1// SPDX-License-Identifier: GPL-2.0
2#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3
4#include <linux/mm.h>
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>
21
22#include <asm/tlb.h>
23#include <asm/pgalloc.h>
24#include "internal.h"
25
26enum scan_result {
27 SCAN_FAIL,
28 SCAN_SUCCEED,
29 SCAN_PMD_NULL,
30 SCAN_EXCEED_NONE_PTE,
31 SCAN_PTE_NON_PRESENT,
32 SCAN_PAGE_RO,
33 SCAN_LACK_REFERENCED_PAGE,
34 SCAN_PAGE_NULL,
35 SCAN_SCAN_ABORT,
36 SCAN_PAGE_COUNT,
37 SCAN_PAGE_LRU,
38 SCAN_PAGE_LOCK,
39 SCAN_PAGE_ANON,
40 SCAN_PAGE_COMPOUND,
41 SCAN_ANY_PROCESS,
42 SCAN_VMA_NULL,
43 SCAN_VMA_CHECK,
44 SCAN_ADDRESS_RANGE,
45 SCAN_SWAP_CACHE_PAGE,
46 SCAN_DEL_PAGE_LRU,
47 SCAN_ALLOC_HUGE_PAGE_FAIL,
48 SCAN_CGROUP_CHARGE_FAIL,
49 SCAN_EXCEED_SWAP_PTE,
50 SCAN_TRUNCATED,
51};
52
53#define CREATE_TRACE_POINTS
54#include <trace/events/huge_memory.h>
55
56/* default scan 8*512 pte (or vmas) every 30 second */
57static unsigned int khugepaged_pages_to_scan __read_mostly;
58static unsigned int khugepaged_pages_collapsed;
59static unsigned int khugepaged_full_scans;
60static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
61/* during fragmentation poll the hugepage allocator once every minute */
62static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
63static unsigned long khugepaged_sleep_expire;
64static DEFINE_SPINLOCK(khugepaged_mm_lock);
65static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
66/*
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
69 * fault.
70 */
71static unsigned int khugepaged_max_ptes_none __read_mostly;
72static unsigned int khugepaged_max_ptes_swap __read_mostly;
73
74#define MM_SLOTS_HASH_BITS 10
75static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
76
77static struct kmem_cache *mm_slot_cache __read_mostly;
78
79/**
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
84 */
85struct mm_slot {
86 struct hlist_node hash;
87 struct list_head mm_node;
88 struct mm_struct *mm;
89};
90
91/**
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
96 *
97 * There is only the one khugepaged_scan instance of this cursor structure.
98 */
99struct khugepaged_scan {
100 struct list_head mm_head;
101 struct mm_slot *mm_slot;
102 unsigned long address;
103};
104
105static struct khugepaged_scan khugepaged_scan = {
106 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
107};
108
109#ifdef CONFIG_SYSFS
110static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
111 struct kobj_attribute *attr,
112 char *buf)
113{
114 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
115}
116
117static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
118 struct kobj_attribute *attr,
119 const char *buf, size_t count)
120{
121 unsigned long msecs;
122 int err;
123
124 err = kstrtoul(buf, 10, &msecs);
125 if (err || msecs > UINT_MAX)
126 return -EINVAL;
127
128 khugepaged_scan_sleep_millisecs = msecs;
129 khugepaged_sleep_expire = 0;
130 wake_up_interruptible(&khugepaged_wait);
131
132 return count;
133}
134static struct kobj_attribute scan_sleep_millisecs_attr =
135 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
136 scan_sleep_millisecs_store);
137
138static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
139 struct kobj_attribute *attr,
140 char *buf)
141{
142 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
143}
144
145static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
146 struct kobj_attribute *attr,
147 const char *buf, size_t count)
148{
149 unsigned long msecs;
150 int err;
151
152 err = kstrtoul(buf, 10, &msecs);
153 if (err || msecs > UINT_MAX)
154 return -EINVAL;
155
156 khugepaged_alloc_sleep_millisecs = msecs;
157 khugepaged_sleep_expire = 0;
158 wake_up_interruptible(&khugepaged_wait);
159
160 return count;
161}
162static struct kobj_attribute alloc_sleep_millisecs_attr =
163 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
164 alloc_sleep_millisecs_store);
165
166static ssize_t pages_to_scan_show(struct kobject *kobj,
167 struct kobj_attribute *attr,
168 char *buf)
169{
170 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
171}
172static ssize_t pages_to_scan_store(struct kobject *kobj,
173 struct kobj_attribute *attr,
174 const char *buf, size_t count)
175{
176 int err;
177 unsigned long pages;
178
179 err = kstrtoul(buf, 10, &pages);
180 if (err || !pages || pages > UINT_MAX)
181 return -EINVAL;
182
183 khugepaged_pages_to_scan = pages;
184
185 return count;
186}
187static struct kobj_attribute pages_to_scan_attr =
188 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
189 pages_to_scan_store);
190
191static ssize_t pages_collapsed_show(struct kobject *kobj,
192 struct kobj_attribute *attr,
193 char *buf)
194{
195 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
196}
197static struct kobj_attribute pages_collapsed_attr =
198 __ATTR_RO(pages_collapsed);
199
200static ssize_t full_scans_show(struct kobject *kobj,
201 struct kobj_attribute *attr,
202 char *buf)
203{
204 return sprintf(buf, "%u\n", khugepaged_full_scans);
205}
206static struct kobj_attribute full_scans_attr =
207 __ATTR_RO(full_scans);
208
209static ssize_t khugepaged_defrag_show(struct kobject *kobj,
210 struct kobj_attribute *attr, char *buf)
211{
212 return single_hugepage_flag_show(kobj, attr, buf,
213 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
214}
215static ssize_t khugepaged_defrag_store(struct kobject *kobj,
216 struct kobj_attribute *attr,
217 const char *buf, size_t count)
218{
219 return single_hugepage_flag_store(kobj, attr, buf, count,
220 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
221}
222static struct kobj_attribute khugepaged_defrag_attr =
223 __ATTR(defrag, 0644, khugepaged_defrag_show,
224 khugepaged_defrag_store);
225
226/*
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.
233 */
234static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
235 struct kobj_attribute *attr,
236 char *buf)
237{
238 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
239}
240static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
241 struct kobj_attribute *attr,
242 const char *buf, size_t count)
243{
244 int err;
245 unsigned long max_ptes_none;
246
247 err = kstrtoul(buf, 10, &max_ptes_none);
248 if (err || max_ptes_none > HPAGE_PMD_NR-1)
249 return -EINVAL;
250
251 khugepaged_max_ptes_none = max_ptes_none;
252
253 return count;
254}
255static 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);
258
259static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
260 struct kobj_attribute *attr,
261 char *buf)
262{
263 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
264}
265
266static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
267 struct kobj_attribute *attr,
268 const char *buf, size_t count)
269{
270 int err;
271 unsigned long max_ptes_swap;
272
273 err = kstrtoul(buf, 10, &max_ptes_swap);
274 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
275 return -EINVAL;
276
277 khugepaged_max_ptes_swap = max_ptes_swap;
278
279 return count;
280}
281
282static 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);
285
286static 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,
295 NULL,
296};
297
298struct attribute_group khugepaged_attr_group = {
299 .attrs = khugepaged_attr,
300 .name = "khugepaged",
301};
302#endif /* CONFIG_SYSFS */
303
304#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
305
306int hugepage_madvise(struct vm_area_struct *vma,
307 unsigned long *vm_flags, int advice)
308{
309 switch (advice) {
310 case MADV_HUGEPAGE:
311#ifdef CONFIG_S390
312 /*
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.
316 */
317 if (mm_has_pgste(vma->vm_mm))
318 return 0;
319#endif
320 *vm_flags &= ~VM_NOHUGEPAGE;
321 *vm_flags |= VM_HUGEPAGE;
322 /*
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.
326 */
327 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
328 khugepaged_enter_vma_merge(vma, *vm_flags))
329 return -ENOMEM;
330 break;
331 case MADV_NOHUGEPAGE:
332 *vm_flags &= ~VM_HUGEPAGE;
333 *vm_flags |= VM_NOHUGEPAGE;
334 /*
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.
338 */
339 break;
340 }
341
342 return 0;
343}
344
345int __init khugepaged_init(void)
346{
347 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
348 sizeof(struct mm_slot),
349 __alignof__(struct mm_slot), 0, NULL);
350 if (!mm_slot_cache)
351 return -ENOMEM;
352
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;
356
357 return 0;
358}
359
360void __init khugepaged_destroy(void)
361{
362 kmem_cache_destroy(mm_slot_cache);
363}
364
365static inline struct mm_slot *alloc_mm_slot(void)
366{
367 if (!mm_slot_cache) /* initialization failed */
368 return NULL;
369 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
370}
371
372static inline void free_mm_slot(struct mm_slot *mm_slot)
373{
374 kmem_cache_free(mm_slot_cache, mm_slot);
375}
376
377static struct mm_slot *get_mm_slot(struct mm_struct *mm)
378{
379 struct mm_slot *mm_slot;
380
381 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
382 if (mm == mm_slot->mm)
383 return mm_slot;
384
385 return NULL;
386}
387
388static void insert_to_mm_slots_hash(struct mm_struct *mm,
389 struct mm_slot *mm_slot)
390{
391 mm_slot->mm = mm;
392 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
393}
394
395static inline int khugepaged_test_exit(struct mm_struct *mm)
396{
397 return atomic_read(&mm->mm_users) == 0;
398}
399
400static bool hugepage_vma_check(struct vm_area_struct *vma,
401 unsigned long vm_flags)
402{
403 if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
404 (vm_flags & VM_NOHUGEPAGE) ||
405 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
406 return false;
407 if (shmem_file(vma->vm_file)) {
408 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
409 return false;
410 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
411 HPAGE_PMD_NR);
412 }
413 if (!vma->anon_vma || vma->vm_ops)
414 return false;
415 if (is_vma_temporary_stack(vma))
416 return false;
417 return !(vm_flags & VM_NO_KHUGEPAGED);
418}
419
420int __khugepaged_enter(struct mm_struct *mm)
421{
422 struct mm_slot *mm_slot;
423 int wakeup;
424
425 mm_slot = alloc_mm_slot();
426 if (!mm_slot)
427 return -ENOMEM;
428
429 /* __khugepaged_exit() must not run from under us */
430 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
431 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
432 free_mm_slot(mm_slot);
433 return 0;
434 }
435
436 spin_lock(&khugepaged_mm_lock);
437 insert_to_mm_slots_hash(mm, mm_slot);
438 /*
439 * Insert just behind the scanning cursor, to let the area settle
440 * down a little.
441 */
442 wakeup = list_empty(&khugepaged_scan.mm_head);
443 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
444 spin_unlock(&khugepaged_mm_lock);
445
446 mmgrab(mm);
447 if (wakeup)
448 wake_up_interruptible(&khugepaged_wait);
449
450 return 0;
451}
452
453int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
454 unsigned long vm_flags)
455{
456 unsigned long hstart, hend;
457
458 /*
459 * khugepaged does not yet work on non-shmem files or special
460 * mappings. And file-private shmem THP is not supported.
461 */
462 if (!hugepage_vma_check(vma, vm_flags))
463 return 0;
464
465 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
466 hend = vma->vm_end & HPAGE_PMD_MASK;
467 if (hstart < hend)
468 return khugepaged_enter(vma, vm_flags);
469 return 0;
470}
471
472void __khugepaged_exit(struct mm_struct *mm)
473{
474 struct mm_slot *mm_slot;
475 int free = 0;
476
477 spin_lock(&khugepaged_mm_lock);
478 mm_slot = get_mm_slot(mm);
479 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
480 hash_del(&mm_slot->hash);
481 list_del(&mm_slot->mm_node);
482 free = 1;
483 }
484 spin_unlock(&khugepaged_mm_lock);
485
486 if (free) {
487 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
488 free_mm_slot(mm_slot);
489 mmdrop(mm);
490 } else if (mm_slot) {
491 /*
492 * This is required to serialize against
493 * khugepaged_test_exit() (which is guaranteed to run
494 * under mmap sem read mode). Stop here (after we
495 * return all pagetables will be destroyed) until
496 * khugepaged has finished working on the pagetables
497 * under the mmap_sem.
498 */
499 down_write(&mm->mmap_sem);
500 up_write(&mm->mmap_sem);
501 }
502}
503
504static void release_pte_page(struct page *page)
505{
506 dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
507 unlock_page(page);
508 putback_lru_page(page);
509}
510
511static void release_pte_pages(pte_t *pte, pte_t *_pte)
512{
513 while (--_pte >= pte) {
514 pte_t pteval = *_pte;
515 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
516 release_pte_page(pte_page(pteval));
517 }
518}
519
520static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
521 unsigned long address,
522 pte_t *pte)
523{
524 struct page *page = NULL;
525 pte_t *_pte;
526 int none_or_zero = 0, result = 0, referenced = 0;
527 bool writable = false;
528
529 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
530 _pte++, address += PAGE_SIZE) {
531 pte_t pteval = *_pte;
532 if (pte_none(pteval) || (pte_present(pteval) &&
533 is_zero_pfn(pte_pfn(pteval)))) {
534 if (!userfaultfd_armed(vma) &&
535 ++none_or_zero <= khugepaged_max_ptes_none) {
536 continue;
537 } else {
538 result = SCAN_EXCEED_NONE_PTE;
539 goto out;
540 }
541 }
542 if (!pte_present(pteval)) {
543 result = SCAN_PTE_NON_PRESENT;
544 goto out;
545 }
546 page = vm_normal_page(vma, address, pteval);
547 if (unlikely(!page)) {
548 result = SCAN_PAGE_NULL;
549 goto out;
550 }
551
552 /* TODO: teach khugepaged to collapse THP mapped with pte */
553 if (PageCompound(page)) {
554 result = SCAN_PAGE_COMPOUND;
555 goto out;
556 }
557
558 VM_BUG_ON_PAGE(!PageAnon(page), page);
559
560 /*
561 * We can do it before isolate_lru_page because the
562 * page can't be freed from under us. NOTE: PG_lock
563 * is needed to serialize against split_huge_page
564 * when invoked from the VM.
565 */
566 if (!trylock_page(page)) {
567 result = SCAN_PAGE_LOCK;
568 goto out;
569 }
570
571 /*
572 * cannot use mapcount: can't collapse if there's a gup pin.
573 * The page must only be referenced by the scanned process
574 * and page swap cache.
575 */
576 if (page_count(page) != 1 + PageSwapCache(page)) {
577 unlock_page(page);
578 result = SCAN_PAGE_COUNT;
579 goto out;
580 }
581 if (pte_write(pteval)) {
582 writable = true;
583 } else {
584 if (PageSwapCache(page) &&
585 !reuse_swap_page(page, NULL)) {
586 unlock_page(page);
587 result = SCAN_SWAP_CACHE_PAGE;
588 goto out;
589 }
590 /*
591 * Page is not in the swap cache. It can be collapsed
592 * into a THP.
593 */
594 }
595
596 /*
597 * Isolate the page to avoid collapsing an hugepage
598 * currently in use by the VM.
599 */
600 if (isolate_lru_page(page)) {
601 unlock_page(page);
602 result = SCAN_DEL_PAGE_LRU;
603 goto out;
604 }
605 inc_node_page_state(page,
606 NR_ISOLATED_ANON + page_is_file_cache(page));
607 VM_BUG_ON_PAGE(!PageLocked(page), page);
608 VM_BUG_ON_PAGE(PageLRU(page), page);
609
610 /* There should be enough young pte to collapse the page */
611 if (pte_young(pteval) ||
612 page_is_young(page) || PageReferenced(page) ||
613 mmu_notifier_test_young(vma->vm_mm, address))
614 referenced++;
615 }
616 if (likely(writable)) {
617 if (likely(referenced)) {
618 result = SCAN_SUCCEED;
619 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
620 referenced, writable, result);
621 return 1;
622 }
623 } else {
624 result = SCAN_PAGE_RO;
625 }
626
627out:
628 release_pte_pages(pte, _pte);
629 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
630 referenced, writable, result);
631 return 0;
632}
633
634static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
635 struct vm_area_struct *vma,
636 unsigned long address,
637 spinlock_t *ptl)
638{
639 pte_t *_pte;
640 for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
641 _pte++, page++, address += PAGE_SIZE) {
642 pte_t pteval = *_pte;
643 struct page *src_page;
644
645 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
646 clear_user_highpage(page, address);
647 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
648 if (is_zero_pfn(pte_pfn(pteval))) {
649 /*
650 * ptl mostly unnecessary.
651 */
652 spin_lock(ptl);
653 /*
654 * paravirt calls inside pte_clear here are
655 * superfluous.
656 */
657 pte_clear(vma->vm_mm, address, _pte);
658 spin_unlock(ptl);
659 }
660 } else {
661 src_page = pte_page(pteval);
662 copy_user_highpage(page, src_page, address, vma);
663 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
664 release_pte_page(src_page);
665 /*
666 * ptl mostly unnecessary, but preempt has to
667 * be disabled to update the per-cpu stats
668 * inside page_remove_rmap().
669 */
670 spin_lock(ptl);
671 /*
672 * paravirt calls inside pte_clear here are
673 * superfluous.
674 */
675 pte_clear(vma->vm_mm, address, _pte);
676 page_remove_rmap(src_page, false);
677 spin_unlock(ptl);
678 free_page_and_swap_cache(src_page);
679 }
680 }
681}
682
683static void khugepaged_alloc_sleep(void)
684{
685 DEFINE_WAIT(wait);
686
687 add_wait_queue(&khugepaged_wait, &wait);
688 freezable_schedule_timeout_interruptible(
689 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
690 remove_wait_queue(&khugepaged_wait, &wait);
691}
692
693static int khugepaged_node_load[MAX_NUMNODES];
694
695static bool khugepaged_scan_abort(int nid)
696{
697 int i;
698
699 /*
700 * If node_reclaim_mode is disabled, then no extra effort is made to
701 * allocate memory locally.
702 */
703 if (!node_reclaim_mode)
704 return false;
705
706 /* If there is a count for this node already, it must be acceptable */
707 if (khugepaged_node_load[nid])
708 return false;
709
710 for (i = 0; i < MAX_NUMNODES; i++) {
711 if (!khugepaged_node_load[i])
712 continue;
713 if (node_distance(nid, i) > RECLAIM_DISTANCE)
714 return true;
715 }
716 return false;
717}
718
719/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
720static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
721{
722 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
723}
724
725#ifdef CONFIG_NUMA
726static int khugepaged_find_target_node(void)
727{
728 static int last_khugepaged_target_node = NUMA_NO_NODE;
729 int nid, target_node = 0, max_value = 0;
730
731 /* find first node with max normal pages hit */
732 for (nid = 0; nid < MAX_NUMNODES; nid++)
733 if (khugepaged_node_load[nid] > max_value) {
734 max_value = khugepaged_node_load[nid];
735 target_node = nid;
736 }
737
738 /* do some balance if several nodes have the same hit record */
739 if (target_node <= last_khugepaged_target_node)
740 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
741 nid++)
742 if (max_value == khugepaged_node_load[nid]) {
743 target_node = nid;
744 break;
745 }
746
747 last_khugepaged_target_node = target_node;
748 return target_node;
749}
750
751static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
752{
753 if (IS_ERR(*hpage)) {
754 if (!*wait)
755 return false;
756
757 *wait = false;
758 *hpage = NULL;
759 khugepaged_alloc_sleep();
760 } else if (*hpage) {
761 put_page(*hpage);
762 *hpage = NULL;
763 }
764
765 return true;
766}
767
768static struct page *
769khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
770{
771 VM_BUG_ON_PAGE(*hpage, *hpage);
772
773 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
774 if (unlikely(!*hpage)) {
775 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
776 *hpage = ERR_PTR(-ENOMEM);
777 return NULL;
778 }
779
780 prep_transhuge_page(*hpage);
781 count_vm_event(THP_COLLAPSE_ALLOC);
782 return *hpage;
783}
784#else
785static int khugepaged_find_target_node(void)
786{
787 return 0;
788}
789
790static inline struct page *alloc_khugepaged_hugepage(void)
791{
792 struct page *page;
793
794 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
795 HPAGE_PMD_ORDER);
796 if (page)
797 prep_transhuge_page(page);
798 return page;
799}
800
801static struct page *khugepaged_alloc_hugepage(bool *wait)
802{
803 struct page *hpage;
804
805 do {
806 hpage = alloc_khugepaged_hugepage();
807 if (!hpage) {
808 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
809 if (!*wait)
810 return NULL;
811
812 *wait = false;
813 khugepaged_alloc_sleep();
814 } else
815 count_vm_event(THP_COLLAPSE_ALLOC);
816 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
817
818 return hpage;
819}
820
821static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
822{
823 if (!*hpage)
824 *hpage = khugepaged_alloc_hugepage(wait);
825
826 if (unlikely(!*hpage))
827 return false;
828
829 return true;
830}
831
832static struct page *
833khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
834{
835 VM_BUG_ON(!*hpage);
836
837 return *hpage;
838}
839#endif
840
841/*
842 * If mmap_sem temporarily dropped, revalidate vma
843 * before taking mmap_sem.
844 * Return 0 if succeeds, otherwise return none-zero
845 * value (scan code).
846 */
847
848static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
849 struct vm_area_struct **vmap)
850{
851 struct vm_area_struct *vma;
852 unsigned long hstart, hend;
853
854 if (unlikely(khugepaged_test_exit(mm)))
855 return SCAN_ANY_PROCESS;
856
857 *vmap = vma = find_vma(mm, address);
858 if (!vma)
859 return SCAN_VMA_NULL;
860
861 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
862 hend = vma->vm_end & HPAGE_PMD_MASK;
863 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
864 return SCAN_ADDRESS_RANGE;
865 if (!hugepage_vma_check(vma, vma->vm_flags))
866 return SCAN_VMA_CHECK;
867 return 0;
868}
869
870/*
871 * Bring missing pages in from swap, to complete THP collapse.
872 * Only done if khugepaged_scan_pmd believes it is worthwhile.
873 *
874 * Called and returns without pte mapped or spinlocks held,
875 * but with mmap_sem held to protect against vma changes.
876 */
877
878static bool __collapse_huge_page_swapin(struct mm_struct *mm,
879 struct vm_area_struct *vma,
880 unsigned long address, pmd_t *pmd,
881 int referenced)
882{
883 int swapped_in = 0;
884 vm_fault_t ret = 0;
885 struct vm_fault vmf = {
886 .vma = vma,
887 .address = address,
888 .flags = FAULT_FLAG_ALLOW_RETRY,
889 .pmd = pmd,
890 .pgoff = linear_page_index(vma, address),
891 };
892
893 /* we only decide to swapin, if there is enough young ptes */
894 if (referenced < HPAGE_PMD_NR/2) {
895 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
896 return false;
897 }
898 vmf.pte = pte_offset_map(pmd, address);
899 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
900 vmf.pte++, vmf.address += PAGE_SIZE) {
901 vmf.orig_pte = *vmf.pte;
902 if (!is_swap_pte(vmf.orig_pte))
903 continue;
904 swapped_in++;
905 ret = do_swap_page(&vmf);
906
907 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
908 if (ret & VM_FAULT_RETRY) {
909 down_read(&mm->mmap_sem);
910 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {
911 /* vma is no longer available, don't continue to swapin */
912 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
913 return false;
914 }
915 /* check if the pmd is still valid */
916 if (mm_find_pmd(mm, address) != pmd) {
917 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
918 return false;
919 }
920 }
921 if (ret & VM_FAULT_ERROR) {
922 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
923 return false;
924 }
925 /* pte is unmapped now, we need to map it */
926 vmf.pte = pte_offset_map(pmd, vmf.address);
927 }
928 vmf.pte--;
929 pte_unmap(vmf.pte);
930 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
931 return true;
932}
933
934static void collapse_huge_page(struct mm_struct *mm,
935 unsigned long address,
936 struct page **hpage,
937 int node, int referenced)
938{
939 pmd_t *pmd, _pmd;
940 pte_t *pte;
941 pgtable_t pgtable;
942 struct page *new_page;
943 spinlock_t *pmd_ptl, *pte_ptl;
944 int isolated = 0, result = 0;
945 struct mem_cgroup *memcg;
946 struct vm_area_struct *vma;
947 struct mmu_notifier_range range;
948 gfp_t gfp;
949
950 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
951
952 /* Only allocate from the target node */
953 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
954
955 /*
956 * Before allocating the hugepage, release the mmap_sem read lock.
957 * The allocation can take potentially a long time if it involves
958 * sync compaction, and we do not need to hold the mmap_sem during
959 * that. We will recheck the vma after taking it again in write mode.
960 */
961 up_read(&mm->mmap_sem);
962 new_page = khugepaged_alloc_page(hpage, gfp, node);
963 if (!new_page) {
964 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
965 goto out_nolock;
966 }
967
968 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
969 result = SCAN_CGROUP_CHARGE_FAIL;
970 goto out_nolock;
971 }
972
973 down_read(&mm->mmap_sem);
974 result = hugepage_vma_revalidate(mm, address, &vma);
975 if (result) {
976 mem_cgroup_cancel_charge(new_page, memcg, true);
977 up_read(&mm->mmap_sem);
978 goto out_nolock;
979 }
980
981 pmd = mm_find_pmd(mm, address);
982 if (!pmd) {
983 result = SCAN_PMD_NULL;
984 mem_cgroup_cancel_charge(new_page, memcg, true);
985 up_read(&mm->mmap_sem);
986 goto out_nolock;
987 }
988
989 /*
990 * __collapse_huge_page_swapin always returns with mmap_sem locked.
991 * If it fails, we release mmap_sem and jump out_nolock.
992 * Continuing to collapse causes inconsistency.
993 */
994 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
995 mem_cgroup_cancel_charge(new_page, memcg, true);
996 up_read(&mm->mmap_sem);
997 goto out_nolock;
998 }
999
1000 up_read(&mm->mmap_sem);
1001 /*
1002 * Prevent all access to pagetables with the exception of
1003 * gup_fast later handled by the ptep_clear_flush and the VM
1004 * handled by the anon_vma lock + PG_lock.
1005 */
1006 down_write(&mm->mmap_sem);
1007 result = hugepage_vma_revalidate(mm, address, &vma);
1008 if (result)
1009 goto out;
1010 /* check if the pmd is still valid */
1011 if (mm_find_pmd(mm, address) != pmd)
1012 goto out;
1013
1014 anon_vma_lock_write(vma->anon_vma);
1015
1016 pte = pte_offset_map(pmd, address);
1017 pte_ptl = pte_lockptr(mm, pmd);
1018
1019 mmu_notifier_range_init(&range, mm, address, address + HPAGE_PMD_SIZE);
1020 mmu_notifier_invalidate_range_start(&range);
1021 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1022 /*
1023 * After this gup_fast can't run anymore. This also removes
1024 * any huge TLB entry from the CPU so we won't allow
1025 * huge and small TLB entries for the same virtual address
1026 * to avoid the risk of CPU bugs in that area.
1027 */
1028 _pmd = pmdp_collapse_flush(vma, address, pmd);
1029 spin_unlock(pmd_ptl);
1030 mmu_notifier_invalidate_range_end(&range);
1031
1032 spin_lock(pte_ptl);
1033 isolated = __collapse_huge_page_isolate(vma, address, pte);
1034 spin_unlock(pte_ptl);
1035
1036 if (unlikely(!isolated)) {
1037 pte_unmap(pte);
1038 spin_lock(pmd_ptl);
1039 BUG_ON(!pmd_none(*pmd));
1040 /*
1041 * We can only use set_pmd_at when establishing
1042 * hugepmds and never for establishing regular pmds that
1043 * points to regular pagetables. Use pmd_populate for that
1044 */
1045 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1046 spin_unlock(pmd_ptl);
1047 anon_vma_unlock_write(vma->anon_vma);
1048 result = SCAN_FAIL;
1049 goto out;
1050 }
1051
1052 /*
1053 * All pages are isolated and locked so anon_vma rmap
1054 * can't run anymore.
1055 */
1056 anon_vma_unlock_write(vma->anon_vma);
1057
1058 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
1059 pte_unmap(pte);
1060 __SetPageUptodate(new_page);
1061 pgtable = pmd_pgtable(_pmd);
1062
1063 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1064 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1065
1066 /*
1067 * spin_lock() below is not the equivalent of smp_wmb(), so
1068 * this is needed to avoid the copy_huge_page writes to become
1069 * visible after the set_pmd_at() write.
1070 */
1071 smp_wmb();
1072
1073 spin_lock(pmd_ptl);
1074 BUG_ON(!pmd_none(*pmd));
1075 page_add_new_anon_rmap(new_page, vma, address, true);
1076 mem_cgroup_commit_charge(new_page, memcg, false, true);
1077 count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1);
1078 lru_cache_add_active_or_unevictable(new_page, vma);
1079 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1080 set_pmd_at(mm, address, pmd, _pmd);
1081 update_mmu_cache_pmd(vma, address, pmd);
1082 spin_unlock(pmd_ptl);
1083
1084 *hpage = NULL;
1085
1086 khugepaged_pages_collapsed++;
1087 result = SCAN_SUCCEED;
1088out_up_write:
1089 up_write(&mm->mmap_sem);
1090out_nolock:
1091 trace_mm_collapse_huge_page(mm, isolated, result);
1092 return;
1093out:
1094 mem_cgroup_cancel_charge(new_page, memcg, true);
1095 goto out_up_write;
1096}
1097
1098static int khugepaged_scan_pmd(struct mm_struct *mm,
1099 struct vm_area_struct *vma,
1100 unsigned long address,
1101 struct page **hpage)
1102{
1103 pmd_t *pmd;
1104 pte_t *pte, *_pte;
1105 int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
1106 struct page *page = NULL;
1107 unsigned long _address;
1108 spinlock_t *ptl;
1109 int node = NUMA_NO_NODE, unmapped = 0;
1110 bool writable = false;
1111
1112 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1113
1114 pmd = mm_find_pmd(mm, address);
1115 if (!pmd) {
1116 result = SCAN_PMD_NULL;
1117 goto out;
1118 }
1119
1120 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1121 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1122 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1123 _pte++, _address += PAGE_SIZE) {
1124 pte_t pteval = *_pte;
1125 if (is_swap_pte(pteval)) {
1126 if (++unmapped <= khugepaged_max_ptes_swap) {
1127 continue;
1128 } else {
1129 result = SCAN_EXCEED_SWAP_PTE;
1130 goto out_unmap;
1131 }
1132 }
1133 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1134 if (!userfaultfd_armed(vma) &&
1135 ++none_or_zero <= khugepaged_max_ptes_none) {
1136 continue;
1137 } else {
1138 result = SCAN_EXCEED_NONE_PTE;
1139 goto out_unmap;
1140 }
1141 }
1142 if (!pte_present(pteval)) {
1143 result = SCAN_PTE_NON_PRESENT;
1144 goto out_unmap;
1145 }
1146 if (pte_write(pteval))
1147 writable = true;
1148
1149 page = vm_normal_page(vma, _address, pteval);
1150 if (unlikely(!page)) {
1151 result = SCAN_PAGE_NULL;
1152 goto out_unmap;
1153 }
1154
1155 /* TODO: teach khugepaged to collapse THP mapped with pte */
1156 if (PageCompound(page)) {
1157 result = SCAN_PAGE_COMPOUND;
1158 goto out_unmap;
1159 }
1160
1161 /*
1162 * Record which node the original page is from and save this
1163 * information to khugepaged_node_load[].
1164 * Khupaged will allocate hugepage from the node has the max
1165 * hit record.
1166 */
1167 node = page_to_nid(page);
1168 if (khugepaged_scan_abort(node)) {
1169 result = SCAN_SCAN_ABORT;
1170 goto out_unmap;
1171 }
1172 khugepaged_node_load[node]++;
1173 if (!PageLRU(page)) {
1174 result = SCAN_PAGE_LRU;
1175 goto out_unmap;
1176 }
1177 if (PageLocked(page)) {
1178 result = SCAN_PAGE_LOCK;
1179 goto out_unmap;
1180 }
1181 if (!PageAnon(page)) {
1182 result = SCAN_PAGE_ANON;
1183 goto out_unmap;
1184 }
1185
1186 /*
1187 * cannot use mapcount: can't collapse if there's a gup pin.
1188 * The page must only be referenced by the scanned process
1189 * and page swap cache.
1190 */
1191 if (page_count(page) != 1 + PageSwapCache(page)) {
1192 result = SCAN_PAGE_COUNT;
1193 goto out_unmap;
1194 }
1195 if (pte_young(pteval) ||
1196 page_is_young(page) || PageReferenced(page) ||
1197 mmu_notifier_test_young(vma->vm_mm, address))
1198 referenced++;
1199 }
1200 if (writable) {
1201 if (referenced) {
1202 result = SCAN_SUCCEED;
1203 ret = 1;
1204 } else {
1205 result = SCAN_LACK_REFERENCED_PAGE;
1206 }
1207 } else {
1208 result = SCAN_PAGE_RO;
1209 }
1210out_unmap:
1211 pte_unmap_unlock(pte, ptl);
1212 if (ret) {
1213 node = khugepaged_find_target_node();
1214 /* collapse_huge_page will return with the mmap_sem released */
1215 collapse_huge_page(mm, address, hpage, node, referenced);
1216 }
1217out:
1218 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1219 none_or_zero, result, unmapped);
1220 return ret;
1221}
1222
1223static void collect_mm_slot(struct mm_slot *mm_slot)
1224{
1225 struct mm_struct *mm = mm_slot->mm;
1226
1227 lockdep_assert_held(&khugepaged_mm_lock);
1228
1229 if (khugepaged_test_exit(mm)) {
1230 /* free mm_slot */
1231 hash_del(&mm_slot->hash);
1232 list_del(&mm_slot->mm_node);
1233
1234 /*
1235 * Not strictly needed because the mm exited already.
1236 *
1237 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1238 */
1239
1240 /* khugepaged_mm_lock actually not necessary for the below */
1241 free_mm_slot(mm_slot);
1242 mmdrop(mm);
1243 }
1244}
1245
1246#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
1247static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1248{
1249 struct vm_area_struct *vma;
1250 unsigned long addr;
1251 pmd_t *pmd, _pmd;
1252
1253 i_mmap_lock_write(mapping);
1254 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1255 /* probably overkill */
1256 if (vma->anon_vma)
1257 continue;
1258 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1259 if (addr & ~HPAGE_PMD_MASK)
1260 continue;
1261 if (vma->vm_end < addr + HPAGE_PMD_SIZE)
1262 continue;
1263 pmd = mm_find_pmd(vma->vm_mm, addr);
1264 if (!pmd)
1265 continue;
1266 /*
1267 * We need exclusive mmap_sem to retract page table.
1268 * If trylock fails we would end up with pte-mapped THP after
1269 * re-fault. Not ideal, but it's more important to not disturb
1270 * the system too much.
1271 */
1272 if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
1273 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
1274 /* assume page table is clear */
1275 _pmd = pmdp_collapse_flush(vma, addr, pmd);
1276 spin_unlock(ptl);
1277 up_write(&vma->vm_mm->mmap_sem);
1278 mm_dec_nr_ptes(vma->vm_mm);
1279 pte_free(vma->vm_mm, pmd_pgtable(_pmd));
1280 }
1281 }
1282 i_mmap_unlock_write(mapping);
1283}
1284
1285/**
1286 * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
1287 *
1288 * Basic scheme is simple, details are more complex:
1289 * - allocate and lock a new huge page;
1290 * - scan page cache replacing old pages with the new one
1291 * + swap in pages if necessary;
1292 * + fill in gaps;
1293 * + keep old pages around in case rollback is required;
1294 * - if replacing succeeds:
1295 * + copy data over;
1296 * + free old pages;
1297 * + unlock huge page;
1298 * - if replacing failed;
1299 * + put all pages back and unfreeze them;
1300 * + restore gaps in the page cache;
1301 * + unlock and free huge page;
1302 */
1303static void collapse_shmem(struct mm_struct *mm,
1304 struct address_space *mapping, pgoff_t start,
1305 struct page **hpage, int node)
1306{
1307 gfp_t gfp;
1308 struct page *new_page;
1309 struct mem_cgroup *memcg;
1310 pgoff_t index, end = start + HPAGE_PMD_NR;
1311 LIST_HEAD(pagelist);
1312 XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
1313 int nr_none = 0, result = SCAN_SUCCEED;
1314
1315 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1316
1317 /* Only allocate from the target node */
1318 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
1319
1320 new_page = khugepaged_alloc_page(hpage, gfp, node);
1321 if (!new_page) {
1322 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1323 goto out;
1324 }
1325
1326 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
1327 result = SCAN_CGROUP_CHARGE_FAIL;
1328 goto out;
1329 }
1330
1331 /* This will be less messy when we use multi-index entries */
1332 do {
1333 xas_lock_irq(&xas);
1334 xas_create_range(&xas);
1335 if (!xas_error(&xas))
1336 break;
1337 xas_unlock_irq(&xas);
1338 if (!xas_nomem(&xas, GFP_KERNEL)) {
1339 mem_cgroup_cancel_charge(new_page, memcg, true);
1340 result = SCAN_FAIL;
1341 goto out;
1342 }
1343 } while (1);
1344
1345 __SetPageLocked(new_page);
1346 __SetPageSwapBacked(new_page);
1347 new_page->index = start;
1348 new_page->mapping = mapping;
1349
1350 /*
1351 * At this point the new_page is locked and not up-to-date.
1352 * It's safe to insert it into the page cache, because nobody would
1353 * be able to map it or use it in another way until we unlock it.
1354 */
1355
1356 xas_set(&xas, start);
1357 for (index = start; index < end; index++) {
1358 struct page *page = xas_next(&xas);
1359
1360 VM_BUG_ON(index != xas.xa_index);
1361 if (!page) {
1362 /*
1363 * Stop if extent has been truncated or hole-punched,
1364 * and is now completely empty.
1365 */
1366 if (index == start) {
1367 if (!xas_next_entry(&xas, end - 1)) {
1368 result = SCAN_TRUNCATED;
1369 goto xa_locked;
1370 }
1371 xas_set(&xas, index);
1372 }
1373 if (!shmem_charge(mapping->host, 1)) {
1374 result = SCAN_FAIL;
1375 goto xa_locked;
1376 }
1377 xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
1378 nr_none++;
1379 continue;
1380 }
1381
1382 if (xa_is_value(page) || !PageUptodate(page)) {
1383 xas_unlock_irq(&xas);
1384 /* swap in or instantiate fallocated page */
1385 if (shmem_getpage(mapping->host, index, &page,
1386 SGP_NOHUGE)) {
1387 result = SCAN_FAIL;
1388 goto xa_unlocked;
1389 }
1390 } else if (trylock_page(page)) {
1391 get_page(page);
1392 xas_unlock_irq(&xas);
1393 } else {
1394 result = SCAN_PAGE_LOCK;
1395 goto xa_locked;
1396 }
1397
1398 /*
1399 * The page must be locked, so we can drop the i_pages lock
1400 * without racing with truncate.
1401 */
1402 VM_BUG_ON_PAGE(!PageLocked(page), page);
1403 VM_BUG_ON_PAGE(!PageUptodate(page), page);
1404
1405 /*
1406 * If file was truncated then extended, or hole-punched, before
1407 * we locked the first page, then a THP might be there already.
1408 */
1409 if (PageTransCompound(page)) {
1410 result = SCAN_PAGE_COMPOUND;
1411 goto out_unlock;
1412 }
1413
1414 if (page_mapping(page) != mapping) {
1415 result = SCAN_TRUNCATED;
1416 goto out_unlock;
1417 }
1418
1419 if (isolate_lru_page(page)) {
1420 result = SCAN_DEL_PAGE_LRU;
1421 goto out_unlock;
1422 }
1423
1424 if (page_mapped(page))
1425 unmap_mapping_pages(mapping, index, 1, false);
1426
1427 xas_lock_irq(&xas);
1428 xas_set(&xas, index);
1429
1430 VM_BUG_ON_PAGE(page != xas_load(&xas), page);
1431 VM_BUG_ON_PAGE(page_mapped(page), page);
1432
1433 /*
1434 * The page is expected to have page_count() == 3:
1435 * - we hold a pin on it;
1436 * - one reference from page cache;
1437 * - one from isolate_lru_page;
1438 */
1439 if (!page_ref_freeze(page, 3)) {
1440 result = SCAN_PAGE_COUNT;
1441 xas_unlock_irq(&xas);
1442 putback_lru_page(page);
1443 goto out_unlock;
1444 }
1445
1446 /*
1447 * Add the page to the list to be able to undo the collapse if
1448 * something go wrong.
1449 */
1450 list_add_tail(&page->lru, &pagelist);
1451
1452 /* Finally, replace with the new page. */
1453 xas_store(&xas, new_page + (index % HPAGE_PMD_NR));
1454 continue;
1455out_unlock:
1456 unlock_page(page);
1457 put_page(page);
1458 goto xa_unlocked;
1459 }
1460
1461 __inc_node_page_state(new_page, NR_SHMEM_THPS);
1462 if (nr_none) {
1463 struct zone *zone = page_zone(new_page);
1464
1465 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
1466 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
1467 }
1468
1469xa_locked:
1470 xas_unlock_irq(&xas);
1471xa_unlocked:
1472
1473 if (result == SCAN_SUCCEED) {
1474 struct page *page, *tmp;
1475
1476 /*
1477 * Replacing old pages with new one has succeeded, now we
1478 * need to copy the content and free the old pages.
1479 */
1480 index = start;
1481 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
1482 while (index < page->index) {
1483 clear_highpage(new_page + (index % HPAGE_PMD_NR));
1484 index++;
1485 }
1486 copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
1487 page);
1488 list_del(&page->lru);
1489 page->mapping = NULL;
1490 page_ref_unfreeze(page, 1);
1491 ClearPageActive(page);
1492 ClearPageUnevictable(page);
1493 unlock_page(page);
1494 put_page(page);
1495 index++;
1496 }
1497 while (index < end) {
1498 clear_highpage(new_page + (index % HPAGE_PMD_NR));
1499 index++;
1500 }
1501
1502 SetPageUptodate(new_page);
1503 page_ref_add(new_page, HPAGE_PMD_NR - 1);
1504 set_page_dirty(new_page);
1505 mem_cgroup_commit_charge(new_page, memcg, false, true);
1506 count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1);
1507 lru_cache_add_anon(new_page);
1508
1509 /*
1510 * Remove pte page tables, so we can re-fault the page as huge.
1511 */
1512 retract_page_tables(mapping, start);
1513 *hpage = NULL;
1514
1515 khugepaged_pages_collapsed++;
1516 } else {
1517 struct page *page;
1518
1519 /* Something went wrong: roll back page cache changes */
1520 xas_lock_irq(&xas);
1521 mapping->nrpages -= nr_none;
1522 shmem_uncharge(mapping->host, nr_none);
1523
1524 xas_set(&xas, start);
1525 xas_for_each(&xas, page, end - 1) {
1526 page = list_first_entry_or_null(&pagelist,
1527 struct page, lru);
1528 if (!page || xas.xa_index < page->index) {
1529 if (!nr_none)
1530 break;
1531 nr_none--;
1532 /* Put holes back where they were */
1533 xas_store(&xas, NULL);
1534 continue;
1535 }
1536
1537 VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
1538
1539 /* Unfreeze the page. */
1540 list_del(&page->lru);
1541 page_ref_unfreeze(page, 2);
1542 xas_store(&xas, page);
1543 xas_pause(&xas);
1544 xas_unlock_irq(&xas);
1545 unlock_page(page);
1546 putback_lru_page(page);
1547 xas_lock_irq(&xas);
1548 }
1549 VM_BUG_ON(nr_none);
1550 xas_unlock_irq(&xas);
1551
1552 mem_cgroup_cancel_charge(new_page, memcg, true);
1553 new_page->mapping = NULL;
1554 }
1555
1556 unlock_page(new_page);
1557out:
1558 VM_BUG_ON(!list_empty(&pagelist));
1559 /* TODO: tracepoints */
1560}
1561
1562static void khugepaged_scan_shmem(struct mm_struct *mm,
1563 struct address_space *mapping,
1564 pgoff_t start, struct page **hpage)
1565{
1566 struct page *page = NULL;
1567 XA_STATE(xas, &mapping->i_pages, start);
1568 int present, swap;
1569 int node = NUMA_NO_NODE;
1570 int result = SCAN_SUCCEED;
1571
1572 present = 0;
1573 swap = 0;
1574 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1575 rcu_read_lock();
1576 xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) {
1577 if (xas_retry(&xas, page))
1578 continue;
1579
1580 if (xa_is_value(page)) {
1581 if (++swap > khugepaged_max_ptes_swap) {
1582 result = SCAN_EXCEED_SWAP_PTE;
1583 break;
1584 }
1585 continue;
1586 }
1587
1588 if (PageTransCompound(page)) {
1589 result = SCAN_PAGE_COMPOUND;
1590 break;
1591 }
1592
1593 node = page_to_nid(page);
1594 if (khugepaged_scan_abort(node)) {
1595 result = SCAN_SCAN_ABORT;
1596 break;
1597 }
1598 khugepaged_node_load[node]++;
1599
1600 if (!PageLRU(page)) {
1601 result = SCAN_PAGE_LRU;
1602 break;
1603 }
1604
1605 if (page_count(page) != 1 + page_mapcount(page)) {
1606 result = SCAN_PAGE_COUNT;
1607 break;
1608 }
1609
1610 /*
1611 * We probably should check if the page is referenced here, but
1612 * nobody would transfer pte_young() to PageReferenced() for us.
1613 * And rmap walk here is just too costly...
1614 */
1615
1616 present++;
1617
1618 if (need_resched()) {
1619 xas_pause(&xas);
1620 cond_resched_rcu();
1621 }
1622 }
1623 rcu_read_unlock();
1624
1625 if (result == SCAN_SUCCEED) {
1626 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
1627 result = SCAN_EXCEED_NONE_PTE;
1628 } else {
1629 node = khugepaged_find_target_node();
1630 collapse_shmem(mm, mapping, start, hpage, node);
1631 }
1632 }
1633
1634 /* TODO: tracepoints */
1635}
1636#else
1637static void khugepaged_scan_shmem(struct mm_struct *mm,
1638 struct address_space *mapping,
1639 pgoff_t start, struct page **hpage)
1640{
1641 BUILD_BUG();
1642}
1643#endif
1644
1645static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1646 struct page **hpage)
1647 __releases(&khugepaged_mm_lock)
1648 __acquires(&khugepaged_mm_lock)
1649{
1650 struct mm_slot *mm_slot;
1651 struct mm_struct *mm;
1652 struct vm_area_struct *vma;
1653 int progress = 0;
1654
1655 VM_BUG_ON(!pages);
1656 lockdep_assert_held(&khugepaged_mm_lock);
1657
1658 if (khugepaged_scan.mm_slot)
1659 mm_slot = khugepaged_scan.mm_slot;
1660 else {
1661 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1662 struct mm_slot, mm_node);
1663 khugepaged_scan.address = 0;
1664 khugepaged_scan.mm_slot = mm_slot;
1665 }
1666 spin_unlock(&khugepaged_mm_lock);
1667
1668 mm = mm_slot->mm;
1669 /*
1670 * Don't wait for semaphore (to avoid long wait times). Just move to
1671 * the next mm on the list.
1672 */
1673 vma = NULL;
1674 if (unlikely(!down_read_trylock(&mm->mmap_sem)))
1675 goto breakouterloop_mmap_sem;
1676 if (likely(!khugepaged_test_exit(mm)))
1677 vma = find_vma(mm, khugepaged_scan.address);
1678
1679 progress++;
1680 for (; vma; vma = vma->vm_next) {
1681 unsigned long hstart, hend;
1682
1683 cond_resched();
1684 if (unlikely(khugepaged_test_exit(mm))) {
1685 progress++;
1686 break;
1687 }
1688 if (!hugepage_vma_check(vma, vma->vm_flags)) {
1689skip:
1690 progress++;
1691 continue;
1692 }
1693 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1694 hend = vma->vm_end & HPAGE_PMD_MASK;
1695 if (hstart >= hend)
1696 goto skip;
1697 if (khugepaged_scan.address > hend)
1698 goto skip;
1699 if (khugepaged_scan.address < hstart)
1700 khugepaged_scan.address = hstart;
1701 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1702
1703 while (khugepaged_scan.address < hend) {
1704 int ret;
1705 cond_resched();
1706 if (unlikely(khugepaged_test_exit(mm)))
1707 goto breakouterloop;
1708
1709 VM_BUG_ON(khugepaged_scan.address < hstart ||
1710 khugepaged_scan.address + HPAGE_PMD_SIZE >
1711 hend);
1712 if (shmem_file(vma->vm_file)) {
1713 struct file *file;
1714 pgoff_t pgoff = linear_page_index(vma,
1715 khugepaged_scan.address);
1716 if (!shmem_huge_enabled(vma))
1717 goto skip;
1718 file = get_file(vma->vm_file);
1719 up_read(&mm->mmap_sem);
1720 ret = 1;
1721 khugepaged_scan_shmem(mm, file->f_mapping,
1722 pgoff, hpage);
1723 fput(file);
1724 } else {
1725 ret = khugepaged_scan_pmd(mm, vma,
1726 khugepaged_scan.address,
1727 hpage);
1728 }
1729 /* move to next address */
1730 khugepaged_scan.address += HPAGE_PMD_SIZE;
1731 progress += HPAGE_PMD_NR;
1732 if (ret)
1733 /* we released mmap_sem so break loop */
1734 goto breakouterloop_mmap_sem;
1735 if (progress >= pages)
1736 goto breakouterloop;
1737 }
1738 }
1739breakouterloop:
1740 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1741breakouterloop_mmap_sem:
1742
1743 spin_lock(&khugepaged_mm_lock);
1744 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1745 /*
1746 * Release the current mm_slot if this mm is about to die, or
1747 * if we scanned all vmas of this mm.
1748 */
1749 if (khugepaged_test_exit(mm) || !vma) {
1750 /*
1751 * Make sure that if mm_users is reaching zero while
1752 * khugepaged runs here, khugepaged_exit will find
1753 * mm_slot not pointing to the exiting mm.
1754 */
1755 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1756 khugepaged_scan.mm_slot = list_entry(
1757 mm_slot->mm_node.next,
1758 struct mm_slot, mm_node);
1759 khugepaged_scan.address = 0;
1760 } else {
1761 khugepaged_scan.mm_slot = NULL;
1762 khugepaged_full_scans++;
1763 }
1764
1765 collect_mm_slot(mm_slot);
1766 }
1767
1768 return progress;
1769}
1770
1771static int khugepaged_has_work(void)
1772{
1773 return !list_empty(&khugepaged_scan.mm_head) &&
1774 khugepaged_enabled();
1775}
1776
1777static int khugepaged_wait_event(void)
1778{
1779 return !list_empty(&khugepaged_scan.mm_head) ||
1780 kthread_should_stop();
1781}
1782
1783static void khugepaged_do_scan(void)
1784{
1785 struct page *hpage = NULL;
1786 unsigned int progress = 0, pass_through_head = 0;
1787 unsigned int pages = khugepaged_pages_to_scan;
1788 bool wait = true;
1789
1790 barrier(); /* write khugepaged_pages_to_scan to local stack */
1791
1792 while (progress < pages) {
1793 if (!khugepaged_prealloc_page(&hpage, &wait))
1794 break;
1795
1796 cond_resched();
1797
1798 if (unlikely(kthread_should_stop() || try_to_freeze()))
1799 break;
1800
1801 spin_lock(&khugepaged_mm_lock);
1802 if (!khugepaged_scan.mm_slot)
1803 pass_through_head++;
1804 if (khugepaged_has_work() &&
1805 pass_through_head < 2)
1806 progress += khugepaged_scan_mm_slot(pages - progress,
1807 &hpage);
1808 else
1809 progress = pages;
1810 spin_unlock(&khugepaged_mm_lock);
1811 }
1812
1813 if (!IS_ERR_OR_NULL(hpage))
1814 put_page(hpage);
1815}
1816
1817static bool khugepaged_should_wakeup(void)
1818{
1819 return kthread_should_stop() ||
1820 time_after_eq(jiffies, khugepaged_sleep_expire);
1821}
1822
1823static void khugepaged_wait_work(void)
1824{
1825 if (khugepaged_has_work()) {
1826 const unsigned long scan_sleep_jiffies =
1827 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
1828
1829 if (!scan_sleep_jiffies)
1830 return;
1831
1832 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
1833 wait_event_freezable_timeout(khugepaged_wait,
1834 khugepaged_should_wakeup(),
1835 scan_sleep_jiffies);
1836 return;
1837 }
1838
1839 if (khugepaged_enabled())
1840 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
1841}
1842
1843static int khugepaged(void *none)
1844{
1845 struct mm_slot *mm_slot;
1846
1847 set_freezable();
1848 set_user_nice(current, MAX_NICE);
1849
1850 while (!kthread_should_stop()) {
1851 khugepaged_do_scan();
1852 khugepaged_wait_work();
1853 }
1854
1855 spin_lock(&khugepaged_mm_lock);
1856 mm_slot = khugepaged_scan.mm_slot;
1857 khugepaged_scan.mm_slot = NULL;
1858 if (mm_slot)
1859 collect_mm_slot(mm_slot);
1860 spin_unlock(&khugepaged_mm_lock);
1861 return 0;
1862}
1863
1864static void set_recommended_min_free_kbytes(void)
1865{
1866 struct zone *zone;
1867 int nr_zones = 0;
1868 unsigned long recommended_min;
1869
1870 for_each_populated_zone(zone) {
1871 /*
1872 * We don't need to worry about fragmentation of
1873 * ZONE_MOVABLE since it only has movable pages.
1874 */
1875 if (zone_idx(zone) > gfp_zone(GFP_USER))
1876 continue;
1877
1878 nr_zones++;
1879 }
1880
1881 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1882 recommended_min = pageblock_nr_pages * nr_zones * 2;
1883
1884 /*
1885 * Make sure that on average at least two pageblocks are almost free
1886 * of another type, one for a migratetype to fall back to and a
1887 * second to avoid subsequent fallbacks of other types There are 3
1888 * MIGRATE_TYPES we care about.
1889 */
1890 recommended_min += pageblock_nr_pages * nr_zones *
1891 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
1892
1893 /* don't ever allow to reserve more than 5% of the lowmem */
1894 recommended_min = min(recommended_min,
1895 (unsigned long) nr_free_buffer_pages() / 20);
1896 recommended_min <<= (PAGE_SHIFT-10);
1897
1898 if (recommended_min > min_free_kbytes) {
1899 if (user_min_free_kbytes >= 0)
1900 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1901 min_free_kbytes, recommended_min);
1902
1903 min_free_kbytes = recommended_min;
1904 }
1905 setup_per_zone_wmarks();
1906}
1907
1908int start_stop_khugepaged(void)
1909{
1910 static struct task_struct *khugepaged_thread __read_mostly;
1911 static DEFINE_MUTEX(khugepaged_mutex);
1912 int err = 0;
1913
1914 mutex_lock(&khugepaged_mutex);
1915 if (khugepaged_enabled()) {
1916 if (!khugepaged_thread)
1917 khugepaged_thread = kthread_run(khugepaged, NULL,
1918 "khugepaged");
1919 if (IS_ERR(khugepaged_thread)) {
1920 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1921 err = PTR_ERR(khugepaged_thread);
1922 khugepaged_thread = NULL;
1923 goto fail;
1924 }
1925
1926 if (!list_empty(&khugepaged_scan.mm_head))
1927 wake_up_interruptible(&khugepaged_wait);
1928
1929 set_recommended_min_free_kbytes();
1930 } else if (khugepaged_thread) {
1931 kthread_stop(khugepaged_thread);
1932 khugepaged_thread = NULL;
1933 }
1934fail:
1935 mutex_unlock(&khugepaged_mutex);
1936 return err;
1937}
1938