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1/*
2 * Copyright (C) 2009 Red Hat, Inc.
3 *
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
6 */
7
8#include <linux/mm.h>
9#include <linux/sched.h>
10#include <linux/highmem.h>
11#include <linux/hugetlb.h>
12#include <linux/mmu_notifier.h>
13#include <linux/rmap.h>
14#include <linux/swap.h>
15#include <linux/mm_inline.h>
16#include <linux/kthread.h>
17#include <linux/khugepaged.h>
18#include <linux/freezer.h>
19#include <linux/mman.h>
20#include <asm/tlb.h>
21#include <asm/pgalloc.h>
22#include "internal.h"
23
24/*
25 * By default transparent hugepage support is enabled for all mappings
26 * and khugepaged scans all mappings. Defrag is only invoked by
27 * khugepaged hugepage allocations and by page faults inside
28 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
29 * allocations.
30 */
31unsigned long transparent_hugepage_flags __read_mostly =
32#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
33 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
34#endif
35#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
37#endif
38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
40
41/* default scan 8*512 pte (or vmas) every 30 second */
42static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
43static unsigned int khugepaged_pages_collapsed;
44static unsigned int khugepaged_full_scans;
45static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
46/* during fragmentation poll the hugepage allocator once every minute */
47static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
48static struct task_struct *khugepaged_thread __read_mostly;
49static DEFINE_MUTEX(khugepaged_mutex);
50static DEFINE_SPINLOCK(khugepaged_mm_lock);
51static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
52/*
53 * default collapse hugepages if there is at least one pte mapped like
54 * it would have happened if the vma was large enough during page
55 * fault.
56 */
57static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
58
59static int khugepaged(void *none);
60static int mm_slots_hash_init(void);
61static int khugepaged_slab_init(void);
62static void khugepaged_slab_free(void);
63
64#define MM_SLOTS_HASH_HEADS 1024
65static struct hlist_head *mm_slots_hash __read_mostly;
66static struct kmem_cache *mm_slot_cache __read_mostly;
67
68/**
69 * struct mm_slot - hash lookup from mm to mm_slot
70 * @hash: hash collision list
71 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
72 * @mm: the mm that this information is valid for
73 */
74struct mm_slot {
75 struct hlist_node hash;
76 struct list_head mm_node;
77 struct mm_struct *mm;
78};
79
80/**
81 * struct khugepaged_scan - cursor for scanning
82 * @mm_head: the head of the mm list to scan
83 * @mm_slot: the current mm_slot we are scanning
84 * @address: the next address inside that to be scanned
85 *
86 * There is only the one khugepaged_scan instance of this cursor structure.
87 */
88struct khugepaged_scan {
89 struct list_head mm_head;
90 struct mm_slot *mm_slot;
91 unsigned long address;
92};
93static struct khugepaged_scan khugepaged_scan = {
94 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
95};
96
97
98static int set_recommended_min_free_kbytes(void)
99{
100 struct zone *zone;
101 int nr_zones = 0;
102 unsigned long recommended_min;
103 extern int min_free_kbytes;
104
105 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
106 &transparent_hugepage_flags) &&
107 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
108 &transparent_hugepage_flags))
109 return 0;
110
111 for_each_populated_zone(zone)
112 nr_zones++;
113
114 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
115 recommended_min = pageblock_nr_pages * nr_zones * 2;
116
117 /*
118 * Make sure that on average at least two pageblocks are almost free
119 * of another type, one for a migratetype to fall back to and a
120 * second to avoid subsequent fallbacks of other types There are 3
121 * MIGRATE_TYPES we care about.
122 */
123 recommended_min += pageblock_nr_pages * nr_zones *
124 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
125
126 /* don't ever allow to reserve more than 5% of the lowmem */
127 recommended_min = min(recommended_min,
128 (unsigned long) nr_free_buffer_pages() / 20);
129 recommended_min <<= (PAGE_SHIFT-10);
130
131 if (recommended_min > min_free_kbytes)
132 min_free_kbytes = recommended_min;
133 setup_per_zone_wmarks();
134 return 0;
135}
136late_initcall(set_recommended_min_free_kbytes);
137
138static int start_khugepaged(void)
139{
140 int err = 0;
141 if (khugepaged_enabled()) {
142 int wakeup;
143 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
144 err = -ENOMEM;
145 goto out;
146 }
147 mutex_lock(&khugepaged_mutex);
148 if (!khugepaged_thread)
149 khugepaged_thread = kthread_run(khugepaged, NULL,
150 "khugepaged");
151 if (unlikely(IS_ERR(khugepaged_thread))) {
152 printk(KERN_ERR
153 "khugepaged: kthread_run(khugepaged) failed\n");
154 err = PTR_ERR(khugepaged_thread);
155 khugepaged_thread = NULL;
156 }
157 wakeup = !list_empty(&khugepaged_scan.mm_head);
158 mutex_unlock(&khugepaged_mutex);
159 if (wakeup)
160 wake_up_interruptible(&khugepaged_wait);
161
162 set_recommended_min_free_kbytes();
163 } else
164 /* wakeup to exit */
165 wake_up_interruptible(&khugepaged_wait);
166out:
167 return err;
168}
169
170#ifdef CONFIG_SYSFS
171
172static ssize_t double_flag_show(struct kobject *kobj,
173 struct kobj_attribute *attr, char *buf,
174 enum transparent_hugepage_flag enabled,
175 enum transparent_hugepage_flag req_madv)
176{
177 if (test_bit(enabled, &transparent_hugepage_flags)) {
178 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
179 return sprintf(buf, "[always] madvise never\n");
180 } else if (test_bit(req_madv, &transparent_hugepage_flags))
181 return sprintf(buf, "always [madvise] never\n");
182 else
183 return sprintf(buf, "always madvise [never]\n");
184}
185static ssize_t double_flag_store(struct kobject *kobj,
186 struct kobj_attribute *attr,
187 const char *buf, size_t count,
188 enum transparent_hugepage_flag enabled,
189 enum transparent_hugepage_flag req_madv)
190{
191 if (!memcmp("always", buf,
192 min(sizeof("always")-1, count))) {
193 set_bit(enabled, &transparent_hugepage_flags);
194 clear_bit(req_madv, &transparent_hugepage_flags);
195 } else if (!memcmp("madvise", buf,
196 min(sizeof("madvise")-1, count))) {
197 clear_bit(enabled, &transparent_hugepage_flags);
198 set_bit(req_madv, &transparent_hugepage_flags);
199 } else if (!memcmp("never", buf,
200 min(sizeof("never")-1, count))) {
201 clear_bit(enabled, &transparent_hugepage_flags);
202 clear_bit(req_madv, &transparent_hugepage_flags);
203 } else
204 return -EINVAL;
205
206 return count;
207}
208
209static ssize_t enabled_show(struct kobject *kobj,
210 struct kobj_attribute *attr, char *buf)
211{
212 return double_flag_show(kobj, attr, buf,
213 TRANSPARENT_HUGEPAGE_FLAG,
214 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
215}
216static ssize_t enabled_store(struct kobject *kobj,
217 struct kobj_attribute *attr,
218 const char *buf, size_t count)
219{
220 ssize_t ret;
221
222 ret = double_flag_store(kobj, attr, buf, count,
223 TRANSPARENT_HUGEPAGE_FLAG,
224 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
225
226 if (ret > 0) {
227 int err = start_khugepaged();
228 if (err)
229 ret = err;
230 }
231
232 if (ret > 0 &&
233 (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
234 &transparent_hugepage_flags) ||
235 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
236 &transparent_hugepage_flags)))
237 set_recommended_min_free_kbytes();
238
239 return ret;
240}
241static struct kobj_attribute enabled_attr =
242 __ATTR(enabled, 0644, enabled_show, enabled_store);
243
244static ssize_t single_flag_show(struct kobject *kobj,
245 struct kobj_attribute *attr, char *buf,
246 enum transparent_hugepage_flag flag)
247{
248 return sprintf(buf, "%d\n",
249 !!test_bit(flag, &transparent_hugepage_flags));
250}
251
252static ssize_t single_flag_store(struct kobject *kobj,
253 struct kobj_attribute *attr,
254 const char *buf, size_t count,
255 enum transparent_hugepage_flag flag)
256{
257 unsigned long value;
258 int ret;
259
260 ret = kstrtoul(buf, 10, &value);
261 if (ret < 0)
262 return ret;
263 if (value > 1)
264 return -EINVAL;
265
266 if (value)
267 set_bit(flag, &transparent_hugepage_flags);
268 else
269 clear_bit(flag, &transparent_hugepage_flags);
270
271 return count;
272}
273
274/*
275 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
276 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
277 * memory just to allocate one more hugepage.
278 */
279static ssize_t defrag_show(struct kobject *kobj,
280 struct kobj_attribute *attr, char *buf)
281{
282 return double_flag_show(kobj, attr, buf,
283 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
284 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
285}
286static ssize_t defrag_store(struct kobject *kobj,
287 struct kobj_attribute *attr,
288 const char *buf, size_t count)
289{
290 return double_flag_store(kobj, attr, buf, count,
291 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
292 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
293}
294static struct kobj_attribute defrag_attr =
295 __ATTR(defrag, 0644, defrag_show, defrag_store);
296
297#ifdef CONFIG_DEBUG_VM
298static ssize_t debug_cow_show(struct kobject *kobj,
299 struct kobj_attribute *attr, char *buf)
300{
301 return single_flag_show(kobj, attr, buf,
302 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
303}
304static ssize_t debug_cow_store(struct kobject *kobj,
305 struct kobj_attribute *attr,
306 const char *buf, size_t count)
307{
308 return single_flag_store(kobj, attr, buf, count,
309 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
310}
311static struct kobj_attribute debug_cow_attr =
312 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
313#endif /* CONFIG_DEBUG_VM */
314
315static struct attribute *hugepage_attr[] = {
316 &enabled_attr.attr,
317 &defrag_attr.attr,
318#ifdef CONFIG_DEBUG_VM
319 &debug_cow_attr.attr,
320#endif
321 NULL,
322};
323
324static struct attribute_group hugepage_attr_group = {
325 .attrs = hugepage_attr,
326};
327
328static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
329 struct kobj_attribute *attr,
330 char *buf)
331{
332 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
333}
334
335static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
336 struct kobj_attribute *attr,
337 const char *buf, size_t count)
338{
339 unsigned long msecs;
340 int err;
341
342 err = strict_strtoul(buf, 10, &msecs);
343 if (err || msecs > UINT_MAX)
344 return -EINVAL;
345
346 khugepaged_scan_sleep_millisecs = msecs;
347 wake_up_interruptible(&khugepaged_wait);
348
349 return count;
350}
351static struct kobj_attribute scan_sleep_millisecs_attr =
352 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
353 scan_sleep_millisecs_store);
354
355static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
356 struct kobj_attribute *attr,
357 char *buf)
358{
359 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
360}
361
362static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
363 struct kobj_attribute *attr,
364 const char *buf, size_t count)
365{
366 unsigned long msecs;
367 int err;
368
369 err = strict_strtoul(buf, 10, &msecs);
370 if (err || msecs > UINT_MAX)
371 return -EINVAL;
372
373 khugepaged_alloc_sleep_millisecs = msecs;
374 wake_up_interruptible(&khugepaged_wait);
375
376 return count;
377}
378static struct kobj_attribute alloc_sleep_millisecs_attr =
379 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
380 alloc_sleep_millisecs_store);
381
382static ssize_t pages_to_scan_show(struct kobject *kobj,
383 struct kobj_attribute *attr,
384 char *buf)
385{
386 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
387}
388static ssize_t pages_to_scan_store(struct kobject *kobj,
389 struct kobj_attribute *attr,
390 const char *buf, size_t count)
391{
392 int err;
393 unsigned long pages;
394
395 err = strict_strtoul(buf, 10, &pages);
396 if (err || !pages || pages > UINT_MAX)
397 return -EINVAL;
398
399 khugepaged_pages_to_scan = pages;
400
401 return count;
402}
403static struct kobj_attribute pages_to_scan_attr =
404 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
405 pages_to_scan_store);
406
407static ssize_t pages_collapsed_show(struct kobject *kobj,
408 struct kobj_attribute *attr,
409 char *buf)
410{
411 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
412}
413static struct kobj_attribute pages_collapsed_attr =
414 __ATTR_RO(pages_collapsed);
415
416static ssize_t full_scans_show(struct kobject *kobj,
417 struct kobj_attribute *attr,
418 char *buf)
419{
420 return sprintf(buf, "%u\n", khugepaged_full_scans);
421}
422static struct kobj_attribute full_scans_attr =
423 __ATTR_RO(full_scans);
424
425static ssize_t khugepaged_defrag_show(struct kobject *kobj,
426 struct kobj_attribute *attr, char *buf)
427{
428 return single_flag_show(kobj, attr, buf,
429 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
430}
431static ssize_t khugepaged_defrag_store(struct kobject *kobj,
432 struct kobj_attribute *attr,
433 const char *buf, size_t count)
434{
435 return single_flag_store(kobj, attr, buf, count,
436 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
437}
438static struct kobj_attribute khugepaged_defrag_attr =
439 __ATTR(defrag, 0644, khugepaged_defrag_show,
440 khugepaged_defrag_store);
441
442/*
443 * max_ptes_none controls if khugepaged should collapse hugepages over
444 * any unmapped ptes in turn potentially increasing the memory
445 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
446 * reduce the available free memory in the system as it
447 * runs. Increasing max_ptes_none will instead potentially reduce the
448 * free memory in the system during the khugepaged scan.
449 */
450static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
451 struct kobj_attribute *attr,
452 char *buf)
453{
454 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
455}
456static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
457 struct kobj_attribute *attr,
458 const char *buf, size_t count)
459{
460 int err;
461 unsigned long max_ptes_none;
462
463 err = strict_strtoul(buf, 10, &max_ptes_none);
464 if (err || max_ptes_none > HPAGE_PMD_NR-1)
465 return -EINVAL;
466
467 khugepaged_max_ptes_none = max_ptes_none;
468
469 return count;
470}
471static struct kobj_attribute khugepaged_max_ptes_none_attr =
472 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
473 khugepaged_max_ptes_none_store);
474
475static struct attribute *khugepaged_attr[] = {
476 &khugepaged_defrag_attr.attr,
477 &khugepaged_max_ptes_none_attr.attr,
478 &pages_to_scan_attr.attr,
479 &pages_collapsed_attr.attr,
480 &full_scans_attr.attr,
481 &scan_sleep_millisecs_attr.attr,
482 &alloc_sleep_millisecs_attr.attr,
483 NULL,
484};
485
486static struct attribute_group khugepaged_attr_group = {
487 .attrs = khugepaged_attr,
488 .name = "khugepaged",
489};
490
491static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
492{
493 int err;
494
495 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
496 if (unlikely(!*hugepage_kobj)) {
497 printk(KERN_ERR "hugepage: failed kobject create\n");
498 return -ENOMEM;
499 }
500
501 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
502 if (err) {
503 printk(KERN_ERR "hugepage: failed register hugeage group\n");
504 goto delete_obj;
505 }
506
507 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
508 if (err) {
509 printk(KERN_ERR "hugepage: failed register hugeage group\n");
510 goto remove_hp_group;
511 }
512
513 return 0;
514
515remove_hp_group:
516 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
517delete_obj:
518 kobject_put(*hugepage_kobj);
519 return err;
520}
521
522static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
523{
524 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
525 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
526 kobject_put(hugepage_kobj);
527}
528#else
529static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
530{
531 return 0;
532}
533
534static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
535{
536}
537#endif /* CONFIG_SYSFS */
538
539static int __init hugepage_init(void)
540{
541 int err;
542 struct kobject *hugepage_kobj;
543
544 if (!has_transparent_hugepage()) {
545 transparent_hugepage_flags = 0;
546 return -EINVAL;
547 }
548
549 err = hugepage_init_sysfs(&hugepage_kobj);
550 if (err)
551 return err;
552
553 err = khugepaged_slab_init();
554 if (err)
555 goto out;
556
557 err = mm_slots_hash_init();
558 if (err) {
559 khugepaged_slab_free();
560 goto out;
561 }
562
563 /*
564 * By default disable transparent hugepages on smaller systems,
565 * where the extra memory used could hurt more than TLB overhead
566 * is likely to save. The admin can still enable it through /sys.
567 */
568 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
569 transparent_hugepage_flags = 0;
570
571 start_khugepaged();
572
573 set_recommended_min_free_kbytes();
574
575 return 0;
576out:
577 hugepage_exit_sysfs(hugepage_kobj);
578 return err;
579}
580module_init(hugepage_init)
581
582static int __init setup_transparent_hugepage(char *str)
583{
584 int ret = 0;
585 if (!str)
586 goto out;
587 if (!strcmp(str, "always")) {
588 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
589 &transparent_hugepage_flags);
590 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
591 &transparent_hugepage_flags);
592 ret = 1;
593 } else if (!strcmp(str, "madvise")) {
594 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
595 &transparent_hugepage_flags);
596 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
597 &transparent_hugepage_flags);
598 ret = 1;
599 } else if (!strcmp(str, "never")) {
600 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
601 &transparent_hugepage_flags);
602 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
603 &transparent_hugepage_flags);
604 ret = 1;
605 }
606out:
607 if (!ret)
608 printk(KERN_WARNING
609 "transparent_hugepage= cannot parse, ignored\n");
610 return ret;
611}
612__setup("transparent_hugepage=", setup_transparent_hugepage);
613
614static void prepare_pmd_huge_pte(pgtable_t pgtable,
615 struct mm_struct *mm)
616{
617 assert_spin_locked(&mm->page_table_lock);
618
619 /* FIFO */
620 if (!mm->pmd_huge_pte)
621 INIT_LIST_HEAD(&pgtable->lru);
622 else
623 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
624 mm->pmd_huge_pte = pgtable;
625}
626
627static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
628{
629 if (likely(vma->vm_flags & VM_WRITE))
630 pmd = pmd_mkwrite(pmd);
631 return pmd;
632}
633
634static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
635 struct vm_area_struct *vma,
636 unsigned long haddr, pmd_t *pmd,
637 struct page *page)
638{
639 pgtable_t pgtable;
640
641 VM_BUG_ON(!PageCompound(page));
642 pgtable = pte_alloc_one(mm, haddr);
643 if (unlikely(!pgtable))
644 return VM_FAULT_OOM;
645
646 clear_huge_page(page, haddr, HPAGE_PMD_NR);
647 __SetPageUptodate(page);
648
649 spin_lock(&mm->page_table_lock);
650 if (unlikely(!pmd_none(*pmd))) {
651 spin_unlock(&mm->page_table_lock);
652 mem_cgroup_uncharge_page(page);
653 put_page(page);
654 pte_free(mm, pgtable);
655 } else {
656 pmd_t entry;
657 entry = mk_pmd(page, vma->vm_page_prot);
658 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
659 entry = pmd_mkhuge(entry);
660 /*
661 * The spinlocking to take the lru_lock inside
662 * page_add_new_anon_rmap() acts as a full memory
663 * barrier to be sure clear_huge_page writes become
664 * visible after the set_pmd_at() write.
665 */
666 page_add_new_anon_rmap(page, vma, haddr);
667 set_pmd_at(mm, haddr, pmd, entry);
668 prepare_pmd_huge_pte(pgtable, mm);
669 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
670 mm->nr_ptes++;
671 spin_unlock(&mm->page_table_lock);
672 }
673
674 return 0;
675}
676
677static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
678{
679 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
680}
681
682static inline struct page *alloc_hugepage_vma(int defrag,
683 struct vm_area_struct *vma,
684 unsigned long haddr, int nd,
685 gfp_t extra_gfp)
686{
687 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
688 HPAGE_PMD_ORDER, vma, haddr, nd);
689}
690
691#ifndef CONFIG_NUMA
692static inline struct page *alloc_hugepage(int defrag)
693{
694 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
695 HPAGE_PMD_ORDER);
696}
697#endif
698
699int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
700 unsigned long address, pmd_t *pmd,
701 unsigned int flags)
702{
703 struct page *page;
704 unsigned long haddr = address & HPAGE_PMD_MASK;
705 pte_t *pte;
706
707 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
708 if (unlikely(anon_vma_prepare(vma)))
709 return VM_FAULT_OOM;
710 if (unlikely(khugepaged_enter(vma)))
711 return VM_FAULT_OOM;
712 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
713 vma, haddr, numa_node_id(), 0);
714 if (unlikely(!page)) {
715 count_vm_event(THP_FAULT_FALLBACK);
716 goto out;
717 }
718 count_vm_event(THP_FAULT_ALLOC);
719 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
720 put_page(page);
721 goto out;
722 }
723 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
724 page))) {
725 mem_cgroup_uncharge_page(page);
726 put_page(page);
727 goto out;
728 }
729
730 return 0;
731 }
732out:
733 /*
734 * Use __pte_alloc instead of pte_alloc_map, because we can't
735 * run pte_offset_map on the pmd, if an huge pmd could
736 * materialize from under us from a different thread.
737 */
738 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
739 return VM_FAULT_OOM;
740 /* if an huge pmd materialized from under us just retry later */
741 if (unlikely(pmd_trans_huge(*pmd)))
742 return 0;
743 /*
744 * A regular pmd is established and it can't morph into a huge pmd
745 * from under us anymore at this point because we hold the mmap_sem
746 * read mode and khugepaged takes it in write mode. So now it's
747 * safe to run pte_offset_map().
748 */
749 pte = pte_offset_map(pmd, address);
750 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
751}
752
753int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
754 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
755 struct vm_area_struct *vma)
756{
757 struct page *src_page;
758 pmd_t pmd;
759 pgtable_t pgtable;
760 int ret;
761
762 ret = -ENOMEM;
763 pgtable = pte_alloc_one(dst_mm, addr);
764 if (unlikely(!pgtable))
765 goto out;
766
767 spin_lock(&dst_mm->page_table_lock);
768 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
769
770 ret = -EAGAIN;
771 pmd = *src_pmd;
772 if (unlikely(!pmd_trans_huge(pmd))) {
773 pte_free(dst_mm, pgtable);
774 goto out_unlock;
775 }
776 if (unlikely(pmd_trans_splitting(pmd))) {
777 /* split huge page running from under us */
778 spin_unlock(&src_mm->page_table_lock);
779 spin_unlock(&dst_mm->page_table_lock);
780 pte_free(dst_mm, pgtable);
781
782 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
783 goto out;
784 }
785 src_page = pmd_page(pmd);
786 VM_BUG_ON(!PageHead(src_page));
787 get_page(src_page);
788 page_dup_rmap(src_page);
789 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
790
791 pmdp_set_wrprotect(src_mm, addr, src_pmd);
792 pmd = pmd_mkold(pmd_wrprotect(pmd));
793 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
794 prepare_pmd_huge_pte(pgtable, dst_mm);
795 dst_mm->nr_ptes++;
796
797 ret = 0;
798out_unlock:
799 spin_unlock(&src_mm->page_table_lock);
800 spin_unlock(&dst_mm->page_table_lock);
801out:
802 return ret;
803}
804
805/* no "address" argument so destroys page coloring of some arch */
806pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
807{
808 pgtable_t pgtable;
809
810 assert_spin_locked(&mm->page_table_lock);
811
812 /* FIFO */
813 pgtable = mm->pmd_huge_pte;
814 if (list_empty(&pgtable->lru))
815 mm->pmd_huge_pte = NULL;
816 else {
817 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
818 struct page, lru);
819 list_del(&pgtable->lru);
820 }
821 return pgtable;
822}
823
824static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
825 struct vm_area_struct *vma,
826 unsigned long address,
827 pmd_t *pmd, pmd_t orig_pmd,
828 struct page *page,
829 unsigned long haddr)
830{
831 pgtable_t pgtable;
832 pmd_t _pmd;
833 int ret = 0, i;
834 struct page **pages;
835
836 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
837 GFP_KERNEL);
838 if (unlikely(!pages)) {
839 ret |= VM_FAULT_OOM;
840 goto out;
841 }
842
843 for (i = 0; i < HPAGE_PMD_NR; i++) {
844 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
845 __GFP_OTHER_NODE,
846 vma, address, page_to_nid(page));
847 if (unlikely(!pages[i] ||
848 mem_cgroup_newpage_charge(pages[i], mm,
849 GFP_KERNEL))) {
850 if (pages[i])
851 put_page(pages[i]);
852 mem_cgroup_uncharge_start();
853 while (--i >= 0) {
854 mem_cgroup_uncharge_page(pages[i]);
855 put_page(pages[i]);
856 }
857 mem_cgroup_uncharge_end();
858 kfree(pages);
859 ret |= VM_FAULT_OOM;
860 goto out;
861 }
862 }
863
864 for (i = 0; i < HPAGE_PMD_NR; i++) {
865 copy_user_highpage(pages[i], page + i,
866 haddr + PAGE_SIZE * i, vma);
867 __SetPageUptodate(pages[i]);
868 cond_resched();
869 }
870
871 spin_lock(&mm->page_table_lock);
872 if (unlikely(!pmd_same(*pmd, orig_pmd)))
873 goto out_free_pages;
874 VM_BUG_ON(!PageHead(page));
875
876 pmdp_clear_flush_notify(vma, haddr, pmd);
877 /* leave pmd empty until pte is filled */
878
879 pgtable = get_pmd_huge_pte(mm);
880 pmd_populate(mm, &_pmd, pgtable);
881
882 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
883 pte_t *pte, entry;
884 entry = mk_pte(pages[i], vma->vm_page_prot);
885 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
886 page_add_new_anon_rmap(pages[i], vma, haddr);
887 pte = pte_offset_map(&_pmd, haddr);
888 VM_BUG_ON(!pte_none(*pte));
889 set_pte_at(mm, haddr, pte, entry);
890 pte_unmap(pte);
891 }
892 kfree(pages);
893
894 smp_wmb(); /* make pte visible before pmd */
895 pmd_populate(mm, pmd, pgtable);
896 page_remove_rmap(page);
897 spin_unlock(&mm->page_table_lock);
898
899 ret |= VM_FAULT_WRITE;
900 put_page(page);
901
902out:
903 return ret;
904
905out_free_pages:
906 spin_unlock(&mm->page_table_lock);
907 mem_cgroup_uncharge_start();
908 for (i = 0; i < HPAGE_PMD_NR; i++) {
909 mem_cgroup_uncharge_page(pages[i]);
910 put_page(pages[i]);
911 }
912 mem_cgroup_uncharge_end();
913 kfree(pages);
914 goto out;
915}
916
917int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
918 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
919{
920 int ret = 0;
921 struct page *page, *new_page;
922 unsigned long haddr;
923
924 VM_BUG_ON(!vma->anon_vma);
925 spin_lock(&mm->page_table_lock);
926 if (unlikely(!pmd_same(*pmd, orig_pmd)))
927 goto out_unlock;
928
929 page = pmd_page(orig_pmd);
930 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
931 haddr = address & HPAGE_PMD_MASK;
932 if (page_mapcount(page) == 1) {
933 pmd_t entry;
934 entry = pmd_mkyoung(orig_pmd);
935 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
936 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
937 update_mmu_cache(vma, address, entry);
938 ret |= VM_FAULT_WRITE;
939 goto out_unlock;
940 }
941 get_page(page);
942 spin_unlock(&mm->page_table_lock);
943
944 if (transparent_hugepage_enabled(vma) &&
945 !transparent_hugepage_debug_cow())
946 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
947 vma, haddr, numa_node_id(), 0);
948 else
949 new_page = NULL;
950
951 if (unlikely(!new_page)) {
952 count_vm_event(THP_FAULT_FALLBACK);
953 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
954 pmd, orig_pmd, page, haddr);
955 if (ret & VM_FAULT_OOM)
956 split_huge_page(page);
957 put_page(page);
958 goto out;
959 }
960 count_vm_event(THP_FAULT_ALLOC);
961
962 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
963 put_page(new_page);
964 split_huge_page(page);
965 put_page(page);
966 ret |= VM_FAULT_OOM;
967 goto out;
968 }
969
970 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
971 __SetPageUptodate(new_page);
972
973 spin_lock(&mm->page_table_lock);
974 put_page(page);
975 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
976 spin_unlock(&mm->page_table_lock);
977 mem_cgroup_uncharge_page(new_page);
978 put_page(new_page);
979 goto out;
980 } else {
981 pmd_t entry;
982 VM_BUG_ON(!PageHead(page));
983 entry = mk_pmd(new_page, vma->vm_page_prot);
984 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
985 entry = pmd_mkhuge(entry);
986 pmdp_clear_flush_notify(vma, haddr, pmd);
987 page_add_new_anon_rmap(new_page, vma, haddr);
988 set_pmd_at(mm, haddr, pmd, entry);
989 update_mmu_cache(vma, address, entry);
990 page_remove_rmap(page);
991 put_page(page);
992 ret |= VM_FAULT_WRITE;
993 }
994out_unlock:
995 spin_unlock(&mm->page_table_lock);
996out:
997 return ret;
998}
999
1000struct page *follow_trans_huge_pmd(struct mm_struct *mm,
1001 unsigned long addr,
1002 pmd_t *pmd,
1003 unsigned int flags)
1004{
1005 struct page *page = NULL;
1006
1007 assert_spin_locked(&mm->page_table_lock);
1008
1009 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1010 goto out;
1011
1012 page = pmd_page(*pmd);
1013 VM_BUG_ON(!PageHead(page));
1014 if (flags & FOLL_TOUCH) {
1015 pmd_t _pmd;
1016 /*
1017 * We should set the dirty bit only for FOLL_WRITE but
1018 * for now the dirty bit in the pmd is meaningless.
1019 * And if the dirty bit will become meaningful and
1020 * we'll only set it with FOLL_WRITE, an atomic
1021 * set_bit will be required on the pmd to set the
1022 * young bit, instead of the current set_pmd_at.
1023 */
1024 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1025 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1026 }
1027 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1028 VM_BUG_ON(!PageCompound(page));
1029 if (flags & FOLL_GET)
1030 get_page_foll(page);
1031
1032out:
1033 return page;
1034}
1035
1036int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1037 pmd_t *pmd, unsigned long addr)
1038{
1039 int ret = 0;
1040
1041 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1042 struct page *page;
1043 pgtable_t pgtable;
1044 pgtable = get_pmd_huge_pte(tlb->mm);
1045 page = pmd_page(*pmd);
1046 pmd_clear(pmd);
1047 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1048 page_remove_rmap(page);
1049 VM_BUG_ON(page_mapcount(page) < 0);
1050 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1051 VM_BUG_ON(!PageHead(page));
1052 tlb->mm->nr_ptes--;
1053 spin_unlock(&tlb->mm->page_table_lock);
1054 tlb_remove_page(tlb, page);
1055 pte_free(tlb->mm, pgtable);
1056 ret = 1;
1057 }
1058 return ret;
1059}
1060
1061int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1062 unsigned long addr, unsigned long end,
1063 unsigned char *vec)
1064{
1065 int ret = 0;
1066
1067 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1068 /*
1069 * All logical pages in the range are present
1070 * if backed by a huge page.
1071 */
1072 spin_unlock(&vma->vm_mm->page_table_lock);
1073 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1074 ret = 1;
1075 }
1076
1077 return ret;
1078}
1079
1080int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1081 unsigned long old_addr,
1082 unsigned long new_addr, unsigned long old_end,
1083 pmd_t *old_pmd, pmd_t *new_pmd)
1084{
1085 int ret = 0;
1086 pmd_t pmd;
1087
1088 struct mm_struct *mm = vma->vm_mm;
1089
1090 if ((old_addr & ~HPAGE_PMD_MASK) ||
1091 (new_addr & ~HPAGE_PMD_MASK) ||
1092 old_end - old_addr < HPAGE_PMD_SIZE ||
1093 (new_vma->vm_flags & VM_NOHUGEPAGE))
1094 goto out;
1095
1096 /*
1097 * The destination pmd shouldn't be established, free_pgtables()
1098 * should have release it.
1099 */
1100 if (WARN_ON(!pmd_none(*new_pmd))) {
1101 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1102 goto out;
1103 }
1104
1105 ret = __pmd_trans_huge_lock(old_pmd, vma);
1106 if (ret == 1) {
1107 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1108 VM_BUG_ON(!pmd_none(*new_pmd));
1109 set_pmd_at(mm, new_addr, new_pmd, pmd);
1110 spin_unlock(&mm->page_table_lock);
1111 }
1112out:
1113 return ret;
1114}
1115
1116int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1117 unsigned long addr, pgprot_t newprot)
1118{
1119 struct mm_struct *mm = vma->vm_mm;
1120 int ret = 0;
1121
1122 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1123 pmd_t entry;
1124 entry = pmdp_get_and_clear(mm, addr, pmd);
1125 entry = pmd_modify(entry, newprot);
1126 set_pmd_at(mm, addr, pmd, entry);
1127 spin_unlock(&vma->vm_mm->page_table_lock);
1128 ret = 1;
1129 }
1130
1131 return ret;
1132}
1133
1134/*
1135 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1136 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1137 *
1138 * Note that if it returns 1, this routine returns without unlocking page
1139 * table locks. So callers must unlock them.
1140 */
1141int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1142{
1143 spin_lock(&vma->vm_mm->page_table_lock);
1144 if (likely(pmd_trans_huge(*pmd))) {
1145 if (unlikely(pmd_trans_splitting(*pmd))) {
1146 spin_unlock(&vma->vm_mm->page_table_lock);
1147 wait_split_huge_page(vma->anon_vma, pmd);
1148 return -1;
1149 } else {
1150 /* Thp mapped by 'pmd' is stable, so we can
1151 * handle it as it is. */
1152 return 1;
1153 }
1154 }
1155 spin_unlock(&vma->vm_mm->page_table_lock);
1156 return 0;
1157}
1158
1159pmd_t *page_check_address_pmd(struct page *page,
1160 struct mm_struct *mm,
1161 unsigned long address,
1162 enum page_check_address_pmd_flag flag)
1163{
1164 pgd_t *pgd;
1165 pud_t *pud;
1166 pmd_t *pmd, *ret = NULL;
1167
1168 if (address & ~HPAGE_PMD_MASK)
1169 goto out;
1170
1171 pgd = pgd_offset(mm, address);
1172 if (!pgd_present(*pgd))
1173 goto out;
1174
1175 pud = pud_offset(pgd, address);
1176 if (!pud_present(*pud))
1177 goto out;
1178
1179 pmd = pmd_offset(pud, address);
1180 if (pmd_none(*pmd))
1181 goto out;
1182 if (pmd_page(*pmd) != page)
1183 goto out;
1184 /*
1185 * split_vma() may create temporary aliased mappings. There is
1186 * no risk as long as all huge pmd are found and have their
1187 * splitting bit set before __split_huge_page_refcount
1188 * runs. Finding the same huge pmd more than once during the
1189 * same rmap walk is not a problem.
1190 */
1191 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1192 pmd_trans_splitting(*pmd))
1193 goto out;
1194 if (pmd_trans_huge(*pmd)) {
1195 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1196 !pmd_trans_splitting(*pmd));
1197 ret = pmd;
1198 }
1199out:
1200 return ret;
1201}
1202
1203static int __split_huge_page_splitting(struct page *page,
1204 struct vm_area_struct *vma,
1205 unsigned long address)
1206{
1207 struct mm_struct *mm = vma->vm_mm;
1208 pmd_t *pmd;
1209 int ret = 0;
1210
1211 spin_lock(&mm->page_table_lock);
1212 pmd = page_check_address_pmd(page, mm, address,
1213 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1214 if (pmd) {
1215 /*
1216 * We can't temporarily set the pmd to null in order
1217 * to split it, the pmd must remain marked huge at all
1218 * times or the VM won't take the pmd_trans_huge paths
1219 * and it won't wait on the anon_vma->root->mutex to
1220 * serialize against split_huge_page*.
1221 */
1222 pmdp_splitting_flush_notify(vma, address, pmd);
1223 ret = 1;
1224 }
1225 spin_unlock(&mm->page_table_lock);
1226
1227 return ret;
1228}
1229
1230static void __split_huge_page_refcount(struct page *page)
1231{
1232 int i;
1233 struct zone *zone = page_zone(page);
1234 struct lruvec *lruvec;
1235 int tail_count = 0;
1236
1237 /* prevent PageLRU to go away from under us, and freeze lru stats */
1238 spin_lock_irq(&zone->lru_lock);
1239 lruvec = mem_cgroup_page_lruvec(page, zone);
1240
1241 compound_lock(page);
1242 /* complete memcg works before add pages to LRU */
1243 mem_cgroup_split_huge_fixup(page);
1244
1245 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1246 struct page *page_tail = page + i;
1247
1248 /* tail_page->_mapcount cannot change */
1249 BUG_ON(page_mapcount(page_tail) < 0);
1250 tail_count += page_mapcount(page_tail);
1251 /* check for overflow */
1252 BUG_ON(tail_count < 0);
1253 BUG_ON(atomic_read(&page_tail->_count) != 0);
1254 /*
1255 * tail_page->_count is zero and not changing from
1256 * under us. But get_page_unless_zero() may be running
1257 * from under us on the tail_page. If we used
1258 * atomic_set() below instead of atomic_add(), we
1259 * would then run atomic_set() concurrently with
1260 * get_page_unless_zero(), and atomic_set() is
1261 * implemented in C not using locked ops. spin_unlock
1262 * on x86 sometime uses locked ops because of PPro
1263 * errata 66, 92, so unless somebody can guarantee
1264 * atomic_set() here would be safe on all archs (and
1265 * not only on x86), it's safer to use atomic_add().
1266 */
1267 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1268 &page_tail->_count);
1269
1270 /* after clearing PageTail the gup refcount can be released */
1271 smp_mb();
1272
1273 /*
1274 * retain hwpoison flag of the poisoned tail page:
1275 * fix for the unsuitable process killed on Guest Machine(KVM)
1276 * by the memory-failure.
1277 */
1278 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1279 page_tail->flags |= (page->flags &
1280 ((1L << PG_referenced) |
1281 (1L << PG_swapbacked) |
1282 (1L << PG_mlocked) |
1283 (1L << PG_uptodate)));
1284 page_tail->flags |= (1L << PG_dirty);
1285
1286 /* clear PageTail before overwriting first_page */
1287 smp_wmb();
1288
1289 /*
1290 * __split_huge_page_splitting() already set the
1291 * splitting bit in all pmd that could map this
1292 * hugepage, that will ensure no CPU can alter the
1293 * mapcount on the head page. The mapcount is only
1294 * accounted in the head page and it has to be
1295 * transferred to all tail pages in the below code. So
1296 * for this code to be safe, the split the mapcount
1297 * can't change. But that doesn't mean userland can't
1298 * keep changing and reading the page contents while
1299 * we transfer the mapcount, so the pmd splitting
1300 * status is achieved setting a reserved bit in the
1301 * pmd, not by clearing the present bit.
1302 */
1303 page_tail->_mapcount = page->_mapcount;
1304
1305 BUG_ON(page_tail->mapping);
1306 page_tail->mapping = page->mapping;
1307
1308 page_tail->index = page->index + i;
1309
1310 BUG_ON(!PageAnon(page_tail));
1311 BUG_ON(!PageUptodate(page_tail));
1312 BUG_ON(!PageDirty(page_tail));
1313 BUG_ON(!PageSwapBacked(page_tail));
1314
1315 lru_add_page_tail(page, page_tail, lruvec);
1316 }
1317 atomic_sub(tail_count, &page->_count);
1318 BUG_ON(atomic_read(&page->_count) <= 0);
1319
1320 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1321 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1322
1323 ClearPageCompound(page);
1324 compound_unlock(page);
1325 spin_unlock_irq(&zone->lru_lock);
1326
1327 for (i = 1; i < HPAGE_PMD_NR; i++) {
1328 struct page *page_tail = page + i;
1329 BUG_ON(page_count(page_tail) <= 0);
1330 /*
1331 * Tail pages may be freed if there wasn't any mapping
1332 * like if add_to_swap() is running on a lru page that
1333 * had its mapping zapped. And freeing these pages
1334 * requires taking the lru_lock so we do the put_page
1335 * of the tail pages after the split is complete.
1336 */
1337 put_page(page_tail);
1338 }
1339
1340 /*
1341 * Only the head page (now become a regular page) is required
1342 * to be pinned by the caller.
1343 */
1344 BUG_ON(page_count(page) <= 0);
1345}
1346
1347static int __split_huge_page_map(struct page *page,
1348 struct vm_area_struct *vma,
1349 unsigned long address)
1350{
1351 struct mm_struct *mm = vma->vm_mm;
1352 pmd_t *pmd, _pmd;
1353 int ret = 0, i;
1354 pgtable_t pgtable;
1355 unsigned long haddr;
1356
1357 spin_lock(&mm->page_table_lock);
1358 pmd = page_check_address_pmd(page, mm, address,
1359 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1360 if (pmd) {
1361 pgtable = get_pmd_huge_pte(mm);
1362 pmd_populate(mm, &_pmd, pgtable);
1363
1364 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1365 i++, haddr += PAGE_SIZE) {
1366 pte_t *pte, entry;
1367 BUG_ON(PageCompound(page+i));
1368 entry = mk_pte(page + i, vma->vm_page_prot);
1369 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1370 if (!pmd_write(*pmd))
1371 entry = pte_wrprotect(entry);
1372 else
1373 BUG_ON(page_mapcount(page) != 1);
1374 if (!pmd_young(*pmd))
1375 entry = pte_mkold(entry);
1376 pte = pte_offset_map(&_pmd, haddr);
1377 BUG_ON(!pte_none(*pte));
1378 set_pte_at(mm, haddr, pte, entry);
1379 pte_unmap(pte);
1380 }
1381
1382 smp_wmb(); /* make pte visible before pmd */
1383 /*
1384 * Up to this point the pmd is present and huge and
1385 * userland has the whole access to the hugepage
1386 * during the split (which happens in place). If we
1387 * overwrite the pmd with the not-huge version
1388 * pointing to the pte here (which of course we could
1389 * if all CPUs were bug free), userland could trigger
1390 * a small page size TLB miss on the small sized TLB
1391 * while the hugepage TLB entry is still established
1392 * in the huge TLB. Some CPU doesn't like that. See
1393 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1394 * Erratum 383 on page 93. Intel should be safe but is
1395 * also warns that it's only safe if the permission
1396 * and cache attributes of the two entries loaded in
1397 * the two TLB is identical (which should be the case
1398 * here). But it is generally safer to never allow
1399 * small and huge TLB entries for the same virtual
1400 * address to be loaded simultaneously. So instead of
1401 * doing "pmd_populate(); flush_tlb_range();" we first
1402 * mark the current pmd notpresent (atomically because
1403 * here the pmd_trans_huge and pmd_trans_splitting
1404 * must remain set at all times on the pmd until the
1405 * split is complete for this pmd), then we flush the
1406 * SMP TLB and finally we write the non-huge version
1407 * of the pmd entry with pmd_populate.
1408 */
1409 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1410 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1411 pmd_populate(mm, pmd, pgtable);
1412 ret = 1;
1413 }
1414 spin_unlock(&mm->page_table_lock);
1415
1416 return ret;
1417}
1418
1419/* must be called with anon_vma->root->mutex hold */
1420static void __split_huge_page(struct page *page,
1421 struct anon_vma *anon_vma)
1422{
1423 int mapcount, mapcount2;
1424 struct anon_vma_chain *avc;
1425
1426 BUG_ON(!PageHead(page));
1427 BUG_ON(PageTail(page));
1428
1429 mapcount = 0;
1430 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1431 struct vm_area_struct *vma = avc->vma;
1432 unsigned long addr = vma_address(page, vma);
1433 BUG_ON(is_vma_temporary_stack(vma));
1434 if (addr == -EFAULT)
1435 continue;
1436 mapcount += __split_huge_page_splitting(page, vma, addr);
1437 }
1438 /*
1439 * It is critical that new vmas are added to the tail of the
1440 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1441 * and establishes a child pmd before
1442 * __split_huge_page_splitting() freezes the parent pmd (so if
1443 * we fail to prevent copy_huge_pmd() from running until the
1444 * whole __split_huge_page() is complete), we will still see
1445 * the newly established pmd of the child later during the
1446 * walk, to be able to set it as pmd_trans_splitting too.
1447 */
1448 if (mapcount != page_mapcount(page))
1449 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1450 mapcount, page_mapcount(page));
1451 BUG_ON(mapcount != page_mapcount(page));
1452
1453 __split_huge_page_refcount(page);
1454
1455 mapcount2 = 0;
1456 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1457 struct vm_area_struct *vma = avc->vma;
1458 unsigned long addr = vma_address(page, vma);
1459 BUG_ON(is_vma_temporary_stack(vma));
1460 if (addr == -EFAULT)
1461 continue;
1462 mapcount2 += __split_huge_page_map(page, vma, addr);
1463 }
1464 if (mapcount != mapcount2)
1465 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1466 mapcount, mapcount2, page_mapcount(page));
1467 BUG_ON(mapcount != mapcount2);
1468}
1469
1470int split_huge_page(struct page *page)
1471{
1472 struct anon_vma *anon_vma;
1473 int ret = 1;
1474
1475 BUG_ON(!PageAnon(page));
1476 anon_vma = page_lock_anon_vma(page);
1477 if (!anon_vma)
1478 goto out;
1479 ret = 0;
1480 if (!PageCompound(page))
1481 goto out_unlock;
1482
1483 BUG_ON(!PageSwapBacked(page));
1484 __split_huge_page(page, anon_vma);
1485 count_vm_event(THP_SPLIT);
1486
1487 BUG_ON(PageCompound(page));
1488out_unlock:
1489 page_unlock_anon_vma(anon_vma);
1490out:
1491 return ret;
1492}
1493
1494#define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1495 VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1496
1497int hugepage_madvise(struct vm_area_struct *vma,
1498 unsigned long *vm_flags, int advice)
1499{
1500 switch (advice) {
1501 case MADV_HUGEPAGE:
1502 /*
1503 * Be somewhat over-protective like KSM for now!
1504 */
1505 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1506 return -EINVAL;
1507 *vm_flags &= ~VM_NOHUGEPAGE;
1508 *vm_flags |= VM_HUGEPAGE;
1509 /*
1510 * If the vma become good for khugepaged to scan,
1511 * register it here without waiting a page fault that
1512 * may not happen any time soon.
1513 */
1514 if (unlikely(khugepaged_enter_vma_merge(vma)))
1515 return -ENOMEM;
1516 break;
1517 case MADV_NOHUGEPAGE:
1518 /*
1519 * Be somewhat over-protective like KSM for now!
1520 */
1521 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1522 return -EINVAL;
1523 *vm_flags &= ~VM_HUGEPAGE;
1524 *vm_flags |= VM_NOHUGEPAGE;
1525 /*
1526 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1527 * this vma even if we leave the mm registered in khugepaged if
1528 * it got registered before VM_NOHUGEPAGE was set.
1529 */
1530 break;
1531 }
1532
1533 return 0;
1534}
1535
1536static int __init khugepaged_slab_init(void)
1537{
1538 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1539 sizeof(struct mm_slot),
1540 __alignof__(struct mm_slot), 0, NULL);
1541 if (!mm_slot_cache)
1542 return -ENOMEM;
1543
1544 return 0;
1545}
1546
1547static void __init khugepaged_slab_free(void)
1548{
1549 kmem_cache_destroy(mm_slot_cache);
1550 mm_slot_cache = NULL;
1551}
1552
1553static inline struct mm_slot *alloc_mm_slot(void)
1554{
1555 if (!mm_slot_cache) /* initialization failed */
1556 return NULL;
1557 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1558}
1559
1560static inline void free_mm_slot(struct mm_slot *mm_slot)
1561{
1562 kmem_cache_free(mm_slot_cache, mm_slot);
1563}
1564
1565static int __init mm_slots_hash_init(void)
1566{
1567 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1568 GFP_KERNEL);
1569 if (!mm_slots_hash)
1570 return -ENOMEM;
1571 return 0;
1572}
1573
1574#if 0
1575static void __init mm_slots_hash_free(void)
1576{
1577 kfree(mm_slots_hash);
1578 mm_slots_hash = NULL;
1579}
1580#endif
1581
1582static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1583{
1584 struct mm_slot *mm_slot;
1585 struct hlist_head *bucket;
1586 struct hlist_node *node;
1587
1588 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1589 % MM_SLOTS_HASH_HEADS];
1590 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1591 if (mm == mm_slot->mm)
1592 return mm_slot;
1593 }
1594 return NULL;
1595}
1596
1597static void insert_to_mm_slots_hash(struct mm_struct *mm,
1598 struct mm_slot *mm_slot)
1599{
1600 struct hlist_head *bucket;
1601
1602 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1603 % MM_SLOTS_HASH_HEADS];
1604 mm_slot->mm = mm;
1605 hlist_add_head(&mm_slot->hash, bucket);
1606}
1607
1608static inline int khugepaged_test_exit(struct mm_struct *mm)
1609{
1610 return atomic_read(&mm->mm_users) == 0;
1611}
1612
1613int __khugepaged_enter(struct mm_struct *mm)
1614{
1615 struct mm_slot *mm_slot;
1616 int wakeup;
1617
1618 mm_slot = alloc_mm_slot();
1619 if (!mm_slot)
1620 return -ENOMEM;
1621
1622 /* __khugepaged_exit() must not run from under us */
1623 VM_BUG_ON(khugepaged_test_exit(mm));
1624 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1625 free_mm_slot(mm_slot);
1626 return 0;
1627 }
1628
1629 spin_lock(&khugepaged_mm_lock);
1630 insert_to_mm_slots_hash(mm, mm_slot);
1631 /*
1632 * Insert just behind the scanning cursor, to let the area settle
1633 * down a little.
1634 */
1635 wakeup = list_empty(&khugepaged_scan.mm_head);
1636 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1637 spin_unlock(&khugepaged_mm_lock);
1638
1639 atomic_inc(&mm->mm_count);
1640 if (wakeup)
1641 wake_up_interruptible(&khugepaged_wait);
1642
1643 return 0;
1644}
1645
1646int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1647{
1648 unsigned long hstart, hend;
1649 if (!vma->anon_vma)
1650 /*
1651 * Not yet faulted in so we will register later in the
1652 * page fault if needed.
1653 */
1654 return 0;
1655 if (vma->vm_ops)
1656 /* khugepaged not yet working on file or special mappings */
1657 return 0;
1658 /*
1659 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1660 * true too, verify it here.
1661 */
1662 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1663 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1664 hend = vma->vm_end & HPAGE_PMD_MASK;
1665 if (hstart < hend)
1666 return khugepaged_enter(vma);
1667 return 0;
1668}
1669
1670void __khugepaged_exit(struct mm_struct *mm)
1671{
1672 struct mm_slot *mm_slot;
1673 int free = 0;
1674
1675 spin_lock(&khugepaged_mm_lock);
1676 mm_slot = get_mm_slot(mm);
1677 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1678 hlist_del(&mm_slot->hash);
1679 list_del(&mm_slot->mm_node);
1680 free = 1;
1681 }
1682 spin_unlock(&khugepaged_mm_lock);
1683
1684 if (free) {
1685 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1686 free_mm_slot(mm_slot);
1687 mmdrop(mm);
1688 } else if (mm_slot) {
1689 /*
1690 * This is required to serialize against
1691 * khugepaged_test_exit() (which is guaranteed to run
1692 * under mmap sem read mode). Stop here (after we
1693 * return all pagetables will be destroyed) until
1694 * khugepaged has finished working on the pagetables
1695 * under the mmap_sem.
1696 */
1697 down_write(&mm->mmap_sem);
1698 up_write(&mm->mmap_sem);
1699 }
1700}
1701
1702static void release_pte_page(struct page *page)
1703{
1704 /* 0 stands for page_is_file_cache(page) == false */
1705 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1706 unlock_page(page);
1707 putback_lru_page(page);
1708}
1709
1710static void release_pte_pages(pte_t *pte, pte_t *_pte)
1711{
1712 while (--_pte >= pte) {
1713 pte_t pteval = *_pte;
1714 if (!pte_none(pteval))
1715 release_pte_page(pte_page(pteval));
1716 }
1717}
1718
1719static void release_all_pte_pages(pte_t *pte)
1720{
1721 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1722}
1723
1724static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1725 unsigned long address,
1726 pte_t *pte)
1727{
1728 struct page *page;
1729 pte_t *_pte;
1730 int referenced = 0, isolated = 0, none = 0;
1731 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1732 _pte++, address += PAGE_SIZE) {
1733 pte_t pteval = *_pte;
1734 if (pte_none(pteval)) {
1735 if (++none <= khugepaged_max_ptes_none)
1736 continue;
1737 else {
1738 release_pte_pages(pte, _pte);
1739 goto out;
1740 }
1741 }
1742 if (!pte_present(pteval) || !pte_write(pteval)) {
1743 release_pte_pages(pte, _pte);
1744 goto out;
1745 }
1746 page = vm_normal_page(vma, address, pteval);
1747 if (unlikely(!page)) {
1748 release_pte_pages(pte, _pte);
1749 goto out;
1750 }
1751 VM_BUG_ON(PageCompound(page));
1752 BUG_ON(!PageAnon(page));
1753 VM_BUG_ON(!PageSwapBacked(page));
1754
1755 /* cannot use mapcount: can't collapse if there's a gup pin */
1756 if (page_count(page) != 1) {
1757 release_pte_pages(pte, _pte);
1758 goto out;
1759 }
1760 /*
1761 * We can do it before isolate_lru_page because the
1762 * page can't be freed from under us. NOTE: PG_lock
1763 * is needed to serialize against split_huge_page
1764 * when invoked from the VM.
1765 */
1766 if (!trylock_page(page)) {
1767 release_pte_pages(pte, _pte);
1768 goto out;
1769 }
1770 /*
1771 * Isolate the page to avoid collapsing an hugepage
1772 * currently in use by the VM.
1773 */
1774 if (isolate_lru_page(page)) {
1775 unlock_page(page);
1776 release_pte_pages(pte, _pte);
1777 goto out;
1778 }
1779 /* 0 stands for page_is_file_cache(page) == false */
1780 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1781 VM_BUG_ON(!PageLocked(page));
1782 VM_BUG_ON(PageLRU(page));
1783
1784 /* If there is no mapped pte young don't collapse the page */
1785 if (pte_young(pteval) || PageReferenced(page) ||
1786 mmu_notifier_test_young(vma->vm_mm, address))
1787 referenced = 1;
1788 }
1789 if (unlikely(!referenced))
1790 release_all_pte_pages(pte);
1791 else
1792 isolated = 1;
1793out:
1794 return isolated;
1795}
1796
1797static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1798 struct vm_area_struct *vma,
1799 unsigned long address,
1800 spinlock_t *ptl)
1801{
1802 pte_t *_pte;
1803 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1804 pte_t pteval = *_pte;
1805 struct page *src_page;
1806
1807 if (pte_none(pteval)) {
1808 clear_user_highpage(page, address);
1809 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1810 } else {
1811 src_page = pte_page(pteval);
1812 copy_user_highpage(page, src_page, address, vma);
1813 VM_BUG_ON(page_mapcount(src_page) != 1);
1814 VM_BUG_ON(page_count(src_page) != 2);
1815 release_pte_page(src_page);
1816 /*
1817 * ptl mostly unnecessary, but preempt has to
1818 * be disabled to update the per-cpu stats
1819 * inside page_remove_rmap().
1820 */
1821 spin_lock(ptl);
1822 /*
1823 * paravirt calls inside pte_clear here are
1824 * superfluous.
1825 */
1826 pte_clear(vma->vm_mm, address, _pte);
1827 page_remove_rmap(src_page);
1828 spin_unlock(ptl);
1829 free_page_and_swap_cache(src_page);
1830 }
1831
1832 address += PAGE_SIZE;
1833 page++;
1834 }
1835}
1836
1837static void collapse_huge_page(struct mm_struct *mm,
1838 unsigned long address,
1839 struct page **hpage,
1840 struct vm_area_struct *vma,
1841 int node)
1842{
1843 pgd_t *pgd;
1844 pud_t *pud;
1845 pmd_t *pmd, _pmd;
1846 pte_t *pte;
1847 pgtable_t pgtable;
1848 struct page *new_page;
1849 spinlock_t *ptl;
1850 int isolated;
1851 unsigned long hstart, hend;
1852
1853 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1854#ifndef CONFIG_NUMA
1855 up_read(&mm->mmap_sem);
1856 VM_BUG_ON(!*hpage);
1857 new_page = *hpage;
1858#else
1859 VM_BUG_ON(*hpage);
1860 /*
1861 * Allocate the page while the vma is still valid and under
1862 * the mmap_sem read mode so there is no memory allocation
1863 * later when we take the mmap_sem in write mode. This is more
1864 * friendly behavior (OTOH it may actually hide bugs) to
1865 * filesystems in userland with daemons allocating memory in
1866 * the userland I/O paths. Allocating memory with the
1867 * mmap_sem in read mode is good idea also to allow greater
1868 * scalability.
1869 */
1870 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1871 node, __GFP_OTHER_NODE);
1872
1873 /*
1874 * After allocating the hugepage, release the mmap_sem read lock in
1875 * preparation for taking it in write mode.
1876 */
1877 up_read(&mm->mmap_sem);
1878 if (unlikely(!new_page)) {
1879 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1880 *hpage = ERR_PTR(-ENOMEM);
1881 return;
1882 }
1883#endif
1884
1885 count_vm_event(THP_COLLAPSE_ALLOC);
1886 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1887#ifdef CONFIG_NUMA
1888 put_page(new_page);
1889#endif
1890 return;
1891 }
1892
1893 /*
1894 * Prevent all access to pagetables with the exception of
1895 * gup_fast later hanlded by the ptep_clear_flush and the VM
1896 * handled by the anon_vma lock + PG_lock.
1897 */
1898 down_write(&mm->mmap_sem);
1899 if (unlikely(khugepaged_test_exit(mm)))
1900 goto out;
1901
1902 vma = find_vma(mm, address);
1903 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1904 hend = vma->vm_end & HPAGE_PMD_MASK;
1905 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1906 goto out;
1907
1908 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1909 (vma->vm_flags & VM_NOHUGEPAGE))
1910 goto out;
1911
1912 if (!vma->anon_vma || vma->vm_ops)
1913 goto out;
1914 if (is_vma_temporary_stack(vma))
1915 goto out;
1916 /*
1917 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1918 * true too, verify it here.
1919 */
1920 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1921
1922 pgd = pgd_offset(mm, address);
1923 if (!pgd_present(*pgd))
1924 goto out;
1925
1926 pud = pud_offset(pgd, address);
1927 if (!pud_present(*pud))
1928 goto out;
1929
1930 pmd = pmd_offset(pud, address);
1931 /* pmd can't go away or become huge under us */
1932 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1933 goto out;
1934
1935 anon_vma_lock(vma->anon_vma);
1936
1937 pte = pte_offset_map(pmd, address);
1938 ptl = pte_lockptr(mm, pmd);
1939
1940 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1941 /*
1942 * After this gup_fast can't run anymore. This also removes
1943 * any huge TLB entry from the CPU so we won't allow
1944 * huge and small TLB entries for the same virtual address
1945 * to avoid the risk of CPU bugs in that area.
1946 */
1947 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1948 spin_unlock(&mm->page_table_lock);
1949
1950 spin_lock(ptl);
1951 isolated = __collapse_huge_page_isolate(vma, address, pte);
1952 spin_unlock(ptl);
1953
1954 if (unlikely(!isolated)) {
1955 pte_unmap(pte);
1956 spin_lock(&mm->page_table_lock);
1957 BUG_ON(!pmd_none(*pmd));
1958 set_pmd_at(mm, address, pmd, _pmd);
1959 spin_unlock(&mm->page_table_lock);
1960 anon_vma_unlock(vma->anon_vma);
1961 goto out;
1962 }
1963
1964 /*
1965 * All pages are isolated and locked so anon_vma rmap
1966 * can't run anymore.
1967 */
1968 anon_vma_unlock(vma->anon_vma);
1969
1970 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1971 pte_unmap(pte);
1972 __SetPageUptodate(new_page);
1973 pgtable = pmd_pgtable(_pmd);
1974 VM_BUG_ON(page_count(pgtable) != 1);
1975 VM_BUG_ON(page_mapcount(pgtable) != 0);
1976
1977 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1978 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1979 _pmd = pmd_mkhuge(_pmd);
1980
1981 /*
1982 * spin_lock() below is not the equivalent of smp_wmb(), so
1983 * this is needed to avoid the copy_huge_page writes to become
1984 * visible after the set_pmd_at() write.
1985 */
1986 smp_wmb();
1987
1988 spin_lock(&mm->page_table_lock);
1989 BUG_ON(!pmd_none(*pmd));
1990 page_add_new_anon_rmap(new_page, vma, address);
1991 set_pmd_at(mm, address, pmd, _pmd);
1992 update_mmu_cache(vma, address, _pmd);
1993 prepare_pmd_huge_pte(pgtable, mm);
1994 spin_unlock(&mm->page_table_lock);
1995
1996#ifndef CONFIG_NUMA
1997 *hpage = NULL;
1998#endif
1999 khugepaged_pages_collapsed++;
2000out_up_write:
2001 up_write(&mm->mmap_sem);
2002 return;
2003
2004out:
2005 mem_cgroup_uncharge_page(new_page);
2006#ifdef CONFIG_NUMA
2007 put_page(new_page);
2008#endif
2009 goto out_up_write;
2010}
2011
2012static int khugepaged_scan_pmd(struct mm_struct *mm,
2013 struct vm_area_struct *vma,
2014 unsigned long address,
2015 struct page **hpage)
2016{
2017 pgd_t *pgd;
2018 pud_t *pud;
2019 pmd_t *pmd;
2020 pte_t *pte, *_pte;
2021 int ret = 0, referenced = 0, none = 0;
2022 struct page *page;
2023 unsigned long _address;
2024 spinlock_t *ptl;
2025 int node = -1;
2026
2027 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2028
2029 pgd = pgd_offset(mm, address);
2030 if (!pgd_present(*pgd))
2031 goto out;
2032
2033 pud = pud_offset(pgd, address);
2034 if (!pud_present(*pud))
2035 goto out;
2036
2037 pmd = pmd_offset(pud, address);
2038 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
2039 goto out;
2040
2041 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2042 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2043 _pte++, _address += PAGE_SIZE) {
2044 pte_t pteval = *_pte;
2045 if (pte_none(pteval)) {
2046 if (++none <= khugepaged_max_ptes_none)
2047 continue;
2048 else
2049 goto out_unmap;
2050 }
2051 if (!pte_present(pteval) || !pte_write(pteval))
2052 goto out_unmap;
2053 page = vm_normal_page(vma, _address, pteval);
2054 if (unlikely(!page))
2055 goto out_unmap;
2056 /*
2057 * Chose the node of the first page. This could
2058 * be more sophisticated and look at more pages,
2059 * but isn't for now.
2060 */
2061 if (node == -1)
2062 node = page_to_nid(page);
2063 VM_BUG_ON(PageCompound(page));
2064 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2065 goto out_unmap;
2066 /* cannot use mapcount: can't collapse if there's a gup pin */
2067 if (page_count(page) != 1)
2068 goto out_unmap;
2069 if (pte_young(pteval) || PageReferenced(page) ||
2070 mmu_notifier_test_young(vma->vm_mm, address))
2071 referenced = 1;
2072 }
2073 if (referenced)
2074 ret = 1;
2075out_unmap:
2076 pte_unmap_unlock(pte, ptl);
2077 if (ret)
2078 /* collapse_huge_page will return with the mmap_sem released */
2079 collapse_huge_page(mm, address, hpage, vma, node);
2080out:
2081 return ret;
2082}
2083
2084static void collect_mm_slot(struct mm_slot *mm_slot)
2085{
2086 struct mm_struct *mm = mm_slot->mm;
2087
2088 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2089
2090 if (khugepaged_test_exit(mm)) {
2091 /* free mm_slot */
2092 hlist_del(&mm_slot->hash);
2093 list_del(&mm_slot->mm_node);
2094
2095 /*
2096 * Not strictly needed because the mm exited already.
2097 *
2098 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2099 */
2100
2101 /* khugepaged_mm_lock actually not necessary for the below */
2102 free_mm_slot(mm_slot);
2103 mmdrop(mm);
2104 }
2105}
2106
2107static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2108 struct page **hpage)
2109 __releases(&khugepaged_mm_lock)
2110 __acquires(&khugepaged_mm_lock)
2111{
2112 struct mm_slot *mm_slot;
2113 struct mm_struct *mm;
2114 struct vm_area_struct *vma;
2115 int progress = 0;
2116
2117 VM_BUG_ON(!pages);
2118 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2119
2120 if (khugepaged_scan.mm_slot)
2121 mm_slot = khugepaged_scan.mm_slot;
2122 else {
2123 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2124 struct mm_slot, mm_node);
2125 khugepaged_scan.address = 0;
2126 khugepaged_scan.mm_slot = mm_slot;
2127 }
2128 spin_unlock(&khugepaged_mm_lock);
2129
2130 mm = mm_slot->mm;
2131 down_read(&mm->mmap_sem);
2132 if (unlikely(khugepaged_test_exit(mm)))
2133 vma = NULL;
2134 else
2135 vma = find_vma(mm, khugepaged_scan.address);
2136
2137 progress++;
2138 for (; vma; vma = vma->vm_next) {
2139 unsigned long hstart, hend;
2140
2141 cond_resched();
2142 if (unlikely(khugepaged_test_exit(mm))) {
2143 progress++;
2144 break;
2145 }
2146
2147 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2148 !khugepaged_always()) ||
2149 (vma->vm_flags & VM_NOHUGEPAGE)) {
2150 skip:
2151 progress++;
2152 continue;
2153 }
2154 if (!vma->anon_vma || vma->vm_ops)
2155 goto skip;
2156 if (is_vma_temporary_stack(vma))
2157 goto skip;
2158 /*
2159 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2160 * must be true too, verify it here.
2161 */
2162 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2163 vma->vm_flags & VM_NO_THP);
2164
2165 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2166 hend = vma->vm_end & HPAGE_PMD_MASK;
2167 if (hstart >= hend)
2168 goto skip;
2169 if (khugepaged_scan.address > hend)
2170 goto skip;
2171 if (khugepaged_scan.address < hstart)
2172 khugepaged_scan.address = hstart;
2173 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2174
2175 while (khugepaged_scan.address < hend) {
2176 int ret;
2177 cond_resched();
2178 if (unlikely(khugepaged_test_exit(mm)))
2179 goto breakouterloop;
2180
2181 VM_BUG_ON(khugepaged_scan.address < hstart ||
2182 khugepaged_scan.address + HPAGE_PMD_SIZE >
2183 hend);
2184 ret = khugepaged_scan_pmd(mm, vma,
2185 khugepaged_scan.address,
2186 hpage);
2187 /* move to next address */
2188 khugepaged_scan.address += HPAGE_PMD_SIZE;
2189 progress += HPAGE_PMD_NR;
2190 if (ret)
2191 /* we released mmap_sem so break loop */
2192 goto breakouterloop_mmap_sem;
2193 if (progress >= pages)
2194 goto breakouterloop;
2195 }
2196 }
2197breakouterloop:
2198 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2199breakouterloop_mmap_sem:
2200
2201 spin_lock(&khugepaged_mm_lock);
2202 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2203 /*
2204 * Release the current mm_slot if this mm is about to die, or
2205 * if we scanned all vmas of this mm.
2206 */
2207 if (khugepaged_test_exit(mm) || !vma) {
2208 /*
2209 * Make sure that if mm_users is reaching zero while
2210 * khugepaged runs here, khugepaged_exit will find
2211 * mm_slot not pointing to the exiting mm.
2212 */
2213 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2214 khugepaged_scan.mm_slot = list_entry(
2215 mm_slot->mm_node.next,
2216 struct mm_slot, mm_node);
2217 khugepaged_scan.address = 0;
2218 } else {
2219 khugepaged_scan.mm_slot = NULL;
2220 khugepaged_full_scans++;
2221 }
2222
2223 collect_mm_slot(mm_slot);
2224 }
2225
2226 return progress;
2227}
2228
2229static int khugepaged_has_work(void)
2230{
2231 return !list_empty(&khugepaged_scan.mm_head) &&
2232 khugepaged_enabled();
2233}
2234
2235static int khugepaged_wait_event(void)
2236{
2237 return !list_empty(&khugepaged_scan.mm_head) ||
2238 !khugepaged_enabled();
2239}
2240
2241static void khugepaged_do_scan(struct page **hpage)
2242{
2243 unsigned int progress = 0, pass_through_head = 0;
2244 unsigned int pages = khugepaged_pages_to_scan;
2245
2246 barrier(); /* write khugepaged_pages_to_scan to local stack */
2247
2248 while (progress < pages) {
2249 cond_resched();
2250
2251#ifndef CONFIG_NUMA
2252 if (!*hpage) {
2253 *hpage = alloc_hugepage(khugepaged_defrag());
2254 if (unlikely(!*hpage)) {
2255 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2256 break;
2257 }
2258 count_vm_event(THP_COLLAPSE_ALLOC);
2259 }
2260#else
2261 if (IS_ERR(*hpage))
2262 break;
2263#endif
2264
2265 if (unlikely(kthread_should_stop() || freezing(current)))
2266 break;
2267
2268 spin_lock(&khugepaged_mm_lock);
2269 if (!khugepaged_scan.mm_slot)
2270 pass_through_head++;
2271 if (khugepaged_has_work() &&
2272 pass_through_head < 2)
2273 progress += khugepaged_scan_mm_slot(pages - progress,
2274 hpage);
2275 else
2276 progress = pages;
2277 spin_unlock(&khugepaged_mm_lock);
2278 }
2279}
2280
2281static void khugepaged_alloc_sleep(void)
2282{
2283 wait_event_freezable_timeout(khugepaged_wait, false,
2284 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2285}
2286
2287#ifndef CONFIG_NUMA
2288static struct page *khugepaged_alloc_hugepage(void)
2289{
2290 struct page *hpage;
2291
2292 do {
2293 hpage = alloc_hugepage(khugepaged_defrag());
2294 if (!hpage) {
2295 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2296 khugepaged_alloc_sleep();
2297 } else
2298 count_vm_event(THP_COLLAPSE_ALLOC);
2299 } while (unlikely(!hpage) &&
2300 likely(khugepaged_enabled()));
2301 return hpage;
2302}
2303#endif
2304
2305static void khugepaged_loop(void)
2306{
2307 struct page *hpage;
2308
2309#ifdef CONFIG_NUMA
2310 hpage = NULL;
2311#endif
2312 while (likely(khugepaged_enabled())) {
2313#ifndef CONFIG_NUMA
2314 hpage = khugepaged_alloc_hugepage();
2315 if (unlikely(!hpage))
2316 break;
2317#else
2318 if (IS_ERR(hpage)) {
2319 khugepaged_alloc_sleep();
2320 hpage = NULL;
2321 }
2322#endif
2323
2324 khugepaged_do_scan(&hpage);
2325#ifndef CONFIG_NUMA
2326 if (hpage)
2327 put_page(hpage);
2328#endif
2329 try_to_freeze();
2330 if (unlikely(kthread_should_stop()))
2331 break;
2332 if (khugepaged_has_work()) {
2333 if (!khugepaged_scan_sleep_millisecs)
2334 continue;
2335 wait_event_freezable_timeout(khugepaged_wait, false,
2336 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2337 } else if (khugepaged_enabled())
2338 wait_event_freezable(khugepaged_wait,
2339 khugepaged_wait_event());
2340 }
2341}
2342
2343static int khugepaged(void *none)
2344{
2345 struct mm_slot *mm_slot;
2346
2347 set_freezable();
2348 set_user_nice(current, 19);
2349
2350 /* serialize with start_khugepaged() */
2351 mutex_lock(&khugepaged_mutex);
2352
2353 for (;;) {
2354 mutex_unlock(&khugepaged_mutex);
2355 VM_BUG_ON(khugepaged_thread != current);
2356 khugepaged_loop();
2357 VM_BUG_ON(khugepaged_thread != current);
2358
2359 mutex_lock(&khugepaged_mutex);
2360 if (!khugepaged_enabled())
2361 break;
2362 if (unlikely(kthread_should_stop()))
2363 break;
2364 }
2365
2366 spin_lock(&khugepaged_mm_lock);
2367 mm_slot = khugepaged_scan.mm_slot;
2368 khugepaged_scan.mm_slot = NULL;
2369 if (mm_slot)
2370 collect_mm_slot(mm_slot);
2371 spin_unlock(&khugepaged_mm_lock);
2372
2373 khugepaged_thread = NULL;
2374 mutex_unlock(&khugepaged_mutex);
2375
2376 return 0;
2377}
2378
2379void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2380{
2381 struct page *page;
2382
2383 spin_lock(&mm->page_table_lock);
2384 if (unlikely(!pmd_trans_huge(*pmd))) {
2385 spin_unlock(&mm->page_table_lock);
2386 return;
2387 }
2388 page = pmd_page(*pmd);
2389 VM_BUG_ON(!page_count(page));
2390 get_page(page);
2391 spin_unlock(&mm->page_table_lock);
2392
2393 split_huge_page(page);
2394
2395 put_page(page);
2396 BUG_ON(pmd_trans_huge(*pmd));
2397}
2398
2399static void split_huge_page_address(struct mm_struct *mm,
2400 unsigned long address)
2401{
2402 pgd_t *pgd;
2403 pud_t *pud;
2404 pmd_t *pmd;
2405
2406 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2407
2408 pgd = pgd_offset(mm, address);
2409 if (!pgd_present(*pgd))
2410 return;
2411
2412 pud = pud_offset(pgd, address);
2413 if (!pud_present(*pud))
2414 return;
2415
2416 pmd = pmd_offset(pud, address);
2417 if (!pmd_present(*pmd))
2418 return;
2419 /*
2420 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2421 * materialize from under us.
2422 */
2423 split_huge_page_pmd(mm, pmd);
2424}
2425
2426void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2427 unsigned long start,
2428 unsigned long end,
2429 long adjust_next)
2430{
2431 /*
2432 * If the new start address isn't hpage aligned and it could
2433 * previously contain an hugepage: check if we need to split
2434 * an huge pmd.
2435 */
2436 if (start & ~HPAGE_PMD_MASK &&
2437 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2438 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2439 split_huge_page_address(vma->vm_mm, start);
2440
2441 /*
2442 * If the new end address isn't hpage aligned and it could
2443 * previously contain an hugepage: check if we need to split
2444 * an huge pmd.
2445 */
2446 if (end & ~HPAGE_PMD_MASK &&
2447 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2448 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2449 split_huge_page_address(vma->vm_mm, end);
2450
2451 /*
2452 * If we're also updating the vma->vm_next->vm_start, if the new
2453 * vm_next->vm_start isn't page aligned and it could previously
2454 * contain an hugepage: check if we need to split an huge pmd.
2455 */
2456 if (adjust_next > 0) {
2457 struct vm_area_struct *next = vma->vm_next;
2458 unsigned long nstart = next->vm_start;
2459 nstart += adjust_next << PAGE_SHIFT;
2460 if (nstart & ~HPAGE_PMD_MASK &&
2461 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2462 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2463 split_huge_page_address(next->vm_mm, nstart);
2464 }
2465}