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1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
2
3 #include <linux/mm.h>
4 #include <linux/sched.h>
5 #include <linux/mmu_notifier.h>
6 #include <linux/rmap.h>
7 #include <linux/swap.h>
8 #include <linux/mm_inline.h>
9 #include <linux/kthread.h>
10 #include <linux/khugepaged.h>
11 #include <linux/freezer.h>
12 #include <linux/mman.h>
13 #include <linux/hashtable.h>
14 #include <linux/userfaultfd_k.h>
15 #include <linux/page_idle.h>
16 #include <linux/swapops.h>
17 #include <linux/shmem_fs.h>
18
19 #include <asm/tlb.h>
20 #include <asm/pgalloc.h>
21 #include "internal.h"
22
23 enum scan_result {
24 SCAN_FAIL,
25 SCAN_SUCCEED,
26 SCAN_PMD_NULL,
27 SCAN_EXCEED_NONE_PTE,
28 SCAN_PTE_NON_PRESENT,
29 SCAN_PAGE_RO,
30 SCAN_LACK_REFERENCED_PAGE,
31 SCAN_PAGE_NULL,
32 SCAN_SCAN_ABORT,
33 SCAN_PAGE_COUNT,
34 SCAN_PAGE_LRU,
35 SCAN_PAGE_LOCK,
36 SCAN_PAGE_ANON,
37 SCAN_PAGE_COMPOUND,
38 SCAN_ANY_PROCESS,
39 SCAN_VMA_NULL,
40 SCAN_VMA_CHECK,
41 SCAN_ADDRESS_RANGE,
42 SCAN_SWAP_CACHE_PAGE,
43 SCAN_DEL_PAGE_LRU,
44 SCAN_ALLOC_HUGE_PAGE_FAIL,
45 SCAN_CGROUP_CHARGE_FAIL,
46 SCAN_EXCEED_SWAP_PTE,
47 SCAN_TRUNCATED,
48 };
49
50 #define CREATE_TRACE_POINTS
51 #include <trace/events/huge_memory.h>
52
53 /* default scan 8*512 pte (or vmas) every 30 second */
54 static unsigned int khugepaged_pages_to_scan __read_mostly;
55 static unsigned int khugepaged_pages_collapsed;
56 static unsigned int khugepaged_full_scans;
57 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
58 /* during fragmentation poll the hugepage allocator once every minute */
59 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
60 static unsigned long khugepaged_sleep_expire;
61 static DEFINE_SPINLOCK(khugepaged_mm_lock);
62 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
63 /*
64 * default collapse hugepages if there is at least one pte mapped like
65 * it would have happened if the vma was large enough during page
66 * fault.
67 */
68 static unsigned int khugepaged_max_ptes_none __read_mostly;
69 static unsigned int khugepaged_max_ptes_swap __read_mostly;
70
71 #define MM_SLOTS_HASH_BITS 10
72 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
73
74 static struct kmem_cache *mm_slot_cache __read_mostly;
75
76 /**
77 * struct mm_slot - hash lookup from mm to mm_slot
78 * @hash: hash collision list
79 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
80 * @mm: the mm that this information is valid for
81 */
82 struct mm_slot {
83 struct hlist_node hash;
84 struct list_head mm_node;
85 struct mm_struct *mm;
86 };
87
88 /**
89 * struct khugepaged_scan - cursor for scanning
90 * @mm_head: the head of the mm list to scan
91 * @mm_slot: the current mm_slot we are scanning
92 * @address: the next address inside that to be scanned
93 *
94 * There is only the one khugepaged_scan instance of this cursor structure.
95 */
96 struct khugepaged_scan {
97 struct list_head mm_head;
98 struct mm_slot *mm_slot;
99 unsigned long address;
100 };
101
102 static struct khugepaged_scan khugepaged_scan = {
103 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
104 };
105
106 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
107 struct kobj_attribute *attr,
108 char *buf)
109 {
110 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
111 }
112
113 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
114 struct kobj_attribute *attr,
115 const char *buf, size_t count)
116 {
117 unsigned long msecs;
118 int err;
119
120 err = kstrtoul(buf, 10, &msecs);
121 if (err || msecs > UINT_MAX)
122 return -EINVAL;
123
124 khugepaged_scan_sleep_millisecs = msecs;
125 khugepaged_sleep_expire = 0;
126 wake_up_interruptible(&khugepaged_wait);
127
128 return count;
129 }
130 static struct kobj_attribute scan_sleep_millisecs_attr =
131 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
132 scan_sleep_millisecs_store);
133
134 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
135 struct kobj_attribute *attr,
136 char *buf)
137 {
138 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
139 }
140
141 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
142 struct kobj_attribute *attr,
143 const char *buf, size_t count)
144 {
145 unsigned long msecs;
146 int err;
147
148 err = kstrtoul(buf, 10, &msecs);
149 if (err || msecs > UINT_MAX)
150 return -EINVAL;
151
152 khugepaged_alloc_sleep_millisecs = msecs;
153 khugepaged_sleep_expire = 0;
154 wake_up_interruptible(&khugepaged_wait);
155
156 return count;
157 }
158 static struct kobj_attribute alloc_sleep_millisecs_attr =
159 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
160 alloc_sleep_millisecs_store);
161
162 static ssize_t pages_to_scan_show(struct kobject *kobj,
163 struct kobj_attribute *attr,
164 char *buf)
165 {
166 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
167 }
168 static ssize_t pages_to_scan_store(struct kobject *kobj,
169 struct kobj_attribute *attr,
170 const char *buf, size_t count)
171 {
172 int err;
173 unsigned long pages;
174
175 err = kstrtoul(buf, 10, &pages);
176 if (err || !pages || pages > UINT_MAX)
177 return -EINVAL;
178
179 khugepaged_pages_to_scan = pages;
180
181 return count;
182 }
183 static struct kobj_attribute pages_to_scan_attr =
184 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
185 pages_to_scan_store);
186
187 static ssize_t pages_collapsed_show(struct kobject *kobj,
188 struct kobj_attribute *attr,
189 char *buf)
190 {
191 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
192 }
193 static struct kobj_attribute pages_collapsed_attr =
194 __ATTR_RO(pages_collapsed);
195
196 static ssize_t full_scans_show(struct kobject *kobj,
197 struct kobj_attribute *attr,
198 char *buf)
199 {
200 return sprintf(buf, "%u\n", khugepaged_full_scans);
201 }
202 static struct kobj_attribute full_scans_attr =
203 __ATTR_RO(full_scans);
204
205 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
206 struct kobj_attribute *attr, char *buf)
207 {
208 return single_hugepage_flag_show(kobj, attr, buf,
209 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
210 }
211 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
212 struct kobj_attribute *attr,
213 const char *buf, size_t count)
214 {
215 return single_hugepage_flag_store(kobj, attr, buf, count,
216 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
217 }
218 static struct kobj_attribute khugepaged_defrag_attr =
219 __ATTR(defrag, 0644, khugepaged_defrag_show,
220 khugepaged_defrag_store);
221
222 /*
223 * max_ptes_none controls if khugepaged should collapse hugepages over
224 * any unmapped ptes in turn potentially increasing the memory
225 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
226 * reduce the available free memory in the system as it
227 * runs. Increasing max_ptes_none will instead potentially reduce the
228 * free memory in the system during the khugepaged scan.
229 */
230 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
231 struct kobj_attribute *attr,
232 char *buf)
233 {
234 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
235 }
236 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
237 struct kobj_attribute *attr,
238 const char *buf, size_t count)
239 {
240 int err;
241 unsigned long max_ptes_none;
242
243 err = kstrtoul(buf, 10, &max_ptes_none);
244 if (err || max_ptes_none > HPAGE_PMD_NR-1)
245 return -EINVAL;
246
247 khugepaged_max_ptes_none = max_ptes_none;
248
249 return count;
250 }
251 static struct kobj_attribute khugepaged_max_ptes_none_attr =
252 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
253 khugepaged_max_ptes_none_store);
254
255 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
256 struct kobj_attribute *attr,
257 char *buf)
258 {
259 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
260 }
261
262 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
263 struct kobj_attribute *attr,
264 const char *buf, size_t count)
265 {
266 int err;
267 unsigned long max_ptes_swap;
268
269 err = kstrtoul(buf, 10, &max_ptes_swap);
270 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
271 return -EINVAL;
272
273 khugepaged_max_ptes_swap = max_ptes_swap;
274
275 return count;
276 }
277
278 static struct kobj_attribute khugepaged_max_ptes_swap_attr =
279 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
280 khugepaged_max_ptes_swap_store);
281
282 static struct attribute *khugepaged_attr[] = {
283 &khugepaged_defrag_attr.attr,
284 &khugepaged_max_ptes_none_attr.attr,
285 &pages_to_scan_attr.attr,
286 &pages_collapsed_attr.attr,
287 &full_scans_attr.attr,
288 &scan_sleep_millisecs_attr.attr,
289 &alloc_sleep_millisecs_attr.attr,
290 &khugepaged_max_ptes_swap_attr.attr,
291 NULL,
292 };
293
294 struct attribute_group khugepaged_attr_group = {
295 .attrs = khugepaged_attr,
296 .name = "khugepaged",
297 };
298
299 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
300
301 int hugepage_madvise(struct vm_area_struct *vma,
302 unsigned long *vm_flags, int advice)
303 {
304 switch (advice) {
305 case MADV_HUGEPAGE:
306 #ifdef CONFIG_S390
307 /*
308 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
309 * can't handle this properly after s390_enable_sie, so we simply
310 * ignore the madvise to prevent qemu from causing a SIGSEGV.
311 */
312 if (mm_has_pgste(vma->vm_mm))
313 return 0;
314 #endif
315 *vm_flags &= ~VM_NOHUGEPAGE;
316 *vm_flags |= VM_HUGEPAGE;
317 /*
318 * If the vma become good for khugepaged to scan,
319 * register it here without waiting a page fault that
320 * may not happen any time soon.
321 */
322 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
323 khugepaged_enter_vma_merge(vma, *vm_flags))
324 return -ENOMEM;
325 break;
326 case MADV_NOHUGEPAGE:
327 *vm_flags &= ~VM_HUGEPAGE;
328 *vm_flags |= VM_NOHUGEPAGE;
329 /*
330 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
331 * this vma even if we leave the mm registered in khugepaged if
332 * it got registered before VM_NOHUGEPAGE was set.
333 */
334 break;
335 }
336
337 return 0;
338 }
339
340 int __init khugepaged_init(void)
341 {
342 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
343 sizeof(struct mm_slot),
344 __alignof__(struct mm_slot), 0, NULL);
345 if (!mm_slot_cache)
346 return -ENOMEM;
347
348 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
349 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
350 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
351
352 return 0;
353 }
354
355 void __init khugepaged_destroy(void)
356 {
357 kmem_cache_destroy(mm_slot_cache);
358 }
359
360 static inline struct mm_slot *alloc_mm_slot(void)
361 {
362 if (!mm_slot_cache) /* initialization failed */
363 return NULL;
364 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
365 }
366
367 static inline void free_mm_slot(struct mm_slot *mm_slot)
368 {
369 kmem_cache_free(mm_slot_cache, mm_slot);
370 }
371
372 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
373 {
374 struct mm_slot *mm_slot;
375
376 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
377 if (mm == mm_slot->mm)
378 return mm_slot;
379
380 return NULL;
381 }
382
383 static void insert_to_mm_slots_hash(struct mm_struct *mm,
384 struct mm_slot *mm_slot)
385 {
386 mm_slot->mm = mm;
387 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
388 }
389
390 static inline int khugepaged_test_exit(struct mm_struct *mm)
391 {
392 return atomic_read(&mm->mm_users) == 0;
393 }
394
395 int __khugepaged_enter(struct mm_struct *mm)
396 {
397 struct mm_slot *mm_slot;
398 int wakeup;
399
400 mm_slot = alloc_mm_slot();
401 if (!mm_slot)
402 return -ENOMEM;
403
404 /* __khugepaged_exit() must not run from under us */
405 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
406 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
407 free_mm_slot(mm_slot);
408 return 0;
409 }
410
411 spin_lock(&khugepaged_mm_lock);
412 insert_to_mm_slots_hash(mm, mm_slot);
413 /*
414 * Insert just behind the scanning cursor, to let the area settle
415 * down a little.
416 */
417 wakeup = list_empty(&khugepaged_scan.mm_head);
418 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
419 spin_unlock(&khugepaged_mm_lock);
420
421 atomic_inc(&mm->mm_count);
422 if (wakeup)
423 wake_up_interruptible(&khugepaged_wait);
424
425 return 0;
426 }
427
428 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
429 unsigned long vm_flags)
430 {
431 unsigned long hstart, hend;
432 if (!vma->anon_vma)
433 /*
434 * Not yet faulted in so we will register later in the
435 * page fault if needed.
436 */
437 return 0;
438 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
439 /* khugepaged not yet working on file or special mappings */
440 return 0;
441 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
442 hend = vma->vm_end & HPAGE_PMD_MASK;
443 if (hstart < hend)
444 return khugepaged_enter(vma, vm_flags);
445 return 0;
446 }
447
448 void __khugepaged_exit(struct mm_struct *mm)
449 {
450 struct mm_slot *mm_slot;
451 int free = 0;
452
453 spin_lock(&khugepaged_mm_lock);
454 mm_slot = get_mm_slot(mm);
455 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
456 hash_del(&mm_slot->hash);
457 list_del(&mm_slot->mm_node);
458 free = 1;
459 }
460 spin_unlock(&khugepaged_mm_lock);
461
462 if (free) {
463 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
464 free_mm_slot(mm_slot);
465 mmdrop(mm);
466 } else if (mm_slot) {
467 /*
468 * This is required to serialize against
469 * khugepaged_test_exit() (which is guaranteed to run
470 * under mmap sem read mode). Stop here (after we
471 * return all pagetables will be destroyed) until
472 * khugepaged has finished working on the pagetables
473 * under the mmap_sem.
474 */
475 down_write(&mm->mmap_sem);
476 up_write(&mm->mmap_sem);
477 }
478 }
479
480 static void release_pte_page(struct page *page)
481 {
482 /* 0 stands for page_is_file_cache(page) == false */
483 dec_node_page_state(page, NR_ISOLATED_ANON + 0);
484 unlock_page(page);
485 putback_lru_page(page);
486 }
487
488 static void release_pte_pages(pte_t *pte, pte_t *_pte)
489 {
490 while (--_pte >= pte) {
491 pte_t pteval = *_pte;
492 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
493 release_pte_page(pte_page(pteval));
494 }
495 }
496
497 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
498 unsigned long address,
499 pte_t *pte)
500 {
501 struct page *page = NULL;
502 pte_t *_pte;
503 int none_or_zero = 0, result = 0, referenced = 0;
504 bool writable = false;
505
506 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
507 _pte++, address += PAGE_SIZE) {
508 pte_t pteval = *_pte;
509 if (pte_none(pteval) || (pte_present(pteval) &&
510 is_zero_pfn(pte_pfn(pteval)))) {
511 if (!userfaultfd_armed(vma) &&
512 ++none_or_zero <= khugepaged_max_ptes_none) {
513 continue;
514 } else {
515 result = SCAN_EXCEED_NONE_PTE;
516 goto out;
517 }
518 }
519 if (!pte_present(pteval)) {
520 result = SCAN_PTE_NON_PRESENT;
521 goto out;
522 }
523 page = vm_normal_page(vma, address, pteval);
524 if (unlikely(!page)) {
525 result = SCAN_PAGE_NULL;
526 goto out;
527 }
528
529 VM_BUG_ON_PAGE(PageCompound(page), page);
530 VM_BUG_ON_PAGE(!PageAnon(page), page);
531 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
532
533 /*
534 * We can do it before isolate_lru_page because the
535 * page can't be freed from under us. NOTE: PG_lock
536 * is needed to serialize against split_huge_page
537 * when invoked from the VM.
538 */
539 if (!trylock_page(page)) {
540 result = SCAN_PAGE_LOCK;
541 goto out;
542 }
543
544 /*
545 * cannot use mapcount: can't collapse if there's a gup pin.
546 * The page must only be referenced by the scanned process
547 * and page swap cache.
548 */
549 if (page_count(page) != 1 + !!PageSwapCache(page)) {
550 unlock_page(page);
551 result = SCAN_PAGE_COUNT;
552 goto out;
553 }
554 if (pte_write(pteval)) {
555 writable = true;
556 } else {
557 if (PageSwapCache(page) &&
558 !reuse_swap_page(page, NULL)) {
559 unlock_page(page);
560 result = SCAN_SWAP_CACHE_PAGE;
561 goto out;
562 }
563 /*
564 * Page is not in the swap cache. It can be collapsed
565 * into a THP.
566 */
567 }
568
569 /*
570 * Isolate the page to avoid collapsing an hugepage
571 * currently in use by the VM.
572 */
573 if (isolate_lru_page(page)) {
574 unlock_page(page);
575 result = SCAN_DEL_PAGE_LRU;
576 goto out;
577 }
578 /* 0 stands for page_is_file_cache(page) == false */
579 inc_node_page_state(page, NR_ISOLATED_ANON + 0);
580 VM_BUG_ON_PAGE(!PageLocked(page), page);
581 VM_BUG_ON_PAGE(PageLRU(page), page);
582
583 /* There should be enough young pte to collapse the page */
584 if (pte_young(pteval) ||
585 page_is_young(page) || PageReferenced(page) ||
586 mmu_notifier_test_young(vma->vm_mm, address))
587 referenced++;
588 }
589 if (likely(writable)) {
590 if (likely(referenced)) {
591 result = SCAN_SUCCEED;
592 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
593 referenced, writable, result);
594 return 1;
595 }
596 } else {
597 result = SCAN_PAGE_RO;
598 }
599
600 out:
601 release_pte_pages(pte, _pte);
602 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
603 referenced, writable, result);
604 return 0;
605 }
606
607 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
608 struct vm_area_struct *vma,
609 unsigned long address,
610 spinlock_t *ptl)
611 {
612 pte_t *_pte;
613 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
614 pte_t pteval = *_pte;
615 struct page *src_page;
616
617 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
618 clear_user_highpage(page, address);
619 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
620 if (is_zero_pfn(pte_pfn(pteval))) {
621 /*
622 * ptl mostly unnecessary.
623 */
624 spin_lock(ptl);
625 /*
626 * paravirt calls inside pte_clear here are
627 * superfluous.
628 */
629 pte_clear(vma->vm_mm, address, _pte);
630 spin_unlock(ptl);
631 }
632 } else {
633 src_page = pte_page(pteval);
634 copy_user_highpage(page, src_page, address, vma);
635 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
636 release_pte_page(src_page);
637 /*
638 * ptl mostly unnecessary, but preempt has to
639 * be disabled to update the per-cpu stats
640 * inside page_remove_rmap().
641 */
642 spin_lock(ptl);
643 /*
644 * paravirt calls inside pte_clear here are
645 * superfluous.
646 */
647 pte_clear(vma->vm_mm, address, _pte);
648 page_remove_rmap(src_page, false);
649 spin_unlock(ptl);
650 free_page_and_swap_cache(src_page);
651 }
652
653 address += PAGE_SIZE;
654 page++;
655 }
656 }
657
658 static void khugepaged_alloc_sleep(void)
659 {
660 DEFINE_WAIT(wait);
661
662 add_wait_queue(&khugepaged_wait, &wait);
663 freezable_schedule_timeout_interruptible(
664 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
665 remove_wait_queue(&khugepaged_wait, &wait);
666 }
667
668 static int khugepaged_node_load[MAX_NUMNODES];
669
670 static bool khugepaged_scan_abort(int nid)
671 {
672 int i;
673
674 /*
675 * If node_reclaim_mode is disabled, then no extra effort is made to
676 * allocate memory locally.
677 */
678 if (!node_reclaim_mode)
679 return false;
680
681 /* If there is a count for this node already, it must be acceptable */
682 if (khugepaged_node_load[nid])
683 return false;
684
685 for (i = 0; i < MAX_NUMNODES; i++) {
686 if (!khugepaged_node_load[i])
687 continue;
688 if (node_distance(nid, i) > RECLAIM_DISTANCE)
689 return true;
690 }
691 return false;
692 }
693
694 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
695 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
696 {
697 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
698 }
699
700 #ifdef CONFIG_NUMA
701 static int khugepaged_find_target_node(void)
702 {
703 static int last_khugepaged_target_node = NUMA_NO_NODE;
704 int nid, target_node = 0, max_value = 0;
705
706 /* find first node with max normal pages hit */
707 for (nid = 0; nid < MAX_NUMNODES; nid++)
708 if (khugepaged_node_load[nid] > max_value) {
709 max_value = khugepaged_node_load[nid];
710 target_node = nid;
711 }
712
713 /* do some balance if several nodes have the same hit record */
714 if (target_node <= last_khugepaged_target_node)
715 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
716 nid++)
717 if (max_value == khugepaged_node_load[nid]) {
718 target_node = nid;
719 break;
720 }
721
722 last_khugepaged_target_node = target_node;
723 return target_node;
724 }
725
726 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
727 {
728 if (IS_ERR(*hpage)) {
729 if (!*wait)
730 return false;
731
732 *wait = false;
733 *hpage = NULL;
734 khugepaged_alloc_sleep();
735 } else if (*hpage) {
736 put_page(*hpage);
737 *hpage = NULL;
738 }
739
740 return true;
741 }
742
743 static struct page *
744 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
745 {
746 VM_BUG_ON_PAGE(*hpage, *hpage);
747
748 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
749 if (unlikely(!*hpage)) {
750 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
751 *hpage = ERR_PTR(-ENOMEM);
752 return NULL;
753 }
754
755 prep_transhuge_page(*hpage);
756 count_vm_event(THP_COLLAPSE_ALLOC);
757 return *hpage;
758 }
759 #else
760 static int khugepaged_find_target_node(void)
761 {
762 return 0;
763 }
764
765 static inline struct page *alloc_khugepaged_hugepage(void)
766 {
767 struct page *page;
768
769 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
770 HPAGE_PMD_ORDER);
771 if (page)
772 prep_transhuge_page(page);
773 return page;
774 }
775
776 static struct page *khugepaged_alloc_hugepage(bool *wait)
777 {
778 struct page *hpage;
779
780 do {
781 hpage = alloc_khugepaged_hugepage();
782 if (!hpage) {
783 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
784 if (!*wait)
785 return NULL;
786
787 *wait = false;
788 khugepaged_alloc_sleep();
789 } else
790 count_vm_event(THP_COLLAPSE_ALLOC);
791 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
792
793 return hpage;
794 }
795
796 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
797 {
798 if (!*hpage)
799 *hpage = khugepaged_alloc_hugepage(wait);
800
801 if (unlikely(!*hpage))
802 return false;
803
804 return true;
805 }
806
807 static struct page *
808 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
809 {
810 VM_BUG_ON(!*hpage);
811
812 return *hpage;
813 }
814 #endif
815
816 static bool hugepage_vma_check(struct vm_area_struct *vma)
817 {
818 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
819 (vma->vm_flags & VM_NOHUGEPAGE))
820 return false;
821 if (shmem_file(vma->vm_file)) {
822 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
823 return false;
824 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
825 HPAGE_PMD_NR);
826 }
827 if (!vma->anon_vma || vma->vm_ops)
828 return false;
829 if (is_vma_temporary_stack(vma))
830 return false;
831 return !(vma->vm_flags & VM_NO_KHUGEPAGED);
832 }
833
834 /*
835 * If mmap_sem temporarily dropped, revalidate vma
836 * before taking mmap_sem.
837 * Return 0 if succeeds, otherwise return none-zero
838 * value (scan code).
839 */
840
841 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
842 struct vm_area_struct **vmap)
843 {
844 struct vm_area_struct *vma;
845 unsigned long hstart, hend;
846
847 if (unlikely(khugepaged_test_exit(mm)))
848 return SCAN_ANY_PROCESS;
849
850 *vmap = vma = find_vma(mm, address);
851 if (!vma)
852 return SCAN_VMA_NULL;
853
854 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
855 hend = vma->vm_end & HPAGE_PMD_MASK;
856 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
857 return SCAN_ADDRESS_RANGE;
858 if (!hugepage_vma_check(vma))
859 return SCAN_VMA_CHECK;
860 return 0;
861 }
862
863 /*
864 * Bring missing pages in from swap, to complete THP collapse.
865 * Only done if khugepaged_scan_pmd believes it is worthwhile.
866 *
867 * Called and returns without pte mapped or spinlocks held,
868 * but with mmap_sem held to protect against vma changes.
869 */
870
871 static bool __collapse_huge_page_swapin(struct mm_struct *mm,
872 struct vm_area_struct *vma,
873 unsigned long address, pmd_t *pmd,
874 int referenced)
875 {
876 pte_t pteval;
877 int swapped_in = 0, ret = 0;
878 struct fault_env fe = {
879 .vma = vma,
880 .address = address,
881 .flags = FAULT_FLAG_ALLOW_RETRY,
882 .pmd = pmd,
883 };
884
885 /* we only decide to swapin, if there is enough young ptes */
886 if (referenced < HPAGE_PMD_NR/2) {
887 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
888 return false;
889 }
890 fe.pte = pte_offset_map(pmd, address);
891 for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE;
892 fe.pte++, fe.address += PAGE_SIZE) {
893 pteval = *fe.pte;
894 if (!is_swap_pte(pteval))
895 continue;
896 swapped_in++;
897 ret = do_swap_page(&fe, pteval);
898
899 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
900 if (ret & VM_FAULT_RETRY) {
901 down_read(&mm->mmap_sem);
902 if (hugepage_vma_revalidate(mm, address, &fe.vma)) {
903 /* vma is no longer available, don't continue to swapin */
904 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
905 return false;
906 }
907 /* check if the pmd is still valid */
908 if (mm_find_pmd(mm, address) != pmd)
909 return false;
910 }
911 if (ret & VM_FAULT_ERROR) {
912 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
913 return false;
914 }
915 /* pte is unmapped now, we need to map it */
916 fe.pte = pte_offset_map(pmd, fe.address);
917 }
918 fe.pte--;
919 pte_unmap(fe.pte);
920 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
921 return true;
922 }
923
924 static void collapse_huge_page(struct mm_struct *mm,
925 unsigned long address,
926 struct page **hpage,
927 int node, int referenced)
928 {
929 pmd_t *pmd, _pmd;
930 pte_t *pte;
931 pgtable_t pgtable;
932 struct page *new_page;
933 spinlock_t *pmd_ptl, *pte_ptl;
934 int isolated = 0, result = 0;
935 struct mem_cgroup *memcg;
936 struct vm_area_struct *vma;
937 unsigned long mmun_start; /* For mmu_notifiers */
938 unsigned long mmun_end; /* For mmu_notifiers */
939 gfp_t gfp;
940
941 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
942
943 /* Only allocate from the target node */
944 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
945
946 /*
947 * Before allocating the hugepage, release the mmap_sem read lock.
948 * The allocation can take potentially a long time if it involves
949 * sync compaction, and we do not need to hold the mmap_sem during
950 * that. We will recheck the vma after taking it again in write mode.
951 */
952 up_read(&mm->mmap_sem);
953 new_page = khugepaged_alloc_page(hpage, gfp, node);
954 if (!new_page) {
955 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
956 goto out_nolock;
957 }
958
959 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
960 result = SCAN_CGROUP_CHARGE_FAIL;
961 goto out_nolock;
962 }
963
964 down_read(&mm->mmap_sem);
965 result = hugepage_vma_revalidate(mm, address, &vma);
966 if (result) {
967 mem_cgroup_cancel_charge(new_page, memcg, true);
968 up_read(&mm->mmap_sem);
969 goto out_nolock;
970 }
971
972 pmd = mm_find_pmd(mm, address);
973 if (!pmd) {
974 result = SCAN_PMD_NULL;
975 mem_cgroup_cancel_charge(new_page, memcg, true);
976 up_read(&mm->mmap_sem);
977 goto out_nolock;
978 }
979
980 /*
981 * __collapse_huge_page_swapin always returns with mmap_sem locked.
982 * If it fails, we release mmap_sem and jump out_nolock.
983 * Continuing to collapse causes inconsistency.
984 */
985 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
986 mem_cgroup_cancel_charge(new_page, memcg, true);
987 up_read(&mm->mmap_sem);
988 goto out_nolock;
989 }
990
991 up_read(&mm->mmap_sem);
992 /*
993 * Prevent all access to pagetables with the exception of
994 * gup_fast later handled by the ptep_clear_flush and the VM
995 * handled by the anon_vma lock + PG_lock.
996 */
997 down_write(&mm->mmap_sem);
998 result = hugepage_vma_revalidate(mm, address, &vma);
999 if (result)
1000 goto out;
1001 /* check if the pmd is still valid */
1002 if (mm_find_pmd(mm, address) != pmd)
1003 goto out;
1004
1005 anon_vma_lock_write(vma->anon_vma);
1006
1007 pte = pte_offset_map(pmd, address);
1008 pte_ptl = pte_lockptr(mm, pmd);
1009
1010 mmun_start = address;
1011 mmun_end = address + HPAGE_PMD_SIZE;
1012 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1013 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1014 /*
1015 * After this gup_fast can't run anymore. This also removes
1016 * any huge TLB entry from the CPU so we won't allow
1017 * huge and small TLB entries for the same virtual address
1018 * to avoid the risk of CPU bugs in that area.
1019 */
1020 _pmd = pmdp_collapse_flush(vma, address, pmd);
1021 spin_unlock(pmd_ptl);
1022 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1023
1024 spin_lock(pte_ptl);
1025 isolated = __collapse_huge_page_isolate(vma, address, pte);
1026 spin_unlock(pte_ptl);
1027
1028 if (unlikely(!isolated)) {
1029 pte_unmap(pte);
1030 spin_lock(pmd_ptl);
1031 BUG_ON(!pmd_none(*pmd));
1032 /*
1033 * We can only use set_pmd_at when establishing
1034 * hugepmds and never for establishing regular pmds that
1035 * points to regular pagetables. Use pmd_populate for that
1036 */
1037 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1038 spin_unlock(pmd_ptl);
1039 anon_vma_unlock_write(vma->anon_vma);
1040 result = SCAN_FAIL;
1041 goto out;
1042 }
1043
1044 /*
1045 * All pages are isolated and locked so anon_vma rmap
1046 * can't run anymore.
1047 */
1048 anon_vma_unlock_write(vma->anon_vma);
1049
1050 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
1051 pte_unmap(pte);
1052 __SetPageUptodate(new_page);
1053 pgtable = pmd_pgtable(_pmd);
1054
1055 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1056 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1057
1058 /*
1059 * spin_lock() below is not the equivalent of smp_wmb(), so
1060 * this is needed to avoid the copy_huge_page writes to become
1061 * visible after the set_pmd_at() write.
1062 */
1063 smp_wmb();
1064
1065 spin_lock(pmd_ptl);
1066 BUG_ON(!pmd_none(*pmd));
1067 page_add_new_anon_rmap(new_page, vma, address, true);
1068 mem_cgroup_commit_charge(new_page, memcg, false, true);
1069 lru_cache_add_active_or_unevictable(new_page, vma);
1070 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1071 set_pmd_at(mm, address, pmd, _pmd);
1072 update_mmu_cache_pmd(vma, address, pmd);
1073 spin_unlock(pmd_ptl);
1074
1075 *hpage = NULL;
1076
1077 khugepaged_pages_collapsed++;
1078 result = SCAN_SUCCEED;
1079 out_up_write:
1080 up_write(&mm->mmap_sem);
1081 out_nolock:
1082 trace_mm_collapse_huge_page(mm, isolated, result);
1083 return;
1084 out:
1085 mem_cgroup_cancel_charge(new_page, memcg, true);
1086 goto out_up_write;
1087 }
1088
1089 static int khugepaged_scan_pmd(struct mm_struct *mm,
1090 struct vm_area_struct *vma,
1091 unsigned long address,
1092 struct page **hpage)
1093 {
1094 pmd_t *pmd;
1095 pte_t *pte, *_pte;
1096 int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
1097 struct page *page = NULL;
1098 unsigned long _address;
1099 spinlock_t *ptl;
1100 int node = NUMA_NO_NODE, unmapped = 0;
1101 bool writable = false;
1102
1103 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1104
1105 pmd = mm_find_pmd(mm, address);
1106 if (!pmd) {
1107 result = SCAN_PMD_NULL;
1108 goto out;
1109 }
1110
1111 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1112 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1113 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1114 _pte++, _address += PAGE_SIZE) {
1115 pte_t pteval = *_pte;
1116 if (is_swap_pte(pteval)) {
1117 if (++unmapped <= khugepaged_max_ptes_swap) {
1118 continue;
1119 } else {
1120 result = SCAN_EXCEED_SWAP_PTE;
1121 goto out_unmap;
1122 }
1123 }
1124 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1125 if (!userfaultfd_armed(vma) &&
1126 ++none_or_zero <= khugepaged_max_ptes_none) {
1127 continue;
1128 } else {
1129 result = SCAN_EXCEED_NONE_PTE;
1130 goto out_unmap;
1131 }
1132 }
1133 if (!pte_present(pteval)) {
1134 result = SCAN_PTE_NON_PRESENT;
1135 goto out_unmap;
1136 }
1137 if (pte_write(pteval))
1138 writable = true;
1139
1140 page = vm_normal_page(vma, _address, pteval);
1141 if (unlikely(!page)) {
1142 result = SCAN_PAGE_NULL;
1143 goto out_unmap;
1144 }
1145
1146 /* TODO: teach khugepaged to collapse THP mapped with pte */
1147 if (PageCompound(page)) {
1148 result = SCAN_PAGE_COMPOUND;
1149 goto out_unmap;
1150 }
1151
1152 /*
1153 * Record which node the original page is from and save this
1154 * information to khugepaged_node_load[].
1155 * Khupaged will allocate hugepage from the node has the max
1156 * hit record.
1157 */
1158 node = page_to_nid(page);
1159 if (khugepaged_scan_abort(node)) {
1160 result = SCAN_SCAN_ABORT;
1161 goto out_unmap;
1162 }
1163 khugepaged_node_load[node]++;
1164 if (!PageLRU(page)) {
1165 result = SCAN_PAGE_LRU;
1166 goto out_unmap;
1167 }
1168 if (PageLocked(page)) {
1169 result = SCAN_PAGE_LOCK;
1170 goto out_unmap;
1171 }
1172 if (!PageAnon(page)) {
1173 result = SCAN_PAGE_ANON;
1174 goto out_unmap;
1175 }
1176
1177 /*
1178 * cannot use mapcount: can't collapse if there's a gup pin.
1179 * The page must only be referenced by the scanned process
1180 * and page swap cache.
1181 */
1182 if (page_count(page) != 1 + !!PageSwapCache(page)) {
1183 result = SCAN_PAGE_COUNT;
1184 goto out_unmap;
1185 }
1186 if (pte_young(pteval) ||
1187 page_is_young(page) || PageReferenced(page) ||
1188 mmu_notifier_test_young(vma->vm_mm, address))
1189 referenced++;
1190 }
1191 if (writable) {
1192 if (referenced) {
1193 result = SCAN_SUCCEED;
1194 ret = 1;
1195 } else {
1196 result = SCAN_LACK_REFERENCED_PAGE;
1197 }
1198 } else {
1199 result = SCAN_PAGE_RO;
1200 }
1201 out_unmap:
1202 pte_unmap_unlock(pte, ptl);
1203 if (ret) {
1204 node = khugepaged_find_target_node();
1205 /* collapse_huge_page will return with the mmap_sem released */
1206 collapse_huge_page(mm, address, hpage, node, referenced);
1207 }
1208 out:
1209 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1210 none_or_zero, result, unmapped);
1211 return ret;
1212 }
1213
1214 static void collect_mm_slot(struct mm_slot *mm_slot)
1215 {
1216 struct mm_struct *mm = mm_slot->mm;
1217
1218 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1219
1220 if (khugepaged_test_exit(mm)) {
1221 /* free mm_slot */
1222 hash_del(&mm_slot->hash);
1223 list_del(&mm_slot->mm_node);
1224
1225 /*
1226 * Not strictly needed because the mm exited already.
1227 *
1228 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1229 */
1230
1231 /* khugepaged_mm_lock actually not necessary for the below */
1232 free_mm_slot(mm_slot);
1233 mmdrop(mm);
1234 }
1235 }
1236
1237 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
1238 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1239 {
1240 struct vm_area_struct *vma;
1241 unsigned long addr;
1242 pmd_t *pmd, _pmd;
1243
1244 i_mmap_lock_write(mapping);
1245 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1246 /* probably overkill */
1247 if (vma->anon_vma)
1248 continue;
1249 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1250 if (addr & ~HPAGE_PMD_MASK)
1251 continue;
1252 if (vma->vm_end < addr + HPAGE_PMD_SIZE)
1253 continue;
1254 pmd = mm_find_pmd(vma->vm_mm, addr);
1255 if (!pmd)
1256 continue;
1257 /*
1258 * We need exclusive mmap_sem to retract page table.
1259 * If trylock fails we would end up with pte-mapped THP after
1260 * re-fault. Not ideal, but it's more important to not disturb
1261 * the system too much.
1262 */
1263 if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
1264 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
1265 /* assume page table is clear */
1266 _pmd = pmdp_collapse_flush(vma, addr, pmd);
1267 spin_unlock(ptl);
1268 up_write(&vma->vm_mm->mmap_sem);
1269 atomic_long_dec(&vma->vm_mm->nr_ptes);
1270 pte_free(vma->vm_mm, pmd_pgtable(_pmd));
1271 }
1272 }
1273 i_mmap_unlock_write(mapping);
1274 }
1275
1276 /**
1277 * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
1278 *
1279 * Basic scheme is simple, details are more complex:
1280 * - allocate and freeze a new huge page;
1281 * - scan over radix tree replacing old pages the new one
1282 * + swap in pages if necessary;
1283 * + fill in gaps;
1284 * + keep old pages around in case if rollback is required;
1285 * - if replacing succeed:
1286 * + copy data over;
1287 * + free old pages;
1288 * + unfreeze huge page;
1289 * - if replacing failed;
1290 * + put all pages back and unfreeze them;
1291 * + restore gaps in the radix-tree;
1292 * + free huge page;
1293 */
1294 static void collapse_shmem(struct mm_struct *mm,
1295 struct address_space *mapping, pgoff_t start,
1296 struct page **hpage, int node)
1297 {
1298 gfp_t gfp;
1299 struct page *page, *new_page, *tmp;
1300 struct mem_cgroup *memcg;
1301 pgoff_t index, end = start + HPAGE_PMD_NR;
1302 LIST_HEAD(pagelist);
1303 struct radix_tree_iter iter;
1304 void **slot;
1305 int nr_none = 0, result = SCAN_SUCCEED;
1306
1307 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1308
1309 /* Only allocate from the target node */
1310 gfp = alloc_hugepage_khugepaged_gfpmask() |
1311 __GFP_OTHER_NODE | __GFP_THISNODE;
1312
1313 new_page = khugepaged_alloc_page(hpage, gfp, node);
1314 if (!new_page) {
1315 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1316 goto out;
1317 }
1318
1319 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
1320 result = SCAN_CGROUP_CHARGE_FAIL;
1321 goto out;
1322 }
1323
1324 new_page->index = start;
1325 new_page->mapping = mapping;
1326 __SetPageSwapBacked(new_page);
1327 __SetPageLocked(new_page);
1328 BUG_ON(!page_ref_freeze(new_page, 1));
1329
1330
1331 /*
1332 * At this point the new_page is 'frozen' (page_count() is zero), locked
1333 * and not up-to-date. It's safe to insert it into radix tree, because
1334 * nobody would be able to map it or use it in other way until we
1335 * unfreeze it.
1336 */
1337
1338 index = start;
1339 spin_lock_irq(&mapping->tree_lock);
1340 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1341 int n = min(iter.index, end) - index;
1342
1343 /*
1344 * Handle holes in the radix tree: charge it from shmem and
1345 * insert relevant subpage of new_page into the radix-tree.
1346 */
1347 if (n && !shmem_charge(mapping->host, n)) {
1348 result = SCAN_FAIL;
1349 break;
1350 }
1351 nr_none += n;
1352 for (; index < min(iter.index, end); index++) {
1353 radix_tree_insert(&mapping->page_tree, index,
1354 new_page + (index % HPAGE_PMD_NR));
1355 }
1356
1357 /* We are done. */
1358 if (index >= end)
1359 break;
1360
1361 page = radix_tree_deref_slot_protected(slot,
1362 &mapping->tree_lock);
1363 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) {
1364 spin_unlock_irq(&mapping->tree_lock);
1365 /* swap in or instantiate fallocated page */
1366 if (shmem_getpage(mapping->host, index, &page,
1367 SGP_NOHUGE)) {
1368 result = SCAN_FAIL;
1369 goto tree_unlocked;
1370 }
1371 spin_lock_irq(&mapping->tree_lock);
1372 } else if (trylock_page(page)) {
1373 get_page(page);
1374 } else {
1375 result = SCAN_PAGE_LOCK;
1376 break;
1377 }
1378
1379 /*
1380 * The page must be locked, so we can drop the tree_lock
1381 * without racing with truncate.
1382 */
1383 VM_BUG_ON_PAGE(!PageLocked(page), page);
1384 VM_BUG_ON_PAGE(!PageUptodate(page), page);
1385 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1386
1387 if (page_mapping(page) != mapping) {
1388 result = SCAN_TRUNCATED;
1389 goto out_unlock;
1390 }
1391 spin_unlock_irq(&mapping->tree_lock);
1392
1393 if (isolate_lru_page(page)) {
1394 result = SCAN_DEL_PAGE_LRU;
1395 goto out_isolate_failed;
1396 }
1397
1398 if (page_mapped(page))
1399 unmap_mapping_range(mapping, index << PAGE_SHIFT,
1400 PAGE_SIZE, 0);
1401
1402 spin_lock_irq(&mapping->tree_lock);
1403
1404 VM_BUG_ON_PAGE(page_mapped(page), page);
1405
1406 /*
1407 * The page is expected to have page_count() == 3:
1408 * - we hold a pin on it;
1409 * - one reference from radix tree;
1410 * - one from isolate_lru_page;
1411 */
1412 if (!page_ref_freeze(page, 3)) {
1413 result = SCAN_PAGE_COUNT;
1414 goto out_lru;
1415 }
1416
1417 /*
1418 * Add the page to the list to be able to undo the collapse if
1419 * something go wrong.
1420 */
1421 list_add_tail(&page->lru, &pagelist);
1422
1423 /* Finally, replace with the new page. */
1424 radix_tree_replace_slot(slot,
1425 new_page + (index % HPAGE_PMD_NR));
1426
1427 index++;
1428 continue;
1429 out_lru:
1430 spin_unlock_irq(&mapping->tree_lock);
1431 putback_lru_page(page);
1432 out_isolate_failed:
1433 unlock_page(page);
1434 put_page(page);
1435 goto tree_unlocked;
1436 out_unlock:
1437 unlock_page(page);
1438 put_page(page);
1439 break;
1440 }
1441
1442 /*
1443 * Handle hole in radix tree at the end of the range.
1444 * This code only triggers if there's nothing in radix tree
1445 * beyond 'end'.
1446 */
1447 if (result == SCAN_SUCCEED && index < end) {
1448 int n = end - index;
1449
1450 if (!shmem_charge(mapping->host, n)) {
1451 result = SCAN_FAIL;
1452 goto tree_locked;
1453 }
1454
1455 for (; index < end; index++) {
1456 radix_tree_insert(&mapping->page_tree, index,
1457 new_page + (index % HPAGE_PMD_NR));
1458 }
1459 nr_none += n;
1460 }
1461
1462 tree_locked:
1463 spin_unlock_irq(&mapping->tree_lock);
1464 tree_unlocked:
1465
1466 if (result == SCAN_SUCCEED) {
1467 unsigned long flags;
1468 struct zone *zone = page_zone(new_page);
1469
1470 /*
1471 * Replacing old pages with new one has succeed, now we need to
1472 * copy the content and free old pages.
1473 */
1474 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
1475 copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
1476 page);
1477 list_del(&page->lru);
1478 unlock_page(page);
1479 page_ref_unfreeze(page, 1);
1480 page->mapping = NULL;
1481 ClearPageActive(page);
1482 ClearPageUnevictable(page);
1483 put_page(page);
1484 }
1485
1486 local_irq_save(flags);
1487 __inc_node_page_state(new_page, NR_SHMEM_THPS);
1488 if (nr_none) {
1489 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
1490 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
1491 }
1492 local_irq_restore(flags);
1493
1494 /*
1495 * Remove pte page tables, so we can re-faulti
1496 * the page as huge.
1497 */
1498 retract_page_tables(mapping, start);
1499
1500 /* Everything is ready, let's unfreeze the new_page */
1501 set_page_dirty(new_page);
1502 SetPageUptodate(new_page);
1503 page_ref_unfreeze(new_page, HPAGE_PMD_NR);
1504 mem_cgroup_commit_charge(new_page, memcg, false, true);
1505 lru_cache_add_anon(new_page);
1506 unlock_page(new_page);
1507
1508 *hpage = NULL;
1509 } else {
1510 /* Something went wrong: rollback changes to the radix-tree */
1511 shmem_uncharge(mapping->host, nr_none);
1512 spin_lock_irq(&mapping->tree_lock);
1513 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
1514 start) {
1515 if (iter.index >= end)
1516 break;
1517 page = list_first_entry_or_null(&pagelist,
1518 struct page, lru);
1519 if (!page || iter.index < page->index) {
1520 if (!nr_none)
1521 break;
1522 /* Put holes back where they were */
1523 radix_tree_replace_slot(slot, NULL);
1524 nr_none--;
1525 continue;
1526 }
1527
1528 VM_BUG_ON_PAGE(page->index != iter.index, page);
1529
1530 /* Unfreeze the page. */
1531 list_del(&page->lru);
1532 page_ref_unfreeze(page, 2);
1533 radix_tree_replace_slot(slot, page);
1534 spin_unlock_irq(&mapping->tree_lock);
1535 putback_lru_page(page);
1536 unlock_page(page);
1537 spin_lock_irq(&mapping->tree_lock);
1538 }
1539 VM_BUG_ON(nr_none);
1540 spin_unlock_irq(&mapping->tree_lock);
1541
1542 /* Unfreeze new_page, caller would take care about freeing it */
1543 page_ref_unfreeze(new_page, 1);
1544 mem_cgroup_cancel_charge(new_page, memcg, true);
1545 unlock_page(new_page);
1546 new_page->mapping = NULL;
1547 }
1548 out:
1549 VM_BUG_ON(!list_empty(&pagelist));
1550 /* TODO: tracepoints */
1551 }
1552
1553 static void khugepaged_scan_shmem(struct mm_struct *mm,
1554 struct address_space *mapping,
1555 pgoff_t start, struct page **hpage)
1556 {
1557 struct page *page = NULL;
1558 struct radix_tree_iter iter;
1559 void **slot;
1560 int present, swap;
1561 int node = NUMA_NO_NODE;
1562 int result = SCAN_SUCCEED;
1563
1564 present = 0;
1565 swap = 0;
1566 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1567 rcu_read_lock();
1568 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1569 if (iter.index >= start + HPAGE_PMD_NR)
1570 break;
1571
1572 page = radix_tree_deref_slot(slot);
1573 if (radix_tree_deref_retry(page)) {
1574 slot = radix_tree_iter_retry(&iter);
1575 continue;
1576 }
1577
1578 if (radix_tree_exception(page)) {
1579 if (++swap > khugepaged_max_ptes_swap) {
1580 result = SCAN_EXCEED_SWAP_PTE;
1581 break;
1582 }
1583 continue;
1584 }
1585
1586 if (PageTransCompound(page)) {
1587 result = SCAN_PAGE_COMPOUND;
1588 break;
1589 }
1590
1591 node = page_to_nid(page);
1592 if (khugepaged_scan_abort(node)) {
1593 result = SCAN_SCAN_ABORT;
1594 break;
1595 }
1596 khugepaged_node_load[node]++;
1597
1598 if (!PageLRU(page)) {
1599 result = SCAN_PAGE_LRU;
1600 break;
1601 }
1602
1603 if (page_count(page) != 1 + page_mapcount(page)) {
1604 result = SCAN_PAGE_COUNT;
1605 break;
1606 }
1607
1608 /*
1609 * We probably should check if the page is referenced here, but
1610 * nobody would transfer pte_young() to PageReferenced() for us.
1611 * And rmap walk here is just too costly...
1612 */
1613
1614 present++;
1615
1616 if (need_resched()) {
1617 cond_resched_rcu();
1618 slot = radix_tree_iter_next(&iter);
1619 }
1620 }
1621 rcu_read_unlock();
1622
1623 if (result == SCAN_SUCCEED) {
1624 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
1625 result = SCAN_EXCEED_NONE_PTE;
1626 } else {
1627 node = khugepaged_find_target_node();
1628 collapse_shmem(mm, mapping, start, hpage, node);
1629 }
1630 }
1631
1632 /* TODO: tracepoints */
1633 }
1634 #else
1635 static void khugepaged_scan_shmem(struct mm_struct *mm,
1636 struct address_space *mapping,
1637 pgoff_t start, struct page **hpage)
1638 {
1639 BUILD_BUG();
1640 }
1641 #endif
1642
1643 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1644 struct page **hpage)
1645 __releases(&khugepaged_mm_lock)
1646 __acquires(&khugepaged_mm_lock)
1647 {
1648 struct mm_slot *mm_slot;
1649 struct mm_struct *mm;
1650 struct vm_area_struct *vma;
1651 int progress = 0;
1652
1653 VM_BUG_ON(!pages);
1654 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1655
1656 if (khugepaged_scan.mm_slot)
1657 mm_slot = khugepaged_scan.mm_slot;
1658 else {
1659 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1660 struct mm_slot, mm_node);
1661 khugepaged_scan.address = 0;
1662 khugepaged_scan.mm_slot = mm_slot;
1663 }
1664 spin_unlock(&khugepaged_mm_lock);
1665
1666 mm = mm_slot->mm;
1667 down_read(&mm->mmap_sem);
1668 if (unlikely(khugepaged_test_exit(mm)))
1669 vma = NULL;
1670 else
1671 vma = find_vma(mm, khugepaged_scan.address);
1672
1673 progress++;
1674 for (; vma; vma = vma->vm_next) {
1675 unsigned long hstart, hend;
1676
1677 cond_resched();
1678 if (unlikely(khugepaged_test_exit(mm))) {
1679 progress++;
1680 break;
1681 }
1682 if (!hugepage_vma_check(vma)) {
1683 skip:
1684 progress++;
1685 continue;
1686 }
1687 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1688 hend = vma->vm_end & HPAGE_PMD_MASK;
1689 if (hstart >= hend)
1690 goto skip;
1691 if (khugepaged_scan.address > hend)
1692 goto skip;
1693 if (khugepaged_scan.address < hstart)
1694 khugepaged_scan.address = hstart;
1695 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1696
1697 while (khugepaged_scan.address < hend) {
1698 int ret;
1699 cond_resched();
1700 if (unlikely(khugepaged_test_exit(mm)))
1701 goto breakouterloop;
1702
1703 VM_BUG_ON(khugepaged_scan.address < hstart ||
1704 khugepaged_scan.address + HPAGE_PMD_SIZE >
1705 hend);
1706 if (shmem_file(vma->vm_file)) {
1707 struct file *file;
1708 pgoff_t pgoff = linear_page_index(vma,
1709 khugepaged_scan.address);
1710 if (!shmem_huge_enabled(vma))
1711 goto skip;
1712 file = get_file(vma->vm_file);
1713 up_read(&mm->mmap_sem);
1714 ret = 1;
1715 khugepaged_scan_shmem(mm, file->f_mapping,
1716 pgoff, hpage);
1717 fput(file);
1718 } else {
1719 ret = khugepaged_scan_pmd(mm, vma,
1720 khugepaged_scan.address,
1721 hpage);
1722 }
1723 /* move to next address */
1724 khugepaged_scan.address += HPAGE_PMD_SIZE;
1725 progress += HPAGE_PMD_NR;
1726 if (ret)
1727 /* we released mmap_sem so break loop */
1728 goto breakouterloop_mmap_sem;
1729 if (progress >= pages)
1730 goto breakouterloop;
1731 }
1732 }
1733 breakouterloop:
1734 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1735 breakouterloop_mmap_sem:
1736
1737 spin_lock(&khugepaged_mm_lock);
1738 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1739 /*
1740 * Release the current mm_slot if this mm is about to die, or
1741 * if we scanned all vmas of this mm.
1742 */
1743 if (khugepaged_test_exit(mm) || !vma) {
1744 /*
1745 * Make sure that if mm_users is reaching zero while
1746 * khugepaged runs here, khugepaged_exit will find
1747 * mm_slot not pointing to the exiting mm.
1748 */
1749 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1750 khugepaged_scan.mm_slot = list_entry(
1751 mm_slot->mm_node.next,
1752 struct mm_slot, mm_node);
1753 khugepaged_scan.address = 0;
1754 } else {
1755 khugepaged_scan.mm_slot = NULL;
1756 khugepaged_full_scans++;
1757 }
1758
1759 collect_mm_slot(mm_slot);
1760 }
1761
1762 return progress;
1763 }
1764
1765 static int khugepaged_has_work(void)
1766 {
1767 return !list_empty(&khugepaged_scan.mm_head) &&
1768 khugepaged_enabled();
1769 }
1770
1771 static int khugepaged_wait_event(void)
1772 {
1773 return !list_empty(&khugepaged_scan.mm_head) ||
1774 kthread_should_stop();
1775 }
1776
1777 static void khugepaged_do_scan(void)
1778 {
1779 struct page *hpage = NULL;
1780 unsigned int progress = 0, pass_through_head = 0;
1781 unsigned int pages = khugepaged_pages_to_scan;
1782 bool wait = true;
1783
1784 barrier(); /* write khugepaged_pages_to_scan to local stack */
1785
1786 while (progress < pages) {
1787 if (!khugepaged_prealloc_page(&hpage, &wait))
1788 break;
1789
1790 cond_resched();
1791
1792 if (unlikely(kthread_should_stop() || try_to_freeze()))
1793 break;
1794
1795 spin_lock(&khugepaged_mm_lock);
1796 if (!khugepaged_scan.mm_slot)
1797 pass_through_head++;
1798 if (khugepaged_has_work() &&
1799 pass_through_head < 2)
1800 progress += khugepaged_scan_mm_slot(pages - progress,
1801 &hpage);
1802 else
1803 progress = pages;
1804 spin_unlock(&khugepaged_mm_lock);
1805 }
1806
1807 if (!IS_ERR_OR_NULL(hpage))
1808 put_page(hpage);
1809 }
1810
1811 static bool khugepaged_should_wakeup(void)
1812 {
1813 return kthread_should_stop() ||
1814 time_after_eq(jiffies, khugepaged_sleep_expire);
1815 }
1816
1817 static void khugepaged_wait_work(void)
1818 {
1819 if (khugepaged_has_work()) {
1820 const unsigned long scan_sleep_jiffies =
1821 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
1822
1823 if (!scan_sleep_jiffies)
1824 return;
1825
1826 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
1827 wait_event_freezable_timeout(khugepaged_wait,
1828 khugepaged_should_wakeup(),
1829 scan_sleep_jiffies);
1830 return;
1831 }
1832
1833 if (khugepaged_enabled())
1834 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
1835 }
1836
1837 static int khugepaged(void *none)
1838 {
1839 struct mm_slot *mm_slot;
1840
1841 set_freezable();
1842 set_user_nice(current, MAX_NICE);
1843
1844 while (!kthread_should_stop()) {
1845 khugepaged_do_scan();
1846 khugepaged_wait_work();
1847 }
1848
1849 spin_lock(&khugepaged_mm_lock);
1850 mm_slot = khugepaged_scan.mm_slot;
1851 khugepaged_scan.mm_slot = NULL;
1852 if (mm_slot)
1853 collect_mm_slot(mm_slot);
1854 spin_unlock(&khugepaged_mm_lock);
1855 return 0;
1856 }
1857
1858 static void set_recommended_min_free_kbytes(void)
1859 {
1860 struct zone *zone;
1861 int nr_zones = 0;
1862 unsigned long recommended_min;
1863
1864 for_each_populated_zone(zone)
1865 nr_zones++;
1866
1867 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1868 recommended_min = pageblock_nr_pages * nr_zones * 2;
1869
1870 /*
1871 * Make sure that on average at least two pageblocks are almost free
1872 * of another type, one for a migratetype to fall back to and a
1873 * second to avoid subsequent fallbacks of other types There are 3
1874 * MIGRATE_TYPES we care about.
1875 */
1876 recommended_min += pageblock_nr_pages * nr_zones *
1877 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
1878
1879 /* don't ever allow to reserve more than 5% of the lowmem */
1880 recommended_min = min(recommended_min,
1881 (unsigned long) nr_free_buffer_pages() / 20);
1882 recommended_min <<= (PAGE_SHIFT-10);
1883
1884 if (recommended_min > min_free_kbytes) {
1885 if (user_min_free_kbytes >= 0)
1886 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1887 min_free_kbytes, recommended_min);
1888
1889 min_free_kbytes = recommended_min;
1890 }
1891 setup_per_zone_wmarks();
1892 }
1893
1894 int start_stop_khugepaged(void)
1895 {
1896 static struct task_struct *khugepaged_thread __read_mostly;
1897 static DEFINE_MUTEX(khugepaged_mutex);
1898 int err = 0;
1899
1900 mutex_lock(&khugepaged_mutex);
1901 if (khugepaged_enabled()) {
1902 if (!khugepaged_thread)
1903 khugepaged_thread = kthread_run(khugepaged, NULL,
1904 "khugepaged");
1905 if (IS_ERR(khugepaged_thread)) {
1906 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1907 err = PTR_ERR(khugepaged_thread);
1908 khugepaged_thread = NULL;
1909 goto fail;
1910 }
1911
1912 if (!list_empty(&khugepaged_scan.mm_head))
1913 wake_up_interruptible(&khugepaged_wait);
1914
1915 set_recommended_min_free_kbytes();
1916 } else if (khugepaged_thread) {
1917 kthread_stop(khugepaged_thread);
1918 khugepaged_thread = NULL;
1919 }
1920 fail:
1921 mutex_unlock(&khugepaged_mutex);
1922 return err;
1923 }