mkwrite(entry
, vma
);
2918 entry
= pte_wrprotect(entry
);
2920 entry
= pte_mkold(entry
);
2923 SetPageDirty(page
+ i
);
2924 pte
= pte_offset_map(&_pmd
, addr
);
2925 BUG_ON(!pte_none(*pte
));
2926 set_pte_at(mm
, addr
, pte
, entry
);
2927 atomic_inc(&page
[i
]._mapcount
);
2932 * Set PG_double_map before dropping compound_mapcount to avoid
2933 * false-negative page_mapped().
2935 if (compound_mapcount(page
) > 1 && !TestSetPageDoubleMap(page
)) {
2936 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2937 atomic_inc(&page
[i
]._mapcount
);
2940 if (atomic_add_negative(-1, compound_mapcount_ptr(page
))) {
2941 /* Last compound_mapcount is gone. */
2942 __dec_zone_page_state(page
, NR_ANON_TRANSPARENT_HUGEPAGES
);
2943 if (TestClearPageDoubleMap(page
)) {
2944 /* No need in mapcount reference anymore */
2945 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2946 atomic_dec(&page
[i
]._mapcount
);
2950 smp_wmb(); /* make pte visible before pmd */
2952 * Up to this point the pmd is present and huge and userland has the
2953 * whole access to the hugepage during the split (which happens in
2954 * place). If we overwrite the pmd with the not-huge version pointing
2955 * to the pte here (which of course we could if all CPUs were bug
2956 * free), userland could trigger a small page size TLB miss on the
2957 * small sized TLB while the hugepage TLB entry is still established in
2958 * the huge TLB. Some CPU doesn't like that.
2959 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2960 * 383 on page 93. Intel should be safe but is also warns that it's
2961 * only safe if the permission and cache attributes of the two entries
2962 * loaded in the two TLB is identical (which should be the case here).
2963 * But it is generally safer to never allow small and huge TLB entries
2964 * for the same virtual address to be loaded simultaneously. So instead
2965 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2966 * current pmd notpresent (atomically because here the pmd_trans_huge
2967 * and pmd_trans_splitting must remain set at all times on the pmd
2968 * until the split is complete for this pmd), then we flush the SMP TLB
2969 * and finally we write the non-huge version of the pmd entry with
2972 pmdp_invalidate(vma
, haddr
, pmd
);
2973 pmd_populate(mm
, pmd
, pgtable
);
2976 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
2977 page_remove_rmap(page
+ i
, false);
2983 void __split_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2984 unsigned long address
, bool freeze
)
2987 struct mm_struct
*mm
= vma
->vm_mm
;
2988 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
2990 mmu_notifier_invalidate_range_start(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
2991 ptl
= pmd_lock(mm
, pmd
);
2992 if (pmd_trans_huge(*pmd
)) {
2993 struct page
*page
= pmd_page(*pmd
);
2994 if (PageMlocked(page
))
2995 clear_page_mlock(page
);
2996 } else if (!pmd_devmap(*pmd
))
2998 __split_huge_pmd_locked(vma
, pmd
, haddr
, freeze
);
3001 mmu_notifier_invalidate_range_end(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
3004 void split_huge_pmd_address(struct vm_area_struct
*vma
, unsigned long address
,
3005 bool freeze
, struct page
*page
)
3011 pgd
= pgd_offset(vma
->vm_mm
, address
);
3012 if (!pgd_present(*pgd
))
3015 pud
= pud_offset(pgd
, address
);
3016 if (!pud_present(*pud
))
3019 pmd
= pmd_offset(pud
, address
);
3020 if (!pmd_present(*pmd
) || (!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
)))
3024 * If caller asks to setup a migration entries, we need a page to check
3025 * pmd against. Otherwise we can end up replacing wrong page.
3027 VM_BUG_ON(freeze
&& !page
);
3028 if (page
&& page
!= pmd_page(*pmd
))
3032 * Caller holds the mmap_sem write mode, so a huge pmd cannot
3033 * materialize from under us.
3035 __split_huge_pmd(vma
, pmd
, address
, freeze
);
3038 void vma_adjust_trans_huge(struct vm_area_struct
*vma
,
3039 unsigned long start
,
3044 * If the new start address isn't hpage aligned and it could
3045 * previously contain an hugepage: check if we need to split
3048 if (start
& ~HPAGE_PMD_MASK
&&
3049 (start
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3050 (start
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3051 split_huge_pmd_address(vma
, start
, false, NULL
);
3054 * If the new end address isn't hpage aligned and it could
3055 * previously contain an hugepage: check if we need to split
3058 if (end
& ~HPAGE_PMD_MASK
&&
3059 (end
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3060 (end
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3061 split_huge_pmd_address(vma
, end
, false, NULL
);
3064 * If we're also updating the vma->vm_next->vm_start, if the new
3065 * vm_next->vm_start isn't page aligned and it could previously
3066 * contain an hugepage: check if we need to split an huge pmd.
3068 if (adjust_next
> 0) {
3069 struct vm_area_struct
*next
= vma
->vm_next
;
3070 unsigned long nstart
= next
->vm_start
;
3071 nstart
+= adjust_next
<< PAGE_SHIFT
;
3072 if (nstart
& ~HPAGE_PMD_MASK
&&
3073 (nstart
& HPAGE_PMD_MASK
) >= next
->vm_start
&&
3074 (nstart
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= next
->vm_end
)
3075 split_huge_pmd_address(next
, nstart
, false, NULL
);
3079 static void freeze_page(struct page
*page
)
3081 enum ttu_flags ttu_flags
= TTU_MIGRATION
| TTU_IGNORE_MLOCK
|
3082 TTU_IGNORE_ACCESS
| TTU_RMAP_LOCKED
;
3085 VM_BUG_ON_PAGE(!PageHead(page
), page
);
3087 /* We only need TTU_SPLIT_HUGE_PMD once */
3088 ret
= try_to_unmap(page
, ttu_flags
| TTU_SPLIT_HUGE_PMD
);
3089 for (i
= 1; !ret
&& i
< HPAGE_PMD_NR
; i
++) {
3090 /* Cut short if the page is unmapped */
3091 if (page_count(page
) == 1)
3094 ret
= try_to_unmap(page
+ i
, ttu_flags
);
3099 static void unfreeze_page(struct page
*page
)
3103 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3104 remove_migration_ptes(page
+ i
, page
+ i
, true);
3107 static void __split_huge_page_tail(struct page
*head
, int tail
,
3108 struct lruvec
*lruvec
, struct list_head
*list
)
3110 struct page
*page_tail
= head
+ tail
;
3112 VM_BUG_ON_PAGE(atomic_read(&page_tail
->_mapcount
) != -1, page_tail
);
3113 VM_BUG_ON_PAGE(page_ref_count(page_tail
) != 0, page_tail
);
3116 * tail_page->_count is zero and not changing from under us. But
3117 * get_page_unless_zero() may be running from under us on the
3118 * tail_page. If we used atomic_set() below instead of atomic_inc(), we
3119 * would then run atomic_set() concurrently with
3120 * get_page_unless_zero(), and atomic_set() is implemented in C not
3121 * using locked ops. spin_unlock on x86 sometime uses locked ops
3122 * because of PPro errata 66, 92, so unless somebody can guarantee
3123 * atomic_set() here would be safe on all archs (and not only on x86),
3124 * it's safer to use atomic_inc().
3126 page_ref_inc(page_tail
);
3128 page_tail
->flags
&= ~PAGE_FLAGS_CHECK_AT_PREP
;
3129 page_tail
->flags
|= (head
->flags
&
3130 ((1L << PG_referenced
) |
3131 (1L << PG_swapbacked
) |
3132 (1L << PG_mlocked
) |
3133 (1L << PG_uptodate
) |
3136 (1L << PG_unevictable
) |
3140 * After clearing PageTail the gup refcount can be released.
3141 * Page flags also must be visible before we make the page non-compound.
3145 clear_compound_head(page_tail
);
3147 if (page_is_young(head
))
3148 set_page_young(page_tail
);
3149 if (page_is_idle(head
))
3150 set_page_idle(page_tail
);
3152 /* ->mapping in first tail page is compound_mapcount */
3153 VM_BUG_ON_PAGE(tail
> 2 && page_tail
->mapping
!= TAIL_MAPPING
,
3155 page_tail
->mapping
= head
->mapping
;
3157 page_tail
->index
= head
->index
+ tail
;
3158 page_cpupid_xchg_last(page_tail
, page_cpupid_last(head
));
3159 lru_add_page_tail(head
, page_tail
, lruvec
, list
);
3162 static void __split_huge_page(struct page
*page
, struct list_head
*list
)
3164 struct page
*head
= compound_head(page
);
3165 struct zone
*zone
= page_zone(head
);
3166 struct lruvec
*lruvec
;
3169 /* prevent PageLRU to go away from under us, and freeze lru stats */
3170 spin_lock_irq(&zone
->lru_lock
);
3171 lruvec
= mem_cgroup_page_lruvec(head
, zone
);
3173 /* complete memcg works before add pages to LRU */
3174 mem_cgroup_split_huge_fixup(head
);
3176 for (i
= HPAGE_PMD_NR
- 1; i
>= 1; i
--)
3177 __split_huge_page_tail(head
, i
, lruvec
, list
);
3179 ClearPageCompound(head
);
3180 spin_unlock_irq(&zone
->lru_lock
);
3182 unfreeze_page(head
);
3184 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3185 struct page
*subpage
= head
+ i
;
3186 if (subpage
== page
)
3188 unlock_page(subpage
);
3191 * Subpages may be freed if there wasn't any mapping
3192 * like if add_to_swap() is running on a lru page that
3193 * had its mapping zapped. And freeing these pages
3194 * requires taking the lru_lock so we do the put_page
3195 * of the tail pages after the split is complete.
3201 int total_mapcount(struct page
*page
)
3205 VM_BUG_ON_PAGE(PageTail(page
), page
);
3207 if (likely(!PageCompound(page
)))
3208 return atomic_read(&page
->_mapcount
) + 1;
3210 ret
= compound_mapcount(page
);
3213 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3214 ret
+= atomic_read(&page
[i
]._mapcount
) + 1;
3215 if (PageDoubleMap(page
))
3216 ret
-= HPAGE_PMD_NR
;
3221 * This calculates accurately how many mappings a transparent hugepage
3222 * has (unlike page_mapcount() which isn't fully accurate). This full
3223 * accuracy is primarily needed to know if copy-on-write faults can
3224 * reuse the page and change the mapping to read-write instead of
3225 * copying them. At the same time this returns the total_mapcount too.
3227 * The function returns the highest mapcount any one of the subpages
3228 * has. If the return value is one, even if different processes are
3229 * mapping different subpages of the transparent hugepage, they can
3230 * all reuse it, because each process is reusing a different subpage.
3232 * The total_mapcount is instead counting all virtual mappings of the
3233 * subpages. If the total_mapcount is equal to "one", it tells the
3234 * caller all mappings belong to the same "mm" and in turn the
3235 * anon_vma of the transparent hugepage can become the vma->anon_vma
3236 * local one as no other process may be mapping any of the subpages.
3238 * It would be more accurate to replace page_mapcount() with
3239 * page_trans_huge_mapcount(), however we only use
3240 * page_trans_huge_mapcount() in the copy-on-write faults where we
3241 * need full accuracy to avoid breaking page pinning, because
3242 * page_trans_huge_mapcount() is slower than page_mapcount().
3244 int page_trans_huge_mapcount(struct page
*page
, int *total_mapcount
)
3246 int i
, ret
, _total_mapcount
, mapcount
;
3248 /* hugetlbfs shouldn't call it */
3249 VM_BUG_ON_PAGE(PageHuge(page
), page
);
3251 if (likely(!PageTransCompound(page
))) {
3252 mapcount
= atomic_read(&page
->_mapcount
) + 1;
3254 *total_mapcount
= mapcount
;
3258 page
= compound_head(page
);
3260 _total_mapcount
= ret
= 0;
3261 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3262 mapcount
= atomic_read(&page
[i
]._mapcount
) + 1;
3263 ret
= max(ret
, mapcount
);
3264 _total_mapcount
+= mapcount
;
3266 if (PageDoubleMap(page
)) {
3268 _total_mapcount
-= HPAGE_PMD_NR
;
3270 mapcount
= compound_mapcount(page
);
3272 _total_mapcount
+= mapcount
;
3274 *total_mapcount
= _total_mapcount
;
3279 * This function splits huge page into normal pages. @page can point to any
3280 * subpage of huge page to split. Split doesn't change the position of @page.
3282 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3283 * The huge page must be locked.
3285 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3287 * Both head page and tail pages will inherit mapping, flags, and so on from
3290 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3291 * they are not mapped.
3293 * Returns 0 if the hugepage is split successfully.
3294 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3297 int split_huge_page_to_list(struct page
*page
, struct list_head
*list
)
3299 struct page
*head
= compound_head(page
);
3300 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(head
));
3301 struct anon_vma
*anon_vma
;
3302 int count
, mapcount
, ret
;
3304 unsigned long flags
;
3306 VM_BUG_ON_PAGE(is_huge_zero_page(page
), page
);
3307 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
3308 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
3309 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
3310 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
3313 * The caller does not necessarily hold an mmap_sem that would prevent
3314 * the anon_vma disappearing so we first we take a reference to it
3315 * and then lock the anon_vma for write. This is similar to
3316 * page_lock_anon_vma_read except the write lock is taken to serialise
3317 * against parallel split or collapse operations.
3319 anon_vma
= page_get_anon_vma(head
);
3324 anon_vma_lock_write(anon_vma
);
3327 * Racy check if we can split the page, before freeze_page() will
3330 if (total_mapcount(head
) != page_count(head
) - 1) {
3335 mlocked
= PageMlocked(page
);
3337 VM_BUG_ON_PAGE(compound_mapcount(head
), head
);
3339 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3343 /* Prevent deferred_split_scan() touching ->_count */
3344 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3345 count
= page_count(head
);
3346 mapcount
= total_mapcount(head
);
3347 if (!mapcount
&& count
== 1) {
3348 if (!list_empty(page_deferred_list(head
))) {
3349 pgdata
->split_queue_len
--;
3350 list_del(page_deferred_list(head
));
3352 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3353 __split_huge_page(page
, list
);
3355 } else if (IS_ENABLED(CONFIG_DEBUG_VM
) && mapcount
) {
3356 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3357 pr_alert("total_mapcount: %u, page_count(): %u\n",
3360 dump_page(head
, NULL
);
3361 dump_page(page
, "total_mapcount(head) > 0");
3364 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3365 unfreeze_page(head
);
3370 anon_vma_unlock_write(anon_vma
);
3371 put_anon_vma(anon_vma
);
3373 count_vm_event(!ret
? THP_SPLIT_PAGE
: THP_SPLIT_PAGE_FAILED
);
3377 void free_transhuge_page(struct page
*page
)
3379 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
3380 unsigned long flags
;
3382 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3383 if (!list_empty(page_deferred_list(page
))) {
3384 pgdata
->split_queue_len
--;
3385 list_del(page_deferred_list(page
));
3387 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3388 free_compound_page(page
);
3391 void deferred_split_huge_page(struct page
*page
)
3393 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
3394 unsigned long flags
;
3396 VM_BUG_ON_PAGE(!PageTransHuge(page
), page
);
3398 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3399 if (list_empty(page_deferred_list(page
))) {
3400 count_vm_event(THP_DEFERRED_SPLIT_PAGE
);
3401 list_add_tail(page_deferred_list(page
), &pgdata
->split_queue
);
3402 pgdata
->split_queue_len
++;
3404 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3407 static unsigned long deferred_split_count(struct shrinker
*shrink
,
3408 struct shrink_control
*sc
)
3410 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
3411 return ACCESS_ONCE(pgdata
->split_queue_len
);
3414 static unsigned long deferred_split_scan(struct shrinker
*shrink
,
3415 struct shrink_control
*sc
)
3417 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
3418 unsigned long flags
;
3419 LIST_HEAD(list
), *pos
, *next
;
3423 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3424 /* Take pin on all head pages to avoid freeing them under us */
3425 list_for_each_safe(pos
, next
, &pgdata
->split_queue
) {
3426 page
= list_entry((void *)pos
, struct page
, mapping
);
3427 page
= compound_head(page
);
3428 if (get_page_unless_zero(page
)) {
3429 list_move(page_deferred_list(page
), &list
);
3431 /* We lost race with put_compound_page() */
3432 list_del_init(page_deferred_list(page
));
3433 pgdata
->split_queue_len
--;
3435 if (!--sc
->nr_to_scan
)
3438 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3440 list_for_each_safe(pos
, next
, &list
) {
3441 page
= list_entry((void *)pos
, struct page
, mapping
);
3443 /* split_huge_page() removes page from list on success */
3444 if (!split_huge_page(page
))
3450 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
3451 list_splice_tail(&list
, &pgdata
->split_queue
);
3452 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
3455 * Stop shrinker if we didn't split any page, but the queue is empty.
3456 * This can happen if pages were freed under us.
3458 if (!split
&& list_empty(&pgdata
->split_queue
))
3463 static struct shrinker deferred_split_shrinker
= {
3464 .count_objects
= deferred_split_count
,
3465 .scan_objects
= deferred_split_scan
,
3466 .seeks
= DEFAULT_SEEKS
,
3467 .flags
= SHRINKER_NUMA_AWARE
,
3470 #ifdef CONFIG_DEBUG_FS
3471 static int split_huge_pages_set(void *data
, u64 val
)
3475 unsigned long pfn
, max_zone_pfn
;
3476 unsigned long total
= 0, split
= 0;
3481 for_each_populated_zone(zone
) {
3482 max_zone_pfn
= zone_end_pfn(zone
);
3483 for (pfn
= zone
->zone_start_pfn
; pfn
< max_zone_pfn
; pfn
++) {
3484 if (!pfn_valid(pfn
))
3487 page
= pfn_to_page(pfn
);
3488 if (!get_page_unless_zero(page
))
3491 if (zone
!= page_zone(page
))
3494 if (!PageHead(page
) || !PageAnon(page
) ||
3500 if (!split_huge_page(page
))
3508 pr_info("%lu of %lu THP split\n", split
, total
);
3512 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops
, NULL
, split_huge_pages_set
,
3515 static int __init
split_huge_pages_debugfs(void)
3519 ret
= debugfs_create_file("split_huge_pages", 0200, NULL
, NULL
,
3520 &split_huge_pages_fops
);
3522 pr_warn("Failed to create split_huge_pages in debugfs");
3525 late_initcall(split_huge_pages_debugfs
);