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.
9 #include <linux/sched.h>
10 #include <linux/highmem.h>
11 #include <linux/hugetlb.h>
12 #include <linux/mmu_notifier.h>
13 #include <linux/rmap.h>
14 #include <linux/swap.h>
15 #include <linux/mm_inline.h>
16 #include <linux/kthread.h>
17 #include <linux/khugepaged.h>
18 #include <linux/freezer.h>
19 #include <linux/mman.h>
21 #include <asm/pgalloc.h>
25 * By default transparent hugepage support is enabled for all mappings
26 * and khugepaged scans all mappings. Defrag is only invoked by
27 * khugepaged hugepage allocations and by page faults inside
28 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
31 unsigned long transparent_hugepage_flags __read_mostly
=
32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
33 (1<<TRANSPARENT_HUGEPAGE_FLAG
)|
35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
)|
38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
)|
39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
41 /* default scan 8*512 pte (or vmas) every 30 second */
42 static unsigned int khugepaged_pages_to_scan __read_mostly
= HPAGE_PMD_NR
*8;
43 static unsigned int khugepaged_pages_collapsed
;
44 static unsigned int khugepaged_full_scans
;
45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly
= 10000;
46 /* during fragmentation poll the hugepage allocator once every minute */
47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly
= 60000;
48 static struct task_struct
*khugepaged_thread __read_mostly
;
49 static DEFINE_MUTEX(khugepaged_mutex
);
50 static DEFINE_SPINLOCK(khugepaged_mm_lock
);
51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait
);
53 * default collapse hugepages if there is at least one pte mapped like
54 * it would have happened if the vma was large enough during page
57 static unsigned int khugepaged_max_ptes_none __read_mostly
= HPAGE_PMD_NR
-1;
59 static int khugepaged(void *none
);
60 static int mm_slots_hash_init(void);
61 static int khugepaged_slab_init(void);
62 static void khugepaged_slab_free(void);
64 #define MM_SLOTS_HASH_HEADS 1024
65 static struct hlist_head
*mm_slots_hash __read_mostly
;
66 static struct kmem_cache
*mm_slot_cache __read_mostly
;
69 * struct mm_slot - hash lookup from mm to mm_slot
70 * @hash: hash collision list
71 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
72 * @mm: the mm that this information is valid for
75 struct hlist_node hash
;
76 struct list_head mm_node
;
81 * struct khugepaged_scan - cursor for scanning
82 * @mm_head: the head of the mm list to scan
83 * @mm_slot: the current mm_slot we are scanning
84 * @address: the next address inside that to be scanned
86 * There is only the one khugepaged_scan instance of this cursor structure.
88 struct khugepaged_scan
{
89 struct list_head mm_head
;
90 struct mm_slot
*mm_slot
;
91 unsigned long address
;
93 static struct khugepaged_scan khugepaged_scan
= {
94 .mm_head
= LIST_HEAD_INIT(khugepaged_scan
.mm_head
),
98 static int set_recommended_min_free_kbytes(void)
102 unsigned long recommended_min
;
103 extern int min_free_kbytes
;
105 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG
,
106 &transparent_hugepage_flags
) &&
107 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
108 &transparent_hugepage_flags
))
111 for_each_populated_zone(zone
)
114 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
115 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
118 * Make sure that on average at least two pageblocks are almost free
119 * of another type, one for a migratetype to fall back to and a
120 * second to avoid subsequent fallbacks of other types There are 3
121 * MIGRATE_TYPES we care about.
123 recommended_min
+= pageblock_nr_pages
* nr_zones
*
124 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
126 /* don't ever allow to reserve more than 5% of the lowmem */
127 recommended_min
= min(recommended_min
,
128 (unsigned long) nr_free_buffer_pages() / 20);
129 recommended_min
<<= (PAGE_SHIFT
-10);
131 if (recommended_min
> min_free_kbytes
)
132 min_free_kbytes
= recommended_min
;
133 setup_per_zone_wmarks();
136 late_initcall(set_recommended_min_free_kbytes
);
138 static int start_khugepaged(void)
141 if (khugepaged_enabled()) {
143 if (unlikely(!mm_slot_cache
|| !mm_slots_hash
)) {
147 mutex_lock(&khugepaged_mutex
);
148 if (!khugepaged_thread
)
149 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
151 if (unlikely(IS_ERR(khugepaged_thread
))) {
153 "khugepaged: kthread_run(khugepaged) failed\n");
154 err
= PTR_ERR(khugepaged_thread
);
155 khugepaged_thread
= NULL
;
157 wakeup
= !list_empty(&khugepaged_scan
.mm_head
);
158 mutex_unlock(&khugepaged_mutex
);
160 wake_up_interruptible(&khugepaged_wait
);
162 set_recommended_min_free_kbytes();
165 wake_up_interruptible(&khugepaged_wait
);
172 static ssize_t
double_flag_show(struct kobject
*kobj
,
173 struct kobj_attribute
*attr
, char *buf
,
174 enum transparent_hugepage_flag enabled
,
175 enum transparent_hugepage_flag req_madv
)
177 if (test_bit(enabled
, &transparent_hugepage_flags
)) {
178 VM_BUG_ON(test_bit(req_madv
, &transparent_hugepage_flags
));
179 return sprintf(buf
, "[always] madvise never\n");
180 } else if (test_bit(req_madv
, &transparent_hugepage_flags
))
181 return sprintf(buf
, "always [madvise] never\n");
183 return sprintf(buf
, "always madvise [never]\n");
185 static ssize_t
double_flag_store(struct kobject
*kobj
,
186 struct kobj_attribute
*attr
,
187 const char *buf
, size_t count
,
188 enum transparent_hugepage_flag enabled
,
189 enum transparent_hugepage_flag req_madv
)
191 if (!memcmp("always", buf
,
192 min(sizeof("always")-1, count
))) {
193 set_bit(enabled
, &transparent_hugepage_flags
);
194 clear_bit(req_madv
, &transparent_hugepage_flags
);
195 } else if (!memcmp("madvise", buf
,
196 min(sizeof("madvise")-1, count
))) {
197 clear_bit(enabled
, &transparent_hugepage_flags
);
198 set_bit(req_madv
, &transparent_hugepage_flags
);
199 } else if (!memcmp("never", buf
,
200 min(sizeof("never")-1, count
))) {
201 clear_bit(enabled
, &transparent_hugepage_flags
);
202 clear_bit(req_madv
, &transparent_hugepage_flags
);
209 static ssize_t
enabled_show(struct kobject
*kobj
,
210 struct kobj_attribute
*attr
, char *buf
)
212 return double_flag_show(kobj
, attr
, buf
,
213 TRANSPARENT_HUGEPAGE_FLAG
,
214 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
216 static ssize_t
enabled_store(struct kobject
*kobj
,
217 struct kobj_attribute
*attr
,
218 const char *buf
, size_t count
)
222 ret
= double_flag_store(kobj
, attr
, buf
, count
,
223 TRANSPARENT_HUGEPAGE_FLAG
,
224 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
227 int err
= start_khugepaged();
233 (test_bit(TRANSPARENT_HUGEPAGE_FLAG
,
234 &transparent_hugepage_flags
) ||
235 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
236 &transparent_hugepage_flags
)))
237 set_recommended_min_free_kbytes();
241 static struct kobj_attribute enabled_attr
=
242 __ATTR(enabled
, 0644, enabled_show
, enabled_store
);
244 static ssize_t
single_flag_show(struct kobject
*kobj
,
245 struct kobj_attribute
*attr
, char *buf
,
246 enum transparent_hugepage_flag flag
)
248 return sprintf(buf
, "%d\n",
249 !!test_bit(flag
, &transparent_hugepage_flags
));
252 static ssize_t
single_flag_store(struct kobject
*kobj
,
253 struct kobj_attribute
*attr
,
254 const char *buf
, size_t count
,
255 enum transparent_hugepage_flag flag
)
260 ret
= kstrtoul(buf
, 10, &value
);
267 set_bit(flag
, &transparent_hugepage_flags
);
269 clear_bit(flag
, &transparent_hugepage_flags
);
275 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
276 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
277 * memory just to allocate one more hugepage.
279 static ssize_t
defrag_show(struct kobject
*kobj
,
280 struct kobj_attribute
*attr
, char *buf
)
282 return double_flag_show(kobj
, attr
, buf
,
283 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
,
284 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
286 static ssize_t
defrag_store(struct kobject
*kobj
,
287 struct kobj_attribute
*attr
,
288 const char *buf
, size_t count
)
290 return double_flag_store(kobj
, attr
, buf
, count
,
291 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG
,
292 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
294 static struct kobj_attribute defrag_attr
=
295 __ATTR(defrag
, 0644, defrag_show
, defrag_store
);
297 #ifdef CONFIG_DEBUG_VM
298 static ssize_t
debug_cow_show(struct kobject
*kobj
,
299 struct kobj_attribute
*attr
, char *buf
)
301 return single_flag_show(kobj
, attr
, buf
,
302 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
304 static ssize_t
debug_cow_store(struct kobject
*kobj
,
305 struct kobj_attribute
*attr
,
306 const char *buf
, size_t count
)
308 return single_flag_store(kobj
, attr
, buf
, count
,
309 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG
);
311 static struct kobj_attribute debug_cow_attr
=
312 __ATTR(debug_cow
, 0644, debug_cow_show
, debug_cow_store
);
313 #endif /* CONFIG_DEBUG_VM */
315 static struct attribute
*hugepage_attr
[] = {
318 #ifdef CONFIG_DEBUG_VM
319 &debug_cow_attr
.attr
,
324 static struct attribute_group hugepage_attr_group
= {
325 .attrs
= hugepage_attr
,
328 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
329 struct kobj_attribute
*attr
,
332 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
335 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
336 struct kobj_attribute
*attr
,
337 const char *buf
, size_t count
)
342 err
= strict_strtoul(buf
, 10, &msecs
);
343 if (err
|| msecs
> UINT_MAX
)
346 khugepaged_scan_sleep_millisecs
= msecs
;
347 wake_up_interruptible(&khugepaged_wait
);
351 static struct kobj_attribute scan_sleep_millisecs_attr
=
352 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
353 scan_sleep_millisecs_store
);
355 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
356 struct kobj_attribute
*attr
,
359 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
362 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
363 struct kobj_attribute
*attr
,
364 const char *buf
, size_t count
)
369 err
= strict_strtoul(buf
, 10, &msecs
);
370 if (err
|| msecs
> UINT_MAX
)
373 khugepaged_alloc_sleep_millisecs
= msecs
;
374 wake_up_interruptible(&khugepaged_wait
);
378 static struct kobj_attribute alloc_sleep_millisecs_attr
=
379 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
380 alloc_sleep_millisecs_store
);
382 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
383 struct kobj_attribute
*attr
,
386 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
388 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
389 struct kobj_attribute
*attr
,
390 const char *buf
, size_t count
)
395 err
= strict_strtoul(buf
, 10, &pages
);
396 if (err
|| !pages
|| pages
> UINT_MAX
)
399 khugepaged_pages_to_scan
= pages
;
403 static struct kobj_attribute pages_to_scan_attr
=
404 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
405 pages_to_scan_store
);
407 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
408 struct kobj_attribute
*attr
,
411 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
413 static struct kobj_attribute pages_collapsed_attr
=
414 __ATTR_RO(pages_collapsed
);
416 static ssize_t
full_scans_show(struct kobject
*kobj
,
417 struct kobj_attribute
*attr
,
420 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
422 static struct kobj_attribute full_scans_attr
=
423 __ATTR_RO(full_scans
);
425 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
426 struct kobj_attribute
*attr
, char *buf
)
428 return single_flag_show(kobj
, attr
, buf
,
429 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
431 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
432 struct kobj_attribute
*attr
,
433 const char *buf
, size_t count
)
435 return single_flag_store(kobj
, attr
, buf
, count
,
436 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
438 static struct kobj_attribute khugepaged_defrag_attr
=
439 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
440 khugepaged_defrag_store
);
443 * max_ptes_none controls if khugepaged should collapse hugepages over
444 * any unmapped ptes in turn potentially increasing the memory
445 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
446 * reduce the available free memory in the system as it
447 * runs. Increasing max_ptes_none will instead potentially reduce the
448 * free memory in the system during the khugepaged scan.
450 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
451 struct kobj_attribute
*attr
,
454 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
456 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
457 struct kobj_attribute
*attr
,
458 const char *buf
, size_t count
)
461 unsigned long max_ptes_none
;
463 err
= strict_strtoul(buf
, 10, &max_ptes_none
);
464 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
467 khugepaged_max_ptes_none
= max_ptes_none
;
471 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
472 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
473 khugepaged_max_ptes_none_store
);
475 static struct attribute
*khugepaged_attr
[] = {
476 &khugepaged_defrag_attr
.attr
,
477 &khugepaged_max_ptes_none_attr
.attr
,
478 &pages_to_scan_attr
.attr
,
479 &pages_collapsed_attr
.attr
,
480 &full_scans_attr
.attr
,
481 &scan_sleep_millisecs_attr
.attr
,
482 &alloc_sleep_millisecs_attr
.attr
,
486 static struct attribute_group khugepaged_attr_group
= {
487 .attrs
= khugepaged_attr
,
488 .name
= "khugepaged",
491 static int __init
hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
495 *hugepage_kobj
= kobject_create_and_add("transparent_hugepage", mm_kobj
);
496 if (unlikely(!*hugepage_kobj
)) {
497 printk(KERN_ERR
"hugepage: failed kobject create\n");
501 err
= sysfs_create_group(*hugepage_kobj
, &hugepage_attr_group
);
503 printk(KERN_ERR
"hugepage: failed register hugeage group\n");
507 err
= sysfs_create_group(*hugepage_kobj
, &khugepaged_attr_group
);
509 printk(KERN_ERR
"hugepage: failed register hugeage group\n");
510 goto remove_hp_group
;
516 sysfs_remove_group(*hugepage_kobj
, &hugepage_attr_group
);
518 kobject_put(*hugepage_kobj
);
522 static void __init
hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
524 sysfs_remove_group(hugepage_kobj
, &khugepaged_attr_group
);
525 sysfs_remove_group(hugepage_kobj
, &hugepage_attr_group
);
526 kobject_put(hugepage_kobj
);
529 static inline int hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
534 static inline void hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
537 #endif /* CONFIG_SYSFS */
539 static int __init
hugepage_init(void)
542 struct kobject
*hugepage_kobj
;
544 if (!has_transparent_hugepage()) {
545 transparent_hugepage_flags
= 0;
549 err
= hugepage_init_sysfs(&hugepage_kobj
);
553 err
= khugepaged_slab_init();
557 err
= mm_slots_hash_init();
559 khugepaged_slab_free();
564 * By default disable transparent hugepages on smaller systems,
565 * where the extra memory used could hurt more than TLB overhead
566 * is likely to save. The admin can still enable it through /sys.
568 if (totalram_pages
< (512 << (20 - PAGE_SHIFT
)))
569 transparent_hugepage_flags
= 0;
573 set_recommended_min_free_kbytes();
577 hugepage_exit_sysfs(hugepage_kobj
);
580 module_init(hugepage_init
)
582 static int __init
setup_transparent_hugepage(char *str
)
587 if (!strcmp(str
, "always")) {
588 set_bit(TRANSPARENT_HUGEPAGE_FLAG
,
589 &transparent_hugepage_flags
);
590 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
591 &transparent_hugepage_flags
);
593 } else if (!strcmp(str
, "madvise")) {
594 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
595 &transparent_hugepage_flags
);
596 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
597 &transparent_hugepage_flags
);
599 } else if (!strcmp(str
, "never")) {
600 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
601 &transparent_hugepage_flags
);
602 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
603 &transparent_hugepage_flags
);
609 "transparent_hugepage= cannot parse, ignored\n");
612 __setup("transparent_hugepage=", setup_transparent_hugepage
);
614 static void prepare_pmd_huge_pte(pgtable_t pgtable
,
615 struct mm_struct
*mm
)
617 assert_spin_locked(&mm
->page_table_lock
);
620 if (!mm
->pmd_huge_pte
)
621 INIT_LIST_HEAD(&pgtable
->lru
);
623 list_add(&pgtable
->lru
, &mm
->pmd_huge_pte
->lru
);
624 mm
->pmd_huge_pte
= pgtable
;
627 static inline pmd_t
maybe_pmd_mkwrite(pmd_t pmd
, struct vm_area_struct
*vma
)
629 if (likely(vma
->vm_flags
& VM_WRITE
))
630 pmd
= pmd_mkwrite(pmd
);
634 static int __do_huge_pmd_anonymous_page(struct mm_struct
*mm
,
635 struct vm_area_struct
*vma
,
636 unsigned long haddr
, pmd_t
*pmd
,
642 VM_BUG_ON(!PageCompound(page
));
643 pgtable
= pte_alloc_one(mm
, haddr
);
644 if (unlikely(!pgtable
)) {
645 mem_cgroup_uncharge_page(page
);
650 clear_huge_page(page
, haddr
, HPAGE_PMD_NR
);
651 __SetPageUptodate(page
);
653 spin_lock(&mm
->page_table_lock
);
654 if (unlikely(!pmd_none(*pmd
))) {
655 spin_unlock(&mm
->page_table_lock
);
656 mem_cgroup_uncharge_page(page
);
658 pte_free(mm
, pgtable
);
661 entry
= mk_pmd(page
, vma
->vm_page_prot
);
662 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
663 entry
= pmd_mkhuge(entry
);
665 * The spinlocking to take the lru_lock inside
666 * page_add_new_anon_rmap() acts as a full memory
667 * barrier to be sure clear_huge_page writes become
668 * visible after the set_pmd_at() write.
670 page_add_new_anon_rmap(page
, vma
, haddr
);
671 set_pmd_at(mm
, haddr
, pmd
, entry
);
672 prepare_pmd_huge_pte(pgtable
, mm
);
673 add_mm_counter(mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
674 spin_unlock(&mm
->page_table_lock
);
680 static inline gfp_t
alloc_hugepage_gfpmask(int defrag
, gfp_t extra_gfp
)
682 return (GFP_TRANSHUGE
& ~(defrag
? 0 : __GFP_WAIT
)) | extra_gfp
;
685 static inline struct page
*alloc_hugepage_vma(int defrag
,
686 struct vm_area_struct
*vma
,
687 unsigned long haddr
, int nd
,
690 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag
, extra_gfp
),
691 HPAGE_PMD_ORDER
, vma
, haddr
, nd
);
695 static inline struct page
*alloc_hugepage(int defrag
)
697 return alloc_pages(alloc_hugepage_gfpmask(defrag
, 0),
702 int do_huge_pmd_anonymous_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
703 unsigned long address
, pmd_t
*pmd
,
707 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
710 if (haddr
>= vma
->vm_start
&& haddr
+ HPAGE_PMD_SIZE
<= vma
->vm_end
) {
711 if (unlikely(anon_vma_prepare(vma
)))
713 if (unlikely(khugepaged_enter(vma
)))
715 page
= alloc_hugepage_vma(transparent_hugepage_defrag(vma
),
716 vma
, haddr
, numa_node_id(), 0);
717 if (unlikely(!page
)) {
718 count_vm_event(THP_FAULT_FALLBACK
);
721 count_vm_event(THP_FAULT_ALLOC
);
722 if (unlikely(mem_cgroup_newpage_charge(page
, mm
, GFP_KERNEL
))) {
727 return __do_huge_pmd_anonymous_page(mm
, vma
, haddr
, pmd
, page
);
731 * Use __pte_alloc instead of pte_alloc_map, because we can't
732 * run pte_offset_map on the pmd, if an huge pmd could
733 * materialize from under us from a different thread.
735 if (unlikely(__pte_alloc(mm
, vma
, pmd
, address
)))
737 /* if an huge pmd materialized from under us just retry later */
738 if (unlikely(pmd_trans_huge(*pmd
)))
741 * A regular pmd is established and it can't morph into a huge pmd
742 * from under us anymore at this point because we hold the mmap_sem
743 * read mode and khugepaged takes it in write mode. So now it's
744 * safe to run pte_offset_map().
746 pte
= pte_offset_map(pmd
, address
);
747 return handle_pte_fault(mm
, vma
, address
, pte
, pmd
, flags
);
750 int copy_huge_pmd(struct mm_struct
*dst_mm
, struct mm_struct
*src_mm
,
751 pmd_t
*dst_pmd
, pmd_t
*src_pmd
, unsigned long addr
,
752 struct vm_area_struct
*vma
)
754 struct page
*src_page
;
760 pgtable
= pte_alloc_one(dst_mm
, addr
);
761 if (unlikely(!pgtable
))
764 spin_lock(&dst_mm
->page_table_lock
);
765 spin_lock_nested(&src_mm
->page_table_lock
, SINGLE_DEPTH_NESTING
);
769 if (unlikely(!pmd_trans_huge(pmd
))) {
770 pte_free(dst_mm
, pgtable
);
773 if (unlikely(pmd_trans_splitting(pmd
))) {
774 /* split huge page running from under us */
775 spin_unlock(&src_mm
->page_table_lock
);
776 spin_unlock(&dst_mm
->page_table_lock
);
777 pte_free(dst_mm
, pgtable
);
779 wait_split_huge_page(vma
->anon_vma
, src_pmd
); /* src_vma */
782 src_page
= pmd_page(pmd
);
783 VM_BUG_ON(!PageHead(src_page
));
785 page_dup_rmap(src_page
);
786 add_mm_counter(dst_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
788 pmdp_set_wrprotect(src_mm
, addr
, src_pmd
);
789 pmd
= pmd_mkold(pmd_wrprotect(pmd
));
790 set_pmd_at(dst_mm
, addr
, dst_pmd
, pmd
);
791 prepare_pmd_huge_pte(pgtable
, dst_mm
);
795 spin_unlock(&src_mm
->page_table_lock
);
796 spin_unlock(&dst_mm
->page_table_lock
);
801 /* no "address" argument so destroys page coloring of some arch */
802 pgtable_t
get_pmd_huge_pte(struct mm_struct
*mm
)
806 assert_spin_locked(&mm
->page_table_lock
);
809 pgtable
= mm
->pmd_huge_pte
;
810 if (list_empty(&pgtable
->lru
))
811 mm
->pmd_huge_pte
= NULL
;
813 mm
->pmd_huge_pte
= list_entry(pgtable
->lru
.next
,
815 list_del(&pgtable
->lru
);
820 static int do_huge_pmd_wp_page_fallback(struct mm_struct
*mm
,
821 struct vm_area_struct
*vma
,
822 unsigned long address
,
823 pmd_t
*pmd
, pmd_t orig_pmd
,
832 pages
= kmalloc(sizeof(struct page
*) * HPAGE_PMD_NR
,
834 if (unlikely(!pages
)) {
839 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
840 pages
[i
] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE
|
842 vma
, address
, page_to_nid(page
));
843 if (unlikely(!pages
[i
] ||
844 mem_cgroup_newpage_charge(pages
[i
], mm
,
848 mem_cgroup_uncharge_start();
850 mem_cgroup_uncharge_page(pages
[i
]);
853 mem_cgroup_uncharge_end();
860 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
861 copy_user_highpage(pages
[i
], page
+ i
,
862 haddr
+ PAGE_SIZE
* i
, vma
);
863 __SetPageUptodate(pages
[i
]);
867 spin_lock(&mm
->page_table_lock
);
868 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
870 VM_BUG_ON(!PageHead(page
));
872 pmdp_clear_flush_notify(vma
, haddr
, pmd
);
873 /* leave pmd empty until pte is filled */
875 pgtable
= get_pmd_huge_pte(mm
);
876 pmd_populate(mm
, &_pmd
, pgtable
);
878 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
880 entry
= mk_pte(pages
[i
], vma
->vm_page_prot
);
881 entry
= maybe_mkwrite(pte_mkdirty(entry
), vma
);
882 page_add_new_anon_rmap(pages
[i
], vma
, haddr
);
883 pte
= pte_offset_map(&_pmd
, haddr
);
884 VM_BUG_ON(!pte_none(*pte
));
885 set_pte_at(mm
, haddr
, pte
, entry
);
891 smp_wmb(); /* make pte visible before pmd */
892 pmd_populate(mm
, pmd
, pgtable
);
893 page_remove_rmap(page
);
894 spin_unlock(&mm
->page_table_lock
);
896 ret
|= VM_FAULT_WRITE
;
903 spin_unlock(&mm
->page_table_lock
);
904 mem_cgroup_uncharge_start();
905 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
906 mem_cgroup_uncharge_page(pages
[i
]);
909 mem_cgroup_uncharge_end();
914 int do_huge_pmd_wp_page(struct mm_struct
*mm
, struct vm_area_struct
*vma
,
915 unsigned long address
, pmd_t
*pmd
, pmd_t orig_pmd
)
918 struct page
*page
, *new_page
;
921 VM_BUG_ON(!vma
->anon_vma
);
922 spin_lock(&mm
->page_table_lock
);
923 if (unlikely(!pmd_same(*pmd
, orig_pmd
)))
926 page
= pmd_page(orig_pmd
);
927 VM_BUG_ON(!PageCompound(page
) || !PageHead(page
));
928 haddr
= address
& HPAGE_PMD_MASK
;
929 if (page_mapcount(page
) == 1) {
931 entry
= pmd_mkyoung(orig_pmd
);
932 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
933 if (pmdp_set_access_flags(vma
, haddr
, pmd
, entry
, 1))
934 update_mmu_cache(vma
, address
, entry
);
935 ret
|= VM_FAULT_WRITE
;
939 spin_unlock(&mm
->page_table_lock
);
941 if (transparent_hugepage_enabled(vma
) &&
942 !transparent_hugepage_debug_cow())
943 new_page
= alloc_hugepage_vma(transparent_hugepage_defrag(vma
),
944 vma
, haddr
, numa_node_id(), 0);
948 if (unlikely(!new_page
)) {
949 count_vm_event(THP_FAULT_FALLBACK
);
950 ret
= do_huge_pmd_wp_page_fallback(mm
, vma
, address
,
951 pmd
, orig_pmd
, page
, haddr
);
955 count_vm_event(THP_FAULT_ALLOC
);
957 if (unlikely(mem_cgroup_newpage_charge(new_page
, mm
, GFP_KERNEL
))) {
964 copy_user_huge_page(new_page
, page
, haddr
, vma
, HPAGE_PMD_NR
);
965 __SetPageUptodate(new_page
);
967 spin_lock(&mm
->page_table_lock
);
969 if (unlikely(!pmd_same(*pmd
, orig_pmd
))) {
970 mem_cgroup_uncharge_page(new_page
);
974 VM_BUG_ON(!PageHead(page
));
975 entry
= mk_pmd(new_page
, vma
->vm_page_prot
);
976 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
977 entry
= pmd_mkhuge(entry
);
978 pmdp_clear_flush_notify(vma
, haddr
, pmd
);
979 page_add_new_anon_rmap(new_page
, vma
, haddr
);
980 set_pmd_at(mm
, haddr
, pmd
, entry
);
981 update_mmu_cache(vma
, address
, entry
);
982 page_remove_rmap(page
);
984 ret
|= VM_FAULT_WRITE
;
987 spin_unlock(&mm
->page_table_lock
);
992 struct page
*follow_trans_huge_pmd(struct mm_struct
*mm
,
997 struct page
*page
= NULL
;
999 assert_spin_locked(&mm
->page_table_lock
);
1001 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
1004 page
= pmd_page(*pmd
);
1005 VM_BUG_ON(!PageHead(page
));
1006 if (flags
& FOLL_TOUCH
) {
1009 * We should set the dirty bit only for FOLL_WRITE but
1010 * for now the dirty bit in the pmd is meaningless.
1011 * And if the dirty bit will become meaningful and
1012 * we'll only set it with FOLL_WRITE, an atomic
1013 * set_bit will be required on the pmd to set the
1014 * young bit, instead of the current set_pmd_at.
1016 _pmd
= pmd_mkyoung(pmd_mkdirty(*pmd
));
1017 set_pmd_at(mm
, addr
& HPAGE_PMD_MASK
, pmd
, _pmd
);
1019 page
+= (addr
& ~HPAGE_PMD_MASK
) >> PAGE_SHIFT
;
1020 VM_BUG_ON(!PageCompound(page
));
1021 if (flags
& FOLL_GET
)
1022 get_page_foll(page
);
1028 int zap_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1033 spin_lock(&tlb
->mm
->page_table_lock
);
1034 if (likely(pmd_trans_huge(*pmd
))) {
1035 if (unlikely(pmd_trans_splitting(*pmd
))) {
1036 spin_unlock(&tlb
->mm
->page_table_lock
);
1037 wait_split_huge_page(vma
->anon_vma
,
1042 pgtable
= get_pmd_huge_pte(tlb
->mm
);
1043 page
= pmd_page(*pmd
);
1045 page_remove_rmap(page
);
1046 VM_BUG_ON(page_mapcount(page
) < 0);
1047 add_mm_counter(tlb
->mm
, MM_ANONPAGES
, -HPAGE_PMD_NR
);
1048 VM_BUG_ON(!PageHead(page
));
1049 spin_unlock(&tlb
->mm
->page_table_lock
);
1050 tlb_remove_page(tlb
, page
);
1051 pte_free(tlb
->mm
, pgtable
);
1055 spin_unlock(&tlb
->mm
->page_table_lock
);
1060 int mincore_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1061 unsigned long addr
, unsigned long end
,
1066 spin_lock(&vma
->vm_mm
->page_table_lock
);
1067 if (likely(pmd_trans_huge(*pmd
))) {
1068 ret
= !pmd_trans_splitting(*pmd
);
1069 spin_unlock(&vma
->vm_mm
->page_table_lock
);
1071 wait_split_huge_page(vma
->anon_vma
, pmd
);
1074 * All logical pages in the range are present
1075 * if backed by a huge page.
1077 memset(vec
, 1, (end
- addr
) >> PAGE_SHIFT
);
1080 spin_unlock(&vma
->vm_mm
->page_table_lock
);
1085 int move_huge_pmd(struct vm_area_struct
*vma
, struct vm_area_struct
*new_vma
,
1086 unsigned long old_addr
,
1087 unsigned long new_addr
, unsigned long old_end
,
1088 pmd_t
*old_pmd
, pmd_t
*new_pmd
)
1093 struct mm_struct
*mm
= vma
->vm_mm
;
1095 if ((old_addr
& ~HPAGE_PMD_MASK
) ||
1096 (new_addr
& ~HPAGE_PMD_MASK
) ||
1097 old_end
- old_addr
< HPAGE_PMD_SIZE
||
1098 (new_vma
->vm_flags
& VM_NOHUGEPAGE
))
1102 * The destination pmd shouldn't be established, free_pgtables()
1103 * should have release it.
1105 if (WARN_ON(!pmd_none(*new_pmd
))) {
1106 VM_BUG_ON(pmd_trans_huge(*new_pmd
));
1110 spin_lock(&mm
->page_table_lock
);
1111 if (likely(pmd_trans_huge(*old_pmd
))) {
1112 if (pmd_trans_splitting(*old_pmd
)) {
1113 spin_unlock(&mm
->page_table_lock
);
1114 wait_split_huge_page(vma
->anon_vma
, old_pmd
);
1117 pmd
= pmdp_get_and_clear(mm
, old_addr
, old_pmd
);
1118 VM_BUG_ON(!pmd_none(*new_pmd
));
1119 set_pmd_at(mm
, new_addr
, new_pmd
, pmd
);
1120 spin_unlock(&mm
->page_table_lock
);
1124 spin_unlock(&mm
->page_table_lock
);
1130 int change_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1131 unsigned long addr
, pgprot_t newprot
)
1133 struct mm_struct
*mm
= vma
->vm_mm
;
1136 spin_lock(&mm
->page_table_lock
);
1137 if (likely(pmd_trans_huge(*pmd
))) {
1138 if (unlikely(pmd_trans_splitting(*pmd
))) {
1139 spin_unlock(&mm
->page_table_lock
);
1140 wait_split_huge_page(vma
->anon_vma
, pmd
);
1144 entry
= pmdp_get_and_clear(mm
, addr
, pmd
);
1145 entry
= pmd_modify(entry
, newprot
);
1146 set_pmd_at(mm
, addr
, pmd
, entry
);
1147 spin_unlock(&vma
->vm_mm
->page_table_lock
);
1148 flush_tlb_range(vma
, addr
, addr
+ HPAGE_PMD_SIZE
);
1152 spin_unlock(&vma
->vm_mm
->page_table_lock
);
1157 pmd_t
*page_check_address_pmd(struct page
*page
,
1158 struct mm_struct
*mm
,
1159 unsigned long address
,
1160 enum page_check_address_pmd_flag flag
)
1164 pmd_t
*pmd
, *ret
= NULL
;
1166 if (address
& ~HPAGE_PMD_MASK
)
1169 pgd
= pgd_offset(mm
, address
);
1170 if (!pgd_present(*pgd
))
1173 pud
= pud_offset(pgd
, address
);
1174 if (!pud_present(*pud
))
1177 pmd
= pmd_offset(pud
, address
);
1180 if (pmd_page(*pmd
) != page
)
1183 * split_vma() may create temporary aliased mappings. There is
1184 * no risk as long as all huge pmd are found and have their
1185 * splitting bit set before __split_huge_page_refcount
1186 * runs. Finding the same huge pmd more than once during the
1187 * same rmap walk is not a problem.
1189 if (flag
== PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG
&&
1190 pmd_trans_splitting(*pmd
))
1192 if (pmd_trans_huge(*pmd
)) {
1193 VM_BUG_ON(flag
== PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG
&&
1194 !pmd_trans_splitting(*pmd
));
1201 static int __split_huge_page_splitting(struct page
*page
,
1202 struct vm_area_struct
*vma
,
1203 unsigned long address
)
1205 struct mm_struct
*mm
= vma
->vm_mm
;
1209 spin_lock(&mm
->page_table_lock
);
1210 pmd
= page_check_address_pmd(page
, mm
, address
,
1211 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG
);
1214 * We can't temporarily set the pmd to null in order
1215 * to split it, the pmd must remain marked huge at all
1216 * times or the VM won't take the pmd_trans_huge paths
1217 * and it won't wait on the anon_vma->root->mutex to
1218 * serialize against split_huge_page*.
1220 pmdp_splitting_flush_notify(vma
, address
, pmd
);
1223 spin_unlock(&mm
->page_table_lock
);
1228 static void __split_huge_page_refcount(struct page
*page
)
1231 unsigned long head_index
= page
->index
;
1232 struct zone
*zone
= page_zone(page
);
1236 /* prevent PageLRU to go away from under us, and freeze lru stats */
1237 spin_lock_irq(&zone
->lru_lock
);
1238 compound_lock(page
);
1239 /* complete memcg works before add pages to LRU */
1240 mem_cgroup_split_huge_fixup(page
);
1242 for (i
= 1; i
< HPAGE_PMD_NR
; i
++) {
1243 struct page
*page_tail
= page
+ i
;
1245 /* tail_page->_mapcount cannot change */
1246 BUG_ON(page_mapcount(page_tail
) < 0);
1247 tail_count
+= page_mapcount(page_tail
);
1248 /* check for overflow */
1249 BUG_ON(tail_count
< 0);
1250 BUG_ON(atomic_read(&page_tail
->_count
) != 0);
1252 * tail_page->_count is zero and not changing from
1253 * under us. But get_page_unless_zero() may be running
1254 * from under us on the tail_page. If we used
1255 * atomic_set() below instead of atomic_add(), we
1256 * would then run atomic_set() concurrently with
1257 * get_page_unless_zero(), and atomic_set() is
1258 * implemented in C not using locked ops. spin_unlock
1259 * on x86 sometime uses locked ops because of PPro
1260 * errata 66, 92, so unless somebody can guarantee
1261 * atomic_set() here would be safe on all archs (and
1262 * not only on x86), it's safer to use atomic_add().
1264 atomic_add(page_mapcount(page
) + page_mapcount(page_tail
) + 1,
1265 &page_tail
->_count
);
1267 /* after clearing PageTail the gup refcount can be released */
1271 * retain hwpoison flag of the poisoned tail page:
1272 * fix for the unsuitable process killed on Guest Machine(KVM)
1273 * by the memory-failure.
1275 page_tail
->flags
&= ~PAGE_FLAGS_CHECK_AT_PREP
| __PG_HWPOISON
;
1276 page_tail
->flags
|= (page
->flags
&
1277 ((1L << PG_referenced
) |
1278 (1L << PG_swapbacked
) |
1279 (1L << PG_mlocked
) |
1280 (1L << PG_uptodate
)));
1281 page_tail
->flags
|= (1L << PG_dirty
);
1283 /* clear PageTail before overwriting first_page */
1287 * __split_huge_page_splitting() already set the
1288 * splitting bit in all pmd that could map this
1289 * hugepage, that will ensure no CPU can alter the
1290 * mapcount on the head page. The mapcount is only
1291 * accounted in the head page and it has to be
1292 * transferred to all tail pages in the below code. So
1293 * for this code to be safe, the split the mapcount
1294 * can't change. But that doesn't mean userland can't
1295 * keep changing and reading the page contents while
1296 * we transfer the mapcount, so the pmd splitting
1297 * status is achieved setting a reserved bit in the
1298 * pmd, not by clearing the present bit.
1300 page_tail
->_mapcount
= page
->_mapcount
;
1302 BUG_ON(page_tail
->mapping
);
1303 page_tail
->mapping
= page
->mapping
;
1305 page_tail
->index
= ++head_index
;
1307 BUG_ON(!PageAnon(page_tail
));
1308 BUG_ON(!PageUptodate(page_tail
));
1309 BUG_ON(!PageDirty(page_tail
));
1310 BUG_ON(!PageSwapBacked(page_tail
));
1313 lru_add_page_tail(zone
, page
, page_tail
);
1315 atomic_sub(tail_count
, &page
->_count
);
1316 BUG_ON(atomic_read(&page
->_count
) <= 0);
1318 __dec_zone_page_state(page
, NR_ANON_TRANSPARENT_HUGEPAGES
);
1319 __mod_zone_page_state(zone
, NR_ANON_PAGES
, HPAGE_PMD_NR
);
1322 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1323 * so adjust those appropriately if this page is on the LRU.
1325 if (PageLRU(page
)) {
1326 zonestat
= NR_LRU_BASE
+ page_lru(page
);
1327 __mod_zone_page_state(zone
, zonestat
, -(HPAGE_PMD_NR
-1));
1330 ClearPageCompound(page
);
1331 compound_unlock(page
);
1332 spin_unlock_irq(&zone
->lru_lock
);
1334 for (i
= 1; i
< HPAGE_PMD_NR
; i
++) {
1335 struct page
*page_tail
= page
+ i
;
1336 BUG_ON(page_count(page_tail
) <= 0);
1338 * Tail pages may be freed if there wasn't any mapping
1339 * like if add_to_swap() is running on a lru page that
1340 * had its mapping zapped. And freeing these pages
1341 * requires taking the lru_lock so we do the put_page
1342 * of the tail pages after the split is complete.
1344 put_page(page_tail
);
1348 * Only the head page (now become a regular page) is required
1349 * to be pinned by the caller.
1351 BUG_ON(page_count(page
) <= 0);
1354 static int __split_huge_page_map(struct page
*page
,
1355 struct vm_area_struct
*vma
,
1356 unsigned long address
)
1358 struct mm_struct
*mm
= vma
->vm_mm
;
1362 unsigned long haddr
;
1364 spin_lock(&mm
->page_table_lock
);
1365 pmd
= page_check_address_pmd(page
, mm
, address
,
1366 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG
);
1368 pgtable
= get_pmd_huge_pte(mm
);
1369 pmd_populate(mm
, &_pmd
, pgtable
);
1371 for (i
= 0, haddr
= address
; i
< HPAGE_PMD_NR
;
1372 i
++, haddr
+= PAGE_SIZE
) {
1374 BUG_ON(PageCompound(page
+i
));
1375 entry
= mk_pte(page
+ i
, vma
->vm_page_prot
);
1376 entry
= maybe_mkwrite(pte_mkdirty(entry
), vma
);
1377 if (!pmd_write(*pmd
))
1378 entry
= pte_wrprotect(entry
);
1380 BUG_ON(page_mapcount(page
) != 1);
1381 if (!pmd_young(*pmd
))
1382 entry
= pte_mkold(entry
);
1383 pte
= pte_offset_map(&_pmd
, haddr
);
1384 BUG_ON(!pte_none(*pte
));
1385 set_pte_at(mm
, haddr
, pte
, entry
);
1390 smp_wmb(); /* make pte visible before pmd */
1392 * Up to this point the pmd is present and huge and
1393 * userland has the whole access to the hugepage
1394 * during the split (which happens in place). If we
1395 * overwrite the pmd with the not-huge version
1396 * pointing to the pte here (which of course we could
1397 * if all CPUs were bug free), userland could trigger
1398 * a small page size TLB miss on the small sized TLB
1399 * while the hugepage TLB entry is still established
1400 * in the huge TLB. Some CPU doesn't like that. See
1401 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1402 * Erratum 383 on page 93. Intel should be safe but is
1403 * also warns that it's only safe if the permission
1404 * and cache attributes of the two entries loaded in
1405 * the two TLB is identical (which should be the case
1406 * here). But it is generally safer to never allow
1407 * small and huge TLB entries for the same virtual
1408 * address to be loaded simultaneously. So instead of
1409 * doing "pmd_populate(); flush_tlb_range();" we first
1410 * mark the current pmd notpresent (atomically because
1411 * here the pmd_trans_huge and pmd_trans_splitting
1412 * must remain set at all times on the pmd until the
1413 * split is complete for this pmd), then we flush the
1414 * SMP TLB and finally we write the non-huge version
1415 * of the pmd entry with pmd_populate.
1417 set_pmd_at(mm
, address
, pmd
, pmd_mknotpresent(*pmd
));
1418 flush_tlb_range(vma
, address
, address
+ HPAGE_PMD_SIZE
);
1419 pmd_populate(mm
, pmd
, pgtable
);
1422 spin_unlock(&mm
->page_table_lock
);
1427 /* must be called with anon_vma->root->mutex hold */
1428 static void __split_huge_page(struct page
*page
,
1429 struct anon_vma
*anon_vma
)
1431 int mapcount
, mapcount2
;
1432 struct anon_vma_chain
*avc
;
1434 BUG_ON(!PageHead(page
));
1435 BUG_ON(PageTail(page
));
1438 list_for_each_entry(avc
, &anon_vma
->head
, same_anon_vma
) {
1439 struct vm_area_struct
*vma
= avc
->vma
;
1440 unsigned long addr
= vma_address(page
, vma
);
1441 BUG_ON(is_vma_temporary_stack(vma
));
1442 if (addr
== -EFAULT
)
1444 mapcount
+= __split_huge_page_splitting(page
, vma
, addr
);
1447 * It is critical that new vmas are added to the tail of the
1448 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1449 * and establishes a child pmd before
1450 * __split_huge_page_splitting() freezes the parent pmd (so if
1451 * we fail to prevent copy_huge_pmd() from running until the
1452 * whole __split_huge_page() is complete), we will still see
1453 * the newly established pmd of the child later during the
1454 * walk, to be able to set it as pmd_trans_splitting too.
1456 if (mapcount
!= page_mapcount(page
))
1457 printk(KERN_ERR
"mapcount %d page_mapcount %d\n",
1458 mapcount
, page_mapcount(page
));
1459 BUG_ON(mapcount
!= page_mapcount(page
));
1461 __split_huge_page_refcount(page
);
1464 list_for_each_entry(avc
, &anon_vma
->head
, same_anon_vma
) {
1465 struct vm_area_struct
*vma
= avc
->vma
;
1466 unsigned long addr
= vma_address(page
, vma
);
1467 BUG_ON(is_vma_temporary_stack(vma
));
1468 if (addr
== -EFAULT
)
1470 mapcount2
+= __split_huge_page_map(page
, vma
, addr
);
1472 if (mapcount
!= mapcount2
)
1473 printk(KERN_ERR
"mapcount %d mapcount2 %d page_mapcount %d\n",
1474 mapcount
, mapcount2
, page_mapcount(page
));
1475 BUG_ON(mapcount
!= mapcount2
);
1478 int split_huge_page(struct page
*page
)
1480 struct anon_vma
*anon_vma
;
1483 BUG_ON(!PageAnon(page
));
1484 anon_vma
= page_lock_anon_vma(page
);
1488 if (!PageCompound(page
))
1491 BUG_ON(!PageSwapBacked(page
));
1492 __split_huge_page(page
, anon_vma
);
1493 count_vm_event(THP_SPLIT
);
1495 BUG_ON(PageCompound(page
));
1497 page_unlock_anon_vma(anon_vma
);
1502 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1503 VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1505 int hugepage_madvise(struct vm_area_struct
*vma
,
1506 unsigned long *vm_flags
, int advice
)
1511 * Be somewhat over-protective like KSM for now!
1513 if (*vm_flags
& (VM_HUGEPAGE
| VM_NO_THP
))
1515 *vm_flags
&= ~VM_NOHUGEPAGE
;
1516 *vm_flags
|= VM_HUGEPAGE
;
1518 * If the vma become good for khugepaged to scan,
1519 * register it here without waiting a page fault that
1520 * may not happen any time soon.
1522 if (unlikely(khugepaged_enter_vma_merge(vma
)))
1525 case MADV_NOHUGEPAGE
:
1527 * Be somewhat over-protective like KSM for now!
1529 if (*vm_flags
& (VM_NOHUGEPAGE
| VM_NO_THP
))
1531 *vm_flags
&= ~VM_HUGEPAGE
;
1532 *vm_flags
|= VM_NOHUGEPAGE
;
1534 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1535 * this vma even if we leave the mm registered in khugepaged if
1536 * it got registered before VM_NOHUGEPAGE was set.
1544 static int __init
khugepaged_slab_init(void)
1546 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
1547 sizeof(struct mm_slot
),
1548 __alignof__(struct mm_slot
), 0, NULL
);
1555 static void __init
khugepaged_slab_free(void)
1557 kmem_cache_destroy(mm_slot_cache
);
1558 mm_slot_cache
= NULL
;
1561 static inline struct mm_slot
*alloc_mm_slot(void)
1563 if (!mm_slot_cache
) /* initialization failed */
1565 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
1568 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
1570 kmem_cache_free(mm_slot_cache
, mm_slot
);
1573 static int __init
mm_slots_hash_init(void)
1575 mm_slots_hash
= kzalloc(MM_SLOTS_HASH_HEADS
* sizeof(struct hlist_head
),
1583 static void __init
mm_slots_hash_free(void)
1585 kfree(mm_slots_hash
);
1586 mm_slots_hash
= NULL
;
1590 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
1592 struct mm_slot
*mm_slot
;
1593 struct hlist_head
*bucket
;
1594 struct hlist_node
*node
;
1596 bucket
= &mm_slots_hash
[((unsigned long)mm
/ sizeof(struct mm_struct
))
1597 % MM_SLOTS_HASH_HEADS
];
1598 hlist_for_each_entry(mm_slot
, node
, bucket
, hash
) {
1599 if (mm
== mm_slot
->mm
)
1605 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
1606 struct mm_slot
*mm_slot
)
1608 struct hlist_head
*bucket
;
1610 bucket
= &mm_slots_hash
[((unsigned long)mm
/ sizeof(struct mm_struct
))
1611 % MM_SLOTS_HASH_HEADS
];
1613 hlist_add_head(&mm_slot
->hash
, bucket
);
1616 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
1618 return atomic_read(&mm
->mm_users
) == 0;
1621 int __khugepaged_enter(struct mm_struct
*mm
)
1623 struct mm_slot
*mm_slot
;
1626 mm_slot
= alloc_mm_slot();
1630 /* __khugepaged_exit() must not run from under us */
1631 VM_BUG_ON(khugepaged_test_exit(mm
));
1632 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
1633 free_mm_slot(mm_slot
);
1637 spin_lock(&khugepaged_mm_lock
);
1638 insert_to_mm_slots_hash(mm
, mm_slot
);
1640 * Insert just behind the scanning cursor, to let the area settle
1643 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
1644 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
1645 spin_unlock(&khugepaged_mm_lock
);
1647 atomic_inc(&mm
->mm_count
);
1649 wake_up_interruptible(&khugepaged_wait
);
1654 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
)
1656 unsigned long hstart
, hend
;
1659 * Not yet faulted in so we will register later in the
1660 * page fault if needed.
1664 /* khugepaged not yet working on file or special mappings */
1667 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1668 * true too, verify it here.
1670 VM_BUG_ON(is_linear_pfn_mapping(vma
) || vma
->vm_flags
& VM_NO_THP
);
1671 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1672 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1674 return khugepaged_enter(vma
);
1678 void __khugepaged_exit(struct mm_struct
*mm
)
1680 struct mm_slot
*mm_slot
;
1683 spin_lock(&khugepaged_mm_lock
);
1684 mm_slot
= get_mm_slot(mm
);
1685 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
1686 hlist_del(&mm_slot
->hash
);
1687 list_del(&mm_slot
->mm_node
);
1690 spin_unlock(&khugepaged_mm_lock
);
1693 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
1694 free_mm_slot(mm_slot
);
1696 } else if (mm_slot
) {
1698 * This is required to serialize against
1699 * khugepaged_test_exit() (which is guaranteed to run
1700 * under mmap sem read mode). Stop here (after we
1701 * return all pagetables will be destroyed) until
1702 * khugepaged has finished working on the pagetables
1703 * under the mmap_sem.
1705 down_write(&mm
->mmap_sem
);
1706 up_write(&mm
->mmap_sem
);
1710 static void release_pte_page(struct page
*page
)
1712 /* 0 stands for page_is_file_cache(page) == false */
1713 dec_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
1715 putback_lru_page(page
);
1718 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
)
1720 while (--_pte
>= pte
) {
1721 pte_t pteval
= *_pte
;
1722 if (!pte_none(pteval
))
1723 release_pte_page(pte_page(pteval
));
1727 static void release_all_pte_pages(pte_t
*pte
)
1729 release_pte_pages(pte
, pte
+ HPAGE_PMD_NR
);
1732 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
1733 unsigned long address
,
1738 int referenced
= 0, isolated
= 0, none
= 0;
1739 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
1740 _pte
++, address
+= PAGE_SIZE
) {
1741 pte_t pteval
= *_pte
;
1742 if (pte_none(pteval
)) {
1743 if (++none
<= khugepaged_max_ptes_none
)
1746 release_pte_pages(pte
, _pte
);
1750 if (!pte_present(pteval
) || !pte_write(pteval
)) {
1751 release_pte_pages(pte
, _pte
);
1754 page
= vm_normal_page(vma
, address
, pteval
);
1755 if (unlikely(!page
)) {
1756 release_pte_pages(pte
, _pte
);
1759 VM_BUG_ON(PageCompound(page
));
1760 BUG_ON(!PageAnon(page
));
1761 VM_BUG_ON(!PageSwapBacked(page
));
1763 /* cannot use mapcount: can't collapse if there's a gup pin */
1764 if (page_count(page
) != 1) {
1765 release_pte_pages(pte
, _pte
);
1769 * We can do it before isolate_lru_page because the
1770 * page can't be freed from under us. NOTE: PG_lock
1771 * is needed to serialize against split_huge_page
1772 * when invoked from the VM.
1774 if (!trylock_page(page
)) {
1775 release_pte_pages(pte
, _pte
);
1779 * Isolate the page to avoid collapsing an hugepage
1780 * currently in use by the VM.
1782 if (isolate_lru_page(page
)) {
1784 release_pte_pages(pte
, _pte
);
1787 /* 0 stands for page_is_file_cache(page) == false */
1788 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
1789 VM_BUG_ON(!PageLocked(page
));
1790 VM_BUG_ON(PageLRU(page
));
1792 /* If there is no mapped pte young don't collapse the page */
1793 if (pte_young(pteval
) || PageReferenced(page
) ||
1794 mmu_notifier_test_young(vma
->vm_mm
, address
))
1797 if (unlikely(!referenced
))
1798 release_all_pte_pages(pte
);
1805 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
1806 struct vm_area_struct
*vma
,
1807 unsigned long address
,
1811 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
; _pte
++) {
1812 pte_t pteval
= *_pte
;
1813 struct page
*src_page
;
1815 if (pte_none(pteval
)) {
1816 clear_user_highpage(page
, address
);
1817 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
1819 src_page
= pte_page(pteval
);
1820 copy_user_highpage(page
, src_page
, address
, vma
);
1821 VM_BUG_ON(page_mapcount(src_page
) != 1);
1822 VM_BUG_ON(page_count(src_page
) != 2);
1823 release_pte_page(src_page
);
1825 * ptl mostly unnecessary, but preempt has to
1826 * be disabled to update the per-cpu stats
1827 * inside page_remove_rmap().
1831 * paravirt calls inside pte_clear here are
1834 pte_clear(vma
->vm_mm
, address
, _pte
);
1835 page_remove_rmap(src_page
);
1837 free_page_and_swap_cache(src_page
);
1840 address
+= PAGE_SIZE
;
1845 static void collapse_huge_page(struct mm_struct
*mm
,
1846 unsigned long address
,
1847 struct page
**hpage
,
1848 struct vm_area_struct
*vma
,
1856 struct page
*new_page
;
1859 unsigned long hstart
, hend
;
1861 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1863 up_read(&mm
->mmap_sem
);
1869 * Allocate the page while the vma is still valid and under
1870 * the mmap_sem read mode so there is no memory allocation
1871 * later when we take the mmap_sem in write mode. This is more
1872 * friendly behavior (OTOH it may actually hide bugs) to
1873 * filesystems in userland with daemons allocating memory in
1874 * the userland I/O paths. Allocating memory with the
1875 * mmap_sem in read mode is good idea also to allow greater
1878 new_page
= alloc_hugepage_vma(khugepaged_defrag(), vma
, address
,
1879 node
, __GFP_OTHER_NODE
);
1882 * After allocating the hugepage, release the mmap_sem read lock in
1883 * preparation for taking it in write mode.
1885 up_read(&mm
->mmap_sem
);
1886 if (unlikely(!new_page
)) {
1887 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
1888 *hpage
= ERR_PTR(-ENOMEM
);
1893 count_vm_event(THP_COLLAPSE_ALLOC
);
1894 if (unlikely(mem_cgroup_newpage_charge(new_page
, mm
, GFP_KERNEL
))) {
1902 * Prevent all access to pagetables with the exception of
1903 * gup_fast later hanlded by the ptep_clear_flush and the VM
1904 * handled by the anon_vma lock + PG_lock.
1906 down_write(&mm
->mmap_sem
);
1907 if (unlikely(khugepaged_test_exit(mm
)))
1910 vma
= find_vma(mm
, address
);
1911 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1912 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1913 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
)
1916 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
1917 (vma
->vm_flags
& VM_NOHUGEPAGE
))
1920 if (!vma
->anon_vma
|| vma
->vm_ops
)
1922 if (is_vma_temporary_stack(vma
))
1925 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1926 * true too, verify it here.
1928 VM_BUG_ON(is_linear_pfn_mapping(vma
) || vma
->vm_flags
& VM_NO_THP
);
1930 pgd
= pgd_offset(mm
, address
);
1931 if (!pgd_present(*pgd
))
1934 pud
= pud_offset(pgd
, address
);
1935 if (!pud_present(*pud
))
1938 pmd
= pmd_offset(pud
, address
);
1939 /* pmd can't go away or become huge under us */
1940 if (!pmd_present(*pmd
) || pmd_trans_huge(*pmd
))
1943 anon_vma_lock(vma
->anon_vma
);
1945 pte
= pte_offset_map(pmd
, address
);
1946 ptl
= pte_lockptr(mm
, pmd
);
1948 spin_lock(&mm
->page_table_lock
); /* probably unnecessary */
1950 * After this gup_fast can't run anymore. This also removes
1951 * any huge TLB entry from the CPU so we won't allow
1952 * huge and small TLB entries for the same virtual address
1953 * to avoid the risk of CPU bugs in that area.
1955 _pmd
= pmdp_clear_flush_notify(vma
, address
, pmd
);
1956 spin_unlock(&mm
->page_table_lock
);
1959 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
);
1962 if (unlikely(!isolated
)) {
1964 spin_lock(&mm
->page_table_lock
);
1965 BUG_ON(!pmd_none(*pmd
));
1966 set_pmd_at(mm
, address
, pmd
, _pmd
);
1967 spin_unlock(&mm
->page_table_lock
);
1968 anon_vma_unlock(vma
->anon_vma
);
1973 * All pages are isolated and locked so anon_vma rmap
1974 * can't run anymore.
1976 anon_vma_unlock(vma
->anon_vma
);
1978 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, ptl
);
1980 __SetPageUptodate(new_page
);
1981 pgtable
= pmd_pgtable(_pmd
);
1982 VM_BUG_ON(page_count(pgtable
) != 1);
1983 VM_BUG_ON(page_mapcount(pgtable
) != 0);
1985 _pmd
= mk_pmd(new_page
, vma
->vm_page_prot
);
1986 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
1987 _pmd
= pmd_mkhuge(_pmd
);
1990 * spin_lock() below is not the equivalent of smp_wmb(), so
1991 * this is needed to avoid the copy_huge_page writes to become
1992 * visible after the set_pmd_at() write.
1996 spin_lock(&mm
->page_table_lock
);
1997 BUG_ON(!pmd_none(*pmd
));
1998 page_add_new_anon_rmap(new_page
, vma
, address
);
1999 set_pmd_at(mm
, address
, pmd
, _pmd
);
2000 update_mmu_cache(vma
, address
, _pmd
);
2001 prepare_pmd_huge_pte(pgtable
, mm
);
2003 spin_unlock(&mm
->page_table_lock
);
2008 khugepaged_pages_collapsed
++;
2010 up_write(&mm
->mmap_sem
);
2014 mem_cgroup_uncharge_page(new_page
);
2021 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
2022 struct vm_area_struct
*vma
,
2023 unsigned long address
,
2024 struct page
**hpage
)
2030 int ret
= 0, referenced
= 0, none
= 0;
2032 unsigned long _address
;
2036 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
2038 pgd
= pgd_offset(mm
, address
);
2039 if (!pgd_present(*pgd
))
2042 pud
= pud_offset(pgd
, address
);
2043 if (!pud_present(*pud
))
2046 pmd
= pmd_offset(pud
, address
);
2047 if (!pmd_present(*pmd
) || pmd_trans_huge(*pmd
))
2050 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
2051 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
2052 _pte
++, _address
+= PAGE_SIZE
) {
2053 pte_t pteval
= *_pte
;
2054 if (pte_none(pteval
)) {
2055 if (++none
<= khugepaged_max_ptes_none
)
2060 if (!pte_present(pteval
) || !pte_write(pteval
))
2062 page
= vm_normal_page(vma
, _address
, pteval
);
2063 if (unlikely(!page
))
2066 * Chose the node of the first page. This could
2067 * be more sophisticated and look at more pages,
2068 * but isn't for now.
2071 node
= page_to_nid(page
);
2072 VM_BUG_ON(PageCompound(page
));
2073 if (!PageLRU(page
) || PageLocked(page
) || !PageAnon(page
))
2075 /* cannot use mapcount: can't collapse if there's a gup pin */
2076 if (page_count(page
) != 1)
2078 if (pte_young(pteval
) || PageReferenced(page
) ||
2079 mmu_notifier_test_young(vma
->vm_mm
, address
))
2085 pte_unmap_unlock(pte
, ptl
);
2087 /* collapse_huge_page will return with the mmap_sem released */
2088 collapse_huge_page(mm
, address
, hpage
, vma
, node
);
2093 static void collect_mm_slot(struct mm_slot
*mm_slot
)
2095 struct mm_struct
*mm
= mm_slot
->mm
;
2097 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock
));
2099 if (khugepaged_test_exit(mm
)) {
2101 hlist_del(&mm_slot
->hash
);
2102 list_del(&mm_slot
->mm_node
);
2105 * Not strictly needed because the mm exited already.
2107 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2110 /* khugepaged_mm_lock actually not necessary for the below */
2111 free_mm_slot(mm_slot
);
2116 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2117 struct page
**hpage
)
2118 __releases(&khugepaged_mm_lock
)
2119 __acquires(&khugepaged_mm_lock
)
2121 struct mm_slot
*mm_slot
;
2122 struct mm_struct
*mm
;
2123 struct vm_area_struct
*vma
;
2127 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock
));
2129 if (khugepaged_scan
.mm_slot
)
2130 mm_slot
= khugepaged_scan
.mm_slot
;
2132 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2133 struct mm_slot
, mm_node
);
2134 khugepaged_scan
.address
= 0;
2135 khugepaged_scan
.mm_slot
= mm_slot
;
2137 spin_unlock(&khugepaged_mm_lock
);
2140 down_read(&mm
->mmap_sem
);
2141 if (unlikely(khugepaged_test_exit(mm
)))
2144 vma
= find_vma(mm
, khugepaged_scan
.address
);
2147 for (; vma
; vma
= vma
->vm_next
) {
2148 unsigned long hstart
, hend
;
2151 if (unlikely(khugepaged_test_exit(mm
))) {
2156 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) &&
2157 !khugepaged_always()) ||
2158 (vma
->vm_flags
& VM_NOHUGEPAGE
)) {
2163 if (!vma
->anon_vma
|| vma
->vm_ops
)
2165 if (is_vma_temporary_stack(vma
))
2168 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2169 * must be true too, verify it here.
2171 VM_BUG_ON(is_linear_pfn_mapping(vma
) ||
2172 vma
->vm_flags
& VM_NO_THP
);
2174 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2175 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2178 if (khugepaged_scan
.address
> hend
)
2180 if (khugepaged_scan
.address
< hstart
)
2181 khugepaged_scan
.address
= hstart
;
2182 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2184 while (khugepaged_scan
.address
< hend
) {
2187 if (unlikely(khugepaged_test_exit(mm
)))
2188 goto breakouterloop
;
2190 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2191 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2193 ret
= khugepaged_scan_pmd(mm
, vma
,
2194 khugepaged_scan
.address
,
2196 /* move to next address */
2197 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2198 progress
+= HPAGE_PMD_NR
;
2200 /* we released mmap_sem so break loop */
2201 goto breakouterloop_mmap_sem
;
2202 if (progress
>= pages
)
2203 goto breakouterloop
;
2207 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
2208 breakouterloop_mmap_sem
:
2210 spin_lock(&khugepaged_mm_lock
);
2211 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2213 * Release the current mm_slot if this mm is about to die, or
2214 * if we scanned all vmas of this mm.
2216 if (khugepaged_test_exit(mm
) || !vma
) {
2218 * Make sure that if mm_users is reaching zero while
2219 * khugepaged runs here, khugepaged_exit will find
2220 * mm_slot not pointing to the exiting mm.
2222 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2223 khugepaged_scan
.mm_slot
= list_entry(
2224 mm_slot
->mm_node
.next
,
2225 struct mm_slot
, mm_node
);
2226 khugepaged_scan
.address
= 0;
2228 khugepaged_scan
.mm_slot
= NULL
;
2229 khugepaged_full_scans
++;
2232 collect_mm_slot(mm_slot
);
2238 static int khugepaged_has_work(void)
2240 return !list_empty(&khugepaged_scan
.mm_head
) &&
2241 khugepaged_enabled();
2244 static int khugepaged_wait_event(void)
2246 return !list_empty(&khugepaged_scan
.mm_head
) ||
2247 !khugepaged_enabled();
2250 static void khugepaged_do_scan(struct page
**hpage
)
2252 unsigned int progress
= 0, pass_through_head
= 0;
2253 unsigned int pages
= khugepaged_pages_to_scan
;
2255 barrier(); /* write khugepaged_pages_to_scan to local stack */
2257 while (progress
< pages
) {
2262 *hpage
= alloc_hugepage(khugepaged_defrag());
2263 if (unlikely(!*hpage
)) {
2264 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2267 count_vm_event(THP_COLLAPSE_ALLOC
);
2274 if (unlikely(kthread_should_stop() || freezing(current
)))
2277 spin_lock(&khugepaged_mm_lock
);
2278 if (!khugepaged_scan
.mm_slot
)
2279 pass_through_head
++;
2280 if (khugepaged_has_work() &&
2281 pass_through_head
< 2)
2282 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2286 spin_unlock(&khugepaged_mm_lock
);
2290 static void khugepaged_alloc_sleep(void)
2292 wait_event_freezable_timeout(khugepaged_wait
, false,
2293 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
2297 static struct page
*khugepaged_alloc_hugepage(void)
2302 hpage
= alloc_hugepage(khugepaged_defrag());
2304 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
2305 khugepaged_alloc_sleep();
2307 count_vm_event(THP_COLLAPSE_ALLOC
);
2308 } while (unlikely(!hpage
) &&
2309 likely(khugepaged_enabled()));
2314 static void khugepaged_loop(void)
2321 while (likely(khugepaged_enabled())) {
2323 hpage
= khugepaged_alloc_hugepage();
2324 if (unlikely(!hpage
))
2327 if (IS_ERR(hpage
)) {
2328 khugepaged_alloc_sleep();
2333 khugepaged_do_scan(&hpage
);
2339 if (unlikely(kthread_should_stop()))
2341 if (khugepaged_has_work()) {
2342 if (!khugepaged_scan_sleep_millisecs
)
2344 wait_event_freezable_timeout(khugepaged_wait
, false,
2345 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
));
2346 } else if (khugepaged_enabled())
2347 wait_event_freezable(khugepaged_wait
,
2348 khugepaged_wait_event());
2352 static int khugepaged(void *none
)
2354 struct mm_slot
*mm_slot
;
2357 set_user_nice(current
, 19);
2359 /* serialize with start_khugepaged() */
2360 mutex_lock(&khugepaged_mutex
);
2363 mutex_unlock(&khugepaged_mutex
);
2364 VM_BUG_ON(khugepaged_thread
!= current
);
2366 VM_BUG_ON(khugepaged_thread
!= current
);
2368 mutex_lock(&khugepaged_mutex
);
2369 if (!khugepaged_enabled())
2371 if (unlikely(kthread_should_stop()))
2375 spin_lock(&khugepaged_mm_lock
);
2376 mm_slot
= khugepaged_scan
.mm_slot
;
2377 khugepaged_scan
.mm_slot
= NULL
;
2379 collect_mm_slot(mm_slot
);
2380 spin_unlock(&khugepaged_mm_lock
);
2382 khugepaged_thread
= NULL
;
2383 mutex_unlock(&khugepaged_mutex
);
2388 void __split_huge_page_pmd(struct mm_struct
*mm
, pmd_t
*pmd
)
2392 spin_lock(&mm
->page_table_lock
);
2393 if (unlikely(!pmd_trans_huge(*pmd
))) {
2394 spin_unlock(&mm
->page_table_lock
);
2397 page
= pmd_page(*pmd
);
2398 VM_BUG_ON(!page_count(page
));
2400 spin_unlock(&mm
->page_table_lock
);
2402 split_huge_page(page
);
2405 BUG_ON(pmd_trans_huge(*pmd
));
2408 static void split_huge_page_address(struct mm_struct
*mm
,
2409 unsigned long address
)
2415 VM_BUG_ON(!(address
& ~HPAGE_PMD_MASK
));
2417 pgd
= pgd_offset(mm
, address
);
2418 if (!pgd_present(*pgd
))
2421 pud
= pud_offset(pgd
, address
);
2422 if (!pud_present(*pud
))
2425 pmd
= pmd_offset(pud
, address
);
2426 if (!pmd_present(*pmd
))
2429 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2430 * materialize from under us.
2432 split_huge_page_pmd(mm
, pmd
);
2435 void __vma_adjust_trans_huge(struct vm_area_struct
*vma
,
2436 unsigned long start
,
2441 * If the new start address isn't hpage aligned and it could
2442 * previously contain an hugepage: check if we need to split
2445 if (start
& ~HPAGE_PMD_MASK
&&
2446 (start
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
2447 (start
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
2448 split_huge_page_address(vma
->vm_mm
, start
);
2451 * If the new end address isn't hpage aligned and it could
2452 * previously contain an hugepage: check if we need to split
2455 if (end
& ~HPAGE_PMD_MASK
&&
2456 (end
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
2457 (end
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
2458 split_huge_page_address(vma
->vm_mm
, end
);
2461 * If we're also updating the vma->vm_next->vm_start, if the new
2462 * vm_next->vm_start isn't page aligned and it could previously
2463 * contain an hugepage: check if we need to split an huge pmd.
2465 if (adjust_next
> 0) {
2466 struct vm_area_struct
*next
= vma
->vm_next
;
2467 unsigned long nstart
= next
->vm_start
;
2468 nstart
+= adjust_next
<< PAGE_SHIFT
;
2469 if (nstart
& ~HPAGE_PMD_MASK
&&
2470 (nstart
& HPAGE_PMD_MASK
) >= next
->vm_start
&&
2471 (nstart
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= next
->vm_end
)
2472 split_huge_page_address(next
->vm_mm
, nstart
);