blob: c01f177a1120a4802fedc63ffc1d9665ea09ec0b [file] [log] [blame]
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
2
3#include <linux/mm.h>
4#include <linux/sched.h>
Ingo Molnar6e84f312017-02-08 18:51:29 +01005#include <linux/sched/mm.h>
Ingo Molnarf7ccbae2017-02-08 18:51:30 +01006#include <linux/sched/coredump.h>
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07007#include <linux/mmu_notifier.h>
8#include <linux/rmap.h>
9#include <linux/swap.h>
10#include <linux/mm_inline.h>
11#include <linux/kthread.h>
12#include <linux/khugepaged.h>
13#include <linux/freezer.h>
14#include <linux/mman.h>
15#include <linux/hashtable.h>
16#include <linux/userfaultfd_k.h>
17#include <linux/page_idle.h>
18#include <linux/swapops.h>
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -070019#include <linux/shmem_fs.h>
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -070020
21#include <asm/tlb.h>
22#include <asm/pgalloc.h>
23#include "internal.h"
24
25enum scan_result {
26 SCAN_FAIL,
27 SCAN_SUCCEED,
28 SCAN_PMD_NULL,
29 SCAN_EXCEED_NONE_PTE,
30 SCAN_PTE_NON_PRESENT,
31 SCAN_PAGE_RO,
Ebru Akagunduz0db501f2016-07-26 15:26:46 -070032 SCAN_LACK_REFERENCED_PAGE,
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -070033 SCAN_PAGE_NULL,
34 SCAN_SCAN_ABORT,
35 SCAN_PAGE_COUNT,
36 SCAN_PAGE_LRU,
37 SCAN_PAGE_LOCK,
38 SCAN_PAGE_ANON,
39 SCAN_PAGE_COMPOUND,
40 SCAN_ANY_PROCESS,
41 SCAN_VMA_NULL,
42 SCAN_VMA_CHECK,
43 SCAN_ADDRESS_RANGE,
44 SCAN_SWAP_CACHE_PAGE,
45 SCAN_DEL_PAGE_LRU,
46 SCAN_ALLOC_HUGE_PAGE_FAIL,
47 SCAN_CGROUP_CHARGE_FAIL,
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -070048 SCAN_EXCEED_SWAP_PTE,
49 SCAN_TRUNCATED,
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -070050};
51
52#define CREATE_TRACE_POINTS
53#include <trace/events/huge_memory.h>
54
55/* default scan 8*512 pte (or vmas) every 30 second */
56static unsigned int khugepaged_pages_to_scan __read_mostly;
57static unsigned int khugepaged_pages_collapsed;
58static unsigned int khugepaged_full_scans;
59static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
60/* during fragmentation poll the hugepage allocator once every minute */
61static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
62static unsigned long khugepaged_sleep_expire;
63static DEFINE_SPINLOCK(khugepaged_mm_lock);
64static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
65/*
66 * default collapse hugepages if there is at least one pte mapped like
67 * it would have happened if the vma was large enough during page
68 * fault.
69 */
70static unsigned int khugepaged_max_ptes_none __read_mostly;
71static unsigned int khugepaged_max_ptes_swap __read_mostly;
72
73#define MM_SLOTS_HASH_BITS 10
74static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
75
76static struct kmem_cache *mm_slot_cache __read_mostly;
77
78/**
79 * struct mm_slot - hash lookup from mm to mm_slot
80 * @hash: hash collision list
81 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
82 * @mm: the mm that this information is valid for
83 */
84struct mm_slot {
85 struct hlist_node hash;
86 struct list_head mm_node;
87 struct mm_struct *mm;
88};
89
90/**
91 * struct khugepaged_scan - cursor for scanning
92 * @mm_head: the head of the mm list to scan
93 * @mm_slot: the current mm_slot we are scanning
94 * @address: the next address inside that to be scanned
95 *
96 * There is only the one khugepaged_scan instance of this cursor structure.
97 */
98struct khugepaged_scan {
99 struct list_head mm_head;
100 struct mm_slot *mm_slot;
101 unsigned long address;
102};
103
104static struct khugepaged_scan khugepaged_scan = {
105 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
106};
107
Jérémy Lefauree1465d12016-11-30 15:54:02 -0800108#ifdef CONFIG_SYSFS
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700109static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
110 struct kobj_attribute *attr,
111 char *buf)
112{
113 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
114}
115
116static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
117 struct kobj_attribute *attr,
118 const char *buf, size_t count)
119{
120 unsigned long msecs;
121 int err;
122
123 err = kstrtoul(buf, 10, &msecs);
124 if (err || msecs > UINT_MAX)
125 return -EINVAL;
126
127 khugepaged_scan_sleep_millisecs = msecs;
128 khugepaged_sleep_expire = 0;
129 wake_up_interruptible(&khugepaged_wait);
130
131 return count;
132}
133static struct kobj_attribute scan_sleep_millisecs_attr =
134 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
135 scan_sleep_millisecs_store);
136
137static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
138 struct kobj_attribute *attr,
139 char *buf)
140{
141 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
142}
143
144static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
145 struct kobj_attribute *attr,
146 const char *buf, size_t count)
147{
148 unsigned long msecs;
149 int err;
150
151 err = kstrtoul(buf, 10, &msecs);
152 if (err || msecs > UINT_MAX)
153 return -EINVAL;
154
155 khugepaged_alloc_sleep_millisecs = msecs;
156 khugepaged_sleep_expire = 0;
157 wake_up_interruptible(&khugepaged_wait);
158
159 return count;
160}
161static struct kobj_attribute alloc_sleep_millisecs_attr =
162 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
163 alloc_sleep_millisecs_store);
164
165static ssize_t pages_to_scan_show(struct kobject *kobj,
166 struct kobj_attribute *attr,
167 char *buf)
168{
169 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
170}
171static ssize_t pages_to_scan_store(struct kobject *kobj,
172 struct kobj_attribute *attr,
173 const char *buf, size_t count)
174{
175 int err;
176 unsigned long pages;
177
178 err = kstrtoul(buf, 10, &pages);
179 if (err || !pages || pages > UINT_MAX)
180 return -EINVAL;
181
182 khugepaged_pages_to_scan = pages;
183
184 return count;
185}
186static struct kobj_attribute pages_to_scan_attr =
187 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
188 pages_to_scan_store);
189
190static ssize_t pages_collapsed_show(struct kobject *kobj,
191 struct kobj_attribute *attr,
192 char *buf)
193{
194 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
195}
196static struct kobj_attribute pages_collapsed_attr =
197 __ATTR_RO(pages_collapsed);
198
199static ssize_t full_scans_show(struct kobject *kobj,
200 struct kobj_attribute *attr,
201 char *buf)
202{
203 return sprintf(buf, "%u\n", khugepaged_full_scans);
204}
205static struct kobj_attribute full_scans_attr =
206 __ATTR_RO(full_scans);
207
208static ssize_t khugepaged_defrag_show(struct kobject *kobj,
209 struct kobj_attribute *attr, char *buf)
210{
211 return single_hugepage_flag_show(kobj, attr, buf,
212 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
213}
214static ssize_t khugepaged_defrag_store(struct kobject *kobj,
215 struct kobj_attribute *attr,
216 const char *buf, size_t count)
217{
218 return single_hugepage_flag_store(kobj, attr, buf, count,
219 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
220}
221static struct kobj_attribute khugepaged_defrag_attr =
222 __ATTR(defrag, 0644, khugepaged_defrag_show,
223 khugepaged_defrag_store);
224
225/*
226 * max_ptes_none controls if khugepaged should collapse hugepages over
227 * any unmapped ptes in turn potentially increasing the memory
228 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
229 * reduce the available free memory in the system as it
230 * runs. Increasing max_ptes_none will instead potentially reduce the
231 * free memory in the system during the khugepaged scan.
232 */
233static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
234 struct kobj_attribute *attr,
235 char *buf)
236{
237 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
238}
239static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
240 struct kobj_attribute *attr,
241 const char *buf, size_t count)
242{
243 int err;
244 unsigned long max_ptes_none;
245
246 err = kstrtoul(buf, 10, &max_ptes_none);
247 if (err || max_ptes_none > HPAGE_PMD_NR-1)
248 return -EINVAL;
249
250 khugepaged_max_ptes_none = max_ptes_none;
251
252 return count;
253}
254static struct kobj_attribute khugepaged_max_ptes_none_attr =
255 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
256 khugepaged_max_ptes_none_store);
257
258static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
259 struct kobj_attribute *attr,
260 char *buf)
261{
262 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
263}
264
265static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
266 struct kobj_attribute *attr,
267 const char *buf, size_t count)
268{
269 int err;
270 unsigned long max_ptes_swap;
271
272 err = kstrtoul(buf, 10, &max_ptes_swap);
273 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
274 return -EINVAL;
275
276 khugepaged_max_ptes_swap = max_ptes_swap;
277
278 return count;
279}
280
281static struct kobj_attribute khugepaged_max_ptes_swap_attr =
282 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
283 khugepaged_max_ptes_swap_store);
284
285static struct attribute *khugepaged_attr[] = {
286 &khugepaged_defrag_attr.attr,
287 &khugepaged_max_ptes_none_attr.attr,
288 &pages_to_scan_attr.attr,
289 &pages_collapsed_attr.attr,
290 &full_scans_attr.attr,
291 &scan_sleep_millisecs_attr.attr,
292 &alloc_sleep_millisecs_attr.attr,
293 &khugepaged_max_ptes_swap_attr.attr,
294 NULL,
295};
296
297struct attribute_group khugepaged_attr_group = {
298 .attrs = khugepaged_attr,
299 .name = "khugepaged",
300};
Jérémy Lefauree1465d12016-11-30 15:54:02 -0800301#endif /* CONFIG_SYSFS */
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700302
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -0700303#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700304
305int hugepage_madvise(struct vm_area_struct *vma,
306 unsigned long *vm_flags, int advice)
307{
308 switch (advice) {
309 case MADV_HUGEPAGE:
310#ifdef CONFIG_S390
311 /*
312 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
313 * can't handle this properly after s390_enable_sie, so we simply
314 * ignore the madvise to prevent qemu from causing a SIGSEGV.
315 */
316 if (mm_has_pgste(vma->vm_mm))
317 return 0;
318#endif
319 *vm_flags &= ~VM_NOHUGEPAGE;
320 *vm_flags |= VM_HUGEPAGE;
321 /*
322 * If the vma become good for khugepaged to scan,
323 * register it here without waiting a page fault that
324 * may not happen any time soon.
325 */
326 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
327 khugepaged_enter_vma_merge(vma, *vm_flags))
328 return -ENOMEM;
329 break;
330 case MADV_NOHUGEPAGE:
331 *vm_flags &= ~VM_HUGEPAGE;
332 *vm_flags |= VM_NOHUGEPAGE;
333 /*
334 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
335 * this vma even if we leave the mm registered in khugepaged if
336 * it got registered before VM_NOHUGEPAGE was set.
337 */
338 break;
339 }
340
341 return 0;
342}
343
344int __init khugepaged_init(void)
345{
346 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
347 sizeof(struct mm_slot),
348 __alignof__(struct mm_slot), 0, NULL);
349 if (!mm_slot_cache)
350 return -ENOMEM;
351
352 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
353 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
354 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
355
356 return 0;
357}
358
359void __init khugepaged_destroy(void)
360{
361 kmem_cache_destroy(mm_slot_cache);
362}
363
364static inline struct mm_slot *alloc_mm_slot(void)
365{
366 if (!mm_slot_cache) /* initialization failed */
367 return NULL;
368 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
369}
370
371static inline void free_mm_slot(struct mm_slot *mm_slot)
372{
373 kmem_cache_free(mm_slot_cache, mm_slot);
374}
375
376static struct mm_slot *get_mm_slot(struct mm_struct *mm)
377{
378 struct mm_slot *mm_slot;
379
380 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
381 if (mm == mm_slot->mm)
382 return mm_slot;
383
384 return NULL;
385}
386
387static void insert_to_mm_slots_hash(struct mm_struct *mm,
388 struct mm_slot *mm_slot)
389{
390 mm_slot->mm = mm;
391 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
392}
393
394static inline int khugepaged_test_exit(struct mm_struct *mm)
395{
396 return atomic_read(&mm->mm_users) == 0;
397}
398
399int __khugepaged_enter(struct mm_struct *mm)
400{
401 struct mm_slot *mm_slot;
402 int wakeup;
403
404 mm_slot = alloc_mm_slot();
405 if (!mm_slot)
406 return -ENOMEM;
407
408 /* __khugepaged_exit() must not run from under us */
409 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
410 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
411 free_mm_slot(mm_slot);
412 return 0;
413 }
414
415 spin_lock(&khugepaged_mm_lock);
416 insert_to_mm_slots_hash(mm, mm_slot);
417 /*
418 * Insert just behind the scanning cursor, to let the area settle
419 * down a little.
420 */
421 wakeup = list_empty(&khugepaged_scan.mm_head);
422 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
423 spin_unlock(&khugepaged_mm_lock);
424
Vegard Nossumf1f10072017-02-27 14:30:07 -0800425 mmgrab(mm);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700426 if (wakeup)
427 wake_up_interruptible(&khugepaged_wait);
428
429 return 0;
430}
431
432int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
433 unsigned long vm_flags)
434{
435 unsigned long hstart, hend;
436 if (!vma->anon_vma)
437 /*
438 * Not yet faulted in so we will register later in the
439 * page fault if needed.
440 */
441 return 0;
442 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
443 /* khugepaged not yet working on file or special mappings */
444 return 0;
445 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
446 hend = vma->vm_end & HPAGE_PMD_MASK;
447 if (hstart < hend)
448 return khugepaged_enter(vma, vm_flags);
449 return 0;
450}
451
452void __khugepaged_exit(struct mm_struct *mm)
453{
454 struct mm_slot *mm_slot;
455 int free = 0;
456
457 spin_lock(&khugepaged_mm_lock);
458 mm_slot = get_mm_slot(mm);
459 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
460 hash_del(&mm_slot->hash);
461 list_del(&mm_slot->mm_node);
462 free = 1;
463 }
464 spin_unlock(&khugepaged_mm_lock);
465
466 if (free) {
467 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
468 free_mm_slot(mm_slot);
469 mmdrop(mm);
470 } else if (mm_slot) {
471 /*
472 * This is required to serialize against
473 * khugepaged_test_exit() (which is guaranteed to run
474 * under mmap sem read mode). Stop here (after we
475 * return all pagetables will be destroyed) until
476 * khugepaged has finished working on the pagetables
477 * under the mmap_sem.
478 */
479 down_write(&mm->mmap_sem);
480 up_write(&mm->mmap_sem);
481 }
482}
483
484static void release_pte_page(struct page *page)
485{
Shaohua Lid44d3632017-05-03 14:52:26 -0700486 dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700487 unlock_page(page);
488 putback_lru_page(page);
489}
490
491static void release_pte_pages(pte_t *pte, pte_t *_pte)
492{
493 while (--_pte >= pte) {
494 pte_t pteval = *_pte;
495 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
496 release_pte_page(pte_page(pteval));
497 }
498}
499
500static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
501 unsigned long address,
502 pte_t *pte)
503{
504 struct page *page = NULL;
505 pte_t *_pte;
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700506 int none_or_zero = 0, result = 0, referenced = 0;
507 bool writable = false;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700508
509 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
510 _pte++, address += PAGE_SIZE) {
511 pte_t pteval = *_pte;
512 if (pte_none(pteval) || (pte_present(pteval) &&
513 is_zero_pfn(pte_pfn(pteval)))) {
514 if (!userfaultfd_armed(vma) &&
515 ++none_or_zero <= khugepaged_max_ptes_none) {
516 continue;
517 } else {
518 result = SCAN_EXCEED_NONE_PTE;
519 goto out;
520 }
521 }
522 if (!pte_present(pteval)) {
523 result = SCAN_PTE_NON_PRESENT;
524 goto out;
525 }
526 page = vm_normal_page(vma, address, pteval);
527 if (unlikely(!page)) {
528 result = SCAN_PAGE_NULL;
529 goto out;
530 }
531
532 VM_BUG_ON_PAGE(PageCompound(page), page);
533 VM_BUG_ON_PAGE(!PageAnon(page), page);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700534
535 /*
536 * We can do it before isolate_lru_page because the
537 * page can't be freed from under us. NOTE: PG_lock
538 * is needed to serialize against split_huge_page
539 * when invoked from the VM.
540 */
541 if (!trylock_page(page)) {
542 result = SCAN_PAGE_LOCK;
543 goto out;
544 }
545
546 /*
547 * cannot use mapcount: can't collapse if there's a gup pin.
548 * The page must only be referenced by the scanned process
549 * and page swap cache.
550 */
Minchan Kim2948be52017-05-03 14:53:35 -0700551 if (page_count(page) != 1 + PageSwapCache(page)) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700552 unlock_page(page);
553 result = SCAN_PAGE_COUNT;
554 goto out;
555 }
556 if (pte_write(pteval)) {
557 writable = true;
558 } else {
559 if (PageSwapCache(page) &&
560 !reuse_swap_page(page, NULL)) {
561 unlock_page(page);
562 result = SCAN_SWAP_CACHE_PAGE;
563 goto out;
564 }
565 /*
566 * Page is not in the swap cache. It can be collapsed
567 * into a THP.
568 */
569 }
570
571 /*
572 * Isolate the page to avoid collapsing an hugepage
573 * currently in use by the VM.
574 */
575 if (isolate_lru_page(page)) {
576 unlock_page(page);
577 result = SCAN_DEL_PAGE_LRU;
578 goto out;
579 }
Shaohua Lid44d3632017-05-03 14:52:26 -0700580 inc_node_page_state(page,
581 NR_ISOLATED_ANON + page_is_file_cache(page));
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700582 VM_BUG_ON_PAGE(!PageLocked(page), page);
583 VM_BUG_ON_PAGE(PageLRU(page), page);
584
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700585 /* There should be enough young pte to collapse the page */
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700586 if (pte_young(pteval) ||
587 page_is_young(page) || PageReferenced(page) ||
588 mmu_notifier_test_young(vma->vm_mm, address))
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700589 referenced++;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700590 }
591 if (likely(writable)) {
592 if (likely(referenced)) {
593 result = SCAN_SUCCEED;
594 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
595 referenced, writable, result);
596 return 1;
597 }
598 } else {
599 result = SCAN_PAGE_RO;
600 }
601
602out:
603 release_pte_pages(pte, _pte);
604 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
605 referenced, writable, result);
606 return 0;
607}
608
609static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
610 struct vm_area_struct *vma,
611 unsigned long address,
612 spinlock_t *ptl)
613{
614 pte_t *_pte;
David Rientjes338a16b2017-05-12 15:47:03 -0700615 for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
616 _pte++, page++, address += PAGE_SIZE) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700617 pte_t pteval = *_pte;
618 struct page *src_page;
619
620 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
621 clear_user_highpage(page, address);
622 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
623 if (is_zero_pfn(pte_pfn(pteval))) {
624 /*
625 * ptl mostly unnecessary.
626 */
627 spin_lock(ptl);
628 /*
629 * paravirt calls inside pte_clear here are
630 * superfluous.
631 */
632 pte_clear(vma->vm_mm, address, _pte);
633 spin_unlock(ptl);
634 }
635 } else {
636 src_page = pte_page(pteval);
637 copy_user_highpage(page, src_page, address, vma);
638 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
639 release_pte_page(src_page);
640 /*
641 * ptl mostly unnecessary, but preempt has to
642 * be disabled to update the per-cpu stats
643 * inside page_remove_rmap().
644 */
645 spin_lock(ptl);
646 /*
647 * paravirt calls inside pte_clear here are
648 * superfluous.
649 */
650 pte_clear(vma->vm_mm, address, _pte);
651 page_remove_rmap(src_page, false);
652 spin_unlock(ptl);
653 free_page_and_swap_cache(src_page);
654 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700655 }
656}
657
658static 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
668static int khugepaged_node_load[MAX_NUMNODES];
669
670static bool khugepaged_scan_abort(int nid)
671{
672 int i;
673
674 /*
Mel Gormana5f5f912016-07-28 15:46:32 -0700675 * If node_reclaim_mode is disabled, then no extra effort is made to
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700676 * allocate memory locally.
677 */
Mel Gormana5f5f912016-07-28 15:46:32 -0700678 if (!node_reclaim_mode)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700679 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 */
695static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
696{
Vlastimil Babka25160352016-07-28 15:49:25 -0700697 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700698}
699
700#ifdef CONFIG_NUMA
701static 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
726static 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
743static struct page *
Kirill A. Shutemov988ddb72016-07-26 15:26:26 -0700744khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700745{
746 VM_BUG_ON_PAGE(*hpage, *hpage);
747
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700748 *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
760static int khugepaged_find_target_node(void)
761{
762 return 0;
763}
764
765static 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
776static 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
796static 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
807static struct page *
Kirill A. Shutemov988ddb72016-07-26 15:26:26 -0700808khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700809{
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700810 VM_BUG_ON(!*hpage);
811
812 return *hpage;
813}
814#endif
815
816static bool hugepage_vma_check(struct vm_area_struct *vma)
817{
818 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
Michal Hocko18600332017-07-10 15:48:02 -0700819 (vma->vm_flags & VM_NOHUGEPAGE) ||
820 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700821 return false;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -0700822 if (shmem_file(vma->vm_file)) {
Kirill A. Shutemove496cf32016-07-26 15:26:35 -0700823 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
824 return false;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -0700825 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
826 HPAGE_PMD_NR);
827 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700828 if (!vma->anon_vma || vma->vm_ops)
829 return false;
830 if (is_vma_temporary_stack(vma))
831 return false;
832 return !(vma->vm_flags & VM_NO_KHUGEPAGED);
833}
834
835/*
836 * If mmap_sem temporarily dropped, revalidate vma
837 * before taking mmap_sem.
838 * Return 0 if succeeds, otherwise return none-zero
839 * value (scan code).
840 */
841
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700842static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
843 struct vm_area_struct **vmap)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700844{
845 struct vm_area_struct *vma;
846 unsigned long hstart, hend;
847
848 if (unlikely(khugepaged_test_exit(mm)))
849 return SCAN_ANY_PROCESS;
850
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700851 *vmap = vma = find_vma(mm, address);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700852 if (!vma)
853 return SCAN_VMA_NULL;
854
855 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
856 hend = vma->vm_end & HPAGE_PMD_MASK;
857 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
858 return SCAN_ADDRESS_RANGE;
859 if (!hugepage_vma_check(vma))
860 return SCAN_VMA_CHECK;
861 return 0;
862}
863
864/*
865 * Bring missing pages in from swap, to complete THP collapse.
866 * Only done if khugepaged_scan_pmd believes it is worthwhile.
867 *
868 * Called and returns without pte mapped or spinlocks held,
869 * but with mmap_sem held to protect against vma changes.
870 */
871
872static bool __collapse_huge_page_swapin(struct mm_struct *mm,
873 struct vm_area_struct *vma,
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700874 unsigned long address, pmd_t *pmd,
875 int referenced)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700876{
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700877 int swapped_in = 0, ret = 0;
Jan Kara82b0f8c2016-12-14 15:06:58 -0800878 struct vm_fault vmf = {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700879 .vma = vma,
880 .address = address,
881 .flags = FAULT_FLAG_ALLOW_RETRY,
882 .pmd = pmd,
Jan Kara0721ec82016-12-14 15:07:04 -0800883 .pgoff = linear_page_index(vma, address),
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700884 };
885
Ebru Akagunduz982785c2016-09-19 14:44:04 -0700886 /* we only decide to swapin, if there is enough young ptes */
887 if (referenced < HPAGE_PMD_NR/2) {
888 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
889 return false;
890 }
Jan Kara82b0f8c2016-12-14 15:06:58 -0800891 vmf.pte = pte_offset_map(pmd, address);
892 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
893 vmf.pte++, vmf.address += PAGE_SIZE) {
Jan Kara29943022016-12-14 15:07:16 -0800894 vmf.orig_pte = *vmf.pte;
895 if (!is_swap_pte(vmf.orig_pte))
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700896 continue;
897 swapped_in++;
Jan Kara29943022016-12-14 15:07:16 -0800898 ret = do_swap_page(&vmf);
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700899
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700900 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
901 if (ret & VM_FAULT_RETRY) {
902 down_read(&mm->mmap_sem);
Jan Kara82b0f8c2016-12-14 15:06:58 -0800903 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {
Ebru Akagunduz47f863e2016-07-26 15:26:43 -0700904 /* vma is no longer available, don't continue to swapin */
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700905 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700906 return false;
Ebru Akagunduz47f863e2016-07-26 15:26:43 -0700907 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700908 /* check if the pmd is still valid */
SeongJae Park835152a2017-05-12 15:46:38 -0700909 if (mm_find_pmd(mm, address) != pmd) {
910 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700911 return false;
SeongJae Park835152a2017-05-12 15:46:38 -0700912 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700913 }
914 if (ret & VM_FAULT_ERROR) {
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700915 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700916 return false;
917 }
918 /* pte is unmapped now, we need to map it */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800919 vmf.pte = pte_offset_map(pmd, vmf.address);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700920 }
Jan Kara82b0f8c2016-12-14 15:06:58 -0800921 vmf.pte--;
922 pte_unmap(vmf.pte);
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700923 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700924 return true;
925}
926
927static void collapse_huge_page(struct mm_struct *mm,
928 unsigned long address,
929 struct page **hpage,
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700930 int node, int referenced)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700931{
932 pmd_t *pmd, _pmd;
933 pte_t *pte;
934 pgtable_t pgtable;
935 struct page *new_page;
936 spinlock_t *pmd_ptl, *pte_ptl;
937 int isolated = 0, result = 0;
938 struct mem_cgroup *memcg;
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700939 struct vm_area_struct *vma;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700940 unsigned long mmun_start; /* For mmu_notifiers */
941 unsigned long mmun_end; /* For mmu_notifiers */
942 gfp_t gfp;
943
944 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
945
946 /* Only allocate from the target node */
Michal Hocko41b61672017-01-10 16:57:42 -0800947 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700948
Kirill A. Shutemov988ddb72016-07-26 15:26:26 -0700949 /*
950 * Before allocating the hugepage, release the mmap_sem read lock.
951 * The allocation can take potentially a long time if it involves
952 * sync compaction, and we do not need to hold the mmap_sem during
953 * that. We will recheck the vma after taking it again in write mode.
954 */
955 up_read(&mm->mmap_sem);
956 new_page = khugepaged_alloc_page(hpage, gfp, node);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700957 if (!new_page) {
958 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
959 goto out_nolock;
960 }
961
962 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
963 result = SCAN_CGROUP_CHARGE_FAIL;
964 goto out_nolock;
965 }
966
967 down_read(&mm->mmap_sem);
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700968 result = hugepage_vma_revalidate(mm, address, &vma);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700969 if (result) {
970 mem_cgroup_cancel_charge(new_page, memcg, true);
971 up_read(&mm->mmap_sem);
972 goto out_nolock;
973 }
974
975 pmd = mm_find_pmd(mm, address);
976 if (!pmd) {
977 result = SCAN_PMD_NULL;
978 mem_cgroup_cancel_charge(new_page, memcg, true);
979 up_read(&mm->mmap_sem);
980 goto out_nolock;
981 }
982
983 /*
984 * __collapse_huge_page_swapin always returns with mmap_sem locked.
Ebru Akagunduz47f863e2016-07-26 15:26:43 -0700985 * If it fails, we release mmap_sem and jump out_nolock.
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700986 * Continuing to collapse causes inconsistency.
987 */
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700988 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700989 mem_cgroup_cancel_charge(new_page, memcg, true);
990 up_read(&mm->mmap_sem);
991 goto out_nolock;
992 }
993
994 up_read(&mm->mmap_sem);
995 /*
996 * Prevent all access to pagetables with the exception of
997 * gup_fast later handled by the ptep_clear_flush and the VM
998 * handled by the anon_vma lock + PG_lock.
999 */
1000 down_write(&mm->mmap_sem);
Kirill A. Shutemovc131f752016-09-19 14:44:01 -07001001 result = hugepage_vma_revalidate(mm, address, &vma);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001002 if (result)
1003 goto out;
1004 /* check if the pmd is still valid */
1005 if (mm_find_pmd(mm, address) != pmd)
1006 goto out;
1007
1008 anon_vma_lock_write(vma->anon_vma);
1009
1010 pte = pte_offset_map(pmd, address);
1011 pte_ptl = pte_lockptr(mm, pmd);
1012
1013 mmun_start = address;
1014 mmun_end = address + HPAGE_PMD_SIZE;
1015 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1016 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1017 /*
1018 * After this gup_fast can't run anymore. This also removes
1019 * any huge TLB entry from the CPU so we won't allow
1020 * huge and small TLB entries for the same virtual address
1021 * to avoid the risk of CPU bugs in that area.
1022 */
1023 _pmd = pmdp_collapse_flush(vma, address, pmd);
1024 spin_unlock(pmd_ptl);
1025 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1026
1027 spin_lock(pte_ptl);
1028 isolated = __collapse_huge_page_isolate(vma, address, pte);
1029 spin_unlock(pte_ptl);
1030
1031 if (unlikely(!isolated)) {
1032 pte_unmap(pte);
1033 spin_lock(pmd_ptl);
1034 BUG_ON(!pmd_none(*pmd));
1035 /*
1036 * We can only use set_pmd_at when establishing
1037 * hugepmds and never for establishing regular pmds that
1038 * points to regular pagetables. Use pmd_populate for that
1039 */
1040 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1041 spin_unlock(pmd_ptl);
1042 anon_vma_unlock_write(vma->anon_vma);
1043 result = SCAN_FAIL;
1044 goto out;
1045 }
1046
1047 /*
1048 * All pages are isolated and locked so anon_vma rmap
1049 * can't run anymore.
1050 */
1051 anon_vma_unlock_write(vma->anon_vma);
1052
1053 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
1054 pte_unmap(pte);
1055 __SetPageUptodate(new_page);
1056 pgtable = pmd_pgtable(_pmd);
1057
1058 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1059 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1060
1061 /*
1062 * spin_lock() below is not the equivalent of smp_wmb(), so
1063 * this is needed to avoid the copy_huge_page writes to become
1064 * visible after the set_pmd_at() write.
1065 */
1066 smp_wmb();
1067
1068 spin_lock(pmd_ptl);
1069 BUG_ON(!pmd_none(*pmd));
1070 page_add_new_anon_rmap(new_page, vma, address, true);
1071 mem_cgroup_commit_charge(new_page, memcg, false, true);
1072 lru_cache_add_active_or_unevictable(new_page, vma);
1073 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1074 set_pmd_at(mm, address, pmd, _pmd);
1075 update_mmu_cache_pmd(vma, address, pmd);
1076 spin_unlock(pmd_ptl);
1077
1078 *hpage = NULL;
1079
1080 khugepaged_pages_collapsed++;
1081 result = SCAN_SUCCEED;
1082out_up_write:
1083 up_write(&mm->mmap_sem);
1084out_nolock:
1085 trace_mm_collapse_huge_page(mm, isolated, result);
1086 return;
1087out:
1088 mem_cgroup_cancel_charge(new_page, memcg, true);
1089 goto out_up_write;
1090}
1091
1092static int khugepaged_scan_pmd(struct mm_struct *mm,
1093 struct vm_area_struct *vma,
1094 unsigned long address,
1095 struct page **hpage)
1096{
1097 pmd_t *pmd;
1098 pte_t *pte, *_pte;
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001099 int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001100 struct page *page = NULL;
1101 unsigned long _address;
1102 spinlock_t *ptl;
1103 int node = NUMA_NO_NODE, unmapped = 0;
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001104 bool writable = false;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001105
1106 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1107
1108 pmd = mm_find_pmd(mm, address);
1109 if (!pmd) {
1110 result = SCAN_PMD_NULL;
1111 goto out;
1112 }
1113
1114 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1115 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1116 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1117 _pte++, _address += PAGE_SIZE) {
1118 pte_t pteval = *_pte;
1119 if (is_swap_pte(pteval)) {
1120 if (++unmapped <= khugepaged_max_ptes_swap) {
1121 continue;
1122 } else {
1123 result = SCAN_EXCEED_SWAP_PTE;
1124 goto out_unmap;
1125 }
1126 }
1127 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1128 if (!userfaultfd_armed(vma) &&
1129 ++none_or_zero <= khugepaged_max_ptes_none) {
1130 continue;
1131 } else {
1132 result = SCAN_EXCEED_NONE_PTE;
1133 goto out_unmap;
1134 }
1135 }
1136 if (!pte_present(pteval)) {
1137 result = SCAN_PTE_NON_PRESENT;
1138 goto out_unmap;
1139 }
1140 if (pte_write(pteval))
1141 writable = true;
1142
1143 page = vm_normal_page(vma, _address, pteval);
1144 if (unlikely(!page)) {
1145 result = SCAN_PAGE_NULL;
1146 goto out_unmap;
1147 }
1148
1149 /* TODO: teach khugepaged to collapse THP mapped with pte */
1150 if (PageCompound(page)) {
1151 result = SCAN_PAGE_COMPOUND;
1152 goto out_unmap;
1153 }
1154
1155 /*
1156 * Record which node the original page is from and save this
1157 * information to khugepaged_node_load[].
1158 * Khupaged will allocate hugepage from the node has the max
1159 * hit record.
1160 */
1161 node = page_to_nid(page);
1162 if (khugepaged_scan_abort(node)) {
1163 result = SCAN_SCAN_ABORT;
1164 goto out_unmap;
1165 }
1166 khugepaged_node_load[node]++;
1167 if (!PageLRU(page)) {
1168 result = SCAN_PAGE_LRU;
1169 goto out_unmap;
1170 }
1171 if (PageLocked(page)) {
1172 result = SCAN_PAGE_LOCK;
1173 goto out_unmap;
1174 }
1175 if (!PageAnon(page)) {
1176 result = SCAN_PAGE_ANON;
1177 goto out_unmap;
1178 }
1179
1180 /*
1181 * cannot use mapcount: can't collapse if there's a gup pin.
1182 * The page must only be referenced by the scanned process
1183 * and page swap cache.
1184 */
Minchan Kim2948be52017-05-03 14:53:35 -07001185 if (page_count(page) != 1 + PageSwapCache(page)) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001186 result = SCAN_PAGE_COUNT;
1187 goto out_unmap;
1188 }
1189 if (pte_young(pteval) ||
1190 page_is_young(page) || PageReferenced(page) ||
1191 mmu_notifier_test_young(vma->vm_mm, address))
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001192 referenced++;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001193 }
1194 if (writable) {
1195 if (referenced) {
1196 result = SCAN_SUCCEED;
1197 ret = 1;
1198 } else {
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001199 result = SCAN_LACK_REFERENCED_PAGE;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001200 }
1201 } else {
1202 result = SCAN_PAGE_RO;
1203 }
1204out_unmap:
1205 pte_unmap_unlock(pte, ptl);
1206 if (ret) {
1207 node = khugepaged_find_target_node();
1208 /* collapse_huge_page will return with the mmap_sem released */
Kirill A. Shutemovc131f752016-09-19 14:44:01 -07001209 collapse_huge_page(mm, address, hpage, node, referenced);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001210 }
1211out:
1212 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1213 none_or_zero, result, unmapped);
1214 return ret;
1215}
1216
1217static void collect_mm_slot(struct mm_slot *mm_slot)
1218{
1219 struct mm_struct *mm = mm_slot->mm;
1220
1221 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1222
1223 if (khugepaged_test_exit(mm)) {
1224 /* free mm_slot */
1225 hash_del(&mm_slot->hash);
1226 list_del(&mm_slot->mm_node);
1227
1228 /*
1229 * Not strictly needed because the mm exited already.
1230 *
1231 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1232 */
1233
1234 /* khugepaged_mm_lock actually not necessary for the below */
1235 free_mm_slot(mm_slot);
1236 mmdrop(mm);
1237 }
1238}
1239
Kirill A. Shutemove496cf32016-07-26 15:26:35 -07001240#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001241static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1242{
1243 struct vm_area_struct *vma;
1244 unsigned long addr;
1245 pmd_t *pmd, _pmd;
1246
1247 i_mmap_lock_write(mapping);
1248 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1249 /* probably overkill */
1250 if (vma->anon_vma)
1251 continue;
1252 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1253 if (addr & ~HPAGE_PMD_MASK)
1254 continue;
1255 if (vma->vm_end < addr + HPAGE_PMD_SIZE)
1256 continue;
1257 pmd = mm_find_pmd(vma->vm_mm, addr);
1258 if (!pmd)
1259 continue;
1260 /*
1261 * We need exclusive mmap_sem to retract page table.
1262 * If trylock fails we would end up with pte-mapped THP after
1263 * re-fault. Not ideal, but it's more important to not disturb
1264 * the system too much.
1265 */
1266 if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
1267 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
1268 /* assume page table is clear */
1269 _pmd = pmdp_collapse_flush(vma, addr, pmd);
1270 spin_unlock(ptl);
1271 up_write(&vma->vm_mm->mmap_sem);
Aneesh Kumar K.Vd670ffd2017-01-10 16:57:18 -08001272 atomic_long_dec(&vma->vm_mm->nr_ptes);
1273 pte_free(vma->vm_mm, pmd_pgtable(_pmd));
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001274 }
1275 }
1276 i_mmap_unlock_write(mapping);
1277}
1278
1279/**
1280 * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
1281 *
1282 * Basic scheme is simple, details are more complex:
1283 * - allocate and freeze a new huge page;
1284 * - scan over radix tree replacing old pages the new one
1285 * + swap in pages if necessary;
1286 * + fill in gaps;
1287 * + keep old pages around in case if rollback is required;
1288 * - if replacing succeed:
1289 * + copy data over;
1290 * + free old pages;
1291 * + unfreeze huge page;
1292 * - if replacing failed;
1293 * + put all pages back and unfreeze them;
1294 * + restore gaps in the radix-tree;
1295 * + free huge page;
1296 */
1297static void collapse_shmem(struct mm_struct *mm,
1298 struct address_space *mapping, pgoff_t start,
1299 struct page **hpage, int node)
1300{
1301 gfp_t gfp;
1302 struct page *page, *new_page, *tmp;
1303 struct mem_cgroup *memcg;
1304 pgoff_t index, end = start + HPAGE_PMD_NR;
1305 LIST_HEAD(pagelist);
1306 struct radix_tree_iter iter;
1307 void **slot;
1308 int nr_none = 0, result = SCAN_SUCCEED;
1309
1310 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1311
1312 /* Only allocate from the target node */
Michal Hocko41b61672017-01-10 16:57:42 -08001313 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001314
1315 new_page = khugepaged_alloc_page(hpage, gfp, node);
1316 if (!new_page) {
1317 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1318 goto out;
1319 }
1320
1321 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
1322 result = SCAN_CGROUP_CHARGE_FAIL;
1323 goto out;
1324 }
1325
1326 new_page->index = start;
1327 new_page->mapping = mapping;
1328 __SetPageSwapBacked(new_page);
1329 __SetPageLocked(new_page);
1330 BUG_ON(!page_ref_freeze(new_page, 1));
1331
1332
1333 /*
1334 * At this point the new_page is 'frozen' (page_count() is zero), locked
1335 * and not up-to-date. It's safe to insert it into radix tree, because
1336 * nobody would be able to map it or use it in other way until we
1337 * unfreeze it.
1338 */
1339
1340 index = start;
1341 spin_lock_irq(&mapping->tree_lock);
1342 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1343 int n = min(iter.index, end) - index;
1344
1345 /*
1346 * Handle holes in the radix tree: charge it from shmem and
1347 * insert relevant subpage of new_page into the radix-tree.
1348 */
1349 if (n && !shmem_charge(mapping->host, n)) {
1350 result = SCAN_FAIL;
1351 break;
1352 }
1353 nr_none += n;
1354 for (; index < min(iter.index, end); index++) {
1355 radix_tree_insert(&mapping->page_tree, index,
1356 new_page + (index % HPAGE_PMD_NR));
1357 }
1358
1359 /* We are done. */
1360 if (index >= end)
1361 break;
1362
1363 page = radix_tree_deref_slot_protected(slot,
1364 &mapping->tree_lock);
1365 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) {
1366 spin_unlock_irq(&mapping->tree_lock);
1367 /* swap in or instantiate fallocated page */
1368 if (shmem_getpage(mapping->host, index, &page,
1369 SGP_NOHUGE)) {
1370 result = SCAN_FAIL;
1371 goto tree_unlocked;
1372 }
1373 spin_lock_irq(&mapping->tree_lock);
1374 } else if (trylock_page(page)) {
1375 get_page(page);
1376 } else {
1377 result = SCAN_PAGE_LOCK;
1378 break;
1379 }
1380
1381 /*
1382 * The page must be locked, so we can drop the tree_lock
1383 * without racing with truncate.
1384 */
1385 VM_BUG_ON_PAGE(!PageLocked(page), page);
1386 VM_BUG_ON_PAGE(!PageUptodate(page), page);
1387 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1388
1389 if (page_mapping(page) != mapping) {
1390 result = SCAN_TRUNCATED;
1391 goto out_unlock;
1392 }
1393 spin_unlock_irq(&mapping->tree_lock);
1394
1395 if (isolate_lru_page(page)) {
1396 result = SCAN_DEL_PAGE_LRU;
1397 goto out_isolate_failed;
1398 }
1399
1400 if (page_mapped(page))
1401 unmap_mapping_range(mapping, index << PAGE_SHIFT,
1402 PAGE_SIZE, 0);
1403
1404 spin_lock_irq(&mapping->tree_lock);
1405
Johannes Weiner91a45f72016-12-12 16:43:32 -08001406 slot = radix_tree_lookup_slot(&mapping->page_tree, index);
1407 VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
1408 &mapping->tree_lock), page);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001409 VM_BUG_ON_PAGE(page_mapped(page), page);
1410
1411 /*
1412 * The page is expected to have page_count() == 3:
1413 * - we hold a pin on it;
1414 * - one reference from radix tree;
1415 * - one from isolate_lru_page;
1416 */
1417 if (!page_ref_freeze(page, 3)) {
1418 result = SCAN_PAGE_COUNT;
1419 goto out_lru;
1420 }
1421
1422 /*
1423 * Add the page to the list to be able to undo the collapse if
1424 * something go wrong.
1425 */
1426 list_add_tail(&page->lru, &pagelist);
1427
1428 /* Finally, replace with the new page. */
Johannes Weiner6d75f362016-12-12 16:43:43 -08001429 radix_tree_replace_slot(&mapping->page_tree, slot,
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001430 new_page + (index % HPAGE_PMD_NR));
1431
Matthew Wilcox148deab2016-12-14 15:08:49 -08001432 slot = radix_tree_iter_resume(slot, &iter);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001433 index++;
1434 continue;
1435out_lru:
1436 spin_unlock_irq(&mapping->tree_lock);
1437 putback_lru_page(page);
1438out_isolate_failed:
1439 unlock_page(page);
1440 put_page(page);
1441 goto tree_unlocked;
1442out_unlock:
1443 unlock_page(page);
1444 put_page(page);
1445 break;
1446 }
1447
1448 /*
1449 * Handle hole in radix tree at the end of the range.
1450 * This code only triggers if there's nothing in radix tree
1451 * beyond 'end'.
1452 */
1453 if (result == SCAN_SUCCEED && index < end) {
1454 int n = end - index;
1455
1456 if (!shmem_charge(mapping->host, n)) {
1457 result = SCAN_FAIL;
1458 goto tree_locked;
1459 }
1460
1461 for (; index < end; index++) {
1462 radix_tree_insert(&mapping->page_tree, index,
1463 new_page + (index % HPAGE_PMD_NR));
1464 }
1465 nr_none += n;
1466 }
1467
1468tree_locked:
1469 spin_unlock_irq(&mapping->tree_lock);
1470tree_unlocked:
1471
1472 if (result == SCAN_SUCCEED) {
1473 unsigned long flags;
1474 struct zone *zone = page_zone(new_page);
1475
1476 /*
1477 * Replacing old pages with new one has succeed, now we need to
1478 * copy the content and free old pages.
1479 */
1480 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
1481 copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
1482 page);
1483 list_del(&page->lru);
1484 unlock_page(page);
1485 page_ref_unfreeze(page, 1);
1486 page->mapping = NULL;
1487 ClearPageActive(page);
1488 ClearPageUnevictable(page);
1489 put_page(page);
1490 }
1491
1492 local_irq_save(flags);
Mel Gorman11fb9982016-07-28 15:46:20 -07001493 __inc_node_page_state(new_page, NR_SHMEM_THPS);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001494 if (nr_none) {
Mel Gorman11fb9982016-07-28 15:46:20 -07001495 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
1496 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001497 }
1498 local_irq_restore(flags);
1499
1500 /*
1501 * Remove pte page tables, so we can re-faulti
1502 * the page as huge.
1503 */
1504 retract_page_tables(mapping, start);
1505
1506 /* Everything is ready, let's unfreeze the new_page */
1507 set_page_dirty(new_page);
1508 SetPageUptodate(new_page);
1509 page_ref_unfreeze(new_page, HPAGE_PMD_NR);
1510 mem_cgroup_commit_charge(new_page, memcg, false, true);
1511 lru_cache_add_anon(new_page);
1512 unlock_page(new_page);
1513
1514 *hpage = NULL;
1515 } else {
1516 /* Something went wrong: rollback changes to the radix-tree */
1517 shmem_uncharge(mapping->host, nr_none);
1518 spin_lock_irq(&mapping->tree_lock);
1519 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
1520 start) {
1521 if (iter.index >= end)
1522 break;
1523 page = list_first_entry_or_null(&pagelist,
1524 struct page, lru);
1525 if (!page || iter.index < page->index) {
1526 if (!nr_none)
1527 break;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001528 nr_none--;
Johannes Weiner59749e62016-12-12 16:43:35 -08001529 /* Put holes back where they were */
1530 radix_tree_delete(&mapping->page_tree,
1531 iter.index);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001532 continue;
1533 }
1534
1535 VM_BUG_ON_PAGE(page->index != iter.index, page);
1536
1537 /* Unfreeze the page. */
1538 list_del(&page->lru);
1539 page_ref_unfreeze(page, 2);
Johannes Weiner6d75f362016-12-12 16:43:43 -08001540 radix_tree_replace_slot(&mapping->page_tree,
1541 slot, page);
Matthew Wilcox148deab2016-12-14 15:08:49 -08001542 slot = radix_tree_iter_resume(slot, &iter);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001543 spin_unlock_irq(&mapping->tree_lock);
1544 putback_lru_page(page);
1545 unlock_page(page);
1546 spin_lock_irq(&mapping->tree_lock);
1547 }
1548 VM_BUG_ON(nr_none);
1549 spin_unlock_irq(&mapping->tree_lock);
1550
1551 /* Unfreeze new_page, caller would take care about freeing it */
1552 page_ref_unfreeze(new_page, 1);
1553 mem_cgroup_cancel_charge(new_page, memcg, true);
1554 unlock_page(new_page);
1555 new_page->mapping = NULL;
1556 }
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 struct radix_tree_iter iter;
1568 void **slot;
1569 int present, swap;
1570 int node = NUMA_NO_NODE;
1571 int result = SCAN_SUCCEED;
1572
1573 present = 0;
1574 swap = 0;
1575 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1576 rcu_read_lock();
1577 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1578 if (iter.index >= start + HPAGE_PMD_NR)
1579 break;
1580
1581 page = radix_tree_deref_slot(slot);
1582 if (radix_tree_deref_retry(page)) {
1583 slot = radix_tree_iter_retry(&iter);
1584 continue;
1585 }
1586
1587 if (radix_tree_exception(page)) {
1588 if (++swap > khugepaged_max_ptes_swap) {
1589 result = SCAN_EXCEED_SWAP_PTE;
1590 break;
1591 }
1592 continue;
1593 }
1594
1595 if (PageTransCompound(page)) {
1596 result = SCAN_PAGE_COMPOUND;
1597 break;
1598 }
1599
1600 node = page_to_nid(page);
1601 if (khugepaged_scan_abort(node)) {
1602 result = SCAN_SCAN_ABORT;
1603 break;
1604 }
1605 khugepaged_node_load[node]++;
1606
1607 if (!PageLRU(page)) {
1608 result = SCAN_PAGE_LRU;
1609 break;
1610 }
1611
1612 if (page_count(page) != 1 + page_mapcount(page)) {
1613 result = SCAN_PAGE_COUNT;
1614 break;
1615 }
1616
1617 /*
1618 * We probably should check if the page is referenced here, but
1619 * nobody would transfer pte_young() to PageReferenced() for us.
1620 * And rmap walk here is just too costly...
1621 */
1622
1623 present++;
1624
1625 if (need_resched()) {
Matthew Wilcox148deab2016-12-14 15:08:49 -08001626 slot = radix_tree_iter_resume(slot, &iter);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001627 cond_resched_rcu();
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001628 }
1629 }
1630 rcu_read_unlock();
1631
1632 if (result == SCAN_SUCCEED) {
1633 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
1634 result = SCAN_EXCEED_NONE_PTE;
1635 } else {
1636 node = khugepaged_find_target_node();
1637 collapse_shmem(mm, mapping, start, hpage, node);
1638 }
1639 }
1640
1641 /* TODO: tracepoints */
1642}
1643#else
1644static void khugepaged_scan_shmem(struct mm_struct *mm,
1645 struct address_space *mapping,
1646 pgoff_t start, struct page **hpage)
1647{
1648 BUILD_BUG();
1649}
1650#endif
1651
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001652static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1653 struct page **hpage)
1654 __releases(&khugepaged_mm_lock)
1655 __acquires(&khugepaged_mm_lock)
1656{
1657 struct mm_slot *mm_slot;
1658 struct mm_struct *mm;
1659 struct vm_area_struct *vma;
1660 int progress = 0;
1661
1662 VM_BUG_ON(!pages);
1663 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1664
1665 if (khugepaged_scan.mm_slot)
1666 mm_slot = khugepaged_scan.mm_slot;
1667 else {
1668 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1669 struct mm_slot, mm_node);
1670 khugepaged_scan.address = 0;
1671 khugepaged_scan.mm_slot = mm_slot;
1672 }
1673 spin_unlock(&khugepaged_mm_lock);
1674
1675 mm = mm_slot->mm;
1676 down_read(&mm->mmap_sem);
1677 if (unlikely(khugepaged_test_exit(mm)))
1678 vma = NULL;
1679 else
1680 vma = find_vma(mm, khugepaged_scan.address);
1681
1682 progress++;
1683 for (; vma; vma = vma->vm_next) {
1684 unsigned long hstart, hend;
1685
1686 cond_resched();
1687 if (unlikely(khugepaged_test_exit(mm))) {
1688 progress++;
1689 break;
1690 }
1691 if (!hugepage_vma_check(vma)) {
1692skip:
1693 progress++;
1694 continue;
1695 }
1696 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1697 hend = vma->vm_end & HPAGE_PMD_MASK;
1698 if (hstart >= hend)
1699 goto skip;
1700 if (khugepaged_scan.address > hend)
1701 goto skip;
1702 if (khugepaged_scan.address < hstart)
1703 khugepaged_scan.address = hstart;
1704 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1705
1706 while (khugepaged_scan.address < hend) {
1707 int ret;
1708 cond_resched();
1709 if (unlikely(khugepaged_test_exit(mm)))
1710 goto breakouterloop;
1711
1712 VM_BUG_ON(khugepaged_scan.address < hstart ||
1713 khugepaged_scan.address + HPAGE_PMD_SIZE >
1714 hend);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001715 if (shmem_file(vma->vm_file)) {
Kirill A. Shutemove496cf32016-07-26 15:26:35 -07001716 struct file *file;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001717 pgoff_t pgoff = linear_page_index(vma,
1718 khugepaged_scan.address);
Kirill A. Shutemove496cf32016-07-26 15:26:35 -07001719 if (!shmem_huge_enabled(vma))
1720 goto skip;
1721 file = get_file(vma->vm_file);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001722 up_read(&mm->mmap_sem);
1723 ret = 1;
1724 khugepaged_scan_shmem(mm, file->f_mapping,
1725 pgoff, hpage);
1726 fput(file);
1727 } else {
1728 ret = khugepaged_scan_pmd(mm, vma,
1729 khugepaged_scan.address,
1730 hpage);
1731 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001732 /* move to next address */
1733 khugepaged_scan.address += HPAGE_PMD_SIZE;
1734 progress += HPAGE_PMD_NR;
1735 if (ret)
1736 /* we released mmap_sem so break loop */
1737 goto breakouterloop_mmap_sem;
1738 if (progress >= pages)
1739 goto breakouterloop;
1740 }
1741 }
1742breakouterloop:
1743 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1744breakouterloop_mmap_sem:
1745
1746 spin_lock(&khugepaged_mm_lock);
1747 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1748 /*
1749 * Release the current mm_slot if this mm is about to die, or
1750 * if we scanned all vmas of this mm.
1751 */
1752 if (khugepaged_test_exit(mm) || !vma) {
1753 /*
1754 * Make sure that if mm_users is reaching zero while
1755 * khugepaged runs here, khugepaged_exit will find
1756 * mm_slot not pointing to the exiting mm.
1757 */
1758 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1759 khugepaged_scan.mm_slot = list_entry(
1760 mm_slot->mm_node.next,
1761 struct mm_slot, mm_node);
1762 khugepaged_scan.address = 0;
1763 } else {
1764 khugepaged_scan.mm_slot = NULL;
1765 khugepaged_full_scans++;
1766 }
1767
1768 collect_mm_slot(mm_slot);
1769 }
1770
1771 return progress;
1772}
1773
1774static int khugepaged_has_work(void)
1775{
1776 return !list_empty(&khugepaged_scan.mm_head) &&
1777 khugepaged_enabled();
1778}
1779
1780static int khugepaged_wait_event(void)
1781{
1782 return !list_empty(&khugepaged_scan.mm_head) ||
1783 kthread_should_stop();
1784}
1785
1786static void khugepaged_do_scan(void)
1787{
1788 struct page *hpage = NULL;
1789 unsigned int progress = 0, pass_through_head = 0;
1790 unsigned int pages = khugepaged_pages_to_scan;
1791 bool wait = true;
1792
1793 barrier(); /* write khugepaged_pages_to_scan to local stack */
1794
1795 while (progress < pages) {
1796 if (!khugepaged_prealloc_page(&hpage, &wait))
1797 break;
1798
1799 cond_resched();
1800
1801 if (unlikely(kthread_should_stop() || try_to_freeze()))
1802 break;
1803
1804 spin_lock(&khugepaged_mm_lock);
1805 if (!khugepaged_scan.mm_slot)
1806 pass_through_head++;
1807 if (khugepaged_has_work() &&
1808 pass_through_head < 2)
1809 progress += khugepaged_scan_mm_slot(pages - progress,
1810 &hpage);
1811 else
1812 progress = pages;
1813 spin_unlock(&khugepaged_mm_lock);
1814 }
1815
1816 if (!IS_ERR_OR_NULL(hpage))
1817 put_page(hpage);
1818}
1819
1820static bool khugepaged_should_wakeup(void)
1821{
1822 return kthread_should_stop() ||
1823 time_after_eq(jiffies, khugepaged_sleep_expire);
1824}
1825
1826static void khugepaged_wait_work(void)
1827{
1828 if (khugepaged_has_work()) {
1829 const unsigned long scan_sleep_jiffies =
1830 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
1831
1832 if (!scan_sleep_jiffies)
1833 return;
1834
1835 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
1836 wait_event_freezable_timeout(khugepaged_wait,
1837 khugepaged_should_wakeup(),
1838 scan_sleep_jiffies);
1839 return;
1840 }
1841
1842 if (khugepaged_enabled())
1843 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
1844}
1845
1846static int khugepaged(void *none)
1847{
1848 struct mm_slot *mm_slot;
1849
1850 set_freezable();
1851 set_user_nice(current, MAX_NICE);
1852
1853 while (!kthread_should_stop()) {
1854 khugepaged_do_scan();
1855 khugepaged_wait_work();
1856 }
1857
1858 spin_lock(&khugepaged_mm_lock);
1859 mm_slot = khugepaged_scan.mm_slot;
1860 khugepaged_scan.mm_slot = NULL;
1861 if (mm_slot)
1862 collect_mm_slot(mm_slot);
1863 spin_unlock(&khugepaged_mm_lock);
1864 return 0;
1865}
1866
1867static void set_recommended_min_free_kbytes(void)
1868{
1869 struct zone *zone;
1870 int nr_zones = 0;
1871 unsigned long recommended_min;
1872
1873 for_each_populated_zone(zone)
1874 nr_zones++;
1875
1876 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1877 recommended_min = pageblock_nr_pages * nr_zones * 2;
1878
1879 /*
1880 * Make sure that on average at least two pageblocks are almost free
1881 * of another type, one for a migratetype to fall back to and a
1882 * second to avoid subsequent fallbacks of other types There are 3
1883 * MIGRATE_TYPES we care about.
1884 */
1885 recommended_min += pageblock_nr_pages * nr_zones *
1886 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
1887
1888 /* don't ever allow to reserve more than 5% of the lowmem */
1889 recommended_min = min(recommended_min,
1890 (unsigned long) nr_free_buffer_pages() / 20);
1891 recommended_min <<= (PAGE_SHIFT-10);
1892
1893 if (recommended_min > min_free_kbytes) {
1894 if (user_min_free_kbytes >= 0)
1895 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1896 min_free_kbytes, recommended_min);
1897
1898 min_free_kbytes = recommended_min;
1899 }
1900 setup_per_zone_wmarks();
1901}
1902
1903int start_stop_khugepaged(void)
1904{
1905 static struct task_struct *khugepaged_thread __read_mostly;
1906 static DEFINE_MUTEX(khugepaged_mutex);
1907 int err = 0;
1908
1909 mutex_lock(&khugepaged_mutex);
1910 if (khugepaged_enabled()) {
1911 if (!khugepaged_thread)
1912 khugepaged_thread = kthread_run(khugepaged, NULL,
1913 "khugepaged");
1914 if (IS_ERR(khugepaged_thread)) {
1915 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1916 err = PTR_ERR(khugepaged_thread);
1917 khugepaged_thread = NULL;
1918 goto fail;
1919 }
1920
1921 if (!list_empty(&khugepaged_scan.mm_head))
1922 wake_up_interruptible(&khugepaged_wait);
1923
1924 set_recommended_min_free_kbytes();
1925 } else if (khugepaged_thread) {
1926 kthread_stop(khugepaged_thread);
1927 khugepaged_thread = NULL;
1928 }
1929fail:
1930 mutex_unlock(&khugepaged_mutex);
1931 return err;
1932}