blob: ea4ff259b67195b32d3335795d4de80c4e6e5bcf [file] [log] [blame]
Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07002#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3
4#include <linux/mm.h>
5#include <linux/sched.h>
Ingo Molnar6e84f312017-02-08 18:51:29 +01006#include <linux/sched/mm.h>
Ingo Molnarf7ccbae2017-02-08 18:51:30 +01007#include <linux/sched/coredump.h>
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07008#include <linux/mmu_notifier.h>
9#include <linux/rmap.h>
10#include <linux/swap.h>
11#include <linux/mm_inline.h>
12#include <linux/kthread.h>
13#include <linux/khugepaged.h>
14#include <linux/freezer.h>
15#include <linux/mman.h>
16#include <linux/hashtable.h>
17#include <linux/userfaultfd_k.h>
18#include <linux/page_idle.h>
19#include <linux/swapops.h>
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -070020#include <linux/shmem_fs.h>
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -070021
22#include <asm/tlb.h>
23#include <asm/pgalloc.h>
24#include "internal.h"
25
26enum scan_result {
27 SCAN_FAIL,
28 SCAN_SUCCEED,
29 SCAN_PMD_NULL,
30 SCAN_EXCEED_NONE_PTE,
31 SCAN_PTE_NON_PRESENT,
32 SCAN_PAGE_RO,
Ebru Akagunduz0db501f2016-07-26 15:26:46 -070033 SCAN_LACK_REFERENCED_PAGE,
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -070034 SCAN_PAGE_NULL,
35 SCAN_SCAN_ABORT,
36 SCAN_PAGE_COUNT,
37 SCAN_PAGE_LRU,
38 SCAN_PAGE_LOCK,
39 SCAN_PAGE_ANON,
40 SCAN_PAGE_COMPOUND,
41 SCAN_ANY_PROCESS,
42 SCAN_VMA_NULL,
43 SCAN_VMA_CHECK,
44 SCAN_ADDRESS_RANGE,
45 SCAN_SWAP_CACHE_PAGE,
46 SCAN_DEL_PAGE_LRU,
47 SCAN_ALLOC_HUGE_PAGE_FAIL,
48 SCAN_CGROUP_CHARGE_FAIL,
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -070049 SCAN_EXCEED_SWAP_PTE,
50 SCAN_TRUNCATED,
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -070051};
52
53#define CREATE_TRACE_POINTS
54#include <trace/events/huge_memory.h>
55
56/* default scan 8*512 pte (or vmas) every 30 second */
57static unsigned int khugepaged_pages_to_scan __read_mostly;
58static unsigned int khugepaged_pages_collapsed;
59static unsigned int khugepaged_full_scans;
60static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
61/* during fragmentation poll the hugepage allocator once every minute */
62static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
63static unsigned long khugepaged_sleep_expire;
64static DEFINE_SPINLOCK(khugepaged_mm_lock);
65static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
66/*
67 * default collapse hugepages if there is at least one pte mapped like
68 * it would have happened if the vma was large enough during page
69 * fault.
70 */
71static unsigned int khugepaged_max_ptes_none __read_mostly;
72static unsigned int khugepaged_max_ptes_swap __read_mostly;
73
74#define MM_SLOTS_HASH_BITS 10
75static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
76
77static struct kmem_cache *mm_slot_cache __read_mostly;
78
79/**
80 * struct mm_slot - hash lookup from mm to mm_slot
81 * @hash: hash collision list
82 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
83 * @mm: the mm that this information is valid for
84 */
85struct mm_slot {
86 struct hlist_node hash;
87 struct list_head mm_node;
88 struct mm_struct *mm;
89};
90
91/**
92 * struct khugepaged_scan - cursor for scanning
93 * @mm_head: the head of the mm list to scan
94 * @mm_slot: the current mm_slot we are scanning
95 * @address: the next address inside that to be scanned
96 *
97 * There is only the one khugepaged_scan instance of this cursor structure.
98 */
99struct khugepaged_scan {
100 struct list_head mm_head;
101 struct mm_slot *mm_slot;
102 unsigned long address;
103};
104
105static struct khugepaged_scan khugepaged_scan = {
106 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
107};
108
Jérémy Lefauree1465d12016-11-30 15:54:02 -0800109#ifdef CONFIG_SYSFS
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700110static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
111 struct kobj_attribute *attr,
112 char *buf)
113{
114 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
115}
116
117static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
118 struct kobj_attribute *attr,
119 const char *buf, size_t count)
120{
121 unsigned long msecs;
122 int err;
123
124 err = kstrtoul(buf, 10, &msecs);
125 if (err || msecs > UINT_MAX)
126 return -EINVAL;
127
128 khugepaged_scan_sleep_millisecs = msecs;
129 khugepaged_sleep_expire = 0;
130 wake_up_interruptible(&khugepaged_wait);
131
132 return count;
133}
134static struct kobj_attribute scan_sleep_millisecs_attr =
135 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
136 scan_sleep_millisecs_store);
137
138static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
139 struct kobj_attribute *attr,
140 char *buf)
141{
142 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
143}
144
145static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
146 struct kobj_attribute *attr,
147 const char *buf, size_t count)
148{
149 unsigned long msecs;
150 int err;
151
152 err = kstrtoul(buf, 10, &msecs);
153 if (err || msecs > UINT_MAX)
154 return -EINVAL;
155
156 khugepaged_alloc_sleep_millisecs = msecs;
157 khugepaged_sleep_expire = 0;
158 wake_up_interruptible(&khugepaged_wait);
159
160 return count;
161}
162static struct kobj_attribute alloc_sleep_millisecs_attr =
163 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
164 alloc_sleep_millisecs_store);
165
166static ssize_t pages_to_scan_show(struct kobject *kobj,
167 struct kobj_attribute *attr,
168 char *buf)
169{
170 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
171}
172static ssize_t pages_to_scan_store(struct kobject *kobj,
173 struct kobj_attribute *attr,
174 const char *buf, size_t count)
175{
176 int err;
177 unsigned long pages;
178
179 err = kstrtoul(buf, 10, &pages);
180 if (err || !pages || pages > UINT_MAX)
181 return -EINVAL;
182
183 khugepaged_pages_to_scan = pages;
184
185 return count;
186}
187static struct kobj_attribute pages_to_scan_attr =
188 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
189 pages_to_scan_store);
190
191static ssize_t pages_collapsed_show(struct kobject *kobj,
192 struct kobj_attribute *attr,
193 char *buf)
194{
195 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
196}
197static struct kobj_attribute pages_collapsed_attr =
198 __ATTR_RO(pages_collapsed);
199
200static ssize_t full_scans_show(struct kobject *kobj,
201 struct kobj_attribute *attr,
202 char *buf)
203{
204 return sprintf(buf, "%u\n", khugepaged_full_scans);
205}
206static struct kobj_attribute full_scans_attr =
207 __ATTR_RO(full_scans);
208
209static ssize_t khugepaged_defrag_show(struct kobject *kobj,
210 struct kobj_attribute *attr, char *buf)
211{
212 return single_hugepage_flag_show(kobj, attr, buf,
213 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
214}
215static ssize_t khugepaged_defrag_store(struct kobject *kobj,
216 struct kobj_attribute *attr,
217 const char *buf, size_t count)
218{
219 return single_hugepage_flag_store(kobj, attr, buf, count,
220 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
221}
222static struct kobj_attribute khugepaged_defrag_attr =
223 __ATTR(defrag, 0644, khugepaged_defrag_show,
224 khugepaged_defrag_store);
225
226/*
227 * max_ptes_none controls if khugepaged should collapse hugepages over
228 * any unmapped ptes in turn potentially increasing the memory
229 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
230 * reduce the available free memory in the system as it
231 * runs. Increasing max_ptes_none will instead potentially reduce the
232 * free memory in the system during the khugepaged scan.
233 */
234static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
235 struct kobj_attribute *attr,
236 char *buf)
237{
238 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
239}
240static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
241 struct kobj_attribute *attr,
242 const char *buf, size_t count)
243{
244 int err;
245 unsigned long max_ptes_none;
246
247 err = kstrtoul(buf, 10, &max_ptes_none);
248 if (err || max_ptes_none > HPAGE_PMD_NR-1)
249 return -EINVAL;
250
251 khugepaged_max_ptes_none = max_ptes_none;
252
253 return count;
254}
255static struct kobj_attribute khugepaged_max_ptes_none_attr =
256 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
257 khugepaged_max_ptes_none_store);
258
259static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
260 struct kobj_attribute *attr,
261 char *buf)
262{
263 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
264}
265
266static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
267 struct kobj_attribute *attr,
268 const char *buf, size_t count)
269{
270 int err;
271 unsigned long max_ptes_swap;
272
273 err = kstrtoul(buf, 10, &max_ptes_swap);
274 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
275 return -EINVAL;
276
277 khugepaged_max_ptes_swap = max_ptes_swap;
278
279 return count;
280}
281
282static struct kobj_attribute khugepaged_max_ptes_swap_attr =
283 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
284 khugepaged_max_ptes_swap_store);
285
286static struct attribute *khugepaged_attr[] = {
287 &khugepaged_defrag_attr.attr,
288 &khugepaged_max_ptes_none_attr.attr,
289 &pages_to_scan_attr.attr,
290 &pages_collapsed_attr.attr,
291 &full_scans_attr.attr,
292 &scan_sleep_millisecs_attr.attr,
293 &alloc_sleep_millisecs_attr.attr,
294 &khugepaged_max_ptes_swap_attr.attr,
295 NULL,
296};
297
298struct attribute_group khugepaged_attr_group = {
299 .attrs = khugepaged_attr,
300 .name = "khugepaged",
301};
Jérémy Lefauree1465d12016-11-30 15:54:02 -0800302#endif /* CONFIG_SYSFS */
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700303
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -0700304#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700305
306int hugepage_madvise(struct vm_area_struct *vma,
307 unsigned long *vm_flags, int advice)
308{
309 switch (advice) {
310 case MADV_HUGEPAGE:
311#ifdef CONFIG_S390
312 /*
313 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
314 * can't handle this properly after s390_enable_sie, so we simply
315 * ignore the madvise to prevent qemu from causing a SIGSEGV.
316 */
317 if (mm_has_pgste(vma->vm_mm))
318 return 0;
319#endif
320 *vm_flags &= ~VM_NOHUGEPAGE;
321 *vm_flags |= VM_HUGEPAGE;
322 /*
323 * If the vma become good for khugepaged to scan,
324 * register it here without waiting a page fault that
325 * may not happen any time soon.
326 */
327 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
328 khugepaged_enter_vma_merge(vma, *vm_flags))
329 return -ENOMEM;
330 break;
331 case MADV_NOHUGEPAGE:
332 *vm_flags &= ~VM_HUGEPAGE;
333 *vm_flags |= VM_NOHUGEPAGE;
334 /*
335 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
336 * this vma even if we leave the mm registered in khugepaged if
337 * it got registered before VM_NOHUGEPAGE was set.
338 */
339 break;
340 }
341
342 return 0;
343}
344
345int __init khugepaged_init(void)
346{
347 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
348 sizeof(struct mm_slot),
349 __alignof__(struct mm_slot), 0, NULL);
350 if (!mm_slot_cache)
351 return -ENOMEM;
352
353 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
354 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
355 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
356
357 return 0;
358}
359
360void __init khugepaged_destroy(void)
361{
362 kmem_cache_destroy(mm_slot_cache);
363}
364
365static inline struct mm_slot *alloc_mm_slot(void)
366{
367 if (!mm_slot_cache) /* initialization failed */
368 return NULL;
369 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
370}
371
372static inline void free_mm_slot(struct mm_slot *mm_slot)
373{
374 kmem_cache_free(mm_slot_cache, mm_slot);
375}
376
377static struct mm_slot *get_mm_slot(struct mm_struct *mm)
378{
379 struct mm_slot *mm_slot;
380
381 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
382 if (mm == mm_slot->mm)
383 return mm_slot;
384
385 return NULL;
386}
387
388static void insert_to_mm_slots_hash(struct mm_struct *mm,
389 struct mm_slot *mm_slot)
390{
391 mm_slot->mm = mm;
392 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
393}
394
395static inline int khugepaged_test_exit(struct mm_struct *mm)
396{
397 return atomic_read(&mm->mm_users) == 0;
398}
399
400int __khugepaged_enter(struct mm_struct *mm)
401{
402 struct mm_slot *mm_slot;
403 int wakeup;
404
405 mm_slot = alloc_mm_slot();
406 if (!mm_slot)
407 return -ENOMEM;
408
409 /* __khugepaged_exit() must not run from under us */
410 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
411 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
412 free_mm_slot(mm_slot);
413 return 0;
414 }
415
416 spin_lock(&khugepaged_mm_lock);
417 insert_to_mm_slots_hash(mm, mm_slot);
418 /*
419 * Insert just behind the scanning cursor, to let the area settle
420 * down a little.
421 */
422 wakeup = list_empty(&khugepaged_scan.mm_head);
423 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
424 spin_unlock(&khugepaged_mm_lock);
425
Vegard Nossumf1f10072017-02-27 14:30:07 -0800426 mmgrab(mm);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700427 if (wakeup)
428 wake_up_interruptible(&khugepaged_wait);
429
430 return 0;
431}
432
433int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
434 unsigned long vm_flags)
435{
436 unsigned long hstart, hend;
437 if (!vma->anon_vma)
438 /*
439 * Not yet faulted in so we will register later in the
440 * page fault if needed.
441 */
442 return 0;
443 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
444 /* khugepaged not yet working on file or special mappings */
445 return 0;
446 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
447 hend = vma->vm_end & HPAGE_PMD_MASK;
448 if (hstart < hend)
449 return khugepaged_enter(vma, vm_flags);
450 return 0;
451}
452
453void __khugepaged_exit(struct mm_struct *mm)
454{
455 struct mm_slot *mm_slot;
456 int free = 0;
457
458 spin_lock(&khugepaged_mm_lock);
459 mm_slot = get_mm_slot(mm);
460 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
461 hash_del(&mm_slot->hash);
462 list_del(&mm_slot->mm_node);
463 free = 1;
464 }
465 spin_unlock(&khugepaged_mm_lock);
466
467 if (free) {
468 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
469 free_mm_slot(mm_slot);
470 mmdrop(mm);
471 } else if (mm_slot) {
472 /*
473 * This is required to serialize against
474 * khugepaged_test_exit() (which is guaranteed to run
475 * under mmap sem read mode). Stop here (after we
476 * return all pagetables will be destroyed) until
477 * khugepaged has finished working on the pagetables
478 * under the mmap_sem.
479 */
480 down_write(&mm->mmap_sem);
481 up_write(&mm->mmap_sem);
482 }
483}
484
485static void release_pte_page(struct page *page)
486{
Shaohua Lid44d3632017-05-03 14:52:26 -0700487 dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700488 unlock_page(page);
489 putback_lru_page(page);
490}
491
492static void release_pte_pages(pte_t *pte, pte_t *_pte)
493{
494 while (--_pte >= pte) {
495 pte_t pteval = *_pte;
496 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
497 release_pte_page(pte_page(pteval));
498 }
499}
500
501static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
502 unsigned long address,
503 pte_t *pte)
504{
505 struct page *page = NULL;
506 pte_t *_pte;
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700507 int none_or_zero = 0, result = 0, referenced = 0;
508 bool writable = false;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700509
510 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
511 _pte++, address += PAGE_SIZE) {
512 pte_t pteval = *_pte;
513 if (pte_none(pteval) || (pte_present(pteval) &&
514 is_zero_pfn(pte_pfn(pteval)))) {
515 if (!userfaultfd_armed(vma) &&
516 ++none_or_zero <= khugepaged_max_ptes_none) {
517 continue;
518 } else {
519 result = SCAN_EXCEED_NONE_PTE;
520 goto out;
521 }
522 }
523 if (!pte_present(pteval)) {
524 result = SCAN_PTE_NON_PRESENT;
525 goto out;
526 }
527 page = vm_normal_page(vma, address, pteval);
528 if (unlikely(!page)) {
529 result = SCAN_PAGE_NULL;
530 goto out;
531 }
532
533 VM_BUG_ON_PAGE(PageCompound(page), page);
534 VM_BUG_ON_PAGE(!PageAnon(page), page);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700535
536 /*
537 * We can do it before isolate_lru_page because the
538 * page can't be freed from under us. NOTE: PG_lock
539 * is needed to serialize against split_huge_page
540 * when invoked from the VM.
541 */
542 if (!trylock_page(page)) {
543 result = SCAN_PAGE_LOCK;
544 goto out;
545 }
546
547 /*
548 * cannot use mapcount: can't collapse if there's a gup pin.
549 * The page must only be referenced by the scanned process
550 * and page swap cache.
551 */
Minchan Kim2948be52017-05-03 14:53:35 -0700552 if (page_count(page) != 1 + PageSwapCache(page)) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700553 unlock_page(page);
554 result = SCAN_PAGE_COUNT;
555 goto out;
556 }
557 if (pte_write(pteval)) {
558 writable = true;
559 } else {
560 if (PageSwapCache(page) &&
561 !reuse_swap_page(page, NULL)) {
562 unlock_page(page);
563 result = SCAN_SWAP_CACHE_PAGE;
564 goto out;
565 }
566 /*
567 * Page is not in the swap cache. It can be collapsed
568 * into a THP.
569 */
570 }
571
572 /*
573 * Isolate the page to avoid collapsing an hugepage
574 * currently in use by the VM.
575 */
576 if (isolate_lru_page(page)) {
577 unlock_page(page);
578 result = SCAN_DEL_PAGE_LRU;
579 goto out;
580 }
Shaohua Lid44d3632017-05-03 14:52:26 -0700581 inc_node_page_state(page,
582 NR_ISOLATED_ANON + page_is_file_cache(page));
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700583 VM_BUG_ON_PAGE(!PageLocked(page), page);
584 VM_BUG_ON_PAGE(PageLRU(page), page);
585
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700586 /* There should be enough young pte to collapse the page */
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700587 if (pte_young(pteval) ||
588 page_is_young(page) || PageReferenced(page) ||
589 mmu_notifier_test_young(vma->vm_mm, address))
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700590 referenced++;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700591 }
592 if (likely(writable)) {
593 if (likely(referenced)) {
594 result = SCAN_SUCCEED;
595 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
596 referenced, writable, result);
597 return 1;
598 }
599 } else {
600 result = SCAN_PAGE_RO;
601 }
602
603out:
604 release_pte_pages(pte, _pte);
605 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
606 referenced, writable, result);
607 return 0;
608}
609
610static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
611 struct vm_area_struct *vma,
612 unsigned long address,
613 spinlock_t *ptl)
614{
615 pte_t *_pte;
David Rientjes338a16b2017-05-12 15:47:03 -0700616 for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
617 _pte++, page++, address += PAGE_SIZE) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700618 pte_t pteval = *_pte;
619 struct page *src_page;
620
621 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
622 clear_user_highpage(page, address);
623 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
624 if (is_zero_pfn(pte_pfn(pteval))) {
625 /*
626 * ptl mostly unnecessary.
627 */
628 spin_lock(ptl);
629 /*
630 * paravirt calls inside pte_clear here are
631 * superfluous.
632 */
633 pte_clear(vma->vm_mm, address, _pte);
634 spin_unlock(ptl);
635 }
636 } else {
637 src_page = pte_page(pteval);
638 copy_user_highpage(page, src_page, address, vma);
639 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
640 release_pte_page(src_page);
641 /*
642 * ptl mostly unnecessary, but preempt has to
643 * be disabled to update the per-cpu stats
644 * inside page_remove_rmap().
645 */
646 spin_lock(ptl);
647 /*
648 * paravirt calls inside pte_clear here are
649 * superfluous.
650 */
651 pte_clear(vma->vm_mm, address, _pte);
652 page_remove_rmap(src_page, false);
653 spin_unlock(ptl);
654 free_page_and_swap_cache(src_page);
655 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700656 }
657}
658
659static void khugepaged_alloc_sleep(void)
660{
661 DEFINE_WAIT(wait);
662
663 add_wait_queue(&khugepaged_wait, &wait);
664 freezable_schedule_timeout_interruptible(
665 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
666 remove_wait_queue(&khugepaged_wait, &wait);
667}
668
669static int khugepaged_node_load[MAX_NUMNODES];
670
671static bool khugepaged_scan_abort(int nid)
672{
673 int i;
674
675 /*
Mel Gormana5f5f912016-07-28 15:46:32 -0700676 * If node_reclaim_mode is disabled, then no extra effort is made to
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700677 * allocate memory locally.
678 */
Mel Gormana5f5f912016-07-28 15:46:32 -0700679 if (!node_reclaim_mode)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700680 return false;
681
682 /* If there is a count for this node already, it must be acceptable */
683 if (khugepaged_node_load[nid])
684 return false;
685
686 for (i = 0; i < MAX_NUMNODES; i++) {
687 if (!khugepaged_node_load[i])
688 continue;
689 if (node_distance(nid, i) > RECLAIM_DISTANCE)
690 return true;
691 }
692 return false;
693}
694
695/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
696static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
697{
Vlastimil Babka25160352016-07-28 15:49:25 -0700698 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700699}
700
701#ifdef CONFIG_NUMA
702static int khugepaged_find_target_node(void)
703{
704 static int last_khugepaged_target_node = NUMA_NO_NODE;
705 int nid, target_node = 0, max_value = 0;
706
707 /* find first node with max normal pages hit */
708 for (nid = 0; nid < MAX_NUMNODES; nid++)
709 if (khugepaged_node_load[nid] > max_value) {
710 max_value = khugepaged_node_load[nid];
711 target_node = nid;
712 }
713
714 /* do some balance if several nodes have the same hit record */
715 if (target_node <= last_khugepaged_target_node)
716 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
717 nid++)
718 if (max_value == khugepaged_node_load[nid]) {
719 target_node = nid;
720 break;
721 }
722
723 last_khugepaged_target_node = target_node;
724 return target_node;
725}
726
727static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
728{
729 if (IS_ERR(*hpage)) {
730 if (!*wait)
731 return false;
732
733 *wait = false;
734 *hpage = NULL;
735 khugepaged_alloc_sleep();
736 } else if (*hpage) {
737 put_page(*hpage);
738 *hpage = NULL;
739 }
740
741 return true;
742}
743
744static struct page *
Kirill A. Shutemov988ddb72016-07-26 15:26:26 -0700745khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700746{
747 VM_BUG_ON_PAGE(*hpage, *hpage);
748
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700749 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
750 if (unlikely(!*hpage)) {
751 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
752 *hpage = ERR_PTR(-ENOMEM);
753 return NULL;
754 }
755
756 prep_transhuge_page(*hpage);
757 count_vm_event(THP_COLLAPSE_ALLOC);
758 return *hpage;
759}
760#else
761static int khugepaged_find_target_node(void)
762{
763 return 0;
764}
765
766static inline struct page *alloc_khugepaged_hugepage(void)
767{
768 struct page *page;
769
770 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
771 HPAGE_PMD_ORDER);
772 if (page)
773 prep_transhuge_page(page);
774 return page;
775}
776
777static struct page *khugepaged_alloc_hugepage(bool *wait)
778{
779 struct page *hpage;
780
781 do {
782 hpage = alloc_khugepaged_hugepage();
783 if (!hpage) {
784 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
785 if (!*wait)
786 return NULL;
787
788 *wait = false;
789 khugepaged_alloc_sleep();
790 } else
791 count_vm_event(THP_COLLAPSE_ALLOC);
792 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
793
794 return hpage;
795}
796
797static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
798{
799 if (!*hpage)
800 *hpage = khugepaged_alloc_hugepage(wait);
801
802 if (unlikely(!*hpage))
803 return false;
804
805 return true;
806}
807
808static struct page *
Kirill A. Shutemov988ddb72016-07-26 15:26:26 -0700809khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700810{
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700811 VM_BUG_ON(!*hpage);
812
813 return *hpage;
814}
815#endif
816
817static bool hugepage_vma_check(struct vm_area_struct *vma)
818{
819 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
Michal Hocko18600332017-07-10 15:48:02 -0700820 (vma->vm_flags & VM_NOHUGEPAGE) ||
821 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700822 return false;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -0700823 if (shmem_file(vma->vm_file)) {
Kirill A. Shutemove496cf32016-07-26 15:26:35 -0700824 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
825 return false;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -0700826 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
827 HPAGE_PMD_NR);
828 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700829 if (!vma->anon_vma || vma->vm_ops)
830 return false;
831 if (is_vma_temporary_stack(vma))
832 return false;
833 return !(vma->vm_flags & VM_NO_KHUGEPAGED);
834}
835
836/*
837 * If mmap_sem temporarily dropped, revalidate vma
838 * before taking mmap_sem.
839 * Return 0 if succeeds, otherwise return none-zero
840 * value (scan code).
841 */
842
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700843static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
844 struct vm_area_struct **vmap)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700845{
846 struct vm_area_struct *vma;
847 unsigned long hstart, hend;
848
849 if (unlikely(khugepaged_test_exit(mm)))
850 return SCAN_ANY_PROCESS;
851
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700852 *vmap = vma = find_vma(mm, address);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700853 if (!vma)
854 return SCAN_VMA_NULL;
855
856 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
857 hend = vma->vm_end & HPAGE_PMD_MASK;
858 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
859 return SCAN_ADDRESS_RANGE;
860 if (!hugepage_vma_check(vma))
861 return SCAN_VMA_CHECK;
862 return 0;
863}
864
865/*
866 * Bring missing pages in from swap, to complete THP collapse.
867 * Only done if khugepaged_scan_pmd believes it is worthwhile.
868 *
869 * Called and returns without pte mapped or spinlocks held,
870 * but with mmap_sem held to protect against vma changes.
871 */
872
873static bool __collapse_huge_page_swapin(struct mm_struct *mm,
874 struct vm_area_struct *vma,
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700875 unsigned long address, pmd_t *pmd,
876 int referenced)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700877{
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700878 int swapped_in = 0, ret = 0;
Jan Kara82b0f8c2016-12-14 15:06:58 -0800879 struct vm_fault vmf = {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700880 .vma = vma,
881 .address = address,
882 .flags = FAULT_FLAG_ALLOW_RETRY,
883 .pmd = pmd,
Jan Kara0721ec82016-12-14 15:07:04 -0800884 .pgoff = linear_page_index(vma, address),
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700885 };
886
Ebru Akagunduz982785c2016-09-19 14:44:04 -0700887 /* we only decide to swapin, if there is enough young ptes */
888 if (referenced < HPAGE_PMD_NR/2) {
889 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
890 return false;
891 }
Jan Kara82b0f8c2016-12-14 15:06:58 -0800892 vmf.pte = pte_offset_map(pmd, address);
893 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
894 vmf.pte++, vmf.address += PAGE_SIZE) {
Jan Kara29943022016-12-14 15:07:16 -0800895 vmf.orig_pte = *vmf.pte;
896 if (!is_swap_pte(vmf.orig_pte))
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700897 continue;
898 swapped_in++;
Jan Kara29943022016-12-14 15:07:16 -0800899 ret = do_swap_page(&vmf);
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700900
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700901 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
902 if (ret & VM_FAULT_RETRY) {
903 down_read(&mm->mmap_sem);
Jan Kara82b0f8c2016-12-14 15:06:58 -0800904 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {
Ebru Akagunduz47f863e2016-07-26 15:26:43 -0700905 /* vma is no longer available, don't continue to swapin */
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700906 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700907 return false;
Ebru Akagunduz47f863e2016-07-26 15:26:43 -0700908 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700909 /* check if the pmd is still valid */
SeongJae Park835152a2017-05-12 15:46:38 -0700910 if (mm_find_pmd(mm, address) != pmd) {
911 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700912 return false;
SeongJae Park835152a2017-05-12 15:46:38 -0700913 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700914 }
915 if (ret & VM_FAULT_ERROR) {
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700916 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700917 return false;
918 }
919 /* pte is unmapped now, we need to map it */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800920 vmf.pte = pte_offset_map(pmd, vmf.address);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700921 }
Jan Kara82b0f8c2016-12-14 15:06:58 -0800922 vmf.pte--;
923 pte_unmap(vmf.pte);
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700924 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700925 return true;
926}
927
928static void collapse_huge_page(struct mm_struct *mm,
929 unsigned long address,
930 struct page **hpage,
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700931 int node, int referenced)
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700932{
933 pmd_t *pmd, _pmd;
934 pte_t *pte;
935 pgtable_t pgtable;
936 struct page *new_page;
937 spinlock_t *pmd_ptl, *pte_ptl;
938 int isolated = 0, result = 0;
939 struct mem_cgroup *memcg;
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700940 struct vm_area_struct *vma;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700941 unsigned long mmun_start; /* For mmu_notifiers */
942 unsigned long mmun_end; /* For mmu_notifiers */
943 gfp_t gfp;
944
945 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
946
947 /* Only allocate from the target node */
Michal Hocko41b61672017-01-10 16:57:42 -0800948 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700949
Kirill A. Shutemov988ddb72016-07-26 15:26:26 -0700950 /*
951 * Before allocating the hugepage, release the mmap_sem read lock.
952 * The allocation can take potentially a long time if it involves
953 * sync compaction, and we do not need to hold the mmap_sem during
954 * that. We will recheck the vma after taking it again in write mode.
955 */
956 up_read(&mm->mmap_sem);
957 new_page = khugepaged_alloc_page(hpage, gfp, node);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700958 if (!new_page) {
959 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
960 goto out_nolock;
961 }
962
963 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
964 result = SCAN_CGROUP_CHARGE_FAIL;
965 goto out_nolock;
966 }
967
968 down_read(&mm->mmap_sem);
Kirill A. Shutemovc131f752016-09-19 14:44:01 -0700969 result = hugepage_vma_revalidate(mm, address, &vma);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700970 if (result) {
971 mem_cgroup_cancel_charge(new_page, memcg, true);
972 up_read(&mm->mmap_sem);
973 goto out_nolock;
974 }
975
976 pmd = mm_find_pmd(mm, address);
977 if (!pmd) {
978 result = SCAN_PMD_NULL;
979 mem_cgroup_cancel_charge(new_page, memcg, true);
980 up_read(&mm->mmap_sem);
981 goto out_nolock;
982 }
983
984 /*
985 * __collapse_huge_page_swapin always returns with mmap_sem locked.
Ebru Akagunduz47f863e2016-07-26 15:26:43 -0700986 * If it fails, we release mmap_sem and jump out_nolock.
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700987 * Continuing to collapse causes inconsistency.
988 */
Ebru Akagunduz0db501f2016-07-26 15:26:46 -0700989 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -0700990 mem_cgroup_cancel_charge(new_page, memcg, true);
991 up_read(&mm->mmap_sem);
992 goto out_nolock;
993 }
994
995 up_read(&mm->mmap_sem);
996 /*
997 * Prevent all access to pagetables with the exception of
998 * gup_fast later handled by the ptep_clear_flush and the VM
999 * handled by the anon_vma lock + PG_lock.
1000 */
1001 down_write(&mm->mmap_sem);
Kirill A. Shutemovc131f752016-09-19 14:44:01 -07001002 result = hugepage_vma_revalidate(mm, address, &vma);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001003 if (result)
1004 goto out;
1005 /* check if the pmd is still valid */
1006 if (mm_find_pmd(mm, address) != pmd)
1007 goto out;
1008
1009 anon_vma_lock_write(vma->anon_vma);
1010
1011 pte = pte_offset_map(pmd, address);
1012 pte_ptl = pte_lockptr(mm, pmd);
1013
1014 mmun_start = address;
1015 mmun_end = address + HPAGE_PMD_SIZE;
1016 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1017 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1018 /*
1019 * After this gup_fast can't run anymore. This also removes
1020 * any huge TLB entry from the CPU so we won't allow
1021 * huge and small TLB entries for the same virtual address
1022 * to avoid the risk of CPU bugs in that area.
1023 */
1024 _pmd = pmdp_collapse_flush(vma, address, pmd);
1025 spin_unlock(pmd_ptl);
1026 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1027
1028 spin_lock(pte_ptl);
1029 isolated = __collapse_huge_page_isolate(vma, address, pte);
1030 spin_unlock(pte_ptl);
1031
1032 if (unlikely(!isolated)) {
1033 pte_unmap(pte);
1034 spin_lock(pmd_ptl);
1035 BUG_ON(!pmd_none(*pmd));
1036 /*
1037 * We can only use set_pmd_at when establishing
1038 * hugepmds and never for establishing regular pmds that
1039 * points to regular pagetables. Use pmd_populate for that
1040 */
1041 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1042 spin_unlock(pmd_ptl);
1043 anon_vma_unlock_write(vma->anon_vma);
1044 result = SCAN_FAIL;
1045 goto out;
1046 }
1047
1048 /*
1049 * All pages are isolated and locked so anon_vma rmap
1050 * can't run anymore.
1051 */
1052 anon_vma_unlock_write(vma->anon_vma);
1053
1054 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
1055 pte_unmap(pte);
1056 __SetPageUptodate(new_page);
1057 pgtable = pmd_pgtable(_pmd);
1058
1059 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1060 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1061
1062 /*
1063 * spin_lock() below is not the equivalent of smp_wmb(), so
1064 * this is needed to avoid the copy_huge_page writes to become
1065 * visible after the set_pmd_at() write.
1066 */
1067 smp_wmb();
1068
1069 spin_lock(pmd_ptl);
1070 BUG_ON(!pmd_none(*pmd));
1071 page_add_new_anon_rmap(new_page, vma, address, true);
1072 mem_cgroup_commit_charge(new_page, memcg, false, true);
1073 lru_cache_add_active_or_unevictable(new_page, vma);
1074 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1075 set_pmd_at(mm, address, pmd, _pmd);
1076 update_mmu_cache_pmd(vma, address, pmd);
1077 spin_unlock(pmd_ptl);
1078
1079 *hpage = NULL;
1080
1081 khugepaged_pages_collapsed++;
1082 result = SCAN_SUCCEED;
1083out_up_write:
1084 up_write(&mm->mmap_sem);
1085out_nolock:
1086 trace_mm_collapse_huge_page(mm, isolated, result);
1087 return;
1088out:
1089 mem_cgroup_cancel_charge(new_page, memcg, true);
1090 goto out_up_write;
1091}
1092
1093static int khugepaged_scan_pmd(struct mm_struct *mm,
1094 struct vm_area_struct *vma,
1095 unsigned long address,
1096 struct page **hpage)
1097{
1098 pmd_t *pmd;
1099 pte_t *pte, *_pte;
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001100 int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001101 struct page *page = NULL;
1102 unsigned long _address;
1103 spinlock_t *ptl;
1104 int node = NUMA_NO_NODE, unmapped = 0;
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001105 bool writable = false;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001106
1107 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1108
1109 pmd = mm_find_pmd(mm, address);
1110 if (!pmd) {
1111 result = SCAN_PMD_NULL;
1112 goto out;
1113 }
1114
1115 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1116 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1117 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1118 _pte++, _address += PAGE_SIZE) {
1119 pte_t pteval = *_pte;
1120 if (is_swap_pte(pteval)) {
1121 if (++unmapped <= khugepaged_max_ptes_swap) {
1122 continue;
1123 } else {
1124 result = SCAN_EXCEED_SWAP_PTE;
1125 goto out_unmap;
1126 }
1127 }
1128 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1129 if (!userfaultfd_armed(vma) &&
1130 ++none_or_zero <= khugepaged_max_ptes_none) {
1131 continue;
1132 } else {
1133 result = SCAN_EXCEED_NONE_PTE;
1134 goto out_unmap;
1135 }
1136 }
1137 if (!pte_present(pteval)) {
1138 result = SCAN_PTE_NON_PRESENT;
1139 goto out_unmap;
1140 }
1141 if (pte_write(pteval))
1142 writable = true;
1143
1144 page = vm_normal_page(vma, _address, pteval);
1145 if (unlikely(!page)) {
1146 result = SCAN_PAGE_NULL;
1147 goto out_unmap;
1148 }
1149
1150 /* TODO: teach khugepaged to collapse THP mapped with pte */
1151 if (PageCompound(page)) {
1152 result = SCAN_PAGE_COMPOUND;
1153 goto out_unmap;
1154 }
1155
1156 /*
1157 * Record which node the original page is from and save this
1158 * information to khugepaged_node_load[].
1159 * Khupaged will allocate hugepage from the node has the max
1160 * hit record.
1161 */
1162 node = page_to_nid(page);
1163 if (khugepaged_scan_abort(node)) {
1164 result = SCAN_SCAN_ABORT;
1165 goto out_unmap;
1166 }
1167 khugepaged_node_load[node]++;
1168 if (!PageLRU(page)) {
1169 result = SCAN_PAGE_LRU;
1170 goto out_unmap;
1171 }
1172 if (PageLocked(page)) {
1173 result = SCAN_PAGE_LOCK;
1174 goto out_unmap;
1175 }
1176 if (!PageAnon(page)) {
1177 result = SCAN_PAGE_ANON;
1178 goto out_unmap;
1179 }
1180
1181 /*
1182 * cannot use mapcount: can't collapse if there's a gup pin.
1183 * The page must only be referenced by the scanned process
1184 * and page swap cache.
1185 */
Minchan Kim2948be52017-05-03 14:53:35 -07001186 if (page_count(page) != 1 + PageSwapCache(page)) {
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001187 result = SCAN_PAGE_COUNT;
1188 goto out_unmap;
1189 }
1190 if (pte_young(pteval) ||
1191 page_is_young(page) || PageReferenced(page) ||
1192 mmu_notifier_test_young(vma->vm_mm, address))
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001193 referenced++;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001194 }
1195 if (writable) {
1196 if (referenced) {
1197 result = SCAN_SUCCEED;
1198 ret = 1;
1199 } else {
Ebru Akagunduz0db501f2016-07-26 15:26:46 -07001200 result = SCAN_LACK_REFERENCED_PAGE;
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001201 }
1202 } else {
1203 result = SCAN_PAGE_RO;
1204 }
1205out_unmap:
1206 pte_unmap_unlock(pte, ptl);
1207 if (ret) {
1208 node = khugepaged_find_target_node();
1209 /* collapse_huge_page will return with the mmap_sem released */
Kirill A. Shutemovc131f752016-09-19 14:44:01 -07001210 collapse_huge_page(mm, address, hpage, node, referenced);
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001211 }
1212out:
1213 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1214 none_or_zero, result, unmapped);
1215 return ret;
1216}
1217
1218static void collect_mm_slot(struct mm_slot *mm_slot)
1219{
1220 struct mm_struct *mm = mm_slot->mm;
1221
1222 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1223
1224 if (khugepaged_test_exit(mm)) {
1225 /* free mm_slot */
1226 hash_del(&mm_slot->hash);
1227 list_del(&mm_slot->mm_node);
1228
1229 /*
1230 * Not strictly needed because the mm exited already.
1231 *
1232 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1233 */
1234
1235 /* khugepaged_mm_lock actually not necessary for the below */
1236 free_mm_slot(mm_slot);
1237 mmdrop(mm);
1238 }
1239}
1240
Kirill A. Shutemove496cf32016-07-26 15:26:35 -07001241#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001242static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1243{
1244 struct vm_area_struct *vma;
1245 unsigned long addr;
1246 pmd_t *pmd, _pmd;
1247
1248 i_mmap_lock_write(mapping);
1249 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1250 /* probably overkill */
1251 if (vma->anon_vma)
1252 continue;
1253 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1254 if (addr & ~HPAGE_PMD_MASK)
1255 continue;
1256 if (vma->vm_end < addr + HPAGE_PMD_SIZE)
1257 continue;
1258 pmd = mm_find_pmd(vma->vm_mm, addr);
1259 if (!pmd)
1260 continue;
1261 /*
1262 * We need exclusive mmap_sem to retract page table.
1263 * If trylock fails we would end up with pte-mapped THP after
1264 * re-fault. Not ideal, but it's more important to not disturb
1265 * the system too much.
1266 */
1267 if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
1268 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
1269 /* assume page table is clear */
1270 _pmd = pmdp_collapse_flush(vma, addr, pmd);
1271 spin_unlock(ptl);
1272 up_write(&vma->vm_mm->mmap_sem);
Kirill A. Shutemovc4812902017-11-15 17:35:37 -08001273 mm_dec_nr_ptes(vma->vm_mm);
Aneesh Kumar K.Vd670ffd2017-01-10 16:57:18 -08001274 pte_free(vma->vm_mm, pmd_pgtable(_pmd));
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001275 }
1276 }
1277 i_mmap_unlock_write(mapping);
1278}
1279
1280/**
1281 * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
1282 *
1283 * Basic scheme is simple, details are more complex:
1284 * - allocate and freeze a new huge page;
1285 * - scan over radix tree replacing old pages the new one
1286 * + swap in pages if necessary;
1287 * + fill in gaps;
1288 * + keep old pages around in case if rollback is required;
1289 * - if replacing succeed:
1290 * + copy data over;
1291 * + free old pages;
1292 * + unfreeze huge page;
1293 * - if replacing failed;
1294 * + put all pages back and unfreeze them;
1295 * + restore gaps in the radix-tree;
1296 * + free huge page;
1297 */
1298static void collapse_shmem(struct mm_struct *mm,
1299 struct address_space *mapping, pgoff_t start,
1300 struct page **hpage, int node)
1301{
1302 gfp_t gfp;
1303 struct page *page, *new_page, *tmp;
1304 struct mem_cgroup *memcg;
1305 pgoff_t index, end = start + HPAGE_PMD_NR;
1306 LIST_HEAD(pagelist);
1307 struct radix_tree_iter iter;
1308 void **slot;
1309 int nr_none = 0, result = SCAN_SUCCEED;
1310
1311 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1312
1313 /* Only allocate from the target node */
Michal Hocko41b61672017-01-10 16:57:42 -08001314 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001315
1316 new_page = khugepaged_alloc_page(hpage, gfp, node);
1317 if (!new_page) {
1318 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1319 goto out;
1320 }
1321
1322 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
1323 result = SCAN_CGROUP_CHARGE_FAIL;
1324 goto out;
1325 }
1326
1327 new_page->index = start;
1328 new_page->mapping = mapping;
1329 __SetPageSwapBacked(new_page);
1330 __SetPageLocked(new_page);
1331 BUG_ON(!page_ref_freeze(new_page, 1));
1332
1333
1334 /*
1335 * At this point the new_page is 'frozen' (page_count() is zero), locked
1336 * and not up-to-date. It's safe to insert it into radix tree, because
1337 * nobody would be able to map it or use it in other way until we
1338 * unfreeze it.
1339 */
1340
1341 index = start;
1342 spin_lock_irq(&mapping->tree_lock);
1343 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1344 int n = min(iter.index, end) - index;
1345
1346 /*
1347 * Handle holes in the radix tree: charge it from shmem and
1348 * insert relevant subpage of new_page into the radix-tree.
1349 */
1350 if (n && !shmem_charge(mapping->host, n)) {
1351 result = SCAN_FAIL;
1352 break;
1353 }
1354 nr_none += n;
1355 for (; index < min(iter.index, end); index++) {
1356 radix_tree_insert(&mapping->page_tree, index,
1357 new_page + (index % HPAGE_PMD_NR));
1358 }
1359
1360 /* We are done. */
1361 if (index >= end)
1362 break;
1363
1364 page = radix_tree_deref_slot_protected(slot,
1365 &mapping->tree_lock);
1366 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) {
1367 spin_unlock_irq(&mapping->tree_lock);
1368 /* swap in or instantiate fallocated page */
1369 if (shmem_getpage(mapping->host, index, &page,
1370 SGP_NOHUGE)) {
1371 result = SCAN_FAIL;
1372 goto tree_unlocked;
1373 }
1374 spin_lock_irq(&mapping->tree_lock);
1375 } else if (trylock_page(page)) {
1376 get_page(page);
1377 } else {
1378 result = SCAN_PAGE_LOCK;
1379 break;
1380 }
1381
1382 /*
1383 * The page must be locked, so we can drop the tree_lock
1384 * without racing with truncate.
1385 */
1386 VM_BUG_ON_PAGE(!PageLocked(page), page);
1387 VM_BUG_ON_PAGE(!PageUptodate(page), page);
1388 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1389
1390 if (page_mapping(page) != mapping) {
1391 result = SCAN_TRUNCATED;
1392 goto out_unlock;
1393 }
1394 spin_unlock_irq(&mapping->tree_lock);
1395
1396 if (isolate_lru_page(page)) {
1397 result = SCAN_DEL_PAGE_LRU;
1398 goto out_isolate_failed;
1399 }
1400
1401 if (page_mapped(page))
1402 unmap_mapping_range(mapping, index << PAGE_SHIFT,
1403 PAGE_SIZE, 0);
1404
1405 spin_lock_irq(&mapping->tree_lock);
1406
Johannes Weiner91a45f72016-12-12 16:43:32 -08001407 slot = radix_tree_lookup_slot(&mapping->page_tree, index);
1408 VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
1409 &mapping->tree_lock), page);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001410 VM_BUG_ON_PAGE(page_mapped(page), page);
1411
1412 /*
1413 * The page is expected to have page_count() == 3:
1414 * - we hold a pin on it;
1415 * - one reference from radix tree;
1416 * - one from isolate_lru_page;
1417 */
1418 if (!page_ref_freeze(page, 3)) {
1419 result = SCAN_PAGE_COUNT;
1420 goto out_lru;
1421 }
1422
1423 /*
1424 * Add the page to the list to be able to undo the collapse if
1425 * something go wrong.
1426 */
1427 list_add_tail(&page->lru, &pagelist);
1428
1429 /* Finally, replace with the new page. */
Johannes Weiner6d75f362016-12-12 16:43:43 -08001430 radix_tree_replace_slot(&mapping->page_tree, slot,
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001431 new_page + (index % HPAGE_PMD_NR));
1432
Matthew Wilcox148deab2016-12-14 15:08:49 -08001433 slot = radix_tree_iter_resume(slot, &iter);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001434 index++;
1435 continue;
1436out_lru:
1437 spin_unlock_irq(&mapping->tree_lock);
1438 putback_lru_page(page);
1439out_isolate_failed:
1440 unlock_page(page);
1441 put_page(page);
1442 goto tree_unlocked;
1443out_unlock:
1444 unlock_page(page);
1445 put_page(page);
1446 break;
1447 }
1448
1449 /*
1450 * Handle hole in radix tree at the end of the range.
1451 * This code only triggers if there's nothing in radix tree
1452 * beyond 'end'.
1453 */
1454 if (result == SCAN_SUCCEED && index < end) {
1455 int n = end - index;
1456
1457 if (!shmem_charge(mapping->host, n)) {
1458 result = SCAN_FAIL;
1459 goto tree_locked;
1460 }
1461
1462 for (; index < end; index++) {
1463 radix_tree_insert(&mapping->page_tree, index,
1464 new_page + (index % HPAGE_PMD_NR));
1465 }
1466 nr_none += n;
1467 }
1468
1469tree_locked:
1470 spin_unlock_irq(&mapping->tree_lock);
1471tree_unlocked:
1472
1473 if (result == SCAN_SUCCEED) {
1474 unsigned long flags;
1475 struct zone *zone = page_zone(new_page);
1476
1477 /*
1478 * Replacing old pages with new one has succeed, now we need to
1479 * copy the content and free old pages.
1480 */
1481 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
1482 copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
1483 page);
1484 list_del(&page->lru);
1485 unlock_page(page);
1486 page_ref_unfreeze(page, 1);
1487 page->mapping = NULL;
1488 ClearPageActive(page);
1489 ClearPageUnevictable(page);
1490 put_page(page);
1491 }
1492
1493 local_irq_save(flags);
Mel Gorman11fb9982016-07-28 15:46:20 -07001494 __inc_node_page_state(new_page, NR_SHMEM_THPS);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001495 if (nr_none) {
Mel Gorman11fb9982016-07-28 15:46:20 -07001496 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
1497 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001498 }
1499 local_irq_restore(flags);
1500
1501 /*
1502 * Remove pte page tables, so we can re-faulti
1503 * the page as huge.
1504 */
1505 retract_page_tables(mapping, start);
1506
1507 /* Everything is ready, let's unfreeze the new_page */
1508 set_page_dirty(new_page);
1509 SetPageUptodate(new_page);
1510 page_ref_unfreeze(new_page, HPAGE_PMD_NR);
1511 mem_cgroup_commit_charge(new_page, memcg, false, true);
1512 lru_cache_add_anon(new_page);
1513 unlock_page(new_page);
1514
1515 *hpage = NULL;
1516 } else {
1517 /* Something went wrong: rollback changes to the radix-tree */
1518 shmem_uncharge(mapping->host, nr_none);
1519 spin_lock_irq(&mapping->tree_lock);
1520 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
1521 start) {
1522 if (iter.index >= end)
1523 break;
1524 page = list_first_entry_or_null(&pagelist,
1525 struct page, lru);
1526 if (!page || iter.index < page->index) {
1527 if (!nr_none)
1528 break;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001529 nr_none--;
Johannes Weiner59749e62016-12-12 16:43:35 -08001530 /* Put holes back where they were */
1531 radix_tree_delete(&mapping->page_tree,
1532 iter.index);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001533 continue;
1534 }
1535
1536 VM_BUG_ON_PAGE(page->index != iter.index, page);
1537
1538 /* Unfreeze the page. */
1539 list_del(&page->lru);
1540 page_ref_unfreeze(page, 2);
Johannes Weiner6d75f362016-12-12 16:43:43 -08001541 radix_tree_replace_slot(&mapping->page_tree,
1542 slot, page);
Matthew Wilcox148deab2016-12-14 15:08:49 -08001543 slot = radix_tree_iter_resume(slot, &iter);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001544 spin_unlock_irq(&mapping->tree_lock);
1545 putback_lru_page(page);
1546 unlock_page(page);
1547 spin_lock_irq(&mapping->tree_lock);
1548 }
1549 VM_BUG_ON(nr_none);
1550 spin_unlock_irq(&mapping->tree_lock);
1551
1552 /* Unfreeze new_page, caller would take care about freeing it */
1553 page_ref_unfreeze(new_page, 1);
1554 mem_cgroup_cancel_charge(new_page, memcg, true);
1555 unlock_page(new_page);
1556 new_page->mapping = NULL;
1557 }
1558out:
1559 VM_BUG_ON(!list_empty(&pagelist));
1560 /* TODO: tracepoints */
1561}
1562
1563static void khugepaged_scan_shmem(struct mm_struct *mm,
1564 struct address_space *mapping,
1565 pgoff_t start, struct page **hpage)
1566{
1567 struct page *page = NULL;
1568 struct radix_tree_iter iter;
1569 void **slot;
1570 int present, swap;
1571 int node = NUMA_NO_NODE;
1572 int result = SCAN_SUCCEED;
1573
1574 present = 0;
1575 swap = 0;
1576 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1577 rcu_read_lock();
1578 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1579 if (iter.index >= start + HPAGE_PMD_NR)
1580 break;
1581
1582 page = radix_tree_deref_slot(slot);
1583 if (radix_tree_deref_retry(page)) {
1584 slot = radix_tree_iter_retry(&iter);
1585 continue;
1586 }
1587
1588 if (radix_tree_exception(page)) {
1589 if (++swap > khugepaged_max_ptes_swap) {
1590 result = SCAN_EXCEED_SWAP_PTE;
1591 break;
1592 }
1593 continue;
1594 }
1595
1596 if (PageTransCompound(page)) {
1597 result = SCAN_PAGE_COMPOUND;
1598 break;
1599 }
1600
1601 node = page_to_nid(page);
1602 if (khugepaged_scan_abort(node)) {
1603 result = SCAN_SCAN_ABORT;
1604 break;
1605 }
1606 khugepaged_node_load[node]++;
1607
1608 if (!PageLRU(page)) {
1609 result = SCAN_PAGE_LRU;
1610 break;
1611 }
1612
1613 if (page_count(page) != 1 + page_mapcount(page)) {
1614 result = SCAN_PAGE_COUNT;
1615 break;
1616 }
1617
1618 /*
1619 * We probably should check if the page is referenced here, but
1620 * nobody would transfer pte_young() to PageReferenced() for us.
1621 * And rmap walk here is just too costly...
1622 */
1623
1624 present++;
1625
1626 if (need_resched()) {
Matthew Wilcox148deab2016-12-14 15:08:49 -08001627 slot = radix_tree_iter_resume(slot, &iter);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001628 cond_resched_rcu();
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001629 }
1630 }
1631 rcu_read_unlock();
1632
1633 if (result == SCAN_SUCCEED) {
1634 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
1635 result = SCAN_EXCEED_NONE_PTE;
1636 } else {
1637 node = khugepaged_find_target_node();
1638 collapse_shmem(mm, mapping, start, hpage, node);
1639 }
1640 }
1641
1642 /* TODO: tracepoints */
1643}
1644#else
1645static void khugepaged_scan_shmem(struct mm_struct *mm,
1646 struct address_space *mapping,
1647 pgoff_t start, struct page **hpage)
1648{
1649 BUILD_BUG();
1650}
1651#endif
1652
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001653static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1654 struct page **hpage)
1655 __releases(&khugepaged_mm_lock)
1656 __acquires(&khugepaged_mm_lock)
1657{
1658 struct mm_slot *mm_slot;
1659 struct mm_struct *mm;
1660 struct vm_area_struct *vma;
1661 int progress = 0;
1662
1663 VM_BUG_ON(!pages);
1664 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1665
1666 if (khugepaged_scan.mm_slot)
1667 mm_slot = khugepaged_scan.mm_slot;
1668 else {
1669 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1670 struct mm_slot, mm_node);
1671 khugepaged_scan.address = 0;
1672 khugepaged_scan.mm_slot = mm_slot;
1673 }
1674 spin_unlock(&khugepaged_mm_lock);
1675
1676 mm = mm_slot->mm;
1677 down_read(&mm->mmap_sem);
1678 if (unlikely(khugepaged_test_exit(mm)))
1679 vma = NULL;
1680 else
1681 vma = find_vma(mm, khugepaged_scan.address);
1682
1683 progress++;
1684 for (; vma; vma = vma->vm_next) {
1685 unsigned long hstart, hend;
1686
1687 cond_resched();
1688 if (unlikely(khugepaged_test_exit(mm))) {
1689 progress++;
1690 break;
1691 }
1692 if (!hugepage_vma_check(vma)) {
1693skip:
1694 progress++;
1695 continue;
1696 }
1697 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1698 hend = vma->vm_end & HPAGE_PMD_MASK;
1699 if (hstart >= hend)
1700 goto skip;
1701 if (khugepaged_scan.address > hend)
1702 goto skip;
1703 if (khugepaged_scan.address < hstart)
1704 khugepaged_scan.address = hstart;
1705 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1706
1707 while (khugepaged_scan.address < hend) {
1708 int ret;
1709 cond_resched();
1710 if (unlikely(khugepaged_test_exit(mm)))
1711 goto breakouterloop;
1712
1713 VM_BUG_ON(khugepaged_scan.address < hstart ||
1714 khugepaged_scan.address + HPAGE_PMD_SIZE >
1715 hend);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001716 if (shmem_file(vma->vm_file)) {
Kirill A. Shutemove496cf32016-07-26 15:26:35 -07001717 struct file *file;
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001718 pgoff_t pgoff = linear_page_index(vma,
1719 khugepaged_scan.address);
Kirill A. Shutemove496cf32016-07-26 15:26:35 -07001720 if (!shmem_huge_enabled(vma))
1721 goto skip;
1722 file = get_file(vma->vm_file);
Kirill A. Shutemovf3f0e1d2016-07-26 15:26:32 -07001723 up_read(&mm->mmap_sem);
1724 ret = 1;
1725 khugepaged_scan_shmem(mm, file->f_mapping,
1726 pgoff, hpage);
1727 fput(file);
1728 } else {
1729 ret = khugepaged_scan_pmd(mm, vma,
1730 khugepaged_scan.address,
1731 hpage);
1732 }
Kirill A. Shutemovb46e7562016-07-26 15:26:24 -07001733 /* move to next address */
1734 khugepaged_scan.address += HPAGE_PMD_SIZE;
1735 progress += HPAGE_PMD_NR;
1736 if (ret)
1737 /* we released mmap_sem so break loop */
1738 goto breakouterloop_mmap_sem;
1739 if (progress >= pages)
1740 goto breakouterloop;
1741 }
1742 }
1743breakouterloop:
1744 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1745breakouterloop_mmap_sem:
1746
1747 spin_lock(&khugepaged_mm_lock);
1748 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1749 /*
1750 * Release the current mm_slot if this mm is about to die, or
1751 * if we scanned all vmas of this mm.
1752 */
1753 if (khugepaged_test_exit(mm) || !vma) {
1754 /*
1755 * Make sure that if mm_users is reaching zero while
1756 * khugepaged runs here, khugepaged_exit will find
1757 * mm_slot not pointing to the exiting mm.
1758 */
1759 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1760 khugepaged_scan.mm_slot = list_entry(
1761 mm_slot->mm_node.next,
1762 struct mm_slot, mm_node);
1763 khugepaged_scan.address = 0;
1764 } else {
1765 khugepaged_scan.mm_slot = NULL;
1766 khugepaged_full_scans++;
1767 }
1768
1769 collect_mm_slot(mm_slot);
1770 }
1771
1772 return progress;
1773}
1774
1775static int khugepaged_has_work(void)
1776{
1777 return !list_empty(&khugepaged_scan.mm_head) &&
1778 khugepaged_enabled();
1779}
1780
1781static int khugepaged_wait_event(void)
1782{
1783 return !list_empty(&khugepaged_scan.mm_head) ||
1784 kthread_should_stop();
1785}
1786
1787static void khugepaged_do_scan(void)
1788{
1789 struct page *hpage = NULL;
1790 unsigned int progress = 0, pass_through_head = 0;
1791 unsigned int pages = khugepaged_pages_to_scan;
1792 bool wait = true;
1793
1794 barrier(); /* write khugepaged_pages_to_scan to local stack */
1795
1796 while (progress < pages) {
1797 if (!khugepaged_prealloc_page(&hpage, &wait))
1798 break;
1799
1800 cond_resched();
1801
1802 if (unlikely(kthread_should_stop() || try_to_freeze()))
1803 break;
1804
1805 spin_lock(&khugepaged_mm_lock);
1806 if (!khugepaged_scan.mm_slot)
1807 pass_through_head++;
1808 if (khugepaged_has_work() &&
1809 pass_through_head < 2)
1810 progress += khugepaged_scan_mm_slot(pages - progress,
1811 &hpage);
1812 else
1813 progress = pages;
1814 spin_unlock(&khugepaged_mm_lock);
1815 }
1816
1817 if (!IS_ERR_OR_NULL(hpage))
1818 put_page(hpage);
1819}
1820
1821static bool khugepaged_should_wakeup(void)
1822{
1823 return kthread_should_stop() ||
1824 time_after_eq(jiffies, khugepaged_sleep_expire);
1825}
1826
1827static void khugepaged_wait_work(void)
1828{
1829 if (khugepaged_has_work()) {
1830 const unsigned long scan_sleep_jiffies =
1831 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
1832
1833 if (!scan_sleep_jiffies)
1834 return;
1835
1836 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
1837 wait_event_freezable_timeout(khugepaged_wait,
1838 khugepaged_should_wakeup(),
1839 scan_sleep_jiffies);
1840 return;
1841 }
1842
1843 if (khugepaged_enabled())
1844 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
1845}
1846
1847static int khugepaged(void *none)
1848{
1849 struct mm_slot *mm_slot;
1850
1851 set_freezable();
1852 set_user_nice(current, MAX_NICE);
1853
1854 while (!kthread_should_stop()) {
1855 khugepaged_do_scan();
1856 khugepaged_wait_work();
1857 }
1858
1859 spin_lock(&khugepaged_mm_lock);
1860 mm_slot = khugepaged_scan.mm_slot;
1861 khugepaged_scan.mm_slot = NULL;
1862 if (mm_slot)
1863 collect_mm_slot(mm_slot);
1864 spin_unlock(&khugepaged_mm_lock);
1865 return 0;
1866}
1867
1868static void set_recommended_min_free_kbytes(void)
1869{
1870 struct zone *zone;
1871 int nr_zones = 0;
1872 unsigned long recommended_min;
1873
1874 for_each_populated_zone(zone)
1875 nr_zones++;
1876
1877 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1878 recommended_min = pageblock_nr_pages * nr_zones * 2;
1879
1880 /*
1881 * Make sure that on average at least two pageblocks are almost free
1882 * of another type, one for a migratetype to fall back to and a
1883 * second to avoid subsequent fallbacks of other types There are 3
1884 * MIGRATE_TYPES we care about.
1885 */
1886 recommended_min += pageblock_nr_pages * nr_zones *
1887 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
1888
1889 /* don't ever allow to reserve more than 5% of the lowmem */
1890 recommended_min = min(recommended_min,
1891 (unsigned long) nr_free_buffer_pages() / 20);
1892 recommended_min <<= (PAGE_SHIFT-10);
1893
1894 if (recommended_min > min_free_kbytes) {
1895 if (user_min_free_kbytes >= 0)
1896 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1897 min_free_kbytes, recommended_min);
1898
1899 min_free_kbytes = recommended_min;
1900 }
1901 setup_per_zone_wmarks();
1902}
1903
1904int start_stop_khugepaged(void)
1905{
1906 static struct task_struct *khugepaged_thread __read_mostly;
1907 static DEFINE_MUTEX(khugepaged_mutex);
1908 int err = 0;
1909
1910 mutex_lock(&khugepaged_mutex);
1911 if (khugepaged_enabled()) {
1912 if (!khugepaged_thread)
1913 khugepaged_thread = kthread_run(khugepaged, NULL,
1914 "khugepaged");
1915 if (IS_ERR(khugepaged_thread)) {
1916 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1917 err = PTR_ERR(khugepaged_thread);
1918 khugepaged_thread = NULL;
1919 goto fail;
1920 }
1921
1922 if (!list_empty(&khugepaged_scan.mm_head))
1923 wake_up_interruptible(&khugepaged_wait);
1924
1925 set_recommended_min_free_kbytes();
1926 } else if (khugepaged_thread) {
1927 kthread_stop(khugepaged_thread);
1928 khugepaged_thread = NULL;
1929 }
1930fail:
1931 mutex_unlock(&khugepaged_mutex);
1932 return err;
1933}