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 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
97 static int set_recommended_min_free_kbytes(void)
101 unsigned long recommended_min;
102 extern int min_free_kbytes;
104 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
105 &transparent_hugepage_flags) &&
106 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
107 &transparent_hugepage_flags))
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()) {
142 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
146 mutex_lock(&khugepaged_mutex);
147 if (!khugepaged_thread)
148 khugepaged_thread = kthread_run(khugepaged, NULL,
150 if (unlikely(IS_ERR(khugepaged_thread))) {
152 "khugepaged: kthread_run(khugepaged) failed\n");
153 err = PTR_ERR(khugepaged_thread);
154 khugepaged_thread = NULL;
156 wakeup = !list_empty(&khugepaged_scan.mm_head);
157 mutex_unlock(&khugepaged_mutex);
159 wake_up_interruptible(&khugepaged_wait);
161 set_recommended_min_free_kbytes();
164 wake_up_interruptible(&khugepaged_wait);
171 static ssize_t double_flag_show(struct kobject *kobj,
172 struct kobj_attribute *attr, char *buf,
173 enum transparent_hugepage_flag enabled,
174 enum transparent_hugepage_flag req_madv)
176 if (test_bit(enabled, &transparent_hugepage_flags)) {
177 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
178 return sprintf(buf, "[always] madvise never\n");
179 } else if (test_bit(req_madv, &transparent_hugepage_flags))
180 return sprintf(buf, "always [madvise] never\n");
182 return sprintf(buf, "always madvise [never]\n");
184 static ssize_t double_flag_store(struct kobject *kobj,
185 struct kobj_attribute *attr,
186 const char *buf, size_t count,
187 enum transparent_hugepage_flag enabled,
188 enum transparent_hugepage_flag req_madv)
190 if (!memcmp("always", buf,
191 min(sizeof("always")-1, count))) {
192 set_bit(enabled, &transparent_hugepage_flags);
193 clear_bit(req_madv, &transparent_hugepage_flags);
194 } else if (!memcmp("madvise", buf,
195 min(sizeof("madvise")-1, count))) {
196 clear_bit(enabled, &transparent_hugepage_flags);
197 set_bit(req_madv, &transparent_hugepage_flags);
198 } else if (!memcmp("never", buf,
199 min(sizeof("never")-1, count))) {
200 clear_bit(enabled, &transparent_hugepage_flags);
201 clear_bit(req_madv, &transparent_hugepage_flags);
208 static ssize_t enabled_show(struct kobject *kobj,
209 struct kobj_attribute *attr, char *buf)
211 return double_flag_show(kobj, attr, buf,
212 TRANSPARENT_HUGEPAGE_FLAG,
213 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
215 static ssize_t enabled_store(struct kobject *kobj,
216 struct kobj_attribute *attr,
217 const char *buf, size_t count)
221 ret = double_flag_store(kobj, attr, buf, count,
222 TRANSPARENT_HUGEPAGE_FLAG,
223 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
226 int err = start_khugepaged();
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",
489 #endif /* CONFIG_SYSFS */
491 static int __init hugepage_init(void)
495 static struct kobject *hugepage_kobj;
499 if (!has_transparent_hugepage()) {
500 transparent_hugepage_flags = 0;
506 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
507 if (unlikely(!hugepage_kobj)) {
508 printk(KERN_ERR "hugepage: failed kobject create\n");
512 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
514 printk(KERN_ERR "hugepage: failed register hugeage group\n");
518 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
520 printk(KERN_ERR "hugepage: failed register hugeage group\n");
525 err = khugepaged_slab_init();
529 err = mm_slots_hash_init();
531 khugepaged_slab_free();
536 * By default disable transparent hugepages on smaller systems,
537 * where the extra memory used could hurt more than TLB overhead
538 * is likely to save. The admin can still enable it through /sys.
540 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
541 transparent_hugepage_flags = 0;
545 set_recommended_min_free_kbytes();
550 module_init(hugepage_init)
552 static int __init setup_transparent_hugepage(char *str)
557 if (!strcmp(str, "always")) {
558 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
559 &transparent_hugepage_flags);
560 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
561 &transparent_hugepage_flags);
563 } else if (!strcmp(str, "madvise")) {
564 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
565 &transparent_hugepage_flags);
566 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
567 &transparent_hugepage_flags);
569 } else if (!strcmp(str, "never")) {
570 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
571 &transparent_hugepage_flags);
572 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
573 &transparent_hugepage_flags);
579 "transparent_hugepage= cannot parse, ignored\n");
582 __setup("transparent_hugepage=", setup_transparent_hugepage);
584 static void prepare_pmd_huge_pte(pgtable_t pgtable,
585 struct mm_struct *mm)
587 assert_spin_locked(&mm->page_table_lock);
590 if (!mm->pmd_huge_pte)
591 INIT_LIST_HEAD(&pgtable->lru);
593 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
594 mm->pmd_huge_pte = pgtable;
597 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
599 if (likely(vma->vm_flags & VM_WRITE))
600 pmd = pmd_mkwrite(pmd);
604 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
605 struct vm_area_struct *vma,
606 unsigned long haddr, pmd_t *pmd,
612 VM_BUG_ON(!PageCompound(page));
613 pgtable = pte_alloc_one(mm, haddr);
614 if (unlikely(!pgtable)) {
615 mem_cgroup_uncharge_page(page);
620 clear_huge_page(page, haddr, HPAGE_PMD_NR);
621 __SetPageUptodate(page);
623 spin_lock(&mm->page_table_lock);
624 if (unlikely(!pmd_none(*pmd))) {
625 spin_unlock(&mm->page_table_lock);
626 mem_cgroup_uncharge_page(page);
628 pte_free(mm, pgtable);
631 entry = mk_pmd(page, vma->vm_page_prot);
632 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
633 entry = pmd_mkhuge(entry);
635 * The spinlocking to take the lru_lock inside
636 * page_add_new_anon_rmap() acts as a full memory
637 * barrier to be sure clear_huge_page writes become
638 * visible after the set_pmd_at() write.
640 page_add_new_anon_rmap(page, vma, haddr);
641 set_pmd_at(mm, haddr, pmd, entry);
642 prepare_pmd_huge_pte(pgtable, mm);
643 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
644 spin_unlock(&mm->page_table_lock);
650 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
652 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
655 static inline struct page *alloc_hugepage_vma(int defrag,
656 struct vm_area_struct *vma,
657 unsigned long haddr, int nd,
660 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
661 HPAGE_PMD_ORDER, vma, haddr, nd);
665 static inline struct page *alloc_hugepage(int defrag)
667 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
672 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
673 unsigned long address, pmd_t *pmd,
677 unsigned long haddr = address & HPAGE_PMD_MASK;
680 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
681 if (unlikely(anon_vma_prepare(vma)))
683 if (unlikely(khugepaged_enter(vma)))
685 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
686 vma, haddr, numa_node_id(), 0);
687 if (unlikely(!page)) {
688 count_vm_event(THP_FAULT_FALLBACK);
691 count_vm_event(THP_FAULT_ALLOC);
692 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
697 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
701 * Use __pte_alloc instead of pte_alloc_map, because we can't
702 * run pte_offset_map on the pmd, if an huge pmd could
703 * materialize from under us from a different thread.
705 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
707 /* if an huge pmd materialized from under us just retry later */
708 if (unlikely(pmd_trans_huge(*pmd)))
711 * A regular pmd is established and it can't morph into a huge pmd
712 * from under us anymore at this point because we hold the mmap_sem
713 * read mode and khugepaged takes it in write mode. So now it's
714 * safe to run pte_offset_map().
716 pte = pte_offset_map(pmd, address);
717 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
720 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
721 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
722 struct vm_area_struct *vma)
724 struct page *src_page;
730 pgtable = pte_alloc_one(dst_mm, addr);
731 if (unlikely(!pgtable))
734 spin_lock(&dst_mm->page_table_lock);
735 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
739 if (unlikely(!pmd_trans_huge(pmd))) {
740 pte_free(dst_mm, pgtable);
743 if (unlikely(pmd_trans_splitting(pmd))) {
744 /* split huge page running from under us */
745 spin_unlock(&src_mm->page_table_lock);
746 spin_unlock(&dst_mm->page_table_lock);
747 pte_free(dst_mm, pgtable);
749 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
752 src_page = pmd_page(pmd);
753 VM_BUG_ON(!PageHead(src_page));
755 page_dup_rmap(src_page);
756 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
758 pmdp_set_wrprotect(src_mm, addr, src_pmd);
759 pmd = pmd_mkold(pmd_wrprotect(pmd));
760 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
761 prepare_pmd_huge_pte(pgtable, dst_mm);
765 spin_unlock(&src_mm->page_table_lock);
766 spin_unlock(&dst_mm->page_table_lock);
771 /* no "address" argument so destroys page coloring of some arch */
772 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
776 assert_spin_locked(&mm->page_table_lock);
779 pgtable = mm->pmd_huge_pte;
780 if (list_empty(&pgtable->lru))
781 mm->pmd_huge_pte = NULL;
783 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
785 list_del(&pgtable->lru);
790 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
791 struct vm_area_struct *vma,
792 unsigned long address,
793 pmd_t *pmd, pmd_t orig_pmd,
802 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
804 if (unlikely(!pages)) {
809 for (i = 0; i < HPAGE_PMD_NR; i++) {
810 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
812 vma, address, page_to_nid(page));
813 if (unlikely(!pages[i] ||
814 mem_cgroup_newpage_charge(pages[i], mm,
818 mem_cgroup_uncharge_start();
820 mem_cgroup_uncharge_page(pages[i]);
823 mem_cgroup_uncharge_end();
830 for (i = 0; i < HPAGE_PMD_NR; i++) {
831 copy_user_highpage(pages[i], page + i,
832 haddr + PAGE_SHIFT*i, vma);
833 __SetPageUptodate(pages[i]);
837 spin_lock(&mm->page_table_lock);
838 if (unlikely(!pmd_same(*pmd, orig_pmd)))
840 VM_BUG_ON(!PageHead(page));
842 pmdp_clear_flush_notify(vma, haddr, pmd);
843 /* leave pmd empty until pte is filled */
845 pgtable = get_pmd_huge_pte(mm);
846 pmd_populate(mm, &_pmd, pgtable);
848 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
850 entry = mk_pte(pages[i], vma->vm_page_prot);
851 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
852 page_add_new_anon_rmap(pages[i], vma, haddr);
853 pte = pte_offset_map(&_pmd, haddr);
854 VM_BUG_ON(!pte_none(*pte));
855 set_pte_at(mm, haddr, pte, entry);
861 smp_wmb(); /* make pte visible before pmd */
862 pmd_populate(mm, pmd, pgtable);
863 page_remove_rmap(page);
864 spin_unlock(&mm->page_table_lock);
866 ret |= VM_FAULT_WRITE;
873 spin_unlock(&mm->page_table_lock);
874 mem_cgroup_uncharge_start();
875 for (i = 0; i < HPAGE_PMD_NR; i++) {
876 mem_cgroup_uncharge_page(pages[i]);
879 mem_cgroup_uncharge_end();
884 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
885 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
888 struct page *page, *new_page;
891 VM_BUG_ON(!vma->anon_vma);
892 spin_lock(&mm->page_table_lock);
893 if (unlikely(!pmd_same(*pmd, orig_pmd)))
896 page = pmd_page(orig_pmd);
897 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
898 haddr = address & HPAGE_PMD_MASK;
899 if (page_mapcount(page) == 1) {
901 entry = pmd_mkyoung(orig_pmd);
902 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
903 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
904 update_mmu_cache(vma, address, entry);
905 ret |= VM_FAULT_WRITE;
909 spin_unlock(&mm->page_table_lock);
911 if (transparent_hugepage_enabled(vma) &&
912 !transparent_hugepage_debug_cow())
913 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
914 vma, haddr, numa_node_id(), 0);
918 if (unlikely(!new_page)) {
919 count_vm_event(THP_FAULT_FALLBACK);
920 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
921 pmd, orig_pmd, page, haddr);
925 count_vm_event(THP_FAULT_ALLOC);
927 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
934 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
935 __SetPageUptodate(new_page);
937 spin_lock(&mm->page_table_lock);
939 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
940 mem_cgroup_uncharge_page(new_page);
944 VM_BUG_ON(!PageHead(page));
945 entry = mk_pmd(new_page, vma->vm_page_prot);
946 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
947 entry = pmd_mkhuge(entry);
948 pmdp_clear_flush_notify(vma, haddr, pmd);
949 page_add_new_anon_rmap(new_page, vma, haddr);
950 set_pmd_at(mm, haddr, pmd, entry);
951 update_mmu_cache(vma, address, entry);
952 page_remove_rmap(page);
954 ret |= VM_FAULT_WRITE;
957 spin_unlock(&mm->page_table_lock);
962 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
967 struct page *page = NULL;
969 assert_spin_locked(&mm->page_table_lock);
971 if (flags & FOLL_WRITE && !pmd_write(*pmd))
974 page = pmd_page(*pmd);
975 VM_BUG_ON(!PageHead(page));
976 if (flags & FOLL_TOUCH) {
979 * We should set the dirty bit only for FOLL_WRITE but
980 * for now the dirty bit in the pmd is meaningless.
981 * And if the dirty bit will become meaningful and
982 * we'll only set it with FOLL_WRITE, an atomic
983 * set_bit will be required on the pmd to set the
984 * young bit, instead of the current set_pmd_at.
986 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
987 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
989 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
990 VM_BUG_ON(!PageCompound(page));
991 if (flags & FOLL_GET)
998 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1003 spin_lock(&tlb->mm->page_table_lock);
1004 if (likely(pmd_trans_huge(*pmd))) {
1005 if (unlikely(pmd_trans_splitting(*pmd))) {
1006 spin_unlock(&tlb->mm->page_table_lock);
1007 wait_split_huge_page(vma->anon_vma,
1012 pgtable = get_pmd_huge_pte(tlb->mm);
1013 page = pmd_page(*pmd);
1015 page_remove_rmap(page);
1016 VM_BUG_ON(page_mapcount(page) < 0);
1017 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1018 VM_BUG_ON(!PageHead(page));
1019 spin_unlock(&tlb->mm->page_table_lock);
1020 tlb_remove_page(tlb, page);
1021 pte_free(tlb->mm, pgtable);
1025 spin_unlock(&tlb->mm->page_table_lock);
1030 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1031 unsigned long addr, unsigned long end,
1036 spin_lock(&vma->vm_mm->page_table_lock);
1037 if (likely(pmd_trans_huge(*pmd))) {
1038 ret = !pmd_trans_splitting(*pmd);
1039 spin_unlock(&vma->vm_mm->page_table_lock);
1041 wait_split_huge_page(vma->anon_vma, pmd);
1044 * All logical pages in the range are present
1045 * if backed by a huge page.
1047 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1050 spin_unlock(&vma->vm_mm->page_table_lock);
1055 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1056 unsigned long addr, pgprot_t newprot)
1058 struct mm_struct *mm = vma->vm_mm;
1061 spin_lock(&mm->page_table_lock);
1062 if (likely(pmd_trans_huge(*pmd))) {
1063 if (unlikely(pmd_trans_splitting(*pmd))) {
1064 spin_unlock(&mm->page_table_lock);
1065 wait_split_huge_page(vma->anon_vma, pmd);
1069 entry = pmdp_get_and_clear(mm, addr, pmd);
1070 entry = pmd_modify(entry, newprot);
1071 set_pmd_at(mm, addr, pmd, entry);
1072 spin_unlock(&vma->vm_mm->page_table_lock);
1073 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1077 spin_unlock(&vma->vm_mm->page_table_lock);
1082 pmd_t *page_check_address_pmd(struct page *page,
1083 struct mm_struct *mm,
1084 unsigned long address,
1085 enum page_check_address_pmd_flag flag)
1089 pmd_t *pmd, *ret = NULL;
1091 if (address & ~HPAGE_PMD_MASK)
1094 pgd = pgd_offset(mm, address);
1095 if (!pgd_present(*pgd))
1098 pud = pud_offset(pgd, address);
1099 if (!pud_present(*pud))
1102 pmd = pmd_offset(pud, address);
1105 if (pmd_page(*pmd) != page)
1108 * split_vma() may create temporary aliased mappings. There is
1109 * no risk as long as all huge pmd are found and have their
1110 * splitting bit set before __split_huge_page_refcount
1111 * runs. Finding the same huge pmd more than once during the
1112 * same rmap walk is not a problem.
1114 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1115 pmd_trans_splitting(*pmd))
1117 if (pmd_trans_huge(*pmd)) {
1118 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1119 !pmd_trans_splitting(*pmd));
1126 static int __split_huge_page_splitting(struct page *page,
1127 struct vm_area_struct *vma,
1128 unsigned long address)
1130 struct mm_struct *mm = vma->vm_mm;
1134 spin_lock(&mm->page_table_lock);
1135 pmd = page_check_address_pmd(page, mm, address,
1136 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1139 * We can't temporarily set the pmd to null in order
1140 * to split it, the pmd must remain marked huge at all
1141 * times or the VM won't take the pmd_trans_huge paths
1142 * and it won't wait on the anon_vma->root->mutex to
1143 * serialize against split_huge_page*.
1145 pmdp_splitting_flush_notify(vma, address, pmd);
1148 spin_unlock(&mm->page_table_lock);
1153 static void __split_huge_page_refcount(struct page *page)
1156 unsigned long head_index = page->index;
1157 struct zone *zone = page_zone(page);
1161 /* prevent PageLRU to go away from under us, and freeze lru stats */
1162 spin_lock_irq(&zone->lru_lock);
1163 compound_lock(page);
1165 for (i = 1; i < HPAGE_PMD_NR; i++) {
1166 struct page *page_tail = page + i;
1168 /* tail_page->_mapcount cannot change */
1169 BUG_ON(page_mapcount(page_tail) < 0);
1170 tail_count += page_mapcount(page_tail);
1171 /* check for overflow */
1172 BUG_ON(tail_count < 0);
1173 BUG_ON(atomic_read(&page_tail->_count) != 0);
1175 * tail_page->_count is zero and not changing from
1176 * under us. But get_page_unless_zero() may be running
1177 * from under us on the tail_page. If we used
1178 * atomic_set() below instead of atomic_add(), we
1179 * would then run atomic_set() concurrently with
1180 * get_page_unless_zero(), and atomic_set() is
1181 * implemented in C not using locked ops. spin_unlock
1182 * on x86 sometime uses locked ops because of PPro
1183 * errata 66, 92, so unless somebody can guarantee
1184 * atomic_set() here would be safe on all archs (and
1185 * not only on x86), it's safer to use atomic_add().
1187 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1188 &page_tail->_count);
1190 /* after clearing PageTail the gup refcount can be released */
1194 * retain hwpoison flag of the poisoned tail page:
1195 * fix for the unsuitable process killed on Guest Machine(KVM)
1196 * by the memory-failure.
1198 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1199 page_tail->flags |= (page->flags &
1200 ((1L << PG_referenced) |
1201 (1L << PG_swapbacked) |
1202 (1L << PG_mlocked) |
1203 (1L << PG_uptodate)));
1204 page_tail->flags |= (1L << PG_dirty);
1206 /* clear PageTail before overwriting first_page */
1210 * __split_huge_page_splitting() already set the
1211 * splitting bit in all pmd that could map this
1212 * hugepage, that will ensure no CPU can alter the
1213 * mapcount on the head page. The mapcount is only
1214 * accounted in the head page and it has to be
1215 * transferred to all tail pages in the below code. So
1216 * for this code to be safe, the split the mapcount
1217 * can't change. But that doesn't mean userland can't
1218 * keep changing and reading the page contents while
1219 * we transfer the mapcount, so the pmd splitting
1220 * status is achieved setting a reserved bit in the
1221 * pmd, not by clearing the present bit.
1223 page_tail->_mapcount = page->_mapcount;
1225 BUG_ON(page_tail->mapping);
1226 page_tail->mapping = page->mapping;
1228 page_tail->index = ++head_index;
1230 BUG_ON(!PageAnon(page_tail));
1231 BUG_ON(!PageUptodate(page_tail));
1232 BUG_ON(!PageDirty(page_tail));
1233 BUG_ON(!PageSwapBacked(page_tail));
1235 mem_cgroup_split_huge_fixup(page, page_tail);
1237 lru_add_page_tail(zone, page, page_tail);
1239 atomic_sub(tail_count, &page->_count);
1240 BUG_ON(atomic_read(&page->_count) <= 0);
1242 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1243 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1246 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1247 * so adjust those appropriately if this page is on the LRU.
1249 if (PageLRU(page)) {
1250 zonestat = NR_LRU_BASE + page_lru(page);
1251 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1254 ClearPageCompound(page);
1255 compound_unlock(page);
1256 spin_unlock_irq(&zone->lru_lock);
1258 for (i = 1; i < HPAGE_PMD_NR; i++) {
1259 struct page *page_tail = page + i;
1260 BUG_ON(page_count(page_tail) <= 0);
1262 * Tail pages may be freed if there wasn't any mapping
1263 * like if add_to_swap() is running on a lru page that
1264 * had its mapping zapped. And freeing these pages
1265 * requires taking the lru_lock so we do the put_page
1266 * of the tail pages after the split is complete.
1268 put_page(page_tail);
1272 * Only the head page (now become a regular page) is required
1273 * to be pinned by the caller.
1275 BUG_ON(page_count(page) <= 0);
1278 static int __split_huge_page_map(struct page *page,
1279 struct vm_area_struct *vma,
1280 unsigned long address)
1282 struct mm_struct *mm = vma->vm_mm;
1286 unsigned long haddr;
1288 spin_lock(&mm->page_table_lock);
1289 pmd = page_check_address_pmd(page, mm, address,
1290 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1292 pgtable = get_pmd_huge_pte(mm);
1293 pmd_populate(mm, &_pmd, pgtable);
1295 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1296 i++, haddr += PAGE_SIZE) {
1298 BUG_ON(PageCompound(page+i));
1299 entry = mk_pte(page + i, vma->vm_page_prot);
1300 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1301 if (!pmd_write(*pmd))
1302 entry = pte_wrprotect(entry);
1304 BUG_ON(page_mapcount(page) != 1);
1305 if (!pmd_young(*pmd))
1306 entry = pte_mkold(entry);
1307 pte = pte_offset_map(&_pmd, haddr);
1308 BUG_ON(!pte_none(*pte));
1309 set_pte_at(mm, haddr, pte, entry);
1314 smp_wmb(); /* make pte visible before pmd */
1316 * Up to this point the pmd is present and huge and
1317 * userland has the whole access to the hugepage
1318 * during the split (which happens in place). If we
1319 * overwrite the pmd with the not-huge version
1320 * pointing to the pte here (which of course we could
1321 * if all CPUs were bug free), userland could trigger
1322 * a small page size TLB miss on the small sized TLB
1323 * while the hugepage TLB entry is still established
1324 * in the huge TLB. Some CPU doesn't like that. See
1325 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1326 * Erratum 383 on page 93. Intel should be safe but is
1327 * also warns that it's only safe if the permission
1328 * and cache attributes of the two entries loaded in
1329 * the two TLB is identical (which should be the case
1330 * here). But it is generally safer to never allow
1331 * small and huge TLB entries for the same virtual
1332 * address to be loaded simultaneously. So instead of
1333 * doing "pmd_populate(); flush_tlb_range();" we first
1334 * mark the current pmd notpresent (atomically because
1335 * here the pmd_trans_huge and pmd_trans_splitting
1336 * must remain set at all times on the pmd until the
1337 * split is complete for this pmd), then we flush the
1338 * SMP TLB and finally we write the non-huge version
1339 * of the pmd entry with pmd_populate.
1341 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1342 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1343 pmd_populate(mm, pmd, pgtable);
1346 spin_unlock(&mm->page_table_lock);
1351 /* must be called with anon_vma->root->mutex hold */
1352 static void __split_huge_page(struct page *page,
1353 struct anon_vma *anon_vma)
1355 int mapcount, mapcount2;
1356 struct anon_vma_chain *avc;
1358 BUG_ON(!PageHead(page));
1359 BUG_ON(PageTail(page));
1362 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1363 struct vm_area_struct *vma = avc->vma;
1364 unsigned long addr = vma_address(page, vma);
1365 BUG_ON(is_vma_temporary_stack(vma));
1366 if (addr == -EFAULT)
1368 mapcount += __split_huge_page_splitting(page, vma, addr);
1371 * It is critical that new vmas are added to the tail of the
1372 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1373 * and establishes a child pmd before
1374 * __split_huge_page_splitting() freezes the parent pmd (so if
1375 * we fail to prevent copy_huge_pmd() from running until the
1376 * whole __split_huge_page() is complete), we will still see
1377 * the newly established pmd of the child later during the
1378 * walk, to be able to set it as pmd_trans_splitting too.
1380 if (mapcount != page_mapcount(page))
1381 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1382 mapcount, page_mapcount(page));
1383 BUG_ON(mapcount != page_mapcount(page));
1385 __split_huge_page_refcount(page);
1388 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1389 struct vm_area_struct *vma = avc->vma;
1390 unsigned long addr = vma_address(page, vma);
1391 BUG_ON(is_vma_temporary_stack(vma));
1392 if (addr == -EFAULT)
1394 mapcount2 += __split_huge_page_map(page, vma, addr);
1396 if (mapcount != mapcount2)
1397 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1398 mapcount, mapcount2, page_mapcount(page));
1399 BUG_ON(mapcount != mapcount2);
1402 int split_huge_page(struct page *page)
1404 struct anon_vma *anon_vma;
1407 BUG_ON(!PageAnon(page));
1408 anon_vma = page_lock_anon_vma(page);
1412 if (!PageCompound(page))
1415 BUG_ON(!PageSwapBacked(page));
1416 __split_huge_page(page, anon_vma);
1417 count_vm_event(THP_SPLIT);
1419 BUG_ON(PageCompound(page));
1421 page_unlock_anon_vma(anon_vma);
1426 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1427 VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1429 int hugepage_madvise(struct vm_area_struct *vma,
1430 unsigned long *vm_flags, int advice)
1435 * Be somewhat over-protective like KSM for now!
1437 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1439 *vm_flags &= ~VM_NOHUGEPAGE;
1440 *vm_flags |= VM_HUGEPAGE;
1442 * If the vma become good for khugepaged to scan,
1443 * register it here without waiting a page fault that
1444 * may not happen any time soon.
1446 if (unlikely(khugepaged_enter_vma_merge(vma)))
1449 case MADV_NOHUGEPAGE:
1451 * Be somewhat over-protective like KSM for now!
1453 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1455 *vm_flags &= ~VM_HUGEPAGE;
1456 *vm_flags |= VM_NOHUGEPAGE;
1458 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1459 * this vma even if we leave the mm registered in khugepaged if
1460 * it got registered before VM_NOHUGEPAGE was set.
1468 static int __init khugepaged_slab_init(void)
1470 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1471 sizeof(struct mm_slot),
1472 __alignof__(struct mm_slot), 0, NULL);
1479 static void __init khugepaged_slab_free(void)
1481 kmem_cache_destroy(mm_slot_cache);
1482 mm_slot_cache = NULL;
1485 static inline struct mm_slot *alloc_mm_slot(void)
1487 if (!mm_slot_cache) /* initialization failed */
1489 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1492 static inline void free_mm_slot(struct mm_slot *mm_slot)
1494 kmem_cache_free(mm_slot_cache, mm_slot);
1497 static int __init mm_slots_hash_init(void)
1499 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1507 static void __init mm_slots_hash_free(void)
1509 kfree(mm_slots_hash);
1510 mm_slots_hash = NULL;
1514 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1516 struct mm_slot *mm_slot;
1517 struct hlist_head *bucket;
1518 struct hlist_node *node;
1520 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1521 % MM_SLOTS_HASH_HEADS];
1522 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1523 if (mm == mm_slot->mm)
1529 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1530 struct mm_slot *mm_slot)
1532 struct hlist_head *bucket;
1534 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1535 % MM_SLOTS_HASH_HEADS];
1537 hlist_add_head(&mm_slot->hash, bucket);
1540 static inline int khugepaged_test_exit(struct mm_struct *mm)
1542 return atomic_read(&mm->mm_users) == 0;
1545 int __khugepaged_enter(struct mm_struct *mm)
1547 struct mm_slot *mm_slot;
1550 mm_slot = alloc_mm_slot();
1554 /* __khugepaged_exit() must not run from under us */
1555 VM_BUG_ON(khugepaged_test_exit(mm));
1556 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1557 free_mm_slot(mm_slot);
1561 spin_lock(&khugepaged_mm_lock);
1562 insert_to_mm_slots_hash(mm, mm_slot);
1564 * Insert just behind the scanning cursor, to let the area settle
1567 wakeup = list_empty(&khugepaged_scan.mm_head);
1568 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1569 spin_unlock(&khugepaged_mm_lock);
1571 atomic_inc(&mm->mm_count);
1573 wake_up_interruptible(&khugepaged_wait);
1578 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1580 unsigned long hstart, hend;
1583 * Not yet faulted in so we will register later in the
1584 * page fault if needed.
1588 /* khugepaged not yet working on file or special mappings */
1591 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1592 * true too, verify it here.
1594 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1595 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1596 hend = vma->vm_end & HPAGE_PMD_MASK;
1598 return khugepaged_enter(vma);
1602 void __khugepaged_exit(struct mm_struct *mm)
1604 struct mm_slot *mm_slot;
1607 spin_lock(&khugepaged_mm_lock);
1608 mm_slot = get_mm_slot(mm);
1609 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1610 hlist_del(&mm_slot->hash);
1611 list_del(&mm_slot->mm_node);
1616 spin_unlock(&khugepaged_mm_lock);
1617 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1618 free_mm_slot(mm_slot);
1620 } else if (mm_slot) {
1621 spin_unlock(&khugepaged_mm_lock);
1623 * This is required to serialize against
1624 * khugepaged_test_exit() (which is guaranteed to run
1625 * under mmap sem read mode). Stop here (after we
1626 * return all pagetables will be destroyed) until
1627 * khugepaged has finished working on the pagetables
1628 * under the mmap_sem.
1630 down_write(&mm->mmap_sem);
1631 up_write(&mm->mmap_sem);
1633 spin_unlock(&khugepaged_mm_lock);
1636 static void release_pte_page(struct page *page)
1638 /* 0 stands for page_is_file_cache(page) == false */
1639 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1641 putback_lru_page(page);
1644 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1646 while (--_pte >= pte) {
1647 pte_t pteval = *_pte;
1648 if (!pte_none(pteval))
1649 release_pte_page(pte_page(pteval));
1653 static void release_all_pte_pages(pte_t *pte)
1655 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1658 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1659 unsigned long address,
1664 int referenced = 0, isolated = 0, none = 0;
1665 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1666 _pte++, address += PAGE_SIZE) {
1667 pte_t pteval = *_pte;
1668 if (pte_none(pteval)) {
1669 if (++none <= khugepaged_max_ptes_none)
1672 release_pte_pages(pte, _pte);
1676 if (!pte_present(pteval) || !pte_write(pteval)) {
1677 release_pte_pages(pte, _pte);
1680 page = vm_normal_page(vma, address, pteval);
1681 if (unlikely(!page)) {
1682 release_pte_pages(pte, _pte);
1685 VM_BUG_ON(PageCompound(page));
1686 BUG_ON(!PageAnon(page));
1687 VM_BUG_ON(!PageSwapBacked(page));
1689 /* cannot use mapcount: can't collapse if there's a gup pin */
1690 if (page_count(page) != 1) {
1691 release_pte_pages(pte, _pte);
1695 * We can do it before isolate_lru_page because the
1696 * page can't be freed from under us. NOTE: PG_lock
1697 * is needed to serialize against split_huge_page
1698 * when invoked from the VM.
1700 if (!trylock_page(page)) {
1701 release_pte_pages(pte, _pte);
1705 * Isolate the page to avoid collapsing an hugepage
1706 * currently in use by the VM.
1708 if (isolate_lru_page(page)) {
1710 release_pte_pages(pte, _pte);
1713 /* 0 stands for page_is_file_cache(page) == false */
1714 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1715 VM_BUG_ON(!PageLocked(page));
1716 VM_BUG_ON(PageLRU(page));
1718 /* If there is no mapped pte young don't collapse the page */
1719 if (pte_young(pteval) || PageReferenced(page) ||
1720 mmu_notifier_test_young(vma->vm_mm, address))
1723 if (unlikely(!referenced))
1724 release_all_pte_pages(pte);
1731 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1732 struct vm_area_struct *vma,
1733 unsigned long address,
1737 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1738 pte_t pteval = *_pte;
1739 struct page *src_page;
1741 if (pte_none(pteval)) {
1742 clear_user_highpage(page, address);
1743 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1745 src_page = pte_page(pteval);
1746 copy_user_highpage(page, src_page, address, vma);
1747 VM_BUG_ON(page_mapcount(src_page) != 1);
1748 VM_BUG_ON(page_count(src_page) != 2);
1749 release_pte_page(src_page);
1751 * ptl mostly unnecessary, but preempt has to
1752 * be disabled to update the per-cpu stats
1753 * inside page_remove_rmap().
1757 * paravirt calls inside pte_clear here are
1760 pte_clear(vma->vm_mm, address, _pte);
1761 page_remove_rmap(src_page);
1763 free_page_and_swap_cache(src_page);
1766 address += PAGE_SIZE;
1771 static void collapse_huge_page(struct mm_struct *mm,
1772 unsigned long address,
1773 struct page **hpage,
1774 struct vm_area_struct *vma,
1782 struct page *new_page;
1785 unsigned long hstart, hend;
1787 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1789 up_read(&mm->mmap_sem);
1795 * Allocate the page while the vma is still valid and under
1796 * the mmap_sem read mode so there is no memory allocation
1797 * later when we take the mmap_sem in write mode. This is more
1798 * friendly behavior (OTOH it may actually hide bugs) to
1799 * filesystems in userland with daemons allocating memory in
1800 * the userland I/O paths. Allocating memory with the
1801 * mmap_sem in read mode is good idea also to allow greater
1804 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1805 node, __GFP_OTHER_NODE);
1808 * After allocating the hugepage, release the mmap_sem read lock in
1809 * preparation for taking it in write mode.
1811 up_read(&mm->mmap_sem);
1812 if (unlikely(!new_page)) {
1813 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1814 *hpage = ERR_PTR(-ENOMEM);
1819 count_vm_event(THP_COLLAPSE_ALLOC);
1820 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1828 * Prevent all access to pagetables with the exception of
1829 * gup_fast later hanlded by the ptep_clear_flush and the VM
1830 * handled by the anon_vma lock + PG_lock.
1832 down_write(&mm->mmap_sem);
1833 if (unlikely(khugepaged_test_exit(mm)))
1836 vma = find_vma(mm, address);
1837 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1838 hend = vma->vm_end & HPAGE_PMD_MASK;
1839 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1842 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1843 (vma->vm_flags & VM_NOHUGEPAGE))
1846 if (!vma->anon_vma || vma->vm_ops)
1848 if (is_vma_temporary_stack(vma))
1851 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1852 * true too, verify it here.
1854 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1856 pgd = pgd_offset(mm, address);
1857 if (!pgd_present(*pgd))
1860 pud = pud_offset(pgd, address);
1861 if (!pud_present(*pud))
1864 pmd = pmd_offset(pud, address);
1865 /* pmd can't go away or become huge under us */
1866 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1869 anon_vma_lock(vma->anon_vma);
1871 pte = pte_offset_map(pmd, address);
1872 ptl = pte_lockptr(mm, pmd);
1874 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1876 * After this gup_fast can't run anymore. This also removes
1877 * any huge TLB entry from the CPU so we won't allow
1878 * huge and small TLB entries for the same virtual address
1879 * to avoid the risk of CPU bugs in that area.
1881 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1882 spin_unlock(&mm->page_table_lock);
1885 isolated = __collapse_huge_page_isolate(vma, address, pte);
1888 if (unlikely(!isolated)) {
1890 spin_lock(&mm->page_table_lock);
1891 BUG_ON(!pmd_none(*pmd));
1892 set_pmd_at(mm, address, pmd, _pmd);
1893 spin_unlock(&mm->page_table_lock);
1894 anon_vma_unlock(vma->anon_vma);
1899 * All pages are isolated and locked so anon_vma rmap
1900 * can't run anymore.
1902 anon_vma_unlock(vma->anon_vma);
1904 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1906 __SetPageUptodate(new_page);
1907 pgtable = pmd_pgtable(_pmd);
1908 VM_BUG_ON(page_count(pgtable) != 1);
1909 VM_BUG_ON(page_mapcount(pgtable) != 0);
1911 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1912 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1913 _pmd = pmd_mkhuge(_pmd);
1916 * spin_lock() below is not the equivalent of smp_wmb(), so
1917 * this is needed to avoid the copy_huge_page writes to become
1918 * visible after the set_pmd_at() write.
1922 spin_lock(&mm->page_table_lock);
1923 BUG_ON(!pmd_none(*pmd));
1924 page_add_new_anon_rmap(new_page, vma, address);
1925 set_pmd_at(mm, address, pmd, _pmd);
1926 update_mmu_cache(vma, address, entry);
1927 prepare_pmd_huge_pte(pgtable, mm);
1929 spin_unlock(&mm->page_table_lock);
1934 khugepaged_pages_collapsed++;
1936 up_write(&mm->mmap_sem);
1940 mem_cgroup_uncharge_page(new_page);
1947 static int khugepaged_scan_pmd(struct mm_struct *mm,
1948 struct vm_area_struct *vma,
1949 unsigned long address,
1950 struct page **hpage)
1956 int ret = 0, referenced = 0, none = 0;
1958 unsigned long _address;
1962 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1964 pgd = pgd_offset(mm, address);
1965 if (!pgd_present(*pgd))
1968 pud = pud_offset(pgd, address);
1969 if (!pud_present(*pud))
1972 pmd = pmd_offset(pud, address);
1973 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1976 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1977 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1978 _pte++, _address += PAGE_SIZE) {
1979 pte_t pteval = *_pte;
1980 if (pte_none(pteval)) {
1981 if (++none <= khugepaged_max_ptes_none)
1986 if (!pte_present(pteval) || !pte_write(pteval))
1988 page = vm_normal_page(vma, _address, pteval);
1989 if (unlikely(!page))
1992 * Chose the node of the first page. This could
1993 * be more sophisticated and look at more pages,
1994 * but isn't for now.
1997 node = page_to_nid(page);
1998 VM_BUG_ON(PageCompound(page));
1999 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2001 /* cannot use mapcount: can't collapse if there's a gup pin */
2002 if (page_count(page) != 1)
2004 if (pte_young(pteval) || PageReferenced(page) ||
2005 mmu_notifier_test_young(vma->vm_mm, address))
2011 pte_unmap_unlock(pte, ptl);
2013 /* collapse_huge_page will return with the mmap_sem released */
2014 collapse_huge_page(mm, address, hpage, vma, node);
2019 static void collect_mm_slot(struct mm_slot *mm_slot)
2021 struct mm_struct *mm = mm_slot->mm;
2023 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2025 if (khugepaged_test_exit(mm)) {
2027 hlist_del(&mm_slot->hash);
2028 list_del(&mm_slot->mm_node);
2031 * Not strictly needed because the mm exited already.
2033 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2036 /* khugepaged_mm_lock actually not necessary for the below */
2037 free_mm_slot(mm_slot);
2042 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2043 struct page **hpage)
2045 struct mm_slot *mm_slot;
2046 struct mm_struct *mm;
2047 struct vm_area_struct *vma;
2051 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2053 if (khugepaged_scan.mm_slot)
2054 mm_slot = khugepaged_scan.mm_slot;
2056 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2057 struct mm_slot, mm_node);
2058 khugepaged_scan.address = 0;
2059 khugepaged_scan.mm_slot = mm_slot;
2061 spin_unlock(&khugepaged_mm_lock);
2064 down_read(&mm->mmap_sem);
2065 if (unlikely(khugepaged_test_exit(mm)))
2068 vma = find_vma(mm, khugepaged_scan.address);
2071 for (; vma; vma = vma->vm_next) {
2072 unsigned long hstart, hend;
2075 if (unlikely(khugepaged_test_exit(mm))) {
2080 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2081 !khugepaged_always()) ||
2082 (vma->vm_flags & VM_NOHUGEPAGE)) {
2087 if (!vma->anon_vma || vma->vm_ops)
2089 if (is_vma_temporary_stack(vma))
2092 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2093 * must be true too, verify it here.
2095 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2096 vma->vm_flags & VM_NO_THP);
2098 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2099 hend = vma->vm_end & HPAGE_PMD_MASK;
2102 if (khugepaged_scan.address > hend)
2104 if (khugepaged_scan.address < hstart)
2105 khugepaged_scan.address = hstart;
2106 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2108 while (khugepaged_scan.address < hend) {
2111 if (unlikely(khugepaged_test_exit(mm)))
2112 goto breakouterloop;
2114 VM_BUG_ON(khugepaged_scan.address < hstart ||
2115 khugepaged_scan.address + HPAGE_PMD_SIZE >
2117 ret = khugepaged_scan_pmd(mm, vma,
2118 khugepaged_scan.address,
2120 /* move to next address */
2121 khugepaged_scan.address += HPAGE_PMD_SIZE;
2122 progress += HPAGE_PMD_NR;
2124 /* we released mmap_sem so break loop */
2125 goto breakouterloop_mmap_sem;
2126 if (progress >= pages)
2127 goto breakouterloop;
2131 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2132 breakouterloop_mmap_sem:
2134 spin_lock(&khugepaged_mm_lock);
2135 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2137 * Release the current mm_slot if this mm is about to die, or
2138 * if we scanned all vmas of this mm.
2140 if (khugepaged_test_exit(mm) || !vma) {
2142 * Make sure that if mm_users is reaching zero while
2143 * khugepaged runs here, khugepaged_exit will find
2144 * mm_slot not pointing to the exiting mm.
2146 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2147 khugepaged_scan.mm_slot = list_entry(
2148 mm_slot->mm_node.next,
2149 struct mm_slot, mm_node);
2150 khugepaged_scan.address = 0;
2152 khugepaged_scan.mm_slot = NULL;
2153 khugepaged_full_scans++;
2156 collect_mm_slot(mm_slot);
2162 static int khugepaged_has_work(void)
2164 return !list_empty(&khugepaged_scan.mm_head) &&
2165 khugepaged_enabled();
2168 static int khugepaged_wait_event(void)
2170 return !list_empty(&khugepaged_scan.mm_head) ||
2171 !khugepaged_enabled();
2174 static void khugepaged_do_scan(struct page **hpage)
2176 unsigned int progress = 0, pass_through_head = 0;
2177 unsigned int pages = khugepaged_pages_to_scan;
2179 barrier(); /* write khugepaged_pages_to_scan to local stack */
2181 while (progress < pages) {
2186 *hpage = alloc_hugepage(khugepaged_defrag());
2187 if (unlikely(!*hpage)) {
2188 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2191 count_vm_event(THP_COLLAPSE_ALLOC);
2198 if (unlikely(kthread_should_stop() || freezing(current)))
2201 spin_lock(&khugepaged_mm_lock);
2202 if (!khugepaged_scan.mm_slot)
2203 pass_through_head++;
2204 if (khugepaged_has_work() &&
2205 pass_through_head < 2)
2206 progress += khugepaged_scan_mm_slot(pages - progress,
2210 spin_unlock(&khugepaged_mm_lock);
2214 static void khugepaged_alloc_sleep(void)
2217 add_wait_queue(&khugepaged_wait, &wait);
2218 schedule_timeout_interruptible(
2220 khugepaged_alloc_sleep_millisecs));
2221 remove_wait_queue(&khugepaged_wait, &wait);
2225 static struct page *khugepaged_alloc_hugepage(void)
2230 hpage = alloc_hugepage(khugepaged_defrag());
2232 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2233 khugepaged_alloc_sleep();
2235 count_vm_event(THP_COLLAPSE_ALLOC);
2236 } while (unlikely(!hpage) &&
2237 likely(khugepaged_enabled()));
2242 static void khugepaged_loop(void)
2249 while (likely(khugepaged_enabled())) {
2251 hpage = khugepaged_alloc_hugepage();
2252 if (unlikely(!hpage))
2255 if (IS_ERR(hpage)) {
2256 khugepaged_alloc_sleep();
2261 khugepaged_do_scan(&hpage);
2267 if (unlikely(kthread_should_stop()))
2269 if (khugepaged_has_work()) {
2271 if (!khugepaged_scan_sleep_millisecs)
2273 add_wait_queue(&khugepaged_wait, &wait);
2274 schedule_timeout_interruptible(
2276 khugepaged_scan_sleep_millisecs));
2277 remove_wait_queue(&khugepaged_wait, &wait);
2278 } else if (khugepaged_enabled())
2279 wait_event_freezable(khugepaged_wait,
2280 khugepaged_wait_event());
2284 static int khugepaged(void *none)
2286 struct mm_slot *mm_slot;
2289 set_user_nice(current, 19);
2291 /* serialize with start_khugepaged() */
2292 mutex_lock(&khugepaged_mutex);
2295 mutex_unlock(&khugepaged_mutex);
2296 VM_BUG_ON(khugepaged_thread != current);
2298 VM_BUG_ON(khugepaged_thread != current);
2300 mutex_lock(&khugepaged_mutex);
2301 if (!khugepaged_enabled())
2303 if (unlikely(kthread_should_stop()))
2307 spin_lock(&khugepaged_mm_lock);
2308 mm_slot = khugepaged_scan.mm_slot;
2309 khugepaged_scan.mm_slot = NULL;
2311 collect_mm_slot(mm_slot);
2312 spin_unlock(&khugepaged_mm_lock);
2314 khugepaged_thread = NULL;
2315 mutex_unlock(&khugepaged_mutex);
2320 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2324 spin_lock(&mm->page_table_lock);
2325 if (unlikely(!pmd_trans_huge(*pmd))) {
2326 spin_unlock(&mm->page_table_lock);
2329 page = pmd_page(*pmd);
2330 VM_BUG_ON(!page_count(page));
2332 spin_unlock(&mm->page_table_lock);
2334 split_huge_page(page);
2337 BUG_ON(pmd_trans_huge(*pmd));
2340 static void split_huge_page_address(struct mm_struct *mm,
2341 unsigned long address)
2347 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2349 pgd = pgd_offset(mm, address);
2350 if (!pgd_present(*pgd))
2353 pud = pud_offset(pgd, address);
2354 if (!pud_present(*pud))
2357 pmd = pmd_offset(pud, address);
2358 if (!pmd_present(*pmd))
2361 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2362 * materialize from under us.
2364 split_huge_page_pmd(mm, pmd);
2367 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2368 unsigned long start,
2373 * If the new start address isn't hpage aligned and it could
2374 * previously contain an hugepage: check if we need to split
2377 if (start & ~HPAGE_PMD_MASK &&
2378 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2379 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2380 split_huge_page_address(vma->vm_mm, start);
2383 * If the new end address isn't hpage aligned and it could
2384 * previously contain an hugepage: check if we need to split
2387 if (end & ~HPAGE_PMD_MASK &&
2388 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2389 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2390 split_huge_page_address(vma->vm_mm, end);
2393 * If we're also updating the vma->vm_next->vm_start, if the new
2394 * vm_next->vm_start isn't page aligned and it could previously
2395 * contain an hugepage: check if we need to split an huge pmd.
2397 if (adjust_next > 0) {
2398 struct vm_area_struct *next = vma->vm_next;
2399 unsigned long nstart = next->vm_start;
2400 nstart += adjust_next << PAGE_SHIFT;
2401 if (nstart & ~HPAGE_PMD_MASK &&
2402 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2403 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2404 split_huge_page_address(next->vm_mm, nstart);