1 // SPDX-License-Identifier: GPL-2.0
2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
5 #include <linux/sched.h>
6 #include <linux/sched/mm.h>
7 #include <linux/sched/coredump.h>
8 #include <linux/mmu_notifier.h>
9 #include <linux/rmap.h>
10 #include <linux/swap.h>
11 #include <linux/mm_inline.h>
12 #include <linux/kthread.h>
13 #include <linux/khugepaged.h>
14 #include <linux/freezer.h>
15 #include <linux/mman.h>
16 #include <linux/hashtable.h>
17 #include <linux/userfaultfd_k.h>
18 #include <linux/page_idle.h>
19 #include <linux/page_table_check.h>
20 #include <linux/rcupdate_wait.h>
21 #include <linux/swapops.h>
22 #include <linux/shmem_fs.h>
23 #include <linux/ksm.h>
26 #include <asm/pgalloc.h>
38 SCAN_EXCEED_SHARED_PTE,
41 SCAN_PTE_MAPPED_HUGEPAGE,
43 SCAN_LACK_REFERENCED_PAGE,
56 SCAN_ALLOC_HUGE_PAGE_FAIL,
57 SCAN_CGROUP_CHARGE_FAIL,
59 SCAN_PAGE_HAS_PRIVATE,
65 #define CREATE_TRACE_POINTS
66 #include <trace/events/huge_memory.h>
68 static struct task_struct *khugepaged_thread __read_mostly;
69 static DEFINE_MUTEX(khugepaged_mutex);
71 /* default scan 8*512 pte (or vmas) every 30 second */
72 static unsigned int khugepaged_pages_to_scan __read_mostly;
73 static unsigned int khugepaged_pages_collapsed;
74 static unsigned int khugepaged_full_scans;
75 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
76 /* during fragmentation poll the hugepage allocator once every minute */
77 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
78 static unsigned long khugepaged_sleep_expire;
79 static DEFINE_SPINLOCK(khugepaged_mm_lock);
80 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
82 * default collapse hugepages if there is at least one pte mapped like
83 * it would have happened if the vma was large enough during page
86 * Note that these are only respected if collapse was initiated by khugepaged.
88 static unsigned int khugepaged_max_ptes_none __read_mostly;
89 static unsigned int khugepaged_max_ptes_swap __read_mostly;
90 static unsigned int khugepaged_max_ptes_shared __read_mostly;
92 #define MM_SLOTS_HASH_BITS 10
93 static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
95 static struct kmem_cache *mm_slot_cache __ro_after_init;
97 struct collapse_control {
100 /* Num pages scanned per node */
101 u32 node_load[MAX_NUMNODES];
103 /* nodemask for allocation fallback */
104 nodemask_t alloc_nmask;
108 * struct khugepaged_mm_slot - khugepaged information per mm that is being scanned
109 * @slot: hash lookup from mm to mm_slot
111 struct khugepaged_mm_slot {
116 * struct khugepaged_scan - cursor for scanning
117 * @mm_head: the head of the mm list to scan
118 * @mm_slot: the current mm_slot we are scanning
119 * @address: the next address inside that to be scanned
121 * There is only the one khugepaged_scan instance of this cursor structure.
123 struct khugepaged_scan {
124 struct list_head mm_head;
125 struct khugepaged_mm_slot *mm_slot;
126 unsigned long address;
129 static struct khugepaged_scan khugepaged_scan = {
130 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
134 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
135 struct kobj_attribute *attr,
138 return sysfs_emit(buf, "%u\n", khugepaged_scan_sleep_millisecs);
141 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
142 struct kobj_attribute *attr,
143 const char *buf, size_t count)
148 err = kstrtouint(buf, 10, &msecs);
152 khugepaged_scan_sleep_millisecs = msecs;
153 khugepaged_sleep_expire = 0;
154 wake_up_interruptible(&khugepaged_wait);
158 static struct kobj_attribute scan_sleep_millisecs_attr =
159 __ATTR_RW(scan_sleep_millisecs);
161 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
162 struct kobj_attribute *attr,
165 return sysfs_emit(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
168 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
169 struct kobj_attribute *attr,
170 const char *buf, size_t count)
175 err = kstrtouint(buf, 10, &msecs);
179 khugepaged_alloc_sleep_millisecs = msecs;
180 khugepaged_sleep_expire = 0;
181 wake_up_interruptible(&khugepaged_wait);
185 static struct kobj_attribute alloc_sleep_millisecs_attr =
186 __ATTR_RW(alloc_sleep_millisecs);
188 static ssize_t pages_to_scan_show(struct kobject *kobj,
189 struct kobj_attribute *attr,
192 return sysfs_emit(buf, "%u\n", khugepaged_pages_to_scan);
194 static ssize_t pages_to_scan_store(struct kobject *kobj,
195 struct kobj_attribute *attr,
196 const char *buf, size_t count)
201 err = kstrtouint(buf, 10, &pages);
205 khugepaged_pages_to_scan = pages;
209 static struct kobj_attribute pages_to_scan_attr =
210 __ATTR_RW(pages_to_scan);
212 static ssize_t pages_collapsed_show(struct kobject *kobj,
213 struct kobj_attribute *attr,
216 return sysfs_emit(buf, "%u\n", khugepaged_pages_collapsed);
218 static struct kobj_attribute pages_collapsed_attr =
219 __ATTR_RO(pages_collapsed);
221 static ssize_t full_scans_show(struct kobject *kobj,
222 struct kobj_attribute *attr,
225 return sysfs_emit(buf, "%u\n", khugepaged_full_scans);
227 static struct kobj_attribute full_scans_attr =
228 __ATTR_RO(full_scans);
230 static ssize_t defrag_show(struct kobject *kobj,
231 struct kobj_attribute *attr, char *buf)
233 return single_hugepage_flag_show(kobj, attr, buf,
234 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
236 static ssize_t defrag_store(struct kobject *kobj,
237 struct kobj_attribute *attr,
238 const char *buf, size_t count)
240 return single_hugepage_flag_store(kobj, attr, buf, count,
241 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
243 static struct kobj_attribute khugepaged_defrag_attr =
247 * max_ptes_none controls if khugepaged should collapse hugepages over
248 * any unmapped ptes in turn potentially increasing the memory
249 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
250 * reduce the available free memory in the system as it
251 * runs. Increasing max_ptes_none will instead potentially reduce the
252 * free memory in the system during the khugepaged scan.
254 static ssize_t max_ptes_none_show(struct kobject *kobj,
255 struct kobj_attribute *attr,
258 return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_none);
260 static ssize_t max_ptes_none_store(struct kobject *kobj,
261 struct kobj_attribute *attr,
262 const char *buf, size_t count)
265 unsigned long max_ptes_none;
267 err = kstrtoul(buf, 10, &max_ptes_none);
268 if (err || max_ptes_none > HPAGE_PMD_NR - 1)
271 khugepaged_max_ptes_none = max_ptes_none;
275 static struct kobj_attribute khugepaged_max_ptes_none_attr =
276 __ATTR_RW(max_ptes_none);
278 static ssize_t max_ptes_swap_show(struct kobject *kobj,
279 struct kobj_attribute *attr,
282 return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_swap);
285 static ssize_t max_ptes_swap_store(struct kobject *kobj,
286 struct kobj_attribute *attr,
287 const char *buf, size_t count)
290 unsigned long max_ptes_swap;
292 err = kstrtoul(buf, 10, &max_ptes_swap);
293 if (err || max_ptes_swap > HPAGE_PMD_NR - 1)
296 khugepaged_max_ptes_swap = max_ptes_swap;
301 static struct kobj_attribute khugepaged_max_ptes_swap_attr =
302 __ATTR_RW(max_ptes_swap);
304 static ssize_t max_ptes_shared_show(struct kobject *kobj,
305 struct kobj_attribute *attr,
308 return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_shared);
311 static ssize_t max_ptes_shared_store(struct kobject *kobj,
312 struct kobj_attribute *attr,
313 const char *buf, size_t count)
316 unsigned long max_ptes_shared;
318 err = kstrtoul(buf, 10, &max_ptes_shared);
319 if (err || max_ptes_shared > HPAGE_PMD_NR - 1)
322 khugepaged_max_ptes_shared = max_ptes_shared;
327 static struct kobj_attribute khugepaged_max_ptes_shared_attr =
328 __ATTR_RW(max_ptes_shared);
330 static struct attribute *khugepaged_attr[] = {
331 &khugepaged_defrag_attr.attr,
332 &khugepaged_max_ptes_none_attr.attr,
333 &khugepaged_max_ptes_swap_attr.attr,
334 &khugepaged_max_ptes_shared_attr.attr,
335 &pages_to_scan_attr.attr,
336 &pages_collapsed_attr.attr,
337 &full_scans_attr.attr,
338 &scan_sleep_millisecs_attr.attr,
339 &alloc_sleep_millisecs_attr.attr,
343 struct attribute_group khugepaged_attr_group = {
344 .attrs = khugepaged_attr,
345 .name = "khugepaged",
347 #endif /* CONFIG_SYSFS */
349 int hugepage_madvise(struct vm_area_struct *vma,
350 unsigned long *vm_flags, int advice)
356 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
357 * can't handle this properly after s390_enable_sie, so we simply
358 * ignore the madvise to prevent qemu from causing a SIGSEGV.
360 if (mm_has_pgste(vma->vm_mm))
363 *vm_flags &= ~VM_NOHUGEPAGE;
364 *vm_flags |= VM_HUGEPAGE;
366 * If the vma become good for khugepaged to scan,
367 * register it here without waiting a page fault that
368 * may not happen any time soon.
370 khugepaged_enter_vma(vma, *vm_flags);
372 case MADV_NOHUGEPAGE:
373 *vm_flags &= ~VM_HUGEPAGE;
374 *vm_flags |= VM_NOHUGEPAGE;
376 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
377 * this vma even if we leave the mm registered in khugepaged if
378 * it got registered before VM_NOHUGEPAGE was set.
386 int __init khugepaged_init(void)
388 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
389 sizeof(struct khugepaged_mm_slot),
390 __alignof__(struct khugepaged_mm_slot),
395 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
396 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
397 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
398 khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2;
403 void __init khugepaged_destroy(void)
405 kmem_cache_destroy(mm_slot_cache);
408 static inline int hpage_collapse_test_exit(struct mm_struct *mm)
410 return atomic_read(&mm->mm_users) == 0;
413 static inline int hpage_collapse_test_exit_or_disable(struct mm_struct *mm)
415 return hpage_collapse_test_exit(mm) ||
416 test_bit(MMF_DISABLE_THP, &mm->flags);
419 void __khugepaged_enter(struct mm_struct *mm)
421 struct khugepaged_mm_slot *mm_slot;
422 struct mm_slot *slot;
425 /* __khugepaged_exit() must not run from under us */
426 VM_BUG_ON_MM(hpage_collapse_test_exit(mm), mm);
427 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags)))
430 mm_slot = mm_slot_alloc(mm_slot_cache);
434 slot = &mm_slot->slot;
436 spin_lock(&khugepaged_mm_lock);
437 mm_slot_insert(mm_slots_hash, mm, slot);
439 * Insert just behind the scanning cursor, to let the area settle
442 wakeup = list_empty(&khugepaged_scan.mm_head);
443 list_add_tail(&slot->mm_node, &khugepaged_scan.mm_head);
444 spin_unlock(&khugepaged_mm_lock);
448 wake_up_interruptible(&khugepaged_wait);
451 void khugepaged_enter_vma(struct vm_area_struct *vma,
452 unsigned long vm_flags)
454 if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
455 hugepage_flags_enabled()) {
456 if (thp_vma_allowable_order(vma, vm_flags, false, false, true,
458 __khugepaged_enter(vma->vm_mm);
462 void __khugepaged_exit(struct mm_struct *mm)
464 struct khugepaged_mm_slot *mm_slot;
465 struct mm_slot *slot;
468 spin_lock(&khugepaged_mm_lock);
469 slot = mm_slot_lookup(mm_slots_hash, mm);
470 mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
471 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
472 hash_del(&slot->hash);
473 list_del(&slot->mm_node);
476 spin_unlock(&khugepaged_mm_lock);
479 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
480 mm_slot_free(mm_slot_cache, mm_slot);
482 } else if (mm_slot) {
484 * This is required to serialize against
485 * hpage_collapse_test_exit() (which is guaranteed to run
486 * under mmap sem read mode). Stop here (after we return all
487 * pagetables will be destroyed) until khugepaged has finished
488 * working on the pagetables under the mmap_lock.
491 mmap_write_unlock(mm);
495 static void release_pte_folio(struct folio *folio)
497 node_stat_mod_folio(folio,
498 NR_ISOLATED_ANON + folio_is_file_lru(folio),
499 -folio_nr_pages(folio));
501 folio_putback_lru(folio);
504 static void release_pte_pages(pte_t *pte, pte_t *_pte,
505 struct list_head *compound_pagelist)
507 struct folio *folio, *tmp;
509 while (--_pte >= pte) {
510 pte_t pteval = ptep_get(_pte);
513 if (pte_none(pteval))
515 pfn = pte_pfn(pteval);
516 if (is_zero_pfn(pfn))
518 folio = pfn_folio(pfn);
519 if (folio_test_large(folio))
521 release_pte_folio(folio);
524 list_for_each_entry_safe(folio, tmp, compound_pagelist, lru) {
525 list_del(&folio->lru);
526 release_pte_folio(folio);
530 static bool is_refcount_suitable(struct folio *folio)
532 int expected_refcount;
534 expected_refcount = folio_mapcount(folio);
535 if (folio_test_swapcache(folio))
536 expected_refcount += folio_nr_pages(folio);
538 return folio_ref_count(folio) == expected_refcount;
541 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
542 unsigned long address,
544 struct collapse_control *cc,
545 struct list_head *compound_pagelist)
547 struct page *page = NULL;
548 struct folio *folio = NULL;
550 int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
551 bool writable = false;
553 for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
554 _pte++, address += PAGE_SIZE) {
555 pte_t pteval = ptep_get(_pte);
556 if (pte_none(pteval) || (pte_present(pteval) &&
557 is_zero_pfn(pte_pfn(pteval)))) {
559 if (!userfaultfd_armed(vma) &&
560 (!cc->is_khugepaged ||
561 none_or_zero <= khugepaged_max_ptes_none)) {
564 result = SCAN_EXCEED_NONE_PTE;
565 count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
569 if (!pte_present(pteval)) {
570 result = SCAN_PTE_NON_PRESENT;
573 if (pte_uffd_wp(pteval)) {
574 result = SCAN_PTE_UFFD_WP;
577 page = vm_normal_page(vma, address, pteval);
578 if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
579 result = SCAN_PAGE_NULL;
583 folio = page_folio(page);
584 VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio);
586 if (page_mapcount(page) > 1) {
588 if (cc->is_khugepaged &&
589 shared > khugepaged_max_ptes_shared) {
590 result = SCAN_EXCEED_SHARED_PTE;
591 count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
596 if (folio_test_large(folio)) {
600 * Check if we have dealt with the compound page
603 list_for_each_entry(f, compound_pagelist, lru) {
610 * We can do it before isolate_lru_page because the
611 * page can't be freed from under us. NOTE: PG_lock
612 * is needed to serialize against split_huge_page
613 * when invoked from the VM.
615 if (!folio_trylock(folio)) {
616 result = SCAN_PAGE_LOCK;
621 * Check if the page has any GUP (or other external) pins.
623 * The page table that maps the page has been already unlinked
624 * from the page table tree and this process cannot get
625 * an additional pin on the page.
627 * New pins can come later if the page is shared across fork,
628 * but not from this process. The other process cannot write to
629 * the page, only trigger CoW.
631 if (!is_refcount_suitable(folio)) {
633 result = SCAN_PAGE_COUNT;
638 * Isolate the page to avoid collapsing an hugepage
639 * currently in use by the VM.
641 if (!folio_isolate_lru(folio)) {
643 result = SCAN_DEL_PAGE_LRU;
646 node_stat_mod_folio(folio,
647 NR_ISOLATED_ANON + folio_is_file_lru(folio),
648 folio_nr_pages(folio));
649 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
650 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
652 if (folio_test_large(folio))
653 list_add_tail(&folio->lru, compound_pagelist);
656 * If collapse was initiated by khugepaged, check that there is
657 * enough young pte to justify collapsing the page
659 if (cc->is_khugepaged &&
660 (pte_young(pteval) || folio_test_young(folio) ||
661 folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm,
665 if (pte_write(pteval))
669 if (unlikely(!writable)) {
670 result = SCAN_PAGE_RO;
671 } else if (unlikely(cc->is_khugepaged && !referenced)) {
672 result = SCAN_LACK_REFERENCED_PAGE;
674 result = SCAN_SUCCEED;
675 trace_mm_collapse_huge_page_isolate(&folio->page, none_or_zero,
676 referenced, writable, result);
680 release_pte_pages(pte, _pte, compound_pagelist);
681 trace_mm_collapse_huge_page_isolate(&folio->page, none_or_zero,
682 referenced, writable, result);
686 static void __collapse_huge_page_copy_succeeded(pte_t *pte,
687 struct vm_area_struct *vma,
688 unsigned long address,
690 struct list_head *compound_pagelist)
692 struct folio *src, *tmp;
696 for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
697 _pte++, address += PAGE_SIZE) {
698 pteval = ptep_get(_pte);
699 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
700 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
701 if (is_zero_pfn(pte_pfn(pteval))) {
703 * ptl mostly unnecessary.
706 ptep_clear(vma->vm_mm, address, _pte);
708 ksm_might_unmap_zero_page(vma->vm_mm, pteval);
711 struct page *src_page = pte_page(pteval);
713 src = page_folio(src_page);
714 if (!folio_test_large(src))
715 release_pte_folio(src);
717 * ptl mostly unnecessary, but preempt has to
718 * be disabled to update the per-cpu stats
719 * inside folio_remove_rmap_pte().
722 ptep_clear(vma->vm_mm, address, _pte);
723 folio_remove_rmap_pte(src, src_page, vma);
725 free_page_and_swap_cache(src_page);
729 list_for_each_entry_safe(src, tmp, compound_pagelist, lru) {
731 node_stat_sub_folio(src, NR_ISOLATED_ANON +
732 folio_is_file_lru(src));
734 free_swap_cache(src);
735 folio_putback_lru(src);
739 static void __collapse_huge_page_copy_failed(pte_t *pte,
742 struct vm_area_struct *vma,
743 struct list_head *compound_pagelist)
748 * Re-establish the PMD to point to the original page table
749 * entry. Restoring PMD needs to be done prior to releasing
750 * pages. Since pages are still isolated and locked here,
751 * acquiring anon_vma_lock_write is unnecessary.
753 pmd_ptl = pmd_lock(vma->vm_mm, pmd);
754 pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
755 spin_unlock(pmd_ptl);
757 * Release both raw and compound pages isolated
758 * in __collapse_huge_page_isolate.
760 release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist);
764 * __collapse_huge_page_copy - attempts to copy memory contents from raw
765 * pages to a hugepage. Cleans up the raw pages if copying succeeds;
766 * otherwise restores the original page table and releases isolated raw pages.
767 * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
769 * @pte: starting of the PTEs to copy from
770 * @page: the new hugepage to copy contents to
771 * @pmd: pointer to the new hugepage's PMD
772 * @orig_pmd: the original raw pages' PMD
773 * @vma: the original raw pages' virtual memory area
774 * @address: starting address to copy
775 * @ptl: lock on raw pages' PTEs
776 * @compound_pagelist: list that stores compound pages
778 static int __collapse_huge_page_copy(pte_t *pte,
782 struct vm_area_struct *vma,
783 unsigned long address,
785 struct list_head *compound_pagelist)
787 struct page *src_page;
790 unsigned long _address;
791 int result = SCAN_SUCCEED;
794 * Copying pages' contents is subject to memory poison at any iteration.
796 for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
797 _pte++, page++, _address += PAGE_SIZE) {
798 pteval = ptep_get(_pte);
799 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
800 clear_user_highpage(page, _address);
803 src_page = pte_page(pteval);
804 if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
805 result = SCAN_COPY_MC;
810 if (likely(result == SCAN_SUCCEED))
811 __collapse_huge_page_copy_succeeded(pte, vma, address, ptl,
814 __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
820 static void khugepaged_alloc_sleep(void)
824 add_wait_queue(&khugepaged_wait, &wait);
825 __set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
826 schedule_timeout(msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
827 remove_wait_queue(&khugepaged_wait, &wait);
830 struct collapse_control khugepaged_collapse_control = {
831 .is_khugepaged = true,
834 static bool hpage_collapse_scan_abort(int nid, struct collapse_control *cc)
839 * If node_reclaim_mode is disabled, then no extra effort is made to
840 * allocate memory locally.
842 if (!node_reclaim_enabled())
845 /* If there is a count for this node already, it must be acceptable */
846 if (cc->node_load[nid])
849 for (i = 0; i < MAX_NUMNODES; i++) {
850 if (!cc->node_load[i])
852 if (node_distance(nid, i) > node_reclaim_distance)
858 #define khugepaged_defrag() \
859 (transparent_hugepage_flags & \
860 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG))
862 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
863 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
865 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
869 static int hpage_collapse_find_target_node(struct collapse_control *cc)
871 int nid, target_node = 0, max_value = 0;
873 /* find first node with max normal pages hit */
874 for (nid = 0; nid < MAX_NUMNODES; nid++)
875 if (cc->node_load[nid] > max_value) {
876 max_value = cc->node_load[nid];
880 for_each_online_node(nid) {
881 if (max_value == cc->node_load[nid])
882 node_set(nid, cc->alloc_nmask);
888 static int hpage_collapse_find_target_node(struct collapse_control *cc)
894 static bool hpage_collapse_alloc_folio(struct folio **folio, gfp_t gfp, int node,
897 *folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, nmask);
899 if (unlikely(!*folio)) {
900 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
904 count_vm_event(THP_COLLAPSE_ALLOC);
909 * If mmap_lock temporarily dropped, revalidate vma
910 * before taking mmap_lock.
911 * Returns enum scan_result value.
914 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
916 struct vm_area_struct **vmap,
917 struct collapse_control *cc)
919 struct vm_area_struct *vma;
921 if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
922 return SCAN_ANY_PROCESS;
924 *vmap = vma = find_vma(mm, address);
926 return SCAN_VMA_NULL;
928 if (!thp_vma_suitable_order(vma, address, PMD_ORDER))
929 return SCAN_ADDRESS_RANGE;
930 if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false,
931 cc->is_khugepaged, PMD_ORDER))
932 return SCAN_VMA_CHECK;
934 * Anon VMA expected, the address may be unmapped then
935 * remapped to file after khugepaged reaquired the mmap_lock.
937 * thp_vma_allowable_order may return true for qualified file
940 if (expect_anon && (!(*vmap)->anon_vma || !vma_is_anonymous(*vmap)))
941 return SCAN_PAGE_ANON;
945 static int find_pmd_or_thp_or_none(struct mm_struct *mm,
946 unsigned long address,
951 *pmd = mm_find_pmd(mm, address);
953 return SCAN_PMD_NULL;
955 pmde = pmdp_get_lockless(*pmd);
957 return SCAN_PMD_NONE;
958 if (!pmd_present(pmde))
959 return SCAN_PMD_NULL;
960 if (pmd_trans_huge(pmde))
961 return SCAN_PMD_MAPPED;
962 if (pmd_devmap(pmde))
963 return SCAN_PMD_NULL;
965 return SCAN_PMD_NULL;
969 static int check_pmd_still_valid(struct mm_struct *mm,
970 unsigned long address,
974 int result = find_pmd_or_thp_or_none(mm, address, &new_pmd);
976 if (result != SCAN_SUCCEED)
984 * Bring missing pages in from swap, to complete THP collapse.
985 * Only done if hpage_collapse_scan_pmd believes it is worthwhile.
987 * Called and returns without pte mapped or spinlocks held.
988 * Returns result: if not SCAN_SUCCEED, mmap_lock has been released.
990 static int __collapse_huge_page_swapin(struct mm_struct *mm,
991 struct vm_area_struct *vma,
992 unsigned long haddr, pmd_t *pmd,
997 unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);
1002 for (address = haddr; address < end; address += PAGE_SIZE) {
1003 struct vm_fault vmf = {
1006 .pgoff = linear_page_index(vma, address),
1007 .flags = FAULT_FLAG_ALLOW_RETRY,
1012 pte = pte_offset_map_nolock(mm, pmd, address, &ptl);
1014 mmap_read_unlock(mm);
1015 result = SCAN_PMD_NULL;
1020 vmf.orig_pte = ptep_get_lockless(pte);
1021 if (!is_swap_pte(vmf.orig_pte))
1026 ret = do_swap_page(&vmf);
1027 /* Which unmaps pte (after perhaps re-checking the entry) */
1031 * do_swap_page returns VM_FAULT_RETRY with released mmap_lock.
1032 * Note we treat VM_FAULT_RETRY as VM_FAULT_ERROR here because
1033 * we do not retry here and swap entry will remain in pagetable
1034 * resulting in later failure.
1036 if (ret & VM_FAULT_RETRY) {
1037 /* Likely, but not guaranteed, that page lock failed */
1038 result = SCAN_PAGE_LOCK;
1041 if (ret & VM_FAULT_ERROR) {
1042 mmap_read_unlock(mm);
1052 /* Drain LRU cache to remove extra pin on the swapped in pages */
1056 result = SCAN_SUCCEED;
1058 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, result);
1062 static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
1063 struct collapse_control *cc)
1065 gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
1067 int node = hpage_collapse_find_target_node(cc);
1068 struct folio *folio;
1070 if (!hpage_collapse_alloc_folio(&folio, gfp, node, &cc->alloc_nmask)) {
1072 return SCAN_ALLOC_HUGE_PAGE_FAIL;
1075 if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
1078 return SCAN_CGROUP_CHARGE_FAIL;
1081 count_memcg_folio_events(folio, THP_COLLAPSE_ALLOC, 1);
1083 *hpage = folio_page(folio, 0);
1084 return SCAN_SUCCEED;
1087 static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
1088 int referenced, int unmapped,
1089 struct collapse_control *cc)
1091 LIST_HEAD(compound_pagelist);
1095 struct folio *folio;
1097 spinlock_t *pmd_ptl, *pte_ptl;
1098 int result = SCAN_FAIL;
1099 struct vm_area_struct *vma;
1100 struct mmu_notifier_range range;
1102 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1105 * Before allocating the hugepage, release the mmap_lock read lock.
1106 * The allocation can take potentially a long time if it involves
1107 * sync compaction, and we do not need to hold the mmap_lock during
1108 * that. We will recheck the vma after taking it again in write mode.
1110 mmap_read_unlock(mm);
1112 result = alloc_charge_hpage(&hpage, mm, cc);
1113 if (result != SCAN_SUCCEED)
1117 result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
1118 if (result != SCAN_SUCCEED) {
1119 mmap_read_unlock(mm);
1123 result = find_pmd_or_thp_or_none(mm, address, &pmd);
1124 if (result != SCAN_SUCCEED) {
1125 mmap_read_unlock(mm);
1131 * __collapse_huge_page_swapin will return with mmap_lock
1132 * released when it fails. So we jump out_nolock directly in
1133 * that case. Continuing to collapse causes inconsistency.
1135 result = __collapse_huge_page_swapin(mm, vma, address, pmd,
1137 if (result != SCAN_SUCCEED)
1141 mmap_read_unlock(mm);
1143 * Prevent all access to pagetables with the exception of
1144 * gup_fast later handled by the ptep_clear_flush and the VM
1145 * handled by the anon_vma lock + PG_lock.
1147 * UFFDIO_MOVE is prevented to race as well thanks to the
1150 mmap_write_lock(mm);
1151 result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
1152 if (result != SCAN_SUCCEED)
1154 /* check if the pmd is still valid */
1155 result = check_pmd_still_valid(mm, address, pmd);
1156 if (result != SCAN_SUCCEED)
1159 vma_start_write(vma);
1160 anon_vma_lock_write(vma->anon_vma);
1162 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address,
1163 address + HPAGE_PMD_SIZE);
1164 mmu_notifier_invalidate_range_start(&range);
1166 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1168 * This removes any huge TLB entry from the CPU so we won't allow
1169 * huge and small TLB entries for the same virtual address to
1170 * avoid the risk of CPU bugs in that area.
1172 * Parallel fast GUP is fine since fast GUP will back off when
1173 * it detects PMD is changed.
1175 _pmd = pmdp_collapse_flush(vma, address, pmd);
1176 spin_unlock(pmd_ptl);
1177 mmu_notifier_invalidate_range_end(&range);
1178 tlb_remove_table_sync_one();
1180 pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl);
1182 result = __collapse_huge_page_isolate(vma, address, pte, cc,
1183 &compound_pagelist);
1184 spin_unlock(pte_ptl);
1186 result = SCAN_PMD_NULL;
1189 if (unlikely(result != SCAN_SUCCEED)) {
1193 BUG_ON(!pmd_none(*pmd));
1195 * We can only use set_pmd_at when establishing
1196 * hugepmds and never for establishing regular pmds that
1197 * points to regular pagetables. Use pmd_populate for that
1199 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1200 spin_unlock(pmd_ptl);
1201 anon_vma_unlock_write(vma->anon_vma);
1206 * All pages are isolated and locked so anon_vma rmap
1207 * can't run anymore.
1209 anon_vma_unlock_write(vma->anon_vma);
1211 result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
1212 vma, address, pte_ptl,
1213 &compound_pagelist);
1215 if (unlikely(result != SCAN_SUCCEED))
1218 folio = page_folio(hpage);
1220 * The smp_wmb() inside __folio_mark_uptodate() ensures the
1221 * copy_huge_page writes become visible before the set_pmd_at()
1224 __folio_mark_uptodate(folio);
1225 pgtable = pmd_pgtable(_pmd);
1227 _pmd = mk_huge_pmd(hpage, vma->vm_page_prot);
1228 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1231 BUG_ON(!pmd_none(*pmd));
1232 folio_add_new_anon_rmap(folio, vma, address);
1233 folio_add_lru_vma(folio, vma);
1234 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1235 set_pmd_at(mm, address, pmd, _pmd);
1236 update_mmu_cache_pmd(vma, address, pmd);
1237 spin_unlock(pmd_ptl);
1241 result = SCAN_SUCCEED;
1243 mmap_write_unlock(mm);
1247 trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
1251 static int hpage_collapse_scan_pmd(struct mm_struct *mm,
1252 struct vm_area_struct *vma,
1253 unsigned long address, bool *mmap_locked,
1254 struct collapse_control *cc)
1258 int result = SCAN_FAIL, referenced = 0;
1259 int none_or_zero = 0, shared = 0;
1260 struct page *page = NULL;
1261 struct folio *folio = NULL;
1262 unsigned long _address;
1264 int node = NUMA_NO_NODE, unmapped = 0;
1265 bool writable = false;
1267 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1269 result = find_pmd_or_thp_or_none(mm, address, &pmd);
1270 if (result != SCAN_SUCCEED)
1273 memset(cc->node_load, 0, sizeof(cc->node_load));
1274 nodes_clear(cc->alloc_nmask);
1275 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1277 result = SCAN_PMD_NULL;
1281 for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR;
1282 _pte++, _address += PAGE_SIZE) {
1283 pte_t pteval = ptep_get(_pte);
1284 if (is_swap_pte(pteval)) {
1286 if (!cc->is_khugepaged ||
1287 unmapped <= khugepaged_max_ptes_swap) {
1289 * Always be strict with uffd-wp
1290 * enabled swap entries. Please see
1291 * comment below for pte_uffd_wp().
1293 if (pte_swp_uffd_wp_any(pteval)) {
1294 result = SCAN_PTE_UFFD_WP;
1299 result = SCAN_EXCEED_SWAP_PTE;
1300 count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
1304 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1306 if (!userfaultfd_armed(vma) &&
1307 (!cc->is_khugepaged ||
1308 none_or_zero <= khugepaged_max_ptes_none)) {
1311 result = SCAN_EXCEED_NONE_PTE;
1312 count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
1316 if (pte_uffd_wp(pteval)) {
1318 * Don't collapse the page if any of the small
1319 * PTEs are armed with uffd write protection.
1320 * Here we can also mark the new huge pmd as
1321 * write protected if any of the small ones is
1322 * marked but that could bring unknown
1323 * userfault messages that falls outside of
1324 * the registered range. So, just be simple.
1326 result = SCAN_PTE_UFFD_WP;
1329 if (pte_write(pteval))
1332 page = vm_normal_page(vma, _address, pteval);
1333 if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
1334 result = SCAN_PAGE_NULL;
1338 if (page_mapcount(page) > 1) {
1340 if (cc->is_khugepaged &&
1341 shared > khugepaged_max_ptes_shared) {
1342 result = SCAN_EXCEED_SHARED_PTE;
1343 count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
1348 folio = page_folio(page);
1350 * Record which node the original page is from and save this
1351 * information to cc->node_load[].
1352 * Khugepaged will allocate hugepage from the node has the max
1355 node = folio_nid(folio);
1356 if (hpage_collapse_scan_abort(node, cc)) {
1357 result = SCAN_SCAN_ABORT;
1360 cc->node_load[node]++;
1361 if (!folio_test_lru(folio)) {
1362 result = SCAN_PAGE_LRU;
1365 if (folio_test_locked(folio)) {
1366 result = SCAN_PAGE_LOCK;
1369 if (!folio_test_anon(folio)) {
1370 result = SCAN_PAGE_ANON;
1375 * Check if the page has any GUP (or other external) pins.
1377 * Here the check may be racy:
1378 * it may see total_mapcount > refcount in some cases?
1379 * But such case is ephemeral we could always retry collapse
1380 * later. However it may report false positive if the page
1381 * has excessive GUP pins (i.e. 512). Anyway the same check
1382 * will be done again later the risk seems low.
1384 if (!is_refcount_suitable(folio)) {
1385 result = SCAN_PAGE_COUNT;
1390 * If collapse was initiated by khugepaged, check that there is
1391 * enough young pte to justify collapsing the page
1393 if (cc->is_khugepaged &&
1394 (pte_young(pteval) || folio_test_young(folio) ||
1395 folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm,
1400 result = SCAN_PAGE_RO;
1401 } else if (cc->is_khugepaged &&
1403 (unmapped && referenced < HPAGE_PMD_NR / 2))) {
1404 result = SCAN_LACK_REFERENCED_PAGE;
1406 result = SCAN_SUCCEED;
1409 pte_unmap_unlock(pte, ptl);
1410 if (result == SCAN_SUCCEED) {
1411 result = collapse_huge_page(mm, address, referenced,
1413 /* collapse_huge_page will return with the mmap_lock released */
1414 *mmap_locked = false;
1417 trace_mm_khugepaged_scan_pmd(mm, &folio->page, writable, referenced,
1418 none_or_zero, result, unmapped);
1422 static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot)
1424 struct mm_slot *slot = &mm_slot->slot;
1425 struct mm_struct *mm = slot->mm;
1427 lockdep_assert_held(&khugepaged_mm_lock);
1429 if (hpage_collapse_test_exit(mm)) {
1431 hash_del(&slot->hash);
1432 list_del(&slot->mm_node);
1435 * Not strictly needed because the mm exited already.
1437 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1440 /* khugepaged_mm_lock actually not necessary for the below */
1441 mm_slot_free(mm_slot_cache, mm_slot);
1447 /* hpage must be locked, and mmap_lock must be held */
1448 static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
1449 pmd_t *pmdp, struct page *hpage)
1451 struct vm_fault vmf = {
1458 VM_BUG_ON(!PageTransHuge(hpage));
1459 mmap_assert_locked(vma->vm_mm);
1461 if (do_set_pmd(&vmf, hpage))
1465 return SCAN_SUCCEED;
1469 * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at
1472 * @mm: process address space where collapse happens
1473 * @addr: THP collapse address
1474 * @install_pmd: If a huge PMD should be installed
1476 * This function checks whether all the PTEs in the PMD are pointing to the
1477 * right THP. If so, retract the page table so the THP can refault in with
1478 * as pmd-mapped. Possibly install a huge PMD mapping the THP.
1480 int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
1483 struct mmu_notifier_range range;
1484 bool notified = false;
1485 unsigned long haddr = addr & HPAGE_PMD_MASK;
1486 struct vm_area_struct *vma = vma_lookup(mm, haddr);
1487 struct folio *folio;
1488 pte_t *start_pte, *pte;
1489 pmd_t *pmd, pgt_pmd;
1490 spinlock_t *pml = NULL, *ptl;
1491 int nr_ptes = 0, result = SCAN_FAIL;
1494 mmap_assert_locked(mm);
1496 /* First check VMA found, in case page tables are being torn down */
1497 if (!vma || !vma->vm_file ||
1498 !range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE))
1499 return SCAN_VMA_CHECK;
1501 /* Fast check before locking page if already PMD-mapped */
1502 result = find_pmd_or_thp_or_none(mm, haddr, &pmd);
1503 if (result == SCAN_PMD_MAPPED)
1507 * If we are here, we've succeeded in replacing all the native pages
1508 * in the page cache with a single hugepage. If a mm were to fault-in
1509 * this memory (mapped by a suitably aligned VMA), we'd get the hugepage
1510 * and map it by a PMD, regardless of sysfs THP settings. As such, let's
1511 * analogously elide sysfs THP settings here.
1513 if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false, false,
1515 return SCAN_VMA_CHECK;
1517 /* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */
1518 if (userfaultfd_wp(vma))
1519 return SCAN_PTE_UFFD_WP;
1521 folio = filemap_lock_folio(vma->vm_file->f_mapping,
1522 linear_page_index(vma, haddr));
1524 return SCAN_PAGE_NULL;
1526 if (folio_order(folio) != HPAGE_PMD_ORDER) {
1527 result = SCAN_PAGE_COMPOUND;
1531 result = find_pmd_or_thp_or_none(mm, haddr, &pmd);
1537 * All pte entries have been removed and pmd cleared.
1538 * Skip all the pte checks and just update the pmd mapping.
1540 goto maybe_install_pmd;
1546 start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);
1547 if (!start_pte) /* mmap_lock + page lock should prevent this */
1550 /* step 1: check all mapped PTEs are to the right huge page */
1551 for (i = 0, addr = haddr, pte = start_pte;
1552 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
1554 pte_t ptent = ptep_get(pte);
1556 /* empty pte, skip */
1557 if (pte_none(ptent))
1560 /* page swapped out, abort */
1561 if (!pte_present(ptent)) {
1562 result = SCAN_PTE_NON_PRESENT;
1566 page = vm_normal_page(vma, addr, ptent);
1567 if (WARN_ON_ONCE(page && is_zone_device_page(page)))
1570 * Note that uprobe, debugger, or MAP_PRIVATE may change the
1571 * page table, but the new page will not be a subpage of hpage.
1573 if (folio_page(folio, i) != page)
1577 pte_unmap_unlock(start_pte, ptl);
1578 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
1579 haddr, haddr + HPAGE_PMD_SIZE);
1580 mmu_notifier_invalidate_range_start(&range);
1584 * pmd_lock covers a wider range than ptl, and (if split from mm's
1585 * page_table_lock) ptl nests inside pml. The less time we hold pml,
1586 * the better; but userfaultfd's mfill_atomic_pte() on a private VMA
1587 * inserts a valid as-if-COWed PTE without even looking up page cache.
1588 * So page lock of folio does not protect from it, so we must not drop
1589 * ptl before pgt_pmd is removed, so uffd private needs pml taken now.
1591 if (userfaultfd_armed(vma) && !(vma->vm_flags & VM_SHARED))
1592 pml = pmd_lock(mm, pmd);
1594 start_pte = pte_offset_map_nolock(mm, pmd, haddr, &ptl);
1595 if (!start_pte) /* mmap_lock + page lock should prevent this */
1599 else if (ptl != pml)
1600 spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
1602 /* step 2: clear page table and adjust rmap */
1603 for (i = 0, addr = haddr, pte = start_pte;
1604 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
1606 pte_t ptent = ptep_get(pte);
1608 if (pte_none(ptent))
1611 * We dropped ptl after the first scan, to do the mmu_notifier:
1612 * page lock stops more PTEs of the folio being faulted in, but
1613 * does not stop write faults COWing anon copies from existing
1614 * PTEs; and does not stop those being swapped out or migrated.
1616 if (!pte_present(ptent)) {
1617 result = SCAN_PTE_NON_PRESENT;
1620 page = vm_normal_page(vma, addr, ptent);
1621 if (folio_page(folio, i) != page)
1625 * Must clear entry, or a racing truncate may re-remove it.
1626 * TLB flush can be left until pmdp_collapse_flush() does it.
1627 * PTE dirty? Shmem page is already dirty; file is read-only.
1629 ptep_clear(mm, addr, pte);
1630 folio_remove_rmap_pte(folio, page, vma);
1634 pte_unmap(start_pte);
1638 /* step 3: set proper refcount and mm_counters. */
1640 folio_ref_sub(folio, nr_ptes);
1641 add_mm_counter(mm, mm_counter_file(folio), -nr_ptes);
1644 /* step 4: remove empty page table */
1646 pml = pmd_lock(mm, pmd);
1648 spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
1650 pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd);
1651 pmdp_get_lockless_sync();
1656 mmu_notifier_invalidate_range_end(&range);
1659 page_table_check_pte_clear_range(mm, haddr, pgt_pmd);
1660 pte_free_defer(mm, pmd_pgtable(pgt_pmd));
1663 /* step 5: install pmd entry */
1664 result = install_pmd
1665 ? set_huge_pmd(vma, haddr, pmd, &folio->page)
1671 folio_ref_sub(folio, nr_ptes);
1672 add_mm_counter(mm, mm_counter_file(folio), -nr_ptes);
1675 pte_unmap_unlock(start_pte, ptl);
1676 if (pml && pml != ptl)
1679 mmu_notifier_invalidate_range_end(&range);
1681 folio_unlock(folio);
1686 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1688 struct vm_area_struct *vma;
1690 i_mmap_lock_read(mapping);
1691 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1692 struct mmu_notifier_range range;
1693 struct mm_struct *mm;
1695 pmd_t *pmd, pgt_pmd;
1698 bool skipped_uffd = false;
1701 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that
1702 * got written to. These VMAs are likely not worth removing
1703 * page tables from, as PMD-mapping is likely to be split later.
1705 if (READ_ONCE(vma->anon_vma))
1708 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1709 if (addr & ~HPAGE_PMD_MASK ||
1710 vma->vm_end < addr + HPAGE_PMD_SIZE)
1714 if (find_pmd_or_thp_or_none(mm, addr, &pmd) != SCAN_SUCCEED)
1717 if (hpage_collapse_test_exit(mm))
1720 * When a vma is registered with uffd-wp, we cannot recycle
1721 * the page table because there may be pte markers installed.
1722 * Other vmas can still have the same file mapped hugely, but
1723 * skip this one: it will always be mapped in small page size
1724 * for uffd-wp registered ranges.
1726 if (userfaultfd_wp(vma))
1729 /* PTEs were notified when unmapped; but now for the PMD? */
1730 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
1731 addr, addr + HPAGE_PMD_SIZE);
1732 mmu_notifier_invalidate_range_start(&range);
1734 pml = pmd_lock(mm, pmd);
1735 ptl = pte_lockptr(mm, pmd);
1737 spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
1740 * Huge page lock is still held, so normally the page table
1741 * must remain empty; and we have already skipped anon_vma
1742 * and userfaultfd_wp() vmas. But since the mmap_lock is not
1743 * held, it is still possible for a racing userfaultfd_ioctl()
1744 * to have inserted ptes or markers. Now that we hold ptlock,
1745 * repeating the anon_vma check protects from one category,
1746 * and repeating the userfaultfd_wp() check from another.
1748 if (unlikely(vma->anon_vma || userfaultfd_wp(vma))) {
1749 skipped_uffd = true;
1751 pgt_pmd = pmdp_collapse_flush(vma, addr, pmd);
1752 pmdp_get_lockless_sync();
1759 mmu_notifier_invalidate_range_end(&range);
1761 if (!skipped_uffd) {
1763 page_table_check_pte_clear_range(mm, addr, pgt_pmd);
1764 pte_free_defer(mm, pmd_pgtable(pgt_pmd));
1767 i_mmap_unlock_read(mapping);
1771 * collapse_file - collapse filemap/tmpfs/shmem pages into huge one.
1773 * @mm: process address space where collapse happens
1774 * @addr: virtual collapse start address
1775 * @file: file that collapse on
1776 * @start: collapse start address
1777 * @cc: collapse context and scratchpad
1779 * Basic scheme is simple, details are more complex:
1780 * - allocate and lock a new huge page;
1781 * - scan page cache, locking old pages
1782 * + swap/gup in pages if necessary;
1783 * - copy data to new page
1784 * - handle shmem holes
1785 * + re-validate that holes weren't filled by someone else
1786 * + check for userfaultfd
1787 * - finalize updates to the page cache;
1788 * - if replacing succeeds:
1789 * + unlock huge page;
1791 * - if replacing failed;
1792 * + unlock old pages
1793 * + unlock and free huge page;
1795 static int collapse_file(struct mm_struct *mm, unsigned long addr,
1796 struct file *file, pgoff_t start,
1797 struct collapse_control *cc)
1799 struct address_space *mapping = file->f_mapping;
1803 struct folio *folio;
1804 pgoff_t index = 0, end = start + HPAGE_PMD_NR;
1805 LIST_HEAD(pagelist);
1806 XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
1807 int nr_none = 0, result = SCAN_SUCCEED;
1808 bool is_shmem = shmem_file(file);
1811 VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
1812 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1814 result = alloc_charge_hpage(&hpage, mm, cc);
1815 if (result != SCAN_SUCCEED)
1818 __SetPageLocked(hpage);
1820 __SetPageSwapBacked(hpage);
1821 hpage->index = start;
1822 hpage->mapping = mapping;
1825 * Ensure we have slots for all the pages in the range. This is
1826 * almost certainly a no-op because most of the pages must be present
1830 xas_create_range(&xas);
1831 if (!xas_error(&xas))
1833 xas_unlock_irq(&xas);
1834 if (!xas_nomem(&xas, GFP_KERNEL)) {
1840 for (index = start; index < end; index++) {
1841 xas_set(&xas, index);
1842 page = xas_load(&xas);
1844 VM_BUG_ON(index != xas.xa_index);
1848 * Stop if extent has been truncated or
1849 * hole-punched, and is now completely
1852 if (index == start) {
1853 if (!xas_next_entry(&xas, end - 1)) {
1854 result = SCAN_TRUNCATED;
1862 if (xa_is_value(page) || !PageUptodate(page)) {
1863 xas_unlock_irq(&xas);
1864 /* swap in or instantiate fallocated page */
1865 if (shmem_get_folio(mapping->host, index,
1866 &folio, SGP_NOALLOC)) {
1870 /* drain lru cache to help isolate_lru_page() */
1872 page = folio_file_page(folio, index);
1873 } else if (trylock_page(page)) {
1875 xas_unlock_irq(&xas);
1877 result = SCAN_PAGE_LOCK;
1880 } else { /* !is_shmem */
1881 if (!page || xa_is_value(page)) {
1882 xas_unlock_irq(&xas);
1883 page_cache_sync_readahead(mapping, &file->f_ra,
1886 /* drain lru cache to help isolate_lru_page() */
1888 page = find_lock_page(mapping, index);
1889 if (unlikely(page == NULL)) {
1893 } else if (PageDirty(page)) {
1895 * khugepaged only works on read-only fd,
1896 * so this page is dirty because it hasn't
1897 * been flushed since first write. There
1898 * won't be new dirty pages.
1900 * Trigger async flush here and hope the
1901 * writeback is done when khugepaged
1902 * revisits this page.
1904 * This is a one-off situation. We are not
1905 * forcing writeback in loop.
1907 xas_unlock_irq(&xas);
1908 filemap_flush(mapping);
1911 } else if (PageWriteback(page)) {
1912 xas_unlock_irq(&xas);
1915 } else if (trylock_page(page)) {
1917 xas_unlock_irq(&xas);
1919 result = SCAN_PAGE_LOCK;
1925 * The page must be locked, so we can drop the i_pages lock
1926 * without racing with truncate.
1928 VM_BUG_ON_PAGE(!PageLocked(page), page);
1930 /* make sure the page is up to date */
1931 if (unlikely(!PageUptodate(page))) {
1937 * If file was truncated then extended, or hole-punched, before
1938 * we locked the first page, then a THP might be there already.
1939 * This will be discovered on the first iteration.
1941 if (PageTransCompound(page)) {
1942 struct page *head = compound_head(page);
1944 result = compound_order(head) == HPAGE_PMD_ORDER &&
1945 head->index == start
1946 /* Maybe PMD-mapped */
1947 ? SCAN_PTE_MAPPED_HUGEPAGE
1948 : SCAN_PAGE_COMPOUND;
1952 folio = page_folio(page);
1954 if (folio_mapping(folio) != mapping) {
1955 result = SCAN_TRUNCATED;
1959 if (!is_shmem && (folio_test_dirty(folio) ||
1960 folio_test_writeback(folio))) {
1962 * khugepaged only works on read-only fd, so this
1963 * page is dirty because it hasn't been flushed
1964 * since first write.
1970 if (!folio_isolate_lru(folio)) {
1971 result = SCAN_DEL_PAGE_LRU;
1975 if (!filemap_release_folio(folio, GFP_KERNEL)) {
1976 result = SCAN_PAGE_HAS_PRIVATE;
1977 folio_putback_lru(folio);
1981 if (folio_mapped(folio))
1983 TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH);
1987 VM_BUG_ON_PAGE(page != xa_load(xas.xa, index), page);
1990 * We control three references to the page:
1991 * - we hold a pin on it;
1992 * - one reference from page cache;
1993 * - one from isolate_lru_page;
1994 * If those are the only references, then any new usage of the
1995 * page will have to fetch it from the page cache. That requires
1996 * locking the page to handle truncate, so any new usage will be
1997 * blocked until we unlock page after collapse/during rollback.
1999 if (page_count(page) != 3) {
2000 result = SCAN_PAGE_COUNT;
2001 xas_unlock_irq(&xas);
2002 putback_lru_page(page);
2007 * Accumulate the pages that are being collapsed.
2009 list_add_tail(&page->lru, &pagelist);
2018 filemap_nr_thps_inc(mapping);
2020 * Paired with smp_mb() in do_dentry_open() to ensure
2021 * i_writecount is up to date and the update to nr_thps is
2022 * visible. Ensures the page cache will be truncated if the
2023 * file is opened writable.
2026 if (inode_is_open_for_write(mapping->host)) {
2028 filemap_nr_thps_dec(mapping);
2033 xas_unlock_irq(&xas);
2037 * If collapse is successful, flush must be done now before copying.
2038 * If collapse is unsuccessful, does flush actually need to be done?
2039 * Do it anyway, to clear the state.
2041 try_to_unmap_flush();
2043 if (result == SCAN_SUCCEED && nr_none &&
2044 !shmem_charge(mapping->host, nr_none))
2046 if (result != SCAN_SUCCEED) {
2052 * The old pages are locked, so they won't change anymore.
2055 list_for_each_entry(page, &pagelist, lru) {
2056 while (index < page->index) {
2057 clear_highpage(hpage + (index % HPAGE_PMD_NR));
2060 if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR), page) > 0) {
2061 result = SCAN_COPY_MC;
2066 while (index < end) {
2067 clear_highpage(hpage + (index % HPAGE_PMD_NR));
2072 struct vm_area_struct *vma;
2073 int nr_none_check = 0;
2075 i_mmap_lock_read(mapping);
2078 xas_set(&xas, start);
2079 for (index = start; index < end; index++) {
2080 if (!xas_next(&xas)) {
2081 xas_store(&xas, XA_RETRY_ENTRY);
2082 if (xas_error(&xas)) {
2083 result = SCAN_STORE_FAILED;
2090 if (nr_none != nr_none_check) {
2091 result = SCAN_PAGE_FILLED;
2096 * If userspace observed a missing page in a VMA with a MODE_MISSING
2097 * userfaultfd, then it might expect a UFFD_EVENT_PAGEFAULT for that
2098 * page. If so, we need to roll back to avoid suppressing such an
2099 * event. Since wp/minor userfaultfds don't give userspace any
2100 * guarantees that the kernel doesn't fill a missing page with a zero
2101 * page, so they don't matter here.
2103 * Any userfaultfds registered after this point will not be able to
2104 * observe any missing pages due to the previously inserted retry
2107 vma_interval_tree_foreach(vma, &mapping->i_mmap, start, end) {
2108 if (userfaultfd_missing(vma)) {
2109 result = SCAN_EXCEED_NONE_PTE;
2115 i_mmap_unlock_read(mapping);
2116 if (result != SCAN_SUCCEED) {
2117 xas_set(&xas, start);
2118 for (index = start; index < end; index++) {
2119 if (xas_next(&xas) == XA_RETRY_ENTRY)
2120 xas_store(&xas, NULL);
2123 xas_unlock_irq(&xas);
2130 folio = page_folio(hpage);
2131 nr = folio_nr_pages(folio);
2133 __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
2135 __lruvec_stat_mod_folio(folio, NR_FILE_THPS, nr);
2138 __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr_none);
2139 /* nr_none is always 0 for non-shmem. */
2140 __lruvec_stat_mod_folio(folio, NR_SHMEM, nr_none);
2144 * Mark hpage as uptodate before inserting it into the page cache so
2145 * that it isn't mistaken for an fallocated but unwritten page.
2147 folio_mark_uptodate(folio);
2148 folio_ref_add(folio, HPAGE_PMD_NR - 1);
2151 folio_mark_dirty(folio);
2152 folio_add_lru(folio);
2154 /* Join all the small entries into a single multi-index entry. */
2155 xas_set_order(&xas, start, HPAGE_PMD_ORDER);
2156 xas_store(&xas, folio);
2157 WARN_ON_ONCE(xas_error(&xas));
2158 xas_unlock_irq(&xas);
2161 * Remove pte page tables, so we can re-fault the page as huge.
2162 * If MADV_COLLAPSE, adjust result to call collapse_pte_mapped_thp().
2164 retract_page_tables(mapping, start);
2165 if (cc && !cc->is_khugepaged)
2166 result = SCAN_PTE_MAPPED_HUGEPAGE;
2167 folio_unlock(folio);
2170 * The collapse has succeeded, so free the old pages.
2172 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
2173 list_del(&page->lru);
2174 page->mapping = NULL;
2175 ClearPageActive(page);
2176 ClearPageUnevictable(page);
2178 folio_put_refs(page_folio(page), 3);
2184 /* Something went wrong: roll back page cache changes */
2187 mapping->nrpages -= nr_none;
2188 xas_unlock_irq(&xas);
2189 shmem_uncharge(mapping->host, nr_none);
2192 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
2193 list_del(&page->lru);
2195 putback_lru_page(page);
2199 * Undo the updates of filemap_nr_thps_inc for non-SHMEM
2200 * file only. This undo is not needed unless failure is
2201 * due to SCAN_COPY_MC.
2203 if (!is_shmem && result == SCAN_COPY_MC) {
2204 filemap_nr_thps_dec(mapping);
2206 * Paired with smp_mb() in do_dentry_open() to
2207 * ensure the update to nr_thps is visible.
2212 hpage->mapping = NULL;
2217 VM_BUG_ON(!list_empty(&pagelist));
2218 trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result);
2222 static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
2223 struct file *file, pgoff_t start,
2224 struct collapse_control *cc)
2226 struct page *page = NULL;
2227 struct address_space *mapping = file->f_mapping;
2228 XA_STATE(xas, &mapping->i_pages, start);
2230 int node = NUMA_NO_NODE;
2231 int result = SCAN_SUCCEED;
2235 memset(cc->node_load, 0, sizeof(cc->node_load));
2236 nodes_clear(cc->alloc_nmask);
2238 xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) {
2239 if (xas_retry(&xas, page))
2242 if (xa_is_value(page)) {
2244 if (cc->is_khugepaged &&
2245 swap > khugepaged_max_ptes_swap) {
2246 result = SCAN_EXCEED_SWAP_PTE;
2247 count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
2254 * TODO: khugepaged should compact smaller compound pages
2255 * into a PMD sized page
2257 if (PageTransCompound(page)) {
2258 struct page *head = compound_head(page);
2260 result = compound_order(head) == HPAGE_PMD_ORDER &&
2261 head->index == start
2262 /* Maybe PMD-mapped */
2263 ? SCAN_PTE_MAPPED_HUGEPAGE
2264 : SCAN_PAGE_COMPOUND;
2266 * For SCAN_PTE_MAPPED_HUGEPAGE, further processing
2267 * by the caller won't touch the page cache, and so
2268 * it's safe to skip LRU and refcount checks before
2274 node = page_to_nid(page);
2275 if (hpage_collapse_scan_abort(node, cc)) {
2276 result = SCAN_SCAN_ABORT;
2279 cc->node_load[node]++;
2281 if (!PageLRU(page)) {
2282 result = SCAN_PAGE_LRU;
2286 if (page_count(page) !=
2287 1 + page_mapcount(page) + page_has_private(page)) {
2288 result = SCAN_PAGE_COUNT;
2293 * We probably should check if the page is referenced here, but
2294 * nobody would transfer pte_young() to PageReferenced() for us.
2295 * And rmap walk here is just too costly...
2300 if (need_resched()) {
2307 if (result == SCAN_SUCCEED) {
2308 if (cc->is_khugepaged &&
2309 present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
2310 result = SCAN_EXCEED_NONE_PTE;
2311 count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
2313 result = collapse_file(mm, addr, file, start, cc);
2317 trace_mm_khugepaged_scan_file(mm, page, file, present, swap, result);
2321 static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
2322 struct file *file, pgoff_t start,
2323 struct collapse_control *cc)
2329 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
2330 struct collapse_control *cc)
2331 __releases(&khugepaged_mm_lock)
2332 __acquires(&khugepaged_mm_lock)
2334 struct vma_iterator vmi;
2335 struct khugepaged_mm_slot *mm_slot;
2336 struct mm_slot *slot;
2337 struct mm_struct *mm;
2338 struct vm_area_struct *vma;
2342 lockdep_assert_held(&khugepaged_mm_lock);
2343 *result = SCAN_FAIL;
2345 if (khugepaged_scan.mm_slot) {
2346 mm_slot = khugepaged_scan.mm_slot;
2347 slot = &mm_slot->slot;
2349 slot = list_entry(khugepaged_scan.mm_head.next,
2350 struct mm_slot, mm_node);
2351 mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
2352 khugepaged_scan.address = 0;
2353 khugepaged_scan.mm_slot = mm_slot;
2355 spin_unlock(&khugepaged_mm_lock);
2359 * Don't wait for semaphore (to avoid long wait times). Just move to
2360 * the next mm on the list.
2363 if (unlikely(!mmap_read_trylock(mm)))
2364 goto breakouterloop_mmap_lock;
2367 if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
2368 goto breakouterloop;
2370 vma_iter_init(&vmi, mm, khugepaged_scan.address);
2371 for_each_vma(vmi, vma) {
2372 unsigned long hstart, hend;
2375 if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
2379 if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false,
2385 hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE);
2386 hend = round_down(vma->vm_end, HPAGE_PMD_SIZE);
2387 if (khugepaged_scan.address > hend)
2389 if (khugepaged_scan.address < hstart)
2390 khugepaged_scan.address = hstart;
2391 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2393 while (khugepaged_scan.address < hend) {
2394 bool mmap_locked = true;
2397 if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
2398 goto breakouterloop;
2400 VM_BUG_ON(khugepaged_scan.address < hstart ||
2401 khugepaged_scan.address + HPAGE_PMD_SIZE >
2403 if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) {
2404 struct file *file = get_file(vma->vm_file);
2405 pgoff_t pgoff = linear_page_index(vma,
2406 khugepaged_scan.address);
2408 mmap_read_unlock(mm);
2409 mmap_locked = false;
2410 *result = hpage_collapse_scan_file(mm,
2411 khugepaged_scan.address, file, pgoff, cc);
2413 if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
2415 if (hpage_collapse_test_exit_or_disable(mm))
2416 goto breakouterloop;
2417 *result = collapse_pte_mapped_thp(mm,
2418 khugepaged_scan.address, false);
2419 if (*result == SCAN_PMD_MAPPED)
2420 *result = SCAN_SUCCEED;
2421 mmap_read_unlock(mm);
2424 *result = hpage_collapse_scan_pmd(mm, vma,
2425 khugepaged_scan.address, &mmap_locked, cc);
2428 if (*result == SCAN_SUCCEED)
2429 ++khugepaged_pages_collapsed;
2431 /* move to next address */
2432 khugepaged_scan.address += HPAGE_PMD_SIZE;
2433 progress += HPAGE_PMD_NR;
2436 * We released mmap_lock so break loop. Note
2437 * that we drop mmap_lock before all hugepage
2438 * allocations, so if allocation fails, we are
2439 * guaranteed to break here and report the
2440 * correct result back to caller.
2442 goto breakouterloop_mmap_lock;
2443 if (progress >= pages)
2444 goto breakouterloop;
2448 mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */
2449 breakouterloop_mmap_lock:
2451 spin_lock(&khugepaged_mm_lock);
2452 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2454 * Release the current mm_slot if this mm is about to die, or
2455 * if we scanned all vmas of this mm.
2457 if (hpage_collapse_test_exit(mm) || !vma) {
2459 * Make sure that if mm_users is reaching zero while
2460 * khugepaged runs here, khugepaged_exit will find
2461 * mm_slot not pointing to the exiting mm.
2463 if (slot->mm_node.next != &khugepaged_scan.mm_head) {
2464 slot = list_entry(slot->mm_node.next,
2465 struct mm_slot, mm_node);
2466 khugepaged_scan.mm_slot =
2467 mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
2468 khugepaged_scan.address = 0;
2470 khugepaged_scan.mm_slot = NULL;
2471 khugepaged_full_scans++;
2474 collect_mm_slot(mm_slot);
2480 static int khugepaged_has_work(void)
2482 return !list_empty(&khugepaged_scan.mm_head) &&
2483 hugepage_flags_enabled();
2486 static int khugepaged_wait_event(void)
2488 return !list_empty(&khugepaged_scan.mm_head) ||
2489 kthread_should_stop();
2492 static void khugepaged_do_scan(struct collapse_control *cc)
2494 unsigned int progress = 0, pass_through_head = 0;
2495 unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
2497 int result = SCAN_SUCCEED;
2499 lru_add_drain_all();
2504 if (unlikely(kthread_should_stop()))
2507 spin_lock(&khugepaged_mm_lock);
2508 if (!khugepaged_scan.mm_slot)
2509 pass_through_head++;
2510 if (khugepaged_has_work() &&
2511 pass_through_head < 2)
2512 progress += khugepaged_scan_mm_slot(pages - progress,
2516 spin_unlock(&khugepaged_mm_lock);
2518 if (progress >= pages)
2521 if (result == SCAN_ALLOC_HUGE_PAGE_FAIL) {
2523 * If fail to allocate the first time, try to sleep for
2524 * a while. When hit again, cancel the scan.
2529 khugepaged_alloc_sleep();
2534 static bool khugepaged_should_wakeup(void)
2536 return kthread_should_stop() ||
2537 time_after_eq(jiffies, khugepaged_sleep_expire);
2540 static void khugepaged_wait_work(void)
2542 if (khugepaged_has_work()) {
2543 const unsigned long scan_sleep_jiffies =
2544 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
2546 if (!scan_sleep_jiffies)
2549 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
2550 wait_event_freezable_timeout(khugepaged_wait,
2551 khugepaged_should_wakeup(),
2552 scan_sleep_jiffies);
2556 if (hugepage_flags_enabled())
2557 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2560 static int khugepaged(void *none)
2562 struct khugepaged_mm_slot *mm_slot;
2565 set_user_nice(current, MAX_NICE);
2567 while (!kthread_should_stop()) {
2568 khugepaged_do_scan(&khugepaged_collapse_control);
2569 khugepaged_wait_work();
2572 spin_lock(&khugepaged_mm_lock);
2573 mm_slot = khugepaged_scan.mm_slot;
2574 khugepaged_scan.mm_slot = NULL;
2576 collect_mm_slot(mm_slot);
2577 spin_unlock(&khugepaged_mm_lock);
2581 static void set_recommended_min_free_kbytes(void)
2585 unsigned long recommended_min;
2587 if (!hugepage_flags_enabled()) {
2588 calculate_min_free_kbytes();
2592 for_each_populated_zone(zone) {
2594 * We don't need to worry about fragmentation of
2595 * ZONE_MOVABLE since it only has movable pages.
2597 if (zone_idx(zone) > gfp_zone(GFP_USER))
2603 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
2604 recommended_min = pageblock_nr_pages * nr_zones * 2;
2607 * Make sure that on average at least two pageblocks are almost free
2608 * of another type, one for a migratetype to fall back to and a
2609 * second to avoid subsequent fallbacks of other types There are 3
2610 * MIGRATE_TYPES we care about.
2612 recommended_min += pageblock_nr_pages * nr_zones *
2613 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
2615 /* don't ever allow to reserve more than 5% of the lowmem */
2616 recommended_min = min(recommended_min,
2617 (unsigned long) nr_free_buffer_pages() / 20);
2618 recommended_min <<= (PAGE_SHIFT-10);
2620 if (recommended_min > min_free_kbytes) {
2621 if (user_min_free_kbytes >= 0)
2622 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
2623 min_free_kbytes, recommended_min);
2625 min_free_kbytes = recommended_min;
2629 setup_per_zone_wmarks();
2632 int start_stop_khugepaged(void)
2636 mutex_lock(&khugepaged_mutex);
2637 if (hugepage_flags_enabled()) {
2638 if (!khugepaged_thread)
2639 khugepaged_thread = kthread_run(khugepaged, NULL,
2641 if (IS_ERR(khugepaged_thread)) {
2642 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
2643 err = PTR_ERR(khugepaged_thread);
2644 khugepaged_thread = NULL;
2648 if (!list_empty(&khugepaged_scan.mm_head))
2649 wake_up_interruptible(&khugepaged_wait);
2650 } else if (khugepaged_thread) {
2651 kthread_stop(khugepaged_thread);
2652 khugepaged_thread = NULL;
2654 set_recommended_min_free_kbytes();
2656 mutex_unlock(&khugepaged_mutex);
2660 void khugepaged_min_free_kbytes_update(void)
2662 mutex_lock(&khugepaged_mutex);
2663 if (hugepage_flags_enabled() && khugepaged_thread)
2664 set_recommended_min_free_kbytes();
2665 mutex_unlock(&khugepaged_mutex);
2668 bool current_is_khugepaged(void)
2670 return kthread_func(current) == khugepaged;
2673 static int madvise_collapse_errno(enum scan_result r)
2676 * MADV_COLLAPSE breaks from existing madvise(2) conventions to provide
2677 * actionable feedback to caller, so they may take an appropriate
2678 * fallback measure depending on the nature of the failure.
2681 case SCAN_ALLOC_HUGE_PAGE_FAIL:
2683 case SCAN_CGROUP_CHARGE_FAIL:
2684 case SCAN_EXCEED_NONE_PTE:
2686 /* Resource temporary unavailable - trying again might succeed */
2687 case SCAN_PAGE_COUNT:
2688 case SCAN_PAGE_LOCK:
2690 case SCAN_DEL_PAGE_LRU:
2691 case SCAN_PAGE_FILLED:
2694 * Other: Trying again likely not to succeed / error intrinsic to
2695 * specified memory range. khugepaged likely won't be able to collapse
2703 int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
2704 unsigned long start, unsigned long end)
2706 struct collapse_control *cc;
2707 struct mm_struct *mm = vma->vm_mm;
2708 unsigned long hstart, hend, addr;
2709 int thps = 0, last_fail = SCAN_FAIL;
2710 bool mmap_locked = true;
2712 BUG_ON(vma->vm_start > start);
2713 BUG_ON(vma->vm_end < end);
2717 if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false, false,
2721 cc = kmalloc(sizeof(*cc), GFP_KERNEL);
2724 cc->is_khugepaged = false;
2727 lru_add_drain_all();
2729 hstart = (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2730 hend = end & HPAGE_PMD_MASK;
2732 for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) {
2733 int result = SCAN_FAIL;
2739 result = hugepage_vma_revalidate(mm, addr, false, &vma,
2741 if (result != SCAN_SUCCEED) {
2746 hend = min(hend, vma->vm_end & HPAGE_PMD_MASK);
2748 mmap_assert_locked(mm);
2749 memset(cc->node_load, 0, sizeof(cc->node_load));
2750 nodes_clear(cc->alloc_nmask);
2751 if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) {
2752 struct file *file = get_file(vma->vm_file);
2753 pgoff_t pgoff = linear_page_index(vma, addr);
2755 mmap_read_unlock(mm);
2756 mmap_locked = false;
2757 result = hpage_collapse_scan_file(mm, addr, file, pgoff,
2761 result = hpage_collapse_scan_pmd(mm, vma, addr,
2765 *prev = NULL; /* Tell caller we dropped mmap_lock */
2770 case SCAN_PMD_MAPPED:
2773 case SCAN_PTE_MAPPED_HUGEPAGE:
2774 BUG_ON(mmap_locked);
2777 result = collapse_pte_mapped_thp(mm, addr, true);
2778 mmap_read_unlock(mm);
2780 /* Whitelisted set of results where continuing OK */
2782 case SCAN_PTE_NON_PRESENT:
2783 case SCAN_PTE_UFFD_WP:
2785 case SCAN_LACK_REFERENCED_PAGE:
2786 case SCAN_PAGE_NULL:
2787 case SCAN_PAGE_COUNT:
2788 case SCAN_PAGE_LOCK:
2789 case SCAN_PAGE_COMPOUND:
2791 case SCAN_DEL_PAGE_LRU:
2796 /* Other error, exit */
2802 /* Caller expects us to hold mmap_lock on return */
2806 mmap_assert_locked(mm);
2810 return thps == ((hend - hstart) >> HPAGE_PMD_SHIFT) ? 0
2811 : madvise_collapse_errno(last_fail);