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>
20 #include <linux/pagemap.h>
22 #include <asm/pgalloc.h>
26 * By default transparent hugepage support is enabled for all mappings
27 * and khugepaged scans all mappings. Defrag is only invoked by
28 * khugepaged hugepage allocations and by page faults inside
29 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
32 unsigned long transparent_hugepage_flags __read_mostly =
33 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
34 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
36 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
37 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
40 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
42 /* default scan 8*512 pte (or vmas) every 30 second */
43 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
44 static unsigned int khugepaged_pages_collapsed;
45 static unsigned int khugepaged_full_scans;
46 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
47 /* during fragmentation poll the hugepage allocator once every minute */
48 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
49 static struct task_struct *khugepaged_thread __read_mostly;
50 static unsigned long huge_zero_pfn __read_mostly;
51 static DEFINE_MUTEX(khugepaged_mutex);
52 static DEFINE_SPINLOCK(khugepaged_mm_lock);
53 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
55 * default collapse hugepages if there is at least one pte mapped like
56 * it would have happened if the vma was large enough during page
59 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
61 static int khugepaged(void *none);
62 static int mm_slots_hash_init(void);
63 static int khugepaged_slab_init(void);
64 static void khugepaged_slab_free(void);
66 #define MM_SLOTS_HASH_HEADS 1024
67 static struct hlist_head *mm_slots_hash __read_mostly;
68 static struct kmem_cache *mm_slot_cache __read_mostly;
71 * struct mm_slot - hash lookup from mm to mm_slot
72 * @hash: hash collision list
73 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
74 * @mm: the mm that this information is valid for
77 struct hlist_node hash;
78 struct list_head mm_node;
83 * struct khugepaged_scan - cursor for scanning
84 * @mm_head: the head of the mm list to scan
85 * @mm_slot: the current mm_slot we are scanning
86 * @address: the next address inside that to be scanned
88 * There is only the one khugepaged_scan instance of this cursor structure.
90 struct khugepaged_scan {
91 struct list_head mm_head;
92 struct mm_slot *mm_slot;
93 unsigned long address;
95 static struct khugepaged_scan khugepaged_scan = {
96 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
100 static int set_recommended_min_free_kbytes(void)
104 unsigned long recommended_min;
105 extern int min_free_kbytes;
107 if (!khugepaged_enabled())
110 for_each_populated_zone(zone)
113 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
114 recommended_min = pageblock_nr_pages * nr_zones * 2;
117 * Make sure that on average at least two pageblocks are almost free
118 * of another type, one for a migratetype to fall back to and a
119 * second to avoid subsequent fallbacks of other types There are 3
120 * MIGRATE_TYPES we care about.
122 recommended_min += pageblock_nr_pages * nr_zones *
123 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
125 /* don't ever allow to reserve more than 5% of the lowmem */
126 recommended_min = min(recommended_min,
127 (unsigned long) nr_free_buffer_pages() / 20);
128 recommended_min <<= (PAGE_SHIFT-10);
130 if (recommended_min > min_free_kbytes)
131 min_free_kbytes = recommended_min;
132 setup_per_zone_wmarks();
135 late_initcall(set_recommended_min_free_kbytes);
137 static int start_khugepaged(void)
140 if (khugepaged_enabled()) {
141 if (!khugepaged_thread)
142 khugepaged_thread = kthread_run(khugepaged, NULL,
144 if (unlikely(IS_ERR(khugepaged_thread))) {
146 "khugepaged: kthread_run(khugepaged) failed\n");
147 err = PTR_ERR(khugepaged_thread);
148 khugepaged_thread = NULL;
151 if (!list_empty(&khugepaged_scan.mm_head))
152 wake_up_interruptible(&khugepaged_wait);
154 set_recommended_min_free_kbytes();
155 } else if (khugepaged_thread) {
156 kthread_stop(khugepaged_thread);
157 khugepaged_thread = NULL;
163 static int __init init_huge_zero_page(void)
167 hpage = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
172 huge_zero_pfn = page_to_pfn(hpage);
176 static inline bool is_huge_zero_pfn(unsigned long pfn)
178 return pfn == huge_zero_pfn;
181 static inline bool is_huge_zero_pmd(pmd_t pmd)
183 return is_huge_zero_pfn(pmd_pfn(pmd));
188 static ssize_t double_flag_show(struct kobject *kobj,
189 struct kobj_attribute *attr, char *buf,
190 enum transparent_hugepage_flag enabled,
191 enum transparent_hugepage_flag req_madv)
193 if (test_bit(enabled, &transparent_hugepage_flags)) {
194 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
195 return sprintf(buf, "[always] madvise never\n");
196 } else if (test_bit(req_madv, &transparent_hugepage_flags))
197 return sprintf(buf, "always [madvise] never\n");
199 return sprintf(buf, "always madvise [never]\n");
201 static ssize_t double_flag_store(struct kobject *kobj,
202 struct kobj_attribute *attr,
203 const char *buf, size_t count,
204 enum transparent_hugepage_flag enabled,
205 enum transparent_hugepage_flag req_madv)
207 if (!memcmp("always", buf,
208 min(sizeof("always")-1, count))) {
209 set_bit(enabled, &transparent_hugepage_flags);
210 clear_bit(req_madv, &transparent_hugepage_flags);
211 } else if (!memcmp("madvise", buf,
212 min(sizeof("madvise")-1, count))) {
213 clear_bit(enabled, &transparent_hugepage_flags);
214 set_bit(req_madv, &transparent_hugepage_flags);
215 } else if (!memcmp("never", buf,
216 min(sizeof("never")-1, count))) {
217 clear_bit(enabled, &transparent_hugepage_flags);
218 clear_bit(req_madv, &transparent_hugepage_flags);
225 static ssize_t enabled_show(struct kobject *kobj,
226 struct kobj_attribute *attr, char *buf)
228 return double_flag_show(kobj, attr, buf,
229 TRANSPARENT_HUGEPAGE_FLAG,
230 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
232 static ssize_t enabled_store(struct kobject *kobj,
233 struct kobj_attribute *attr,
234 const char *buf, size_t count)
238 ret = double_flag_store(kobj, attr, buf, count,
239 TRANSPARENT_HUGEPAGE_FLAG,
240 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
245 mutex_lock(&khugepaged_mutex);
246 err = start_khugepaged();
247 mutex_unlock(&khugepaged_mutex);
255 static struct kobj_attribute enabled_attr =
256 __ATTR(enabled, 0644, enabled_show, enabled_store);
258 static ssize_t single_flag_show(struct kobject *kobj,
259 struct kobj_attribute *attr, char *buf,
260 enum transparent_hugepage_flag flag)
262 return sprintf(buf, "%d\n",
263 !!test_bit(flag, &transparent_hugepage_flags));
266 static ssize_t single_flag_store(struct kobject *kobj,
267 struct kobj_attribute *attr,
268 const char *buf, size_t count,
269 enum transparent_hugepage_flag flag)
274 ret = kstrtoul(buf, 10, &value);
281 set_bit(flag, &transparent_hugepage_flags);
283 clear_bit(flag, &transparent_hugepage_flags);
289 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
290 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
291 * memory just to allocate one more hugepage.
293 static ssize_t defrag_show(struct kobject *kobj,
294 struct kobj_attribute *attr, char *buf)
296 return double_flag_show(kobj, attr, buf,
297 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
298 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
300 static ssize_t defrag_store(struct kobject *kobj,
301 struct kobj_attribute *attr,
302 const char *buf, size_t count)
304 return double_flag_store(kobj, attr, buf, count,
305 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
306 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
308 static struct kobj_attribute defrag_attr =
309 __ATTR(defrag, 0644, defrag_show, defrag_store);
311 #ifdef CONFIG_DEBUG_VM
312 static ssize_t debug_cow_show(struct kobject *kobj,
313 struct kobj_attribute *attr, char *buf)
315 return single_flag_show(kobj, attr, buf,
316 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
318 static ssize_t debug_cow_store(struct kobject *kobj,
319 struct kobj_attribute *attr,
320 const char *buf, size_t count)
322 return single_flag_store(kobj, attr, buf, count,
323 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
325 static struct kobj_attribute debug_cow_attr =
326 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
327 #endif /* CONFIG_DEBUG_VM */
329 static struct attribute *hugepage_attr[] = {
332 #ifdef CONFIG_DEBUG_VM
333 &debug_cow_attr.attr,
338 static struct attribute_group hugepage_attr_group = {
339 .attrs = hugepage_attr,
342 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
343 struct kobj_attribute *attr,
346 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
349 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
350 struct kobj_attribute *attr,
351 const char *buf, size_t count)
356 err = strict_strtoul(buf, 10, &msecs);
357 if (err || msecs > UINT_MAX)
360 khugepaged_scan_sleep_millisecs = msecs;
361 wake_up_interruptible(&khugepaged_wait);
365 static struct kobj_attribute scan_sleep_millisecs_attr =
366 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
367 scan_sleep_millisecs_store);
369 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
370 struct kobj_attribute *attr,
373 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
376 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
377 struct kobj_attribute *attr,
378 const char *buf, size_t count)
383 err = strict_strtoul(buf, 10, &msecs);
384 if (err || msecs > UINT_MAX)
387 khugepaged_alloc_sleep_millisecs = msecs;
388 wake_up_interruptible(&khugepaged_wait);
392 static struct kobj_attribute alloc_sleep_millisecs_attr =
393 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
394 alloc_sleep_millisecs_store);
396 static ssize_t pages_to_scan_show(struct kobject *kobj,
397 struct kobj_attribute *attr,
400 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
402 static ssize_t pages_to_scan_store(struct kobject *kobj,
403 struct kobj_attribute *attr,
404 const char *buf, size_t count)
409 err = strict_strtoul(buf, 10, &pages);
410 if (err || !pages || pages > UINT_MAX)
413 khugepaged_pages_to_scan = pages;
417 static struct kobj_attribute pages_to_scan_attr =
418 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
419 pages_to_scan_store);
421 static ssize_t pages_collapsed_show(struct kobject *kobj,
422 struct kobj_attribute *attr,
425 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
427 static struct kobj_attribute pages_collapsed_attr =
428 __ATTR_RO(pages_collapsed);
430 static ssize_t full_scans_show(struct kobject *kobj,
431 struct kobj_attribute *attr,
434 return sprintf(buf, "%u\n", khugepaged_full_scans);
436 static struct kobj_attribute full_scans_attr =
437 __ATTR_RO(full_scans);
439 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
440 struct kobj_attribute *attr, char *buf)
442 return single_flag_show(kobj, attr, buf,
443 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
445 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
446 struct kobj_attribute *attr,
447 const char *buf, size_t count)
449 return single_flag_store(kobj, attr, buf, count,
450 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
452 static struct kobj_attribute khugepaged_defrag_attr =
453 __ATTR(defrag, 0644, khugepaged_defrag_show,
454 khugepaged_defrag_store);
457 * max_ptes_none controls if khugepaged should collapse hugepages over
458 * any unmapped ptes in turn potentially increasing the memory
459 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
460 * reduce the available free memory in the system as it
461 * runs. Increasing max_ptes_none will instead potentially reduce the
462 * free memory in the system during the khugepaged scan.
464 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
465 struct kobj_attribute *attr,
468 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
470 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
471 struct kobj_attribute *attr,
472 const char *buf, size_t count)
475 unsigned long max_ptes_none;
477 err = strict_strtoul(buf, 10, &max_ptes_none);
478 if (err || max_ptes_none > HPAGE_PMD_NR-1)
481 khugepaged_max_ptes_none = max_ptes_none;
485 static struct kobj_attribute khugepaged_max_ptes_none_attr =
486 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
487 khugepaged_max_ptes_none_store);
489 static struct attribute *khugepaged_attr[] = {
490 &khugepaged_defrag_attr.attr,
491 &khugepaged_max_ptes_none_attr.attr,
492 &pages_to_scan_attr.attr,
493 &pages_collapsed_attr.attr,
494 &full_scans_attr.attr,
495 &scan_sleep_millisecs_attr.attr,
496 &alloc_sleep_millisecs_attr.attr,
500 static struct attribute_group khugepaged_attr_group = {
501 .attrs = khugepaged_attr,
502 .name = "khugepaged",
505 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
509 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
510 if (unlikely(!*hugepage_kobj)) {
511 printk(KERN_ERR "hugepage: failed kobject create\n");
515 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
517 printk(KERN_ERR "hugepage: failed register hugeage group\n");
521 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
523 printk(KERN_ERR "hugepage: failed register hugeage group\n");
524 goto remove_hp_group;
530 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
532 kobject_put(*hugepage_kobj);
536 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
538 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
539 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
540 kobject_put(hugepage_kobj);
543 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
548 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
551 #endif /* CONFIG_SYSFS */
553 static int __init hugepage_init(void)
556 struct kobject *hugepage_kobj;
558 if (!has_transparent_hugepage()) {
559 transparent_hugepage_flags = 0;
563 err = hugepage_init_sysfs(&hugepage_kobj);
567 err = init_huge_zero_page();
571 err = khugepaged_slab_init();
575 err = mm_slots_hash_init();
577 khugepaged_slab_free();
582 * By default disable transparent hugepages on smaller systems,
583 * where the extra memory used could hurt more than TLB overhead
584 * is likely to save. The admin can still enable it through /sys.
586 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
587 transparent_hugepage_flags = 0;
594 __free_page(pfn_to_page(huge_zero_pfn));
595 hugepage_exit_sysfs(hugepage_kobj);
598 module_init(hugepage_init)
600 static int __init setup_transparent_hugepage(char *str)
605 if (!strcmp(str, "always")) {
606 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
607 &transparent_hugepage_flags);
608 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
609 &transparent_hugepage_flags);
611 } else if (!strcmp(str, "madvise")) {
612 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
613 &transparent_hugepage_flags);
614 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
615 &transparent_hugepage_flags);
617 } else if (!strcmp(str, "never")) {
618 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
619 &transparent_hugepage_flags);
620 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
621 &transparent_hugepage_flags);
627 "transparent_hugepage= cannot parse, ignored\n");
630 __setup("transparent_hugepage=", setup_transparent_hugepage);
632 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
634 if (likely(vma->vm_flags & VM_WRITE))
635 pmd = pmd_mkwrite(pmd);
639 static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma)
642 entry = mk_pmd(page, vma->vm_page_prot);
643 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
644 entry = pmd_mkhuge(entry);
648 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
649 struct vm_area_struct *vma,
650 unsigned long haddr, pmd_t *pmd,
655 VM_BUG_ON(!PageCompound(page));
656 pgtable = pte_alloc_one(mm, haddr);
657 if (unlikely(!pgtable))
660 clear_huge_page(page, haddr, HPAGE_PMD_NR);
661 __SetPageUptodate(page);
663 spin_lock(&mm->page_table_lock);
664 if (unlikely(!pmd_none(*pmd))) {
665 spin_unlock(&mm->page_table_lock);
666 mem_cgroup_uncharge_page(page);
668 pte_free(mm, pgtable);
671 entry = mk_huge_pmd(page, vma);
673 * The spinlocking to take the lru_lock inside
674 * page_add_new_anon_rmap() acts as a full memory
675 * barrier to be sure clear_huge_page writes become
676 * visible after the set_pmd_at() write.
678 page_add_new_anon_rmap(page, vma, haddr);
679 set_pmd_at(mm, haddr, pmd, entry);
680 pgtable_trans_huge_deposit(mm, pgtable);
681 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
683 spin_unlock(&mm->page_table_lock);
689 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
691 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
694 static inline struct page *alloc_hugepage_vma(int defrag,
695 struct vm_area_struct *vma,
696 unsigned long haddr, int nd,
699 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
700 HPAGE_PMD_ORDER, vma, haddr, nd);
704 static inline struct page *alloc_hugepage(int defrag)
706 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
711 static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
712 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd)
715 entry = pfn_pmd(huge_zero_pfn, vma->vm_page_prot);
716 entry = pmd_wrprotect(entry);
717 entry = pmd_mkhuge(entry);
718 set_pmd_at(mm, haddr, pmd, entry);
719 pgtable_trans_huge_deposit(mm, pgtable);
723 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
724 unsigned long address, pmd_t *pmd,
728 unsigned long haddr = address & HPAGE_PMD_MASK;
731 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
732 if (unlikely(anon_vma_prepare(vma)))
734 if (unlikely(khugepaged_enter(vma)))
736 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
737 vma, haddr, numa_node_id(), 0);
738 if (unlikely(!page)) {
739 count_vm_event(THP_FAULT_FALLBACK);
742 count_vm_event(THP_FAULT_ALLOC);
743 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
747 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
749 mem_cgroup_uncharge_page(page);
758 * Use __pte_alloc instead of pte_alloc_map, because we can't
759 * run pte_offset_map on the pmd, if an huge pmd could
760 * materialize from under us from a different thread.
762 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
764 /* if an huge pmd materialized from under us just retry later */
765 if (unlikely(pmd_trans_huge(*pmd)))
768 * A regular pmd is established and it can't morph into a huge pmd
769 * from under us anymore at this point because we hold the mmap_sem
770 * read mode and khugepaged takes it in write mode. So now it's
771 * safe to run pte_offset_map().
773 pte = pte_offset_map(pmd, address);
774 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
777 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
778 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
779 struct vm_area_struct *vma)
781 struct page *src_page;
787 pgtable = pte_alloc_one(dst_mm, addr);
788 if (unlikely(!pgtable))
791 spin_lock(&dst_mm->page_table_lock);
792 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
796 if (unlikely(!pmd_trans_huge(pmd))) {
797 pte_free(dst_mm, pgtable);
801 * mm->page_table_lock is enough to be sure that huge zero pmd is not
802 * under splitting since we don't split the page itself, only pmd to
805 if (is_huge_zero_pmd(pmd)) {
806 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd);
810 if (unlikely(pmd_trans_splitting(pmd))) {
811 /* split huge page running from under us */
812 spin_unlock(&src_mm->page_table_lock);
813 spin_unlock(&dst_mm->page_table_lock);
814 pte_free(dst_mm, pgtable);
816 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
819 src_page = pmd_page(pmd);
820 VM_BUG_ON(!PageHead(src_page));
822 page_dup_rmap(src_page);
823 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
825 pmdp_set_wrprotect(src_mm, addr, src_pmd);
826 pmd = pmd_mkold(pmd_wrprotect(pmd));
827 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
828 pgtable_trans_huge_deposit(dst_mm, pgtable);
833 spin_unlock(&src_mm->page_table_lock);
834 spin_unlock(&dst_mm->page_table_lock);
839 void huge_pmd_set_accessed(struct mm_struct *mm,
840 struct vm_area_struct *vma,
841 unsigned long address,
842 pmd_t *pmd, pmd_t orig_pmd,
848 spin_lock(&mm->page_table_lock);
849 if (unlikely(!pmd_same(*pmd, orig_pmd)))
852 entry = pmd_mkyoung(orig_pmd);
853 haddr = address & HPAGE_PMD_MASK;
854 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
855 update_mmu_cache_pmd(vma, address, pmd);
858 spin_unlock(&mm->page_table_lock);
861 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
862 struct vm_area_struct *vma, unsigned long address,
863 pmd_t *pmd, unsigned long haddr)
869 unsigned long mmun_start; /* For mmu_notifiers */
870 unsigned long mmun_end; /* For mmu_notifiers */
872 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
878 if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
884 clear_user_highpage(page, address);
885 __SetPageUptodate(page);
888 mmun_end = haddr + HPAGE_PMD_SIZE;
889 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
891 spin_lock(&mm->page_table_lock);
892 pmdp_clear_flush(vma, haddr, pmd);
893 /* leave pmd empty until pte is filled */
895 pgtable = pgtable_trans_huge_withdraw(mm);
896 pmd_populate(mm, &_pmd, pgtable);
898 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
900 if (haddr == (address & PAGE_MASK)) {
901 entry = mk_pte(page, vma->vm_page_prot);
902 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
903 page_add_new_anon_rmap(page, vma, haddr);
905 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
906 entry = pte_mkspecial(entry);
908 pte = pte_offset_map(&_pmd, haddr);
909 VM_BUG_ON(!pte_none(*pte));
910 set_pte_at(mm, haddr, pte, entry);
913 smp_wmb(); /* make pte visible before pmd */
914 pmd_populate(mm, pmd, pgtable);
915 spin_unlock(&mm->page_table_lock);
916 inc_mm_counter(mm, MM_ANONPAGES);
918 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
920 ret |= VM_FAULT_WRITE;
925 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
926 struct vm_area_struct *vma,
927 unsigned long address,
928 pmd_t *pmd, pmd_t orig_pmd,
936 unsigned long mmun_start; /* For mmu_notifiers */
937 unsigned long mmun_end; /* For mmu_notifiers */
939 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
941 if (unlikely(!pages)) {
946 for (i = 0; i < HPAGE_PMD_NR; i++) {
947 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
949 vma, address, page_to_nid(page));
950 if (unlikely(!pages[i] ||
951 mem_cgroup_newpage_charge(pages[i], mm,
955 mem_cgroup_uncharge_start();
957 mem_cgroup_uncharge_page(pages[i]);
960 mem_cgroup_uncharge_end();
967 for (i = 0; i < HPAGE_PMD_NR; i++) {
968 copy_user_highpage(pages[i], page + i,
969 haddr + PAGE_SIZE * i, vma);
970 __SetPageUptodate(pages[i]);
975 mmun_end = haddr + HPAGE_PMD_SIZE;
976 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
978 spin_lock(&mm->page_table_lock);
979 if (unlikely(!pmd_same(*pmd, orig_pmd)))
981 VM_BUG_ON(!PageHead(page));
983 pmdp_clear_flush(vma, haddr, pmd);
984 /* leave pmd empty until pte is filled */
986 pgtable = pgtable_trans_huge_withdraw(mm);
987 pmd_populate(mm, &_pmd, pgtable);
989 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
991 entry = mk_pte(pages[i], vma->vm_page_prot);
992 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
993 page_add_new_anon_rmap(pages[i], vma, haddr);
994 pte = pte_offset_map(&_pmd, haddr);
995 VM_BUG_ON(!pte_none(*pte));
996 set_pte_at(mm, haddr, pte, entry);
1001 smp_wmb(); /* make pte visible before pmd */
1002 pmd_populate(mm, pmd, pgtable);
1003 page_remove_rmap(page);
1004 spin_unlock(&mm->page_table_lock);
1006 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1008 ret |= VM_FAULT_WRITE;
1015 spin_unlock(&mm->page_table_lock);
1016 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1017 mem_cgroup_uncharge_start();
1018 for (i = 0; i < HPAGE_PMD_NR; i++) {
1019 mem_cgroup_uncharge_page(pages[i]);
1022 mem_cgroup_uncharge_end();
1027 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1028 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1031 struct page *page = NULL, *new_page;
1032 unsigned long haddr;
1033 unsigned long mmun_start; /* For mmu_notifiers */
1034 unsigned long mmun_end; /* For mmu_notifiers */
1036 VM_BUG_ON(!vma->anon_vma);
1037 haddr = address & HPAGE_PMD_MASK;
1038 if (is_huge_zero_pmd(orig_pmd))
1040 spin_lock(&mm->page_table_lock);
1041 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1044 page = pmd_page(orig_pmd);
1045 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
1046 if (page_mapcount(page) == 1) {
1048 entry = pmd_mkyoung(orig_pmd);
1049 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1050 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1051 update_mmu_cache_pmd(vma, address, pmd);
1052 ret |= VM_FAULT_WRITE;
1056 spin_unlock(&mm->page_table_lock);
1058 if (transparent_hugepage_enabled(vma) &&
1059 !transparent_hugepage_debug_cow())
1060 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1061 vma, haddr, numa_node_id(), 0);
1065 if (unlikely(!new_page)) {
1066 count_vm_event(THP_FAULT_FALLBACK);
1067 if (is_huge_zero_pmd(orig_pmd)) {
1068 ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1069 address, pmd, haddr);
1071 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1072 pmd, orig_pmd, page, haddr);
1073 if (ret & VM_FAULT_OOM)
1074 split_huge_page(page);
1079 count_vm_event(THP_FAULT_ALLOC);
1081 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1084 split_huge_page(page);
1087 ret |= VM_FAULT_OOM;
1091 if (is_huge_zero_pmd(orig_pmd))
1092 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1094 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1095 __SetPageUptodate(new_page);
1098 mmun_end = haddr + HPAGE_PMD_SIZE;
1099 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1101 spin_lock(&mm->page_table_lock);
1104 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1105 spin_unlock(&mm->page_table_lock);
1106 mem_cgroup_uncharge_page(new_page);
1111 entry = mk_huge_pmd(new_page, vma);
1112 pmdp_clear_flush(vma, haddr, pmd);
1113 page_add_new_anon_rmap(new_page, vma, haddr);
1114 set_pmd_at(mm, haddr, pmd, entry);
1115 update_mmu_cache_pmd(vma, address, pmd);
1116 if (is_huge_zero_pmd(orig_pmd))
1117 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1119 VM_BUG_ON(!PageHead(page));
1120 page_remove_rmap(page);
1123 ret |= VM_FAULT_WRITE;
1125 spin_unlock(&mm->page_table_lock);
1127 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1131 spin_unlock(&mm->page_table_lock);
1135 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1140 struct mm_struct *mm = vma->vm_mm;
1141 struct page *page = NULL;
1143 assert_spin_locked(&mm->page_table_lock);
1145 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1148 page = pmd_page(*pmd);
1149 VM_BUG_ON(!PageHead(page));
1150 if (flags & FOLL_TOUCH) {
1153 * We should set the dirty bit only for FOLL_WRITE but
1154 * for now the dirty bit in the pmd is meaningless.
1155 * And if the dirty bit will become meaningful and
1156 * we'll only set it with FOLL_WRITE, an atomic
1157 * set_bit will be required on the pmd to set the
1158 * young bit, instead of the current set_pmd_at.
1160 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1161 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1163 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1164 if (page->mapping && trylock_page(page)) {
1167 mlock_vma_page(page);
1171 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1172 VM_BUG_ON(!PageCompound(page));
1173 if (flags & FOLL_GET)
1174 get_page_foll(page);
1180 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1181 pmd_t *pmd, unsigned long addr)
1185 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1189 pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1190 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1191 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1192 if (is_huge_zero_pmd(orig_pmd)) {
1194 spin_unlock(&tlb->mm->page_table_lock);
1196 page = pmd_page(orig_pmd);
1197 page_remove_rmap(page);
1198 VM_BUG_ON(page_mapcount(page) < 0);
1199 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1200 VM_BUG_ON(!PageHead(page));
1202 spin_unlock(&tlb->mm->page_table_lock);
1203 tlb_remove_page(tlb, page);
1205 pte_free(tlb->mm, pgtable);
1211 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1212 unsigned long addr, unsigned long end,
1217 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1219 * All logical pages in the range are present
1220 * if backed by a huge page.
1222 spin_unlock(&vma->vm_mm->page_table_lock);
1223 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1230 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1231 unsigned long old_addr,
1232 unsigned long new_addr, unsigned long old_end,
1233 pmd_t *old_pmd, pmd_t *new_pmd)
1238 struct mm_struct *mm = vma->vm_mm;
1240 if ((old_addr & ~HPAGE_PMD_MASK) ||
1241 (new_addr & ~HPAGE_PMD_MASK) ||
1242 old_end - old_addr < HPAGE_PMD_SIZE ||
1243 (new_vma->vm_flags & VM_NOHUGEPAGE))
1247 * The destination pmd shouldn't be established, free_pgtables()
1248 * should have release it.
1250 if (WARN_ON(!pmd_none(*new_pmd))) {
1251 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1255 ret = __pmd_trans_huge_lock(old_pmd, vma);
1257 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1258 VM_BUG_ON(!pmd_none(*new_pmd));
1259 set_pmd_at(mm, new_addr, new_pmd, pmd);
1260 spin_unlock(&mm->page_table_lock);
1266 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1267 unsigned long addr, pgprot_t newprot)
1269 struct mm_struct *mm = vma->vm_mm;
1272 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1274 entry = pmdp_get_and_clear(mm, addr, pmd);
1275 entry = pmd_modify(entry, newprot);
1276 BUG_ON(pmd_write(entry));
1277 set_pmd_at(mm, addr, pmd, entry);
1278 spin_unlock(&vma->vm_mm->page_table_lock);
1286 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1287 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1289 * Note that if it returns 1, this routine returns without unlocking page
1290 * table locks. So callers must unlock them.
1292 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1294 spin_lock(&vma->vm_mm->page_table_lock);
1295 if (likely(pmd_trans_huge(*pmd))) {
1296 if (unlikely(pmd_trans_splitting(*pmd))) {
1297 spin_unlock(&vma->vm_mm->page_table_lock);
1298 wait_split_huge_page(vma->anon_vma, pmd);
1301 /* Thp mapped by 'pmd' is stable, so we can
1302 * handle it as it is. */
1306 spin_unlock(&vma->vm_mm->page_table_lock);
1310 pmd_t *page_check_address_pmd(struct page *page,
1311 struct mm_struct *mm,
1312 unsigned long address,
1313 enum page_check_address_pmd_flag flag)
1315 pmd_t *pmd, *ret = NULL;
1317 if (address & ~HPAGE_PMD_MASK)
1320 pmd = mm_find_pmd(mm, address);
1325 if (pmd_page(*pmd) != page)
1328 * split_vma() may create temporary aliased mappings. There is
1329 * no risk as long as all huge pmd are found and have their
1330 * splitting bit set before __split_huge_page_refcount
1331 * runs. Finding the same huge pmd more than once during the
1332 * same rmap walk is not a problem.
1334 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1335 pmd_trans_splitting(*pmd))
1337 if (pmd_trans_huge(*pmd)) {
1338 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1339 !pmd_trans_splitting(*pmd));
1346 static int __split_huge_page_splitting(struct page *page,
1347 struct vm_area_struct *vma,
1348 unsigned long address)
1350 struct mm_struct *mm = vma->vm_mm;
1353 /* For mmu_notifiers */
1354 const unsigned long mmun_start = address;
1355 const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
1357 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1358 spin_lock(&mm->page_table_lock);
1359 pmd = page_check_address_pmd(page, mm, address,
1360 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1363 * We can't temporarily set the pmd to null in order
1364 * to split it, the pmd must remain marked huge at all
1365 * times or the VM won't take the pmd_trans_huge paths
1366 * and it won't wait on the anon_vma->root->mutex to
1367 * serialize against split_huge_page*.
1369 pmdp_splitting_flush(vma, address, pmd);
1372 spin_unlock(&mm->page_table_lock);
1373 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1378 static void __split_huge_page_refcount(struct page *page)
1381 struct zone *zone = page_zone(page);
1382 struct lruvec *lruvec;
1385 /* prevent PageLRU to go away from under us, and freeze lru stats */
1386 spin_lock_irq(&zone->lru_lock);
1387 lruvec = mem_cgroup_page_lruvec(page, zone);
1389 compound_lock(page);
1390 /* complete memcg works before add pages to LRU */
1391 mem_cgroup_split_huge_fixup(page);
1393 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1394 struct page *page_tail = page + i;
1396 /* tail_page->_mapcount cannot change */
1397 BUG_ON(page_mapcount(page_tail) < 0);
1398 tail_count += page_mapcount(page_tail);
1399 /* check for overflow */
1400 BUG_ON(tail_count < 0);
1401 BUG_ON(atomic_read(&page_tail->_count) != 0);
1403 * tail_page->_count is zero and not changing from
1404 * under us. But get_page_unless_zero() may be running
1405 * from under us on the tail_page. If we used
1406 * atomic_set() below instead of atomic_add(), we
1407 * would then run atomic_set() concurrently with
1408 * get_page_unless_zero(), and atomic_set() is
1409 * implemented in C not using locked ops. spin_unlock
1410 * on x86 sometime uses locked ops because of PPro
1411 * errata 66, 92, so unless somebody can guarantee
1412 * atomic_set() here would be safe on all archs (and
1413 * not only on x86), it's safer to use atomic_add().
1415 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1416 &page_tail->_count);
1418 /* after clearing PageTail the gup refcount can be released */
1422 * retain hwpoison flag of the poisoned tail page:
1423 * fix for the unsuitable process killed on Guest Machine(KVM)
1424 * by the memory-failure.
1426 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1427 page_tail->flags |= (page->flags &
1428 ((1L << PG_referenced) |
1429 (1L << PG_swapbacked) |
1430 (1L << PG_mlocked) |
1431 (1L << PG_uptodate)));
1432 page_tail->flags |= (1L << PG_dirty);
1434 /* clear PageTail before overwriting first_page */
1438 * __split_huge_page_splitting() already set the
1439 * splitting bit in all pmd that could map this
1440 * hugepage, that will ensure no CPU can alter the
1441 * mapcount on the head page. The mapcount is only
1442 * accounted in the head page and it has to be
1443 * transferred to all tail pages in the below code. So
1444 * for this code to be safe, the split the mapcount
1445 * can't change. But that doesn't mean userland can't
1446 * keep changing and reading the page contents while
1447 * we transfer the mapcount, so the pmd splitting
1448 * status is achieved setting a reserved bit in the
1449 * pmd, not by clearing the present bit.
1451 page_tail->_mapcount = page->_mapcount;
1453 BUG_ON(page_tail->mapping);
1454 page_tail->mapping = page->mapping;
1456 page_tail->index = page->index + i;
1458 BUG_ON(!PageAnon(page_tail));
1459 BUG_ON(!PageUptodate(page_tail));
1460 BUG_ON(!PageDirty(page_tail));
1461 BUG_ON(!PageSwapBacked(page_tail));
1463 lru_add_page_tail(page, page_tail, lruvec);
1465 atomic_sub(tail_count, &page->_count);
1466 BUG_ON(atomic_read(&page->_count) <= 0);
1468 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1469 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1471 ClearPageCompound(page);
1472 compound_unlock(page);
1473 spin_unlock_irq(&zone->lru_lock);
1475 for (i = 1; i < HPAGE_PMD_NR; i++) {
1476 struct page *page_tail = page + i;
1477 BUG_ON(page_count(page_tail) <= 0);
1479 * Tail pages may be freed if there wasn't any mapping
1480 * like if add_to_swap() is running on a lru page that
1481 * had its mapping zapped. And freeing these pages
1482 * requires taking the lru_lock so we do the put_page
1483 * of the tail pages after the split is complete.
1485 put_page(page_tail);
1489 * Only the head page (now become a regular page) is required
1490 * to be pinned by the caller.
1492 BUG_ON(page_count(page) <= 0);
1495 static int __split_huge_page_map(struct page *page,
1496 struct vm_area_struct *vma,
1497 unsigned long address)
1499 struct mm_struct *mm = vma->vm_mm;
1503 unsigned long haddr;
1505 spin_lock(&mm->page_table_lock);
1506 pmd = page_check_address_pmd(page, mm, address,
1507 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1509 pgtable = pgtable_trans_huge_withdraw(mm);
1510 pmd_populate(mm, &_pmd, pgtable);
1513 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1515 BUG_ON(PageCompound(page+i));
1516 entry = mk_pte(page + i, vma->vm_page_prot);
1517 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1518 if (!pmd_write(*pmd))
1519 entry = pte_wrprotect(entry);
1521 BUG_ON(page_mapcount(page) != 1);
1522 if (!pmd_young(*pmd))
1523 entry = pte_mkold(entry);
1524 pte = pte_offset_map(&_pmd, haddr);
1525 BUG_ON(!pte_none(*pte));
1526 set_pte_at(mm, haddr, pte, entry);
1530 smp_wmb(); /* make pte visible before pmd */
1532 * Up to this point the pmd is present and huge and
1533 * userland has the whole access to the hugepage
1534 * during the split (which happens in place). If we
1535 * overwrite the pmd with the not-huge version
1536 * pointing to the pte here (which of course we could
1537 * if all CPUs were bug free), userland could trigger
1538 * a small page size TLB miss on the small sized TLB
1539 * while the hugepage TLB entry is still established
1540 * in the huge TLB. Some CPU doesn't like that. See
1541 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1542 * Erratum 383 on page 93. Intel should be safe but is
1543 * also warns that it's only safe if the permission
1544 * and cache attributes of the two entries loaded in
1545 * the two TLB is identical (which should be the case
1546 * here). But it is generally safer to never allow
1547 * small and huge TLB entries for the same virtual
1548 * address to be loaded simultaneously. So instead of
1549 * doing "pmd_populate(); flush_tlb_range();" we first
1550 * mark the current pmd notpresent (atomically because
1551 * here the pmd_trans_huge and pmd_trans_splitting
1552 * must remain set at all times on the pmd until the
1553 * split is complete for this pmd), then we flush the
1554 * SMP TLB and finally we write the non-huge version
1555 * of the pmd entry with pmd_populate.
1557 pmdp_invalidate(vma, address, pmd);
1558 pmd_populate(mm, pmd, pgtable);
1561 spin_unlock(&mm->page_table_lock);
1566 /* must be called with anon_vma->root->mutex hold */
1567 static void __split_huge_page(struct page *page,
1568 struct anon_vma *anon_vma)
1570 int mapcount, mapcount2;
1571 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1572 struct anon_vma_chain *avc;
1574 BUG_ON(!PageHead(page));
1575 BUG_ON(PageTail(page));
1578 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1579 struct vm_area_struct *vma = avc->vma;
1580 unsigned long addr = vma_address(page, vma);
1581 BUG_ON(is_vma_temporary_stack(vma));
1582 mapcount += __split_huge_page_splitting(page, vma, addr);
1585 * It is critical that new vmas are added to the tail of the
1586 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1587 * and establishes a child pmd before
1588 * __split_huge_page_splitting() freezes the parent pmd (so if
1589 * we fail to prevent copy_huge_pmd() from running until the
1590 * whole __split_huge_page() is complete), we will still see
1591 * the newly established pmd of the child later during the
1592 * walk, to be able to set it as pmd_trans_splitting too.
1594 if (mapcount != page_mapcount(page))
1595 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1596 mapcount, page_mapcount(page));
1597 BUG_ON(mapcount != page_mapcount(page));
1599 __split_huge_page_refcount(page);
1602 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1603 struct vm_area_struct *vma = avc->vma;
1604 unsigned long addr = vma_address(page, vma);
1605 BUG_ON(is_vma_temporary_stack(vma));
1606 mapcount2 += __split_huge_page_map(page, vma, addr);
1608 if (mapcount != mapcount2)
1609 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1610 mapcount, mapcount2, page_mapcount(page));
1611 BUG_ON(mapcount != mapcount2);
1614 int split_huge_page(struct page *page)
1616 struct anon_vma *anon_vma;
1619 BUG_ON(!PageAnon(page));
1620 anon_vma = page_lock_anon_vma(page);
1624 if (!PageCompound(page))
1627 BUG_ON(!PageSwapBacked(page));
1628 __split_huge_page(page, anon_vma);
1629 count_vm_event(THP_SPLIT);
1631 BUG_ON(PageCompound(page));
1633 page_unlock_anon_vma(anon_vma);
1638 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1640 int hugepage_madvise(struct vm_area_struct *vma,
1641 unsigned long *vm_flags, int advice)
1643 struct mm_struct *mm = vma->vm_mm;
1648 * Be somewhat over-protective like KSM for now!
1650 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1652 if (mm->def_flags & VM_NOHUGEPAGE)
1654 *vm_flags &= ~VM_NOHUGEPAGE;
1655 *vm_flags |= VM_HUGEPAGE;
1657 * If the vma become good for khugepaged to scan,
1658 * register it here without waiting a page fault that
1659 * may not happen any time soon.
1661 if (unlikely(khugepaged_enter_vma_merge(vma)))
1664 case MADV_NOHUGEPAGE:
1666 * Be somewhat over-protective like KSM for now!
1668 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1670 *vm_flags &= ~VM_HUGEPAGE;
1671 *vm_flags |= VM_NOHUGEPAGE;
1673 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1674 * this vma even if we leave the mm registered in khugepaged if
1675 * it got registered before VM_NOHUGEPAGE was set.
1683 static int __init khugepaged_slab_init(void)
1685 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1686 sizeof(struct mm_slot),
1687 __alignof__(struct mm_slot), 0, NULL);
1694 static void __init khugepaged_slab_free(void)
1696 kmem_cache_destroy(mm_slot_cache);
1697 mm_slot_cache = NULL;
1700 static inline struct mm_slot *alloc_mm_slot(void)
1702 if (!mm_slot_cache) /* initialization failed */
1704 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1707 static inline void free_mm_slot(struct mm_slot *mm_slot)
1709 kmem_cache_free(mm_slot_cache, mm_slot);
1712 static int __init mm_slots_hash_init(void)
1714 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1722 static void __init mm_slots_hash_free(void)
1724 kfree(mm_slots_hash);
1725 mm_slots_hash = NULL;
1729 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1731 struct mm_slot *mm_slot;
1732 struct hlist_head *bucket;
1733 struct hlist_node *node;
1735 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1736 % MM_SLOTS_HASH_HEADS];
1737 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1738 if (mm == mm_slot->mm)
1744 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1745 struct mm_slot *mm_slot)
1747 struct hlist_head *bucket;
1749 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1750 % MM_SLOTS_HASH_HEADS];
1752 hlist_add_head(&mm_slot->hash, bucket);
1755 static inline int khugepaged_test_exit(struct mm_struct *mm)
1757 return atomic_read(&mm->mm_users) == 0;
1760 int __khugepaged_enter(struct mm_struct *mm)
1762 struct mm_slot *mm_slot;
1765 mm_slot = alloc_mm_slot();
1769 /* __khugepaged_exit() must not run from under us */
1770 VM_BUG_ON(khugepaged_test_exit(mm));
1771 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1772 free_mm_slot(mm_slot);
1776 spin_lock(&khugepaged_mm_lock);
1777 insert_to_mm_slots_hash(mm, mm_slot);
1779 * Insert just behind the scanning cursor, to let the area settle
1782 wakeup = list_empty(&khugepaged_scan.mm_head);
1783 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1784 spin_unlock(&khugepaged_mm_lock);
1786 atomic_inc(&mm->mm_count);
1788 wake_up_interruptible(&khugepaged_wait);
1793 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1795 unsigned long hstart, hend;
1798 * Not yet faulted in so we will register later in the
1799 * page fault if needed.
1803 /* khugepaged not yet working on file or special mappings */
1805 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1806 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1807 hend = vma->vm_end & HPAGE_PMD_MASK;
1809 return khugepaged_enter(vma);
1813 void __khugepaged_exit(struct mm_struct *mm)
1815 struct mm_slot *mm_slot;
1818 spin_lock(&khugepaged_mm_lock);
1819 mm_slot = get_mm_slot(mm);
1820 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1821 hlist_del(&mm_slot->hash);
1822 list_del(&mm_slot->mm_node);
1825 spin_unlock(&khugepaged_mm_lock);
1828 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1829 free_mm_slot(mm_slot);
1831 } else if (mm_slot) {
1833 * This is required to serialize against
1834 * khugepaged_test_exit() (which is guaranteed to run
1835 * under mmap sem read mode). Stop here (after we
1836 * return all pagetables will be destroyed) until
1837 * khugepaged has finished working on the pagetables
1838 * under the mmap_sem.
1840 down_write(&mm->mmap_sem);
1841 up_write(&mm->mmap_sem);
1845 static void release_pte_page(struct page *page)
1847 /* 0 stands for page_is_file_cache(page) == false */
1848 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1850 putback_lru_page(page);
1853 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1855 while (--_pte >= pte) {
1856 pte_t pteval = *_pte;
1857 if (!pte_none(pteval))
1858 release_pte_page(pte_page(pteval));
1862 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1863 unsigned long address,
1868 int referenced = 0, none = 0;
1869 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1870 _pte++, address += PAGE_SIZE) {
1871 pte_t pteval = *_pte;
1872 if (pte_none(pteval)) {
1873 if (++none <= khugepaged_max_ptes_none)
1878 if (!pte_present(pteval) || !pte_write(pteval))
1880 page = vm_normal_page(vma, address, pteval);
1881 if (unlikely(!page))
1884 VM_BUG_ON(PageCompound(page));
1885 BUG_ON(!PageAnon(page));
1886 VM_BUG_ON(!PageSwapBacked(page));
1888 /* cannot use mapcount: can't collapse if there's a gup pin */
1889 if (page_count(page) != 1)
1892 * We can do it before isolate_lru_page because the
1893 * page can't be freed from under us. NOTE: PG_lock
1894 * is needed to serialize against split_huge_page
1895 * when invoked from the VM.
1897 if (!trylock_page(page))
1900 * Isolate the page to avoid collapsing an hugepage
1901 * currently in use by the VM.
1903 if (isolate_lru_page(page)) {
1907 /* 0 stands for page_is_file_cache(page) == false */
1908 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1909 VM_BUG_ON(!PageLocked(page));
1910 VM_BUG_ON(PageLRU(page));
1912 /* If there is no mapped pte young don't collapse the page */
1913 if (pte_young(pteval) || PageReferenced(page) ||
1914 mmu_notifier_test_young(vma->vm_mm, address))
1917 if (likely(referenced))
1920 release_pte_pages(pte, _pte);
1924 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1925 struct vm_area_struct *vma,
1926 unsigned long address,
1930 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1931 pte_t pteval = *_pte;
1932 struct page *src_page;
1934 if (pte_none(pteval)) {
1935 clear_user_highpage(page, address);
1936 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1938 src_page = pte_page(pteval);
1939 copy_user_highpage(page, src_page, address, vma);
1940 VM_BUG_ON(page_mapcount(src_page) != 1);
1941 release_pte_page(src_page);
1943 * ptl mostly unnecessary, but preempt has to
1944 * be disabled to update the per-cpu stats
1945 * inside page_remove_rmap().
1949 * paravirt calls inside pte_clear here are
1952 pte_clear(vma->vm_mm, address, _pte);
1953 page_remove_rmap(src_page);
1955 free_page_and_swap_cache(src_page);
1958 address += PAGE_SIZE;
1963 static void khugepaged_alloc_sleep(void)
1965 wait_event_freezable_timeout(khugepaged_wait, false,
1966 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
1970 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
1972 if (IS_ERR(*hpage)) {
1978 khugepaged_alloc_sleep();
1979 } else if (*hpage) {
1988 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
1989 struct vm_area_struct *vma, unsigned long address,
1994 * Allocate the page while the vma is still valid and under
1995 * the mmap_sem read mode so there is no memory allocation
1996 * later when we take the mmap_sem in write mode. This is more
1997 * friendly behavior (OTOH it may actually hide bugs) to
1998 * filesystems in userland with daemons allocating memory in
1999 * the userland I/O paths. Allocating memory with the
2000 * mmap_sem in read mode is good idea also to allow greater
2003 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2004 node, __GFP_OTHER_NODE);
2007 * After allocating the hugepage, release the mmap_sem read lock in
2008 * preparation for taking it in write mode.
2010 up_read(&mm->mmap_sem);
2011 if (unlikely(!*hpage)) {
2012 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2013 *hpage = ERR_PTR(-ENOMEM);
2017 count_vm_event(THP_COLLAPSE_ALLOC);
2021 static struct page *khugepaged_alloc_hugepage(bool *wait)
2026 hpage = alloc_hugepage(khugepaged_defrag());
2028 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2033 khugepaged_alloc_sleep();
2035 count_vm_event(THP_COLLAPSE_ALLOC);
2036 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2041 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2044 *hpage = khugepaged_alloc_hugepage(wait);
2046 if (unlikely(!*hpage))
2053 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2054 struct vm_area_struct *vma, unsigned long address,
2057 up_read(&mm->mmap_sem);
2063 static bool hugepage_vma_check(struct vm_area_struct *vma)
2065 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2066 (vma->vm_flags & VM_NOHUGEPAGE))
2069 if (!vma->anon_vma || vma->vm_ops)
2071 if (is_vma_temporary_stack(vma))
2073 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2077 static void collapse_huge_page(struct mm_struct *mm,
2078 unsigned long address,
2079 struct page **hpage,
2080 struct vm_area_struct *vma,
2086 struct page *new_page;
2089 unsigned long hstart, hend;
2090 unsigned long mmun_start; /* For mmu_notifiers */
2091 unsigned long mmun_end; /* For mmu_notifiers */
2093 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2095 /* release the mmap_sem read lock. */
2096 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2100 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2104 * Prevent all access to pagetables with the exception of
2105 * gup_fast later hanlded by the ptep_clear_flush and the VM
2106 * handled by the anon_vma lock + PG_lock.
2108 down_write(&mm->mmap_sem);
2109 if (unlikely(khugepaged_test_exit(mm)))
2112 vma = find_vma(mm, address);
2113 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2114 hend = vma->vm_end & HPAGE_PMD_MASK;
2115 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2117 if (!hugepage_vma_check(vma))
2119 pmd = mm_find_pmd(mm, address);
2122 if (pmd_trans_huge(*pmd))
2125 anon_vma_lock(vma->anon_vma);
2127 pte = pte_offset_map(pmd, address);
2128 ptl = pte_lockptr(mm, pmd);
2130 mmun_start = address;
2131 mmun_end = address + HPAGE_PMD_SIZE;
2132 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2133 spin_lock(&mm->page_table_lock); /* probably unnecessary */
2135 * After this gup_fast can't run anymore. This also removes
2136 * any huge TLB entry from the CPU so we won't allow
2137 * huge and small TLB entries for the same virtual address
2138 * to avoid the risk of CPU bugs in that area.
2140 _pmd = pmdp_clear_flush(vma, address, pmd);
2141 spin_unlock(&mm->page_table_lock);
2142 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2145 isolated = __collapse_huge_page_isolate(vma, address, pte);
2148 if (unlikely(!isolated)) {
2150 spin_lock(&mm->page_table_lock);
2151 BUG_ON(!pmd_none(*pmd));
2152 set_pmd_at(mm, address, pmd, _pmd);
2153 spin_unlock(&mm->page_table_lock);
2154 anon_vma_unlock(vma->anon_vma);
2159 * All pages are isolated and locked so anon_vma rmap
2160 * can't run anymore.
2162 anon_vma_unlock(vma->anon_vma);
2164 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2166 __SetPageUptodate(new_page);
2167 pgtable = pmd_pgtable(_pmd);
2169 _pmd = mk_huge_pmd(new_page, vma);
2172 * spin_lock() below is not the equivalent of smp_wmb(), so
2173 * this is needed to avoid the copy_huge_page writes to become
2174 * visible after the set_pmd_at() write.
2178 spin_lock(&mm->page_table_lock);
2179 BUG_ON(!pmd_none(*pmd));
2180 page_add_new_anon_rmap(new_page, vma, address);
2181 set_pmd_at(mm, address, pmd, _pmd);
2182 update_mmu_cache_pmd(vma, address, pmd);
2183 pgtable_trans_huge_deposit(mm, pgtable);
2184 spin_unlock(&mm->page_table_lock);
2188 khugepaged_pages_collapsed++;
2190 up_write(&mm->mmap_sem);
2194 mem_cgroup_uncharge_page(new_page);
2198 static int khugepaged_scan_pmd(struct mm_struct *mm,
2199 struct vm_area_struct *vma,
2200 unsigned long address,
2201 struct page **hpage)
2205 int ret = 0, referenced = 0, none = 0;
2207 unsigned long _address;
2211 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2213 pmd = mm_find_pmd(mm, address);
2216 if (pmd_trans_huge(*pmd))
2219 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2220 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2221 _pte++, _address += PAGE_SIZE) {
2222 pte_t pteval = *_pte;
2223 if (pte_none(pteval)) {
2224 if (++none <= khugepaged_max_ptes_none)
2229 if (!pte_present(pteval) || !pte_write(pteval))
2231 page = vm_normal_page(vma, _address, pteval);
2232 if (unlikely(!page))
2235 * Chose the node of the first page. This could
2236 * be more sophisticated and look at more pages,
2237 * but isn't for now.
2240 node = page_to_nid(page);
2241 VM_BUG_ON(PageCompound(page));
2242 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2244 /* cannot use mapcount: can't collapse if there's a gup pin */
2245 if (page_count(page) != 1)
2247 if (pte_young(pteval) || PageReferenced(page) ||
2248 mmu_notifier_test_young(vma->vm_mm, address))
2254 pte_unmap_unlock(pte, ptl);
2256 /* collapse_huge_page will return with the mmap_sem released */
2257 collapse_huge_page(mm, address, hpage, vma, node);
2262 static void collect_mm_slot(struct mm_slot *mm_slot)
2264 struct mm_struct *mm = mm_slot->mm;
2266 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2268 if (khugepaged_test_exit(mm)) {
2270 hlist_del(&mm_slot->hash);
2271 list_del(&mm_slot->mm_node);
2274 * Not strictly needed because the mm exited already.
2276 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2279 /* khugepaged_mm_lock actually not necessary for the below */
2280 free_mm_slot(mm_slot);
2285 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2286 struct page **hpage)
2287 __releases(&khugepaged_mm_lock)
2288 __acquires(&khugepaged_mm_lock)
2290 struct mm_slot *mm_slot;
2291 struct mm_struct *mm;
2292 struct vm_area_struct *vma;
2296 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2298 if (khugepaged_scan.mm_slot)
2299 mm_slot = khugepaged_scan.mm_slot;
2301 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2302 struct mm_slot, mm_node);
2303 khugepaged_scan.address = 0;
2304 khugepaged_scan.mm_slot = mm_slot;
2306 spin_unlock(&khugepaged_mm_lock);
2309 down_read(&mm->mmap_sem);
2310 if (unlikely(khugepaged_test_exit(mm)))
2313 vma = find_vma(mm, khugepaged_scan.address);
2316 for (; vma; vma = vma->vm_next) {
2317 unsigned long hstart, hend;
2320 if (unlikely(khugepaged_test_exit(mm))) {
2324 if (!hugepage_vma_check(vma)) {
2329 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2330 hend = vma->vm_end & HPAGE_PMD_MASK;
2333 if (khugepaged_scan.address > hend)
2335 if (khugepaged_scan.address < hstart)
2336 khugepaged_scan.address = hstart;
2337 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2339 while (khugepaged_scan.address < hend) {
2342 if (unlikely(khugepaged_test_exit(mm)))
2343 goto breakouterloop;
2345 VM_BUG_ON(khugepaged_scan.address < hstart ||
2346 khugepaged_scan.address + HPAGE_PMD_SIZE >
2348 ret = khugepaged_scan_pmd(mm, vma,
2349 khugepaged_scan.address,
2351 /* move to next address */
2352 khugepaged_scan.address += HPAGE_PMD_SIZE;
2353 progress += HPAGE_PMD_NR;
2355 /* we released mmap_sem so break loop */
2356 goto breakouterloop_mmap_sem;
2357 if (progress >= pages)
2358 goto breakouterloop;
2362 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2363 breakouterloop_mmap_sem:
2365 spin_lock(&khugepaged_mm_lock);
2366 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2368 * Release the current mm_slot if this mm is about to die, or
2369 * if we scanned all vmas of this mm.
2371 if (khugepaged_test_exit(mm) || !vma) {
2373 * Make sure that if mm_users is reaching zero while
2374 * khugepaged runs here, khugepaged_exit will find
2375 * mm_slot not pointing to the exiting mm.
2377 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2378 khugepaged_scan.mm_slot = list_entry(
2379 mm_slot->mm_node.next,
2380 struct mm_slot, mm_node);
2381 khugepaged_scan.address = 0;
2383 khugepaged_scan.mm_slot = NULL;
2384 khugepaged_full_scans++;
2387 collect_mm_slot(mm_slot);
2393 static int khugepaged_has_work(void)
2395 return !list_empty(&khugepaged_scan.mm_head) &&
2396 khugepaged_enabled();
2399 static int khugepaged_wait_event(void)
2401 return !list_empty(&khugepaged_scan.mm_head) ||
2402 kthread_should_stop();
2405 static void khugepaged_do_scan(void)
2407 struct page *hpage = NULL;
2408 unsigned int progress = 0, pass_through_head = 0;
2409 unsigned int pages = khugepaged_pages_to_scan;
2412 barrier(); /* write khugepaged_pages_to_scan to local stack */
2414 while (progress < pages) {
2415 if (!khugepaged_prealloc_page(&hpage, &wait))
2420 if (unlikely(kthread_should_stop() || freezing(current)))
2423 spin_lock(&khugepaged_mm_lock);
2424 if (!khugepaged_scan.mm_slot)
2425 pass_through_head++;
2426 if (khugepaged_has_work() &&
2427 pass_through_head < 2)
2428 progress += khugepaged_scan_mm_slot(pages - progress,
2432 spin_unlock(&khugepaged_mm_lock);
2435 if (!IS_ERR_OR_NULL(hpage))
2439 static void khugepaged_wait_work(void)
2443 if (khugepaged_has_work()) {
2444 if (!khugepaged_scan_sleep_millisecs)
2447 wait_event_freezable_timeout(khugepaged_wait,
2448 kthread_should_stop(),
2449 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2453 if (khugepaged_enabled())
2454 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2457 static int khugepaged(void *none)
2459 struct mm_slot *mm_slot;
2462 set_user_nice(current, 19);
2464 while (!kthread_should_stop()) {
2465 khugepaged_do_scan();
2466 khugepaged_wait_work();
2469 spin_lock(&khugepaged_mm_lock);
2470 mm_slot = khugepaged_scan.mm_slot;
2471 khugepaged_scan.mm_slot = NULL;
2473 collect_mm_slot(mm_slot);
2474 spin_unlock(&khugepaged_mm_lock);
2478 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2482 spin_lock(&mm->page_table_lock);
2483 if (unlikely(!pmd_trans_huge(*pmd))) {
2484 spin_unlock(&mm->page_table_lock);
2487 page = pmd_page(*pmd);
2488 VM_BUG_ON(!page_count(page));
2490 spin_unlock(&mm->page_table_lock);
2492 split_huge_page(page);
2495 BUG_ON(pmd_trans_huge(*pmd));
2498 static void split_huge_page_address(struct mm_struct *mm,
2499 unsigned long address)
2503 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2505 pmd = mm_find_pmd(mm, address);
2509 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2510 * materialize from under us.
2512 split_huge_page_pmd(mm, pmd);
2515 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2516 unsigned long start,
2521 * If the new start address isn't hpage aligned and it could
2522 * previously contain an hugepage: check if we need to split
2525 if (start & ~HPAGE_PMD_MASK &&
2526 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2527 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2528 split_huge_page_address(vma->vm_mm, start);
2531 * If the new end address isn't hpage aligned and it could
2532 * previously contain an hugepage: check if we need to split
2535 if (end & ~HPAGE_PMD_MASK &&
2536 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2537 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2538 split_huge_page_address(vma->vm_mm, end);
2541 * If we're also updating the vma->vm_next->vm_start, if the new
2542 * vm_next->vm_start isn't page aligned and it could previously
2543 * contain an hugepage: check if we need to split an huge pmd.
2545 if (adjust_next > 0) {
2546 struct vm_area_struct *next = vma->vm_next;
2547 unsigned long nstart = next->vm_start;
2548 nstart += adjust_next << PAGE_SHIFT;
2549 if (nstart & ~HPAGE_PMD_MASK &&
2550 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2551 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2552 split_huge_page_address(next->vm_mm, nstart);