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>
20 #include <asm/pgalloc.h>
24 * By default transparent hugepage support is enabled for all mappings
25 * and khugepaged scans all mappings. Defrag is only invoked by
26 * khugepaged hugepage allocations and by page faults inside
27 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
30 unsigned long transparent_hugepage_flags __read_mostly =
31 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
32 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
34 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
35 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
37 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
40 /* default scan 8*512 pte (or vmas) every 30 second */
41 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
42 static unsigned int khugepaged_pages_collapsed;
43 static unsigned int khugepaged_full_scans;
44 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
45 /* during fragmentation poll the hugepage allocator once every minute */
46 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
47 static struct task_struct *khugepaged_thread __read_mostly;
48 static DEFINE_MUTEX(khugepaged_mutex);
49 static DEFINE_SPINLOCK(khugepaged_mm_lock);
50 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
52 * default collapse hugepages if there is at least one pte mapped like
53 * it would have happened if the vma was large enough during page
56 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
58 static int khugepaged(void *none);
59 static int mm_slots_hash_init(void);
60 static int khugepaged_slab_init(void);
61 static void khugepaged_slab_free(void);
63 #define MM_SLOTS_HASH_HEADS 1024
64 static struct hlist_head *mm_slots_hash __read_mostly;
65 static struct kmem_cache *mm_slot_cache __read_mostly;
68 * struct mm_slot - hash lookup from mm to mm_slot
69 * @hash: hash collision list
70 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
71 * @mm: the mm that this information is valid for
74 struct hlist_node hash;
75 struct list_head mm_node;
80 * struct khugepaged_scan - cursor for scanning
81 * @mm_head: the head of the mm list to scan
82 * @mm_slot: the current mm_slot we are scanning
83 * @address: the next address inside that to be scanned
85 * There is only the one khugepaged_scan instance of this cursor structure.
87 struct khugepaged_scan {
88 struct list_head mm_head;
89 struct mm_slot *mm_slot;
90 unsigned long address;
92 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
96 static int set_recommended_min_free_kbytes(void)
100 unsigned long recommended_min;
101 extern int min_free_kbytes;
103 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
104 &transparent_hugepage_flags) &&
105 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
106 &transparent_hugepage_flags))
109 for_each_populated_zone(zone)
112 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
113 recommended_min = pageblock_nr_pages * nr_zones * 2;
116 * Make sure that on average at least two pageblocks are almost free
117 * of another type, one for a migratetype to fall back to and a
118 * second to avoid subsequent fallbacks of other types There are 3
119 * MIGRATE_TYPES we care about.
121 recommended_min += pageblock_nr_pages * nr_zones *
122 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
124 /* don't ever allow to reserve more than 5% of the lowmem */
125 recommended_min = min(recommended_min,
126 (unsigned long) nr_free_buffer_pages() / 20);
127 recommended_min <<= (PAGE_SHIFT-10);
129 if (recommended_min > min_free_kbytes)
130 min_free_kbytes = recommended_min;
131 setup_per_zone_wmarks();
134 late_initcall(set_recommended_min_free_kbytes);
136 static int start_khugepaged(void)
139 if (khugepaged_enabled()) {
141 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
145 mutex_lock(&khugepaged_mutex);
146 if (!khugepaged_thread)
147 khugepaged_thread = kthread_run(khugepaged, NULL,
149 if (unlikely(IS_ERR(khugepaged_thread))) {
151 "khugepaged: kthread_run(khugepaged) failed\n");
152 err = PTR_ERR(khugepaged_thread);
153 khugepaged_thread = NULL;
155 wakeup = !list_empty(&khugepaged_scan.mm_head);
156 mutex_unlock(&khugepaged_mutex);
158 wake_up_interruptible(&khugepaged_wait);
160 set_recommended_min_free_kbytes();
163 wake_up_interruptible(&khugepaged_wait);
170 static ssize_t double_flag_show(struct kobject *kobj,
171 struct kobj_attribute *attr, char *buf,
172 enum transparent_hugepage_flag enabled,
173 enum transparent_hugepage_flag req_madv)
175 if (test_bit(enabled, &transparent_hugepage_flags)) {
176 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
177 return sprintf(buf, "[always] madvise never\n");
178 } else if (test_bit(req_madv, &transparent_hugepage_flags))
179 return sprintf(buf, "always [madvise] never\n");
181 return sprintf(buf, "always madvise [never]\n");
183 static ssize_t double_flag_store(struct kobject *kobj,
184 struct kobj_attribute *attr,
185 const char *buf, size_t count,
186 enum transparent_hugepage_flag enabled,
187 enum transparent_hugepage_flag req_madv)
189 if (!memcmp("always", buf,
190 min(sizeof("always")-1, count))) {
191 set_bit(enabled, &transparent_hugepage_flags);
192 clear_bit(req_madv, &transparent_hugepage_flags);
193 } else if (!memcmp("madvise", buf,
194 min(sizeof("madvise")-1, count))) {
195 clear_bit(enabled, &transparent_hugepage_flags);
196 set_bit(req_madv, &transparent_hugepage_flags);
197 } else if (!memcmp("never", buf,
198 min(sizeof("never")-1, count))) {
199 clear_bit(enabled, &transparent_hugepage_flags);
200 clear_bit(req_madv, &transparent_hugepage_flags);
207 static ssize_t enabled_show(struct kobject *kobj,
208 struct kobj_attribute *attr, char *buf)
210 return double_flag_show(kobj, attr, buf,
211 TRANSPARENT_HUGEPAGE_FLAG,
212 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
214 static ssize_t enabled_store(struct kobject *kobj,
215 struct kobj_attribute *attr,
216 const char *buf, size_t count)
220 ret = double_flag_store(kobj, attr, buf, count,
221 TRANSPARENT_HUGEPAGE_FLAG,
222 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
225 int err = start_khugepaged();
231 (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
232 &transparent_hugepage_flags) ||
233 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
234 &transparent_hugepage_flags)))
235 set_recommended_min_free_kbytes();
239 static struct kobj_attribute enabled_attr =
240 __ATTR(enabled, 0644, enabled_show, enabled_store);
242 static ssize_t single_flag_show(struct kobject *kobj,
243 struct kobj_attribute *attr, char *buf,
244 enum transparent_hugepage_flag flag)
246 if (test_bit(flag, &transparent_hugepage_flags))
247 return sprintf(buf, "[yes] no\n");
249 return sprintf(buf, "yes [no]\n");
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)
256 if (!memcmp("yes", buf,
257 min(sizeof("yes")-1, count))) {
258 set_bit(flag, &transparent_hugepage_flags);
259 } else if (!memcmp("no", buf,
260 min(sizeof("no")-1, count))) {
261 clear_bit(flag, &transparent_hugepage_flags);
269 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
270 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
271 * memory just to allocate one more hugepage.
273 static ssize_t defrag_show(struct kobject *kobj,
274 struct kobj_attribute *attr, char *buf)
276 return double_flag_show(kobj, attr, buf,
277 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
278 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
280 static ssize_t defrag_store(struct kobject *kobj,
281 struct kobj_attribute *attr,
282 const char *buf, size_t count)
284 return double_flag_store(kobj, attr, buf, count,
285 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
286 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
288 static struct kobj_attribute defrag_attr =
289 __ATTR(defrag, 0644, defrag_show, defrag_store);
291 #ifdef CONFIG_DEBUG_VM
292 static ssize_t debug_cow_show(struct kobject *kobj,
293 struct kobj_attribute *attr, char *buf)
295 return single_flag_show(kobj, attr, buf,
296 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
298 static ssize_t debug_cow_store(struct kobject *kobj,
299 struct kobj_attribute *attr,
300 const char *buf, size_t count)
302 return single_flag_store(kobj, attr, buf, count,
303 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
305 static struct kobj_attribute debug_cow_attr =
306 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
307 #endif /* CONFIG_DEBUG_VM */
309 static struct attribute *hugepage_attr[] = {
312 #ifdef CONFIG_DEBUG_VM
313 &debug_cow_attr.attr,
318 static struct attribute_group hugepage_attr_group = {
319 .attrs = hugepage_attr,
322 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
323 struct kobj_attribute *attr,
326 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
329 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
330 struct kobj_attribute *attr,
331 const char *buf, size_t count)
336 err = strict_strtoul(buf, 10, &msecs);
337 if (err || msecs > UINT_MAX)
340 khugepaged_scan_sleep_millisecs = msecs;
341 wake_up_interruptible(&khugepaged_wait);
345 static struct kobj_attribute scan_sleep_millisecs_attr =
346 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
347 scan_sleep_millisecs_store);
349 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
350 struct kobj_attribute *attr,
353 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
356 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
357 struct kobj_attribute *attr,
358 const char *buf, size_t count)
363 err = strict_strtoul(buf, 10, &msecs);
364 if (err || msecs > UINT_MAX)
367 khugepaged_alloc_sleep_millisecs = msecs;
368 wake_up_interruptible(&khugepaged_wait);
372 static struct kobj_attribute alloc_sleep_millisecs_attr =
373 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
374 alloc_sleep_millisecs_store);
376 static ssize_t pages_to_scan_show(struct kobject *kobj,
377 struct kobj_attribute *attr,
380 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
382 static ssize_t pages_to_scan_store(struct kobject *kobj,
383 struct kobj_attribute *attr,
384 const char *buf, size_t count)
389 err = strict_strtoul(buf, 10, &pages);
390 if (err || !pages || pages > UINT_MAX)
393 khugepaged_pages_to_scan = pages;
397 static struct kobj_attribute pages_to_scan_attr =
398 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
399 pages_to_scan_store);
401 static ssize_t pages_collapsed_show(struct kobject *kobj,
402 struct kobj_attribute *attr,
405 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
407 static struct kobj_attribute pages_collapsed_attr =
408 __ATTR_RO(pages_collapsed);
410 static ssize_t full_scans_show(struct kobject *kobj,
411 struct kobj_attribute *attr,
414 return sprintf(buf, "%u\n", khugepaged_full_scans);
416 static struct kobj_attribute full_scans_attr =
417 __ATTR_RO(full_scans);
419 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
420 struct kobj_attribute *attr, char *buf)
422 return single_flag_show(kobj, attr, buf,
423 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
425 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
426 struct kobj_attribute *attr,
427 const char *buf, size_t count)
429 return single_flag_store(kobj, attr, buf, count,
430 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
432 static struct kobj_attribute khugepaged_defrag_attr =
433 __ATTR(defrag, 0644, khugepaged_defrag_show,
434 khugepaged_defrag_store);
437 * max_ptes_none controls if khugepaged should collapse hugepages over
438 * any unmapped ptes in turn potentially increasing the memory
439 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
440 * reduce the available free memory in the system as it
441 * runs. Increasing max_ptes_none will instead potentially reduce the
442 * free memory in the system during the khugepaged scan.
444 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
445 struct kobj_attribute *attr,
448 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
450 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
451 struct kobj_attribute *attr,
452 const char *buf, size_t count)
455 unsigned long max_ptes_none;
457 err = strict_strtoul(buf, 10, &max_ptes_none);
458 if (err || max_ptes_none > HPAGE_PMD_NR-1)
461 khugepaged_max_ptes_none = max_ptes_none;
465 static struct kobj_attribute khugepaged_max_ptes_none_attr =
466 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
467 khugepaged_max_ptes_none_store);
469 static struct attribute *khugepaged_attr[] = {
470 &khugepaged_defrag_attr.attr,
471 &khugepaged_max_ptes_none_attr.attr,
472 &pages_to_scan_attr.attr,
473 &pages_collapsed_attr.attr,
474 &full_scans_attr.attr,
475 &scan_sleep_millisecs_attr.attr,
476 &alloc_sleep_millisecs_attr.attr,
480 static struct attribute_group khugepaged_attr_group = {
481 .attrs = khugepaged_attr,
482 .name = "khugepaged",
484 #endif /* CONFIG_SYSFS */
486 static int __init hugepage_init(void)
490 static struct kobject *hugepage_kobj;
494 if (!has_transparent_hugepage()) {
495 transparent_hugepage_flags = 0;
501 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
502 if (unlikely(!hugepage_kobj)) {
503 printk(KERN_ERR "hugepage: failed kobject create\n");
507 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
509 printk(KERN_ERR "hugepage: failed register hugeage group\n");
513 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
515 printk(KERN_ERR "hugepage: failed register hugeage group\n");
520 err = khugepaged_slab_init();
524 err = mm_slots_hash_init();
526 khugepaged_slab_free();
531 * By default disable transparent hugepages on smaller systems,
532 * where the extra memory used could hurt more than TLB overhead
533 * is likely to save. The admin can still enable it through /sys.
535 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
536 transparent_hugepage_flags = 0;
540 set_recommended_min_free_kbytes();
545 module_init(hugepage_init)
547 static int __init setup_transparent_hugepage(char *str)
552 if (!strcmp(str, "always")) {
553 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
554 &transparent_hugepage_flags);
555 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
556 &transparent_hugepage_flags);
558 } else if (!strcmp(str, "madvise")) {
559 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
560 &transparent_hugepage_flags);
561 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
562 &transparent_hugepage_flags);
564 } else if (!strcmp(str, "never")) {
565 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
566 &transparent_hugepage_flags);
567 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
568 &transparent_hugepage_flags);
574 "transparent_hugepage= cannot parse, ignored\n");
577 __setup("transparent_hugepage=", setup_transparent_hugepage);
579 static void prepare_pmd_huge_pte(pgtable_t pgtable,
580 struct mm_struct *mm)
582 assert_spin_locked(&mm->page_table_lock);
585 if (!mm->pmd_huge_pte)
586 INIT_LIST_HEAD(&pgtable->lru);
588 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
589 mm->pmd_huge_pte = pgtable;
592 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
594 if (likely(vma->vm_flags & VM_WRITE))
595 pmd = pmd_mkwrite(pmd);
599 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
600 struct vm_area_struct *vma,
601 unsigned long haddr, pmd_t *pmd,
607 VM_BUG_ON(!PageCompound(page));
608 pgtable = pte_alloc_one(mm, haddr);
609 if (unlikely(!pgtable)) {
610 mem_cgroup_uncharge_page(page);
615 clear_huge_page(page, haddr, HPAGE_PMD_NR);
616 __SetPageUptodate(page);
618 spin_lock(&mm->page_table_lock);
619 if (unlikely(!pmd_none(*pmd))) {
620 spin_unlock(&mm->page_table_lock);
621 mem_cgroup_uncharge_page(page);
623 pte_free(mm, pgtable);
626 entry = mk_pmd(page, vma->vm_page_prot);
627 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
628 entry = pmd_mkhuge(entry);
630 * The spinlocking to take the lru_lock inside
631 * page_add_new_anon_rmap() acts as a full memory
632 * barrier to be sure clear_huge_page writes become
633 * visible after the set_pmd_at() write.
635 page_add_new_anon_rmap(page, vma, haddr);
636 set_pmd_at(mm, haddr, pmd, entry);
637 prepare_pmd_huge_pte(pgtable, mm);
638 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
639 spin_unlock(&mm->page_table_lock);
645 static inline gfp_t alloc_hugepage_gfpmask(int defrag)
647 return GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT);
650 static inline struct page *alloc_hugepage_vma(int defrag,
651 struct vm_area_struct *vma,
654 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag),
655 HPAGE_PMD_ORDER, vma, haddr);
659 static inline struct page *alloc_hugepage(int defrag)
661 return alloc_pages(alloc_hugepage_gfpmask(defrag),
666 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
667 unsigned long address, pmd_t *pmd,
671 unsigned long haddr = address & HPAGE_PMD_MASK;
674 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
675 if (unlikely(anon_vma_prepare(vma)))
677 if (unlikely(khugepaged_enter(vma)))
679 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
683 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
688 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
692 * Use __pte_alloc instead of pte_alloc_map, because we can't
693 * run pte_offset_map on the pmd, if an huge pmd could
694 * materialize from under us from a different thread.
696 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
698 /* if an huge pmd materialized from under us just retry later */
699 if (unlikely(pmd_trans_huge(*pmd)))
702 * A regular pmd is established and it can't morph into a huge pmd
703 * from under us anymore at this point because we hold the mmap_sem
704 * read mode and khugepaged takes it in write mode. So now it's
705 * safe to run pte_offset_map().
707 pte = pte_offset_map(pmd, address);
708 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
711 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
712 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
713 struct vm_area_struct *vma)
715 struct page *src_page;
721 pgtable = pte_alloc_one(dst_mm, addr);
722 if (unlikely(!pgtable))
725 spin_lock(&dst_mm->page_table_lock);
726 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
730 if (unlikely(!pmd_trans_huge(pmd))) {
731 pte_free(dst_mm, pgtable);
734 if (unlikely(pmd_trans_splitting(pmd))) {
735 /* split huge page running from under us */
736 spin_unlock(&src_mm->page_table_lock);
737 spin_unlock(&dst_mm->page_table_lock);
738 pte_free(dst_mm, pgtable);
740 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
743 src_page = pmd_page(pmd);
744 VM_BUG_ON(!PageHead(src_page));
746 page_dup_rmap(src_page);
747 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
749 pmdp_set_wrprotect(src_mm, addr, src_pmd);
750 pmd = pmd_mkold(pmd_wrprotect(pmd));
751 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
752 prepare_pmd_huge_pte(pgtable, dst_mm);
756 spin_unlock(&src_mm->page_table_lock);
757 spin_unlock(&dst_mm->page_table_lock);
762 /* no "address" argument so destroys page coloring of some arch */
763 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
767 assert_spin_locked(&mm->page_table_lock);
770 pgtable = mm->pmd_huge_pte;
771 if (list_empty(&pgtable->lru))
772 mm->pmd_huge_pte = NULL;
774 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
776 list_del(&pgtable->lru);
781 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
782 struct vm_area_struct *vma,
783 unsigned long address,
784 pmd_t *pmd, pmd_t orig_pmd,
793 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
795 if (unlikely(!pages)) {
800 for (i = 0; i < HPAGE_PMD_NR; i++) {
801 pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
803 if (unlikely(!pages[i] ||
804 mem_cgroup_newpage_charge(pages[i], mm,
808 mem_cgroup_uncharge_start();
810 mem_cgroup_uncharge_page(pages[i]);
813 mem_cgroup_uncharge_end();
820 for (i = 0; i < HPAGE_PMD_NR; i++) {
821 copy_user_highpage(pages[i], page + i,
822 haddr + PAGE_SHIFT*i, vma);
823 __SetPageUptodate(pages[i]);
827 spin_lock(&mm->page_table_lock);
828 if (unlikely(!pmd_same(*pmd, orig_pmd)))
830 VM_BUG_ON(!PageHead(page));
832 pmdp_clear_flush_notify(vma, haddr, pmd);
833 /* leave pmd empty until pte is filled */
835 pgtable = get_pmd_huge_pte(mm);
836 pmd_populate(mm, &_pmd, pgtable);
838 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
840 entry = mk_pte(pages[i], vma->vm_page_prot);
841 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
842 page_add_new_anon_rmap(pages[i], vma, haddr);
843 pte = pte_offset_map(&_pmd, haddr);
844 VM_BUG_ON(!pte_none(*pte));
845 set_pte_at(mm, haddr, pte, entry);
851 smp_wmb(); /* make pte visible before pmd */
852 pmd_populate(mm, pmd, pgtable);
853 page_remove_rmap(page);
854 spin_unlock(&mm->page_table_lock);
856 ret |= VM_FAULT_WRITE;
863 spin_unlock(&mm->page_table_lock);
864 mem_cgroup_uncharge_start();
865 for (i = 0; i < HPAGE_PMD_NR; i++) {
866 mem_cgroup_uncharge_page(pages[i]);
869 mem_cgroup_uncharge_end();
874 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
875 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
878 struct page *page, *new_page;
881 VM_BUG_ON(!vma->anon_vma);
882 spin_lock(&mm->page_table_lock);
883 if (unlikely(!pmd_same(*pmd, orig_pmd)))
886 page = pmd_page(orig_pmd);
887 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
888 haddr = address & HPAGE_PMD_MASK;
889 if (page_mapcount(page) == 1) {
891 entry = pmd_mkyoung(orig_pmd);
892 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
893 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
894 update_mmu_cache(vma, address, entry);
895 ret |= VM_FAULT_WRITE;
899 spin_unlock(&mm->page_table_lock);
901 if (transparent_hugepage_enabled(vma) &&
902 !transparent_hugepage_debug_cow())
903 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
908 if (unlikely(!new_page)) {
909 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
910 pmd, orig_pmd, page, haddr);
915 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
922 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
923 __SetPageUptodate(new_page);
925 spin_lock(&mm->page_table_lock);
927 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
928 mem_cgroup_uncharge_page(new_page);
932 VM_BUG_ON(!PageHead(page));
933 entry = mk_pmd(new_page, vma->vm_page_prot);
934 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
935 entry = pmd_mkhuge(entry);
936 pmdp_clear_flush_notify(vma, haddr, pmd);
937 page_add_new_anon_rmap(new_page, vma, haddr);
938 set_pmd_at(mm, haddr, pmd, entry);
939 update_mmu_cache(vma, address, entry);
940 page_remove_rmap(page);
942 ret |= VM_FAULT_WRITE;
945 spin_unlock(&mm->page_table_lock);
950 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
955 struct page *page = NULL;
957 assert_spin_locked(&mm->page_table_lock);
959 if (flags & FOLL_WRITE && !pmd_write(*pmd))
962 page = pmd_page(*pmd);
963 VM_BUG_ON(!PageHead(page));
964 if (flags & FOLL_TOUCH) {
967 * We should set the dirty bit only for FOLL_WRITE but
968 * for now the dirty bit in the pmd is meaningless.
969 * And if the dirty bit will become meaningful and
970 * we'll only set it with FOLL_WRITE, an atomic
971 * set_bit will be required on the pmd to set the
972 * young bit, instead of the current set_pmd_at.
974 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
975 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
977 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
978 VM_BUG_ON(!PageCompound(page));
979 if (flags & FOLL_GET)
986 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
991 spin_lock(&tlb->mm->page_table_lock);
992 if (likely(pmd_trans_huge(*pmd))) {
993 if (unlikely(pmd_trans_splitting(*pmd))) {
994 spin_unlock(&tlb->mm->page_table_lock);
995 wait_split_huge_page(vma->anon_vma,
1000 pgtable = get_pmd_huge_pte(tlb->mm);
1001 page = pmd_page(*pmd);
1003 page_remove_rmap(page);
1004 VM_BUG_ON(page_mapcount(page) < 0);
1005 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1006 VM_BUG_ON(!PageHead(page));
1007 spin_unlock(&tlb->mm->page_table_lock);
1008 tlb_remove_page(tlb, page);
1009 pte_free(tlb->mm, pgtable);
1013 spin_unlock(&tlb->mm->page_table_lock);
1018 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1019 unsigned long addr, unsigned long end,
1024 spin_lock(&vma->vm_mm->page_table_lock);
1025 if (likely(pmd_trans_huge(*pmd))) {
1026 ret = !pmd_trans_splitting(*pmd);
1027 spin_unlock(&vma->vm_mm->page_table_lock);
1029 wait_split_huge_page(vma->anon_vma, pmd);
1032 * All logical pages in the range are present
1033 * if backed by a huge page.
1035 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1038 spin_unlock(&vma->vm_mm->page_table_lock);
1043 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1044 unsigned long addr, pgprot_t newprot)
1046 struct mm_struct *mm = vma->vm_mm;
1049 spin_lock(&mm->page_table_lock);
1050 if (likely(pmd_trans_huge(*pmd))) {
1051 if (unlikely(pmd_trans_splitting(*pmd))) {
1052 spin_unlock(&mm->page_table_lock);
1053 wait_split_huge_page(vma->anon_vma, pmd);
1057 entry = pmdp_get_and_clear(mm, addr, pmd);
1058 entry = pmd_modify(entry, newprot);
1059 set_pmd_at(mm, addr, pmd, entry);
1060 spin_unlock(&vma->vm_mm->page_table_lock);
1061 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1065 spin_unlock(&vma->vm_mm->page_table_lock);
1070 pmd_t *page_check_address_pmd(struct page *page,
1071 struct mm_struct *mm,
1072 unsigned long address,
1073 enum page_check_address_pmd_flag flag)
1077 pmd_t *pmd, *ret = NULL;
1079 if (address & ~HPAGE_PMD_MASK)
1082 pgd = pgd_offset(mm, address);
1083 if (!pgd_present(*pgd))
1086 pud = pud_offset(pgd, address);
1087 if (!pud_present(*pud))
1090 pmd = pmd_offset(pud, address);
1093 if (pmd_page(*pmd) != page)
1096 * split_vma() may create temporary aliased mappings. There is
1097 * no risk as long as all huge pmd are found and have their
1098 * splitting bit set before __split_huge_page_refcount
1099 * runs. Finding the same huge pmd more than once during the
1100 * same rmap walk is not a problem.
1102 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1103 pmd_trans_splitting(*pmd))
1105 if (pmd_trans_huge(*pmd)) {
1106 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1107 !pmd_trans_splitting(*pmd));
1114 static int __split_huge_page_splitting(struct page *page,
1115 struct vm_area_struct *vma,
1116 unsigned long address)
1118 struct mm_struct *mm = vma->vm_mm;
1122 spin_lock(&mm->page_table_lock);
1123 pmd = page_check_address_pmd(page, mm, address,
1124 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1127 * We can't temporarily set the pmd to null in order
1128 * to split it, the pmd must remain marked huge at all
1129 * times or the VM won't take the pmd_trans_huge paths
1130 * and it won't wait on the anon_vma->root->lock to
1131 * serialize against split_huge_page*.
1133 pmdp_splitting_flush_notify(vma, address, pmd);
1136 spin_unlock(&mm->page_table_lock);
1141 static void __split_huge_page_refcount(struct page *page)
1144 unsigned long head_index = page->index;
1145 struct zone *zone = page_zone(page);
1147 /* prevent PageLRU to go away from under us, and freeze lru stats */
1148 spin_lock_irq(&zone->lru_lock);
1149 compound_lock(page);
1151 for (i = 1; i < HPAGE_PMD_NR; i++) {
1152 struct page *page_tail = page + i;
1154 /* tail_page->_count cannot change */
1155 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1156 BUG_ON(page_count(page) <= 0);
1157 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1158 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1160 /* after clearing PageTail the gup refcount can be released */
1163 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1164 page_tail->flags |= (page->flags &
1165 ((1L << PG_referenced) |
1166 (1L << PG_swapbacked) |
1167 (1L << PG_mlocked) |
1168 (1L << PG_uptodate)));
1169 page_tail->flags |= (1L << PG_dirty);
1172 * 1) clear PageTail before overwriting first_page
1173 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1178 * __split_huge_page_splitting() already set the
1179 * splitting bit in all pmd that could map this
1180 * hugepage, that will ensure no CPU can alter the
1181 * mapcount on the head page. The mapcount is only
1182 * accounted in the head page and it has to be
1183 * transferred to all tail pages in the below code. So
1184 * for this code to be safe, the split the mapcount
1185 * can't change. But that doesn't mean userland can't
1186 * keep changing and reading the page contents while
1187 * we transfer the mapcount, so the pmd splitting
1188 * status is achieved setting a reserved bit in the
1189 * pmd, not by clearing the present bit.
1191 BUG_ON(page_mapcount(page_tail));
1192 page_tail->_mapcount = page->_mapcount;
1194 BUG_ON(page_tail->mapping);
1195 page_tail->mapping = page->mapping;
1197 page_tail->index = ++head_index;
1199 BUG_ON(!PageAnon(page_tail));
1200 BUG_ON(!PageUptodate(page_tail));
1201 BUG_ON(!PageDirty(page_tail));
1202 BUG_ON(!PageSwapBacked(page_tail));
1204 lru_add_page_tail(zone, page, page_tail);
1207 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1208 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1210 ClearPageCompound(page);
1211 compound_unlock(page);
1212 spin_unlock_irq(&zone->lru_lock);
1214 for (i = 1; i < HPAGE_PMD_NR; i++) {
1215 struct page *page_tail = page + i;
1216 BUG_ON(page_count(page_tail) <= 0);
1218 * Tail pages may be freed if there wasn't any mapping
1219 * like if add_to_swap() is running on a lru page that
1220 * had its mapping zapped. And freeing these pages
1221 * requires taking the lru_lock so we do the put_page
1222 * of the tail pages after the split is complete.
1224 put_page(page_tail);
1228 * Only the head page (now become a regular page) is required
1229 * to be pinned by the caller.
1231 BUG_ON(page_count(page) <= 0);
1234 static int __split_huge_page_map(struct page *page,
1235 struct vm_area_struct *vma,
1236 unsigned long address)
1238 struct mm_struct *mm = vma->vm_mm;
1242 unsigned long haddr;
1244 spin_lock(&mm->page_table_lock);
1245 pmd = page_check_address_pmd(page, mm, address,
1246 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1248 pgtable = get_pmd_huge_pte(mm);
1249 pmd_populate(mm, &_pmd, pgtable);
1251 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1252 i++, haddr += PAGE_SIZE) {
1254 BUG_ON(PageCompound(page+i));
1255 entry = mk_pte(page + i, vma->vm_page_prot);
1256 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1257 if (!pmd_write(*pmd))
1258 entry = pte_wrprotect(entry);
1260 BUG_ON(page_mapcount(page) != 1);
1261 if (!pmd_young(*pmd))
1262 entry = pte_mkold(entry);
1263 pte = pte_offset_map(&_pmd, haddr);
1264 BUG_ON(!pte_none(*pte));
1265 set_pte_at(mm, haddr, pte, entry);
1270 smp_wmb(); /* make pte visible before pmd */
1272 * Up to this point the pmd is present and huge and
1273 * userland has the whole access to the hugepage
1274 * during the split (which happens in place). If we
1275 * overwrite the pmd with the not-huge version
1276 * pointing to the pte here (which of course we could
1277 * if all CPUs were bug free), userland could trigger
1278 * a small page size TLB miss on the small sized TLB
1279 * while the hugepage TLB entry is still established
1280 * in the huge TLB. Some CPU doesn't like that. See
1281 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1282 * Erratum 383 on page 93. Intel should be safe but is
1283 * also warns that it's only safe if the permission
1284 * and cache attributes of the two entries loaded in
1285 * the two TLB is identical (which should be the case
1286 * here). But it is generally safer to never allow
1287 * small and huge TLB entries for the same virtual
1288 * address to be loaded simultaneously. So instead of
1289 * doing "pmd_populate(); flush_tlb_range();" we first
1290 * mark the current pmd notpresent (atomically because
1291 * here the pmd_trans_huge and pmd_trans_splitting
1292 * must remain set at all times on the pmd until the
1293 * split is complete for this pmd), then we flush the
1294 * SMP TLB and finally we write the non-huge version
1295 * of the pmd entry with pmd_populate.
1297 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1298 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1299 pmd_populate(mm, pmd, pgtable);
1302 spin_unlock(&mm->page_table_lock);
1307 /* must be called with anon_vma->root->lock hold */
1308 static void __split_huge_page(struct page *page,
1309 struct anon_vma *anon_vma)
1311 int mapcount, mapcount2;
1312 struct anon_vma_chain *avc;
1314 BUG_ON(!PageHead(page));
1315 BUG_ON(PageTail(page));
1318 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1319 struct vm_area_struct *vma = avc->vma;
1320 unsigned long addr = vma_address(page, vma);
1321 BUG_ON(is_vma_temporary_stack(vma));
1322 if (addr == -EFAULT)
1324 mapcount += __split_huge_page_splitting(page, vma, addr);
1327 * It is critical that new vmas are added to the tail of the
1328 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1329 * and establishes a child pmd before
1330 * __split_huge_page_splitting() freezes the parent pmd (so if
1331 * we fail to prevent copy_huge_pmd() from running until the
1332 * whole __split_huge_page() is complete), we will still see
1333 * the newly established pmd of the child later during the
1334 * walk, to be able to set it as pmd_trans_splitting too.
1336 if (mapcount != page_mapcount(page))
1337 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1338 mapcount, page_mapcount(page));
1339 BUG_ON(mapcount != page_mapcount(page));
1341 __split_huge_page_refcount(page);
1344 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1345 struct vm_area_struct *vma = avc->vma;
1346 unsigned long addr = vma_address(page, vma);
1347 BUG_ON(is_vma_temporary_stack(vma));
1348 if (addr == -EFAULT)
1350 mapcount2 += __split_huge_page_map(page, vma, addr);
1352 if (mapcount != mapcount2)
1353 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1354 mapcount, mapcount2, page_mapcount(page));
1355 BUG_ON(mapcount != mapcount2);
1358 int split_huge_page(struct page *page)
1360 struct anon_vma *anon_vma;
1363 BUG_ON(!PageAnon(page));
1364 anon_vma = page_lock_anon_vma(page);
1368 if (!PageCompound(page))
1371 BUG_ON(!PageSwapBacked(page));
1372 __split_huge_page(page, anon_vma);
1374 BUG_ON(PageCompound(page));
1376 page_unlock_anon_vma(anon_vma);
1381 int hugepage_madvise(unsigned long *vm_flags)
1384 * Be somewhat over-protective like KSM for now!
1386 if (*vm_flags & (VM_HUGEPAGE | VM_SHARED | VM_MAYSHARE |
1387 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1388 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1389 VM_MIXEDMAP | VM_SAO))
1392 *vm_flags |= VM_HUGEPAGE;
1397 static int __init khugepaged_slab_init(void)
1399 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1400 sizeof(struct mm_slot),
1401 __alignof__(struct mm_slot), 0, NULL);
1408 static void __init khugepaged_slab_free(void)
1410 kmem_cache_destroy(mm_slot_cache);
1411 mm_slot_cache = NULL;
1414 static inline struct mm_slot *alloc_mm_slot(void)
1416 if (!mm_slot_cache) /* initialization failed */
1418 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1421 static inline void free_mm_slot(struct mm_slot *mm_slot)
1423 kmem_cache_free(mm_slot_cache, mm_slot);
1426 static int __init mm_slots_hash_init(void)
1428 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1436 static void __init mm_slots_hash_free(void)
1438 kfree(mm_slots_hash);
1439 mm_slots_hash = NULL;
1443 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1445 struct mm_slot *mm_slot;
1446 struct hlist_head *bucket;
1447 struct hlist_node *node;
1449 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1450 % MM_SLOTS_HASH_HEADS];
1451 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1452 if (mm == mm_slot->mm)
1458 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1459 struct mm_slot *mm_slot)
1461 struct hlist_head *bucket;
1463 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1464 % MM_SLOTS_HASH_HEADS];
1466 hlist_add_head(&mm_slot->hash, bucket);
1469 static inline int khugepaged_test_exit(struct mm_struct *mm)
1471 return atomic_read(&mm->mm_users) == 0;
1474 int __khugepaged_enter(struct mm_struct *mm)
1476 struct mm_slot *mm_slot;
1479 mm_slot = alloc_mm_slot();
1483 /* __khugepaged_exit() must not run from under us */
1484 VM_BUG_ON(khugepaged_test_exit(mm));
1485 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1486 free_mm_slot(mm_slot);
1490 spin_lock(&khugepaged_mm_lock);
1491 insert_to_mm_slots_hash(mm, mm_slot);
1493 * Insert just behind the scanning cursor, to let the area settle
1496 wakeup = list_empty(&khugepaged_scan.mm_head);
1497 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1498 spin_unlock(&khugepaged_mm_lock);
1500 atomic_inc(&mm->mm_count);
1502 wake_up_interruptible(&khugepaged_wait);
1507 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1509 unsigned long hstart, hend;
1512 * Not yet faulted in so we will register later in the
1513 * page fault if needed.
1516 if (vma->vm_file || vma->vm_ops)
1517 /* khugepaged not yet working on file or special mappings */
1519 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1520 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1521 hend = vma->vm_end & HPAGE_PMD_MASK;
1523 return khugepaged_enter(vma);
1527 void __khugepaged_exit(struct mm_struct *mm)
1529 struct mm_slot *mm_slot;
1532 spin_lock(&khugepaged_mm_lock);
1533 mm_slot = get_mm_slot(mm);
1534 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1535 hlist_del(&mm_slot->hash);
1536 list_del(&mm_slot->mm_node);
1541 spin_unlock(&khugepaged_mm_lock);
1542 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1543 free_mm_slot(mm_slot);
1545 } else if (mm_slot) {
1546 spin_unlock(&khugepaged_mm_lock);
1548 * This is required to serialize against
1549 * khugepaged_test_exit() (which is guaranteed to run
1550 * under mmap sem read mode). Stop here (after we
1551 * return all pagetables will be destroyed) until
1552 * khugepaged has finished working on the pagetables
1553 * under the mmap_sem.
1555 down_write(&mm->mmap_sem);
1556 up_write(&mm->mmap_sem);
1558 spin_unlock(&khugepaged_mm_lock);
1561 static void release_pte_page(struct page *page)
1563 /* 0 stands for page_is_file_cache(page) == false */
1564 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1566 putback_lru_page(page);
1569 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1571 while (--_pte >= pte) {
1572 pte_t pteval = *_pte;
1573 if (!pte_none(pteval))
1574 release_pte_page(pte_page(pteval));
1578 static void release_all_pte_pages(pte_t *pte)
1580 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1583 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1584 unsigned long address,
1589 int referenced = 0, isolated = 0, none = 0;
1590 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1591 _pte++, address += PAGE_SIZE) {
1592 pte_t pteval = *_pte;
1593 if (pte_none(pteval)) {
1594 if (++none <= khugepaged_max_ptes_none)
1597 release_pte_pages(pte, _pte);
1601 if (!pte_present(pteval) || !pte_write(pteval)) {
1602 release_pte_pages(pte, _pte);
1605 page = vm_normal_page(vma, address, pteval);
1606 if (unlikely(!page)) {
1607 release_pte_pages(pte, _pte);
1610 VM_BUG_ON(PageCompound(page));
1611 BUG_ON(!PageAnon(page));
1612 VM_BUG_ON(!PageSwapBacked(page));
1614 /* cannot use mapcount: can't collapse if there's a gup pin */
1615 if (page_count(page) != 1) {
1616 release_pte_pages(pte, _pte);
1620 * We can do it before isolate_lru_page because the
1621 * page can't be freed from under us. NOTE: PG_lock
1622 * is needed to serialize against split_huge_page
1623 * when invoked from the VM.
1625 if (!trylock_page(page)) {
1626 release_pte_pages(pte, _pte);
1630 * Isolate the page to avoid collapsing an hugepage
1631 * currently in use by the VM.
1633 if (isolate_lru_page(page)) {
1635 release_pte_pages(pte, _pte);
1638 /* 0 stands for page_is_file_cache(page) == false */
1639 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1640 VM_BUG_ON(!PageLocked(page));
1641 VM_BUG_ON(PageLRU(page));
1643 /* If there is no mapped pte young don't collapse the page */
1644 if (pte_young(pteval) || PageReferenced(page) ||
1645 mmu_notifier_test_young(vma->vm_mm, address))
1648 if (unlikely(!referenced))
1649 release_all_pte_pages(pte);
1656 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1657 struct vm_area_struct *vma,
1658 unsigned long address,
1662 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1663 pte_t pteval = *_pte;
1664 struct page *src_page;
1666 if (pte_none(pteval)) {
1667 clear_user_highpage(page, address);
1668 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1670 src_page = pte_page(pteval);
1671 copy_user_highpage(page, src_page, address, vma);
1672 VM_BUG_ON(page_mapcount(src_page) != 1);
1673 VM_BUG_ON(page_count(src_page) != 2);
1674 release_pte_page(src_page);
1676 * ptl mostly unnecessary, but preempt has to
1677 * be disabled to update the per-cpu stats
1678 * inside page_remove_rmap().
1682 * paravirt calls inside pte_clear here are
1685 pte_clear(vma->vm_mm, address, _pte);
1686 page_remove_rmap(src_page);
1688 free_page_and_swap_cache(src_page);
1691 address += PAGE_SIZE;
1696 static void collapse_huge_page(struct mm_struct *mm,
1697 unsigned long address,
1698 struct page **hpage,
1699 struct vm_area_struct *vma)
1706 struct page *new_page;
1709 unsigned long hstart, hend;
1711 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1718 * Allocate the page while the vma is still valid and under
1719 * the mmap_sem read mode so there is no memory allocation
1720 * later when we take the mmap_sem in write mode. This is more
1721 * friendly behavior (OTOH it may actually hide bugs) to
1722 * filesystems in userland with daemons allocating memory in
1723 * the userland I/O paths. Allocating memory with the
1724 * mmap_sem in read mode is good idea also to allow greater
1727 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address);
1728 if (unlikely(!new_page)) {
1729 up_read(&mm->mmap_sem);
1730 *hpage = ERR_PTR(-ENOMEM);
1734 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1735 up_read(&mm->mmap_sem);
1740 /* after allocating the hugepage upgrade to mmap_sem write mode */
1741 up_read(&mm->mmap_sem);
1744 * Prevent all access to pagetables with the exception of
1745 * gup_fast later hanlded by the ptep_clear_flush and the VM
1746 * handled by the anon_vma lock + PG_lock.
1748 down_write(&mm->mmap_sem);
1749 if (unlikely(khugepaged_test_exit(mm)))
1752 vma = find_vma(mm, address);
1753 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1754 hend = vma->vm_end & HPAGE_PMD_MASK;
1755 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1758 if (!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always())
1761 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1762 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
1764 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1766 pgd = pgd_offset(mm, address);
1767 if (!pgd_present(*pgd))
1770 pud = pud_offset(pgd, address);
1771 if (!pud_present(*pud))
1774 pmd = pmd_offset(pud, address);
1775 /* pmd can't go away or become huge under us */
1776 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1779 anon_vma_lock(vma->anon_vma);
1781 pte = pte_offset_map(pmd, address);
1782 ptl = pte_lockptr(mm, pmd);
1784 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1786 * After this gup_fast can't run anymore. This also removes
1787 * any huge TLB entry from the CPU so we won't allow
1788 * huge and small TLB entries for the same virtual address
1789 * to avoid the risk of CPU bugs in that area.
1791 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1792 spin_unlock(&mm->page_table_lock);
1795 isolated = __collapse_huge_page_isolate(vma, address, pte);
1799 if (unlikely(!isolated)) {
1800 spin_lock(&mm->page_table_lock);
1801 BUG_ON(!pmd_none(*pmd));
1802 set_pmd_at(mm, address, pmd, _pmd);
1803 spin_unlock(&mm->page_table_lock);
1804 anon_vma_unlock(vma->anon_vma);
1805 mem_cgroup_uncharge_page(new_page);
1810 * All pages are isolated and locked so anon_vma rmap
1811 * can't run anymore.
1813 anon_vma_unlock(vma->anon_vma);
1815 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1816 __SetPageUptodate(new_page);
1817 pgtable = pmd_pgtable(_pmd);
1818 VM_BUG_ON(page_count(pgtable) != 1);
1819 VM_BUG_ON(page_mapcount(pgtable) != 0);
1821 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1822 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1823 _pmd = pmd_mkhuge(_pmd);
1826 * spin_lock() below is not the equivalent of smp_wmb(), so
1827 * this is needed to avoid the copy_huge_page writes to become
1828 * visible after the set_pmd_at() write.
1832 spin_lock(&mm->page_table_lock);
1833 BUG_ON(!pmd_none(*pmd));
1834 page_add_new_anon_rmap(new_page, vma, address);
1835 set_pmd_at(mm, address, pmd, _pmd);
1836 update_mmu_cache(vma, address, entry);
1837 prepare_pmd_huge_pte(pgtable, mm);
1839 spin_unlock(&mm->page_table_lock);
1844 khugepaged_pages_collapsed++;
1846 up_write(&mm->mmap_sem);
1856 static int khugepaged_scan_pmd(struct mm_struct *mm,
1857 struct vm_area_struct *vma,
1858 unsigned long address,
1859 struct page **hpage)
1865 int ret = 0, referenced = 0, none = 0;
1867 unsigned long _address;
1870 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1872 pgd = pgd_offset(mm, address);
1873 if (!pgd_present(*pgd))
1876 pud = pud_offset(pgd, address);
1877 if (!pud_present(*pud))
1880 pmd = pmd_offset(pud, address);
1881 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1884 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1885 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1886 _pte++, _address += PAGE_SIZE) {
1887 pte_t pteval = *_pte;
1888 if (pte_none(pteval)) {
1889 if (++none <= khugepaged_max_ptes_none)
1894 if (!pte_present(pteval) || !pte_write(pteval))
1896 page = vm_normal_page(vma, _address, pteval);
1897 if (unlikely(!page))
1899 VM_BUG_ON(PageCompound(page));
1900 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1902 /* cannot use mapcount: can't collapse if there's a gup pin */
1903 if (page_count(page) != 1)
1905 if (pte_young(pteval) || PageReferenced(page) ||
1906 mmu_notifier_test_young(vma->vm_mm, address))
1912 pte_unmap_unlock(pte, ptl);
1914 /* collapse_huge_page will return with the mmap_sem released */
1915 collapse_huge_page(mm, address, hpage, vma);
1920 static void collect_mm_slot(struct mm_slot *mm_slot)
1922 struct mm_struct *mm = mm_slot->mm;
1924 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1926 if (khugepaged_test_exit(mm)) {
1928 hlist_del(&mm_slot->hash);
1929 list_del(&mm_slot->mm_node);
1932 * Not strictly needed because the mm exited already.
1934 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1937 /* khugepaged_mm_lock actually not necessary for the below */
1938 free_mm_slot(mm_slot);
1943 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1944 struct page **hpage)
1946 struct mm_slot *mm_slot;
1947 struct mm_struct *mm;
1948 struct vm_area_struct *vma;
1952 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1954 if (khugepaged_scan.mm_slot)
1955 mm_slot = khugepaged_scan.mm_slot;
1957 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1958 struct mm_slot, mm_node);
1959 khugepaged_scan.address = 0;
1960 khugepaged_scan.mm_slot = mm_slot;
1962 spin_unlock(&khugepaged_mm_lock);
1965 down_read(&mm->mmap_sem);
1966 if (unlikely(khugepaged_test_exit(mm)))
1969 vma = find_vma(mm, khugepaged_scan.address);
1972 for (; vma; vma = vma->vm_next) {
1973 unsigned long hstart, hend;
1976 if (unlikely(khugepaged_test_exit(mm))) {
1981 if (!(vma->vm_flags & VM_HUGEPAGE) &&
1982 !khugepaged_always()) {
1987 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1988 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) {
1989 khugepaged_scan.address = vma->vm_end;
1993 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1995 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1996 hend = vma->vm_end & HPAGE_PMD_MASK;
1997 if (hstart >= hend) {
2001 if (khugepaged_scan.address < hstart)
2002 khugepaged_scan.address = hstart;
2003 if (khugepaged_scan.address > hend) {
2004 khugepaged_scan.address = hend + HPAGE_PMD_SIZE;
2008 BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2010 while (khugepaged_scan.address < hend) {
2013 if (unlikely(khugepaged_test_exit(mm)))
2014 goto breakouterloop;
2016 VM_BUG_ON(khugepaged_scan.address < hstart ||
2017 khugepaged_scan.address + HPAGE_PMD_SIZE >
2019 ret = khugepaged_scan_pmd(mm, vma,
2020 khugepaged_scan.address,
2022 /* move to next address */
2023 khugepaged_scan.address += HPAGE_PMD_SIZE;
2024 progress += HPAGE_PMD_NR;
2026 /* we released mmap_sem so break loop */
2027 goto breakouterloop_mmap_sem;
2028 if (progress >= pages)
2029 goto breakouterloop;
2033 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2034 breakouterloop_mmap_sem:
2036 spin_lock(&khugepaged_mm_lock);
2037 BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2039 * Release the current mm_slot if this mm is about to die, or
2040 * if we scanned all vmas of this mm.
2042 if (khugepaged_test_exit(mm) || !vma) {
2044 * Make sure that if mm_users is reaching zero while
2045 * khugepaged runs here, khugepaged_exit will find
2046 * mm_slot not pointing to the exiting mm.
2048 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2049 khugepaged_scan.mm_slot = list_entry(
2050 mm_slot->mm_node.next,
2051 struct mm_slot, mm_node);
2052 khugepaged_scan.address = 0;
2054 khugepaged_scan.mm_slot = NULL;
2055 khugepaged_full_scans++;
2058 collect_mm_slot(mm_slot);
2064 static int khugepaged_has_work(void)
2066 return !list_empty(&khugepaged_scan.mm_head) &&
2067 khugepaged_enabled();
2070 static int khugepaged_wait_event(void)
2072 return !list_empty(&khugepaged_scan.mm_head) ||
2073 !khugepaged_enabled();
2076 static void khugepaged_do_scan(struct page **hpage)
2078 unsigned int progress = 0, pass_through_head = 0;
2079 unsigned int pages = khugepaged_pages_to_scan;
2081 barrier(); /* write khugepaged_pages_to_scan to local stack */
2083 while (progress < pages) {
2088 *hpage = alloc_hugepage(khugepaged_defrag());
2089 if (unlikely(!*hpage))
2097 if (unlikely(kthread_should_stop() || freezing(current)))
2100 spin_lock(&khugepaged_mm_lock);
2101 if (!khugepaged_scan.mm_slot)
2102 pass_through_head++;
2103 if (khugepaged_has_work() &&
2104 pass_through_head < 2)
2105 progress += khugepaged_scan_mm_slot(pages - progress,
2109 spin_unlock(&khugepaged_mm_lock);
2113 static void khugepaged_alloc_sleep(void)
2116 add_wait_queue(&khugepaged_wait, &wait);
2117 schedule_timeout_interruptible(
2119 khugepaged_alloc_sleep_millisecs));
2120 remove_wait_queue(&khugepaged_wait, &wait);
2124 static struct page *khugepaged_alloc_hugepage(void)
2129 hpage = alloc_hugepage(khugepaged_defrag());
2131 khugepaged_alloc_sleep();
2132 } while (unlikely(!hpage) &&
2133 likely(khugepaged_enabled()));
2138 static void khugepaged_loop(void)
2145 while (likely(khugepaged_enabled())) {
2147 hpage = khugepaged_alloc_hugepage();
2148 if (unlikely(!hpage))
2151 if (IS_ERR(hpage)) {
2152 khugepaged_alloc_sleep();
2157 khugepaged_do_scan(&hpage);
2163 if (unlikely(kthread_should_stop()))
2165 if (khugepaged_has_work()) {
2167 if (!khugepaged_scan_sleep_millisecs)
2169 add_wait_queue(&khugepaged_wait, &wait);
2170 schedule_timeout_interruptible(
2172 khugepaged_scan_sleep_millisecs));
2173 remove_wait_queue(&khugepaged_wait, &wait);
2174 } else if (khugepaged_enabled())
2175 wait_event_freezable(khugepaged_wait,
2176 khugepaged_wait_event());
2180 static int khugepaged(void *none)
2182 struct mm_slot *mm_slot;
2185 set_user_nice(current, 19);
2187 /* serialize with start_khugepaged() */
2188 mutex_lock(&khugepaged_mutex);
2191 mutex_unlock(&khugepaged_mutex);
2192 BUG_ON(khugepaged_thread != current);
2194 BUG_ON(khugepaged_thread != current);
2196 mutex_lock(&khugepaged_mutex);
2197 if (!khugepaged_enabled())
2199 if (unlikely(kthread_should_stop()))
2203 spin_lock(&khugepaged_mm_lock);
2204 mm_slot = khugepaged_scan.mm_slot;
2205 khugepaged_scan.mm_slot = NULL;
2207 collect_mm_slot(mm_slot);
2208 spin_unlock(&khugepaged_mm_lock);
2210 khugepaged_thread = NULL;
2211 mutex_unlock(&khugepaged_mutex);
2216 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2220 spin_lock(&mm->page_table_lock);
2221 if (unlikely(!pmd_trans_huge(*pmd))) {
2222 spin_unlock(&mm->page_table_lock);
2225 page = pmd_page(*pmd);
2226 VM_BUG_ON(!page_count(page));
2228 spin_unlock(&mm->page_table_lock);
2230 split_huge_page(page);
2233 BUG_ON(pmd_trans_huge(*pmd));
2236 static void split_huge_page_address(struct mm_struct *mm,
2237 unsigned long address)
2243 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2245 pgd = pgd_offset(mm, address);
2246 if (!pgd_present(*pgd))
2249 pud = pud_offset(pgd, address);
2250 if (!pud_present(*pud))
2253 pmd = pmd_offset(pud, address);
2254 if (!pmd_present(*pmd))
2257 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2258 * materialize from under us.
2260 split_huge_page_pmd(mm, pmd);
2263 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2264 unsigned long start,
2269 * If the new start address isn't hpage aligned and it could
2270 * previously contain an hugepage: check if we need to split
2273 if (start & ~HPAGE_PMD_MASK &&
2274 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2275 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2276 split_huge_page_address(vma->vm_mm, start);
2279 * If the new end address isn't hpage aligned and it could
2280 * previously contain an hugepage: check if we need to split
2283 if (end & ~HPAGE_PMD_MASK &&
2284 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2285 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2286 split_huge_page_address(vma->vm_mm, end);
2289 * If we're also updating the vma->vm_next->vm_start, if the new
2290 * vm_next->vm_start isn't page aligned and it could previously
2291 * contain an hugepage: check if we need to split an huge pmd.
2293 if (adjust_next > 0) {
2294 struct vm_area_struct *next = vma->vm_next;
2295 unsigned long nstart = next->vm_start;
2296 nstart += adjust_next << PAGE_SHIFT;
2297 if (nstart & ~HPAGE_PMD_MASK &&
2298 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2299 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2300 split_huge_page_address(next->vm_mm, nstart);