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>
19 #include <asm/pgalloc.h>
23 * By default transparent hugepage support is enabled for all mappings
24 * and khugepaged scans all mappings. Defrag is only invoked by
25 * khugepaged hugepage allocations and by page faults inside
26 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
29 unsigned long transparent_hugepage_flags __read_mostly =
30 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
31 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
33 /* default scan 8*512 pte (or vmas) every 30 second */
34 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
35 static unsigned int khugepaged_pages_collapsed;
36 static unsigned int khugepaged_full_scans;
37 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
38 /* during fragmentation poll the hugepage allocator once every minute */
39 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
40 static struct task_struct *khugepaged_thread __read_mostly;
41 static DEFINE_MUTEX(khugepaged_mutex);
42 static DEFINE_SPINLOCK(khugepaged_mm_lock);
43 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
45 * default collapse hugepages if there is at least one pte mapped like
46 * it would have happened if the vma was large enough during page
49 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
51 static int khugepaged(void *none);
52 static int mm_slots_hash_init(void);
53 static int khugepaged_slab_init(void);
54 static void khugepaged_slab_free(void);
56 #define MM_SLOTS_HASH_HEADS 1024
57 static struct hlist_head *mm_slots_hash __read_mostly;
58 static struct kmem_cache *mm_slot_cache __read_mostly;
61 * struct mm_slot - hash lookup from mm to mm_slot
62 * @hash: hash collision list
63 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
64 * @mm: the mm that this information is valid for
67 struct hlist_node hash;
68 struct list_head mm_node;
73 * struct khugepaged_scan - cursor for scanning
74 * @mm_head: the head of the mm list to scan
75 * @mm_slot: the current mm_slot we are scanning
76 * @address: the next address inside that to be scanned
78 * There is only the one khugepaged_scan instance of this cursor structure.
80 struct khugepaged_scan {
81 struct list_head mm_head;
82 struct mm_slot *mm_slot;
83 unsigned long address;
85 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
88 static int start_khugepaged(void)
91 if (khugepaged_enabled()) {
93 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
97 mutex_lock(&khugepaged_mutex);
98 if (!khugepaged_thread)
99 khugepaged_thread = kthread_run(khugepaged, NULL,
101 if (unlikely(IS_ERR(khugepaged_thread))) {
103 "khugepaged: kthread_run(khugepaged) failed\n");
104 err = PTR_ERR(khugepaged_thread);
105 khugepaged_thread = NULL;
107 wakeup = !list_empty(&khugepaged_scan.mm_head);
108 mutex_unlock(&khugepaged_mutex);
110 wake_up_interruptible(&khugepaged_wait);
113 wake_up_interruptible(&khugepaged_wait);
120 static ssize_t double_flag_show(struct kobject *kobj,
121 struct kobj_attribute *attr, char *buf,
122 enum transparent_hugepage_flag enabled,
123 enum transparent_hugepage_flag req_madv)
125 if (test_bit(enabled, &transparent_hugepage_flags)) {
126 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
127 return sprintf(buf, "[always] madvise never\n");
128 } else if (test_bit(req_madv, &transparent_hugepage_flags))
129 return sprintf(buf, "always [madvise] never\n");
131 return sprintf(buf, "always madvise [never]\n");
133 static ssize_t double_flag_store(struct kobject *kobj,
134 struct kobj_attribute *attr,
135 const char *buf, size_t count,
136 enum transparent_hugepage_flag enabled,
137 enum transparent_hugepage_flag req_madv)
139 if (!memcmp("always", buf,
140 min(sizeof("always")-1, count))) {
141 set_bit(enabled, &transparent_hugepage_flags);
142 clear_bit(req_madv, &transparent_hugepage_flags);
143 } else if (!memcmp("madvise", buf,
144 min(sizeof("madvise")-1, count))) {
145 clear_bit(enabled, &transparent_hugepage_flags);
146 set_bit(req_madv, &transparent_hugepage_flags);
147 } else if (!memcmp("never", buf,
148 min(sizeof("never")-1, count))) {
149 clear_bit(enabled, &transparent_hugepage_flags);
150 clear_bit(req_madv, &transparent_hugepage_flags);
157 static ssize_t enabled_show(struct kobject *kobj,
158 struct kobj_attribute *attr, char *buf)
160 return double_flag_show(kobj, attr, buf,
161 TRANSPARENT_HUGEPAGE_FLAG,
162 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
164 static ssize_t enabled_store(struct kobject *kobj,
165 struct kobj_attribute *attr,
166 const char *buf, size_t count)
170 ret = double_flag_store(kobj, attr, buf, count,
171 TRANSPARENT_HUGEPAGE_FLAG,
172 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
175 int err = start_khugepaged();
182 static struct kobj_attribute enabled_attr =
183 __ATTR(enabled, 0644, enabled_show, enabled_store);
185 static ssize_t single_flag_show(struct kobject *kobj,
186 struct kobj_attribute *attr, char *buf,
187 enum transparent_hugepage_flag flag)
189 if (test_bit(flag, &transparent_hugepage_flags))
190 return sprintf(buf, "[yes] no\n");
192 return sprintf(buf, "yes [no]\n");
194 static ssize_t single_flag_store(struct kobject *kobj,
195 struct kobj_attribute *attr,
196 const char *buf, size_t count,
197 enum transparent_hugepage_flag flag)
199 if (!memcmp("yes", buf,
200 min(sizeof("yes")-1, count))) {
201 set_bit(flag, &transparent_hugepage_flags);
202 } else if (!memcmp("no", buf,
203 min(sizeof("no")-1, count))) {
204 clear_bit(flag, &transparent_hugepage_flags);
212 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
213 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
214 * memory just to allocate one more hugepage.
216 static ssize_t defrag_show(struct kobject *kobj,
217 struct kobj_attribute *attr, char *buf)
219 return double_flag_show(kobj, attr, buf,
220 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
221 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
223 static ssize_t defrag_store(struct kobject *kobj,
224 struct kobj_attribute *attr,
225 const char *buf, size_t count)
227 return double_flag_store(kobj, attr, buf, count,
228 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
229 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
231 static struct kobj_attribute defrag_attr =
232 __ATTR(defrag, 0644, defrag_show, defrag_store);
234 #ifdef CONFIG_DEBUG_VM
235 static ssize_t debug_cow_show(struct kobject *kobj,
236 struct kobj_attribute *attr, char *buf)
238 return single_flag_show(kobj, attr, buf,
239 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
241 static ssize_t debug_cow_store(struct kobject *kobj,
242 struct kobj_attribute *attr,
243 const char *buf, size_t count)
245 return single_flag_store(kobj, attr, buf, count,
246 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
248 static struct kobj_attribute debug_cow_attr =
249 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
250 #endif /* CONFIG_DEBUG_VM */
252 static struct attribute *hugepage_attr[] = {
255 #ifdef CONFIG_DEBUG_VM
256 &debug_cow_attr.attr,
261 static struct attribute_group hugepage_attr_group = {
262 .attrs = hugepage_attr,
265 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
266 struct kobj_attribute *attr,
269 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
272 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
273 struct kobj_attribute *attr,
274 const char *buf, size_t count)
279 err = strict_strtoul(buf, 10, &msecs);
280 if (err || msecs > UINT_MAX)
283 khugepaged_scan_sleep_millisecs = msecs;
284 wake_up_interruptible(&khugepaged_wait);
288 static struct kobj_attribute scan_sleep_millisecs_attr =
289 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
290 scan_sleep_millisecs_store);
292 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
293 struct kobj_attribute *attr,
296 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
299 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
300 struct kobj_attribute *attr,
301 const char *buf, size_t count)
306 err = strict_strtoul(buf, 10, &msecs);
307 if (err || msecs > UINT_MAX)
310 khugepaged_alloc_sleep_millisecs = msecs;
311 wake_up_interruptible(&khugepaged_wait);
315 static struct kobj_attribute alloc_sleep_millisecs_attr =
316 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
317 alloc_sleep_millisecs_store);
319 static ssize_t pages_to_scan_show(struct kobject *kobj,
320 struct kobj_attribute *attr,
323 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
325 static ssize_t pages_to_scan_store(struct kobject *kobj,
326 struct kobj_attribute *attr,
327 const char *buf, size_t count)
332 err = strict_strtoul(buf, 10, &pages);
333 if (err || !pages || pages > UINT_MAX)
336 khugepaged_pages_to_scan = pages;
340 static struct kobj_attribute pages_to_scan_attr =
341 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
342 pages_to_scan_store);
344 static ssize_t pages_collapsed_show(struct kobject *kobj,
345 struct kobj_attribute *attr,
348 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
350 static struct kobj_attribute pages_collapsed_attr =
351 __ATTR_RO(pages_collapsed);
353 static ssize_t full_scans_show(struct kobject *kobj,
354 struct kobj_attribute *attr,
357 return sprintf(buf, "%u\n", khugepaged_full_scans);
359 static struct kobj_attribute full_scans_attr =
360 __ATTR_RO(full_scans);
362 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
363 struct kobj_attribute *attr, char *buf)
365 return single_flag_show(kobj, attr, buf,
366 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
368 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
369 struct kobj_attribute *attr,
370 const char *buf, size_t count)
372 return single_flag_store(kobj, attr, buf, count,
373 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
375 static struct kobj_attribute khugepaged_defrag_attr =
376 __ATTR(defrag, 0644, khugepaged_defrag_show,
377 khugepaged_defrag_store);
380 * max_ptes_none controls if khugepaged should collapse hugepages over
381 * any unmapped ptes in turn potentially increasing the memory
382 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
383 * reduce the available free memory in the system as it
384 * runs. Increasing max_ptes_none will instead potentially reduce the
385 * free memory in the system during the khugepaged scan.
387 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
388 struct kobj_attribute *attr,
391 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
393 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
394 struct kobj_attribute *attr,
395 const char *buf, size_t count)
398 unsigned long max_ptes_none;
400 err = strict_strtoul(buf, 10, &max_ptes_none);
401 if (err || max_ptes_none > HPAGE_PMD_NR-1)
404 khugepaged_max_ptes_none = max_ptes_none;
408 static struct kobj_attribute khugepaged_max_ptes_none_attr =
409 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
410 khugepaged_max_ptes_none_store);
412 static struct attribute *khugepaged_attr[] = {
413 &khugepaged_defrag_attr.attr,
414 &khugepaged_max_ptes_none_attr.attr,
415 &pages_to_scan_attr.attr,
416 &pages_collapsed_attr.attr,
417 &full_scans_attr.attr,
418 &scan_sleep_millisecs_attr.attr,
419 &alloc_sleep_millisecs_attr.attr,
423 static struct attribute_group khugepaged_attr_group = {
424 .attrs = khugepaged_attr,
425 .name = "khugepaged",
427 #endif /* CONFIG_SYSFS */
429 static int __init hugepage_init(void)
433 static struct kobject *hugepage_kobj;
436 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
437 if (unlikely(!hugepage_kobj)) {
438 printk(KERN_ERR "hugepage: failed kobject create\n");
442 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
444 printk(KERN_ERR "hugepage: failed register hugeage group\n");
448 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
450 printk(KERN_ERR "hugepage: failed register hugeage group\n");
455 err = khugepaged_slab_init();
459 err = mm_slots_hash_init();
461 khugepaged_slab_free();
470 module_init(hugepage_init)
472 static int __init setup_transparent_hugepage(char *str)
477 if (!strcmp(str, "always")) {
478 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
479 &transparent_hugepage_flags);
480 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
481 &transparent_hugepage_flags);
483 } else if (!strcmp(str, "madvise")) {
484 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
485 &transparent_hugepage_flags);
486 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
487 &transparent_hugepage_flags);
489 } else if (!strcmp(str, "never")) {
490 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
491 &transparent_hugepage_flags);
492 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
493 &transparent_hugepage_flags);
499 "transparent_hugepage= cannot parse, ignored\n");
502 __setup("transparent_hugepage=", setup_transparent_hugepage);
504 static void prepare_pmd_huge_pte(pgtable_t pgtable,
505 struct mm_struct *mm)
507 assert_spin_locked(&mm->page_table_lock);
510 if (!mm->pmd_huge_pte)
511 INIT_LIST_HEAD(&pgtable->lru);
513 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
514 mm->pmd_huge_pte = pgtable;
517 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
519 if (likely(vma->vm_flags & VM_WRITE))
520 pmd = pmd_mkwrite(pmd);
524 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
525 struct vm_area_struct *vma,
526 unsigned long haddr, pmd_t *pmd,
532 VM_BUG_ON(!PageCompound(page));
533 pgtable = pte_alloc_one(mm, haddr);
534 if (unlikely(!pgtable)) {
535 mem_cgroup_uncharge_page(page);
540 clear_huge_page(page, haddr, HPAGE_PMD_NR);
541 __SetPageUptodate(page);
543 spin_lock(&mm->page_table_lock);
544 if (unlikely(!pmd_none(*pmd))) {
545 spin_unlock(&mm->page_table_lock);
546 mem_cgroup_uncharge_page(page);
548 pte_free(mm, pgtable);
551 entry = mk_pmd(page, vma->vm_page_prot);
552 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
553 entry = pmd_mkhuge(entry);
555 * The spinlocking to take the lru_lock inside
556 * page_add_new_anon_rmap() acts as a full memory
557 * barrier to be sure clear_huge_page writes become
558 * visible after the set_pmd_at() write.
560 page_add_new_anon_rmap(page, vma, haddr);
561 set_pmd_at(mm, haddr, pmd, entry);
562 prepare_pmd_huge_pte(pgtable, mm);
563 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
564 spin_unlock(&mm->page_table_lock);
570 static inline struct page *alloc_hugepage(int defrag)
572 return alloc_pages(GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT),
576 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
577 unsigned long address, pmd_t *pmd,
581 unsigned long haddr = address & HPAGE_PMD_MASK;
584 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
585 if (unlikely(anon_vma_prepare(vma)))
587 if (unlikely(khugepaged_enter(vma)))
589 page = alloc_hugepage(transparent_hugepage_defrag(vma));
592 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
597 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
601 * Use __pte_alloc instead of pte_alloc_map, because we can't
602 * run pte_offset_map on the pmd, if an huge pmd could
603 * materialize from under us from a different thread.
605 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
607 /* if an huge pmd materialized from under us just retry later */
608 if (unlikely(pmd_trans_huge(*pmd)))
611 * A regular pmd is established and it can't morph into a huge pmd
612 * from under us anymore at this point because we hold the mmap_sem
613 * read mode and khugepaged takes it in write mode. So now it's
614 * safe to run pte_offset_map().
616 pte = pte_offset_map(pmd, address);
617 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
620 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
621 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
622 struct vm_area_struct *vma)
624 struct page *src_page;
630 pgtable = pte_alloc_one(dst_mm, addr);
631 if (unlikely(!pgtable))
634 spin_lock(&dst_mm->page_table_lock);
635 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
639 if (unlikely(!pmd_trans_huge(pmd))) {
640 pte_free(dst_mm, pgtable);
643 if (unlikely(pmd_trans_splitting(pmd))) {
644 /* split huge page running from under us */
645 spin_unlock(&src_mm->page_table_lock);
646 spin_unlock(&dst_mm->page_table_lock);
647 pte_free(dst_mm, pgtable);
649 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
652 src_page = pmd_page(pmd);
653 VM_BUG_ON(!PageHead(src_page));
655 page_dup_rmap(src_page);
656 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
658 pmdp_set_wrprotect(src_mm, addr, src_pmd);
659 pmd = pmd_mkold(pmd_wrprotect(pmd));
660 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
661 prepare_pmd_huge_pte(pgtable, dst_mm);
665 spin_unlock(&src_mm->page_table_lock);
666 spin_unlock(&dst_mm->page_table_lock);
671 /* no "address" argument so destroys page coloring of some arch */
672 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
676 assert_spin_locked(&mm->page_table_lock);
679 pgtable = mm->pmd_huge_pte;
680 if (list_empty(&pgtable->lru))
681 mm->pmd_huge_pte = NULL;
683 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
685 list_del(&pgtable->lru);
690 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
691 struct vm_area_struct *vma,
692 unsigned long address,
693 pmd_t *pmd, pmd_t orig_pmd,
702 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
704 if (unlikely(!pages)) {
709 for (i = 0; i < HPAGE_PMD_NR; i++) {
710 pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
712 if (unlikely(!pages[i] ||
713 mem_cgroup_newpage_charge(pages[i], mm,
717 mem_cgroup_uncharge_start();
719 mem_cgroup_uncharge_page(pages[i]);
722 mem_cgroup_uncharge_end();
729 for (i = 0; i < HPAGE_PMD_NR; i++) {
730 copy_user_highpage(pages[i], page + i,
731 haddr + PAGE_SHIFT*i, vma);
732 __SetPageUptodate(pages[i]);
736 spin_lock(&mm->page_table_lock);
737 if (unlikely(!pmd_same(*pmd, orig_pmd)))
739 VM_BUG_ON(!PageHead(page));
741 pmdp_clear_flush_notify(vma, haddr, pmd);
742 /* leave pmd empty until pte is filled */
744 pgtable = get_pmd_huge_pte(mm);
745 pmd_populate(mm, &_pmd, pgtable);
747 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
749 entry = mk_pte(pages[i], vma->vm_page_prot);
750 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
751 page_add_new_anon_rmap(pages[i], vma, haddr);
752 pte = pte_offset_map(&_pmd, haddr);
753 VM_BUG_ON(!pte_none(*pte));
754 set_pte_at(mm, haddr, pte, entry);
760 smp_wmb(); /* make pte visible before pmd */
761 pmd_populate(mm, pmd, pgtable);
762 page_remove_rmap(page);
763 spin_unlock(&mm->page_table_lock);
765 ret |= VM_FAULT_WRITE;
772 spin_unlock(&mm->page_table_lock);
773 mem_cgroup_uncharge_start();
774 for (i = 0; i < HPAGE_PMD_NR; i++) {
775 mem_cgroup_uncharge_page(pages[i]);
778 mem_cgroup_uncharge_end();
783 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
784 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
787 struct page *page, *new_page;
790 VM_BUG_ON(!vma->anon_vma);
791 spin_lock(&mm->page_table_lock);
792 if (unlikely(!pmd_same(*pmd, orig_pmd)))
795 page = pmd_page(orig_pmd);
796 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
797 haddr = address & HPAGE_PMD_MASK;
798 if (page_mapcount(page) == 1) {
800 entry = pmd_mkyoung(orig_pmd);
801 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
802 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
803 update_mmu_cache(vma, address, entry);
804 ret |= VM_FAULT_WRITE;
808 spin_unlock(&mm->page_table_lock);
810 if (transparent_hugepage_enabled(vma) &&
811 !transparent_hugepage_debug_cow())
812 new_page = alloc_hugepage(transparent_hugepage_defrag(vma));
816 if (unlikely(!new_page)) {
817 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
818 pmd, orig_pmd, page, haddr);
823 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
830 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
831 __SetPageUptodate(new_page);
833 spin_lock(&mm->page_table_lock);
835 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
836 mem_cgroup_uncharge_page(new_page);
840 VM_BUG_ON(!PageHead(page));
841 entry = mk_pmd(new_page, vma->vm_page_prot);
842 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
843 entry = pmd_mkhuge(entry);
844 pmdp_clear_flush_notify(vma, haddr, pmd);
845 page_add_new_anon_rmap(new_page, vma, haddr);
846 set_pmd_at(mm, haddr, pmd, entry);
847 update_mmu_cache(vma, address, entry);
848 page_remove_rmap(page);
850 ret |= VM_FAULT_WRITE;
853 spin_unlock(&mm->page_table_lock);
858 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
863 struct page *page = NULL;
865 assert_spin_locked(&mm->page_table_lock);
867 if (flags & FOLL_WRITE && !pmd_write(*pmd))
870 page = pmd_page(*pmd);
871 VM_BUG_ON(!PageHead(page));
872 if (flags & FOLL_TOUCH) {
875 * We should set the dirty bit only for FOLL_WRITE but
876 * for now the dirty bit in the pmd is meaningless.
877 * And if the dirty bit will become meaningful and
878 * we'll only set it with FOLL_WRITE, an atomic
879 * set_bit will be required on the pmd to set the
880 * young bit, instead of the current set_pmd_at.
882 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
883 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
885 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
886 VM_BUG_ON(!PageCompound(page));
887 if (flags & FOLL_GET)
894 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
899 spin_lock(&tlb->mm->page_table_lock);
900 if (likely(pmd_trans_huge(*pmd))) {
901 if (unlikely(pmd_trans_splitting(*pmd))) {
902 spin_unlock(&tlb->mm->page_table_lock);
903 wait_split_huge_page(vma->anon_vma,
908 pgtable = get_pmd_huge_pte(tlb->mm);
909 page = pmd_page(*pmd);
911 page_remove_rmap(page);
912 VM_BUG_ON(page_mapcount(page) < 0);
913 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
914 VM_BUG_ON(!PageHead(page));
915 spin_unlock(&tlb->mm->page_table_lock);
916 tlb_remove_page(tlb, page);
917 pte_free(tlb->mm, pgtable);
921 spin_unlock(&tlb->mm->page_table_lock);
926 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
927 unsigned long addr, unsigned long end,
932 spin_lock(&vma->vm_mm->page_table_lock);
933 if (likely(pmd_trans_huge(*pmd))) {
934 ret = !pmd_trans_splitting(*pmd);
935 spin_unlock(&vma->vm_mm->page_table_lock);
937 wait_split_huge_page(vma->anon_vma, pmd);
940 * All logical pages in the range are present
941 * if backed by a huge page.
943 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
946 spin_unlock(&vma->vm_mm->page_table_lock);
951 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
952 unsigned long addr, pgprot_t newprot)
954 struct mm_struct *mm = vma->vm_mm;
957 spin_lock(&mm->page_table_lock);
958 if (likely(pmd_trans_huge(*pmd))) {
959 if (unlikely(pmd_trans_splitting(*pmd))) {
960 spin_unlock(&mm->page_table_lock);
961 wait_split_huge_page(vma->anon_vma, pmd);
965 entry = pmdp_get_and_clear(mm, addr, pmd);
966 entry = pmd_modify(entry, newprot);
967 set_pmd_at(mm, addr, pmd, entry);
968 spin_unlock(&vma->vm_mm->page_table_lock);
969 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
973 spin_unlock(&vma->vm_mm->page_table_lock);
978 pmd_t *page_check_address_pmd(struct page *page,
979 struct mm_struct *mm,
980 unsigned long address,
981 enum page_check_address_pmd_flag flag)
985 pmd_t *pmd, *ret = NULL;
987 if (address & ~HPAGE_PMD_MASK)
990 pgd = pgd_offset(mm, address);
991 if (!pgd_present(*pgd))
994 pud = pud_offset(pgd, address);
995 if (!pud_present(*pud))
998 pmd = pmd_offset(pud, address);
1001 if (pmd_page(*pmd) != page)
1003 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1004 pmd_trans_splitting(*pmd));
1005 if (pmd_trans_huge(*pmd)) {
1006 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1007 !pmd_trans_splitting(*pmd));
1014 static int __split_huge_page_splitting(struct page *page,
1015 struct vm_area_struct *vma,
1016 unsigned long address)
1018 struct mm_struct *mm = vma->vm_mm;
1022 spin_lock(&mm->page_table_lock);
1023 pmd = page_check_address_pmd(page, mm, address,
1024 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1027 * We can't temporarily set the pmd to null in order
1028 * to split it, the pmd must remain marked huge at all
1029 * times or the VM won't take the pmd_trans_huge paths
1030 * and it won't wait on the anon_vma->root->lock to
1031 * serialize against split_huge_page*.
1033 pmdp_splitting_flush_notify(vma, address, pmd);
1036 spin_unlock(&mm->page_table_lock);
1041 static void __split_huge_page_refcount(struct page *page)
1044 unsigned long head_index = page->index;
1045 struct zone *zone = page_zone(page);
1047 /* prevent PageLRU to go away from under us, and freeze lru stats */
1048 spin_lock_irq(&zone->lru_lock);
1049 compound_lock(page);
1051 for (i = 1; i < HPAGE_PMD_NR; i++) {
1052 struct page *page_tail = page + i;
1054 /* tail_page->_count cannot change */
1055 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1056 BUG_ON(page_count(page) <= 0);
1057 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1058 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1060 /* after clearing PageTail the gup refcount can be released */
1063 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1064 page_tail->flags |= (page->flags &
1065 ((1L << PG_referenced) |
1066 (1L << PG_swapbacked) |
1067 (1L << PG_mlocked) |
1068 (1L << PG_uptodate)));
1069 page_tail->flags |= (1L << PG_dirty);
1072 * 1) clear PageTail before overwriting first_page
1073 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1078 * __split_huge_page_splitting() already set the
1079 * splitting bit in all pmd that could map this
1080 * hugepage, that will ensure no CPU can alter the
1081 * mapcount on the head page. The mapcount is only
1082 * accounted in the head page and it has to be
1083 * transferred to all tail pages in the below code. So
1084 * for this code to be safe, the split the mapcount
1085 * can't change. But that doesn't mean userland can't
1086 * keep changing and reading the page contents while
1087 * we transfer the mapcount, so the pmd splitting
1088 * status is achieved setting a reserved bit in the
1089 * pmd, not by clearing the present bit.
1091 BUG_ON(page_mapcount(page_tail));
1092 page_tail->_mapcount = page->_mapcount;
1094 BUG_ON(page_tail->mapping);
1095 page_tail->mapping = page->mapping;
1097 page_tail->index = ++head_index;
1099 BUG_ON(!PageAnon(page_tail));
1100 BUG_ON(!PageUptodate(page_tail));
1101 BUG_ON(!PageDirty(page_tail));
1102 BUG_ON(!PageSwapBacked(page_tail));
1104 lru_add_page_tail(zone, page, page_tail);
1107 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1108 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1110 ClearPageCompound(page);
1111 compound_unlock(page);
1112 spin_unlock_irq(&zone->lru_lock);
1114 for (i = 1; i < HPAGE_PMD_NR; i++) {
1115 struct page *page_tail = page + i;
1116 BUG_ON(page_count(page_tail) <= 0);
1118 * Tail pages may be freed if there wasn't any mapping
1119 * like if add_to_swap() is running on a lru page that
1120 * had its mapping zapped. And freeing these pages
1121 * requires taking the lru_lock so we do the put_page
1122 * of the tail pages after the split is complete.
1124 put_page(page_tail);
1128 * Only the head page (now become a regular page) is required
1129 * to be pinned by the caller.
1131 BUG_ON(page_count(page) <= 0);
1134 static int __split_huge_page_map(struct page *page,
1135 struct vm_area_struct *vma,
1136 unsigned long address)
1138 struct mm_struct *mm = vma->vm_mm;
1142 unsigned long haddr;
1144 spin_lock(&mm->page_table_lock);
1145 pmd = page_check_address_pmd(page, mm, address,
1146 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1148 pgtable = get_pmd_huge_pte(mm);
1149 pmd_populate(mm, &_pmd, pgtable);
1151 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1152 i++, haddr += PAGE_SIZE) {
1154 BUG_ON(PageCompound(page+i));
1155 entry = mk_pte(page + i, vma->vm_page_prot);
1156 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1157 if (!pmd_write(*pmd))
1158 entry = pte_wrprotect(entry);
1160 BUG_ON(page_mapcount(page) != 1);
1161 if (!pmd_young(*pmd))
1162 entry = pte_mkold(entry);
1163 pte = pte_offset_map(&_pmd, haddr);
1164 BUG_ON(!pte_none(*pte));
1165 set_pte_at(mm, haddr, pte, entry);
1170 smp_wmb(); /* make pte visible before pmd */
1172 * Up to this point the pmd is present and huge and
1173 * userland has the whole access to the hugepage
1174 * during the split (which happens in place). If we
1175 * overwrite the pmd with the not-huge version
1176 * pointing to the pte here (which of course we could
1177 * if all CPUs were bug free), userland could trigger
1178 * a small page size TLB miss on the small sized TLB
1179 * while the hugepage TLB entry is still established
1180 * in the huge TLB. Some CPU doesn't like that. See
1181 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1182 * Erratum 383 on page 93. Intel should be safe but is
1183 * also warns that it's only safe if the permission
1184 * and cache attributes of the two entries loaded in
1185 * the two TLB is identical (which should be the case
1186 * here). But it is generally safer to never allow
1187 * small and huge TLB entries for the same virtual
1188 * address to be loaded simultaneously. So instead of
1189 * doing "pmd_populate(); flush_tlb_range();" we first
1190 * mark the current pmd notpresent (atomically because
1191 * here the pmd_trans_huge and pmd_trans_splitting
1192 * must remain set at all times on the pmd until the
1193 * split is complete for this pmd), then we flush the
1194 * SMP TLB and finally we write the non-huge version
1195 * of the pmd entry with pmd_populate.
1197 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1198 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1199 pmd_populate(mm, pmd, pgtable);
1202 spin_unlock(&mm->page_table_lock);
1207 /* must be called with anon_vma->root->lock hold */
1208 static void __split_huge_page(struct page *page,
1209 struct anon_vma *anon_vma)
1211 int mapcount, mapcount2;
1212 struct anon_vma_chain *avc;
1214 BUG_ON(!PageHead(page));
1215 BUG_ON(PageTail(page));
1218 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1219 struct vm_area_struct *vma = avc->vma;
1220 unsigned long addr = vma_address(page, vma);
1221 BUG_ON(is_vma_temporary_stack(vma));
1222 if (addr == -EFAULT)
1224 mapcount += __split_huge_page_splitting(page, vma, addr);
1227 * It is critical that new vmas are added to the tail of the
1228 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1229 * and establishes a child pmd before
1230 * __split_huge_page_splitting() freezes the parent pmd (so if
1231 * we fail to prevent copy_huge_pmd() from running until the
1232 * whole __split_huge_page() is complete), we will still see
1233 * the newly established pmd of the child later during the
1234 * walk, to be able to set it as pmd_trans_splitting too.
1236 if (mapcount != page_mapcount(page))
1237 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1238 mapcount, page_mapcount(page));
1239 BUG_ON(mapcount != page_mapcount(page));
1241 __split_huge_page_refcount(page);
1244 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1245 struct vm_area_struct *vma = avc->vma;
1246 unsigned long addr = vma_address(page, vma);
1247 BUG_ON(is_vma_temporary_stack(vma));
1248 if (addr == -EFAULT)
1250 mapcount2 += __split_huge_page_map(page, vma, addr);
1252 if (mapcount != mapcount2)
1253 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1254 mapcount, mapcount2, page_mapcount(page));
1255 BUG_ON(mapcount != mapcount2);
1258 int split_huge_page(struct page *page)
1260 struct anon_vma *anon_vma;
1263 BUG_ON(!PageAnon(page));
1264 anon_vma = page_lock_anon_vma(page);
1268 if (!PageCompound(page))
1271 BUG_ON(!PageSwapBacked(page));
1272 __split_huge_page(page, anon_vma);
1274 BUG_ON(PageCompound(page));
1276 page_unlock_anon_vma(anon_vma);
1281 int hugepage_madvise(unsigned long *vm_flags)
1284 * Be somewhat over-protective like KSM for now!
1286 if (*vm_flags & (VM_HUGEPAGE | VM_SHARED | VM_MAYSHARE |
1287 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1288 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1289 VM_MIXEDMAP | VM_SAO))
1292 *vm_flags |= VM_HUGEPAGE;
1297 static int __init khugepaged_slab_init(void)
1299 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1300 sizeof(struct mm_slot),
1301 __alignof__(struct mm_slot), 0, NULL);
1308 static void __init khugepaged_slab_free(void)
1310 kmem_cache_destroy(mm_slot_cache);
1311 mm_slot_cache = NULL;
1314 static inline struct mm_slot *alloc_mm_slot(void)
1316 if (!mm_slot_cache) /* initialization failed */
1318 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1321 static inline void free_mm_slot(struct mm_slot *mm_slot)
1323 kmem_cache_free(mm_slot_cache, mm_slot);
1326 static int __init mm_slots_hash_init(void)
1328 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1336 static void __init mm_slots_hash_free(void)
1338 kfree(mm_slots_hash);
1339 mm_slots_hash = NULL;
1343 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1345 struct mm_slot *mm_slot;
1346 struct hlist_head *bucket;
1347 struct hlist_node *node;
1349 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1350 % MM_SLOTS_HASH_HEADS];
1351 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1352 if (mm == mm_slot->mm)
1358 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1359 struct mm_slot *mm_slot)
1361 struct hlist_head *bucket;
1363 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1364 % MM_SLOTS_HASH_HEADS];
1366 hlist_add_head(&mm_slot->hash, bucket);
1369 static inline int khugepaged_test_exit(struct mm_struct *mm)
1371 return atomic_read(&mm->mm_users) == 0;
1374 int __khugepaged_enter(struct mm_struct *mm)
1376 struct mm_slot *mm_slot;
1379 mm_slot = alloc_mm_slot();
1383 /* __khugepaged_exit() must not run from under us */
1384 VM_BUG_ON(khugepaged_test_exit(mm));
1385 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1386 free_mm_slot(mm_slot);
1390 spin_lock(&khugepaged_mm_lock);
1391 insert_to_mm_slots_hash(mm, mm_slot);
1393 * Insert just behind the scanning cursor, to let the area settle
1396 wakeup = list_empty(&khugepaged_scan.mm_head);
1397 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1398 spin_unlock(&khugepaged_mm_lock);
1400 atomic_inc(&mm->mm_count);
1402 wake_up_interruptible(&khugepaged_wait);
1407 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1409 unsigned long hstart, hend;
1412 * Not yet faulted in so we will register later in the
1413 * page fault if needed.
1416 if (vma->vm_file || vma->vm_ops)
1417 /* khugepaged not yet working on file or special mappings */
1419 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1420 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1421 hend = vma->vm_end & HPAGE_PMD_MASK;
1423 return khugepaged_enter(vma);
1427 void __khugepaged_exit(struct mm_struct *mm)
1429 struct mm_slot *mm_slot;
1432 spin_lock(&khugepaged_mm_lock);
1433 mm_slot = get_mm_slot(mm);
1434 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1435 hlist_del(&mm_slot->hash);
1436 list_del(&mm_slot->mm_node);
1441 spin_unlock(&khugepaged_mm_lock);
1442 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1443 free_mm_slot(mm_slot);
1445 } else if (mm_slot) {
1446 spin_unlock(&khugepaged_mm_lock);
1448 * This is required to serialize against
1449 * khugepaged_test_exit() (which is guaranteed to run
1450 * under mmap sem read mode). Stop here (after we
1451 * return all pagetables will be destroyed) until
1452 * khugepaged has finished working on the pagetables
1453 * under the mmap_sem.
1455 down_write(&mm->mmap_sem);
1456 up_write(&mm->mmap_sem);
1458 spin_unlock(&khugepaged_mm_lock);
1461 static void release_pte_page(struct page *page)
1463 /* 0 stands for page_is_file_cache(page) == false */
1464 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1466 putback_lru_page(page);
1469 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1471 while (--_pte >= pte) {
1472 pte_t pteval = *_pte;
1473 if (!pte_none(pteval))
1474 release_pte_page(pte_page(pteval));
1478 static void release_all_pte_pages(pte_t *pte)
1480 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1483 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1484 unsigned long address,
1489 int referenced = 0, isolated = 0, none = 0;
1490 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1491 _pte++, address += PAGE_SIZE) {
1492 pte_t pteval = *_pte;
1493 if (pte_none(pteval)) {
1494 if (++none <= khugepaged_max_ptes_none)
1497 release_pte_pages(pte, _pte);
1501 if (!pte_present(pteval) || !pte_write(pteval)) {
1502 release_pte_pages(pte, _pte);
1505 page = vm_normal_page(vma, address, pteval);
1506 if (unlikely(!page)) {
1507 release_pte_pages(pte, _pte);
1510 VM_BUG_ON(PageCompound(page));
1511 BUG_ON(!PageAnon(page));
1512 VM_BUG_ON(!PageSwapBacked(page));
1514 /* cannot use mapcount: can't collapse if there's a gup pin */
1515 if (page_count(page) != 1) {
1516 release_pte_pages(pte, _pte);
1520 * We can do it before isolate_lru_page because the
1521 * page can't be freed from under us. NOTE: PG_lock
1522 * is needed to serialize against split_huge_page
1523 * when invoked from the VM.
1525 if (!trylock_page(page)) {
1526 release_pte_pages(pte, _pte);
1530 * Isolate the page to avoid collapsing an hugepage
1531 * currently in use by the VM.
1533 if (isolate_lru_page(page)) {
1535 release_pte_pages(pte, _pte);
1538 /* 0 stands for page_is_file_cache(page) == false */
1539 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1540 VM_BUG_ON(!PageLocked(page));
1541 VM_BUG_ON(PageLRU(page));
1543 /* If there is no mapped pte young don't collapse the page */
1544 if (pte_young(pteval))
1547 if (unlikely(!referenced))
1548 release_all_pte_pages(pte);
1555 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1556 struct vm_area_struct *vma,
1557 unsigned long address,
1561 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1562 pte_t pteval = *_pte;
1563 struct page *src_page;
1565 if (pte_none(pteval)) {
1566 clear_user_highpage(page, address);
1567 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1569 src_page = pte_page(pteval);
1570 copy_user_highpage(page, src_page, address, vma);
1571 VM_BUG_ON(page_mapcount(src_page) != 1);
1572 VM_BUG_ON(page_count(src_page) != 2);
1573 release_pte_page(src_page);
1575 * ptl mostly unnecessary, but preempt has to
1576 * be disabled to update the per-cpu stats
1577 * inside page_remove_rmap().
1581 * paravirt calls inside pte_clear here are
1584 pte_clear(vma->vm_mm, address, _pte);
1585 page_remove_rmap(src_page);
1587 free_page_and_swap_cache(src_page);
1590 address += PAGE_SIZE;
1595 static void collapse_huge_page(struct mm_struct *mm,
1596 unsigned long address,
1597 struct page **hpage)
1599 struct vm_area_struct *vma;
1605 struct page *new_page;
1608 unsigned long hstart, hend;
1610 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1614 * Prevent all access to pagetables with the exception of
1615 * gup_fast later hanlded by the ptep_clear_flush and the VM
1616 * handled by the anon_vma lock + PG_lock.
1618 down_write(&mm->mmap_sem);
1619 if (unlikely(khugepaged_test_exit(mm)))
1622 vma = find_vma(mm, address);
1623 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1624 hend = vma->vm_end & HPAGE_PMD_MASK;
1625 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1628 if (!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always())
1631 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1632 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
1634 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1636 pgd = pgd_offset(mm, address);
1637 if (!pgd_present(*pgd))
1640 pud = pud_offset(pgd, address);
1641 if (!pud_present(*pud))
1644 pmd = pmd_offset(pud, address);
1645 /* pmd can't go away or become huge under us */
1646 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1650 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
1653 anon_vma_lock(vma->anon_vma);
1655 pte = pte_offset_map(pmd, address);
1656 ptl = pte_lockptr(mm, pmd);
1658 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1660 * After this gup_fast can't run anymore. This also removes
1661 * any huge TLB entry from the CPU so we won't allow
1662 * huge and small TLB entries for the same virtual address
1663 * to avoid the risk of CPU bugs in that area.
1665 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1666 spin_unlock(&mm->page_table_lock);
1669 isolated = __collapse_huge_page_isolate(vma, address, pte);
1673 if (unlikely(!isolated)) {
1674 spin_lock(&mm->page_table_lock);
1675 BUG_ON(!pmd_none(*pmd));
1676 set_pmd_at(mm, address, pmd, _pmd);
1677 spin_unlock(&mm->page_table_lock);
1678 anon_vma_unlock(vma->anon_vma);
1679 mem_cgroup_uncharge_page(new_page);
1684 * All pages are isolated and locked so anon_vma rmap
1685 * can't run anymore.
1687 anon_vma_unlock(vma->anon_vma);
1689 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1690 __SetPageUptodate(new_page);
1691 pgtable = pmd_pgtable(_pmd);
1692 VM_BUG_ON(page_count(pgtable) != 1);
1693 VM_BUG_ON(page_mapcount(pgtable) != 0);
1695 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1696 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1697 _pmd = pmd_mkhuge(_pmd);
1700 * spin_lock() below is not the equivalent of smp_wmb(), so
1701 * this is needed to avoid the copy_huge_page writes to become
1702 * visible after the set_pmd_at() write.
1706 spin_lock(&mm->page_table_lock);
1707 BUG_ON(!pmd_none(*pmd));
1708 page_add_new_anon_rmap(new_page, vma, address);
1709 set_pmd_at(mm, address, pmd, _pmd);
1710 update_mmu_cache(vma, address, entry);
1711 prepare_pmd_huge_pte(pgtable, mm);
1713 spin_unlock(&mm->page_table_lock);
1716 khugepaged_pages_collapsed++;
1718 up_write(&mm->mmap_sem);
1721 static int khugepaged_scan_pmd(struct mm_struct *mm,
1722 struct vm_area_struct *vma,
1723 unsigned long address,
1724 struct page **hpage)
1730 int ret = 0, referenced = 0, none = 0;
1732 unsigned long _address;
1735 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1737 pgd = pgd_offset(mm, address);
1738 if (!pgd_present(*pgd))
1741 pud = pud_offset(pgd, address);
1742 if (!pud_present(*pud))
1745 pmd = pmd_offset(pud, address);
1746 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1749 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1750 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1751 _pte++, _address += PAGE_SIZE) {
1752 pte_t pteval = *_pte;
1753 if (pte_none(pteval)) {
1754 if (++none <= khugepaged_max_ptes_none)
1759 if (!pte_present(pteval) || !pte_write(pteval))
1761 page = vm_normal_page(vma, _address, pteval);
1762 if (unlikely(!page))
1764 VM_BUG_ON(PageCompound(page));
1765 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1767 /* cannot use mapcount: can't collapse if there's a gup pin */
1768 if (page_count(page) != 1)
1770 if (pte_young(pteval))
1776 pte_unmap_unlock(pte, ptl);
1778 up_read(&mm->mmap_sem);
1779 collapse_huge_page(mm, address, hpage);
1785 static void collect_mm_slot(struct mm_slot *mm_slot)
1787 struct mm_struct *mm = mm_slot->mm;
1789 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1791 if (khugepaged_test_exit(mm)) {
1793 hlist_del(&mm_slot->hash);
1794 list_del(&mm_slot->mm_node);
1797 * Not strictly needed because the mm exited already.
1799 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1802 /* khugepaged_mm_lock actually not necessary for the below */
1803 free_mm_slot(mm_slot);
1808 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1809 struct page **hpage)
1811 struct mm_slot *mm_slot;
1812 struct mm_struct *mm;
1813 struct vm_area_struct *vma;
1817 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1819 if (khugepaged_scan.mm_slot)
1820 mm_slot = khugepaged_scan.mm_slot;
1822 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1823 struct mm_slot, mm_node);
1824 khugepaged_scan.address = 0;
1825 khugepaged_scan.mm_slot = mm_slot;
1827 spin_unlock(&khugepaged_mm_lock);
1830 down_read(&mm->mmap_sem);
1831 if (unlikely(khugepaged_test_exit(mm)))
1834 vma = find_vma(mm, khugepaged_scan.address);
1837 for (; vma; vma = vma->vm_next) {
1838 unsigned long hstart, hend;
1841 if (unlikely(khugepaged_test_exit(mm))) {
1846 if (!(vma->vm_flags & VM_HUGEPAGE) &&
1847 !khugepaged_always()) {
1852 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1853 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) {
1854 khugepaged_scan.address = vma->vm_end;
1858 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1860 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1861 hend = vma->vm_end & HPAGE_PMD_MASK;
1862 if (hstart >= hend) {
1866 if (khugepaged_scan.address < hstart)
1867 khugepaged_scan.address = hstart;
1868 if (khugepaged_scan.address > hend) {
1869 khugepaged_scan.address = hend + HPAGE_PMD_SIZE;
1873 BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1875 while (khugepaged_scan.address < hend) {
1878 if (unlikely(khugepaged_test_exit(mm)))
1879 goto breakouterloop;
1881 VM_BUG_ON(khugepaged_scan.address < hstart ||
1882 khugepaged_scan.address + HPAGE_PMD_SIZE >
1884 ret = khugepaged_scan_pmd(mm, vma,
1885 khugepaged_scan.address,
1887 /* move to next address */
1888 khugepaged_scan.address += HPAGE_PMD_SIZE;
1889 progress += HPAGE_PMD_NR;
1891 /* we released mmap_sem so break loop */
1892 goto breakouterloop_mmap_sem;
1893 if (progress >= pages)
1894 goto breakouterloop;
1898 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1899 breakouterloop_mmap_sem:
1901 spin_lock(&khugepaged_mm_lock);
1902 BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1904 * Release the current mm_slot if this mm is about to die, or
1905 * if we scanned all vmas of this mm.
1907 if (khugepaged_test_exit(mm) || !vma) {
1909 * Make sure that if mm_users is reaching zero while
1910 * khugepaged runs here, khugepaged_exit will find
1911 * mm_slot not pointing to the exiting mm.
1913 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1914 khugepaged_scan.mm_slot = list_entry(
1915 mm_slot->mm_node.next,
1916 struct mm_slot, mm_node);
1917 khugepaged_scan.address = 0;
1919 khugepaged_scan.mm_slot = NULL;
1920 khugepaged_full_scans++;
1923 collect_mm_slot(mm_slot);
1929 static int khugepaged_has_work(void)
1931 return !list_empty(&khugepaged_scan.mm_head) &&
1932 khugepaged_enabled();
1935 static int khugepaged_wait_event(void)
1937 return !list_empty(&khugepaged_scan.mm_head) ||
1938 !khugepaged_enabled();
1941 static void khugepaged_do_scan(struct page **hpage)
1943 unsigned int progress = 0, pass_through_head = 0;
1944 unsigned int pages = khugepaged_pages_to_scan;
1946 barrier(); /* write khugepaged_pages_to_scan to local stack */
1948 while (progress < pages) {
1952 *hpage = alloc_hugepage(khugepaged_defrag());
1953 if (unlikely(!*hpage))
1957 spin_lock(&khugepaged_mm_lock);
1958 if (!khugepaged_scan.mm_slot)
1959 pass_through_head++;
1960 if (khugepaged_has_work() &&
1961 pass_through_head < 2)
1962 progress += khugepaged_scan_mm_slot(pages - progress,
1966 spin_unlock(&khugepaged_mm_lock);
1970 static struct page *khugepaged_alloc_hugepage(void)
1975 hpage = alloc_hugepage(khugepaged_defrag());
1978 add_wait_queue(&khugepaged_wait, &wait);
1979 schedule_timeout_interruptible(
1981 khugepaged_alloc_sleep_millisecs));
1982 remove_wait_queue(&khugepaged_wait, &wait);
1984 } while (unlikely(!hpage) &&
1985 likely(khugepaged_enabled()));
1989 static void khugepaged_loop(void)
1993 while (likely(khugepaged_enabled())) {
1994 hpage = khugepaged_alloc_hugepage();
1995 if (unlikely(!hpage))
1998 khugepaged_do_scan(&hpage);
2001 if (khugepaged_has_work()) {
2003 if (!khugepaged_scan_sleep_millisecs)
2005 add_wait_queue(&khugepaged_wait, &wait);
2006 schedule_timeout_interruptible(
2008 khugepaged_scan_sleep_millisecs));
2009 remove_wait_queue(&khugepaged_wait, &wait);
2010 } else if (khugepaged_enabled())
2011 wait_event_interruptible(khugepaged_wait,
2012 khugepaged_wait_event());
2016 static int khugepaged(void *none)
2018 struct mm_slot *mm_slot;
2020 set_user_nice(current, 19);
2022 /* serialize with start_khugepaged() */
2023 mutex_lock(&khugepaged_mutex);
2026 mutex_unlock(&khugepaged_mutex);
2027 BUG_ON(khugepaged_thread != current);
2029 BUG_ON(khugepaged_thread != current);
2031 mutex_lock(&khugepaged_mutex);
2032 if (!khugepaged_enabled())
2036 spin_lock(&khugepaged_mm_lock);
2037 mm_slot = khugepaged_scan.mm_slot;
2038 khugepaged_scan.mm_slot = NULL;
2040 collect_mm_slot(mm_slot);
2041 spin_unlock(&khugepaged_mm_lock);
2043 khugepaged_thread = NULL;
2044 mutex_unlock(&khugepaged_mutex);
2049 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2053 spin_lock(&mm->page_table_lock);
2054 if (unlikely(!pmd_trans_huge(*pmd))) {
2055 spin_unlock(&mm->page_table_lock);
2058 page = pmd_page(*pmd);
2059 VM_BUG_ON(!page_count(page));
2061 spin_unlock(&mm->page_table_lock);
2063 split_huge_page(page);
2066 BUG_ON(pmd_trans_huge(*pmd));