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_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
= HPAGE_PMD_NR
*8;
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
= HPAGE_PMD_NR
-1;
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 DEFINE_SPINLOCK(split_queue_lock
);
142 static LIST_HEAD(split_queue
);
143 static unsigned long split_queue_len
;
144 static struct shrinker deferred_split_shrinker
;
146 static void set_recommended_min_free_kbytes(void)
150 unsigned long recommended_min
;
152 for_each_populated_zone(zone
)
155 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
156 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
159 * Make sure that on average at least two pageblocks are almost free
160 * of another type, one for a migratetype to fall back to and a
161 * second to avoid subsequent fallbacks of other types There are 3
162 * MIGRATE_TYPES we care about.
164 recommended_min
+= pageblock_nr_pages
* nr_zones
*
165 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
167 /* don't ever allow to reserve more than 5% of the lowmem */
168 recommended_min
= min(recommended_min
,
169 (unsigned long) nr_free_buffer_pages() / 20);
170 recommended_min
<<= (PAGE_SHIFT
-10);
172 if (recommended_min
> min_free_kbytes
) {
173 if (user_min_free_kbytes
>= 0)
174 pr_info("raising min_free_kbytes from %d to %lu "
175 "to help transparent hugepage allocations\n",
176 min_free_kbytes
, recommended_min
);
178 min_free_kbytes
= recommended_min
;
180 setup_per_zone_wmarks();
183 static int start_stop_khugepaged(void)
186 if (khugepaged_enabled()) {
187 if (!khugepaged_thread
)
188 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
190 if (IS_ERR(khugepaged_thread
)) {
191 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
192 err
= PTR_ERR(khugepaged_thread
);
193 khugepaged_thread
= NULL
;
197 if (!list_empty(&khugepaged_scan
.mm_head
))
198 wake_up_interruptible(&khugepaged_wait
);
200 set_recommended_min_free_kbytes();
201 } else if (khugepaged_thread
) {
202 kthread_stop(khugepaged_thread
);
203 khugepaged_thread
= NULL
;
209 static atomic_t huge_zero_refcount
;
210 struct page
*huge_zero_page __read_mostly
;
212 struct page
*get_huge_zero_page(void)
214 struct page
*zero_page
;
216 if (likely(atomic_inc_not_zero(&huge_zero_refcount
)))
217 return READ_ONCE(huge_zero_page
);
219 zero_page
= alloc_pages((GFP_TRANSHUGE
| __GFP_ZERO
) & ~__GFP_MOVABLE
,
222 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED
);
225 count_vm_event(THP_ZERO_PAGE_ALLOC
);
227 if (cmpxchg(&huge_zero_page
, NULL
, zero_page
)) {
229 __free_pages(zero_page
, compound_order(zero_page
));
233 /* We take additional reference here. It will be put back by shrinker */
234 atomic_set(&huge_zero_refcount
, 2);
236 return READ_ONCE(huge_zero_page
);
239 static void put_huge_zero_page(void)
242 * Counter should never go to zero here. Only shrinker can put
245 BUG_ON(atomic_dec_and_test(&huge_zero_refcount
));
248 static unsigned long shrink_huge_zero_page_count(struct shrinker
*shrink
,
249 struct shrink_control
*sc
)
251 /* we can free zero page only if last reference remains */
252 return atomic_read(&huge_zero_refcount
) == 1 ? HPAGE_PMD_NR
: 0;
255 static unsigned long shrink_huge_zero_page_scan(struct shrinker
*shrink
,
256 struct shrink_control
*sc
)
258 if (atomic_cmpxchg(&huge_zero_refcount
, 1, 0) == 1) {
259 struct page
*zero_page
= xchg(&huge_zero_page
, NULL
);
260 BUG_ON(zero_page
== NULL
);
261 __free_pages(zero_page
, compound_order(zero_page
));
268 static struct shrinker huge_zero_page_shrinker
= {
269 .count_objects
= shrink_huge_zero_page_count
,
270 .scan_objects
= shrink_huge_zero_page_scan
,
271 .seeks
= DEFAULT_SEEKS
,
276 static ssize_t
double_flag_show(struct kobject
*kobj
,
277 struct kobj_attribute
*attr
, char *buf
,
278 enum transparent_hugepage_flag enabled
,
279 enum transparent_hugepage_flag req_madv
)
281 if (test_bit(enabled
, &transparent_hugepage_flags
)) {
282 VM_BUG_ON(test_bit(req_madv
, &transparent_hugepage_flags
));
283 return sprintf(buf
, "[always] madvise never\n");
284 } else if (test_bit(req_madv
, &transparent_hugepage_flags
))
285 return sprintf(buf
, "always [madvise] never\n");
287 return sprintf(buf
, "always madvise [never]\n");
289 static ssize_t
double_flag_store(struct kobject
*kobj
,
290 struct kobj_attribute
*attr
,
291 const char *buf
, size_t count
,
292 enum transparent_hugepage_flag enabled
,
293 enum transparent_hugepage_flag req_madv
)
295 if (!memcmp("always", buf
,
296 min(sizeof("always")-1, count
))) {
297 set_bit(enabled
, &transparent_hugepage_flags
);
298 clear_bit(req_madv
, &transparent_hugepage_flags
);
299 } else if (!memcmp("madvise", buf
,
300 min(sizeof("madvise")-1, count
))) {
301 clear_bit(enabled
, &transparent_hugepage_flags
);
302 set_bit(req_madv
, &transparent_hugepage_flags
);
303 } else if (!memcmp("never", buf
,
304 min(sizeof("never")-1, count
))) {
305 clear_bit(enabled
, &transparent_hugepage_flags
);
306 clear_bit(req_madv
, &transparent_hugepage_flags
);
313 static ssize_t
enabled_show(struct kobject
*kobj
,
314 struct kobj_attribute
*attr
, char *buf
)
316 return double_flag_show(kobj
, attr
, buf
,
317 TRANSPARENT_HUGEPAGE_FLAG
,
318 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
320 static ssize_t
enabled_store(struct kobject
*kobj
,
321 struct kobj_attribute
*attr
,
322 const char *buf
, size_t count
)
326 ret
= double_flag_store(kobj
, attr
, buf
, count
,
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 return double_flag_show(kobj
, attr
, buf
,
385 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
,
386 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
388 static ssize_t
defrag_store(struct kobject
*kobj
,
389 struct kobj_attribute
*attr
,
390 const char *buf
, size_t count
)
392 return double_flag_store(kobj
, attr
, buf
, count
,
393 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
,
394 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
396 static struct kobj_attribute defrag_attr
=
397 __ATTR(defrag
, 0644, defrag_show
, defrag_store
);
399 static ssize_t
use_zero_page_show(struct kobject
*kobj
,
400 struct kobj_attribute
*attr
, char *buf
)
402 return single_flag_show(kobj
, attr
, buf
,
403 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
405 static ssize_t
use_zero_page_store(struct kobject
*kobj
,
406 struct kobj_attribute
*attr
, const char *buf
, size_t count
)
408 return single_flag_store(kobj
, attr
, buf
, count
,
409 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
411 static struct kobj_attribute use_zero_page_attr
=
412 __ATTR(use_zero_page
, 0644, use_zero_page_show
, use_zero_page_store
);
413 #ifdef CONFIG_DEBUG_VM
414 static ssize_t
debug_cow_show(struct kobject
*kobj
,
415 struct kobj_attribute
*attr
, char *buf
)
417 return single_flag_show(kobj
, attr
, buf
,
418 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
420 static ssize_t
debug_cow_store(struct kobject
*kobj
,
421 struct kobj_attribute
*attr
,
422 const char *buf
, size_t count
)
424 return single_flag_store(kobj
, attr
, buf
, count
,
425 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
427 static struct kobj_attribute debug_cow_attr
=
428 __ATTR(debug_cow
, 0644, debug_cow_show
, debug_cow_store
);
429 #endif /* CONFIG_DEBUG_VM */
431 static struct attribute
*hugepage_attr
[] = {
434 &use_zero_page_attr
.attr
,
435 #ifdef CONFIG_DEBUG_VM
436 &debug_cow_attr
.attr
,
441 static struct attribute_group hugepage_attr_group
= {
442 .attrs
= hugepage_attr
,
445 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
446 struct kobj_attribute
*attr
,
449 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
452 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
453 struct kobj_attribute
*attr
,
454 const char *buf
, size_t count
)
459 err
= kstrtoul(buf
, 10, &msecs
);
460 if (err
|| msecs
> UINT_MAX
)
463 khugepaged_scan_sleep_millisecs
= msecs
;
464 wake_up_interruptible(&khugepaged_wait
);
468 static struct kobj_attribute scan_sleep_millisecs_attr
=
469 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
470 scan_sleep_millisecs_store
);
472 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
473 struct kobj_attribute
*attr
,
476 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
479 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
480 struct kobj_attribute
*attr
,
481 const char *buf
, size_t count
)
486 err
= kstrtoul(buf
, 10, &msecs
);
487 if (err
|| msecs
> UINT_MAX
)
490 khugepaged_alloc_sleep_millisecs
= msecs
;
491 wake_up_interruptible(&khugepaged_wait
);
495 static struct kobj_attribute alloc_sleep_millisecs_attr
=
496 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
497 alloc_sleep_millisecs_store
);
499 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
500 struct kobj_attribute
*attr
,
503 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
505 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
506 struct kobj_attribute
*attr
,
507 const char *buf
, size_t count
)
512 err
= kstrtoul(buf
, 10, &pages
);
513 if (err
|| !pages
|| pages
> UINT_MAX
)
516 khugepaged_pages_to_scan
= pages
;
520 static struct kobj_attribute pages_to_scan_attr
=
521 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
522 pages_to_scan_store
);
524 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
525 struct kobj_attribute
*attr
,
528 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
530 static struct kobj_attribute pages_collapsed_attr
=
531 __ATTR_RO(pages_collapsed
);
533 static ssize_t
full_scans_show(struct kobject
*kobj
,
534 struct kobj_attribute
*attr
,
537 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
539 static struct kobj_attribute full_scans_attr
=
540 __ATTR_RO(full_scans
);
542 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
543 struct kobj_attribute
*attr
, char *buf
)
545 return single_flag_show(kobj
, attr
, buf
,
546 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
548 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
549 struct kobj_attribute
*attr
,
550 const char *buf
, size_t count
)
552 return single_flag_store(kobj
, attr
, buf
, count
,
553 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
555 static struct kobj_attribute khugepaged_defrag_attr
=
556 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
557 khugepaged_defrag_store
);
560 * max_ptes_none controls if khugepaged should collapse hugepages over
561 * any unmapped ptes in turn potentially increasing the memory
562 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
563 * reduce the available free memory in the system as it
564 * runs. Increasing max_ptes_none will instead potentially reduce the
565 * free memory in the system during the khugepaged scan.
567 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
568 struct kobj_attribute
*attr
,
571 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
573 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
574 struct kobj_attribute
*attr
,
575 const char *buf
, size_t count
)
578 unsigned long max_ptes_none
;
580 err
= kstrtoul(buf
, 10, &max_ptes_none
);
581 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
584 khugepaged_max_ptes_none
= max_ptes_none
;
588 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
589 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
590 khugepaged_max_ptes_none_store
);
592 static struct attribute
*khugepaged_attr
[] = {
593 &khugepaged_defrag_attr
.attr
,
594 &khugepaged_max_ptes_none_attr
.attr
,
595 &pages_to_scan_attr
.attr
,
596 &pages_collapsed_attr
.attr
,
597 &full_scans_attr
.attr
,
598 &scan_sleep_millisecs_attr
.attr
,
599 &alloc_sleep_millisecs_attr
.attr
,
603 static struct attribute_group khugepaged_attr_group
= {
604 .attrs
= khugepaged_attr
,
605 .name
= "khugepaged",
608 static int __init
hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
612 *hugepage_kobj
= kobject_create_and_add("transparent_hugepage", mm_kobj
);
613 if (unlikely(!*hugepage_kobj
)) {
614 pr_err("failed to create transparent hugepage kobject\n");
618 err
= sysfs_create_group(*hugepage_kobj
, &hugepage_attr_group
);
620 pr_err("failed to register transparent hugepage group\n");
624 err
= sysfs_create_group(*hugepage_kobj
, &khugepaged_attr_group
);
626 pr_err("failed to register transparent hugepage group\n");
627 goto remove_hp_group
;
633 sysfs_remove_group(*hugepage_kobj
, &hugepage_attr_group
);
635 kobject_put(*hugepage_kobj
);
639 static void __init
hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
641 sysfs_remove_group(hugepage_kobj
, &khugepaged_attr_group
);
642 sysfs_remove_group(hugepage_kobj
, &hugepage_attr_group
);
643 kobject_put(hugepage_kobj
);
646 static inline int hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
651 static inline void hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
654 #endif /* CONFIG_SYSFS */
656 static int __init
hugepage_init(void)
659 struct kobject
*hugepage_kobj
;
661 if (!has_transparent_hugepage()) {
662 transparent_hugepage_flags
= 0;
666 err
= hugepage_init_sysfs(&hugepage_kobj
);
670 err
= khugepaged_slab_init();
674 err
= register_shrinker(&huge_zero_page_shrinker
);
676 goto err_hzp_shrinker
;
677 err
= register_shrinker(&deferred_split_shrinker
);
679 goto err_split_shrinker
;
682 * By default disable transparent hugepages on smaller systems,
683 * where the extra memory used could hurt more than TLB overhead
684 * is likely to save. The admin can still enable it through /sys.
686 if (totalram_pages
< (512 << (20 - PAGE_SHIFT
))) {
687 transparent_hugepage_flags
= 0;
691 err
= start_stop_khugepaged();
697 unregister_shrinker(&deferred_split_shrinker
);
699 unregister_shrinker(&huge_zero_page_shrinker
);
701 khugepaged_slab_exit();
703 hugepage_exit_sysfs(hugepage_kobj
);
707 subsys_initcall(hugepage_init
);
709 static int __init
setup_transparent_hugepage(char *str
)
714 if (!strcmp(str
, "always")) {
715 set_bit(TRANSPARENT_HUGEPAGE_FLAG
,
716 &transparent_hugepage_flags
);
717 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
718 &transparent_hugepage_flags
);
720 } else if (!strcmp(str
, "madvise")) {
721 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
722 &transparent_hugepage_flags
);
723 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
724 &transparent_hugepage_flags
);
726 } else if (!strcmp(str
, "never")) {
727 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
728 &transparent_hugepage_flags
);
729 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
730 &transparent_hugepage_flags
);
735 pr_warn("transparent_hugepage= cannot parse, ignored\n");
738 __setup("transparent_hugepage=", setup_transparent_hugepage
);
740 pmd_t
maybe_pmd_mkwrite(pmd_t pmd
, struct vm_area_struct
*vma
)
742 if (likely(vma
->vm_flags
& VM_WRITE
))
743 pmd
= pmd_mkwrite(pmd
);
747 static inline pmd_t
mk_huge_pmd(struct page
*page
, pgprot_t prot
)
750 entry
= mk_pmd(page
, prot
);
751 entry
= pmd_mkhuge(entry
);
755 static inline struct list_head
*page_deferred_list(struct page
*page
)
758 * ->lru in the tail pages is occupied by compound_head.
759 * Let's use ->mapping + ->index in the second tail page as list_head.
761 return (struct list_head
*)&page
[2].mapping
;
764 void prep_transhuge_page(struct page
*page
)
767 * we use page->mapping and page->indexlru in second tail page
768 * as list_head: assuming THP order >= 2
770 BUILD_BUG_ON(HPAGE_PMD_ORDER
< 2);
772 INIT_LIST_HEAD(page_deferred_list(page
));
773 set_compound_page_dtor(page
, TRANSHUGE_PAGE_DTOR
);
776 static int __do_huge_pmd_anonymous_page(struct mm_struct
*mm
,
777 struct vm_area_struct
*vma
,
778 unsigned long address
, pmd_t
*pmd
,
779 struct page
*page
, gfp_t gfp
,
782 struct mem_cgroup
*memcg
;
785 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
787 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
789 if (mem_cgroup_try_charge(page
, mm
, gfp
, &memcg
, true)) {
791 count_vm_event(THP_FAULT_FALLBACK
);
792 return VM_FAULT_FALLBACK
;
795 pgtable
= pte_alloc_one(mm
, haddr
);
796 if (unlikely(!pgtable
)) {
797 mem_cgroup_cancel_charge(page
, memcg
, true);
802 clear_huge_page(page
, haddr
, HPAGE_PMD_NR
);
804 * The memory barrier inside __SetPageUptodate makes sure that
805 * clear_huge_page writes become visible before the set_pmd_at()
808 __SetPageUptodate(page
);
810 ptl
= pmd_lock(mm
, pmd
);
811 if (unlikely(!pmd_none(*pmd
))) {
813 mem_cgroup_cancel_charge(page
, memcg
, true);
815 pte_free(mm
, pgtable
);
819 /* Deliver the page fault to userland */
820 if (userfaultfd_missing(vma
)) {
824 mem_cgroup_cancel_charge(page
, memcg
, true);
826 pte_free(mm
, pgtable
);
827 ret
= handle_userfault(vma
, address
, flags
,
829 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
833 entry
= mk_huge_pmd(page
, vma
->vm_page_prot
);
834 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
835 page_add_new_anon_rmap(page
, vma
, haddr
, true);
836 mem_cgroup_commit_charge(page
, memcg
, false, true);
837 lru_cache_add_active_or_unevictable(page
, vma
);
838 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
839 set_pmd_at(mm
, haddr
, pmd
, entry
);
840 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
841 atomic_long_inc(&mm
->nr_ptes
);
843 count_vm_event(THP_FAULT_ALLOC
);
849 static inline gfp_t
alloc_hugepage_gfpmask(int defrag
, gfp_t extra_gfp
)
851 return (GFP_TRANSHUGE
& ~(defrag
? 0 : __GFP_RECLAIM
)) | extra_gfp
;
854 /* Caller must hold page table lock. */
855 static bool set_huge_zero_page(pgtable_t pgtable
, struct mm_struct
*mm
,
856 struct vm_area_struct
*vma
, unsigned long haddr
, pmd_t
*pmd
,
857 struct page
*zero_page
)
862 entry
= mk_pmd(zero_page
, vma
->vm_page_prot
);
863 entry
= pmd_mkhuge(entry
);
864 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
865 set_pmd_at(mm
, haddr
, pmd
, entry
);
866 atomic_long_inc(&mm
->nr_ptes
);
870 int do_huge_pmd_anonymous_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
871 unsigned long address
, pmd_t
*pmd
,
876 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
878 if (haddr
< vma
->vm_start
|| haddr
+ HPAGE_PMD_SIZE
> vma
->vm_end
)
879 return VM_FAULT_FALLBACK
;
880 if (unlikely(anon_vma_prepare(vma
)))
882 if (unlikely(khugepaged_enter(vma
, vma
->vm_flags
)))
884 if (!(flags
& FAULT_FLAG_WRITE
) && !mm_forbids_zeropage(mm
) &&
885 transparent_hugepage_use_zero_page()) {
888 struct page
*zero_page
;
891 pgtable
= pte_alloc_one(mm
, haddr
);
892 if (unlikely(!pgtable
))
894 zero_page
= get_huge_zero_page();
895 if (unlikely(!zero_page
)) {
896 pte_free(mm
, pgtable
);
897 count_vm_event(THP_FAULT_FALLBACK
);
898 return VM_FAULT_FALLBACK
;
900 ptl
= pmd_lock(mm
, pmd
);
903 if (pmd_none(*pmd
)) {
904 if (userfaultfd_missing(vma
)) {
906 ret
= handle_userfault(vma
, address
, flags
,
908 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
910 set_huge_zero_page(pgtable
, mm
, vma
,
919 pte_free(mm
, pgtable
);
920 put_huge_zero_page();
924 gfp
= alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma
), 0);
925 page
= alloc_hugepage_vma(gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
926 if (unlikely(!page
)) {
927 count_vm_event(THP_FAULT_FALLBACK
);
928 return VM_FAULT_FALLBACK
;
930 prep_transhuge_page(page
);
931 return __do_huge_pmd_anonymous_page(mm
, vma
, address
, pmd
, page
, gfp
,
935 static void insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
936 pmd_t
*pmd
, pfn_t pfn
, pgprot_t prot
, bool write
)
938 struct mm_struct
*mm
= vma
->vm_mm
;
942 ptl
= pmd_lock(mm
, pmd
);
943 entry
= pmd_mkhuge(pfn_t_pmd(pfn
, prot
));
944 if (pfn_t_devmap(pfn
))
945 entry
= pmd_mkdevmap(entry
);
947 entry
= pmd_mkyoung(pmd_mkdirty(entry
));
948 entry
= maybe_pmd_mkwrite(entry
, vma
);
950 set_pmd_at(mm
, addr
, pmd
, entry
);
951 update_mmu_cache_pmd(vma
, addr
, pmd
);
955 int vmf_insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
956 pmd_t
*pmd
, pfn_t pfn
, bool write
)
958 pgprot_t pgprot
= vma
->vm_page_prot
;
960 * If we had pmd_special, we could avoid all these restrictions,
961 * but we need to be consistent with PTEs and architectures that
962 * can't support a 'special' bit.
964 BUG_ON(!(vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)));
965 BUG_ON((vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)) ==
966 (VM_PFNMAP
|VM_MIXEDMAP
));
967 BUG_ON((vma
->vm_flags
& VM_PFNMAP
) && is_cow_mapping(vma
->vm_flags
));
968 BUG_ON(!pfn_t_devmap(pfn
));
970 if (addr
< vma
->vm_start
|| addr
>= vma
->vm_end
)
971 return VM_FAULT_SIGBUS
;
972 if (track_pfn_insert(vma
, &pgprot
, pfn
))
973 return VM_FAULT_SIGBUS
;
974 insert_pfn_pmd(vma
, addr
, pmd
, pfn
, pgprot
, write
);
975 return VM_FAULT_NOPAGE
;
978 static void touch_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
984 * We should set the dirty bit only for FOLL_WRITE but for now
985 * the dirty bit in the pmd is meaningless. And if the dirty
986 * bit will become meaningful and we'll only set it with
987 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
988 * set the young bit, instead of the current set_pmd_at.
990 _pmd
= pmd_mkyoung(pmd_mkdirty(*pmd
));
991 if (pmdp_set_access_flags(vma
, addr
& HPAGE_PMD_MASK
,
993 update_mmu_cache_pmd(vma
, addr
, pmd
);
996 struct page
*follow_devmap_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
997 pmd_t
*pmd
, int flags
)
999 unsigned long pfn
= pmd_pfn(*pmd
);
1000 struct mm_struct
*mm
= vma
->vm_mm
;
1001 struct dev_pagemap
*pgmap
;
1004 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1006 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1009 if (pmd_present(*pmd
) && pmd_devmap(*pmd
))
1014 if (flags
& FOLL_TOUCH
)
1015 touch_pmd(vma
, addr
, pmd
);
1018 * device mapped pages can only be returned if the
1019 * caller will manage the page reference count.
1021 if (!(flags
& FOLL_GET
))
1022 return ERR_PTR(-EEXIST
);
1024 pfn
+= (addr
& ~PMD_MASK
) >> PAGE_SHIFT
;
1025 pgmap
= get_dev_pagemap(pfn
, NULL
);
1027 return ERR_PTR(-EFAULT
);
1028 page
= pfn_to_page(pfn
);
1030 put_dev_pagemap(pgmap
);
1035 int copy_huge_pmd(struct mm_struct
*dst_mm
, struct mm_struct
*src_mm
,
1036 pmd_t
*dst_pmd
, pmd_t
*src_pmd
, unsigned long addr
,
1037 struct vm_area_struct
*vma
)
1039 spinlock_t
*dst_ptl
, *src_ptl
;
1040 struct page
*src_page
;
1046 pgtable
= pte_alloc_one(dst_mm
, addr
);
1047 if (unlikely(!pgtable
))
1050 dst_ptl
= pmd_lock(dst_mm
, dst_pmd
);
1051 src_ptl
= pmd_lockptr(src_mm
, src_pmd
);
1052 spin_lock_nested(src_ptl
, SINGLE_DEPTH_NESTING
);
1056 if (unlikely(!pmd_trans_huge(pmd
) && !pmd_devmap(pmd
))) {
1057 pte_free(dst_mm
, pgtable
);
1061 * When page table lock is held, the huge zero pmd should not be
1062 * under splitting since we don't split the page itself, only pmd to
1065 if (is_huge_zero_pmd(pmd
)) {
1066 struct page
*zero_page
;
1068 * get_huge_zero_page() will never allocate a new page here,
1069 * since we already have a zero page to copy. It just takes a
1072 zero_page
= get_huge_zero_page();
1073 set_huge_zero_page(pgtable
, dst_mm
, vma
, addr
, dst_pmd
,
1079 if (pmd_trans_huge(pmd
)) {
1080 /* thp accounting separate from pmd_devmap accounting */
1081 src_page
= pmd_page(pmd
);
1082 VM_BUG_ON_PAGE(!PageHead(src_page
), src_page
);
1084 page_dup_rmap(src_page
, true);
1085 add_mm_counter(dst_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1086 atomic_long_inc(&dst_mm
->nr_ptes
);
1087 pgtable_trans_huge_deposit(dst_mm
, dst_pmd
, pgtable
);
1090 pmdp_set_wrprotect(src_mm
, addr
, src_pmd
);
1091 pmd
= pmd_mkold(pmd_wrprotect(pmd
));
1092 set_pmd_at(dst_mm
, addr
, dst_pmd
, pmd
);
1096 spin_unlock(src_ptl
);
1097 spin_unlock(dst_ptl
);
1102 void huge_pmd_set_accessed(struct mm_struct
*mm
,
1103 struct vm_area_struct
*vma
,
1104 unsigned long address
,
1105 pmd_t
*pmd
, pmd_t orig_pmd
,
1110 unsigned long haddr
;
1112 ptl
= pmd_lock(mm
, pmd
);
1113 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1116 entry
= pmd_mkyoung(orig_pmd
);
1117 haddr
= address
& HPAGE_PMD_MASK
;
1118 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, dirty
))
1119 update_mmu_cache_pmd(vma
, address
, pmd
);
1125 static int do_huge_pmd_wp_page_fallback(struct mm_struct
*mm
,
1126 struct vm_area_struct
*vma
,
1127 unsigned long address
,
1128 pmd_t
*pmd
, pmd_t orig_pmd
,
1130 unsigned long haddr
)
1132 struct mem_cgroup
*memcg
;
1137 struct page
**pages
;
1138 unsigned long mmun_start
; /* For mmu_notifiers */
1139 unsigned long mmun_end
; /* For mmu_notifiers */
1141 pages
= kmalloc(sizeof(struct page
*) * HPAGE_PMD_NR
,
1143 if (unlikely(!pages
)) {
1144 ret
|= VM_FAULT_OOM
;
1148 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1149 pages
[i
] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE
|
1151 vma
, address
, page_to_nid(page
));
1152 if (unlikely(!pages
[i
] ||
1153 mem_cgroup_try_charge(pages
[i
], mm
, GFP_KERNEL
,
1158 memcg
= (void *)page_private(pages
[i
]);
1159 set_page_private(pages
[i
], 0);
1160 mem_cgroup_cancel_charge(pages
[i
], memcg
,
1165 ret
|= VM_FAULT_OOM
;
1168 set_page_private(pages
[i
], (unsigned long)memcg
);
1171 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1172 copy_user_highpage(pages
[i
], page
+ i
,
1173 haddr
+ PAGE_SIZE
* i
, vma
);
1174 __SetPageUptodate(pages
[i
]);
1179 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1180 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1182 ptl
= pmd_lock(mm
, pmd
);
1183 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1184 goto out_free_pages
;
1185 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1187 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1188 /* leave pmd empty until pte is filled */
1190 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
1191 pmd_populate(mm
, &_pmd
, pgtable
);
1193 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
1195 entry
= mk_pte(pages
[i
], vma
->vm_page_prot
);
1196 entry
= maybe_mkwrite(pte_mkdirty(entry
), vma
);
1197 memcg
= (void *)page_private(pages
[i
]);
1198 set_page_private(pages
[i
], 0);
1199 page_add_new_anon_rmap(pages
[i
], vma
, haddr
, false);
1200 mem_cgroup_commit_charge(pages
[i
], memcg
, false, false);
1201 lru_cache_add_active_or_unevictable(pages
[i
], vma
);
1202 pte
= pte_offset_map(&_pmd
, haddr
);
1203 VM_BUG_ON(!pte_none(*pte
));
1204 set_pte_at(mm
, haddr
, pte
, entry
);
1209 smp_wmb(); /* make pte visible before pmd */
1210 pmd_populate(mm
, pmd
, pgtable
);
1211 page_remove_rmap(page
, true);
1214 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1216 ret
|= VM_FAULT_WRITE
;
1224 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1225 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1226 memcg
= (void *)page_private(pages
[i
]);
1227 set_page_private(pages
[i
], 0);
1228 mem_cgroup_cancel_charge(pages
[i
], memcg
, false);
1235 int do_huge_pmd_wp_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1236 unsigned long address
, pmd_t
*pmd
, pmd_t orig_pmd
)
1240 struct page
*page
= NULL
, *new_page
;
1241 struct mem_cgroup
*memcg
;
1242 unsigned long haddr
;
1243 unsigned long mmun_start
; /* For mmu_notifiers */
1244 unsigned long mmun_end
; /* For mmu_notifiers */
1245 gfp_t huge_gfp
; /* for allocation and charge */
1247 ptl
= pmd_lockptr(mm
, pmd
);
1248 VM_BUG_ON_VMA(!vma
->anon_vma
, vma
);
1249 haddr
= address
& HPAGE_PMD_MASK
;
1250 if (is_huge_zero_pmd(orig_pmd
))
1253 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
1256 page
= pmd_page(orig_pmd
);
1257 VM_BUG_ON_PAGE(!PageCompound(page
) || !PageHead(page
), page
);
1259 * We can only reuse the page if nobody else maps the huge page or it's
1260 * part. We can do it by checking page_mapcount() on each sub-page, but
1262 * The cheaper way is to check page_count() to be equal 1: every
1263 * mapcount takes page reference reference, so this way we can
1264 * guarantee, that the PMD is the only mapping.
1265 * This can give false negative if somebody pinned the page, but that's
1268 if (page_mapcount(page
) == 1 && page_count(page
) == 1) {
1270 entry
= pmd_mkyoung(orig_pmd
);
1271 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1272 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, 1))
1273 update_mmu_cache_pmd(vma
, address
, pmd
);
1274 ret
|= VM_FAULT_WRITE
;
1280 if (transparent_hugepage_enabled(vma
) &&
1281 !transparent_hugepage_debug_cow()) {
1282 huge_gfp
= alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma
), 0);
1283 new_page
= alloc_hugepage_vma(huge_gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
1287 if (likely(new_page
)) {
1288 prep_transhuge_page(new_page
);
1291 split_huge_pmd(vma
, pmd
, address
);
1292 ret
|= VM_FAULT_FALLBACK
;
1294 ret
= do_huge_pmd_wp_page_fallback(mm
, vma
, address
,
1295 pmd
, orig_pmd
, page
, haddr
);
1296 if (ret
& VM_FAULT_OOM
) {
1297 split_huge_pmd(vma
, pmd
, address
);
1298 ret
|= VM_FAULT_FALLBACK
;
1302 count_vm_event(THP_FAULT_FALLBACK
);
1306 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, huge_gfp
, &memcg
,
1310 split_huge_pmd(vma
, pmd
, address
);
1313 split_huge_pmd(vma
, pmd
, address
);
1314 ret
|= VM_FAULT_FALLBACK
;
1315 count_vm_event(THP_FAULT_FALLBACK
);
1319 count_vm_event(THP_FAULT_ALLOC
);
1322 clear_huge_page(new_page
, haddr
, HPAGE_PMD_NR
);
1324 copy_user_huge_page(new_page
, page
, haddr
, vma
, HPAGE_PMD_NR
);
1325 __SetPageUptodate(new_page
);
1328 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1329 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1334 if (unlikely(!pmd_same(*pmd
, orig_pmd
))) {
1336 mem_cgroup_cancel_charge(new_page
, memcg
, true);
1341 entry
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1342 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1343 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1344 page_add_new_anon_rmap(new_page
, vma
, haddr
, true);
1345 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
1346 lru_cache_add_active_or_unevictable(new_page
, vma
);
1347 set_pmd_at(mm
, haddr
, pmd
, entry
);
1348 update_mmu_cache_pmd(vma
, address
, pmd
);
1350 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1351 put_huge_zero_page();
1353 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1354 page_remove_rmap(page
, true);
1357 ret
|= VM_FAULT_WRITE
;
1361 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1369 struct page
*follow_trans_huge_pmd(struct vm_area_struct
*vma
,
1374 struct mm_struct
*mm
= vma
->vm_mm
;
1375 struct page
*page
= NULL
;
1377 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1379 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1382 /* Avoid dumping huge zero page */
1383 if ((flags
& FOLL_DUMP
) && is_huge_zero_pmd(*pmd
))
1384 return ERR_PTR(-EFAULT
);
1386 /* Full NUMA hinting faults to serialise migration in fault paths */
1387 if ((flags
& FOLL_NUMA
) && pmd_protnone(*pmd
))
1390 page
= pmd_page(*pmd
);
1391 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1392 if (flags
& FOLL_TOUCH
)
1393 touch_pmd(vma
, addr
, pmd
);
1394 if ((flags
& FOLL_MLOCK
) && (vma
->vm_flags
& VM_LOCKED
)) {
1396 * We don't mlock() pte-mapped THPs. This way we can avoid
1397 * leaking mlocked pages into non-VM_LOCKED VMAs.
1399 * In most cases the pmd is the only mapping of the page as we
1400 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1401 * writable private mappings in populate_vma_page_range().
1403 * The only scenario when we have the page shared here is if we
1404 * mlocking read-only mapping shared over fork(). We skip
1405 * mlocking such pages.
1407 if (compound_mapcount(page
) == 1 && !PageDoubleMap(page
) &&
1408 page
->mapping
&& trylock_page(page
)) {
1411 mlock_vma_page(page
);
1415 page
+= (addr
& ~HPAGE_PMD_MASK
) >> PAGE_SHIFT
;
1416 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
1417 if (flags
& FOLL_GET
)
1424 /* NUMA hinting page fault entry point for trans huge pmds */
1425 int do_huge_pmd_numa_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
1426 unsigned long addr
, pmd_t pmd
, pmd_t
*pmdp
)
1429 struct anon_vma
*anon_vma
= NULL
;
1431 unsigned long haddr
= addr
& HPAGE_PMD_MASK
;
1432 int page_nid
= -1, this_nid
= numa_node_id();
1433 int target_nid
, last_cpupid
= -1;
1435 bool migrated
= false;
1439 /* A PROT_NONE fault should not end up here */
1440 BUG_ON(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)));
1442 ptl
= pmd_lock(mm
, pmdp
);
1443 if (unlikely(!pmd_same(pmd
, *pmdp
)))
1447 * If there are potential migrations, wait for completion and retry
1448 * without disrupting NUMA hinting information. Do not relock and
1449 * check_same as the page may no longer be mapped.
1451 if (unlikely(pmd_trans_migrating(*pmdp
))) {
1452 page
= pmd_page(*pmdp
);
1454 wait_on_page_locked(page
);
1458 page
= pmd_page(pmd
);
1459 BUG_ON(is_huge_zero_page(page
));
1460 page_nid
= page_to_nid(page
);
1461 last_cpupid
= page_cpupid_last(page
);
1462 count_vm_numa_event(NUMA_HINT_FAULTS
);
1463 if (page_nid
== this_nid
) {
1464 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL
);
1465 flags
|= TNF_FAULT_LOCAL
;
1468 /* See similar comment in do_numa_page for explanation */
1469 if (!(vma
->vm_flags
& VM_WRITE
))
1470 flags
|= TNF_NO_GROUP
;
1473 * Acquire the page lock to serialise THP migrations but avoid dropping
1474 * page_table_lock if at all possible
1476 page_locked
= trylock_page(page
);
1477 target_nid
= mpol_misplaced(page
, vma
, haddr
);
1478 if (target_nid
== -1) {
1479 /* If the page was locked, there are no parallel migrations */
1484 /* Migration could have started since the pmd_trans_migrating check */
1487 wait_on_page_locked(page
);
1493 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1494 * to serialises splits
1498 anon_vma
= page_lock_anon_vma_read(page
);
1500 /* Confirm the PMD did not change while page_table_lock was released */
1502 if (unlikely(!pmd_same(pmd
, *pmdp
))) {
1509 /* Bail if we fail to protect against THP splits for any reason */
1510 if (unlikely(!anon_vma
)) {
1517 * Migrate the THP to the requested node, returns with page unlocked
1518 * and access rights restored.
1521 migrated
= migrate_misplaced_transhuge_page(mm
, vma
,
1522 pmdp
, pmd
, addr
, page
, target_nid
);
1524 flags
|= TNF_MIGRATED
;
1525 page_nid
= target_nid
;
1527 flags
|= TNF_MIGRATE_FAIL
;
1531 BUG_ON(!PageLocked(page
));
1532 was_writable
= pmd_write(pmd
);
1533 pmd
= pmd_modify(pmd
, vma
->vm_page_prot
);
1534 pmd
= pmd_mkyoung(pmd
);
1536 pmd
= pmd_mkwrite(pmd
);
1537 set_pmd_at(mm
, haddr
, pmdp
, pmd
);
1538 update_mmu_cache_pmd(vma
, addr
, pmdp
);
1545 page_unlock_anon_vma_read(anon_vma
);
1548 task_numa_fault(last_cpupid
, page_nid
, HPAGE_PMD_NR
, flags
);
1553 int madvise_free_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1554 pmd_t
*pmd
, unsigned long addr
, unsigned long next
)
1560 struct mm_struct
*mm
= tlb
->mm
;
1563 if (!pmd_trans_huge_lock(pmd
, vma
, &ptl
))
1567 if (is_huge_zero_pmd(orig_pmd
)) {
1572 page
= pmd_page(orig_pmd
);
1574 * If other processes are mapping this page, we couldn't discard
1575 * the page unless they all do MADV_FREE so let's skip the page.
1577 if (page_mapcount(page
) != 1)
1580 if (!trylock_page(page
))
1584 * If user want to discard part-pages of THP, split it so MADV_FREE
1585 * will deactivate only them.
1587 if (next
- addr
!= HPAGE_PMD_SIZE
) {
1590 if (split_huge_page(page
)) {
1601 if (PageDirty(page
))
1602 ClearPageDirty(page
);
1605 if (PageActive(page
))
1606 deactivate_page(page
);
1608 if (pmd_young(orig_pmd
) || pmd_dirty(orig_pmd
)) {
1609 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1611 orig_pmd
= pmd_mkold(orig_pmd
);
1612 orig_pmd
= pmd_mkclean(orig_pmd
);
1614 set_pmd_at(mm
, addr
, pmd
, orig_pmd
);
1615 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1624 int zap_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1625 pmd_t
*pmd
, unsigned long addr
)
1630 if (!__pmd_trans_huge_lock(pmd
, vma
, &ptl
))
1633 * For architectures like ppc64 we look at deposited pgtable
1634 * when calling pmdp_huge_get_and_clear. So do the
1635 * pgtable_trans_huge_withdraw after finishing pmdp related
1638 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1640 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1641 if (vma_is_dax(vma
)) {
1643 if (is_huge_zero_pmd(orig_pmd
))
1644 put_huge_zero_page();
1645 } else if (is_huge_zero_pmd(orig_pmd
)) {
1646 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1647 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1649 put_huge_zero_page();
1651 struct page
*page
= pmd_page(orig_pmd
);
1652 page_remove_rmap(page
, true);
1653 VM_BUG_ON_PAGE(page_mapcount(page
) < 0, page
);
1654 add_mm_counter(tlb
->mm
, MM_ANONPAGES
, -HPAGE_PMD_NR
);
1655 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1656 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1657 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1659 tlb_remove_page(tlb
, page
);
1664 bool move_huge_pmd(struct vm_area_struct
*vma
, struct vm_area_struct
*new_vma
,
1665 unsigned long old_addr
,
1666 unsigned long new_addr
, unsigned long old_end
,
1667 pmd_t
*old_pmd
, pmd_t
*new_pmd
)
1669 spinlock_t
*old_ptl
, *new_ptl
;
1672 struct mm_struct
*mm
= vma
->vm_mm
;
1674 if ((old_addr
& ~HPAGE_PMD_MASK
) ||
1675 (new_addr
& ~HPAGE_PMD_MASK
) ||
1676 old_end
- old_addr
< HPAGE_PMD_SIZE
||
1677 (new_vma
->vm_flags
& VM_NOHUGEPAGE
))
1681 * The destination pmd shouldn't be established, free_pgtables()
1682 * should have release it.
1684 if (WARN_ON(!pmd_none(*new_pmd
))) {
1685 VM_BUG_ON(pmd_trans_huge(*new_pmd
));
1690 * We don't have to worry about the ordering of src and dst
1691 * ptlocks because exclusive mmap_sem prevents deadlock.
1693 if (__pmd_trans_huge_lock(old_pmd
, vma
, &old_ptl
)) {
1694 new_ptl
= pmd_lockptr(mm
, new_pmd
);
1695 if (new_ptl
!= old_ptl
)
1696 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
1697 pmd
= pmdp_huge_get_and_clear(mm
, old_addr
, old_pmd
);
1698 VM_BUG_ON(!pmd_none(*new_pmd
));
1700 if (pmd_move_must_withdraw(new_ptl
, old_ptl
)) {
1702 pgtable
= pgtable_trans_huge_withdraw(mm
, old_pmd
);
1703 pgtable_trans_huge_deposit(mm
, new_pmd
, pgtable
);
1705 set_pmd_at(mm
, new_addr
, new_pmd
, pmd_mksoft_dirty(pmd
));
1706 if (new_ptl
!= old_ptl
)
1707 spin_unlock(new_ptl
);
1708 spin_unlock(old_ptl
);
1716 * - 0 if PMD could not be locked
1717 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1718 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1720 int change_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1721 unsigned long addr
, pgprot_t newprot
, int prot_numa
)
1723 struct mm_struct
*mm
= vma
->vm_mm
;
1727 if (__pmd_trans_huge_lock(pmd
, vma
, &ptl
)) {
1729 bool preserve_write
= prot_numa
&& pmd_write(*pmd
);
1733 * Avoid trapping faults against the zero page. The read-only
1734 * data is likely to be read-cached on the local CPU and
1735 * local/remote hits to the zero page are not interesting.
1737 if (prot_numa
&& is_huge_zero_pmd(*pmd
)) {
1742 if (!prot_numa
|| !pmd_protnone(*pmd
)) {
1743 entry
= pmdp_huge_get_and_clear_notify(mm
, addr
, pmd
);
1744 entry
= pmd_modify(entry
, newprot
);
1746 entry
= pmd_mkwrite(entry
);
1748 set_pmd_at(mm
, addr
, pmd
, entry
);
1749 BUG_ON(!preserve_write
&& pmd_write(entry
));
1758 * Returns true if a given pmd maps a thp, false otherwise.
1760 * Note that if it returns true, this routine returns without unlocking page
1761 * table lock. So callers must unlock it.
1763 bool __pmd_trans_huge_lock(pmd_t
*pmd
, struct vm_area_struct
*vma
,
1766 *ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1767 if (likely(pmd_trans_huge(*pmd
) || pmd_devmap(*pmd
)))
1773 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1775 int hugepage_madvise(struct vm_area_struct
*vma
,
1776 unsigned long *vm_flags
, int advice
)
1782 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1783 * can't handle this properly after s390_enable_sie, so we simply
1784 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1786 if (mm_has_pgste(vma
->vm_mm
))
1790 * Be somewhat over-protective like KSM for now!
1792 if (*vm_flags
& VM_NO_THP
)
1794 *vm_flags
&= ~VM_NOHUGEPAGE
;
1795 *vm_flags
|= VM_HUGEPAGE
;
1797 * If the vma become good for khugepaged to scan,
1798 * register it here without waiting a page fault that
1799 * may not happen any time soon.
1801 if (unlikely(khugepaged_enter_vma_merge(vma
, *vm_flags
)))
1804 case MADV_NOHUGEPAGE
:
1806 * Be somewhat over-protective like KSM for now!
1808 if (*vm_flags
& VM_NO_THP
)
1810 *vm_flags
&= ~VM_HUGEPAGE
;
1811 *vm_flags
|= VM_NOHUGEPAGE
;
1813 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1814 * this vma even if we leave the mm registered in khugepaged if
1815 * it got registered before VM_NOHUGEPAGE was set.
1823 static int __init
khugepaged_slab_init(void)
1825 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
1826 sizeof(struct mm_slot
),
1827 __alignof__(struct mm_slot
), 0, NULL
);
1834 static void __init
khugepaged_slab_exit(void)
1836 kmem_cache_destroy(mm_slot_cache
);
1839 static inline struct mm_slot
*alloc_mm_slot(void)
1841 if (!mm_slot_cache
) /* initialization failed */
1843 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
1846 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
1848 kmem_cache_free(mm_slot_cache
, mm_slot
);
1851 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
1853 struct mm_slot
*mm_slot
;
1855 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
1856 if (mm
== mm_slot
->mm
)
1862 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
1863 struct mm_slot
*mm_slot
)
1866 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
1869 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
1871 return atomic_read(&mm
->mm_users
) == 0;
1874 int __khugepaged_enter(struct mm_struct
*mm
)
1876 struct mm_slot
*mm_slot
;
1879 mm_slot
= alloc_mm_slot();
1883 /* __khugepaged_exit() must not run from under us */
1884 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
1885 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
1886 free_mm_slot(mm_slot
);
1890 spin_lock(&khugepaged_mm_lock
);
1891 insert_to_mm_slots_hash(mm
, mm_slot
);
1893 * Insert just behind the scanning cursor, to let the area settle
1896 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
1897 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
1898 spin_unlock(&khugepaged_mm_lock
);
1900 atomic_inc(&mm
->mm_count
);
1902 wake_up_interruptible(&khugepaged_wait
);
1907 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
1908 unsigned long vm_flags
)
1910 unsigned long hstart
, hend
;
1913 * Not yet faulted in so we will register later in the
1914 * page fault if needed.
1918 /* khugepaged not yet working on file or special mappings */
1920 VM_BUG_ON_VMA(vm_flags
& VM_NO_THP
, vma
);
1921 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1922 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1924 return khugepaged_enter(vma
, vm_flags
);
1928 void __khugepaged_exit(struct mm_struct
*mm
)
1930 struct mm_slot
*mm_slot
;
1933 spin_lock(&khugepaged_mm_lock
);
1934 mm_slot
= get_mm_slot(mm
);
1935 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
1936 hash_del(&mm_slot
->hash
);
1937 list_del(&mm_slot
->mm_node
);
1940 spin_unlock(&khugepaged_mm_lock
);
1943 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
1944 free_mm_slot(mm_slot
);
1946 } else if (mm_slot
) {
1948 * This is required to serialize against
1949 * khugepaged_test_exit() (which is guaranteed to run
1950 * under mmap sem read mode). Stop here (after we
1951 * return all pagetables will be destroyed) until
1952 * khugepaged has finished working on the pagetables
1953 * under the mmap_sem.
1955 down_write(&mm
->mmap_sem
);
1956 up_write(&mm
->mmap_sem
);
1960 static void release_pte_page(struct page
*page
)
1962 /* 0 stands for page_is_file_cache(page) == false */
1963 dec_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
1965 putback_lru_page(page
);
1968 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
)
1970 while (--_pte
>= pte
) {
1971 pte_t pteval
= *_pte
;
1972 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)))
1973 release_pte_page(pte_page(pteval
));
1977 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
1978 unsigned long address
,
1981 struct page
*page
= NULL
;
1983 int none_or_zero
= 0, result
= 0;
1984 bool referenced
= false, writable
= false;
1986 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
1987 _pte
++, address
+= PAGE_SIZE
) {
1988 pte_t pteval
= *_pte
;
1989 if (pte_none(pteval
) || (pte_present(pteval
) &&
1990 is_zero_pfn(pte_pfn(pteval
)))) {
1991 if (!userfaultfd_armed(vma
) &&
1992 ++none_or_zero
<= khugepaged_max_ptes_none
) {
1995 result
= SCAN_EXCEED_NONE_PTE
;
1999 if (!pte_present(pteval
)) {
2000 result
= SCAN_PTE_NON_PRESENT
;
2003 page
= vm_normal_page(vma
, address
, pteval
);
2004 if (unlikely(!page
)) {
2005 result
= SCAN_PAGE_NULL
;
2009 VM_BUG_ON_PAGE(PageCompound(page
), page
);
2010 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
2011 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
2014 * We can do it before isolate_lru_page because the
2015 * page can't be freed from under us. NOTE: PG_lock
2016 * is needed to serialize against split_huge_page
2017 * when invoked from the VM.
2019 if (!trylock_page(page
)) {
2020 result
= SCAN_PAGE_LOCK
;
2025 * cannot use mapcount: can't collapse if there's a gup pin.
2026 * The page must only be referenced by the scanned process
2027 * and page swap cache.
2029 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2031 result
= SCAN_PAGE_COUNT
;
2034 if (pte_write(pteval
)) {
2037 if (PageSwapCache(page
) && !reuse_swap_page(page
)) {
2039 result
= SCAN_SWAP_CACHE_PAGE
;
2043 * Page is not in the swap cache. It can be collapsed
2049 * Isolate the page to avoid collapsing an hugepage
2050 * currently in use by the VM.
2052 if (isolate_lru_page(page
)) {
2054 result
= SCAN_DEL_PAGE_LRU
;
2057 /* 0 stands for page_is_file_cache(page) == false */
2058 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
2059 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
2060 VM_BUG_ON_PAGE(PageLRU(page
), page
);
2062 /* If there is no mapped pte young don't collapse the page */
2063 if (pte_young(pteval
) ||
2064 page_is_young(page
) || PageReferenced(page
) ||
2065 mmu_notifier_test_young(vma
->vm_mm
, address
))
2068 if (likely(writable
)) {
2069 if (likely(referenced
)) {
2070 result
= SCAN_SUCCEED
;
2071 trace_mm_collapse_huge_page_isolate(page_to_pfn(page
), none_or_zero
,
2072 referenced
, writable
, result
);
2076 result
= SCAN_PAGE_RO
;
2080 release_pte_pages(pte
, _pte
);
2081 trace_mm_collapse_huge_page_isolate(page_to_pfn(page
), none_or_zero
,
2082 referenced
, writable
, result
);
2086 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
2087 struct vm_area_struct
*vma
,
2088 unsigned long address
,
2092 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
; _pte
++) {
2093 pte_t pteval
= *_pte
;
2094 struct page
*src_page
;
2096 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2097 clear_user_highpage(page
, address
);
2098 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
2099 if (is_zero_pfn(pte_pfn(pteval
))) {
2101 * ptl mostly unnecessary.
2105 * paravirt calls inside pte_clear here are
2108 pte_clear(vma
->vm_mm
, address
, _pte
);
2112 src_page
= pte_page(pteval
);
2113 copy_user_highpage(page
, src_page
, address
, vma
);
2114 VM_BUG_ON_PAGE(page_mapcount(src_page
) != 1, src_page
);
2115 release_pte_page(src_page
);
2117 * ptl mostly unnecessary, but preempt has to
2118 * be disabled to update the per-cpu stats
2119 * inside page_remove_rmap().
2123 * paravirt calls inside pte_clear here are
2126 pte_clear(vma
->vm_mm
, address
, _pte
);
2127 page_remove_rmap(src_page
, false);
2129 free_page_and_swap_cache(src_page
);
2132 address
+= PAGE_SIZE
;
2137 static void khugepaged_alloc_sleep(void)
2141 add_wait_queue(&khugepaged_wait
, &wait
);
2142 freezable_schedule_timeout_interruptible(
2143 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
2144 remove_wait_queue(&khugepaged_wait
, &wait
);
2147 static int khugepaged_node_load
[MAX_NUMNODES
];
2149 static bool khugepaged_scan_abort(int nid
)
2154 * If zone_reclaim_mode is disabled, then no extra effort is made to
2155 * allocate memory locally.
2157 if (!zone_reclaim_mode
)
2160 /* If there is a count for this node already, it must be acceptable */
2161 if (khugepaged_node_load
[nid
])
2164 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
2165 if (!khugepaged_node_load
[i
])
2167 if (node_distance(nid
, i
) > RECLAIM_DISTANCE
)
2174 static int khugepaged_find_target_node(void)
2176 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
2177 int nid
, target_node
= 0, max_value
= 0;
2179 /* find first node with max normal pages hit */
2180 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
2181 if (khugepaged_node_load
[nid
] > max_value
) {
2182 max_value
= khugepaged_node_load
[nid
];
2186 /* do some balance if several nodes have the same hit record */
2187 if (target_node
<= last_khugepaged_target_node
)
2188 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
2190 if (max_value
== khugepaged_node_load
[nid
]) {
2195 last_khugepaged_target_node
= target_node
;
2199 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2201 if (IS_ERR(*hpage
)) {
2207 khugepaged_alloc_sleep();
2208 } else if (*hpage
) {
2216 static struct page
*
2217 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2218 unsigned long address
, int node
)
2220 VM_BUG_ON_PAGE(*hpage
, *hpage
);
2223 * Before allocating the hugepage, release the mmap_sem read lock.
2224 * The allocation can take potentially a long time if it involves
2225 * sync compaction, and we do not need to hold the mmap_sem during
2226 * that. We will recheck the vma after taking it again in write mode.
2228 up_read(&mm
->mmap_sem
);
2230 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
2231 if (unlikely(!*hpage
)) {
2232 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2233 *hpage
= ERR_PTR(-ENOMEM
);
2237 prep_transhuge_page(*hpage
);
2238 count_vm_event(THP_COLLAPSE_ALLOC
);
2242 static int khugepaged_find_target_node(void)
2247 static inline struct page
*alloc_hugepage(int defrag
)
2251 page
= alloc_pages(alloc_hugepage_gfpmask(defrag
, 0), HPAGE_PMD_ORDER
);
2253 prep_transhuge_page(page
);
2257 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
2262 hpage
= alloc_hugepage(khugepaged_defrag());
2264 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2269 khugepaged_alloc_sleep();
2271 count_vm_event(THP_COLLAPSE_ALLOC
);
2272 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
2277 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
2280 *hpage
= khugepaged_alloc_hugepage(wait
);
2282 if (unlikely(!*hpage
))
2288 static struct page
*
2289 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, struct mm_struct
*mm
,
2290 unsigned long address
, int node
)
2292 up_read(&mm
->mmap_sem
);
2299 static bool hugepage_vma_check(struct vm_area_struct
*vma
)
2301 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
2302 (vma
->vm_flags
& VM_NOHUGEPAGE
))
2304 if (!vma
->anon_vma
|| vma
->vm_ops
)
2306 if (is_vma_temporary_stack(vma
))
2308 VM_BUG_ON_VMA(vma
->vm_flags
& VM_NO_THP
, vma
);
2312 static void collapse_huge_page(struct mm_struct
*mm
,
2313 unsigned long address
,
2314 struct page
**hpage
,
2315 struct vm_area_struct
*vma
,
2321 struct page
*new_page
;
2322 spinlock_t
*pmd_ptl
, *pte_ptl
;
2323 int isolated
= 0, result
= 0;
2324 unsigned long hstart
, hend
;
2325 struct mem_cgroup
*memcg
;
2326 unsigned long mmun_start
; /* For mmu_notifiers */
2327 unsigned long mmun_end
; /* For mmu_notifiers */
2330 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2332 /* Only allocate from the target node */
2333 gfp
= alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE
) |
2336 /* release the mmap_sem read lock. */
2337 new_page
= khugepaged_alloc_page(hpage
, gfp
, mm
, address
, node
);
2339 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
2343 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, gfp
, &memcg
, true))) {
2344 result
= SCAN_CGROUP_CHARGE_FAIL
;
2349 * Prevent all access to pagetables with the exception of
2350 * gup_fast later hanlded by the ptep_clear_flush and the VM
2351 * handled by the anon_vma lock + PG_lock.
2353 down_write(&mm
->mmap_sem
);
2354 if (unlikely(khugepaged_test_exit(mm
))) {
2355 result
= SCAN_ANY_PROCESS
;
2359 vma
= find_vma(mm
, address
);
2361 result
= SCAN_VMA_NULL
;
2364 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2365 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2366 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
) {
2367 result
= SCAN_ADDRESS_RANGE
;
2370 if (!hugepage_vma_check(vma
)) {
2371 result
= SCAN_VMA_CHECK
;
2374 pmd
= mm_find_pmd(mm
, address
);
2376 result
= SCAN_PMD_NULL
;
2380 anon_vma_lock_write(vma
->anon_vma
);
2382 pte
= pte_offset_map(pmd
, address
);
2383 pte_ptl
= pte_lockptr(mm
, pmd
);
2385 mmun_start
= address
;
2386 mmun_end
= address
+ HPAGE_PMD_SIZE
;
2387 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
2388 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
2390 * After this gup_fast can't run anymore. This also removes
2391 * any huge TLB entry from the CPU so we won't allow
2392 * huge and small TLB entries for the same virtual address
2393 * to avoid the risk of CPU bugs in that area.
2395 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
2396 spin_unlock(pmd_ptl
);
2397 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
2400 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
);
2401 spin_unlock(pte_ptl
);
2403 if (unlikely(!isolated
)) {
2406 BUG_ON(!pmd_none(*pmd
));
2408 * We can only use set_pmd_at when establishing
2409 * hugepmds and never for establishing regular pmds that
2410 * points to regular pagetables. Use pmd_populate for that
2412 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
2413 spin_unlock(pmd_ptl
);
2414 anon_vma_unlock_write(vma
->anon_vma
);
2420 * All pages are isolated and locked so anon_vma rmap
2421 * can't run anymore.
2423 anon_vma_unlock_write(vma
->anon_vma
);
2425 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
);
2427 __SetPageUptodate(new_page
);
2428 pgtable
= pmd_pgtable(_pmd
);
2430 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
2431 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
2434 * spin_lock() below is not the equivalent of smp_wmb(), so
2435 * this is needed to avoid the copy_huge_page writes to become
2436 * visible after the set_pmd_at() write.
2441 BUG_ON(!pmd_none(*pmd
));
2442 page_add_new_anon_rmap(new_page
, vma
, address
, true);
2443 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
2444 lru_cache_add_active_or_unevictable(new_page
, vma
);
2445 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
2446 set_pmd_at(mm
, address
, pmd
, _pmd
);
2447 update_mmu_cache_pmd(vma
, address
, pmd
);
2448 spin_unlock(pmd_ptl
);
2452 khugepaged_pages_collapsed
++;
2453 result
= SCAN_SUCCEED
;
2455 up_write(&mm
->mmap_sem
);
2456 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2460 trace_mm_collapse_huge_page(mm
, isolated
, result
);
2463 mem_cgroup_cancel_charge(new_page
, memcg
, true);
2467 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
2468 struct vm_area_struct
*vma
,
2469 unsigned long address
,
2470 struct page
**hpage
)
2474 int ret
= 0, none_or_zero
= 0, result
= 0;
2475 struct page
*page
= NULL
;
2476 unsigned long _address
;
2478 int node
= NUMA_NO_NODE
;
2479 bool writable
= false, referenced
= false;
2481 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2483 pmd
= mm_find_pmd(mm
, address
);
2485 result
= SCAN_PMD_NULL
;
2489 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
2490 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
2491 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2492 _pte
++, _address
+= PAGE_SIZE
) {
2493 pte_t pteval
= *_pte
;
2494 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
2495 if (!userfaultfd_armed(vma
) &&
2496 ++none_or_zero
<= khugepaged_max_ptes_none
) {
2499 result
= SCAN_EXCEED_NONE_PTE
;
2503 if (!pte_present(pteval
)) {
2504 result
= SCAN_PTE_NON_PRESENT
;
2507 if (pte_write(pteval
))
2510 page
= vm_normal_page(vma
, _address
, pteval
);
2511 if (unlikely(!page
)) {
2512 result
= SCAN_PAGE_NULL
;
2516 /* TODO: teach khugepaged to collapse THP mapped with pte */
2517 if (PageCompound(page
)) {
2518 result
= SCAN_PAGE_COMPOUND
;
2523 * Record which node the original page is from and save this
2524 * information to khugepaged_node_load[].
2525 * Khupaged will allocate hugepage from the node has the max
2528 node
= page_to_nid(page
);
2529 if (khugepaged_scan_abort(node
)) {
2530 result
= SCAN_SCAN_ABORT
;
2533 khugepaged_node_load
[node
]++;
2534 if (!PageLRU(page
)) {
2535 result
= SCAN_SCAN_ABORT
;
2538 if (PageLocked(page
)) {
2539 result
= SCAN_PAGE_LOCK
;
2542 if (!PageAnon(page
)) {
2543 result
= SCAN_PAGE_ANON
;
2548 * cannot use mapcount: can't collapse if there's a gup pin.
2549 * The page must only be referenced by the scanned process
2550 * and page swap cache.
2552 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
2553 result
= SCAN_PAGE_COUNT
;
2556 if (pte_young(pteval
) ||
2557 page_is_young(page
) || PageReferenced(page
) ||
2558 mmu_notifier_test_young(vma
->vm_mm
, address
))
2563 result
= SCAN_SUCCEED
;
2566 result
= SCAN_NO_REFERENCED_PAGE
;
2569 result
= SCAN_PAGE_RO
;
2572 pte_unmap_unlock(pte
, ptl
);
2574 node
= khugepaged_find_target_node();
2575 /* collapse_huge_page will return with the mmap_sem released */
2576 collapse_huge_page(mm
, address
, hpage
, vma
, node
);
2579 trace_mm_khugepaged_scan_pmd(mm
, page_to_pfn(page
), writable
, referenced
,
2580 none_or_zero
, result
);
2584 static void collect_mm_slot(struct mm_slot
*mm_slot
)
2586 struct mm_struct
*mm
= mm_slot
->mm
;
2588 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2590 if (khugepaged_test_exit(mm
)) {
2592 hash_del(&mm_slot
->hash
);
2593 list_del(&mm_slot
->mm_node
);
2596 * Not strictly needed because the mm exited already.
2598 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2601 /* khugepaged_mm_lock actually not necessary for the below */
2602 free_mm_slot(mm_slot
);
2607 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2608 struct page
**hpage
)
2609 __releases(&khugepaged_mm_lock
)
2610 __acquires(&khugepaged_mm_lock
)
2612 struct mm_slot
*mm_slot
;
2613 struct mm_struct
*mm
;
2614 struct vm_area_struct
*vma
;
2618 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
2620 if (khugepaged_scan
.mm_slot
)
2621 mm_slot
= khugepaged_scan
.mm_slot
;
2623 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2624 struct mm_slot
, mm_node
);
2625 khugepaged_scan
.address
= 0;
2626 khugepaged_scan
.mm_slot
= mm_slot
;
2628 spin_unlock(&khugepaged_mm_lock
);
2631 down_read(&mm
->mmap_sem
);
2632 if (unlikely(khugepaged_test_exit(mm
)))
2635 vma
= find_vma(mm
, khugepaged_scan
.address
);
2638 for (; vma
; vma
= vma
->vm_next
) {
2639 unsigned long hstart
, hend
;
2642 if (unlikely(khugepaged_test_exit(mm
))) {
2646 if (!hugepage_vma_check(vma
)) {
2651 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2652 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2655 if (khugepaged_scan
.address
> hend
)
2657 if (khugepaged_scan
.address
< hstart
)
2658 khugepaged_scan
.address
= hstart
;
2659 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2661 while (khugepaged_scan
.address
< hend
) {
2664 if (unlikely(khugepaged_test_exit(mm
)))
2665 goto breakouterloop
;
2667 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2668 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2670 ret
= khugepaged_scan_pmd(mm
, vma
,
2671 khugepaged_scan
.address
,
2673 /* move to next address */
2674 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2675 progress
+= HPAGE_PMD_NR
;
2677 /* we released mmap_sem so break loop */
2678 goto breakouterloop_mmap_sem
;
2679 if (progress
>= pages
)
2680 goto breakouterloop
;
2684 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
2685 breakouterloop_mmap_sem
:
2687 spin_lock(&khugepaged_mm_lock
);
2688 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2690 * Release the current mm_slot if this mm is about to die, or
2691 * if we scanned all vmas of this mm.
2693 if (khugepaged_test_exit(mm
) || !vma
) {
2695 * Make sure that if mm_users is reaching zero while
2696 * khugepaged runs here, khugepaged_exit will find
2697 * mm_slot not pointing to the exiting mm.
2699 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2700 khugepaged_scan
.mm_slot
= list_entry(
2701 mm_slot
->mm_node
.next
,
2702 struct mm_slot
, mm_node
);
2703 khugepaged_scan
.address
= 0;
2705 khugepaged_scan
.mm_slot
= NULL
;
2706 khugepaged_full_scans
++;
2709 collect_mm_slot(mm_slot
);
2715 static int khugepaged_has_work(void)
2717 return !list_empty(&khugepaged_scan
.mm_head
) &&
2718 khugepaged_enabled();
2721 static int khugepaged_wait_event(void)
2723 return !list_empty(&khugepaged_scan
.mm_head
) ||
2724 kthread_should_stop();
2727 static void khugepaged_do_scan(void)
2729 struct page
*hpage
= NULL
;
2730 unsigned int progress
= 0, pass_through_head
= 0;
2731 unsigned int pages
= khugepaged_pages_to_scan
;
2734 barrier(); /* write khugepaged_pages_to_scan to local stack */
2736 while (progress
< pages
) {
2737 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2742 if (unlikely(kthread_should_stop() || try_to_freeze()))
2745 spin_lock(&khugepaged_mm_lock
);
2746 if (!khugepaged_scan
.mm_slot
)
2747 pass_through_head
++;
2748 if (khugepaged_has_work() &&
2749 pass_through_head
< 2)
2750 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2754 spin_unlock(&khugepaged_mm_lock
);
2757 if (!IS_ERR_OR_NULL(hpage
))
2761 static void khugepaged_wait_work(void)
2763 if (khugepaged_has_work()) {
2764 if (!khugepaged_scan_sleep_millisecs
)
2767 wait_event_freezable_timeout(khugepaged_wait
,
2768 kthread_should_stop(),
2769 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
));
2773 if (khugepaged_enabled())
2774 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2777 static int khugepaged(void *none
)
2779 struct mm_slot
*mm_slot
;
2782 set_user_nice(current
, MAX_NICE
);
2784 while (!kthread_should_stop()) {
2785 khugepaged_do_scan();
2786 khugepaged_wait_work();
2789 spin_lock(&khugepaged_mm_lock
);
2790 mm_slot
= khugepaged_scan
.mm_slot
;
2791 khugepaged_scan
.mm_slot
= NULL
;
2793 collect_mm_slot(mm_slot
);
2794 spin_unlock(&khugepaged_mm_lock
);
2798 static void __split_huge_zero_page_pmd(struct vm_area_struct
*vma
,
2799 unsigned long haddr
, pmd_t
*pmd
)
2801 struct mm_struct
*mm
= vma
->vm_mm
;
2806 /* leave pmd empty until pte is filled */
2807 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2809 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2810 pmd_populate(mm
, &_pmd
, pgtable
);
2812 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2814 entry
= pfn_pte(my_zero_pfn(haddr
), vma
->vm_page_prot
);
2815 entry
= pte_mkspecial(entry
);
2816 pte
= pte_offset_map(&_pmd
, haddr
);
2817 VM_BUG_ON(!pte_none(*pte
));
2818 set_pte_at(mm
, haddr
, pte
, entry
);
2821 smp_wmb(); /* make pte visible before pmd */
2822 pmd_populate(mm
, pmd
, pgtable
);
2823 put_huge_zero_page();
2826 static void __split_huge_pmd_locked(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2827 unsigned long haddr
, bool freeze
)
2829 struct mm_struct
*mm
= vma
->vm_mm
;
2833 bool young
, write
, dirty
;
2836 VM_BUG_ON(haddr
& ~HPAGE_PMD_MASK
);
2837 VM_BUG_ON_VMA(vma
->vm_start
> haddr
, vma
);
2838 VM_BUG_ON_VMA(vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
, vma
);
2839 VM_BUG_ON(!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
));
2841 count_vm_event(THP_SPLIT_PMD
);
2843 if (vma_is_dax(vma
)) {
2844 pmd_t _pmd
= pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
2845 if (is_huge_zero_pmd(_pmd
))
2846 put_huge_zero_page();
2848 } else if (is_huge_zero_pmd(*pmd
)) {
2849 return __split_huge_zero_page_pmd(vma
, haddr
, pmd
);
2852 page
= pmd_page(*pmd
);
2853 VM_BUG_ON_PAGE(!page_count(page
), page
);
2854 atomic_add(HPAGE_PMD_NR
- 1, &page
->_count
);
2855 write
= pmd_write(*pmd
);
2856 young
= pmd_young(*pmd
);
2857 dirty
= pmd_dirty(*pmd
);
2859 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
2860 pmd_populate(mm
, &_pmd
, pgtable
);
2862 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2865 * Note that NUMA hinting access restrictions are not
2866 * transferred to avoid any possibility of altering
2867 * permissions across VMAs.
2870 swp_entry_t swp_entry
;
2871 swp_entry
= make_migration_entry(page
+ i
, write
);
2872 entry
= swp_entry_to_pte(swp_entry
);
2874 entry
= mk_pte(page
+ i
, vma
->vm_page_prot
);
2875 entry
= maybe_mkwrite(entry
, vma
);
2877 entry
= pte_wrprotect(entry
);
2879 entry
= pte_mkold(entry
);
2882 SetPageDirty(page
+ i
);
2883 pte
= pte_offset_map(&_pmd
, haddr
);
2884 BUG_ON(!pte_none(*pte
));
2885 set_pte_at(mm
, haddr
, pte
, entry
);
2886 atomic_inc(&page
[i
]._mapcount
);
2891 * Set PG_double_map before dropping compound_mapcount to avoid
2892 * false-negative page_mapped().
2894 if (compound_mapcount(page
) > 1 && !TestSetPageDoubleMap(page
)) {
2895 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2896 atomic_inc(&page
[i
]._mapcount
);
2899 if (atomic_add_negative(-1, compound_mapcount_ptr(page
))) {
2900 /* Last compound_mapcount is gone. */
2901 __dec_zone_page_state(page
, NR_ANON_TRANSPARENT_HUGEPAGES
);
2902 if (TestClearPageDoubleMap(page
)) {
2903 /* No need in mapcount reference anymore */
2904 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2905 atomic_dec(&page
[i
]._mapcount
);
2909 smp_wmb(); /* make pte visible before pmd */
2911 * Up to this point the pmd is present and huge and userland has the
2912 * whole access to the hugepage during the split (which happens in
2913 * place). If we overwrite the pmd with the not-huge version pointing
2914 * to the pte here (which of course we could if all CPUs were bug
2915 * free), userland could trigger a small page size TLB miss on the
2916 * small sized TLB while the hugepage TLB entry is still established in
2917 * the huge TLB. Some CPU doesn't like that.
2918 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2919 * 383 on page 93. Intel should be safe but is also warns that it's
2920 * only safe if the permission and cache attributes of the two entries
2921 * loaded in the two TLB is identical (which should be the case here).
2922 * But it is generally safer to never allow small and huge TLB entries
2923 * for the same virtual address to be loaded simultaneously. So instead
2924 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2925 * current pmd notpresent (atomically because here the pmd_trans_huge
2926 * and pmd_trans_splitting must remain set at all times on the pmd
2927 * until the split is complete for this pmd), then we flush the SMP TLB
2928 * and finally we write the non-huge version of the pmd entry with
2931 pmdp_invalidate(vma
, haddr
, pmd
);
2932 pmd_populate(mm
, pmd
, pgtable
);
2935 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
2936 page_remove_rmap(page
+ i
, false);
2942 void __split_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
2943 unsigned long address
)
2946 struct mm_struct
*mm
= vma
->vm_mm
;
2947 struct page
*page
= NULL
;
2948 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
2950 mmu_notifier_invalidate_range_start(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
2951 ptl
= pmd_lock(mm
, pmd
);
2952 if (pmd_trans_huge(*pmd
)) {
2953 page
= pmd_page(*pmd
);
2954 if (PageMlocked(page
))
2958 } else if (!pmd_devmap(*pmd
))
2960 __split_huge_pmd_locked(vma
, pmd
, haddr
, false);
2963 mmu_notifier_invalidate_range_end(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
2966 munlock_vma_page(page
);
2972 static void split_huge_pmd_address(struct vm_area_struct
*vma
,
2973 unsigned long address
)
2979 VM_BUG_ON(!(address
& ~HPAGE_PMD_MASK
));
2981 pgd
= pgd_offset(vma
->vm_mm
, address
);
2982 if (!pgd_present(*pgd
))
2985 pud
= pud_offset(pgd
, address
);
2986 if (!pud_present(*pud
))
2989 pmd
= pmd_offset(pud
, address
);
2990 if (!pmd_present(*pmd
) || (!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
)))
2993 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2994 * materialize from under us.
2996 split_huge_pmd(vma
, pmd
, address
);
2999 void vma_adjust_trans_huge(struct vm_area_struct
*vma
,
3000 unsigned long start
,
3005 * If the new start address isn't hpage aligned and it could
3006 * previously contain an hugepage: check if we need to split
3009 if (start
& ~HPAGE_PMD_MASK
&&
3010 (start
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3011 (start
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3012 split_huge_pmd_address(vma
, start
);
3015 * If the new end address isn't hpage aligned and it could
3016 * previously contain an hugepage: check if we need to split
3019 if (end
& ~HPAGE_PMD_MASK
&&
3020 (end
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
3021 (end
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
3022 split_huge_pmd_address(vma
, end
);
3025 * If we're also updating the vma->vm_next->vm_start, if the new
3026 * vm_next->vm_start isn't page aligned and it could previously
3027 * contain an hugepage: check if we need to split an huge pmd.
3029 if (adjust_next
> 0) {
3030 struct vm_area_struct
*next
= vma
->vm_next
;
3031 unsigned long nstart
= next
->vm_start
;
3032 nstart
+= adjust_next
<< PAGE_SHIFT
;
3033 if (nstart
& ~HPAGE_PMD_MASK
&&
3034 (nstart
& HPAGE_PMD_MASK
) >= next
->vm_start
&&
3035 (nstart
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= next
->vm_end
)
3036 split_huge_pmd_address(next
, nstart
);
3040 static void freeze_page_vma(struct vm_area_struct
*vma
, struct page
*page
,
3041 unsigned long address
)
3043 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
3049 int i
, nr
= HPAGE_PMD_NR
;
3051 /* Skip pages which doesn't belong to the VMA */
3052 if (address
< vma
->vm_start
) {
3053 int off
= (vma
->vm_start
- address
) >> PAGE_SHIFT
;
3056 address
= vma
->vm_start
;
3059 pgd
= pgd_offset(vma
->vm_mm
, address
);
3060 if (!pgd_present(*pgd
))
3062 pud
= pud_offset(pgd
, address
);
3063 if (!pud_present(*pud
))
3065 pmd
= pmd_offset(pud
, address
);
3066 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
3067 if (!pmd_present(*pmd
)) {
3071 if (pmd_trans_huge(*pmd
)) {
3072 if (page
== pmd_page(*pmd
))
3073 __split_huge_pmd_locked(vma
, pmd
, haddr
, true);
3079 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, address
, &ptl
);
3080 for (i
= 0; i
< nr
; i
++, address
+= PAGE_SIZE
, page
++, pte
++) {
3081 pte_t entry
, swp_pte
;
3082 swp_entry_t swp_entry
;
3085 * We've just crossed page table boundary: need to map next one.
3086 * It can happen if THP was mremaped to non PMD-aligned address.
3088 if (unlikely(address
== haddr
+ HPAGE_PMD_SIZE
)) {
3089 pte_unmap_unlock(pte
- 1, ptl
);
3090 pmd
= mm_find_pmd(vma
->vm_mm
, address
);
3093 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
,
3097 if (!pte_present(*pte
))
3099 if (page_to_pfn(page
) != pte_pfn(*pte
))
3101 flush_cache_page(vma
, address
, page_to_pfn(page
));
3102 entry
= ptep_clear_flush(vma
, address
, pte
);
3103 if (pte_dirty(entry
))
3105 swp_entry
= make_migration_entry(page
, pte_write(entry
));
3106 swp_pte
= swp_entry_to_pte(swp_entry
);
3107 if (pte_soft_dirty(entry
))
3108 swp_pte
= pte_swp_mksoft_dirty(swp_pte
);
3109 set_pte_at(vma
->vm_mm
, address
, pte
, swp_pte
);
3110 page_remove_rmap(page
, false);
3113 pte_unmap_unlock(pte
- 1, ptl
);
3116 static void freeze_page(struct anon_vma
*anon_vma
, struct page
*page
)
3118 struct anon_vma_chain
*avc
;
3119 pgoff_t pgoff
= page_to_pgoff(page
);
3121 VM_BUG_ON_PAGE(!PageHead(page
), page
);
3123 anon_vma_interval_tree_foreach(avc
, &anon_vma
->rb_root
, pgoff
,
3124 pgoff
+ HPAGE_PMD_NR
- 1) {
3125 unsigned long address
= __vma_address(page
, avc
->vma
);
3127 mmu_notifier_invalidate_range_start(avc
->vma
->vm_mm
,
3128 address
, address
+ HPAGE_PMD_SIZE
);
3129 freeze_page_vma(avc
->vma
, page
, address
);
3130 mmu_notifier_invalidate_range_end(avc
->vma
->vm_mm
,
3131 address
, address
+ HPAGE_PMD_SIZE
);
3135 static void unfreeze_page_vma(struct vm_area_struct
*vma
, struct page
*page
,
3136 unsigned long address
)
3141 swp_entry_t swp_entry
;
3142 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
3143 int i
, nr
= HPAGE_PMD_NR
;
3145 /* Skip pages which doesn't belong to the VMA */
3146 if (address
< vma
->vm_start
) {
3147 int off
= (vma
->vm_start
- address
) >> PAGE_SHIFT
;
3150 address
= vma
->vm_start
;
3153 pmd
= mm_find_pmd(vma
->vm_mm
, address
);
3157 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
, address
, &ptl
);
3158 for (i
= 0; i
< nr
; i
++, address
+= PAGE_SIZE
, page
++, pte
++) {
3160 * We've just crossed page table boundary: need to map next one.
3161 * It can happen if THP was mremaped to non-PMD aligned address.
3163 if (unlikely(address
== haddr
+ HPAGE_PMD_SIZE
)) {
3164 pte_unmap_unlock(pte
- 1, ptl
);
3165 pmd
= mm_find_pmd(vma
->vm_mm
, address
);
3168 pte
= pte_offset_map_lock(vma
->vm_mm
, pmd
,
3172 if (!is_swap_pte(*pte
))
3175 swp_entry
= pte_to_swp_entry(*pte
);
3176 if (!is_migration_entry(swp_entry
))
3178 if (migration_entry_to_page(swp_entry
) != page
)
3182 page_add_anon_rmap(page
, vma
, address
, false);
3184 entry
= pte_mkold(mk_pte(page
, vma
->vm_page_prot
));
3185 if (PageDirty(page
))
3186 entry
= pte_mkdirty(entry
);
3187 if (is_write_migration_entry(swp_entry
))
3188 entry
= maybe_mkwrite(entry
, vma
);
3190 flush_dcache_page(page
);
3191 set_pte_at(vma
->vm_mm
, address
, pte
, entry
);
3193 /* No need to invalidate - it was non-present before */
3194 update_mmu_cache(vma
, address
, pte
);
3196 pte_unmap_unlock(pte
- 1, ptl
);
3199 static void unfreeze_page(struct anon_vma
*anon_vma
, struct page
*page
)
3201 struct anon_vma_chain
*avc
;
3202 pgoff_t pgoff
= page_to_pgoff(page
);
3204 anon_vma_interval_tree_foreach(avc
, &anon_vma
->rb_root
,
3205 pgoff
, pgoff
+ HPAGE_PMD_NR
- 1) {
3206 unsigned long address
= __vma_address(page
, avc
->vma
);
3208 mmu_notifier_invalidate_range_start(avc
->vma
->vm_mm
,
3209 address
, address
+ HPAGE_PMD_SIZE
);
3210 unfreeze_page_vma(avc
->vma
, page
, address
);
3211 mmu_notifier_invalidate_range_end(avc
->vma
->vm_mm
,
3212 address
, address
+ HPAGE_PMD_SIZE
);
3216 static int __split_huge_page_tail(struct page
*head
, int tail
,
3217 struct lruvec
*lruvec
, struct list_head
*list
)
3220 struct page
*page_tail
= head
+ tail
;
3222 mapcount
= atomic_read(&page_tail
->_mapcount
) + 1;
3223 VM_BUG_ON_PAGE(atomic_read(&page_tail
->_count
) != 0, page_tail
);
3226 * tail_page->_count is zero and not changing from under us. But
3227 * get_page_unless_zero() may be running from under us on the
3228 * tail_page. If we used atomic_set() below instead of atomic_add(), we
3229 * would then run atomic_set() concurrently with
3230 * get_page_unless_zero(), and atomic_set() is implemented in C not
3231 * using locked ops. spin_unlock on x86 sometime uses locked ops
3232 * because of PPro errata 66, 92, so unless somebody can guarantee
3233 * atomic_set() here would be safe on all archs (and not only on x86),
3234 * it's safer to use atomic_add().
3236 atomic_add(mapcount
+ 1, &page_tail
->_count
);
3239 page_tail
->flags
&= ~PAGE_FLAGS_CHECK_AT_PREP
;
3240 page_tail
->flags
|= (head
->flags
&
3241 ((1L << PG_referenced
) |
3242 (1L << PG_swapbacked
) |
3243 (1L << PG_mlocked
) |
3244 (1L << PG_uptodate
) |
3247 (1L << PG_unevictable
) |
3251 * After clearing PageTail the gup refcount can be released.
3252 * Page flags also must be visible before we make the page non-compound.
3256 clear_compound_head(page_tail
);
3258 if (page_is_young(head
))
3259 set_page_young(page_tail
);
3260 if (page_is_idle(head
))
3261 set_page_idle(page_tail
);
3263 /* ->mapping in first tail page is compound_mapcount */
3264 VM_BUG_ON_PAGE(tail
> 2 && page_tail
->mapping
!= TAIL_MAPPING
,
3266 page_tail
->mapping
= head
->mapping
;
3268 page_tail
->index
= head
->index
+ tail
;
3269 page_cpupid_xchg_last(page_tail
, page_cpupid_last(head
));
3270 lru_add_page_tail(head
, page_tail
, lruvec
, list
);
3275 static void __split_huge_page(struct page
*page
, struct list_head
*list
)
3277 struct page
*head
= compound_head(page
);
3278 struct zone
*zone
= page_zone(head
);
3279 struct lruvec
*lruvec
;
3280 int i
, tail_mapcount
;
3282 /* prevent PageLRU to go away from under us, and freeze lru stats */
3283 spin_lock_irq(&zone
->lru_lock
);
3284 lruvec
= mem_cgroup_page_lruvec(head
, zone
);
3286 /* complete memcg works before add pages to LRU */
3287 mem_cgroup_split_huge_fixup(head
);
3290 for (i
= HPAGE_PMD_NR
- 1; i
>= 1; i
--)
3291 tail_mapcount
+= __split_huge_page_tail(head
, i
, lruvec
, list
);
3292 atomic_sub(tail_mapcount
, &head
->_count
);
3294 ClearPageCompound(head
);
3295 spin_unlock_irq(&zone
->lru_lock
);
3297 unfreeze_page(page_anon_vma(head
), head
);
3299 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
3300 struct page
*subpage
= head
+ i
;
3301 if (subpage
== page
)
3303 unlock_page(subpage
);
3306 * Subpages may be freed if there wasn't any mapping
3307 * like if add_to_swap() is running on a lru page that
3308 * had its mapping zapped. And freeing these pages
3309 * requires taking the lru_lock so we do the put_page
3310 * of the tail pages after the split is complete.
3316 int total_mapcount(struct page
*page
)
3320 VM_BUG_ON_PAGE(PageTail(page
), page
);
3322 if (likely(!PageCompound(page
)))
3323 return atomic_read(&page
->_mapcount
) + 1;
3325 ret
= compound_mapcount(page
);
3328 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
3329 ret
+= atomic_read(&page
[i
]._mapcount
) + 1;
3330 if (PageDoubleMap(page
))
3331 ret
-= HPAGE_PMD_NR
;
3336 * This function splits huge page into normal pages. @page can point to any
3337 * subpage of huge page to split. Split doesn't change the position of @page.
3339 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3340 * The huge page must be locked.
3342 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3344 * Both head page and tail pages will inherit mapping, flags, and so on from
3347 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3348 * they are not mapped.
3350 * Returns 0 if the hugepage is split successfully.
3351 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3354 int split_huge_page_to_list(struct page
*page
, struct list_head
*list
)
3356 struct page
*head
= compound_head(page
);
3357 struct anon_vma
*anon_vma
;
3358 int count
, mapcount
, ret
;
3361 VM_BUG_ON_PAGE(is_huge_zero_page(page
), page
);
3362 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
3363 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
3364 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
3365 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
3368 * The caller does not necessarily hold an mmap_sem that would prevent
3369 * the anon_vma disappearing so we first we take a reference to it
3370 * and then lock the anon_vma for write. This is similar to
3371 * page_lock_anon_vma_read except the write lock is taken to serialise
3372 * against parallel split or collapse operations.
3374 anon_vma
= page_get_anon_vma(head
);
3379 anon_vma_lock_write(anon_vma
);
3382 * Racy check if we can split the page, before freeze_page() will
3385 if (total_mapcount(head
) != page_count(head
) - 1) {
3390 mlocked
= PageMlocked(page
);
3391 freeze_page(anon_vma
, head
);
3392 VM_BUG_ON_PAGE(compound_mapcount(head
), head
);
3394 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3398 /* Prevent deferred_split_scan() touching ->_count */
3399 spin_lock(&split_queue_lock
);
3400 count
= page_count(head
);
3401 mapcount
= total_mapcount(head
);
3402 if (!mapcount
&& count
== 1) {
3403 if (!list_empty(page_deferred_list(head
))) {
3405 list_del(page_deferred_list(head
));
3407 spin_unlock(&split_queue_lock
);
3408 __split_huge_page(page
, list
);
3410 } else if (IS_ENABLED(CONFIG_DEBUG_VM
) && mapcount
) {
3411 spin_unlock(&split_queue_lock
);
3412 pr_alert("total_mapcount: %u, page_count(): %u\n",
3415 dump_page(head
, NULL
);
3416 dump_page(page
, "total_mapcount(head) > 0");
3419 spin_unlock(&split_queue_lock
);
3420 unfreeze_page(anon_vma
, head
);
3425 anon_vma_unlock_write(anon_vma
);
3426 put_anon_vma(anon_vma
);
3428 count_vm_event(!ret
? THP_SPLIT_PAGE
: THP_SPLIT_PAGE_FAILED
);
3432 void free_transhuge_page(struct page
*page
)
3434 unsigned long flags
;
3436 spin_lock_irqsave(&split_queue_lock
, flags
);
3437 if (!list_empty(page_deferred_list(page
))) {
3439 list_del(page_deferred_list(page
));
3441 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3442 free_compound_page(page
);
3445 void deferred_split_huge_page(struct page
*page
)
3447 unsigned long flags
;
3449 VM_BUG_ON_PAGE(!PageTransHuge(page
), page
);
3451 spin_lock_irqsave(&split_queue_lock
, flags
);
3452 if (list_empty(page_deferred_list(page
))) {
3453 list_add_tail(page_deferred_list(page
), &split_queue
);
3456 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3459 static unsigned long deferred_split_count(struct shrinker
*shrink
,
3460 struct shrink_control
*sc
)
3463 * Split a page from split_queue will free up at least one page,
3464 * at most HPAGE_PMD_NR - 1. We don't track exact number.
3465 * Let's use HPAGE_PMD_NR / 2 as ballpark.
3467 return ACCESS_ONCE(split_queue_len
) * HPAGE_PMD_NR
/ 2;
3470 static unsigned long deferred_split_scan(struct shrinker
*shrink
,
3471 struct shrink_control
*sc
)
3473 unsigned long flags
;
3474 LIST_HEAD(list
), *pos
, *next
;
3478 spin_lock_irqsave(&split_queue_lock
, flags
);
3479 list_splice_init(&split_queue
, &list
);
3481 /* Take pin on all head pages to avoid freeing them under us */
3482 list_for_each_safe(pos
, next
, &list
) {
3483 page
= list_entry((void *)pos
, struct page
, mapping
);
3484 page
= compound_head(page
);
3485 /* race with put_compound_page() */
3486 if (!get_page_unless_zero(page
)) {
3487 list_del_init(page_deferred_list(page
));
3491 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3493 list_for_each_safe(pos
, next
, &list
) {
3494 page
= list_entry((void *)pos
, struct page
, mapping
);
3496 /* split_huge_page() removes page from list on success */
3497 if (!split_huge_page(page
))
3503 spin_lock_irqsave(&split_queue_lock
, flags
);
3504 list_splice_tail(&list
, &split_queue
);
3505 spin_unlock_irqrestore(&split_queue_lock
, flags
);
3507 return split
* HPAGE_PMD_NR
/ 2;
3510 static struct shrinker deferred_split_shrinker
= {
3511 .count_objects
= deferred_split_count
,
3512 .scan_objects
= deferred_split_scan
,
3513 .seeks
= DEFAULT_SEEKS
,
3516 #ifdef CONFIG_DEBUG_FS
3517 static int split_huge_pages_set(void *data
, u64 val
)
3521 unsigned long pfn
, max_zone_pfn
;
3522 unsigned long total
= 0, split
= 0;
3527 for_each_populated_zone(zone
) {
3528 max_zone_pfn
= zone_end_pfn(zone
);
3529 for (pfn
= zone
->zone_start_pfn
; pfn
< max_zone_pfn
; pfn
++) {
3530 if (!pfn_valid(pfn
))
3533 page
= pfn_to_page(pfn
);
3534 if (!get_page_unless_zero(page
))
3537 if (zone
!= page_zone(page
))
3540 if (!PageHead(page
) || !PageAnon(page
) ||
3546 if (!split_huge_page(page
))
3554 pr_info("%lu of %lu THP split", split
, total
);
3558 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops
, NULL
, split_huge_pages_set
,
3561 static int __init
split_huge_pages_debugfs(void)
3565 ret
= debugfs_create_file("split_huge_pages", 0644, NULL
, NULL
,
3566 &split_huge_pages_fops
);
3568 pr_warn("Failed to create split_huge_pages in debugfs");
3571 late_initcall(split_huge_pages_debugfs
);