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/swapops.h>
20 #include <linux/shmem_fs.h>
23 #include <asm/pgalloc.h>
33 SCAN_LACK_REFERENCED_PAGE,
47 SCAN_ALLOC_HUGE_PAGE_FAIL,
48 SCAN_CGROUP_CHARGE_FAIL,
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/huge_memory.h>
56 /* default scan 8*512 pte (or vmas) every 30 second */
57 static unsigned int khugepaged_pages_to_scan __read_mostly;
58 static unsigned int khugepaged_pages_collapsed;
59 static unsigned int khugepaged_full_scans;
60 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
61 /* during fragmentation poll the hugepage allocator once every minute */
62 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
63 static unsigned long khugepaged_sleep_expire;
64 static DEFINE_SPINLOCK(khugepaged_mm_lock);
65 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
67 * default collapse hugepages if there is at least one pte mapped like
68 * it would have happened if the vma was large enough during page
71 static unsigned int khugepaged_max_ptes_none __read_mostly;
72 static unsigned int khugepaged_max_ptes_swap __read_mostly;
74 #define MM_SLOTS_HASH_BITS 10
75 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
77 static struct kmem_cache *mm_slot_cache __read_mostly;
80 * struct mm_slot - hash lookup from mm to mm_slot
81 * @hash: hash collision list
82 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
83 * @mm: the mm that this information is valid for
86 struct hlist_node hash;
87 struct list_head mm_node;
92 * struct khugepaged_scan - cursor for scanning
93 * @mm_head: the head of the mm list to scan
94 * @mm_slot: the current mm_slot we are scanning
95 * @address: the next address inside that to be scanned
97 * There is only the one khugepaged_scan instance of this cursor structure.
99 struct khugepaged_scan {
100 struct list_head mm_head;
101 struct mm_slot *mm_slot;
102 unsigned long address;
105 static struct khugepaged_scan khugepaged_scan = {
106 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
110 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
111 struct kobj_attribute *attr,
114 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
117 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
118 struct kobj_attribute *attr,
119 const char *buf, size_t count)
124 err = kstrtoul(buf, 10, &msecs);
125 if (err || msecs > UINT_MAX)
128 khugepaged_scan_sleep_millisecs = msecs;
129 khugepaged_sleep_expire = 0;
130 wake_up_interruptible(&khugepaged_wait);
134 static struct kobj_attribute scan_sleep_millisecs_attr =
135 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
136 scan_sleep_millisecs_store);
138 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
139 struct kobj_attribute *attr,
142 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
145 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
146 struct kobj_attribute *attr,
147 const char *buf, size_t count)
152 err = kstrtoul(buf, 10, &msecs);
153 if (err || msecs > UINT_MAX)
156 khugepaged_alloc_sleep_millisecs = msecs;
157 khugepaged_sleep_expire = 0;
158 wake_up_interruptible(&khugepaged_wait);
162 static struct kobj_attribute alloc_sleep_millisecs_attr =
163 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
164 alloc_sleep_millisecs_store);
166 static ssize_t pages_to_scan_show(struct kobject *kobj,
167 struct kobj_attribute *attr,
170 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
172 static ssize_t pages_to_scan_store(struct kobject *kobj,
173 struct kobj_attribute *attr,
174 const char *buf, size_t count)
179 err = kstrtoul(buf, 10, &pages);
180 if (err || !pages || pages > UINT_MAX)
183 khugepaged_pages_to_scan = pages;
187 static struct kobj_attribute pages_to_scan_attr =
188 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
189 pages_to_scan_store);
191 static ssize_t pages_collapsed_show(struct kobject *kobj,
192 struct kobj_attribute *attr,
195 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
197 static struct kobj_attribute pages_collapsed_attr =
198 __ATTR_RO(pages_collapsed);
200 static ssize_t full_scans_show(struct kobject *kobj,
201 struct kobj_attribute *attr,
204 return sprintf(buf, "%u\n", khugepaged_full_scans);
206 static struct kobj_attribute full_scans_attr =
207 __ATTR_RO(full_scans);
209 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
210 struct kobj_attribute *attr, char *buf)
212 return single_hugepage_flag_show(kobj, attr, buf,
213 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
215 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
216 struct kobj_attribute *attr,
217 const char *buf, size_t count)
219 return single_hugepage_flag_store(kobj, attr, buf, count,
220 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
222 static struct kobj_attribute khugepaged_defrag_attr =
223 __ATTR(defrag, 0644, khugepaged_defrag_show,
224 khugepaged_defrag_store);
227 * max_ptes_none controls if khugepaged should collapse hugepages over
228 * any unmapped ptes in turn potentially increasing the memory
229 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
230 * reduce the available free memory in the system as it
231 * runs. Increasing max_ptes_none will instead potentially reduce the
232 * free memory in the system during the khugepaged scan.
234 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
235 struct kobj_attribute *attr,
238 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
240 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
241 struct kobj_attribute *attr,
242 const char *buf, size_t count)
245 unsigned long max_ptes_none;
247 err = kstrtoul(buf, 10, &max_ptes_none);
248 if (err || max_ptes_none > HPAGE_PMD_NR-1)
251 khugepaged_max_ptes_none = max_ptes_none;
255 static struct kobj_attribute khugepaged_max_ptes_none_attr =
256 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
257 khugepaged_max_ptes_none_store);
259 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
260 struct kobj_attribute *attr,
263 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
266 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
267 struct kobj_attribute *attr,
268 const char *buf, size_t count)
271 unsigned long max_ptes_swap;
273 err = kstrtoul(buf, 10, &max_ptes_swap);
274 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
277 khugepaged_max_ptes_swap = max_ptes_swap;
282 static struct kobj_attribute khugepaged_max_ptes_swap_attr =
283 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
284 khugepaged_max_ptes_swap_store);
286 static struct attribute *khugepaged_attr[] = {
287 &khugepaged_defrag_attr.attr,
288 &khugepaged_max_ptes_none_attr.attr,
289 &pages_to_scan_attr.attr,
290 &pages_collapsed_attr.attr,
291 &full_scans_attr.attr,
292 &scan_sleep_millisecs_attr.attr,
293 &alloc_sleep_millisecs_attr.attr,
294 &khugepaged_max_ptes_swap_attr.attr,
298 struct attribute_group khugepaged_attr_group = {
299 .attrs = khugepaged_attr,
300 .name = "khugepaged",
302 #endif /* CONFIG_SYSFS */
304 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
306 int hugepage_madvise(struct vm_area_struct *vma,
307 unsigned long *vm_flags, int advice)
313 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
314 * can't handle this properly after s390_enable_sie, so we simply
315 * ignore the madvise to prevent qemu from causing a SIGSEGV.
317 if (mm_has_pgste(vma->vm_mm))
320 *vm_flags &= ~VM_NOHUGEPAGE;
321 *vm_flags |= VM_HUGEPAGE;
323 * If the vma become good for khugepaged to scan,
324 * register it here without waiting a page fault that
325 * may not happen any time soon.
327 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
328 khugepaged_enter_vma_merge(vma, *vm_flags))
331 case MADV_NOHUGEPAGE:
332 *vm_flags &= ~VM_HUGEPAGE;
333 *vm_flags |= VM_NOHUGEPAGE;
335 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
336 * this vma even if we leave the mm registered in khugepaged if
337 * it got registered before VM_NOHUGEPAGE was set.
345 int __init khugepaged_init(void)
347 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
348 sizeof(struct mm_slot),
349 __alignof__(struct mm_slot), 0, NULL);
353 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
354 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
355 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
360 void __init khugepaged_destroy(void)
362 kmem_cache_destroy(mm_slot_cache);
365 static inline struct mm_slot *alloc_mm_slot(void)
367 if (!mm_slot_cache) /* initialization failed */
369 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
372 static inline void free_mm_slot(struct mm_slot *mm_slot)
374 kmem_cache_free(mm_slot_cache, mm_slot);
377 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
379 struct mm_slot *mm_slot;
381 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
382 if (mm == mm_slot->mm)
388 static void insert_to_mm_slots_hash(struct mm_struct *mm,
389 struct mm_slot *mm_slot)
392 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
395 static inline int khugepaged_test_exit(struct mm_struct *mm)
397 return atomic_read(&mm->mm_users) == 0;
400 int __khugepaged_enter(struct mm_struct *mm)
402 struct mm_slot *mm_slot;
405 mm_slot = alloc_mm_slot();
409 /* __khugepaged_exit() must not run from under us */
410 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
411 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
412 free_mm_slot(mm_slot);
416 spin_lock(&khugepaged_mm_lock);
417 insert_to_mm_slots_hash(mm, mm_slot);
419 * Insert just behind the scanning cursor, to let the area settle
422 wakeup = list_empty(&khugepaged_scan.mm_head);
423 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
424 spin_unlock(&khugepaged_mm_lock);
428 wake_up_interruptible(&khugepaged_wait);
433 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
434 unsigned long vm_flags)
436 unsigned long hstart, hend;
439 * Not yet faulted in so we will register later in the
440 * page fault if needed.
443 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
444 /* khugepaged not yet working on file or special mappings */
446 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
447 hend = vma->vm_end & HPAGE_PMD_MASK;
449 return khugepaged_enter(vma, vm_flags);
453 void __khugepaged_exit(struct mm_struct *mm)
455 struct mm_slot *mm_slot;
458 spin_lock(&khugepaged_mm_lock);
459 mm_slot = get_mm_slot(mm);
460 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
461 hash_del(&mm_slot->hash);
462 list_del(&mm_slot->mm_node);
465 spin_unlock(&khugepaged_mm_lock);
468 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
469 free_mm_slot(mm_slot);
471 } else if (mm_slot) {
473 * This is required to serialize against
474 * khugepaged_test_exit() (which is guaranteed to run
475 * under mmap sem read mode). Stop here (after we
476 * return all pagetables will be destroyed) until
477 * khugepaged has finished working on the pagetables
478 * under the mmap_sem.
480 down_write(&mm->mmap_sem);
481 up_write(&mm->mmap_sem);
485 static void release_pte_page(struct page *page)
487 dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
489 putback_lru_page(page);
492 static void release_pte_pages(pte_t *pte, pte_t *_pte)
494 while (--_pte >= pte) {
495 pte_t pteval = *_pte;
496 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
497 release_pte_page(pte_page(pteval));
501 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
502 unsigned long address,
505 struct page *page = NULL;
507 int none_or_zero = 0, result = 0, referenced = 0;
508 bool writable = false;
510 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
511 _pte++, address += PAGE_SIZE) {
512 pte_t pteval = *_pte;
513 if (pte_none(pteval) || (pte_present(pteval) &&
514 is_zero_pfn(pte_pfn(pteval)))) {
515 if (!userfaultfd_armed(vma) &&
516 ++none_or_zero <= khugepaged_max_ptes_none) {
519 result = SCAN_EXCEED_NONE_PTE;
523 if (!pte_present(pteval)) {
524 result = SCAN_PTE_NON_PRESENT;
527 page = vm_normal_page(vma, address, pteval);
528 if (unlikely(!page)) {
529 result = SCAN_PAGE_NULL;
533 VM_BUG_ON_PAGE(PageCompound(page), page);
534 VM_BUG_ON_PAGE(!PageAnon(page), page);
537 * We can do it before isolate_lru_page because the
538 * page can't be freed from under us. NOTE: PG_lock
539 * is needed to serialize against split_huge_page
540 * when invoked from the VM.
542 if (!trylock_page(page)) {
543 result = SCAN_PAGE_LOCK;
548 * cannot use mapcount: can't collapse if there's a gup pin.
549 * The page must only be referenced by the scanned process
550 * and page swap cache.
552 if (page_count(page) != 1 + PageSwapCache(page)) {
554 result = SCAN_PAGE_COUNT;
557 if (pte_write(pteval)) {
560 if (PageSwapCache(page) &&
561 !reuse_swap_page(page, NULL)) {
563 result = SCAN_SWAP_CACHE_PAGE;
567 * Page is not in the swap cache. It can be collapsed
573 * Isolate the page to avoid collapsing an hugepage
574 * currently in use by the VM.
576 if (isolate_lru_page(page)) {
578 result = SCAN_DEL_PAGE_LRU;
581 inc_node_page_state(page,
582 NR_ISOLATED_ANON + page_is_file_cache(page));
583 VM_BUG_ON_PAGE(!PageLocked(page), page);
584 VM_BUG_ON_PAGE(PageLRU(page), page);
586 /* There should be enough young pte to collapse the page */
587 if (pte_young(pteval) ||
588 page_is_young(page) || PageReferenced(page) ||
589 mmu_notifier_test_young(vma->vm_mm, address))
592 if (likely(writable)) {
593 if (likely(referenced)) {
594 result = SCAN_SUCCEED;
595 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
596 referenced, writable, result);
600 result = SCAN_PAGE_RO;
604 release_pte_pages(pte, _pte);
605 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
606 referenced, writable, result);
610 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
611 struct vm_area_struct *vma,
612 unsigned long address,
616 for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
617 _pte++, page++, address += PAGE_SIZE) {
618 pte_t pteval = *_pte;
619 struct page *src_page;
621 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
622 clear_user_highpage(page, address);
623 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
624 if (is_zero_pfn(pte_pfn(pteval))) {
626 * ptl mostly unnecessary.
630 * paravirt calls inside pte_clear here are
633 pte_clear(vma->vm_mm, address, _pte);
637 src_page = pte_page(pteval);
638 copy_user_highpage(page, src_page, address, vma);
639 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
640 release_pte_page(src_page);
642 * ptl mostly unnecessary, but preempt has to
643 * be disabled to update the per-cpu stats
644 * inside page_remove_rmap().
648 * paravirt calls inside pte_clear here are
651 pte_clear(vma->vm_mm, address, _pte);
652 page_remove_rmap(src_page, false);
654 free_page_and_swap_cache(src_page);
659 static void khugepaged_alloc_sleep(void)
663 add_wait_queue(&khugepaged_wait, &wait);
664 freezable_schedule_timeout_interruptible(
665 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
666 remove_wait_queue(&khugepaged_wait, &wait);
669 static int khugepaged_node_load[MAX_NUMNODES];
671 static bool khugepaged_scan_abort(int nid)
676 * If node_reclaim_mode is disabled, then no extra effort is made to
677 * allocate memory locally.
679 if (!node_reclaim_mode)
682 /* If there is a count for this node already, it must be acceptable */
683 if (khugepaged_node_load[nid])
686 for (i = 0; i < MAX_NUMNODES; i++) {
687 if (!khugepaged_node_load[i])
689 if (node_distance(nid, i) > RECLAIM_DISTANCE)
695 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
696 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
698 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
702 static int khugepaged_find_target_node(void)
704 static int last_khugepaged_target_node = NUMA_NO_NODE;
705 int nid, target_node = 0, max_value = 0;
707 /* find first node with max normal pages hit */
708 for (nid = 0; nid < MAX_NUMNODES; nid++)
709 if (khugepaged_node_load[nid] > max_value) {
710 max_value = khugepaged_node_load[nid];
714 /* do some balance if several nodes have the same hit record */
715 if (target_node <= last_khugepaged_target_node)
716 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
718 if (max_value == khugepaged_node_load[nid]) {
723 last_khugepaged_target_node = target_node;
727 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
729 if (IS_ERR(*hpage)) {
735 khugepaged_alloc_sleep();
745 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
747 VM_BUG_ON_PAGE(*hpage, *hpage);
749 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
750 if (unlikely(!*hpage)) {
751 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
752 *hpage = ERR_PTR(-ENOMEM);
756 prep_transhuge_page(*hpage);
757 count_vm_event(THP_COLLAPSE_ALLOC);
761 static int khugepaged_find_target_node(void)
766 static inline struct page *alloc_khugepaged_hugepage(void)
770 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
773 prep_transhuge_page(page);
777 static struct page *khugepaged_alloc_hugepage(bool *wait)
782 hpage = alloc_khugepaged_hugepage();
784 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
789 khugepaged_alloc_sleep();
791 count_vm_event(THP_COLLAPSE_ALLOC);
792 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
797 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
800 *hpage = khugepaged_alloc_hugepage(wait);
802 if (unlikely(!*hpage))
809 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
817 static bool hugepage_vma_check(struct vm_area_struct *vma)
819 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
820 (vma->vm_flags & VM_NOHUGEPAGE) ||
821 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
823 if (shmem_file(vma->vm_file)) {
824 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
826 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
829 if (!vma->anon_vma || vma->vm_ops)
831 if (is_vma_temporary_stack(vma))
833 return !(vma->vm_flags & VM_NO_KHUGEPAGED);
837 * If mmap_sem temporarily dropped, revalidate vma
838 * before taking mmap_sem.
839 * Return 0 if succeeds, otherwise return none-zero
843 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
844 struct vm_area_struct **vmap)
846 struct vm_area_struct *vma;
847 unsigned long hstart, hend;
849 if (unlikely(khugepaged_test_exit(mm)))
850 return SCAN_ANY_PROCESS;
852 *vmap = vma = find_vma(mm, address);
854 return SCAN_VMA_NULL;
856 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
857 hend = vma->vm_end & HPAGE_PMD_MASK;
858 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
859 return SCAN_ADDRESS_RANGE;
860 if (!hugepage_vma_check(vma))
861 return SCAN_VMA_CHECK;
866 * Bring missing pages in from swap, to complete THP collapse.
867 * Only done if khugepaged_scan_pmd believes it is worthwhile.
869 * Called and returns without pte mapped or spinlocks held,
870 * but with mmap_sem held to protect against vma changes.
873 static bool __collapse_huge_page_swapin(struct mm_struct *mm,
874 struct vm_area_struct *vma,
875 unsigned long address, pmd_t *pmd,
878 int swapped_in = 0, ret = 0;
879 struct vm_fault vmf = {
882 .flags = FAULT_FLAG_ALLOW_RETRY,
884 .pgoff = linear_page_index(vma, address),
887 /* we only decide to swapin, if there is enough young ptes */
888 if (referenced < HPAGE_PMD_NR/2) {
889 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
892 vmf.pte = pte_offset_map(pmd, address);
893 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
894 vmf.pte++, vmf.address += PAGE_SIZE) {
895 vmf.orig_pte = *vmf.pte;
896 if (!is_swap_pte(vmf.orig_pte))
899 ret = do_swap_page(&vmf);
901 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
902 if (ret & VM_FAULT_RETRY) {
903 down_read(&mm->mmap_sem);
904 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {
905 /* vma is no longer available, don't continue to swapin */
906 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
909 /* check if the pmd is still valid */
910 if (mm_find_pmd(mm, address) != pmd) {
911 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
915 if (ret & VM_FAULT_ERROR) {
916 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
919 /* pte is unmapped now, we need to map it */
920 vmf.pte = pte_offset_map(pmd, vmf.address);
924 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
928 static void collapse_huge_page(struct mm_struct *mm,
929 unsigned long address,
931 int node, int referenced)
936 struct page *new_page;
937 spinlock_t *pmd_ptl, *pte_ptl;
938 int isolated = 0, result = 0;
939 struct mem_cgroup *memcg;
940 struct vm_area_struct *vma;
941 unsigned long mmun_start; /* For mmu_notifiers */
942 unsigned long mmun_end; /* For mmu_notifiers */
945 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
947 /* Only allocate from the target node */
948 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
951 * Before allocating the hugepage, release the mmap_sem read lock.
952 * The allocation can take potentially a long time if it involves
953 * sync compaction, and we do not need to hold the mmap_sem during
954 * that. We will recheck the vma after taking it again in write mode.
956 up_read(&mm->mmap_sem);
957 new_page = khugepaged_alloc_page(hpage, gfp, node);
959 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
963 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
964 result = SCAN_CGROUP_CHARGE_FAIL;
968 down_read(&mm->mmap_sem);
969 result = hugepage_vma_revalidate(mm, address, &vma);
971 mem_cgroup_cancel_charge(new_page, memcg, true);
972 up_read(&mm->mmap_sem);
976 pmd = mm_find_pmd(mm, address);
978 result = SCAN_PMD_NULL;
979 mem_cgroup_cancel_charge(new_page, memcg, true);
980 up_read(&mm->mmap_sem);
985 * __collapse_huge_page_swapin always returns with mmap_sem locked.
986 * If it fails, we release mmap_sem and jump out_nolock.
987 * Continuing to collapse causes inconsistency.
989 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
990 mem_cgroup_cancel_charge(new_page, memcg, true);
991 up_read(&mm->mmap_sem);
995 up_read(&mm->mmap_sem);
997 * Prevent all access to pagetables with the exception of
998 * gup_fast later handled by the ptep_clear_flush and the VM
999 * handled by the anon_vma lock + PG_lock.
1001 down_write(&mm->mmap_sem);
1002 result = hugepage_vma_revalidate(mm, address, &vma);
1005 /* check if the pmd is still valid */
1006 if (mm_find_pmd(mm, address) != pmd)
1009 anon_vma_lock_write(vma->anon_vma);
1011 pte = pte_offset_map(pmd, address);
1012 pte_ptl = pte_lockptr(mm, pmd);
1014 mmun_start = address;
1015 mmun_end = address + HPAGE_PMD_SIZE;
1016 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1017 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1019 * After this gup_fast can't run anymore. This also removes
1020 * any huge TLB entry from the CPU so we won't allow
1021 * huge and small TLB entries for the same virtual address
1022 * to avoid the risk of CPU bugs in that area.
1024 _pmd = pmdp_collapse_flush(vma, address, pmd);
1025 spin_unlock(pmd_ptl);
1026 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1029 isolated = __collapse_huge_page_isolate(vma, address, pte);
1030 spin_unlock(pte_ptl);
1032 if (unlikely(!isolated)) {
1035 BUG_ON(!pmd_none(*pmd));
1037 * We can only use set_pmd_at when establishing
1038 * hugepmds and never for establishing regular pmds that
1039 * points to regular pagetables. Use pmd_populate for that
1041 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1042 spin_unlock(pmd_ptl);
1043 anon_vma_unlock_write(vma->anon_vma);
1049 * All pages are isolated and locked so anon_vma rmap
1050 * can't run anymore.
1052 anon_vma_unlock_write(vma->anon_vma);
1054 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
1056 __SetPageUptodate(new_page);
1057 pgtable = pmd_pgtable(_pmd);
1059 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1060 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1063 * spin_lock() below is not the equivalent of smp_wmb(), so
1064 * this is needed to avoid the copy_huge_page writes to become
1065 * visible after the set_pmd_at() write.
1070 BUG_ON(!pmd_none(*pmd));
1071 page_add_new_anon_rmap(new_page, vma, address, true);
1072 mem_cgroup_commit_charge(new_page, memcg, false, true);
1073 lru_cache_add_active_or_unevictable(new_page, vma);
1074 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1075 set_pmd_at(mm, address, pmd, _pmd);
1076 update_mmu_cache_pmd(vma, address, pmd);
1077 spin_unlock(pmd_ptl);
1081 khugepaged_pages_collapsed++;
1082 result = SCAN_SUCCEED;
1084 up_write(&mm->mmap_sem);
1086 trace_mm_collapse_huge_page(mm, isolated, result);
1089 mem_cgroup_cancel_charge(new_page, memcg, true);
1093 static int khugepaged_scan_pmd(struct mm_struct *mm,
1094 struct vm_area_struct *vma,
1095 unsigned long address,
1096 struct page **hpage)
1100 int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
1101 struct page *page = NULL;
1102 unsigned long _address;
1104 int node = NUMA_NO_NODE, unmapped = 0;
1105 bool writable = false;
1107 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1109 pmd = mm_find_pmd(mm, address);
1111 result = SCAN_PMD_NULL;
1115 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1116 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1117 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1118 _pte++, _address += PAGE_SIZE) {
1119 pte_t pteval = *_pte;
1120 if (is_swap_pte(pteval)) {
1121 if (++unmapped <= khugepaged_max_ptes_swap) {
1124 result = SCAN_EXCEED_SWAP_PTE;
1128 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1129 if (!userfaultfd_armed(vma) &&
1130 ++none_or_zero <= khugepaged_max_ptes_none) {
1133 result = SCAN_EXCEED_NONE_PTE;
1137 if (!pte_present(pteval)) {
1138 result = SCAN_PTE_NON_PRESENT;
1141 if (pte_write(pteval))
1144 page = vm_normal_page(vma, _address, pteval);
1145 if (unlikely(!page)) {
1146 result = SCAN_PAGE_NULL;
1150 /* TODO: teach khugepaged to collapse THP mapped with pte */
1151 if (PageCompound(page)) {
1152 result = SCAN_PAGE_COMPOUND;
1157 * Record which node the original page is from and save this
1158 * information to khugepaged_node_load[].
1159 * Khupaged will allocate hugepage from the node has the max
1162 node = page_to_nid(page);
1163 if (khugepaged_scan_abort(node)) {
1164 result = SCAN_SCAN_ABORT;
1167 khugepaged_node_load[node]++;
1168 if (!PageLRU(page)) {
1169 result = SCAN_PAGE_LRU;
1172 if (PageLocked(page)) {
1173 result = SCAN_PAGE_LOCK;
1176 if (!PageAnon(page)) {
1177 result = SCAN_PAGE_ANON;
1182 * cannot use mapcount: can't collapse if there's a gup pin.
1183 * The page must only be referenced by the scanned process
1184 * and page swap cache.
1186 if (page_count(page) != 1 + PageSwapCache(page)) {
1187 result = SCAN_PAGE_COUNT;
1190 if (pte_young(pteval) ||
1191 page_is_young(page) || PageReferenced(page) ||
1192 mmu_notifier_test_young(vma->vm_mm, address))
1197 result = SCAN_SUCCEED;
1200 result = SCAN_LACK_REFERENCED_PAGE;
1203 result = SCAN_PAGE_RO;
1206 pte_unmap_unlock(pte, ptl);
1208 node = khugepaged_find_target_node();
1209 /* collapse_huge_page will return with the mmap_sem released */
1210 collapse_huge_page(mm, address, hpage, node, referenced);
1213 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1214 none_or_zero, result, unmapped);
1218 static void collect_mm_slot(struct mm_slot *mm_slot)
1220 struct mm_struct *mm = mm_slot->mm;
1222 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1224 if (khugepaged_test_exit(mm)) {
1226 hash_del(&mm_slot->hash);
1227 list_del(&mm_slot->mm_node);
1230 * Not strictly needed because the mm exited already.
1232 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1235 /* khugepaged_mm_lock actually not necessary for the below */
1236 free_mm_slot(mm_slot);
1241 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
1242 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1244 struct vm_area_struct *vma;
1248 i_mmap_lock_write(mapping);
1249 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1250 /* probably overkill */
1253 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1254 if (addr & ~HPAGE_PMD_MASK)
1256 if (vma->vm_end < addr + HPAGE_PMD_SIZE)
1258 pmd = mm_find_pmd(vma->vm_mm, addr);
1262 * We need exclusive mmap_sem to retract page table.
1263 * If trylock fails we would end up with pte-mapped THP after
1264 * re-fault. Not ideal, but it's more important to not disturb
1265 * the system too much.
1267 if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
1268 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
1269 /* assume page table is clear */
1270 _pmd = pmdp_collapse_flush(vma, addr, pmd);
1272 up_write(&vma->vm_mm->mmap_sem);
1273 mm_dec_nr_ptes(vma->vm_mm);
1274 pte_free(vma->vm_mm, pmd_pgtable(_pmd));
1277 i_mmap_unlock_write(mapping);
1281 * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
1283 * Basic scheme is simple, details are more complex:
1284 * - allocate and freeze a new huge page;
1285 * - scan over radix tree replacing old pages the new one
1286 * + swap in pages if necessary;
1288 * + keep old pages around in case if rollback is required;
1289 * - if replacing succeed:
1292 * + unfreeze huge page;
1293 * - if replacing failed;
1294 * + put all pages back and unfreeze them;
1295 * + restore gaps in the radix-tree;
1298 static void collapse_shmem(struct mm_struct *mm,
1299 struct address_space *mapping, pgoff_t start,
1300 struct page **hpage, int node)
1303 struct page *page, *new_page, *tmp;
1304 struct mem_cgroup *memcg;
1305 pgoff_t index, end = start + HPAGE_PMD_NR;
1306 LIST_HEAD(pagelist);
1307 struct radix_tree_iter iter;
1309 int nr_none = 0, result = SCAN_SUCCEED;
1311 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1313 /* Only allocate from the target node */
1314 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
1316 new_page = khugepaged_alloc_page(hpage, gfp, node);
1318 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1322 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
1323 result = SCAN_CGROUP_CHARGE_FAIL;
1327 new_page->index = start;
1328 new_page->mapping = mapping;
1329 __SetPageSwapBacked(new_page);
1330 __SetPageLocked(new_page);
1331 BUG_ON(!page_ref_freeze(new_page, 1));
1335 * At this point the new_page is 'frozen' (page_count() is zero), locked
1336 * and not up-to-date. It's safe to insert it into radix tree, because
1337 * nobody would be able to map it or use it in other way until we
1342 spin_lock_irq(&mapping->tree_lock);
1343 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1344 int n = min(iter.index, end) - index;
1347 * Handle holes in the radix tree: charge it from shmem and
1348 * insert relevant subpage of new_page into the radix-tree.
1350 if (n && !shmem_charge(mapping->host, n)) {
1355 for (; index < min(iter.index, end); index++) {
1356 radix_tree_insert(&mapping->page_tree, index,
1357 new_page + (index % HPAGE_PMD_NR));
1364 page = radix_tree_deref_slot_protected(slot,
1365 &mapping->tree_lock);
1366 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) {
1367 spin_unlock_irq(&mapping->tree_lock);
1368 /* swap in or instantiate fallocated page */
1369 if (shmem_getpage(mapping->host, index, &page,
1374 spin_lock_irq(&mapping->tree_lock);
1375 } else if (trylock_page(page)) {
1378 result = SCAN_PAGE_LOCK;
1383 * The page must be locked, so we can drop the tree_lock
1384 * without racing with truncate.
1386 VM_BUG_ON_PAGE(!PageLocked(page), page);
1387 VM_BUG_ON_PAGE(!PageUptodate(page), page);
1388 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1390 if (page_mapping(page) != mapping) {
1391 result = SCAN_TRUNCATED;
1394 spin_unlock_irq(&mapping->tree_lock);
1396 if (isolate_lru_page(page)) {
1397 result = SCAN_DEL_PAGE_LRU;
1398 goto out_isolate_failed;
1401 if (page_mapped(page))
1402 unmap_mapping_range(mapping, index << PAGE_SHIFT,
1405 spin_lock_irq(&mapping->tree_lock);
1407 slot = radix_tree_lookup_slot(&mapping->page_tree, index);
1408 VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
1409 &mapping->tree_lock), page);
1410 VM_BUG_ON_PAGE(page_mapped(page), page);
1413 * The page is expected to have page_count() == 3:
1414 * - we hold a pin on it;
1415 * - one reference from radix tree;
1416 * - one from isolate_lru_page;
1418 if (!page_ref_freeze(page, 3)) {
1419 result = SCAN_PAGE_COUNT;
1424 * Add the page to the list to be able to undo the collapse if
1425 * something go wrong.
1427 list_add_tail(&page->lru, &pagelist);
1429 /* Finally, replace with the new page. */
1430 radix_tree_replace_slot(&mapping->page_tree, slot,
1431 new_page + (index % HPAGE_PMD_NR));
1433 slot = radix_tree_iter_resume(slot, &iter);
1437 spin_unlock_irq(&mapping->tree_lock);
1438 putback_lru_page(page);
1450 * Handle hole in radix tree at the end of the range.
1451 * This code only triggers if there's nothing in radix tree
1454 if (result == SCAN_SUCCEED && index < end) {
1455 int n = end - index;
1457 if (!shmem_charge(mapping->host, n)) {
1462 for (; index < end; index++) {
1463 radix_tree_insert(&mapping->page_tree, index,
1464 new_page + (index % HPAGE_PMD_NR));
1470 spin_unlock_irq(&mapping->tree_lock);
1473 if (result == SCAN_SUCCEED) {
1474 unsigned long flags;
1475 struct zone *zone = page_zone(new_page);
1478 * Replacing old pages with new one has succeed, now we need to
1479 * copy the content and free old pages.
1481 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
1482 copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
1484 list_del(&page->lru);
1486 page_ref_unfreeze(page, 1);
1487 page->mapping = NULL;
1488 ClearPageActive(page);
1489 ClearPageUnevictable(page);
1493 local_irq_save(flags);
1494 __inc_node_page_state(new_page, NR_SHMEM_THPS);
1496 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
1497 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
1499 local_irq_restore(flags);
1502 * Remove pte page tables, so we can re-faulti
1505 retract_page_tables(mapping, start);
1507 /* Everything is ready, let's unfreeze the new_page */
1508 set_page_dirty(new_page);
1509 SetPageUptodate(new_page);
1510 page_ref_unfreeze(new_page, HPAGE_PMD_NR);
1511 mem_cgroup_commit_charge(new_page, memcg, false, true);
1512 lru_cache_add_anon(new_page);
1513 unlock_page(new_page);
1517 /* Something went wrong: rollback changes to the radix-tree */
1518 shmem_uncharge(mapping->host, nr_none);
1519 spin_lock_irq(&mapping->tree_lock);
1520 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
1522 if (iter.index >= end)
1524 page = list_first_entry_or_null(&pagelist,
1526 if (!page || iter.index < page->index) {
1530 /* Put holes back where they were */
1531 radix_tree_delete(&mapping->page_tree,
1536 VM_BUG_ON_PAGE(page->index != iter.index, page);
1538 /* Unfreeze the page. */
1539 list_del(&page->lru);
1540 page_ref_unfreeze(page, 2);
1541 radix_tree_replace_slot(&mapping->page_tree,
1543 slot = radix_tree_iter_resume(slot, &iter);
1544 spin_unlock_irq(&mapping->tree_lock);
1545 putback_lru_page(page);
1547 spin_lock_irq(&mapping->tree_lock);
1550 spin_unlock_irq(&mapping->tree_lock);
1552 /* Unfreeze new_page, caller would take care about freeing it */
1553 page_ref_unfreeze(new_page, 1);
1554 mem_cgroup_cancel_charge(new_page, memcg, true);
1555 unlock_page(new_page);
1556 new_page->mapping = NULL;
1559 VM_BUG_ON(!list_empty(&pagelist));
1560 /* TODO: tracepoints */
1563 static void khugepaged_scan_shmem(struct mm_struct *mm,
1564 struct address_space *mapping,
1565 pgoff_t start, struct page **hpage)
1567 struct page *page = NULL;
1568 struct radix_tree_iter iter;
1571 int node = NUMA_NO_NODE;
1572 int result = SCAN_SUCCEED;
1576 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1578 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1579 if (iter.index >= start + HPAGE_PMD_NR)
1582 page = radix_tree_deref_slot(slot);
1583 if (radix_tree_deref_retry(page)) {
1584 slot = radix_tree_iter_retry(&iter);
1588 if (radix_tree_exception(page)) {
1589 if (++swap > khugepaged_max_ptes_swap) {
1590 result = SCAN_EXCEED_SWAP_PTE;
1596 if (PageTransCompound(page)) {
1597 result = SCAN_PAGE_COMPOUND;
1601 node = page_to_nid(page);
1602 if (khugepaged_scan_abort(node)) {
1603 result = SCAN_SCAN_ABORT;
1606 khugepaged_node_load[node]++;
1608 if (!PageLRU(page)) {
1609 result = SCAN_PAGE_LRU;
1613 if (page_count(page) != 1 + page_mapcount(page)) {
1614 result = SCAN_PAGE_COUNT;
1619 * We probably should check if the page is referenced here, but
1620 * nobody would transfer pte_young() to PageReferenced() for us.
1621 * And rmap walk here is just too costly...
1626 if (need_resched()) {
1627 slot = radix_tree_iter_resume(slot, &iter);
1633 if (result == SCAN_SUCCEED) {
1634 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
1635 result = SCAN_EXCEED_NONE_PTE;
1637 node = khugepaged_find_target_node();
1638 collapse_shmem(mm, mapping, start, hpage, node);
1642 /* TODO: tracepoints */
1645 static void khugepaged_scan_shmem(struct mm_struct *mm,
1646 struct address_space *mapping,
1647 pgoff_t start, struct page **hpage)
1653 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1654 struct page **hpage)
1655 __releases(&khugepaged_mm_lock)
1656 __acquires(&khugepaged_mm_lock)
1658 struct mm_slot *mm_slot;
1659 struct mm_struct *mm;
1660 struct vm_area_struct *vma;
1664 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1666 if (khugepaged_scan.mm_slot)
1667 mm_slot = khugepaged_scan.mm_slot;
1669 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1670 struct mm_slot, mm_node);
1671 khugepaged_scan.address = 0;
1672 khugepaged_scan.mm_slot = mm_slot;
1674 spin_unlock(&khugepaged_mm_lock);
1677 down_read(&mm->mmap_sem);
1678 if (unlikely(khugepaged_test_exit(mm)))
1681 vma = find_vma(mm, khugepaged_scan.address);
1684 for (; vma; vma = vma->vm_next) {
1685 unsigned long hstart, hend;
1688 if (unlikely(khugepaged_test_exit(mm))) {
1692 if (!hugepage_vma_check(vma)) {
1697 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1698 hend = vma->vm_end & HPAGE_PMD_MASK;
1701 if (khugepaged_scan.address > hend)
1703 if (khugepaged_scan.address < hstart)
1704 khugepaged_scan.address = hstart;
1705 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1707 while (khugepaged_scan.address < hend) {
1710 if (unlikely(khugepaged_test_exit(mm)))
1711 goto breakouterloop;
1713 VM_BUG_ON(khugepaged_scan.address < hstart ||
1714 khugepaged_scan.address + HPAGE_PMD_SIZE >
1716 if (shmem_file(vma->vm_file)) {
1718 pgoff_t pgoff = linear_page_index(vma,
1719 khugepaged_scan.address);
1720 if (!shmem_huge_enabled(vma))
1722 file = get_file(vma->vm_file);
1723 up_read(&mm->mmap_sem);
1725 khugepaged_scan_shmem(mm, file->f_mapping,
1729 ret = khugepaged_scan_pmd(mm, vma,
1730 khugepaged_scan.address,
1733 /* move to next address */
1734 khugepaged_scan.address += HPAGE_PMD_SIZE;
1735 progress += HPAGE_PMD_NR;
1737 /* we released mmap_sem so break loop */
1738 goto breakouterloop_mmap_sem;
1739 if (progress >= pages)
1740 goto breakouterloop;
1744 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1745 breakouterloop_mmap_sem:
1747 spin_lock(&khugepaged_mm_lock);
1748 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1750 * Release the current mm_slot if this mm is about to die, or
1751 * if we scanned all vmas of this mm.
1753 if (khugepaged_test_exit(mm) || !vma) {
1755 * Make sure that if mm_users is reaching zero while
1756 * khugepaged runs here, khugepaged_exit will find
1757 * mm_slot not pointing to the exiting mm.
1759 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1760 khugepaged_scan.mm_slot = list_entry(
1761 mm_slot->mm_node.next,
1762 struct mm_slot, mm_node);
1763 khugepaged_scan.address = 0;
1765 khugepaged_scan.mm_slot = NULL;
1766 khugepaged_full_scans++;
1769 collect_mm_slot(mm_slot);
1775 static int khugepaged_has_work(void)
1777 return !list_empty(&khugepaged_scan.mm_head) &&
1778 khugepaged_enabled();
1781 static int khugepaged_wait_event(void)
1783 return !list_empty(&khugepaged_scan.mm_head) ||
1784 kthread_should_stop();
1787 static void khugepaged_do_scan(void)
1789 struct page *hpage = NULL;
1790 unsigned int progress = 0, pass_through_head = 0;
1791 unsigned int pages = khugepaged_pages_to_scan;
1794 barrier(); /* write khugepaged_pages_to_scan to local stack */
1796 while (progress < pages) {
1797 if (!khugepaged_prealloc_page(&hpage, &wait))
1802 if (unlikely(kthread_should_stop() || try_to_freeze()))
1805 spin_lock(&khugepaged_mm_lock);
1806 if (!khugepaged_scan.mm_slot)
1807 pass_through_head++;
1808 if (khugepaged_has_work() &&
1809 pass_through_head < 2)
1810 progress += khugepaged_scan_mm_slot(pages - progress,
1814 spin_unlock(&khugepaged_mm_lock);
1817 if (!IS_ERR_OR_NULL(hpage))
1821 static bool khugepaged_should_wakeup(void)
1823 return kthread_should_stop() ||
1824 time_after_eq(jiffies, khugepaged_sleep_expire);
1827 static void khugepaged_wait_work(void)
1829 if (khugepaged_has_work()) {
1830 const unsigned long scan_sleep_jiffies =
1831 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
1833 if (!scan_sleep_jiffies)
1836 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
1837 wait_event_freezable_timeout(khugepaged_wait,
1838 khugepaged_should_wakeup(),
1839 scan_sleep_jiffies);
1843 if (khugepaged_enabled())
1844 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
1847 static int khugepaged(void *none)
1849 struct mm_slot *mm_slot;
1852 set_user_nice(current, MAX_NICE);
1854 while (!kthread_should_stop()) {
1855 khugepaged_do_scan();
1856 khugepaged_wait_work();
1859 spin_lock(&khugepaged_mm_lock);
1860 mm_slot = khugepaged_scan.mm_slot;
1861 khugepaged_scan.mm_slot = NULL;
1863 collect_mm_slot(mm_slot);
1864 spin_unlock(&khugepaged_mm_lock);
1868 static void set_recommended_min_free_kbytes(void)
1872 unsigned long recommended_min;
1874 for_each_populated_zone(zone)
1877 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1878 recommended_min = pageblock_nr_pages * nr_zones * 2;
1881 * Make sure that on average at least two pageblocks are almost free
1882 * of another type, one for a migratetype to fall back to and a
1883 * second to avoid subsequent fallbacks of other types There are 3
1884 * MIGRATE_TYPES we care about.
1886 recommended_min += pageblock_nr_pages * nr_zones *
1887 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
1889 /* don't ever allow to reserve more than 5% of the lowmem */
1890 recommended_min = min(recommended_min,
1891 (unsigned long) nr_free_buffer_pages() / 20);
1892 recommended_min <<= (PAGE_SHIFT-10);
1894 if (recommended_min > min_free_kbytes) {
1895 if (user_min_free_kbytes >= 0)
1896 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1897 min_free_kbytes, recommended_min);
1899 min_free_kbytes = recommended_min;
1901 setup_per_zone_wmarks();
1904 int start_stop_khugepaged(void)
1906 static struct task_struct *khugepaged_thread __read_mostly;
1907 static DEFINE_MUTEX(khugepaged_mutex);
1910 mutex_lock(&khugepaged_mutex);
1911 if (khugepaged_enabled()) {
1912 if (!khugepaged_thread)
1913 khugepaged_thread = kthread_run(khugepaged, NULL,
1915 if (IS_ERR(khugepaged_thread)) {
1916 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1917 err = PTR_ERR(khugepaged_thread);
1918 khugepaged_thread = NULL;
1922 if (!list_empty(&khugepaged_scan.mm_head))
1923 wake_up_interruptible(&khugepaged_wait);
1925 set_recommended_min_free_kbytes();
1926 } else if (khugepaged_thread) {
1927 kthread_stop(khugepaged_thread);
1928 khugepaged_thread = NULL;
1931 mutex_unlock(&khugepaged_mutex);