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()) {
142 if (!khugepaged_thread)
143 khugepaged_thread = kthread_run(khugepaged, NULL,
145 if (unlikely(IS_ERR(khugepaged_thread))) {
147 "khugepaged: kthread_run(khugepaged) failed\n");
148 err = PTR_ERR(khugepaged_thread);
149 khugepaged_thread = NULL;
152 if (!list_empty(&khugepaged_scan.mm_head))
153 wake_up_interruptible(&khugepaged_wait);
155 set_recommended_min_free_kbytes();
156 } else if (khugepaged_thread) {
157 kthread_stop(khugepaged_thread);
158 khugepaged_thread = NULL;
166 static ssize_t double_flag_show(struct kobject *kobj,
167 struct kobj_attribute *attr, char *buf,
168 enum transparent_hugepage_flag enabled,
169 enum transparent_hugepage_flag req_madv)
171 if (test_bit(enabled, &transparent_hugepage_flags)) {
172 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
173 return sprintf(buf, "[always] madvise never\n");
174 } else if (test_bit(req_madv, &transparent_hugepage_flags))
175 return sprintf(buf, "always [madvise] never\n");
177 return sprintf(buf, "always madvise [never]\n");
179 static ssize_t double_flag_store(struct kobject *kobj,
180 struct kobj_attribute *attr,
181 const char *buf, size_t count,
182 enum transparent_hugepage_flag enabled,
183 enum transparent_hugepage_flag req_madv)
185 if (!memcmp("always", buf,
186 min(sizeof("always")-1, count))) {
187 set_bit(enabled, &transparent_hugepage_flags);
188 clear_bit(req_madv, &transparent_hugepage_flags);
189 } else if (!memcmp("madvise", buf,
190 min(sizeof("madvise")-1, count))) {
191 clear_bit(enabled, &transparent_hugepage_flags);
192 set_bit(req_madv, &transparent_hugepage_flags);
193 } else if (!memcmp("never", buf,
194 min(sizeof("never")-1, count))) {
195 clear_bit(enabled, &transparent_hugepage_flags);
196 clear_bit(req_madv, &transparent_hugepage_flags);
203 static ssize_t enabled_show(struct kobject *kobj,
204 struct kobj_attribute *attr, char *buf)
206 return double_flag_show(kobj, attr, buf,
207 TRANSPARENT_HUGEPAGE_FLAG,
208 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
210 static ssize_t enabled_store(struct kobject *kobj,
211 struct kobj_attribute *attr,
212 const char *buf, size_t count)
216 ret = double_flag_store(kobj, attr, buf, count,
217 TRANSPARENT_HUGEPAGE_FLAG,
218 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
223 mutex_lock(&khugepaged_mutex);
224 err = start_khugepaged();
225 mutex_unlock(&khugepaged_mutex);
232 (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
233 &transparent_hugepage_flags) ||
234 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
235 &transparent_hugepage_flags)))
236 set_recommended_min_free_kbytes();
240 static struct kobj_attribute enabled_attr =
241 __ATTR(enabled, 0644, enabled_show, enabled_store);
243 static ssize_t single_flag_show(struct kobject *kobj,
244 struct kobj_attribute *attr, char *buf,
245 enum transparent_hugepage_flag flag)
247 return sprintf(buf, "%d\n",
248 !!test_bit(flag, &transparent_hugepage_flags));
251 static ssize_t single_flag_store(struct kobject *kobj,
252 struct kobj_attribute *attr,
253 const char *buf, size_t count,
254 enum transparent_hugepage_flag flag)
259 ret = kstrtoul(buf, 10, &value);
266 set_bit(flag, &transparent_hugepage_flags);
268 clear_bit(flag, &transparent_hugepage_flags);
274 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
275 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
276 * memory just to allocate one more hugepage.
278 static ssize_t defrag_show(struct kobject *kobj,
279 struct kobj_attribute *attr, char *buf)
281 return double_flag_show(kobj, attr, buf,
282 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
283 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
285 static ssize_t defrag_store(struct kobject *kobj,
286 struct kobj_attribute *attr,
287 const char *buf, size_t count)
289 return double_flag_store(kobj, attr, buf, count,
290 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
291 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
293 static struct kobj_attribute defrag_attr =
294 __ATTR(defrag, 0644, defrag_show, defrag_store);
296 #ifdef CONFIG_DEBUG_VM
297 static ssize_t debug_cow_show(struct kobject *kobj,
298 struct kobj_attribute *attr, char *buf)
300 return single_flag_show(kobj, attr, buf,
301 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
303 static ssize_t debug_cow_store(struct kobject *kobj,
304 struct kobj_attribute *attr,
305 const char *buf, size_t count)
307 return single_flag_store(kobj, attr, buf, count,
308 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
310 static struct kobj_attribute debug_cow_attr =
311 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
312 #endif /* CONFIG_DEBUG_VM */
314 static struct attribute *hugepage_attr[] = {
317 #ifdef CONFIG_DEBUG_VM
318 &debug_cow_attr.attr,
323 static struct attribute_group hugepage_attr_group = {
324 .attrs = hugepage_attr,
327 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
328 struct kobj_attribute *attr,
331 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
334 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
335 struct kobj_attribute *attr,
336 const char *buf, size_t count)
341 err = strict_strtoul(buf, 10, &msecs);
342 if (err || msecs > UINT_MAX)
345 khugepaged_scan_sleep_millisecs = msecs;
346 wake_up_interruptible(&khugepaged_wait);
350 static struct kobj_attribute scan_sleep_millisecs_attr =
351 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
352 scan_sleep_millisecs_store);
354 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
355 struct kobj_attribute *attr,
358 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
361 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
362 struct kobj_attribute *attr,
363 const char *buf, size_t count)
368 err = strict_strtoul(buf, 10, &msecs);
369 if (err || msecs > UINT_MAX)
372 khugepaged_alloc_sleep_millisecs = msecs;
373 wake_up_interruptible(&khugepaged_wait);
377 static struct kobj_attribute alloc_sleep_millisecs_attr =
378 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
379 alloc_sleep_millisecs_store);
381 static ssize_t pages_to_scan_show(struct kobject *kobj,
382 struct kobj_attribute *attr,
385 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
387 static ssize_t pages_to_scan_store(struct kobject *kobj,
388 struct kobj_attribute *attr,
389 const char *buf, size_t count)
394 err = strict_strtoul(buf, 10, &pages);
395 if (err || !pages || pages > UINT_MAX)
398 khugepaged_pages_to_scan = pages;
402 static struct kobj_attribute pages_to_scan_attr =
403 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
404 pages_to_scan_store);
406 static ssize_t pages_collapsed_show(struct kobject *kobj,
407 struct kobj_attribute *attr,
410 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
412 static struct kobj_attribute pages_collapsed_attr =
413 __ATTR_RO(pages_collapsed);
415 static ssize_t full_scans_show(struct kobject *kobj,
416 struct kobj_attribute *attr,
419 return sprintf(buf, "%u\n", khugepaged_full_scans);
421 static struct kobj_attribute full_scans_attr =
422 __ATTR_RO(full_scans);
424 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
425 struct kobj_attribute *attr, char *buf)
427 return single_flag_show(kobj, attr, buf,
428 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
430 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
431 struct kobj_attribute *attr,
432 const char *buf, size_t count)
434 return single_flag_store(kobj, attr, buf, count,
435 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
437 static struct kobj_attribute khugepaged_defrag_attr =
438 __ATTR(defrag, 0644, khugepaged_defrag_show,
439 khugepaged_defrag_store);
442 * max_ptes_none controls if khugepaged should collapse hugepages over
443 * any unmapped ptes in turn potentially increasing the memory
444 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
445 * reduce the available free memory in the system as it
446 * runs. Increasing max_ptes_none will instead potentially reduce the
447 * free memory in the system during the khugepaged scan.
449 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
450 struct kobj_attribute *attr,
453 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
455 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
456 struct kobj_attribute *attr,
457 const char *buf, size_t count)
460 unsigned long max_ptes_none;
462 err = strict_strtoul(buf, 10, &max_ptes_none);
463 if (err || max_ptes_none > HPAGE_PMD_NR-1)
466 khugepaged_max_ptes_none = max_ptes_none;
470 static struct kobj_attribute khugepaged_max_ptes_none_attr =
471 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
472 khugepaged_max_ptes_none_store);
474 static struct attribute *khugepaged_attr[] = {
475 &khugepaged_defrag_attr.attr,
476 &khugepaged_max_ptes_none_attr.attr,
477 &pages_to_scan_attr.attr,
478 &pages_collapsed_attr.attr,
479 &full_scans_attr.attr,
480 &scan_sleep_millisecs_attr.attr,
481 &alloc_sleep_millisecs_attr.attr,
485 static struct attribute_group khugepaged_attr_group = {
486 .attrs = khugepaged_attr,
487 .name = "khugepaged",
490 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
494 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
495 if (unlikely(!*hugepage_kobj)) {
496 printk(KERN_ERR "hugepage: failed kobject create\n");
500 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
502 printk(KERN_ERR "hugepage: failed register hugeage group\n");
506 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
508 printk(KERN_ERR "hugepage: failed register hugeage group\n");
509 goto remove_hp_group;
515 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
517 kobject_put(*hugepage_kobj);
521 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
523 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
524 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
525 kobject_put(hugepage_kobj);
528 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
533 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
536 #endif /* CONFIG_SYSFS */
538 static int __init hugepage_init(void)
541 struct kobject *hugepage_kobj;
543 if (!has_transparent_hugepage()) {
544 transparent_hugepage_flags = 0;
548 err = hugepage_init_sysfs(&hugepage_kobj);
552 err = khugepaged_slab_init();
556 err = mm_slots_hash_init();
558 khugepaged_slab_free();
563 * By default disable transparent hugepages on smaller systems,
564 * where the extra memory used could hurt more than TLB overhead
565 * is likely to save. The admin can still enable it through /sys.
567 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
568 transparent_hugepage_flags = 0;
572 set_recommended_min_free_kbytes();
576 hugepage_exit_sysfs(hugepage_kobj);
579 module_init(hugepage_init)
581 static int __init setup_transparent_hugepage(char *str)
586 if (!strcmp(str, "always")) {
587 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
588 &transparent_hugepage_flags);
589 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
590 &transparent_hugepage_flags);
592 } else if (!strcmp(str, "madvise")) {
593 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
594 &transparent_hugepage_flags);
595 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
596 &transparent_hugepage_flags);
598 } else if (!strcmp(str, "never")) {
599 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
600 &transparent_hugepage_flags);
601 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
602 &transparent_hugepage_flags);
608 "transparent_hugepage= cannot parse, ignored\n");
611 __setup("transparent_hugepage=", setup_transparent_hugepage);
613 static void prepare_pmd_huge_pte(pgtable_t pgtable,
614 struct mm_struct *mm)
616 assert_spin_locked(&mm->page_table_lock);
619 if (!mm->pmd_huge_pte)
620 INIT_LIST_HEAD(&pgtable->lru);
622 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
623 mm->pmd_huge_pte = pgtable;
626 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
628 if (likely(vma->vm_flags & VM_WRITE))
629 pmd = pmd_mkwrite(pmd);
633 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
634 struct vm_area_struct *vma,
635 unsigned long haddr, pmd_t *pmd,
640 VM_BUG_ON(!PageCompound(page));
641 pgtable = pte_alloc_one(mm, haddr);
642 if (unlikely(!pgtable))
645 clear_huge_page(page, haddr, HPAGE_PMD_NR);
646 __SetPageUptodate(page);
648 spin_lock(&mm->page_table_lock);
649 if (unlikely(!pmd_none(*pmd))) {
650 spin_unlock(&mm->page_table_lock);
651 mem_cgroup_uncharge_page(page);
653 pte_free(mm, pgtable);
656 entry = mk_pmd(page, vma->vm_page_prot);
657 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
658 entry = pmd_mkhuge(entry);
660 * The spinlocking to take the lru_lock inside
661 * page_add_new_anon_rmap() acts as a full memory
662 * barrier to be sure clear_huge_page writes become
663 * visible after the set_pmd_at() write.
665 page_add_new_anon_rmap(page, vma, haddr);
666 set_pmd_at(mm, haddr, pmd, entry);
667 prepare_pmd_huge_pte(pgtable, mm);
668 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
670 spin_unlock(&mm->page_table_lock);
676 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
678 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
681 static inline struct page *alloc_hugepage_vma(int defrag,
682 struct vm_area_struct *vma,
683 unsigned long haddr, int nd,
686 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
687 HPAGE_PMD_ORDER, vma, haddr, nd);
691 static inline struct page *alloc_hugepage(int defrag)
693 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
698 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
699 unsigned long address, pmd_t *pmd,
703 unsigned long haddr = address & HPAGE_PMD_MASK;
706 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
707 if (unlikely(anon_vma_prepare(vma)))
709 if (unlikely(khugepaged_enter(vma)))
711 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
712 vma, haddr, numa_node_id(), 0);
713 if (unlikely(!page)) {
714 count_vm_event(THP_FAULT_FALLBACK);
717 count_vm_event(THP_FAULT_ALLOC);
718 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
722 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
724 mem_cgroup_uncharge_page(page);
733 * Use __pte_alloc instead of pte_alloc_map, because we can't
734 * run pte_offset_map on the pmd, if an huge pmd could
735 * materialize from under us from a different thread.
737 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
739 /* if an huge pmd materialized from under us just retry later */
740 if (unlikely(pmd_trans_huge(*pmd)))
743 * A regular pmd is established and it can't morph into a huge pmd
744 * from under us anymore at this point because we hold the mmap_sem
745 * read mode and khugepaged takes it in write mode. So now it's
746 * safe to run pte_offset_map().
748 pte = pte_offset_map(pmd, address);
749 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
752 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
753 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
754 struct vm_area_struct *vma)
756 struct page *src_page;
762 pgtable = pte_alloc_one(dst_mm, addr);
763 if (unlikely(!pgtable))
766 spin_lock(&dst_mm->page_table_lock);
767 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
771 if (unlikely(!pmd_trans_huge(pmd))) {
772 pte_free(dst_mm, pgtable);
775 if (unlikely(pmd_trans_splitting(pmd))) {
776 /* split huge page running from under us */
777 spin_unlock(&src_mm->page_table_lock);
778 spin_unlock(&dst_mm->page_table_lock);
779 pte_free(dst_mm, pgtable);
781 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
784 src_page = pmd_page(pmd);
785 VM_BUG_ON(!PageHead(src_page));
787 page_dup_rmap(src_page);
788 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
790 pmdp_set_wrprotect(src_mm, addr, src_pmd);
791 pmd = pmd_mkold(pmd_wrprotect(pmd));
792 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
793 prepare_pmd_huge_pte(pgtable, dst_mm);
798 spin_unlock(&src_mm->page_table_lock);
799 spin_unlock(&dst_mm->page_table_lock);
804 /* no "address" argument so destroys page coloring of some arch */
805 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
809 assert_spin_locked(&mm->page_table_lock);
812 pgtable = mm->pmd_huge_pte;
813 if (list_empty(&pgtable->lru))
814 mm->pmd_huge_pte = NULL;
816 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
818 list_del(&pgtable->lru);
823 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
824 struct vm_area_struct *vma,
825 unsigned long address,
826 pmd_t *pmd, pmd_t orig_pmd,
835 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
837 if (unlikely(!pages)) {
842 for (i = 0; i < HPAGE_PMD_NR; i++) {
843 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
845 vma, address, page_to_nid(page));
846 if (unlikely(!pages[i] ||
847 mem_cgroup_newpage_charge(pages[i], mm,
851 mem_cgroup_uncharge_start();
853 mem_cgroup_uncharge_page(pages[i]);
856 mem_cgroup_uncharge_end();
863 for (i = 0; i < HPAGE_PMD_NR; i++) {
864 copy_user_highpage(pages[i], page + i,
865 haddr + PAGE_SIZE * i, vma);
866 __SetPageUptodate(pages[i]);
870 spin_lock(&mm->page_table_lock);
871 if (unlikely(!pmd_same(*pmd, orig_pmd)))
873 VM_BUG_ON(!PageHead(page));
875 pmdp_clear_flush_notify(vma, haddr, pmd);
876 /* leave pmd empty until pte is filled */
878 pgtable = get_pmd_huge_pte(mm);
879 pmd_populate(mm, &_pmd, pgtable);
881 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
883 entry = mk_pte(pages[i], vma->vm_page_prot);
884 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
885 page_add_new_anon_rmap(pages[i], vma, haddr);
886 pte = pte_offset_map(&_pmd, haddr);
887 VM_BUG_ON(!pte_none(*pte));
888 set_pte_at(mm, haddr, pte, entry);
893 smp_wmb(); /* make pte visible before pmd */
894 pmd_populate(mm, pmd, pgtable);
895 page_remove_rmap(page);
896 spin_unlock(&mm->page_table_lock);
898 ret |= VM_FAULT_WRITE;
905 spin_unlock(&mm->page_table_lock);
906 mem_cgroup_uncharge_start();
907 for (i = 0; i < HPAGE_PMD_NR; i++) {
908 mem_cgroup_uncharge_page(pages[i]);
911 mem_cgroup_uncharge_end();
916 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
917 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
920 struct page *page, *new_page;
923 VM_BUG_ON(!vma->anon_vma);
924 spin_lock(&mm->page_table_lock);
925 if (unlikely(!pmd_same(*pmd, orig_pmd)))
928 page = pmd_page(orig_pmd);
929 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
930 haddr = address & HPAGE_PMD_MASK;
931 if (page_mapcount(page) == 1) {
933 entry = pmd_mkyoung(orig_pmd);
934 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
935 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
936 update_mmu_cache(vma, address, entry);
937 ret |= VM_FAULT_WRITE;
941 spin_unlock(&mm->page_table_lock);
943 if (transparent_hugepage_enabled(vma) &&
944 !transparent_hugepage_debug_cow())
945 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
946 vma, haddr, numa_node_id(), 0);
950 if (unlikely(!new_page)) {
951 count_vm_event(THP_FAULT_FALLBACK);
952 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
953 pmd, orig_pmd, page, haddr);
954 if (ret & VM_FAULT_OOM)
955 split_huge_page(page);
959 count_vm_event(THP_FAULT_ALLOC);
961 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
963 split_huge_page(page);
969 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
970 __SetPageUptodate(new_page);
972 spin_lock(&mm->page_table_lock);
974 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
975 spin_unlock(&mm->page_table_lock);
976 mem_cgroup_uncharge_page(new_page);
981 VM_BUG_ON(!PageHead(page));
982 entry = mk_pmd(new_page, vma->vm_page_prot);
983 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
984 entry = pmd_mkhuge(entry);
985 pmdp_clear_flush_notify(vma, haddr, pmd);
986 page_add_new_anon_rmap(new_page, vma, haddr);
987 set_pmd_at(mm, haddr, pmd, entry);
988 update_mmu_cache(vma, address, entry);
989 page_remove_rmap(page);
991 ret |= VM_FAULT_WRITE;
994 spin_unlock(&mm->page_table_lock);
999 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
1004 struct page *page = NULL;
1006 assert_spin_locked(&mm->page_table_lock);
1008 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1011 page = pmd_page(*pmd);
1012 VM_BUG_ON(!PageHead(page));
1013 if (flags & FOLL_TOUCH) {
1016 * We should set the dirty bit only for FOLL_WRITE but
1017 * for now the dirty bit in the pmd is meaningless.
1018 * And if the dirty bit will become meaningful and
1019 * we'll only set it with FOLL_WRITE, an atomic
1020 * set_bit will be required on the pmd to set the
1021 * young bit, instead of the current set_pmd_at.
1023 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1024 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1026 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1027 VM_BUG_ON(!PageCompound(page));
1028 if (flags & FOLL_GET)
1029 get_page_foll(page);
1035 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1036 pmd_t *pmd, unsigned long addr)
1040 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1043 pgtable = get_pmd_huge_pte(tlb->mm);
1044 page = pmd_page(*pmd);
1046 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1047 page_remove_rmap(page);
1048 VM_BUG_ON(page_mapcount(page) < 0);
1049 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1050 VM_BUG_ON(!PageHead(page));
1052 spin_unlock(&tlb->mm->page_table_lock);
1053 tlb_remove_page(tlb, page);
1054 pte_free(tlb->mm, pgtable);
1060 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1061 unsigned long addr, unsigned long end,
1066 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1068 * All logical pages in the range are present
1069 * if backed by a huge page.
1071 spin_unlock(&vma->vm_mm->page_table_lock);
1072 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1079 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1080 unsigned long old_addr,
1081 unsigned long new_addr, unsigned long old_end,
1082 pmd_t *old_pmd, pmd_t *new_pmd)
1087 struct mm_struct *mm = vma->vm_mm;
1089 if ((old_addr & ~HPAGE_PMD_MASK) ||
1090 (new_addr & ~HPAGE_PMD_MASK) ||
1091 old_end - old_addr < HPAGE_PMD_SIZE ||
1092 (new_vma->vm_flags & VM_NOHUGEPAGE))
1096 * The destination pmd shouldn't be established, free_pgtables()
1097 * should have release it.
1099 if (WARN_ON(!pmd_none(*new_pmd))) {
1100 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1104 ret = __pmd_trans_huge_lock(old_pmd, vma);
1106 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1107 VM_BUG_ON(!pmd_none(*new_pmd));
1108 set_pmd_at(mm, new_addr, new_pmd, pmd);
1109 spin_unlock(&mm->page_table_lock);
1115 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1116 unsigned long addr, pgprot_t newprot)
1118 struct mm_struct *mm = vma->vm_mm;
1121 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1123 entry = pmdp_get_and_clear(mm, addr, pmd);
1124 entry = pmd_modify(entry, newprot);
1125 set_pmd_at(mm, addr, pmd, entry);
1126 spin_unlock(&vma->vm_mm->page_table_lock);
1134 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1135 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1137 * Note that if it returns 1, this routine returns without unlocking page
1138 * table locks. So callers must unlock them.
1140 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1142 spin_lock(&vma->vm_mm->page_table_lock);
1143 if (likely(pmd_trans_huge(*pmd))) {
1144 if (unlikely(pmd_trans_splitting(*pmd))) {
1145 spin_unlock(&vma->vm_mm->page_table_lock);
1146 wait_split_huge_page(vma->anon_vma, pmd);
1149 /* Thp mapped by 'pmd' is stable, so we can
1150 * handle it as it is. */
1154 spin_unlock(&vma->vm_mm->page_table_lock);
1158 pmd_t *page_check_address_pmd(struct page *page,
1159 struct mm_struct *mm,
1160 unsigned long address,
1161 enum page_check_address_pmd_flag flag)
1165 pmd_t *pmd, *ret = NULL;
1167 if (address & ~HPAGE_PMD_MASK)
1170 pgd = pgd_offset(mm, address);
1171 if (!pgd_present(*pgd))
1174 pud = pud_offset(pgd, address);
1175 if (!pud_present(*pud))
1178 pmd = pmd_offset(pud, address);
1181 if (pmd_page(*pmd) != page)
1184 * split_vma() may create temporary aliased mappings. There is
1185 * no risk as long as all huge pmd are found and have their
1186 * splitting bit set before __split_huge_page_refcount
1187 * runs. Finding the same huge pmd more than once during the
1188 * same rmap walk is not a problem.
1190 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1191 pmd_trans_splitting(*pmd))
1193 if (pmd_trans_huge(*pmd)) {
1194 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1195 !pmd_trans_splitting(*pmd));
1202 static int __split_huge_page_splitting(struct page *page,
1203 struct vm_area_struct *vma,
1204 unsigned long address)
1206 struct mm_struct *mm = vma->vm_mm;
1210 spin_lock(&mm->page_table_lock);
1211 pmd = page_check_address_pmd(page, mm, address,
1212 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1215 * We can't temporarily set the pmd to null in order
1216 * to split it, the pmd must remain marked huge at all
1217 * times or the VM won't take the pmd_trans_huge paths
1218 * and it won't wait on the anon_vma->root->mutex to
1219 * serialize against split_huge_page*.
1221 pmdp_splitting_flush_notify(vma, address, pmd);
1224 spin_unlock(&mm->page_table_lock);
1229 static void __split_huge_page_refcount(struct page *page)
1232 struct zone *zone = page_zone(page);
1233 struct lruvec *lruvec;
1236 /* prevent PageLRU to go away from under us, and freeze lru stats */
1237 spin_lock_irq(&zone->lru_lock);
1238 lruvec = mem_cgroup_page_lruvec(page, zone);
1240 compound_lock(page);
1241 /* complete memcg works before add pages to LRU */
1242 mem_cgroup_split_huge_fixup(page);
1244 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1245 struct page *page_tail = page + i;
1247 /* tail_page->_mapcount cannot change */
1248 BUG_ON(page_mapcount(page_tail) < 0);
1249 tail_count += page_mapcount(page_tail);
1250 /* check for overflow */
1251 BUG_ON(tail_count < 0);
1252 BUG_ON(atomic_read(&page_tail->_count) != 0);
1254 * tail_page->_count is zero and not changing from
1255 * under us. But get_page_unless_zero() may be running
1256 * from under us on the tail_page. If we used
1257 * atomic_set() below instead of atomic_add(), we
1258 * would then run atomic_set() concurrently with
1259 * get_page_unless_zero(), and atomic_set() is
1260 * implemented in C not using locked ops. spin_unlock
1261 * on x86 sometime uses locked ops because of PPro
1262 * errata 66, 92, so unless somebody can guarantee
1263 * atomic_set() here would be safe on all archs (and
1264 * not only on x86), it's safer to use atomic_add().
1266 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1267 &page_tail->_count);
1269 /* after clearing PageTail the gup refcount can be released */
1273 * retain hwpoison flag of the poisoned tail page:
1274 * fix for the unsuitable process killed on Guest Machine(KVM)
1275 * by the memory-failure.
1277 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1278 page_tail->flags |= (page->flags &
1279 ((1L << PG_referenced) |
1280 (1L << PG_swapbacked) |
1281 (1L << PG_mlocked) |
1282 (1L << PG_uptodate)));
1283 page_tail->flags |= (1L << PG_dirty);
1285 /* clear PageTail before overwriting first_page */
1289 * __split_huge_page_splitting() already set the
1290 * splitting bit in all pmd that could map this
1291 * hugepage, that will ensure no CPU can alter the
1292 * mapcount on the head page. The mapcount is only
1293 * accounted in the head page and it has to be
1294 * transferred to all tail pages in the below code. So
1295 * for this code to be safe, the split the mapcount
1296 * can't change. But that doesn't mean userland can't
1297 * keep changing and reading the page contents while
1298 * we transfer the mapcount, so the pmd splitting
1299 * status is achieved setting a reserved bit in the
1300 * pmd, not by clearing the present bit.
1302 page_tail->_mapcount = page->_mapcount;
1304 BUG_ON(page_tail->mapping);
1305 page_tail->mapping = page->mapping;
1307 page_tail->index = page->index + i;
1309 BUG_ON(!PageAnon(page_tail));
1310 BUG_ON(!PageUptodate(page_tail));
1311 BUG_ON(!PageDirty(page_tail));
1312 BUG_ON(!PageSwapBacked(page_tail));
1314 lru_add_page_tail(page, page_tail, lruvec);
1316 atomic_sub(tail_count, &page->_count);
1317 BUG_ON(atomic_read(&page->_count) <= 0);
1319 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1320 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1322 ClearPageCompound(page);
1323 compound_unlock(page);
1324 spin_unlock_irq(&zone->lru_lock);
1326 for (i = 1; i < HPAGE_PMD_NR; i++) {
1327 struct page *page_tail = page + i;
1328 BUG_ON(page_count(page_tail) <= 0);
1330 * Tail pages may be freed if there wasn't any mapping
1331 * like if add_to_swap() is running on a lru page that
1332 * had its mapping zapped. And freeing these pages
1333 * requires taking the lru_lock so we do the put_page
1334 * of the tail pages after the split is complete.
1336 put_page(page_tail);
1340 * Only the head page (now become a regular page) is required
1341 * to be pinned by the caller.
1343 BUG_ON(page_count(page) <= 0);
1346 static int __split_huge_page_map(struct page *page,
1347 struct vm_area_struct *vma,
1348 unsigned long address)
1350 struct mm_struct *mm = vma->vm_mm;
1354 unsigned long haddr;
1356 spin_lock(&mm->page_table_lock);
1357 pmd = page_check_address_pmd(page, mm, address,
1358 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1360 pgtable = get_pmd_huge_pte(mm);
1361 pmd_populate(mm, &_pmd, pgtable);
1363 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1364 i++, haddr += PAGE_SIZE) {
1366 BUG_ON(PageCompound(page+i));
1367 entry = mk_pte(page + i, vma->vm_page_prot);
1368 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1369 if (!pmd_write(*pmd))
1370 entry = pte_wrprotect(entry);
1372 BUG_ON(page_mapcount(page) != 1);
1373 if (!pmd_young(*pmd))
1374 entry = pte_mkold(entry);
1375 pte = pte_offset_map(&_pmd, haddr);
1376 BUG_ON(!pte_none(*pte));
1377 set_pte_at(mm, haddr, pte, entry);
1381 smp_wmb(); /* make pte visible before pmd */
1383 * Up to this point the pmd is present and huge and
1384 * userland has the whole access to the hugepage
1385 * during the split (which happens in place). If we
1386 * overwrite the pmd with the not-huge version
1387 * pointing to the pte here (which of course we could
1388 * if all CPUs were bug free), userland could trigger
1389 * a small page size TLB miss on the small sized TLB
1390 * while the hugepage TLB entry is still established
1391 * in the huge TLB. Some CPU doesn't like that. See
1392 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1393 * Erratum 383 on page 93. Intel should be safe but is
1394 * also warns that it's only safe if the permission
1395 * and cache attributes of the two entries loaded in
1396 * the two TLB is identical (which should be the case
1397 * here). But it is generally safer to never allow
1398 * small and huge TLB entries for the same virtual
1399 * address to be loaded simultaneously. So instead of
1400 * doing "pmd_populate(); flush_tlb_range();" we first
1401 * mark the current pmd notpresent (atomically because
1402 * here the pmd_trans_huge and pmd_trans_splitting
1403 * must remain set at all times on the pmd until the
1404 * split is complete for this pmd), then we flush the
1405 * SMP TLB and finally we write the non-huge version
1406 * of the pmd entry with pmd_populate.
1408 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1409 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1410 pmd_populate(mm, pmd, pgtable);
1413 spin_unlock(&mm->page_table_lock);
1418 /* must be called with anon_vma->root->mutex hold */
1419 static void __split_huge_page(struct page *page,
1420 struct anon_vma *anon_vma)
1422 int mapcount, mapcount2;
1423 struct anon_vma_chain *avc;
1425 BUG_ON(!PageHead(page));
1426 BUG_ON(PageTail(page));
1429 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1430 struct vm_area_struct *vma = avc->vma;
1431 unsigned long addr = vma_address(page, vma);
1432 BUG_ON(is_vma_temporary_stack(vma));
1433 if (addr == -EFAULT)
1435 mapcount += __split_huge_page_splitting(page, vma, addr);
1438 * It is critical that new vmas are added to the tail of the
1439 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1440 * and establishes a child pmd before
1441 * __split_huge_page_splitting() freezes the parent pmd (so if
1442 * we fail to prevent copy_huge_pmd() from running until the
1443 * whole __split_huge_page() is complete), we will still see
1444 * the newly established pmd of the child later during the
1445 * walk, to be able to set it as pmd_trans_splitting too.
1447 if (mapcount != page_mapcount(page))
1448 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1449 mapcount, page_mapcount(page));
1450 BUG_ON(mapcount != page_mapcount(page));
1452 __split_huge_page_refcount(page);
1455 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1456 struct vm_area_struct *vma = avc->vma;
1457 unsigned long addr = vma_address(page, vma);
1458 BUG_ON(is_vma_temporary_stack(vma));
1459 if (addr == -EFAULT)
1461 mapcount2 += __split_huge_page_map(page, vma, addr);
1463 if (mapcount != mapcount2)
1464 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1465 mapcount, mapcount2, page_mapcount(page));
1466 BUG_ON(mapcount != mapcount2);
1469 int split_huge_page(struct page *page)
1471 struct anon_vma *anon_vma;
1474 BUG_ON(!PageAnon(page));
1475 anon_vma = page_lock_anon_vma(page);
1479 if (!PageCompound(page))
1482 BUG_ON(!PageSwapBacked(page));
1483 __split_huge_page(page, anon_vma);
1484 count_vm_event(THP_SPLIT);
1486 BUG_ON(PageCompound(page));
1488 page_unlock_anon_vma(anon_vma);
1493 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1495 int hugepage_madvise(struct vm_area_struct *vma,
1496 unsigned long *vm_flags, int advice)
1501 * Be somewhat over-protective like KSM for now!
1503 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1505 *vm_flags &= ~VM_NOHUGEPAGE;
1506 *vm_flags |= VM_HUGEPAGE;
1508 * If the vma become good for khugepaged to scan,
1509 * register it here without waiting a page fault that
1510 * may not happen any time soon.
1512 if (unlikely(khugepaged_enter_vma_merge(vma)))
1515 case MADV_NOHUGEPAGE:
1517 * Be somewhat over-protective like KSM for now!
1519 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1521 *vm_flags &= ~VM_HUGEPAGE;
1522 *vm_flags |= VM_NOHUGEPAGE;
1524 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1525 * this vma even if we leave the mm registered in khugepaged if
1526 * it got registered before VM_NOHUGEPAGE was set.
1534 static int __init khugepaged_slab_init(void)
1536 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1537 sizeof(struct mm_slot),
1538 __alignof__(struct mm_slot), 0, NULL);
1545 static void __init khugepaged_slab_free(void)
1547 kmem_cache_destroy(mm_slot_cache);
1548 mm_slot_cache = NULL;
1551 static inline struct mm_slot *alloc_mm_slot(void)
1553 if (!mm_slot_cache) /* initialization failed */
1555 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1558 static inline void free_mm_slot(struct mm_slot *mm_slot)
1560 kmem_cache_free(mm_slot_cache, mm_slot);
1563 static int __init mm_slots_hash_init(void)
1565 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1573 static void __init mm_slots_hash_free(void)
1575 kfree(mm_slots_hash);
1576 mm_slots_hash = NULL;
1580 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1582 struct mm_slot *mm_slot;
1583 struct hlist_head *bucket;
1584 struct hlist_node *node;
1586 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1587 % MM_SLOTS_HASH_HEADS];
1588 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1589 if (mm == mm_slot->mm)
1595 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1596 struct mm_slot *mm_slot)
1598 struct hlist_head *bucket;
1600 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1601 % MM_SLOTS_HASH_HEADS];
1603 hlist_add_head(&mm_slot->hash, bucket);
1606 static inline int khugepaged_test_exit(struct mm_struct *mm)
1608 return atomic_read(&mm->mm_users) == 0;
1611 int __khugepaged_enter(struct mm_struct *mm)
1613 struct mm_slot *mm_slot;
1616 mm_slot = alloc_mm_slot();
1620 /* __khugepaged_exit() must not run from under us */
1621 VM_BUG_ON(khugepaged_test_exit(mm));
1622 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1623 free_mm_slot(mm_slot);
1627 spin_lock(&khugepaged_mm_lock);
1628 insert_to_mm_slots_hash(mm, mm_slot);
1630 * Insert just behind the scanning cursor, to let the area settle
1633 wakeup = list_empty(&khugepaged_scan.mm_head);
1634 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1635 spin_unlock(&khugepaged_mm_lock);
1637 atomic_inc(&mm->mm_count);
1639 wake_up_interruptible(&khugepaged_wait);
1644 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1646 unsigned long hstart, hend;
1649 * Not yet faulted in so we will register later in the
1650 * page fault if needed.
1654 /* khugepaged not yet working on file or special mappings */
1656 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1657 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1658 hend = vma->vm_end & HPAGE_PMD_MASK;
1660 return khugepaged_enter(vma);
1664 void __khugepaged_exit(struct mm_struct *mm)
1666 struct mm_slot *mm_slot;
1669 spin_lock(&khugepaged_mm_lock);
1670 mm_slot = get_mm_slot(mm);
1671 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1672 hlist_del(&mm_slot->hash);
1673 list_del(&mm_slot->mm_node);
1676 spin_unlock(&khugepaged_mm_lock);
1679 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1680 free_mm_slot(mm_slot);
1682 } else if (mm_slot) {
1684 * This is required to serialize against
1685 * khugepaged_test_exit() (which is guaranteed to run
1686 * under mmap sem read mode). Stop here (after we
1687 * return all pagetables will be destroyed) until
1688 * khugepaged has finished working on the pagetables
1689 * under the mmap_sem.
1691 down_write(&mm->mmap_sem);
1692 up_write(&mm->mmap_sem);
1696 static void release_pte_page(struct page *page)
1698 /* 0 stands for page_is_file_cache(page) == false */
1699 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1701 putback_lru_page(page);
1704 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1706 while (--_pte >= pte) {
1707 pte_t pteval = *_pte;
1708 if (!pte_none(pteval))
1709 release_pte_page(pte_page(pteval));
1713 static void release_all_pte_pages(pte_t *pte)
1715 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1718 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1719 unsigned long address,
1724 int referenced = 0, isolated = 0, none = 0;
1725 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1726 _pte++, address += PAGE_SIZE) {
1727 pte_t pteval = *_pte;
1728 if (pte_none(pteval)) {
1729 if (++none <= khugepaged_max_ptes_none)
1732 release_pte_pages(pte, _pte);
1736 if (!pte_present(pteval) || !pte_write(pteval)) {
1737 release_pte_pages(pte, _pte);
1740 page = vm_normal_page(vma, address, pteval);
1741 if (unlikely(!page)) {
1742 release_pte_pages(pte, _pte);
1745 VM_BUG_ON(PageCompound(page));
1746 BUG_ON(!PageAnon(page));
1747 VM_BUG_ON(!PageSwapBacked(page));
1749 /* cannot use mapcount: can't collapse if there's a gup pin */
1750 if (page_count(page) != 1) {
1751 release_pte_pages(pte, _pte);
1755 * We can do it before isolate_lru_page because the
1756 * page can't be freed from under us. NOTE: PG_lock
1757 * is needed to serialize against split_huge_page
1758 * when invoked from the VM.
1760 if (!trylock_page(page)) {
1761 release_pte_pages(pte, _pte);
1765 * Isolate the page to avoid collapsing an hugepage
1766 * currently in use by the VM.
1768 if (isolate_lru_page(page)) {
1770 release_pte_pages(pte, _pte);
1773 /* 0 stands for page_is_file_cache(page) == false */
1774 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1775 VM_BUG_ON(!PageLocked(page));
1776 VM_BUG_ON(PageLRU(page));
1778 /* If there is no mapped pte young don't collapse the page */
1779 if (pte_young(pteval) || PageReferenced(page) ||
1780 mmu_notifier_test_young(vma->vm_mm, address))
1783 if (unlikely(!referenced))
1784 release_all_pte_pages(pte);
1791 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1792 struct vm_area_struct *vma,
1793 unsigned long address,
1797 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1798 pte_t pteval = *_pte;
1799 struct page *src_page;
1801 if (pte_none(pteval)) {
1802 clear_user_highpage(page, address);
1803 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1805 src_page = pte_page(pteval);
1806 copy_user_highpage(page, src_page, address, vma);
1807 VM_BUG_ON(page_mapcount(src_page) != 1);
1808 release_pte_page(src_page);
1810 * ptl mostly unnecessary, but preempt has to
1811 * be disabled to update the per-cpu stats
1812 * inside page_remove_rmap().
1816 * paravirt calls inside pte_clear here are
1819 pte_clear(vma->vm_mm, address, _pte);
1820 page_remove_rmap(src_page);
1822 free_page_and_swap_cache(src_page);
1825 address += PAGE_SIZE;
1830 static void khugepaged_alloc_sleep(void)
1832 wait_event_freezable_timeout(khugepaged_wait, false,
1833 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
1837 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
1839 if (IS_ERR(*hpage)) {
1844 khugepaged_alloc_sleep();
1845 } else if (*hpage) {
1854 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
1855 struct vm_area_struct *vma, unsigned long address,
1860 * Allocate the page while the vma is still valid and under
1861 * the mmap_sem read mode so there is no memory allocation
1862 * later when we take the mmap_sem in write mode. This is more
1863 * friendly behavior (OTOH it may actually hide bugs) to
1864 * filesystems in userland with daemons allocating memory in
1865 * the userland I/O paths. Allocating memory with the
1866 * mmap_sem in read mode is good idea also to allow greater
1869 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1870 node, __GFP_OTHER_NODE);
1873 * After allocating the hugepage, release the mmap_sem read lock in
1874 * preparation for taking it in write mode.
1876 up_read(&mm->mmap_sem);
1877 if (unlikely(!*hpage)) {
1878 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1879 *hpage = ERR_PTR(-ENOMEM);
1883 count_vm_event(THP_COLLAPSE_ALLOC);
1887 static struct page *khugepaged_alloc_hugepage(bool *wait)
1892 hpage = alloc_hugepage(khugepaged_defrag());
1894 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1899 khugepaged_alloc_sleep();
1901 count_vm_event(THP_COLLAPSE_ALLOC);
1902 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
1907 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
1910 *hpage = khugepaged_alloc_hugepage(wait);
1912 if (unlikely(!*hpage))
1919 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
1920 struct vm_area_struct *vma, unsigned long address,
1923 up_read(&mm->mmap_sem);
1929 static void collapse_huge_page(struct mm_struct *mm,
1930 unsigned long address,
1931 struct page **hpage,
1932 struct vm_area_struct *vma,
1940 struct page *new_page;
1943 unsigned long hstart, hend;
1945 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1947 /* release the mmap_sem read lock. */
1948 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
1952 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
1956 * Prevent all access to pagetables with the exception of
1957 * gup_fast later hanlded by the ptep_clear_flush and the VM
1958 * handled by the anon_vma lock + PG_lock.
1960 down_write(&mm->mmap_sem);
1961 if (unlikely(khugepaged_test_exit(mm)))
1964 vma = find_vma(mm, address);
1965 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1966 hend = vma->vm_end & HPAGE_PMD_MASK;
1967 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1970 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1971 (vma->vm_flags & VM_NOHUGEPAGE))
1974 if (!vma->anon_vma || vma->vm_ops)
1976 if (is_vma_temporary_stack(vma))
1978 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1980 pgd = pgd_offset(mm, address);
1981 if (!pgd_present(*pgd))
1984 pud = pud_offset(pgd, address);
1985 if (!pud_present(*pud))
1988 pmd = pmd_offset(pud, address);
1989 /* pmd can't go away or become huge under us */
1990 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1993 anon_vma_lock(vma->anon_vma);
1995 pte = pte_offset_map(pmd, address);
1996 ptl = pte_lockptr(mm, pmd);
1998 spin_lock(&mm->page_table_lock); /* probably unnecessary */
2000 * After this gup_fast can't run anymore. This also removes
2001 * any huge TLB entry from the CPU so we won't allow
2002 * huge and small TLB entries for the same virtual address
2003 * to avoid the risk of CPU bugs in that area.
2005 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
2006 spin_unlock(&mm->page_table_lock);
2009 isolated = __collapse_huge_page_isolate(vma, address, pte);
2012 if (unlikely(!isolated)) {
2014 spin_lock(&mm->page_table_lock);
2015 BUG_ON(!pmd_none(*pmd));
2016 set_pmd_at(mm, address, pmd, _pmd);
2017 spin_unlock(&mm->page_table_lock);
2018 anon_vma_unlock(vma->anon_vma);
2023 * All pages are isolated and locked so anon_vma rmap
2024 * can't run anymore.
2026 anon_vma_unlock(vma->anon_vma);
2028 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2030 __SetPageUptodate(new_page);
2031 pgtable = pmd_pgtable(_pmd);
2032 VM_BUG_ON(page_count(pgtable) != 1);
2033 VM_BUG_ON(page_mapcount(pgtable) != 0);
2035 _pmd = mk_pmd(new_page, vma->vm_page_prot);
2036 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2037 _pmd = pmd_mkhuge(_pmd);
2040 * spin_lock() below is not the equivalent of smp_wmb(), so
2041 * this is needed to avoid the copy_huge_page writes to become
2042 * visible after the set_pmd_at() write.
2046 spin_lock(&mm->page_table_lock);
2047 BUG_ON(!pmd_none(*pmd));
2048 page_add_new_anon_rmap(new_page, vma, address);
2049 set_pmd_at(mm, address, pmd, _pmd);
2050 update_mmu_cache(vma, address, _pmd);
2051 prepare_pmd_huge_pte(pgtable, mm);
2052 spin_unlock(&mm->page_table_lock);
2056 khugepaged_pages_collapsed++;
2058 up_write(&mm->mmap_sem);
2062 mem_cgroup_uncharge_page(new_page);
2066 static int khugepaged_scan_pmd(struct mm_struct *mm,
2067 struct vm_area_struct *vma,
2068 unsigned long address,
2069 struct page **hpage)
2075 int ret = 0, referenced = 0, none = 0;
2077 unsigned long _address;
2081 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2083 pgd = pgd_offset(mm, address);
2084 if (!pgd_present(*pgd))
2087 pud = pud_offset(pgd, address);
2088 if (!pud_present(*pud))
2091 pmd = pmd_offset(pud, address);
2092 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
2095 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2096 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2097 _pte++, _address += PAGE_SIZE) {
2098 pte_t pteval = *_pte;
2099 if (pte_none(pteval)) {
2100 if (++none <= khugepaged_max_ptes_none)
2105 if (!pte_present(pteval) || !pte_write(pteval))
2107 page = vm_normal_page(vma, _address, pteval);
2108 if (unlikely(!page))
2111 * Chose the node of the first page. This could
2112 * be more sophisticated and look at more pages,
2113 * but isn't for now.
2116 node = page_to_nid(page);
2117 VM_BUG_ON(PageCompound(page));
2118 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2120 /* cannot use mapcount: can't collapse if there's a gup pin */
2121 if (page_count(page) != 1)
2123 if (pte_young(pteval) || PageReferenced(page) ||
2124 mmu_notifier_test_young(vma->vm_mm, address))
2130 pte_unmap_unlock(pte, ptl);
2132 /* collapse_huge_page will return with the mmap_sem released */
2133 collapse_huge_page(mm, address, hpage, vma, node);
2138 static void collect_mm_slot(struct mm_slot *mm_slot)
2140 struct mm_struct *mm = mm_slot->mm;
2142 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2144 if (khugepaged_test_exit(mm)) {
2146 hlist_del(&mm_slot->hash);
2147 list_del(&mm_slot->mm_node);
2150 * Not strictly needed because the mm exited already.
2152 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2155 /* khugepaged_mm_lock actually not necessary for the below */
2156 free_mm_slot(mm_slot);
2161 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2162 struct page **hpage)
2163 __releases(&khugepaged_mm_lock)
2164 __acquires(&khugepaged_mm_lock)
2166 struct mm_slot *mm_slot;
2167 struct mm_struct *mm;
2168 struct vm_area_struct *vma;
2172 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2174 if (khugepaged_scan.mm_slot)
2175 mm_slot = khugepaged_scan.mm_slot;
2177 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2178 struct mm_slot, mm_node);
2179 khugepaged_scan.address = 0;
2180 khugepaged_scan.mm_slot = mm_slot;
2182 spin_unlock(&khugepaged_mm_lock);
2185 down_read(&mm->mmap_sem);
2186 if (unlikely(khugepaged_test_exit(mm)))
2189 vma = find_vma(mm, khugepaged_scan.address);
2192 for (; vma; vma = vma->vm_next) {
2193 unsigned long hstart, hend;
2196 if (unlikely(khugepaged_test_exit(mm))) {
2201 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2202 !khugepaged_always()) ||
2203 (vma->vm_flags & VM_NOHUGEPAGE)) {
2208 if (!vma->anon_vma || vma->vm_ops)
2210 if (is_vma_temporary_stack(vma))
2212 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2214 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2215 hend = vma->vm_end & HPAGE_PMD_MASK;
2218 if (khugepaged_scan.address > hend)
2220 if (khugepaged_scan.address < hstart)
2221 khugepaged_scan.address = hstart;
2222 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2224 while (khugepaged_scan.address < hend) {
2227 if (unlikely(khugepaged_test_exit(mm)))
2228 goto breakouterloop;
2230 VM_BUG_ON(khugepaged_scan.address < hstart ||
2231 khugepaged_scan.address + HPAGE_PMD_SIZE >
2233 ret = khugepaged_scan_pmd(mm, vma,
2234 khugepaged_scan.address,
2236 /* move to next address */
2237 khugepaged_scan.address += HPAGE_PMD_SIZE;
2238 progress += HPAGE_PMD_NR;
2240 /* we released mmap_sem so break loop */
2241 goto breakouterloop_mmap_sem;
2242 if (progress >= pages)
2243 goto breakouterloop;
2247 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2248 breakouterloop_mmap_sem:
2250 spin_lock(&khugepaged_mm_lock);
2251 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2253 * Release the current mm_slot if this mm is about to die, or
2254 * if we scanned all vmas of this mm.
2256 if (khugepaged_test_exit(mm) || !vma) {
2258 * Make sure that if mm_users is reaching zero while
2259 * khugepaged runs here, khugepaged_exit will find
2260 * mm_slot not pointing to the exiting mm.
2262 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2263 khugepaged_scan.mm_slot = list_entry(
2264 mm_slot->mm_node.next,
2265 struct mm_slot, mm_node);
2266 khugepaged_scan.address = 0;
2268 khugepaged_scan.mm_slot = NULL;
2269 khugepaged_full_scans++;
2272 collect_mm_slot(mm_slot);
2278 static int khugepaged_has_work(void)
2280 return !list_empty(&khugepaged_scan.mm_head) &&
2281 khugepaged_enabled();
2284 static int khugepaged_wait_event(void)
2286 return !list_empty(&khugepaged_scan.mm_head) ||
2287 kthread_should_stop();
2290 static void khugepaged_do_scan(void)
2292 struct page *hpage = NULL;
2293 unsigned int progress = 0, pass_through_head = 0;
2294 unsigned int pages = khugepaged_pages_to_scan;
2297 barrier(); /* write khugepaged_pages_to_scan to local stack */
2299 while (progress < pages) {
2300 if (!khugepaged_prealloc_page(&hpage, &wait))
2305 if (unlikely(kthread_should_stop() || freezing(current)))
2308 spin_lock(&khugepaged_mm_lock);
2309 if (!khugepaged_scan.mm_slot)
2310 pass_through_head++;
2311 if (khugepaged_has_work() &&
2312 pass_through_head < 2)
2313 progress += khugepaged_scan_mm_slot(pages - progress,
2317 spin_unlock(&khugepaged_mm_lock);
2320 if (!IS_ERR_OR_NULL(hpage))
2324 static void khugepaged_wait_work(void)
2328 if (khugepaged_has_work()) {
2329 if (!khugepaged_scan_sleep_millisecs)
2332 wait_event_freezable_timeout(khugepaged_wait,
2333 kthread_should_stop(),
2334 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2338 if (khugepaged_enabled())
2339 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2342 static void khugepaged_loop(void)
2344 while (likely(khugepaged_enabled())) {
2345 khugepaged_do_scan();
2346 khugepaged_wait_work();
2350 static int khugepaged(void *none)
2352 struct mm_slot *mm_slot;
2355 set_user_nice(current, 19);
2357 while (!kthread_should_stop())
2360 spin_lock(&khugepaged_mm_lock);
2361 mm_slot = khugepaged_scan.mm_slot;
2362 khugepaged_scan.mm_slot = NULL;
2364 collect_mm_slot(mm_slot);
2365 spin_unlock(&khugepaged_mm_lock);
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);