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,
641 VM_BUG_ON(!PageCompound(page));
642 pgtable = pte_alloc_one(mm, haddr);
643 if (unlikely(!pgtable)) {
644 mem_cgroup_uncharge_page(page);
649 clear_huge_page(page, haddr, HPAGE_PMD_NR);
650 __SetPageUptodate(page);
652 spin_lock(&mm->page_table_lock);
653 if (unlikely(!pmd_none(*pmd))) {
654 spin_unlock(&mm->page_table_lock);
655 mem_cgroup_uncharge_page(page);
657 pte_free(mm, pgtable);
660 entry = mk_pmd(page, vma->vm_page_prot);
661 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
662 entry = pmd_mkhuge(entry);
664 * The spinlocking to take the lru_lock inside
665 * page_add_new_anon_rmap() acts as a full memory
666 * barrier to be sure clear_huge_page writes become
667 * visible after the set_pmd_at() write.
669 page_add_new_anon_rmap(page, vma, haddr);
670 set_pmd_at(mm, haddr, pmd, entry);
671 prepare_pmd_huge_pte(pgtable, mm);
672 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);
796 spin_unlock(&src_mm->page_table_lock);
797 spin_unlock(&dst_mm->page_table_lock);
802 /* no "address" argument so destroys page coloring of some arch */
803 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
807 assert_spin_locked(&mm->page_table_lock);
810 pgtable = mm->pmd_huge_pte;
811 if (list_empty(&pgtable->lru))
812 mm->pmd_huge_pte = NULL;
814 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
816 list_del(&pgtable->lru);
821 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
822 struct vm_area_struct *vma,
823 unsigned long address,
824 pmd_t *pmd, pmd_t orig_pmd,
833 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
835 if (unlikely(!pages)) {
840 for (i = 0; i < HPAGE_PMD_NR; i++) {
841 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
843 vma, address, page_to_nid(page));
844 if (unlikely(!pages[i] ||
845 mem_cgroup_newpage_charge(pages[i], mm,
849 mem_cgroup_uncharge_start();
851 mem_cgroup_uncharge_page(pages[i]);
854 mem_cgroup_uncharge_end();
861 for (i = 0; i < HPAGE_PMD_NR; i++) {
862 copy_user_highpage(pages[i], page + i,
863 haddr + PAGE_SIZE * i, vma);
864 __SetPageUptodate(pages[i]);
868 spin_lock(&mm->page_table_lock);
869 if (unlikely(!pmd_same(*pmd, orig_pmd)))
871 VM_BUG_ON(!PageHead(page));
873 pmdp_clear_flush_notify(vma, haddr, pmd);
874 /* leave pmd empty until pte is filled */
876 pgtable = get_pmd_huge_pte(mm);
877 pmd_populate(mm, &_pmd, pgtable);
879 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
881 entry = mk_pte(pages[i], vma->vm_page_prot);
882 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
883 page_add_new_anon_rmap(pages[i], vma, haddr);
884 pte = pte_offset_map(&_pmd, haddr);
885 VM_BUG_ON(!pte_none(*pte));
886 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,
1029 pmd_t *pmd, unsigned long addr)
1033 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1036 pgtable = get_pmd_huge_pte(tlb->mm);
1037 page = pmd_page(*pmd);
1039 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1040 page_remove_rmap(page);
1041 VM_BUG_ON(page_mapcount(page) < 0);
1042 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1043 VM_BUG_ON(!PageHead(page));
1045 spin_unlock(&tlb->mm->page_table_lock);
1046 tlb_remove_page(tlb, page);
1047 pte_free(tlb->mm, pgtable);
1053 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1054 unsigned long addr, unsigned long end,
1059 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1061 * All logical pages in the range are present
1062 * if backed by a huge page.
1064 spin_unlock(&vma->vm_mm->page_table_lock);
1065 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1072 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1073 unsigned long old_addr,
1074 unsigned long new_addr, unsigned long old_end,
1075 pmd_t *old_pmd, pmd_t *new_pmd)
1080 struct mm_struct *mm = vma->vm_mm;
1082 if ((old_addr & ~HPAGE_PMD_MASK) ||
1083 (new_addr & ~HPAGE_PMD_MASK) ||
1084 old_end - old_addr < HPAGE_PMD_SIZE ||
1085 (new_vma->vm_flags & VM_NOHUGEPAGE))
1089 * The destination pmd shouldn't be established, free_pgtables()
1090 * should have release it.
1092 if (WARN_ON(!pmd_none(*new_pmd))) {
1093 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1097 ret = __pmd_trans_huge_lock(old_pmd, vma);
1099 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1100 VM_BUG_ON(!pmd_none(*new_pmd));
1101 set_pmd_at(mm, new_addr, new_pmd, pmd);
1102 spin_unlock(&mm->page_table_lock);
1108 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1109 unsigned long addr, pgprot_t newprot)
1111 struct mm_struct *mm = vma->vm_mm;
1114 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1116 entry = pmdp_get_and_clear(mm, addr, pmd);
1117 entry = pmd_modify(entry, newprot);
1118 set_pmd_at(mm, addr, pmd, entry);
1119 spin_unlock(&vma->vm_mm->page_table_lock);
1127 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1128 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1130 * Note that if it returns 1, this routine returns without unlocking page
1131 * table locks. So callers must unlock them.
1133 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1135 spin_lock(&vma->vm_mm->page_table_lock);
1136 if (likely(pmd_trans_huge(*pmd))) {
1137 if (unlikely(pmd_trans_splitting(*pmd))) {
1138 spin_unlock(&vma->vm_mm->page_table_lock);
1139 wait_split_huge_page(vma->anon_vma, pmd);
1142 /* Thp mapped by 'pmd' is stable, so we can
1143 * handle it as it is. */
1147 spin_unlock(&vma->vm_mm->page_table_lock);
1151 pmd_t *page_check_address_pmd(struct page *page,
1152 struct mm_struct *mm,
1153 unsigned long address,
1154 enum page_check_address_pmd_flag flag)
1158 pmd_t *pmd, *ret = NULL;
1160 if (address & ~HPAGE_PMD_MASK)
1163 pgd = pgd_offset(mm, address);
1164 if (!pgd_present(*pgd))
1167 pud = pud_offset(pgd, address);
1168 if (!pud_present(*pud))
1171 pmd = pmd_offset(pud, address);
1174 if (pmd_page(*pmd) != page)
1177 * split_vma() may create temporary aliased mappings. There is
1178 * no risk as long as all huge pmd are found and have their
1179 * splitting bit set before __split_huge_page_refcount
1180 * runs. Finding the same huge pmd more than once during the
1181 * same rmap walk is not a problem.
1183 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1184 pmd_trans_splitting(*pmd))
1186 if (pmd_trans_huge(*pmd)) {
1187 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1188 !pmd_trans_splitting(*pmd));
1195 static int __split_huge_page_splitting(struct page *page,
1196 struct vm_area_struct *vma,
1197 unsigned long address)
1199 struct mm_struct *mm = vma->vm_mm;
1203 spin_lock(&mm->page_table_lock);
1204 pmd = page_check_address_pmd(page, mm, address,
1205 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1208 * We can't temporarily set the pmd to null in order
1209 * to split it, the pmd must remain marked huge at all
1210 * times or the VM won't take the pmd_trans_huge paths
1211 * and it won't wait on the anon_vma->root->mutex to
1212 * serialize against split_huge_page*.
1214 pmdp_splitting_flush_notify(vma, address, pmd);
1217 spin_unlock(&mm->page_table_lock);
1222 static void __split_huge_page_refcount(struct page *page)
1225 struct zone *zone = page_zone(page);
1228 /* prevent PageLRU to go away from under us, and freeze lru stats */
1229 spin_lock_irq(&zone->lru_lock);
1230 compound_lock(page);
1231 /* complete memcg works before add pages to LRU */
1232 mem_cgroup_split_huge_fixup(page);
1234 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1235 struct page *page_tail = page + i;
1237 /* tail_page->_mapcount cannot change */
1238 BUG_ON(page_mapcount(page_tail) < 0);
1239 tail_count += page_mapcount(page_tail);
1240 /* check for overflow */
1241 BUG_ON(tail_count < 0);
1242 BUG_ON(atomic_read(&page_tail->_count) != 0);
1244 * tail_page->_count is zero and not changing from
1245 * under us. But get_page_unless_zero() may be running
1246 * from under us on the tail_page. If we used
1247 * atomic_set() below instead of atomic_add(), we
1248 * would then run atomic_set() concurrently with
1249 * get_page_unless_zero(), and atomic_set() is
1250 * implemented in C not using locked ops. spin_unlock
1251 * on x86 sometime uses locked ops because of PPro
1252 * errata 66, 92, so unless somebody can guarantee
1253 * atomic_set() here would be safe on all archs (and
1254 * not only on x86), it's safer to use atomic_add().
1256 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1257 &page_tail->_count);
1259 /* after clearing PageTail the gup refcount can be released */
1263 * retain hwpoison flag of the poisoned tail page:
1264 * fix for the unsuitable process killed on Guest Machine(KVM)
1265 * by the memory-failure.
1267 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1268 page_tail->flags |= (page->flags &
1269 ((1L << PG_referenced) |
1270 (1L << PG_swapbacked) |
1271 (1L << PG_mlocked) |
1272 (1L << PG_uptodate)));
1273 page_tail->flags |= (1L << PG_dirty);
1275 /* clear PageTail before overwriting first_page */
1279 * __split_huge_page_splitting() already set the
1280 * splitting bit in all pmd that could map this
1281 * hugepage, that will ensure no CPU can alter the
1282 * mapcount on the head page. The mapcount is only
1283 * accounted in the head page and it has to be
1284 * transferred to all tail pages in the below code. So
1285 * for this code to be safe, the split the mapcount
1286 * can't change. But that doesn't mean userland can't
1287 * keep changing and reading the page contents while
1288 * we transfer the mapcount, so the pmd splitting
1289 * status is achieved setting a reserved bit in the
1290 * pmd, not by clearing the present bit.
1292 page_tail->_mapcount = page->_mapcount;
1294 BUG_ON(page_tail->mapping);
1295 page_tail->mapping = page->mapping;
1297 page_tail->index = page->index + i;
1299 BUG_ON(!PageAnon(page_tail));
1300 BUG_ON(!PageUptodate(page_tail));
1301 BUG_ON(!PageDirty(page_tail));
1302 BUG_ON(!PageSwapBacked(page_tail));
1305 lru_add_page_tail(zone, page, page_tail);
1307 atomic_sub(tail_count, &page->_count);
1308 BUG_ON(atomic_read(&page->_count) <= 0);
1310 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1311 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1313 ClearPageCompound(page);
1314 compound_unlock(page);
1315 spin_unlock_irq(&zone->lru_lock);
1317 for (i = 1; i < HPAGE_PMD_NR; i++) {
1318 struct page *page_tail = page + i;
1319 BUG_ON(page_count(page_tail) <= 0);
1321 * Tail pages may be freed if there wasn't any mapping
1322 * like if add_to_swap() is running on a lru page that
1323 * had its mapping zapped. And freeing these pages
1324 * requires taking the lru_lock so we do the put_page
1325 * of the tail pages after the split is complete.
1327 put_page(page_tail);
1331 * Only the head page (now become a regular page) is required
1332 * to be pinned by the caller.
1334 BUG_ON(page_count(page) <= 0);
1337 static int __split_huge_page_map(struct page *page,
1338 struct vm_area_struct *vma,
1339 unsigned long address)
1341 struct mm_struct *mm = vma->vm_mm;
1345 unsigned long haddr;
1347 spin_lock(&mm->page_table_lock);
1348 pmd = page_check_address_pmd(page, mm, address,
1349 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1351 pgtable = get_pmd_huge_pte(mm);
1352 pmd_populate(mm, &_pmd, pgtable);
1354 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1355 i++, haddr += PAGE_SIZE) {
1357 BUG_ON(PageCompound(page+i));
1358 entry = mk_pte(page + i, vma->vm_page_prot);
1359 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1360 if (!pmd_write(*pmd))
1361 entry = pte_wrprotect(entry);
1363 BUG_ON(page_mapcount(page) != 1);
1364 if (!pmd_young(*pmd))
1365 entry = pte_mkold(entry);
1366 pte = pte_offset_map(&_pmd, haddr);
1367 BUG_ON(!pte_none(*pte));
1368 set_pte_at(mm, haddr, pte, entry);
1372 smp_wmb(); /* make pte visible before pmd */
1374 * Up to this point the pmd is present and huge and
1375 * userland has the whole access to the hugepage
1376 * during the split (which happens in place). If we
1377 * overwrite the pmd with the not-huge version
1378 * pointing to the pte here (which of course we could
1379 * if all CPUs were bug free), userland could trigger
1380 * a small page size TLB miss on the small sized TLB
1381 * while the hugepage TLB entry is still established
1382 * in the huge TLB. Some CPU doesn't like that. See
1383 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1384 * Erratum 383 on page 93. Intel should be safe but is
1385 * also warns that it's only safe if the permission
1386 * and cache attributes of the two entries loaded in
1387 * the two TLB is identical (which should be the case
1388 * here). But it is generally safer to never allow
1389 * small and huge TLB entries for the same virtual
1390 * address to be loaded simultaneously. So instead of
1391 * doing "pmd_populate(); flush_tlb_range();" we first
1392 * mark the current pmd notpresent (atomically because
1393 * here the pmd_trans_huge and pmd_trans_splitting
1394 * must remain set at all times on the pmd until the
1395 * split is complete for this pmd), then we flush the
1396 * SMP TLB and finally we write the non-huge version
1397 * of the pmd entry with pmd_populate.
1399 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1400 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1401 pmd_populate(mm, pmd, pgtable);
1404 spin_unlock(&mm->page_table_lock);
1409 /* must be called with anon_vma->root->mutex hold */
1410 static void __split_huge_page(struct page *page,
1411 struct anon_vma *anon_vma)
1413 int mapcount, mapcount2;
1414 struct anon_vma_chain *avc;
1416 BUG_ON(!PageHead(page));
1417 BUG_ON(PageTail(page));
1420 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1421 struct vm_area_struct *vma = avc->vma;
1422 unsigned long addr = vma_address(page, vma);
1423 BUG_ON(is_vma_temporary_stack(vma));
1424 if (addr == -EFAULT)
1426 mapcount += __split_huge_page_splitting(page, vma, addr);
1429 * It is critical that new vmas are added to the tail of the
1430 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1431 * and establishes a child pmd before
1432 * __split_huge_page_splitting() freezes the parent pmd (so if
1433 * we fail to prevent copy_huge_pmd() from running until the
1434 * whole __split_huge_page() is complete), we will still see
1435 * the newly established pmd of the child later during the
1436 * walk, to be able to set it as pmd_trans_splitting too.
1438 if (mapcount != page_mapcount(page))
1439 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1440 mapcount, page_mapcount(page));
1441 BUG_ON(mapcount != page_mapcount(page));
1443 __split_huge_page_refcount(page);
1446 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1447 struct vm_area_struct *vma = avc->vma;
1448 unsigned long addr = vma_address(page, vma);
1449 BUG_ON(is_vma_temporary_stack(vma));
1450 if (addr == -EFAULT)
1452 mapcount2 += __split_huge_page_map(page, vma, addr);
1454 if (mapcount != mapcount2)
1455 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1456 mapcount, mapcount2, page_mapcount(page));
1457 BUG_ON(mapcount != mapcount2);
1460 int split_huge_page(struct page *page)
1462 struct anon_vma *anon_vma;
1465 BUG_ON(!PageAnon(page));
1466 anon_vma = page_lock_anon_vma(page);
1470 if (!PageCompound(page))
1473 BUG_ON(!PageSwapBacked(page));
1474 __split_huge_page(page, anon_vma);
1475 count_vm_event(THP_SPLIT);
1477 BUG_ON(PageCompound(page));
1479 page_unlock_anon_vma(anon_vma);
1484 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1485 VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1487 int hugepage_madvise(struct vm_area_struct *vma,
1488 unsigned long *vm_flags, int advice)
1493 * Be somewhat over-protective like KSM for now!
1495 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1497 *vm_flags &= ~VM_NOHUGEPAGE;
1498 *vm_flags |= VM_HUGEPAGE;
1500 * If the vma become good for khugepaged to scan,
1501 * register it here without waiting a page fault that
1502 * may not happen any time soon.
1504 if (unlikely(khugepaged_enter_vma_merge(vma)))
1507 case MADV_NOHUGEPAGE:
1509 * Be somewhat over-protective like KSM for now!
1511 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1513 *vm_flags &= ~VM_HUGEPAGE;
1514 *vm_flags |= VM_NOHUGEPAGE;
1516 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1517 * this vma even if we leave the mm registered in khugepaged if
1518 * it got registered before VM_NOHUGEPAGE was set.
1526 static int __init khugepaged_slab_init(void)
1528 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1529 sizeof(struct mm_slot),
1530 __alignof__(struct mm_slot), 0, NULL);
1537 static void __init khugepaged_slab_free(void)
1539 kmem_cache_destroy(mm_slot_cache);
1540 mm_slot_cache = NULL;
1543 static inline struct mm_slot *alloc_mm_slot(void)
1545 if (!mm_slot_cache) /* initialization failed */
1547 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1550 static inline void free_mm_slot(struct mm_slot *mm_slot)
1552 kmem_cache_free(mm_slot_cache, mm_slot);
1555 static int __init mm_slots_hash_init(void)
1557 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1565 static void __init mm_slots_hash_free(void)
1567 kfree(mm_slots_hash);
1568 mm_slots_hash = NULL;
1572 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1574 struct mm_slot *mm_slot;
1575 struct hlist_head *bucket;
1576 struct hlist_node *node;
1578 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1579 % MM_SLOTS_HASH_HEADS];
1580 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1581 if (mm == mm_slot->mm)
1587 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1588 struct mm_slot *mm_slot)
1590 struct hlist_head *bucket;
1592 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1593 % MM_SLOTS_HASH_HEADS];
1595 hlist_add_head(&mm_slot->hash, bucket);
1598 static inline int khugepaged_test_exit(struct mm_struct *mm)
1600 return atomic_read(&mm->mm_users) == 0;
1603 int __khugepaged_enter(struct mm_struct *mm)
1605 struct mm_slot *mm_slot;
1608 mm_slot = alloc_mm_slot();
1612 /* __khugepaged_exit() must not run from under us */
1613 VM_BUG_ON(khugepaged_test_exit(mm));
1614 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1615 free_mm_slot(mm_slot);
1619 spin_lock(&khugepaged_mm_lock);
1620 insert_to_mm_slots_hash(mm, mm_slot);
1622 * Insert just behind the scanning cursor, to let the area settle
1625 wakeup = list_empty(&khugepaged_scan.mm_head);
1626 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1627 spin_unlock(&khugepaged_mm_lock);
1629 atomic_inc(&mm->mm_count);
1631 wake_up_interruptible(&khugepaged_wait);
1636 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1638 unsigned long hstart, hend;
1641 * Not yet faulted in so we will register later in the
1642 * page fault if needed.
1646 /* khugepaged not yet working on file or special mappings */
1649 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1650 * true too, verify it here.
1652 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1653 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1654 hend = vma->vm_end & HPAGE_PMD_MASK;
1656 return khugepaged_enter(vma);
1660 void __khugepaged_exit(struct mm_struct *mm)
1662 struct mm_slot *mm_slot;
1665 spin_lock(&khugepaged_mm_lock);
1666 mm_slot = get_mm_slot(mm);
1667 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1668 hlist_del(&mm_slot->hash);
1669 list_del(&mm_slot->mm_node);
1672 spin_unlock(&khugepaged_mm_lock);
1675 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1676 free_mm_slot(mm_slot);
1678 } else if (mm_slot) {
1680 * This is required to serialize against
1681 * khugepaged_test_exit() (which is guaranteed to run
1682 * under mmap sem read mode). Stop here (after we
1683 * return all pagetables will be destroyed) until
1684 * khugepaged has finished working on the pagetables
1685 * under the mmap_sem.
1687 down_write(&mm->mmap_sem);
1688 up_write(&mm->mmap_sem);
1692 static void release_pte_page(struct page *page)
1694 /* 0 stands for page_is_file_cache(page) == false */
1695 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1697 putback_lru_page(page);
1700 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1702 while (--_pte >= pte) {
1703 pte_t pteval = *_pte;
1704 if (!pte_none(pteval))
1705 release_pte_page(pte_page(pteval));
1709 static void release_all_pte_pages(pte_t *pte)
1711 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1714 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1715 unsigned long address,
1720 int referenced = 0, isolated = 0, none = 0;
1721 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1722 _pte++, address += PAGE_SIZE) {
1723 pte_t pteval = *_pte;
1724 if (pte_none(pteval)) {
1725 if (++none <= khugepaged_max_ptes_none)
1728 release_pte_pages(pte, _pte);
1732 if (!pte_present(pteval) || !pte_write(pteval)) {
1733 release_pte_pages(pte, _pte);
1736 page = vm_normal_page(vma, address, pteval);
1737 if (unlikely(!page)) {
1738 release_pte_pages(pte, _pte);
1741 VM_BUG_ON(PageCompound(page));
1742 BUG_ON(!PageAnon(page));
1743 VM_BUG_ON(!PageSwapBacked(page));
1745 /* cannot use mapcount: can't collapse if there's a gup pin */
1746 if (page_count(page) != 1) {
1747 release_pte_pages(pte, _pte);
1751 * We can do it before isolate_lru_page because the
1752 * page can't be freed from under us. NOTE: PG_lock
1753 * is needed to serialize against split_huge_page
1754 * when invoked from the VM.
1756 if (!trylock_page(page)) {
1757 release_pte_pages(pte, _pte);
1761 * Isolate the page to avoid collapsing an hugepage
1762 * currently in use by the VM.
1764 if (isolate_lru_page(page)) {
1766 release_pte_pages(pte, _pte);
1769 /* 0 stands for page_is_file_cache(page) == false */
1770 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1771 VM_BUG_ON(!PageLocked(page));
1772 VM_BUG_ON(PageLRU(page));
1774 /* If there is no mapped pte young don't collapse the page */
1775 if (pte_young(pteval) || PageReferenced(page) ||
1776 mmu_notifier_test_young(vma->vm_mm, address))
1779 if (unlikely(!referenced))
1780 release_all_pte_pages(pte);
1787 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1788 struct vm_area_struct *vma,
1789 unsigned long address,
1793 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1794 pte_t pteval = *_pte;
1795 struct page *src_page;
1797 if (pte_none(pteval)) {
1798 clear_user_highpage(page, address);
1799 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1801 src_page = pte_page(pteval);
1802 copy_user_highpage(page, src_page, address, vma);
1803 VM_BUG_ON(page_mapcount(src_page) != 1);
1804 VM_BUG_ON(page_count(src_page) != 2);
1805 release_pte_page(src_page);
1807 * ptl mostly unnecessary, but preempt has to
1808 * be disabled to update the per-cpu stats
1809 * inside page_remove_rmap().
1813 * paravirt calls inside pte_clear here are
1816 pte_clear(vma->vm_mm, address, _pte);
1817 page_remove_rmap(src_page);
1819 free_page_and_swap_cache(src_page);
1822 address += PAGE_SIZE;
1827 static void collapse_huge_page(struct mm_struct *mm,
1828 unsigned long address,
1829 struct page **hpage,
1830 struct vm_area_struct *vma,
1838 struct page *new_page;
1841 unsigned long hstart, hend;
1843 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1845 up_read(&mm->mmap_sem);
1851 * Allocate the page while the vma is still valid and under
1852 * the mmap_sem read mode so there is no memory allocation
1853 * later when we take the mmap_sem in write mode. This is more
1854 * friendly behavior (OTOH it may actually hide bugs) to
1855 * filesystems in userland with daemons allocating memory in
1856 * the userland I/O paths. Allocating memory with the
1857 * mmap_sem in read mode is good idea also to allow greater
1860 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1861 node, __GFP_OTHER_NODE);
1864 * After allocating the hugepage, release the mmap_sem read lock in
1865 * preparation for taking it in write mode.
1867 up_read(&mm->mmap_sem);
1868 if (unlikely(!new_page)) {
1869 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1870 *hpage = ERR_PTR(-ENOMEM);
1875 count_vm_event(THP_COLLAPSE_ALLOC);
1876 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1884 * Prevent all access to pagetables with the exception of
1885 * gup_fast later hanlded by the ptep_clear_flush and the VM
1886 * handled by the anon_vma lock + PG_lock.
1888 down_write(&mm->mmap_sem);
1889 if (unlikely(khugepaged_test_exit(mm)))
1892 vma = find_vma(mm, address);
1893 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1894 hend = vma->vm_end & HPAGE_PMD_MASK;
1895 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1898 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1899 (vma->vm_flags & VM_NOHUGEPAGE))
1902 if (!vma->anon_vma || vma->vm_ops)
1904 if (is_vma_temporary_stack(vma))
1907 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1908 * true too, verify it here.
1910 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1912 pgd = pgd_offset(mm, address);
1913 if (!pgd_present(*pgd))
1916 pud = pud_offset(pgd, address);
1917 if (!pud_present(*pud))
1920 pmd = pmd_offset(pud, address);
1921 /* pmd can't go away or become huge under us */
1922 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1925 anon_vma_lock(vma->anon_vma);
1927 pte = pte_offset_map(pmd, address);
1928 ptl = pte_lockptr(mm, pmd);
1930 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1932 * After this gup_fast can't run anymore. This also removes
1933 * any huge TLB entry from the CPU so we won't allow
1934 * huge and small TLB entries for the same virtual address
1935 * to avoid the risk of CPU bugs in that area.
1937 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1938 spin_unlock(&mm->page_table_lock);
1941 isolated = __collapse_huge_page_isolate(vma, address, pte);
1944 if (unlikely(!isolated)) {
1946 spin_lock(&mm->page_table_lock);
1947 BUG_ON(!pmd_none(*pmd));
1948 set_pmd_at(mm, address, pmd, _pmd);
1949 spin_unlock(&mm->page_table_lock);
1950 anon_vma_unlock(vma->anon_vma);
1955 * All pages are isolated and locked so anon_vma rmap
1956 * can't run anymore.
1958 anon_vma_unlock(vma->anon_vma);
1960 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1962 __SetPageUptodate(new_page);
1963 pgtable = pmd_pgtable(_pmd);
1964 VM_BUG_ON(page_count(pgtable) != 1);
1965 VM_BUG_ON(page_mapcount(pgtable) != 0);
1967 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1968 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1969 _pmd = pmd_mkhuge(_pmd);
1972 * spin_lock() below is not the equivalent of smp_wmb(), so
1973 * this is needed to avoid the copy_huge_page writes to become
1974 * visible after the set_pmd_at() write.
1978 spin_lock(&mm->page_table_lock);
1979 BUG_ON(!pmd_none(*pmd));
1980 page_add_new_anon_rmap(new_page, vma, address);
1981 set_pmd_at(mm, address, pmd, _pmd);
1982 update_mmu_cache(vma, address, _pmd);
1983 prepare_pmd_huge_pte(pgtable, mm);
1984 spin_unlock(&mm->page_table_lock);
1989 khugepaged_pages_collapsed++;
1991 up_write(&mm->mmap_sem);
1995 mem_cgroup_uncharge_page(new_page);
2002 static int khugepaged_scan_pmd(struct mm_struct *mm,
2003 struct vm_area_struct *vma,
2004 unsigned long address,
2005 struct page **hpage)
2011 int ret = 0, referenced = 0, none = 0;
2013 unsigned long _address;
2017 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2019 pgd = pgd_offset(mm, address);
2020 if (!pgd_present(*pgd))
2023 pud = pud_offset(pgd, address);
2024 if (!pud_present(*pud))
2027 pmd = pmd_offset(pud, address);
2028 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
2031 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2032 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2033 _pte++, _address += PAGE_SIZE) {
2034 pte_t pteval = *_pte;
2035 if (pte_none(pteval)) {
2036 if (++none <= khugepaged_max_ptes_none)
2041 if (!pte_present(pteval) || !pte_write(pteval))
2043 page = vm_normal_page(vma, _address, pteval);
2044 if (unlikely(!page))
2047 * Chose the node of the first page. This could
2048 * be more sophisticated and look at more pages,
2049 * but isn't for now.
2052 node = page_to_nid(page);
2053 VM_BUG_ON(PageCompound(page));
2054 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2056 /* cannot use mapcount: can't collapse if there's a gup pin */
2057 if (page_count(page) != 1)
2059 if (pte_young(pteval) || PageReferenced(page) ||
2060 mmu_notifier_test_young(vma->vm_mm, address))
2066 pte_unmap_unlock(pte, ptl);
2068 /* collapse_huge_page will return with the mmap_sem released */
2069 collapse_huge_page(mm, address, hpage, vma, node);
2074 static void collect_mm_slot(struct mm_slot *mm_slot)
2076 struct mm_struct *mm = mm_slot->mm;
2078 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2080 if (khugepaged_test_exit(mm)) {
2082 hlist_del(&mm_slot->hash);
2083 list_del(&mm_slot->mm_node);
2086 * Not strictly needed because the mm exited already.
2088 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2091 /* khugepaged_mm_lock actually not necessary for the below */
2092 free_mm_slot(mm_slot);
2097 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2098 struct page **hpage)
2099 __releases(&khugepaged_mm_lock)
2100 __acquires(&khugepaged_mm_lock)
2102 struct mm_slot *mm_slot;
2103 struct mm_struct *mm;
2104 struct vm_area_struct *vma;
2108 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2110 if (khugepaged_scan.mm_slot)
2111 mm_slot = khugepaged_scan.mm_slot;
2113 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2114 struct mm_slot, mm_node);
2115 khugepaged_scan.address = 0;
2116 khugepaged_scan.mm_slot = mm_slot;
2118 spin_unlock(&khugepaged_mm_lock);
2121 down_read(&mm->mmap_sem);
2122 if (unlikely(khugepaged_test_exit(mm)))
2125 vma = find_vma(mm, khugepaged_scan.address);
2128 for (; vma; vma = vma->vm_next) {
2129 unsigned long hstart, hend;
2132 if (unlikely(khugepaged_test_exit(mm))) {
2137 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2138 !khugepaged_always()) ||
2139 (vma->vm_flags & VM_NOHUGEPAGE)) {
2144 if (!vma->anon_vma || vma->vm_ops)
2146 if (is_vma_temporary_stack(vma))
2149 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2150 * must be true too, verify it here.
2152 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2153 vma->vm_flags & VM_NO_THP);
2155 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2156 hend = vma->vm_end & HPAGE_PMD_MASK;
2159 if (khugepaged_scan.address > hend)
2161 if (khugepaged_scan.address < hstart)
2162 khugepaged_scan.address = hstart;
2163 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2165 while (khugepaged_scan.address < hend) {
2168 if (unlikely(khugepaged_test_exit(mm)))
2169 goto breakouterloop;
2171 VM_BUG_ON(khugepaged_scan.address < hstart ||
2172 khugepaged_scan.address + HPAGE_PMD_SIZE >
2174 ret = khugepaged_scan_pmd(mm, vma,
2175 khugepaged_scan.address,
2177 /* move to next address */
2178 khugepaged_scan.address += HPAGE_PMD_SIZE;
2179 progress += HPAGE_PMD_NR;
2181 /* we released mmap_sem so break loop */
2182 goto breakouterloop_mmap_sem;
2183 if (progress >= pages)
2184 goto breakouterloop;
2188 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2189 breakouterloop_mmap_sem:
2191 spin_lock(&khugepaged_mm_lock);
2192 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2194 * Release the current mm_slot if this mm is about to die, or
2195 * if we scanned all vmas of this mm.
2197 if (khugepaged_test_exit(mm) || !vma) {
2199 * Make sure that if mm_users is reaching zero while
2200 * khugepaged runs here, khugepaged_exit will find
2201 * mm_slot not pointing to the exiting mm.
2203 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2204 khugepaged_scan.mm_slot = list_entry(
2205 mm_slot->mm_node.next,
2206 struct mm_slot, mm_node);
2207 khugepaged_scan.address = 0;
2209 khugepaged_scan.mm_slot = NULL;
2210 khugepaged_full_scans++;
2213 collect_mm_slot(mm_slot);
2219 static int khugepaged_has_work(void)
2221 return !list_empty(&khugepaged_scan.mm_head) &&
2222 khugepaged_enabled();
2225 static int khugepaged_wait_event(void)
2227 return !list_empty(&khugepaged_scan.mm_head) ||
2228 !khugepaged_enabled();
2231 static void khugepaged_do_scan(struct page **hpage)
2233 unsigned int progress = 0, pass_through_head = 0;
2234 unsigned int pages = khugepaged_pages_to_scan;
2236 barrier(); /* write khugepaged_pages_to_scan to local stack */
2238 while (progress < pages) {
2243 *hpage = alloc_hugepage(khugepaged_defrag());
2244 if (unlikely(!*hpage)) {
2245 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2248 count_vm_event(THP_COLLAPSE_ALLOC);
2255 if (unlikely(kthread_should_stop() || freezing(current)))
2258 spin_lock(&khugepaged_mm_lock);
2259 if (!khugepaged_scan.mm_slot)
2260 pass_through_head++;
2261 if (khugepaged_has_work() &&
2262 pass_through_head < 2)
2263 progress += khugepaged_scan_mm_slot(pages - progress,
2267 spin_unlock(&khugepaged_mm_lock);
2271 static void khugepaged_alloc_sleep(void)
2273 wait_event_freezable_timeout(khugepaged_wait, false,
2274 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2278 static struct page *khugepaged_alloc_hugepage(void)
2283 hpage = alloc_hugepage(khugepaged_defrag());
2285 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2286 khugepaged_alloc_sleep();
2288 count_vm_event(THP_COLLAPSE_ALLOC);
2289 } while (unlikely(!hpage) &&
2290 likely(khugepaged_enabled()));
2295 static void khugepaged_loop(void)
2302 while (likely(khugepaged_enabled())) {
2304 hpage = khugepaged_alloc_hugepage();
2305 if (unlikely(!hpage))
2308 if (IS_ERR(hpage)) {
2309 khugepaged_alloc_sleep();
2314 khugepaged_do_scan(&hpage);
2320 if (unlikely(kthread_should_stop()))
2322 if (khugepaged_has_work()) {
2323 if (!khugepaged_scan_sleep_millisecs)
2325 wait_event_freezable_timeout(khugepaged_wait, false,
2326 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2327 } else if (khugepaged_enabled())
2328 wait_event_freezable(khugepaged_wait,
2329 khugepaged_wait_event());
2333 static int khugepaged(void *none)
2335 struct mm_slot *mm_slot;
2338 set_user_nice(current, 19);
2340 /* serialize with start_khugepaged() */
2341 mutex_lock(&khugepaged_mutex);
2344 mutex_unlock(&khugepaged_mutex);
2345 VM_BUG_ON(khugepaged_thread != current);
2347 VM_BUG_ON(khugepaged_thread != current);
2349 mutex_lock(&khugepaged_mutex);
2350 if (!khugepaged_enabled())
2352 if (unlikely(kthread_should_stop()))
2356 spin_lock(&khugepaged_mm_lock);
2357 mm_slot = khugepaged_scan.mm_slot;
2358 khugepaged_scan.mm_slot = NULL;
2360 collect_mm_slot(mm_slot);
2361 spin_unlock(&khugepaged_mm_lock);
2363 khugepaged_thread = NULL;
2364 mutex_unlock(&khugepaged_mutex);
2369 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2373 spin_lock(&mm->page_table_lock);
2374 if (unlikely(!pmd_trans_huge(*pmd))) {
2375 spin_unlock(&mm->page_table_lock);
2378 page = pmd_page(*pmd);
2379 VM_BUG_ON(!page_count(page));
2381 spin_unlock(&mm->page_table_lock);
2383 split_huge_page(page);
2386 BUG_ON(pmd_trans_huge(*pmd));
2389 static void split_huge_page_address(struct mm_struct *mm,
2390 unsigned long address)
2396 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2398 pgd = pgd_offset(mm, address);
2399 if (!pgd_present(*pgd))
2402 pud = pud_offset(pgd, address);
2403 if (!pud_present(*pud))
2406 pmd = pmd_offset(pud, address);
2407 if (!pmd_present(*pmd))
2410 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2411 * materialize from under us.
2413 split_huge_page_pmd(mm, pmd);
2416 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2417 unsigned long start,
2422 * If the new start address isn't hpage aligned and it could
2423 * previously contain an hugepage: check if we need to split
2426 if (start & ~HPAGE_PMD_MASK &&
2427 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2428 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2429 split_huge_page_address(vma->vm_mm, start);
2432 * If the new end address isn't hpage aligned and it could
2433 * previously contain an hugepage: check if we need to split
2436 if (end & ~HPAGE_PMD_MASK &&
2437 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2438 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2439 split_huge_page_address(vma->vm_mm, end);
2442 * If we're also updating the vma->vm_next->vm_start, if the new
2443 * vm_next->vm_start isn't page aligned and it could previously
2444 * contain an hugepage: check if we need to split an huge pmd.
2446 if (adjust_next > 0) {
2447 struct vm_area_struct *next = vma->vm_next;
2448 unsigned long nstart = next->vm_start;
2449 nstart += adjust_next << PAGE_SHIFT;
2450 if (nstart & ~HPAGE_PMD_MASK &&
2451 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2452 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2453 split_huge_page_address(next->vm_mm, nstart);