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/khugepaged.h>
22 #include <linux/freezer.h>
23 #include <linux/pfn_t.h>
24 #include <linux/mman.h>
25 #include <linux/memremap.h>
26 #include <linux/pagemap.h>
27 #include <linux/debugfs.h>
28 #include <linux/migrate.h>
29 #include <linux/hashtable.h>
30 #include <linux/userfaultfd_k.h>
31 #include <linux/page_idle.h>
32 #include <linux/shmem_fs.h>
35 #include <asm/pgalloc.h>
39 * By default transparent hugepage support is disabled in order that avoid
40 * to risk increase the memory footprint of applications without a guaranteed
41 * benefit. When transparent hugepage support is enabled, is for all mappings,
42 * and khugepaged scans all mappings.
43 * Defrag is invoked by khugepaged hugepage allocations and by page faults
44 * for all hugepage allocations.
46 unsigned long transparent_hugepage_flags __read_mostly
=
47 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
48 (1<<TRANSPARENT_HUGEPAGE_FLAG
)|
50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
51 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
)|
53 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
)|
54 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
)|
55 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
57 static struct shrinker deferred_split_shrinker
;
59 static atomic_t huge_zero_refcount
;
60 struct page
*huge_zero_page __read_mostly
;
62 static struct page
*get_huge_zero_page(void)
64 struct page
*zero_page
;
66 if (likely(atomic_inc_not_zero(&huge_zero_refcount
)))
67 return READ_ONCE(huge_zero_page
);
69 zero_page
= alloc_pages((GFP_TRANSHUGE
| __GFP_ZERO
) & ~__GFP_MOVABLE
,
72 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED
);
75 count_vm_event(THP_ZERO_PAGE_ALLOC
);
77 if (cmpxchg(&huge_zero_page
, NULL
, zero_page
)) {
79 __free_pages(zero_page
, compound_order(zero_page
));
83 /* We take additional reference here. It will be put back by shrinker */
84 atomic_set(&huge_zero_refcount
, 2);
86 return READ_ONCE(huge_zero_page
);
89 static void put_huge_zero_page(void)
92 * Counter should never go to zero here. Only shrinker can put
95 BUG_ON(atomic_dec_and_test(&huge_zero_refcount
));
98 struct page
*mm_get_huge_zero_page(struct mm_struct
*mm
)
100 if (test_bit(MMF_HUGE_ZERO_PAGE
, &mm
->flags
))
101 return READ_ONCE(huge_zero_page
);
103 if (!get_huge_zero_page())
106 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE
, &mm
->flags
))
107 put_huge_zero_page();
109 return READ_ONCE(huge_zero_page
);
112 void mm_put_huge_zero_page(struct mm_struct
*mm
)
114 if (test_bit(MMF_HUGE_ZERO_PAGE
, &mm
->flags
))
115 put_huge_zero_page();
118 static unsigned long shrink_huge_zero_page_count(struct shrinker
*shrink
,
119 struct shrink_control
*sc
)
121 /* we can free zero page only if last reference remains */
122 return atomic_read(&huge_zero_refcount
) == 1 ? HPAGE_PMD_NR
: 0;
125 static unsigned long shrink_huge_zero_page_scan(struct shrinker
*shrink
,
126 struct shrink_control
*sc
)
128 if (atomic_cmpxchg(&huge_zero_refcount
, 1, 0) == 1) {
129 struct page
*zero_page
= xchg(&huge_zero_page
, NULL
);
130 BUG_ON(zero_page
== NULL
);
131 __free_pages(zero_page
, compound_order(zero_page
));
138 static struct shrinker huge_zero_page_shrinker
= {
139 .count_objects
= shrink_huge_zero_page_count
,
140 .scan_objects
= shrink_huge_zero_page_scan
,
141 .seeks
= DEFAULT_SEEKS
,
146 static ssize_t
triple_flag_store(struct kobject
*kobj
,
147 struct kobj_attribute
*attr
,
148 const char *buf
, size_t count
,
149 enum transparent_hugepage_flag enabled
,
150 enum transparent_hugepage_flag deferred
,
151 enum transparent_hugepage_flag req_madv
)
153 if (!memcmp("defer", buf
,
154 min(sizeof("defer")-1, count
))) {
155 if (enabled
== deferred
)
157 clear_bit(enabled
, &transparent_hugepage_flags
);
158 clear_bit(req_madv
, &transparent_hugepage_flags
);
159 set_bit(deferred
, &transparent_hugepage_flags
);
160 } else if (!memcmp("always", buf
,
161 min(sizeof("always")-1, count
))) {
162 clear_bit(deferred
, &transparent_hugepage_flags
);
163 clear_bit(req_madv
, &transparent_hugepage_flags
);
164 set_bit(enabled
, &transparent_hugepage_flags
);
165 } else if (!memcmp("madvise", buf
,
166 min(sizeof("madvise")-1, count
))) {
167 clear_bit(enabled
, &transparent_hugepage_flags
);
168 clear_bit(deferred
, &transparent_hugepage_flags
);
169 set_bit(req_madv
, &transparent_hugepage_flags
);
170 } else if (!memcmp("never", buf
,
171 min(sizeof("never")-1, count
))) {
172 clear_bit(enabled
, &transparent_hugepage_flags
);
173 clear_bit(req_madv
, &transparent_hugepage_flags
);
174 clear_bit(deferred
, &transparent_hugepage_flags
);
181 static ssize_t
enabled_show(struct kobject
*kobj
,
182 struct kobj_attribute
*attr
, char *buf
)
184 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG
, &transparent_hugepage_flags
))
185 return sprintf(buf
, "[always] madvise never\n");
186 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
, &transparent_hugepage_flags
))
187 return sprintf(buf
, "always [madvise] never\n");
189 return sprintf(buf
, "always madvise [never]\n");
192 static ssize_t
enabled_store(struct kobject
*kobj
,
193 struct kobj_attribute
*attr
,
194 const char *buf
, size_t count
)
198 ret
= triple_flag_store(kobj
, attr
, buf
, count
,
199 TRANSPARENT_HUGEPAGE_FLAG
,
200 TRANSPARENT_HUGEPAGE_FLAG
,
201 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
);
204 int err
= start_stop_khugepaged();
211 static struct kobj_attribute enabled_attr
=
212 __ATTR(enabled
, 0644, enabled_show
, enabled_store
);
214 ssize_t
single_hugepage_flag_show(struct kobject
*kobj
,
215 struct kobj_attribute
*attr
, char *buf
,
216 enum transparent_hugepage_flag flag
)
218 return sprintf(buf
, "%d\n",
219 !!test_bit(flag
, &transparent_hugepage_flags
));
222 ssize_t
single_hugepage_flag_store(struct kobject
*kobj
,
223 struct kobj_attribute
*attr
,
224 const char *buf
, size_t count
,
225 enum transparent_hugepage_flag flag
)
230 ret
= kstrtoul(buf
, 10, &value
);
237 set_bit(flag
, &transparent_hugepage_flags
);
239 clear_bit(flag
, &transparent_hugepage_flags
);
245 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
246 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
247 * memory just to allocate one more hugepage.
249 static ssize_t
defrag_show(struct kobject
*kobj
,
250 struct kobj_attribute
*attr
, char *buf
)
252 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
, &transparent_hugepage_flags
))
253 return sprintf(buf
, "[always] defer madvise never\n");
254 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
, &transparent_hugepage_flags
))
255 return sprintf(buf
, "always [defer] madvise never\n");
256 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
, &transparent_hugepage_flags
))
257 return sprintf(buf
, "always defer [madvise] never\n");
259 return sprintf(buf
, "always defer madvise [never]\n");
262 static ssize_t
defrag_store(struct kobject
*kobj
,
263 struct kobj_attribute
*attr
,
264 const char *buf
, size_t count
)
266 return triple_flag_store(kobj
, attr
, buf
, count
,
267 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
,
268 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
,
269 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
);
271 static struct kobj_attribute defrag_attr
=
272 __ATTR(defrag
, 0644, defrag_show
, defrag_store
);
274 static ssize_t
use_zero_page_show(struct kobject
*kobj
,
275 struct kobj_attribute
*attr
, char *buf
)
277 return single_hugepage_flag_show(kobj
, attr
, buf
,
278 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
280 static ssize_t
use_zero_page_store(struct kobject
*kobj
,
281 struct kobj_attribute
*attr
, const char *buf
, size_t count
)
283 return single_hugepage_flag_store(kobj
, attr
, buf
, count
,
284 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG
);
286 static struct kobj_attribute use_zero_page_attr
=
287 __ATTR(use_zero_page
, 0644, use_zero_page_show
, use_zero_page_store
);
289 static ssize_t
hpage_pmd_size_show(struct kobject
*kobj
,
290 struct kobj_attribute
*attr
, char *buf
)
292 return sprintf(buf
, "%lu\n", HPAGE_PMD_SIZE
);
294 static struct kobj_attribute hpage_pmd_size_attr
=
295 __ATTR_RO(hpage_pmd_size
);
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_hugepage_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_hugepage_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 &use_zero_page_attr
.attr
,
319 &hpage_pmd_size_attr
.attr
,
320 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
321 &shmem_enabled_attr
.attr
,
323 #ifdef CONFIG_DEBUG_VM
324 &debug_cow_attr
.attr
,
329 static struct attribute_group hugepage_attr_group
= {
330 .attrs
= hugepage_attr
,
333 static int __init
hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
337 *hugepage_kobj
= kobject_create_and_add("transparent_hugepage", mm_kobj
);
338 if (unlikely(!*hugepage_kobj
)) {
339 pr_err("failed to create transparent hugepage kobject\n");
343 err
= sysfs_create_group(*hugepage_kobj
, &hugepage_attr_group
);
345 pr_err("failed to register transparent hugepage group\n");
349 err
= sysfs_create_group(*hugepage_kobj
, &khugepaged_attr_group
);
351 pr_err("failed to register transparent hugepage group\n");
352 goto remove_hp_group
;
358 sysfs_remove_group(*hugepage_kobj
, &hugepage_attr_group
);
360 kobject_put(*hugepage_kobj
);
364 static void __init
hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
366 sysfs_remove_group(hugepage_kobj
, &khugepaged_attr_group
);
367 sysfs_remove_group(hugepage_kobj
, &hugepage_attr_group
);
368 kobject_put(hugepage_kobj
);
371 static inline int hugepage_init_sysfs(struct kobject
**hugepage_kobj
)
376 static inline void hugepage_exit_sysfs(struct kobject
*hugepage_kobj
)
379 #endif /* CONFIG_SYSFS */
381 static int __init
hugepage_init(void)
384 struct kobject
*hugepage_kobj
;
386 if (!has_transparent_hugepage()) {
387 transparent_hugepage_flags
= 0;
392 * hugepages can't be allocated by the buddy allocator
394 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER
>= MAX_ORDER
);
396 * we use page->mapping and page->index in second tail page
397 * as list_head: assuming THP order >= 2
399 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER
< 2);
401 err
= hugepage_init_sysfs(&hugepage_kobj
);
405 err
= khugepaged_init();
409 err
= register_shrinker(&huge_zero_page_shrinker
);
411 goto err_hzp_shrinker
;
412 err
= register_shrinker(&deferred_split_shrinker
);
414 goto err_split_shrinker
;
417 * By default disable transparent hugepages on smaller systems,
418 * where the extra memory used could hurt more than TLB overhead
419 * is likely to save. The admin can still enable it through /sys.
421 if (totalram_pages
< (512 << (20 - PAGE_SHIFT
))) {
422 transparent_hugepage_flags
= 0;
426 err
= start_stop_khugepaged();
432 unregister_shrinker(&deferred_split_shrinker
);
434 unregister_shrinker(&huge_zero_page_shrinker
);
436 khugepaged_destroy();
438 hugepage_exit_sysfs(hugepage_kobj
);
442 subsys_initcall(hugepage_init
);
444 static int __init
setup_transparent_hugepage(char *str
)
449 if (!strcmp(str
, "always")) {
450 set_bit(TRANSPARENT_HUGEPAGE_FLAG
,
451 &transparent_hugepage_flags
);
452 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
453 &transparent_hugepage_flags
);
455 } else if (!strcmp(str
, "madvise")) {
456 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
457 &transparent_hugepage_flags
);
458 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
459 &transparent_hugepage_flags
);
461 } else if (!strcmp(str
, "never")) {
462 clear_bit(TRANSPARENT_HUGEPAGE_FLAG
,
463 &transparent_hugepage_flags
);
464 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG
,
465 &transparent_hugepage_flags
);
470 pr_warn("transparent_hugepage= cannot parse, ignored\n");
473 __setup("transparent_hugepage=", setup_transparent_hugepage
);
475 pmd_t
maybe_pmd_mkwrite(pmd_t pmd
, struct vm_area_struct
*vma
)
477 if (likely(vma
->vm_flags
& VM_WRITE
))
478 pmd
= pmd_mkwrite(pmd
);
482 static inline struct list_head
*page_deferred_list(struct page
*page
)
485 * ->lru in the tail pages is occupied by compound_head.
486 * Let's use ->mapping + ->index in the second tail page as list_head.
488 return (struct list_head
*)&page
[2].mapping
;
491 void prep_transhuge_page(struct page
*page
)
494 * we use page->mapping and page->indexlru in second tail page
495 * as list_head: assuming THP order >= 2
498 INIT_LIST_HEAD(page_deferred_list(page
));
499 set_compound_page_dtor(page
, TRANSHUGE_PAGE_DTOR
);
502 unsigned long __thp_get_unmapped_area(struct file
*filp
, unsigned long len
,
503 loff_t off
, unsigned long flags
, unsigned long size
)
506 loff_t off_end
= off
+ len
;
507 loff_t off_align
= round_up(off
, size
);
508 unsigned long len_pad
;
510 if (off_end
<= off_align
|| (off_end
- off_align
) < size
)
513 len_pad
= len
+ size
;
514 if (len_pad
< len
|| (off
+ len_pad
) < off
)
517 addr
= current
->mm
->get_unmapped_area(filp
, 0, len_pad
,
518 off
>> PAGE_SHIFT
, flags
);
519 if (IS_ERR_VALUE(addr
))
522 addr
+= (off
- addr
) & (size
- 1);
526 unsigned long thp_get_unmapped_area(struct file
*filp
, unsigned long addr
,
527 unsigned long len
, unsigned long pgoff
, unsigned long flags
)
529 loff_t off
= (loff_t
)pgoff
<< PAGE_SHIFT
;
533 if (!IS_DAX(filp
->f_mapping
->host
) || !IS_ENABLED(CONFIG_FS_DAX_PMD
))
536 addr
= __thp_get_unmapped_area(filp
, len
, off
, flags
, PMD_SIZE
);
541 return current
->mm
->get_unmapped_area(filp
, addr
, len
, pgoff
, flags
);
543 EXPORT_SYMBOL_GPL(thp_get_unmapped_area
);
545 static int __do_huge_pmd_anonymous_page(struct vm_fault
*vmf
, struct page
*page
,
548 struct vm_area_struct
*vma
= vmf
->vma
;
549 struct mem_cgroup
*memcg
;
551 unsigned long haddr
= vmf
->address
& HPAGE_PMD_MASK
;
553 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
555 if (mem_cgroup_try_charge(page
, vma
->vm_mm
, gfp
, &memcg
, true)) {
557 count_vm_event(THP_FAULT_FALLBACK
);
558 return VM_FAULT_FALLBACK
;
561 pgtable
= pte_alloc_one(vma
->vm_mm
, haddr
);
562 if (unlikely(!pgtable
)) {
563 mem_cgroup_cancel_charge(page
, memcg
, true);
568 clear_huge_page(page
, haddr
, HPAGE_PMD_NR
);
570 * The memory barrier inside __SetPageUptodate makes sure that
571 * clear_huge_page writes become visible before the set_pmd_at()
574 __SetPageUptodate(page
);
576 vmf
->ptl
= pmd_lock(vma
->vm_mm
, vmf
->pmd
);
577 if (unlikely(!pmd_none(*vmf
->pmd
))) {
578 spin_unlock(vmf
->ptl
);
579 mem_cgroup_cancel_charge(page
, memcg
, true);
581 pte_free(vma
->vm_mm
, pgtable
);
585 /* Deliver the page fault to userland */
586 if (userfaultfd_missing(vma
)) {
589 spin_unlock(vmf
->ptl
);
590 mem_cgroup_cancel_charge(page
, memcg
, true);
592 pte_free(vma
->vm_mm
, pgtable
);
593 ret
= handle_userfault(vmf
, VM_UFFD_MISSING
);
594 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
598 entry
= mk_huge_pmd(page
, vma
->vm_page_prot
);
599 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
600 page_add_new_anon_rmap(page
, vma
, haddr
, true);
601 mem_cgroup_commit_charge(page
, memcg
, false, true);
602 lru_cache_add_active_or_unevictable(page
, vma
);
603 pgtable_trans_huge_deposit(vma
->vm_mm
, vmf
->pmd
, pgtable
);
604 set_pmd_at(vma
->vm_mm
, haddr
, vmf
->pmd
, entry
);
605 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
606 atomic_long_inc(&vma
->vm_mm
->nr_ptes
);
607 spin_unlock(vmf
->ptl
);
608 count_vm_event(THP_FAULT_ALLOC
);
615 * If THP defrag is set to always then directly reclaim/compact as necessary
616 * If set to defer then do only background reclaim/compact and defer to khugepaged
617 * If set to madvise and the VMA is flagged then directly reclaim/compact
618 * When direct reclaim/compact is allowed, don't retry except for flagged VMA's
620 static inline gfp_t
alloc_hugepage_direct_gfpmask(struct vm_area_struct
*vma
)
622 bool vma_madvised
= !!(vma
->vm_flags
& VM_HUGEPAGE
);
624 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG
,
625 &transparent_hugepage_flags
) && vma_madvised
)
626 return GFP_TRANSHUGE
;
627 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG
,
628 &transparent_hugepage_flags
))
629 return GFP_TRANSHUGE_LIGHT
| __GFP_KSWAPD_RECLAIM
;
630 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG
,
631 &transparent_hugepage_flags
))
632 return GFP_TRANSHUGE
| (vma_madvised
? 0 : __GFP_NORETRY
);
634 return GFP_TRANSHUGE_LIGHT
;
637 /* Caller must hold page table lock. */
638 static bool set_huge_zero_page(pgtable_t pgtable
, struct mm_struct
*mm
,
639 struct vm_area_struct
*vma
, unsigned long haddr
, pmd_t
*pmd
,
640 struct page
*zero_page
)
645 entry
= mk_pmd(zero_page
, vma
->vm_page_prot
);
646 entry
= pmd_mkhuge(entry
);
648 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
649 set_pmd_at(mm
, haddr
, pmd
, entry
);
650 atomic_long_inc(&mm
->nr_ptes
);
654 int do_huge_pmd_anonymous_page(struct vm_fault
*vmf
)
656 struct vm_area_struct
*vma
= vmf
->vma
;
659 unsigned long haddr
= vmf
->address
& HPAGE_PMD_MASK
;
661 if (haddr
< vma
->vm_start
|| haddr
+ HPAGE_PMD_SIZE
> vma
->vm_end
)
662 return VM_FAULT_FALLBACK
;
663 if (stack_guard_area(vma
, haddr
) ||
664 stack_guard_area(vma
, haddr
+ HPAGE_PMD_SIZE
))
665 return VM_FAULT_FALLBACK
;
666 if (unlikely(anon_vma_prepare(vma
)))
668 if (unlikely(khugepaged_enter(vma
, vma
->vm_flags
)))
670 if (!(vmf
->flags
& FAULT_FLAG_WRITE
) &&
671 !mm_forbids_zeropage(vma
->vm_mm
) &&
672 transparent_hugepage_use_zero_page()) {
674 struct page
*zero_page
;
677 pgtable
= pte_alloc_one(vma
->vm_mm
, haddr
);
678 if (unlikely(!pgtable
))
680 zero_page
= mm_get_huge_zero_page(vma
->vm_mm
);
681 if (unlikely(!zero_page
)) {
682 pte_free(vma
->vm_mm
, pgtable
);
683 count_vm_event(THP_FAULT_FALLBACK
);
684 return VM_FAULT_FALLBACK
;
686 vmf
->ptl
= pmd_lock(vma
->vm_mm
, vmf
->pmd
);
689 if (pmd_none(*vmf
->pmd
)) {
690 if (userfaultfd_missing(vma
)) {
691 spin_unlock(vmf
->ptl
);
692 ret
= handle_userfault(vmf
, VM_UFFD_MISSING
);
693 VM_BUG_ON(ret
& VM_FAULT_FALLBACK
);
695 set_huge_zero_page(pgtable
, vma
->vm_mm
, vma
,
696 haddr
, vmf
->pmd
, zero_page
);
697 spin_unlock(vmf
->ptl
);
701 spin_unlock(vmf
->ptl
);
703 pte_free(vma
->vm_mm
, pgtable
);
706 gfp
= alloc_hugepage_direct_gfpmask(vma
);
707 page
= alloc_hugepage_vma(gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
708 if (unlikely(!page
)) {
709 count_vm_event(THP_FAULT_FALLBACK
);
710 return VM_FAULT_FALLBACK
;
712 prep_transhuge_page(page
);
713 return __do_huge_pmd_anonymous_page(vmf
, page
, gfp
);
716 static void insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
717 pmd_t
*pmd
, pfn_t pfn
, pgprot_t prot
, bool write
)
719 struct mm_struct
*mm
= vma
->vm_mm
;
723 ptl
= pmd_lock(mm
, pmd
);
724 entry
= pmd_mkhuge(pfn_t_pmd(pfn
, prot
));
725 if (pfn_t_devmap(pfn
))
726 entry
= pmd_mkdevmap(entry
);
728 entry
= pmd_mkyoung(pmd_mkdirty(entry
));
729 entry
= maybe_pmd_mkwrite(entry
, vma
);
731 set_pmd_at(mm
, addr
, pmd
, entry
);
732 update_mmu_cache_pmd(vma
, addr
, pmd
);
736 int vmf_insert_pfn_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
737 pmd_t
*pmd
, pfn_t pfn
, bool write
)
739 pgprot_t pgprot
= vma
->vm_page_prot
;
741 * If we had pmd_special, we could avoid all these restrictions,
742 * but we need to be consistent with PTEs and architectures that
743 * can't support a 'special' bit.
745 BUG_ON(!(vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)));
746 BUG_ON((vma
->vm_flags
& (VM_PFNMAP
|VM_MIXEDMAP
)) ==
747 (VM_PFNMAP
|VM_MIXEDMAP
));
748 BUG_ON((vma
->vm_flags
& VM_PFNMAP
) && is_cow_mapping(vma
->vm_flags
));
749 BUG_ON(!pfn_t_devmap(pfn
));
751 if (addr
< vma
->vm_start
|| addr
>= vma
->vm_end
)
752 return VM_FAULT_SIGBUS
;
754 track_pfn_insert(vma
, &pgprot
, pfn
);
756 insert_pfn_pmd(vma
, addr
, pmd
, pfn
, pgprot
, write
);
757 return VM_FAULT_NOPAGE
;
759 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd
);
761 static void touch_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
767 * We should set the dirty bit only for FOLL_WRITE but for now
768 * the dirty bit in the pmd is meaningless. And if the dirty
769 * bit will become meaningful and we'll only set it with
770 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
771 * set the young bit, instead of the current set_pmd_at.
773 _pmd
= pmd_mkyoung(pmd_mkdirty(*pmd
));
774 if (pmdp_set_access_flags(vma
, addr
& HPAGE_PMD_MASK
,
776 update_mmu_cache_pmd(vma
, addr
, pmd
);
779 struct page
*follow_devmap_pmd(struct vm_area_struct
*vma
, unsigned long addr
,
780 pmd_t
*pmd
, int flags
)
782 unsigned long pfn
= pmd_pfn(*pmd
);
783 struct mm_struct
*mm
= vma
->vm_mm
;
784 struct dev_pagemap
*pgmap
;
787 assert_spin_locked(pmd_lockptr(mm
, pmd
));
790 * When we COW a devmap PMD entry, we split it into PTEs, so we should
791 * not be in this function with `flags & FOLL_COW` set.
793 WARN_ONCE(flags
& FOLL_COW
, "mm: In follow_devmap_pmd with FOLL_COW set");
795 if (flags
& FOLL_WRITE
&& !pmd_write(*pmd
))
798 if (pmd_present(*pmd
) && pmd_devmap(*pmd
))
803 if (flags
& FOLL_TOUCH
)
804 touch_pmd(vma
, addr
, pmd
);
807 * device mapped pages can only be returned if the
808 * caller will manage the page reference count.
810 if (!(flags
& FOLL_GET
))
811 return ERR_PTR(-EEXIST
);
813 pfn
+= (addr
& ~PMD_MASK
) >> PAGE_SHIFT
;
814 pgmap
= get_dev_pagemap(pfn
, NULL
);
816 return ERR_PTR(-EFAULT
);
817 page
= pfn_to_page(pfn
);
819 put_dev_pagemap(pgmap
);
824 int copy_huge_pmd(struct mm_struct
*dst_mm
, struct mm_struct
*src_mm
,
825 pmd_t
*dst_pmd
, pmd_t
*src_pmd
, unsigned long addr
,
826 struct vm_area_struct
*vma
)
828 spinlock_t
*dst_ptl
, *src_ptl
;
829 struct page
*src_page
;
831 pgtable_t pgtable
= NULL
;
834 /* Skip if can be re-fill on fault */
835 if (!vma_is_anonymous(vma
))
838 pgtable
= pte_alloc_one(dst_mm
, addr
);
839 if (unlikely(!pgtable
))
842 dst_ptl
= pmd_lock(dst_mm
, dst_pmd
);
843 src_ptl
= pmd_lockptr(src_mm
, src_pmd
);
844 spin_lock_nested(src_ptl
, SINGLE_DEPTH_NESTING
);
848 if (unlikely(!pmd_trans_huge(pmd
))) {
849 pte_free(dst_mm
, pgtable
);
853 * When page table lock is held, the huge zero pmd should not be
854 * under splitting since we don't split the page itself, only pmd to
857 if (is_huge_zero_pmd(pmd
)) {
858 struct page
*zero_page
;
860 * get_huge_zero_page() will never allocate a new page here,
861 * since we already have a zero page to copy. It just takes a
864 zero_page
= mm_get_huge_zero_page(dst_mm
);
865 set_huge_zero_page(pgtable
, dst_mm
, vma
, addr
, dst_pmd
,
871 src_page
= pmd_page(pmd
);
872 VM_BUG_ON_PAGE(!PageHead(src_page
), src_page
);
874 page_dup_rmap(src_page
, true);
875 add_mm_counter(dst_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
876 atomic_long_inc(&dst_mm
->nr_ptes
);
877 pgtable_trans_huge_deposit(dst_mm
, dst_pmd
, pgtable
);
879 pmdp_set_wrprotect(src_mm
, addr
, src_pmd
);
880 pmd
= pmd_mkold(pmd_wrprotect(pmd
));
881 set_pmd_at(dst_mm
, addr
, dst_pmd
, pmd
);
885 spin_unlock(src_ptl
);
886 spin_unlock(dst_ptl
);
891 void huge_pmd_set_accessed(struct vm_fault
*vmf
, pmd_t orig_pmd
)
895 bool write
= vmf
->flags
& FAULT_FLAG_WRITE
;
897 vmf
->ptl
= pmd_lock(vmf
->vma
->vm_mm
, vmf
->pmd
);
898 if (unlikely(!pmd_same(*vmf
->pmd
, orig_pmd
)))
901 entry
= pmd_mkyoung(orig_pmd
);
903 entry
= pmd_mkdirty(entry
);
904 haddr
= vmf
->address
& HPAGE_PMD_MASK
;
905 if (pmdp_set_access_flags(vmf
->vma
, haddr
, vmf
->pmd
, entry
, write
))
906 update_mmu_cache_pmd(vmf
->vma
, vmf
->address
, vmf
->pmd
);
909 spin_unlock(vmf
->ptl
);
912 static int do_huge_pmd_wp_page_fallback(struct vm_fault
*vmf
, pmd_t orig_pmd
,
915 struct vm_area_struct
*vma
= vmf
->vma
;
916 unsigned long haddr
= vmf
->address
& HPAGE_PMD_MASK
;
917 struct mem_cgroup
*memcg
;
922 unsigned long mmun_start
; /* For mmu_notifiers */
923 unsigned long mmun_end
; /* For mmu_notifiers */
925 pages
= kmalloc(sizeof(struct page
*) * HPAGE_PMD_NR
,
927 if (unlikely(!pages
)) {
932 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
933 pages
[i
] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE
, vma
,
934 vmf
->address
, page_to_nid(page
));
935 if (unlikely(!pages
[i
] ||
936 mem_cgroup_try_charge(pages
[i
], vma
->vm_mm
,
937 GFP_KERNEL
, &memcg
, false))) {
941 memcg
= (void *)page_private(pages
[i
]);
942 set_page_private(pages
[i
], 0);
943 mem_cgroup_cancel_charge(pages
[i
], memcg
,
951 set_page_private(pages
[i
], (unsigned long)memcg
);
954 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
955 copy_user_highpage(pages
[i
], page
+ i
,
956 haddr
+ PAGE_SIZE
* i
, vma
);
957 __SetPageUptodate(pages
[i
]);
962 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
963 mmu_notifier_invalidate_range_start(vma
->vm_mm
, mmun_start
, mmun_end
);
965 vmf
->ptl
= pmd_lock(vma
->vm_mm
, vmf
->pmd
);
966 if (unlikely(!pmd_same(*vmf
->pmd
, orig_pmd
)))
968 VM_BUG_ON_PAGE(!PageHead(page
), page
);
970 pmdp_huge_clear_flush_notify(vma
, haddr
, vmf
->pmd
);
971 /* leave pmd empty until pte is filled */
973 pgtable
= pgtable_trans_huge_withdraw(vma
->vm_mm
, vmf
->pmd
);
974 pmd_populate(vma
->vm_mm
, &_pmd
, pgtable
);
976 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
978 entry
= mk_pte(pages
[i
], vma
->vm_page_prot
);
979 entry
= maybe_mkwrite(pte_mkdirty(entry
), vma
);
980 memcg
= (void *)page_private(pages
[i
]);
981 set_page_private(pages
[i
], 0);
982 page_add_new_anon_rmap(pages
[i
], vmf
->vma
, haddr
, false);
983 mem_cgroup_commit_charge(pages
[i
], memcg
, false, false);
984 lru_cache_add_active_or_unevictable(pages
[i
], vma
);
985 vmf
->pte
= pte_offset_map(&_pmd
, haddr
);
986 VM_BUG_ON(!pte_none(*vmf
->pte
));
987 set_pte_at(vma
->vm_mm
, haddr
, vmf
->pte
, entry
);
992 smp_wmb(); /* make pte visible before pmd */
993 pmd_populate(vma
->vm_mm
, vmf
->pmd
, pgtable
);
994 page_remove_rmap(page
, true);
995 spin_unlock(vmf
->ptl
);
997 mmu_notifier_invalidate_range_end(vma
->vm_mm
, mmun_start
, mmun_end
);
999 ret
|= VM_FAULT_WRITE
;
1006 spin_unlock(vmf
->ptl
);
1007 mmu_notifier_invalidate_range_end(vma
->vm_mm
, mmun_start
, mmun_end
);
1008 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1009 memcg
= (void *)page_private(pages
[i
]);
1010 set_page_private(pages
[i
], 0);
1011 mem_cgroup_cancel_charge(pages
[i
], memcg
, false);
1018 int do_huge_pmd_wp_page(struct vm_fault
*vmf
, pmd_t orig_pmd
)
1020 struct vm_area_struct
*vma
= vmf
->vma
;
1021 struct page
*page
= NULL
, *new_page
;
1022 struct mem_cgroup
*memcg
;
1023 unsigned long haddr
= vmf
->address
& HPAGE_PMD_MASK
;
1024 unsigned long mmun_start
; /* For mmu_notifiers */
1025 unsigned long mmun_end
; /* For mmu_notifiers */
1026 gfp_t huge_gfp
; /* for allocation and charge */
1029 vmf
->ptl
= pmd_lockptr(vma
->vm_mm
, vmf
->pmd
);
1030 VM_BUG_ON_VMA(!vma
->anon_vma
, vma
);
1031 if (is_huge_zero_pmd(orig_pmd
))
1033 spin_lock(vmf
->ptl
);
1034 if (unlikely(!pmd_same(*vmf
->pmd
, orig_pmd
)))
1037 page
= pmd_page(orig_pmd
);
1038 VM_BUG_ON_PAGE(!PageCompound(page
) || !PageHead(page
), page
);
1040 * We can only reuse the page if nobody else maps the huge page or it's
1043 if (page_trans_huge_mapcount(page
, NULL
) == 1) {
1045 entry
= pmd_mkyoung(orig_pmd
);
1046 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1047 if (pmdp_set_access_flags(vma
, haddr
, vmf
->pmd
, entry
, 1))
1048 update_mmu_cache_pmd(vma
, vmf
->address
, vmf
->pmd
);
1049 ret
|= VM_FAULT_WRITE
;
1053 spin_unlock(vmf
->ptl
);
1055 if (transparent_hugepage_enabled(vma
) &&
1056 !transparent_hugepage_debug_cow()) {
1057 huge_gfp
= alloc_hugepage_direct_gfpmask(vma
);
1058 new_page
= alloc_hugepage_vma(huge_gfp
, vma
, haddr
, HPAGE_PMD_ORDER
);
1062 if (likely(new_page
)) {
1063 prep_transhuge_page(new_page
);
1066 split_huge_pmd(vma
, vmf
->pmd
, vmf
->address
);
1067 ret
|= VM_FAULT_FALLBACK
;
1069 ret
= do_huge_pmd_wp_page_fallback(vmf
, orig_pmd
, page
);
1070 if (ret
& VM_FAULT_OOM
) {
1071 split_huge_pmd(vma
, vmf
->pmd
, vmf
->address
);
1072 ret
|= VM_FAULT_FALLBACK
;
1076 count_vm_event(THP_FAULT_FALLBACK
);
1080 if (unlikely(mem_cgroup_try_charge(new_page
, vma
->vm_mm
,
1081 huge_gfp
, &memcg
, true))) {
1083 split_huge_pmd(vma
, vmf
->pmd
, vmf
->address
);
1086 ret
|= VM_FAULT_FALLBACK
;
1087 count_vm_event(THP_FAULT_FALLBACK
);
1091 count_vm_event(THP_FAULT_ALLOC
);
1094 clear_huge_page(new_page
, haddr
, HPAGE_PMD_NR
);
1096 copy_user_huge_page(new_page
, page
, haddr
, vma
, HPAGE_PMD_NR
);
1097 __SetPageUptodate(new_page
);
1100 mmun_end
= haddr
+ HPAGE_PMD_SIZE
;
1101 mmu_notifier_invalidate_range_start(vma
->vm_mm
, mmun_start
, mmun_end
);
1103 spin_lock(vmf
->ptl
);
1106 if (unlikely(!pmd_same(*vmf
->pmd
, orig_pmd
))) {
1107 spin_unlock(vmf
->ptl
);
1108 mem_cgroup_cancel_charge(new_page
, memcg
, true);
1113 entry
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1114 entry
= maybe_pmd_mkwrite(pmd_mkdirty(entry
), vma
);
1115 pmdp_huge_clear_flush_notify(vma
, haddr
, vmf
->pmd
);
1116 page_add_new_anon_rmap(new_page
, vma
, haddr
, true);
1117 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
1118 lru_cache_add_active_or_unevictable(new_page
, vma
);
1119 set_pmd_at(vma
->vm_mm
, haddr
, vmf
->pmd
, entry
);
1120 update_mmu_cache_pmd(vma
, vmf
->address
, vmf
->pmd
);
1122 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, HPAGE_PMD_NR
);
1124 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1125 page_remove_rmap(page
, true);
1128 ret
|= VM_FAULT_WRITE
;
1130 spin_unlock(vmf
->ptl
);
1132 mmu_notifier_invalidate_range_end(vma
->vm_mm
, mmun_start
, mmun_end
);
1136 spin_unlock(vmf
->ptl
);
1141 * FOLL_FORCE can write to even unwritable pmd's, but only
1142 * after we've gone through a COW cycle and they are dirty.
1144 static inline bool can_follow_write_pmd(pmd_t pmd
, unsigned int flags
)
1146 return pmd_write(pmd
) ||
1147 ((flags
& FOLL_FORCE
) && (flags
& FOLL_COW
) && pmd_dirty(pmd
));
1150 struct page
*follow_trans_huge_pmd(struct vm_area_struct
*vma
,
1155 struct mm_struct
*mm
= vma
->vm_mm
;
1156 struct page
*page
= NULL
;
1158 assert_spin_locked(pmd_lockptr(mm
, pmd
));
1160 if (flags
& FOLL_WRITE
&& !can_follow_write_pmd(*pmd
, flags
))
1163 /* Avoid dumping huge zero page */
1164 if ((flags
& FOLL_DUMP
) && is_huge_zero_pmd(*pmd
))
1165 return ERR_PTR(-EFAULT
);
1167 /* Full NUMA hinting faults to serialise migration in fault paths */
1168 if ((flags
& FOLL_NUMA
) && pmd_protnone(*pmd
))
1171 page
= pmd_page(*pmd
);
1172 VM_BUG_ON_PAGE(!PageHead(page
) && !is_zone_device_page(page
), page
);
1173 if (flags
& FOLL_TOUCH
)
1174 touch_pmd(vma
, addr
, pmd
);
1175 if ((flags
& FOLL_MLOCK
) && (vma
->vm_flags
& VM_LOCKED
)) {
1177 * We don't mlock() pte-mapped THPs. This way we can avoid
1178 * leaking mlocked pages into non-VM_LOCKED VMAs.
1182 * In most cases the pmd is the only mapping of the page as we
1183 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1184 * writable private mappings in populate_vma_page_range().
1186 * The only scenario when we have the page shared here is if we
1187 * mlocking read-only mapping shared over fork(). We skip
1188 * mlocking such pages.
1192 * We can expect PageDoubleMap() to be stable under page lock:
1193 * for file pages we set it in page_add_file_rmap(), which
1194 * requires page to be locked.
1197 if (PageAnon(page
) && compound_mapcount(page
) != 1)
1199 if (PageDoubleMap(page
) || !page
->mapping
)
1201 if (!trylock_page(page
))
1204 if (page
->mapping
&& !PageDoubleMap(page
))
1205 mlock_vma_page(page
);
1209 page
+= (addr
& ~HPAGE_PMD_MASK
) >> PAGE_SHIFT
;
1210 VM_BUG_ON_PAGE(!PageCompound(page
) && !is_zone_device_page(page
), page
);
1211 if (flags
& FOLL_GET
)
1218 /* NUMA hinting page fault entry point for trans huge pmds */
1219 int do_huge_pmd_numa_page(struct vm_fault
*vmf
, pmd_t pmd
)
1221 struct vm_area_struct
*vma
= vmf
->vma
;
1222 struct anon_vma
*anon_vma
= NULL
;
1224 unsigned long haddr
= vmf
->address
& HPAGE_PMD_MASK
;
1225 int page_nid
= -1, this_nid
= numa_node_id();
1226 int target_nid
, last_cpupid
= -1;
1228 bool migrated
= false;
1232 vmf
->ptl
= pmd_lock(vma
->vm_mm
, vmf
->pmd
);
1233 if (unlikely(!pmd_same(pmd
, *vmf
->pmd
)))
1237 * If there are potential migrations, wait for completion and retry
1238 * without disrupting NUMA hinting information. Do not relock and
1239 * check_same as the page may no longer be mapped.
1241 if (unlikely(pmd_trans_migrating(*vmf
->pmd
))) {
1242 page
= pmd_page(*vmf
->pmd
);
1243 spin_unlock(vmf
->ptl
);
1244 wait_on_page_locked(page
);
1248 page
= pmd_page(pmd
);
1249 BUG_ON(is_huge_zero_page(page
));
1250 page_nid
= page_to_nid(page
);
1251 last_cpupid
= page_cpupid_last(page
);
1252 count_vm_numa_event(NUMA_HINT_FAULTS
);
1253 if (page_nid
== this_nid
) {
1254 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL
);
1255 flags
|= TNF_FAULT_LOCAL
;
1258 /* See similar comment in do_numa_page for explanation */
1259 if (!pmd_savedwrite(pmd
))
1260 flags
|= TNF_NO_GROUP
;
1263 * Acquire the page lock to serialise THP migrations but avoid dropping
1264 * page_table_lock if at all possible
1266 page_locked
= trylock_page(page
);
1267 target_nid
= mpol_misplaced(page
, vma
, haddr
);
1268 if (target_nid
== -1) {
1269 /* If the page was locked, there are no parallel migrations */
1274 /* Migration could have started since the pmd_trans_migrating check */
1276 spin_unlock(vmf
->ptl
);
1277 wait_on_page_locked(page
);
1283 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1284 * to serialises splits
1287 spin_unlock(vmf
->ptl
);
1288 anon_vma
= page_lock_anon_vma_read(page
);
1290 /* Confirm the PMD did not change while page_table_lock was released */
1291 spin_lock(vmf
->ptl
);
1292 if (unlikely(!pmd_same(pmd
, *vmf
->pmd
))) {
1299 /* Bail if we fail to protect against THP splits for any reason */
1300 if (unlikely(!anon_vma
)) {
1307 * Migrate the THP to the requested node, returns with page unlocked
1308 * and access rights restored.
1310 spin_unlock(vmf
->ptl
);
1311 migrated
= migrate_misplaced_transhuge_page(vma
->vm_mm
, vma
,
1312 vmf
->pmd
, pmd
, vmf
->address
, page
, target_nid
);
1314 flags
|= TNF_MIGRATED
;
1315 page_nid
= target_nid
;
1317 flags
|= TNF_MIGRATE_FAIL
;
1321 BUG_ON(!PageLocked(page
));
1322 was_writable
= pmd_savedwrite(pmd
);
1323 pmd
= pmd_modify(pmd
, vma
->vm_page_prot
);
1324 pmd
= pmd_mkyoung(pmd
);
1326 pmd
= pmd_mkwrite(pmd
);
1327 set_pmd_at(vma
->vm_mm
, haddr
, vmf
->pmd
, pmd
);
1328 update_mmu_cache_pmd(vma
, vmf
->address
, vmf
->pmd
);
1331 spin_unlock(vmf
->ptl
);
1335 page_unlock_anon_vma_read(anon_vma
);
1338 task_numa_fault(last_cpupid
, page_nid
, HPAGE_PMD_NR
,
1345 * Return true if we do MADV_FREE successfully on entire pmd page.
1346 * Otherwise, return false.
1348 bool madvise_free_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1349 pmd_t
*pmd
, unsigned long addr
, unsigned long next
)
1354 struct mm_struct
*mm
= tlb
->mm
;
1357 tlb_remove_check_page_size_change(tlb
, HPAGE_PMD_SIZE
);
1359 ptl
= pmd_trans_huge_lock(pmd
, vma
);
1364 if (is_huge_zero_pmd(orig_pmd
))
1367 page
= pmd_page(orig_pmd
);
1369 * If other processes are mapping this page, we couldn't discard
1370 * the page unless they all do MADV_FREE so let's skip the page.
1372 if (page_mapcount(page
) != 1)
1375 if (!trylock_page(page
))
1379 * If user want to discard part-pages of THP, split it so MADV_FREE
1380 * will deactivate only them.
1382 if (next
- addr
!= HPAGE_PMD_SIZE
) {
1385 split_huge_page(page
);
1391 if (PageDirty(page
))
1392 ClearPageDirty(page
);
1395 if (PageActive(page
))
1396 deactivate_page(page
);
1398 if (pmd_young(orig_pmd
) || pmd_dirty(orig_pmd
)) {
1399 pmdp_invalidate(vma
, addr
, pmd
);
1400 orig_pmd
= pmd_mkold(orig_pmd
);
1401 orig_pmd
= pmd_mkclean(orig_pmd
);
1403 set_pmd_at(mm
, addr
, pmd
, orig_pmd
);
1404 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1413 static inline void zap_deposited_table(struct mm_struct
*mm
, pmd_t
*pmd
)
1417 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
1418 pte_free(mm
, pgtable
);
1419 atomic_long_dec(&mm
->nr_ptes
);
1422 int zap_huge_pmd(struct mmu_gather
*tlb
, struct vm_area_struct
*vma
,
1423 pmd_t
*pmd
, unsigned long addr
)
1428 tlb_remove_check_page_size_change(tlb
, HPAGE_PMD_SIZE
);
1430 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1434 * For architectures like ppc64 we look at deposited pgtable
1435 * when calling pmdp_huge_get_and_clear. So do the
1436 * pgtable_trans_huge_withdraw after finishing pmdp related
1439 orig_pmd
= pmdp_huge_get_and_clear_full(tlb
->mm
, addr
, pmd
,
1441 tlb_remove_pmd_tlb_entry(tlb
, pmd
, addr
);
1442 if (vma_is_dax(vma
)) {
1444 if (is_huge_zero_pmd(orig_pmd
))
1445 tlb_remove_page_size(tlb
, pmd_page(orig_pmd
), HPAGE_PMD_SIZE
);
1446 } else if (is_huge_zero_pmd(orig_pmd
)) {
1447 pte_free(tlb
->mm
, pgtable_trans_huge_withdraw(tlb
->mm
, pmd
));
1448 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1450 tlb_remove_page_size(tlb
, pmd_page(orig_pmd
), HPAGE_PMD_SIZE
);
1452 struct page
*page
= pmd_page(orig_pmd
);
1453 page_remove_rmap(page
, true);
1454 VM_BUG_ON_PAGE(page_mapcount(page
) < 0, page
);
1455 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1456 if (PageAnon(page
)) {
1458 pgtable
= pgtable_trans_huge_withdraw(tlb
->mm
, pmd
);
1459 pte_free(tlb
->mm
, pgtable
);
1460 atomic_long_dec(&tlb
->mm
->nr_ptes
);
1461 add_mm_counter(tlb
->mm
, MM_ANONPAGES
, -HPAGE_PMD_NR
);
1463 if (arch_needs_pgtable_deposit())
1464 zap_deposited_table(tlb
->mm
, pmd
);
1465 add_mm_counter(tlb
->mm
, MM_FILEPAGES
, -HPAGE_PMD_NR
);
1468 tlb_remove_page_size(tlb
, page
, HPAGE_PMD_SIZE
);
1473 #ifndef pmd_move_must_withdraw
1474 static inline int pmd_move_must_withdraw(spinlock_t
*new_pmd_ptl
,
1475 spinlock_t
*old_pmd_ptl
,
1476 struct vm_area_struct
*vma
)
1479 * With split pmd lock we also need to move preallocated
1480 * PTE page table if new_pmd is on different PMD page table.
1482 * We also don't deposit and withdraw tables for file pages.
1484 return (new_pmd_ptl
!= old_pmd_ptl
) && vma_is_anonymous(vma
);
1488 bool move_huge_pmd(struct vm_area_struct
*vma
, unsigned long old_addr
,
1489 unsigned long new_addr
, unsigned long old_end
,
1490 pmd_t
*old_pmd
, pmd_t
*new_pmd
, bool *need_flush
)
1492 spinlock_t
*old_ptl
, *new_ptl
;
1494 struct mm_struct
*mm
= vma
->vm_mm
;
1495 bool force_flush
= false;
1497 if ((old_addr
& ~HPAGE_PMD_MASK
) ||
1498 (new_addr
& ~HPAGE_PMD_MASK
) ||
1499 old_end
- old_addr
< HPAGE_PMD_SIZE
)
1503 * The destination pmd shouldn't be established, free_pgtables()
1504 * should have release it.
1506 if (WARN_ON(!pmd_none(*new_pmd
))) {
1507 VM_BUG_ON(pmd_trans_huge(*new_pmd
));
1512 * We don't have to worry about the ordering of src and dst
1513 * ptlocks because exclusive mmap_sem prevents deadlock.
1515 old_ptl
= __pmd_trans_huge_lock(old_pmd
, vma
);
1517 new_ptl
= pmd_lockptr(mm
, new_pmd
);
1518 if (new_ptl
!= old_ptl
)
1519 spin_lock_nested(new_ptl
, SINGLE_DEPTH_NESTING
);
1520 pmd
= pmdp_huge_get_and_clear(mm
, old_addr
, old_pmd
);
1521 if (pmd_present(pmd
) && pmd_dirty(pmd
))
1523 VM_BUG_ON(!pmd_none(*new_pmd
));
1525 if (pmd_move_must_withdraw(new_ptl
, old_ptl
, vma
)) {
1527 pgtable
= pgtable_trans_huge_withdraw(mm
, old_pmd
);
1528 pgtable_trans_huge_deposit(mm
, new_pmd
, pgtable
);
1530 set_pmd_at(mm
, new_addr
, new_pmd
, pmd_mksoft_dirty(pmd
));
1531 if (new_ptl
!= old_ptl
)
1532 spin_unlock(new_ptl
);
1534 flush_tlb_range(vma
, old_addr
, old_addr
+ PMD_SIZE
);
1537 spin_unlock(old_ptl
);
1545 * - 0 if PMD could not be locked
1546 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1547 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1549 int change_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1550 unsigned long addr
, pgprot_t newprot
, int prot_numa
)
1552 struct mm_struct
*mm
= vma
->vm_mm
;
1556 ptl
= __pmd_trans_huge_lock(pmd
, vma
);
1559 bool preserve_write
= prot_numa
&& pmd_write(*pmd
);
1563 * Avoid trapping faults against the zero page. The read-only
1564 * data is likely to be read-cached on the local CPU and
1565 * local/remote hits to the zero page are not interesting.
1567 if (prot_numa
&& is_huge_zero_pmd(*pmd
)) {
1572 if (!prot_numa
|| !pmd_protnone(*pmd
)) {
1573 entry
= pmdp_huge_get_and_clear_notify(mm
, addr
, pmd
);
1574 entry
= pmd_modify(entry
, newprot
);
1576 entry
= pmd_mk_savedwrite(entry
);
1578 set_pmd_at(mm
, addr
, pmd
, entry
);
1579 BUG_ON(vma_is_anonymous(vma
) && !preserve_write
&&
1589 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1591 * Note that if it returns page table lock pointer, this routine returns without
1592 * unlocking page table lock. So callers must unlock it.
1594 spinlock_t
*__pmd_trans_huge_lock(pmd_t
*pmd
, struct vm_area_struct
*vma
)
1597 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1598 if (likely(pmd_trans_huge(*pmd
) || pmd_devmap(*pmd
)))
1604 static void __split_huge_zero_page_pmd(struct vm_area_struct
*vma
,
1605 unsigned long haddr
, pmd_t
*pmd
)
1607 struct mm_struct
*mm
= vma
->vm_mm
;
1612 /* leave pmd empty until pte is filled */
1613 pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1615 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
1616 pmd_populate(mm
, &_pmd
, pgtable
);
1618 for (i
= 0; i
< HPAGE_PMD_NR
; i
++, haddr
+= PAGE_SIZE
) {
1620 entry
= pfn_pte(my_zero_pfn(haddr
), vma
->vm_page_prot
);
1621 entry
= pte_mkspecial(entry
);
1622 pte
= pte_offset_map(&_pmd
, haddr
);
1623 VM_BUG_ON(!pte_none(*pte
));
1624 set_pte_at(mm
, haddr
, pte
, entry
);
1627 smp_wmb(); /* make pte visible before pmd */
1628 pmd_populate(mm
, pmd
, pgtable
);
1631 static void __split_huge_pmd_locked(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1632 unsigned long haddr
, bool freeze
)
1634 struct mm_struct
*mm
= vma
->vm_mm
;
1638 bool young
, write
, dirty
, soft_dirty
;
1642 VM_BUG_ON(haddr
& ~HPAGE_PMD_MASK
);
1643 VM_BUG_ON_VMA(vma
->vm_start
> haddr
, vma
);
1644 VM_BUG_ON_VMA(vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
, vma
);
1645 VM_BUG_ON(!pmd_trans_huge(*pmd
) && !pmd_devmap(*pmd
));
1647 count_vm_event(THP_SPLIT_PMD
);
1649 if (!vma_is_anonymous(vma
)) {
1650 _pmd
= pmdp_huge_clear_flush_notify(vma
, haddr
, pmd
);
1652 * We are going to unmap this huge page. So
1653 * just go ahead and zap it
1655 if (arch_needs_pgtable_deposit())
1656 zap_deposited_table(mm
, pmd
);
1657 if (vma_is_dax(vma
))
1659 page
= pmd_page(_pmd
);
1660 if (!PageReferenced(page
) && pmd_young(_pmd
))
1661 SetPageReferenced(page
);
1662 page_remove_rmap(page
, true);
1664 add_mm_counter(mm
, MM_FILEPAGES
, -HPAGE_PMD_NR
);
1666 } else if (is_huge_zero_pmd(*pmd
)) {
1667 return __split_huge_zero_page_pmd(vma
, haddr
, pmd
);
1670 page
= pmd_page(*pmd
);
1671 VM_BUG_ON_PAGE(!page_count(page
), page
);
1672 page_ref_add(page
, HPAGE_PMD_NR
- 1);
1673 write
= pmd_write(*pmd
);
1674 young
= pmd_young(*pmd
);
1675 dirty
= pmd_dirty(*pmd
);
1676 soft_dirty
= pmd_soft_dirty(*pmd
);
1678 pmdp_huge_split_prepare(vma
, haddr
, pmd
);
1679 pgtable
= pgtable_trans_huge_withdraw(mm
, pmd
);
1680 pmd_populate(mm
, &_pmd
, pgtable
);
1682 for (i
= 0, addr
= haddr
; i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
) {
1685 * Note that NUMA hinting access restrictions are not
1686 * transferred to avoid any possibility of altering
1687 * permissions across VMAs.
1690 swp_entry_t swp_entry
;
1691 swp_entry
= make_migration_entry(page
+ i
, write
);
1692 entry
= swp_entry_to_pte(swp_entry
);
1694 entry
= pte_swp_mksoft_dirty(entry
);
1696 entry
= mk_pte(page
+ i
, READ_ONCE(vma
->vm_page_prot
));
1697 entry
= maybe_mkwrite(entry
, vma
);
1699 entry
= pte_wrprotect(entry
);
1701 entry
= pte_mkold(entry
);
1703 entry
= pte_mksoft_dirty(entry
);
1706 SetPageDirty(page
+ i
);
1707 pte
= pte_offset_map(&_pmd
, addr
);
1708 BUG_ON(!pte_none(*pte
));
1709 set_pte_at(mm
, addr
, pte
, entry
);
1710 atomic_inc(&page
[i
]._mapcount
);
1715 * Set PG_double_map before dropping compound_mapcount to avoid
1716 * false-negative page_mapped().
1718 if (compound_mapcount(page
) > 1 && !TestSetPageDoubleMap(page
)) {
1719 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
1720 atomic_inc(&page
[i
]._mapcount
);
1723 if (atomic_add_negative(-1, compound_mapcount_ptr(page
))) {
1724 /* Last compound_mapcount is gone. */
1725 __dec_node_page_state(page
, NR_ANON_THPS
);
1726 if (TestClearPageDoubleMap(page
)) {
1727 /* No need in mapcount reference anymore */
1728 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
1729 atomic_dec(&page
[i
]._mapcount
);
1733 smp_wmb(); /* make pte visible before pmd */
1735 * Up to this point the pmd is present and huge and userland has the
1736 * whole access to the hugepage during the split (which happens in
1737 * place). If we overwrite the pmd with the not-huge version pointing
1738 * to the pte here (which of course we could if all CPUs were bug
1739 * free), userland could trigger a small page size TLB miss on the
1740 * small sized TLB while the hugepage TLB entry is still established in
1741 * the huge TLB. Some CPU doesn't like that.
1742 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
1743 * 383 on page 93. Intel should be safe but is also warns that it's
1744 * only safe if the permission and cache attributes of the two entries
1745 * loaded in the two TLB is identical (which should be the case here).
1746 * But it is generally safer to never allow small and huge TLB entries
1747 * for the same virtual address to be loaded simultaneously. So instead
1748 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
1749 * current pmd notpresent (atomically because here the pmd_trans_huge
1750 * and pmd_trans_splitting must remain set at all times on the pmd
1751 * until the split is complete for this pmd), then we flush the SMP TLB
1752 * and finally we write the non-huge version of the pmd entry with
1755 pmdp_invalidate(vma
, haddr
, pmd
);
1756 pmd_populate(mm
, pmd
, pgtable
);
1759 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1760 page_remove_rmap(page
+ i
, false);
1766 void __split_huge_pmd(struct vm_area_struct
*vma
, pmd_t
*pmd
,
1767 unsigned long address
, bool freeze
, struct page
*page
)
1770 struct mm_struct
*mm
= vma
->vm_mm
;
1771 unsigned long haddr
= address
& HPAGE_PMD_MASK
;
1773 mmu_notifier_invalidate_range_start(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
1774 ptl
= pmd_lock(mm
, pmd
);
1777 * If caller asks to setup a migration entries, we need a page to check
1778 * pmd against. Otherwise we can end up replacing wrong page.
1780 VM_BUG_ON(freeze
&& !page
);
1781 if (page
&& page
!= pmd_page(*pmd
))
1784 if (pmd_trans_huge(*pmd
)) {
1785 page
= pmd_page(*pmd
);
1786 if (PageMlocked(page
))
1787 clear_page_mlock(page
);
1788 } else if (!pmd_devmap(*pmd
))
1790 __split_huge_pmd_locked(vma
, pmd
, haddr
, freeze
);
1793 mmu_notifier_invalidate_range_end(mm
, haddr
, haddr
+ HPAGE_PMD_SIZE
);
1796 void split_huge_pmd_address(struct vm_area_struct
*vma
, unsigned long address
,
1797 bool freeze
, struct page
*page
)
1803 pgd
= pgd_offset(vma
->vm_mm
, address
);
1804 if (!pgd_present(*pgd
))
1807 pud
= pud_offset(pgd
, address
);
1808 if (!pud_present(*pud
))
1811 pmd
= pmd_offset(pud
, address
);
1813 __split_huge_pmd(vma
, pmd
, address
, freeze
, page
);
1816 void vma_adjust_trans_huge(struct vm_area_struct
*vma
,
1817 unsigned long start
,
1822 * If the new start address isn't hpage aligned and it could
1823 * previously contain an hugepage: check if we need to split
1826 if (start
& ~HPAGE_PMD_MASK
&&
1827 (start
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
1828 (start
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
1829 split_huge_pmd_address(vma
, start
, false, NULL
);
1832 * If the new end address isn't hpage aligned and it could
1833 * previously contain an hugepage: check if we need to split
1836 if (end
& ~HPAGE_PMD_MASK
&&
1837 (end
& HPAGE_PMD_MASK
) >= vma
->vm_start
&&
1838 (end
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= vma
->vm_end
)
1839 split_huge_pmd_address(vma
, end
, false, NULL
);
1842 * If we're also updating the vma->vm_next->vm_start, if the new
1843 * vm_next->vm_start isn't page aligned and it could previously
1844 * contain an hugepage: check if we need to split an huge pmd.
1846 if (adjust_next
> 0) {
1847 struct vm_area_struct
*next
= vma
->vm_next
;
1848 unsigned long nstart
= next
->vm_start
;
1849 nstart
+= adjust_next
<< PAGE_SHIFT
;
1850 if (nstart
& ~HPAGE_PMD_MASK
&&
1851 (nstart
& HPAGE_PMD_MASK
) >= next
->vm_start
&&
1852 (nstart
& HPAGE_PMD_MASK
) + HPAGE_PMD_SIZE
<= next
->vm_end
)
1853 split_huge_pmd_address(next
, nstart
, false, NULL
);
1857 static void freeze_page(struct page
*page
)
1859 enum ttu_flags ttu_flags
= TTU_IGNORE_MLOCK
| TTU_IGNORE_ACCESS
|
1863 VM_BUG_ON_PAGE(!PageHead(page
), page
);
1866 ttu_flags
|= TTU_MIGRATION
;
1868 /* We only need TTU_SPLIT_HUGE_PMD once */
1869 ret
= try_to_unmap(page
, ttu_flags
| TTU_SPLIT_HUGE_PMD
);
1870 for (i
= 1; !ret
&& i
< HPAGE_PMD_NR
; i
++) {
1871 /* Cut short if the page is unmapped */
1872 if (page_count(page
) == 1)
1875 ret
= try_to_unmap(page
+ i
, ttu_flags
);
1877 VM_BUG_ON_PAGE(ret
, page
+ i
- 1);
1880 static void unfreeze_page(struct page
*page
)
1884 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
1885 remove_migration_ptes(page
+ i
, page
+ i
, true);
1888 static void __split_huge_page_tail(struct page
*head
, int tail
,
1889 struct lruvec
*lruvec
, struct list_head
*list
)
1891 struct page
*page_tail
= head
+ tail
;
1893 VM_BUG_ON_PAGE(atomic_read(&page_tail
->_mapcount
) != -1, page_tail
);
1894 VM_BUG_ON_PAGE(page_ref_count(page_tail
) != 0, page_tail
);
1897 * tail_page->_refcount is zero and not changing from under us. But
1898 * get_page_unless_zero() may be running from under us on the
1899 * tail_page. If we used atomic_set() below instead of atomic_inc() or
1900 * atomic_add(), we would then run atomic_set() concurrently with
1901 * get_page_unless_zero(), and atomic_set() is implemented in C not
1902 * using locked ops. spin_unlock on x86 sometime uses locked ops
1903 * because of PPro errata 66, 92, so unless somebody can guarantee
1904 * atomic_set() here would be safe on all archs (and not only on x86),
1905 * it's safer to use atomic_inc()/atomic_add().
1907 if (PageAnon(head
)) {
1908 page_ref_inc(page_tail
);
1910 /* Additional pin to radix tree */
1911 page_ref_add(page_tail
, 2);
1914 page_tail
->flags
&= ~PAGE_FLAGS_CHECK_AT_PREP
;
1915 page_tail
->flags
|= (head
->flags
&
1916 ((1L << PG_referenced
) |
1917 (1L << PG_swapbacked
) |
1918 (1L << PG_mlocked
) |
1919 (1L << PG_uptodate
) |
1922 (1L << PG_unevictable
) |
1926 * After clearing PageTail the gup refcount can be released.
1927 * Page flags also must be visible before we make the page non-compound.
1931 clear_compound_head(page_tail
);
1933 if (page_is_young(head
))
1934 set_page_young(page_tail
);
1935 if (page_is_idle(head
))
1936 set_page_idle(page_tail
);
1938 /* ->mapping in first tail page is compound_mapcount */
1939 VM_BUG_ON_PAGE(tail
> 2 && page_tail
->mapping
!= TAIL_MAPPING
,
1941 page_tail
->mapping
= head
->mapping
;
1943 page_tail
->index
= head
->index
+ tail
;
1944 page_cpupid_xchg_last(page_tail
, page_cpupid_last(head
));
1945 lru_add_page_tail(head
, page_tail
, lruvec
, list
);
1948 static void __split_huge_page(struct page
*page
, struct list_head
*list
,
1949 unsigned long flags
)
1951 struct page
*head
= compound_head(page
);
1952 struct zone
*zone
= page_zone(head
);
1953 struct lruvec
*lruvec
;
1957 lruvec
= mem_cgroup_page_lruvec(head
, zone
->zone_pgdat
);
1959 /* complete memcg works before add pages to LRU */
1960 mem_cgroup_split_huge_fixup(head
);
1962 if (!PageAnon(page
))
1963 end
= DIV_ROUND_UP(i_size_read(head
->mapping
->host
), PAGE_SIZE
);
1965 for (i
= HPAGE_PMD_NR
- 1; i
>= 1; i
--) {
1966 __split_huge_page_tail(head
, i
, lruvec
, list
);
1967 /* Some pages can be beyond i_size: drop them from page cache */
1968 if (head
[i
].index
>= end
) {
1969 __ClearPageDirty(head
+ i
);
1970 __delete_from_page_cache(head
+ i
, NULL
);
1971 if (IS_ENABLED(CONFIG_SHMEM
) && PageSwapBacked(head
))
1972 shmem_uncharge(head
->mapping
->host
, 1);
1977 ClearPageCompound(head
);
1978 /* See comment in __split_huge_page_tail() */
1979 if (PageAnon(head
)) {
1982 /* Additional pin to radix tree */
1983 page_ref_add(head
, 2);
1984 spin_unlock(&head
->mapping
->tree_lock
);
1987 spin_unlock_irqrestore(zone_lru_lock(page_zone(head
)), flags
);
1989 unfreeze_page(head
);
1991 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
1992 struct page
*subpage
= head
+ i
;
1993 if (subpage
== page
)
1995 unlock_page(subpage
);
1998 * Subpages may be freed if there wasn't any mapping
1999 * like if add_to_swap() is running on a lru page that
2000 * had its mapping zapped. And freeing these pages
2001 * requires taking the lru_lock so we do the put_page
2002 * of the tail pages after the split is complete.
2008 int total_mapcount(struct page
*page
)
2010 int i
, compound
, ret
;
2012 VM_BUG_ON_PAGE(PageTail(page
), page
);
2014 if (likely(!PageCompound(page
)))
2015 return atomic_read(&page
->_mapcount
) + 1;
2017 compound
= compound_mapcount(page
);
2021 for (i
= 0; i
< HPAGE_PMD_NR
; i
++)
2022 ret
+= atomic_read(&page
[i
]._mapcount
) + 1;
2023 /* File pages has compound_mapcount included in _mapcount */
2024 if (!PageAnon(page
))
2025 return ret
- compound
* HPAGE_PMD_NR
;
2026 if (PageDoubleMap(page
))
2027 ret
-= HPAGE_PMD_NR
;
2032 * This calculates accurately how many mappings a transparent hugepage
2033 * has (unlike page_mapcount() which isn't fully accurate). This full
2034 * accuracy is primarily needed to know if copy-on-write faults can
2035 * reuse the page and change the mapping to read-write instead of
2036 * copying them. At the same time this returns the total_mapcount too.
2038 * The function returns the highest mapcount any one of the subpages
2039 * has. If the return value is one, even if different processes are
2040 * mapping different subpages of the transparent hugepage, they can
2041 * all reuse it, because each process is reusing a different subpage.
2043 * The total_mapcount is instead counting all virtual mappings of the
2044 * subpages. If the total_mapcount is equal to "one", it tells the
2045 * caller all mappings belong to the same "mm" and in turn the
2046 * anon_vma of the transparent hugepage can become the vma->anon_vma
2047 * local one as no other process may be mapping any of the subpages.
2049 * It would be more accurate to replace page_mapcount() with
2050 * page_trans_huge_mapcount(), however we only use
2051 * page_trans_huge_mapcount() in the copy-on-write faults where we
2052 * need full accuracy to avoid breaking page pinning, because
2053 * page_trans_huge_mapcount() is slower than page_mapcount().
2055 int page_trans_huge_mapcount(struct page
*page
, int *total_mapcount
)
2057 int i
, ret
, _total_mapcount
, mapcount
;
2059 /* hugetlbfs shouldn't call it */
2060 VM_BUG_ON_PAGE(PageHuge(page
), page
);
2062 if (likely(!PageTransCompound(page
))) {
2063 mapcount
= atomic_read(&page
->_mapcount
) + 1;
2065 *total_mapcount
= mapcount
;
2069 page
= compound_head(page
);
2071 _total_mapcount
= ret
= 0;
2072 for (i
= 0; i
< HPAGE_PMD_NR
; i
++) {
2073 mapcount
= atomic_read(&page
[i
]._mapcount
) + 1;
2074 ret
= max(ret
, mapcount
);
2075 _total_mapcount
+= mapcount
;
2077 if (PageDoubleMap(page
)) {
2079 _total_mapcount
-= HPAGE_PMD_NR
;
2081 mapcount
= compound_mapcount(page
);
2083 _total_mapcount
+= mapcount
;
2085 *total_mapcount
= _total_mapcount
;
2090 * This function splits huge page into normal pages. @page can point to any
2091 * subpage of huge page to split. Split doesn't change the position of @page.
2093 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2094 * The huge page must be locked.
2096 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2098 * Both head page and tail pages will inherit mapping, flags, and so on from
2101 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2102 * they are not mapped.
2104 * Returns 0 if the hugepage is split successfully.
2105 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2108 int split_huge_page_to_list(struct page
*page
, struct list_head
*list
)
2110 struct page
*head
= compound_head(page
);
2111 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(head
));
2112 struct anon_vma
*anon_vma
= NULL
;
2113 struct address_space
*mapping
= NULL
;
2114 int count
, mapcount
, extra_pins
, ret
;
2116 unsigned long flags
;
2118 VM_BUG_ON_PAGE(is_huge_zero_page(page
), page
);
2119 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
2120 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
2121 VM_BUG_ON_PAGE(!PageCompound(page
), page
);
2123 if (PageAnon(head
)) {
2125 * The caller does not necessarily hold an mmap_sem that would
2126 * prevent the anon_vma disappearing so we first we take a
2127 * reference to it and then lock the anon_vma for write. This
2128 * is similar to page_lock_anon_vma_read except the write lock
2129 * is taken to serialise against parallel split or collapse
2132 anon_vma
= page_get_anon_vma(head
);
2139 anon_vma_lock_write(anon_vma
);
2141 mapping
= head
->mapping
;
2149 /* Addidional pins from radix tree */
2150 extra_pins
= HPAGE_PMD_NR
;
2152 i_mmap_lock_read(mapping
);
2156 * Racy check if we can split the page, before freeze_page() will
2159 if (total_mapcount(head
) != page_count(head
) - extra_pins
- 1) {
2164 mlocked
= PageMlocked(page
);
2166 VM_BUG_ON_PAGE(compound_mapcount(head
), head
);
2168 /* Make sure the page is not on per-CPU pagevec as it takes pin */
2172 /* prevent PageLRU to go away from under us, and freeze lru stats */
2173 spin_lock_irqsave(zone_lru_lock(page_zone(head
)), flags
);
2178 spin_lock(&mapping
->tree_lock
);
2179 pslot
= radix_tree_lookup_slot(&mapping
->page_tree
,
2182 * Check if the head page is present in radix tree.
2183 * We assume all tail are present too, if head is there.
2185 if (radix_tree_deref_slot_protected(pslot
,
2186 &mapping
->tree_lock
) != head
)
2190 /* Prevent deferred_split_scan() touching ->_refcount */
2191 spin_lock(&pgdata
->split_queue_lock
);
2192 count
= page_count(head
);
2193 mapcount
= total_mapcount(head
);
2194 if (!mapcount
&& page_ref_freeze(head
, 1 + extra_pins
)) {
2195 if (!list_empty(page_deferred_list(head
))) {
2196 pgdata
->split_queue_len
--;
2197 list_del(page_deferred_list(head
));
2200 __dec_node_page_state(page
, NR_SHMEM_THPS
);
2201 spin_unlock(&pgdata
->split_queue_lock
);
2202 __split_huge_page(page
, list
, flags
);
2205 if (IS_ENABLED(CONFIG_DEBUG_VM
) && mapcount
) {
2206 pr_alert("total_mapcount: %u, page_count(): %u\n",
2209 dump_page(head
, NULL
);
2210 dump_page(page
, "total_mapcount(head) > 0");
2213 spin_unlock(&pgdata
->split_queue_lock
);
2215 spin_unlock(&mapping
->tree_lock
);
2216 spin_unlock_irqrestore(zone_lru_lock(page_zone(head
)), flags
);
2217 unfreeze_page(head
);
2223 anon_vma_unlock_write(anon_vma
);
2224 put_anon_vma(anon_vma
);
2227 i_mmap_unlock_read(mapping
);
2229 count_vm_event(!ret
? THP_SPLIT_PAGE
: THP_SPLIT_PAGE_FAILED
);
2233 void free_transhuge_page(struct page
*page
)
2235 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
2236 unsigned long flags
;
2238 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
2239 if (!list_empty(page_deferred_list(page
))) {
2240 pgdata
->split_queue_len
--;
2241 list_del(page_deferred_list(page
));
2243 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
2244 free_compound_page(page
);
2247 void deferred_split_huge_page(struct page
*page
)
2249 struct pglist_data
*pgdata
= NODE_DATA(page_to_nid(page
));
2250 unsigned long flags
;
2252 VM_BUG_ON_PAGE(!PageTransHuge(page
), page
);
2254 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
2255 if (list_empty(page_deferred_list(page
))) {
2256 count_vm_event(THP_DEFERRED_SPLIT_PAGE
);
2257 list_add_tail(page_deferred_list(page
), &pgdata
->split_queue
);
2258 pgdata
->split_queue_len
++;
2260 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
2263 static unsigned long deferred_split_count(struct shrinker
*shrink
,
2264 struct shrink_control
*sc
)
2266 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
2267 return ACCESS_ONCE(pgdata
->split_queue_len
);
2270 static unsigned long deferred_split_scan(struct shrinker
*shrink
,
2271 struct shrink_control
*sc
)
2273 struct pglist_data
*pgdata
= NODE_DATA(sc
->nid
);
2274 unsigned long flags
;
2275 LIST_HEAD(list
), *pos
, *next
;
2279 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
2280 /* Take pin on all head pages to avoid freeing them under us */
2281 list_for_each_safe(pos
, next
, &pgdata
->split_queue
) {
2282 page
= list_entry((void *)pos
, struct page
, mapping
);
2283 page
= compound_head(page
);
2284 if (get_page_unless_zero(page
)) {
2285 list_move(page_deferred_list(page
), &list
);
2287 /* We lost race with put_compound_page() */
2288 list_del_init(page_deferred_list(page
));
2289 pgdata
->split_queue_len
--;
2291 if (!--sc
->nr_to_scan
)
2294 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
2296 list_for_each_safe(pos
, next
, &list
) {
2297 page
= list_entry((void *)pos
, struct page
, mapping
);
2299 /* split_huge_page() removes page from list on success */
2300 if (!split_huge_page(page
))
2306 spin_lock_irqsave(&pgdata
->split_queue_lock
, flags
);
2307 list_splice_tail(&list
, &pgdata
->split_queue
);
2308 spin_unlock_irqrestore(&pgdata
->split_queue_lock
, flags
);
2311 * Stop shrinker if we didn't split any page, but the queue is empty.
2312 * This can happen if pages were freed under us.
2314 if (!split
&& list_empty(&pgdata
->split_queue
))
2319 static struct shrinker deferred_split_shrinker
= {
2320 .count_objects
= deferred_split_count
,
2321 .scan_objects
= deferred_split_scan
,
2322 .seeks
= DEFAULT_SEEKS
,
2323 .flags
= SHRINKER_NUMA_AWARE
,
2326 #ifdef CONFIG_DEBUG_FS
2327 static int split_huge_pages_set(void *data
, u64 val
)
2331 unsigned long pfn
, max_zone_pfn
;
2332 unsigned long total
= 0, split
= 0;
2337 for_each_populated_zone(zone
) {
2338 max_zone_pfn
= zone_end_pfn(zone
);
2339 for (pfn
= zone
->zone_start_pfn
; pfn
< max_zone_pfn
; pfn
++) {
2340 if (!pfn_valid(pfn
))
2343 page
= pfn_to_page(pfn
);
2344 if (!get_page_unless_zero(page
))
2347 if (zone
!= page_zone(page
))
2350 if (!PageHead(page
) || PageHuge(page
) || !PageLRU(page
))
2355 if (!split_huge_page(page
))
2363 pr_info("%lu of %lu THP split\n", split
, total
);
2367 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops
, NULL
, split_huge_pages_set
,
2370 static int __init
split_huge_pages_debugfs(void)
2374 ret
= debugfs_create_file("split_huge_pages", 0200, NULL
, NULL
,
2375 &split_huge_pages_fops
);
2377 pr_warn("Failed to create split_huge_pages in debugfs");
2380 late_initcall(split_huge_pages_debugfs
);