mm: Account for a THP NUMA hinting update as one PTE update
[linux-3.10.git] / mm / huge_memory.c
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/shrinker.h>
16 #include <linux/mm_inline.h>
17 #include <linux/kthread.h>
18 #include <linux/khugepaged.h>
19 #include <linux/freezer.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/migrate.h>
23 #include <linux/hashtable.h>
24
25 #include <asm/tlb.h>
26 #include <asm/pgalloc.h>
27 #include "internal.h"
28
29 /*
30  * By default transparent hugepage support is enabled for all mappings
31  * and khugepaged scans all mappings. Defrag is only invoked by
32  * khugepaged hugepage allocations and by page faults inside
33  * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
34  * allocations.
35  */
36 unsigned long transparent_hugepage_flags __read_mostly =
37 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
38         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
39 #endif
40 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
41         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
42 #endif
43         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
44         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
45         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
46
47 /* default scan 8*512 pte (or vmas) every 30 second */
48 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
49 static unsigned int khugepaged_pages_collapsed;
50 static unsigned int khugepaged_full_scans;
51 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
52 /* during fragmentation poll the hugepage allocator once every minute */
53 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
54 static struct task_struct *khugepaged_thread __read_mostly;
55 static DEFINE_MUTEX(khugepaged_mutex);
56 static DEFINE_SPINLOCK(khugepaged_mm_lock);
57 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
58 /*
59  * default collapse hugepages if there is at least one pte mapped like
60  * it would have happened if the vma was large enough during page
61  * fault.
62  */
63 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
64
65 static int khugepaged(void *none);
66 static int khugepaged_slab_init(void);
67
68 #define MM_SLOTS_HASH_BITS 10
69 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
70
71 static struct kmem_cache *mm_slot_cache __read_mostly;
72
73 /**
74  * struct mm_slot - hash lookup from mm to mm_slot
75  * @hash: hash collision list
76  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
77  * @mm: the mm that this information is valid for
78  */
79 struct mm_slot {
80         struct hlist_node hash;
81         struct list_head mm_node;
82         struct mm_struct *mm;
83 };
84
85 /**
86  * struct khugepaged_scan - cursor for scanning
87  * @mm_head: the head of the mm list to scan
88  * @mm_slot: the current mm_slot we are scanning
89  * @address: the next address inside that to be scanned
90  *
91  * There is only the one khugepaged_scan instance of this cursor structure.
92  */
93 struct khugepaged_scan {
94         struct list_head mm_head;
95         struct mm_slot *mm_slot;
96         unsigned long address;
97 };
98 static struct khugepaged_scan khugepaged_scan = {
99         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
100 };
101
102
103 static int set_recommended_min_free_kbytes(void)
104 {
105         struct zone *zone;
106         int nr_zones = 0;
107         unsigned long recommended_min;
108
109         if (!khugepaged_enabled())
110                 return 0;
111
112         for_each_populated_zone(zone)
113                 nr_zones++;
114
115         /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
116         recommended_min = pageblock_nr_pages * nr_zones * 2;
117
118         /*
119          * Make sure that on average at least two pageblocks are almost free
120          * of another type, one for a migratetype to fall back to and a
121          * second to avoid subsequent fallbacks of other types There are 3
122          * MIGRATE_TYPES we care about.
123          */
124         recommended_min += pageblock_nr_pages * nr_zones *
125                            MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
126
127         /* don't ever allow to reserve more than 5% of the lowmem */
128         recommended_min = min(recommended_min,
129                               (unsigned long) nr_free_buffer_pages() / 20);
130         recommended_min <<= (PAGE_SHIFT-10);
131
132         if (recommended_min > min_free_kbytes)
133                 min_free_kbytes = recommended_min;
134         setup_per_zone_wmarks();
135         return 0;
136 }
137 late_initcall(set_recommended_min_free_kbytes);
138
139 static int start_khugepaged(void)
140 {
141         int err = 0;
142         if (khugepaged_enabled()) {
143                 if (!khugepaged_thread)
144                         khugepaged_thread = kthread_run(khugepaged, NULL,
145                                                         "khugepaged");
146                 if (unlikely(IS_ERR(khugepaged_thread))) {
147                         printk(KERN_ERR
148                                "khugepaged: kthread_run(khugepaged) failed\n");
149                         err = PTR_ERR(khugepaged_thread);
150                         khugepaged_thread = NULL;
151                 }
152
153                 if (!list_empty(&khugepaged_scan.mm_head))
154                         wake_up_interruptible(&khugepaged_wait);
155
156                 set_recommended_min_free_kbytes();
157         } else if (khugepaged_thread) {
158                 kthread_stop(khugepaged_thread);
159                 khugepaged_thread = NULL;
160         }
161
162         return err;
163 }
164
165 static atomic_t huge_zero_refcount;
166 static struct page *huge_zero_page __read_mostly;
167
168 static inline bool is_huge_zero_page(struct page *page)
169 {
170         return ACCESS_ONCE(huge_zero_page) == page;
171 }
172
173 static inline bool is_huge_zero_pmd(pmd_t pmd)
174 {
175         return is_huge_zero_page(pmd_page(pmd));
176 }
177
178 static struct page *get_huge_zero_page(void)
179 {
180         struct page *zero_page;
181 retry:
182         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
183                 return ACCESS_ONCE(huge_zero_page);
184
185         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
186                         HPAGE_PMD_ORDER);
187         if (!zero_page) {
188                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
189                 return NULL;
190         }
191         count_vm_event(THP_ZERO_PAGE_ALLOC);
192         preempt_disable();
193         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
194                 preempt_enable();
195                 __free_page(zero_page);
196                 goto retry;
197         }
198
199         /* We take additional reference here. It will be put back by shrinker */
200         atomic_set(&huge_zero_refcount, 2);
201         preempt_enable();
202         return ACCESS_ONCE(huge_zero_page);
203 }
204
205 static void put_huge_zero_page(void)
206 {
207         /*
208          * Counter should never go to zero here. Only shrinker can put
209          * last reference.
210          */
211         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
212 }
213
214 static int shrink_huge_zero_page(struct shrinker *shrink,
215                 struct shrink_control *sc)
216 {
217         if (!sc->nr_to_scan)
218                 /* we can free zero page only if last reference remains */
219                 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
220
221         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
222                 struct page *zero_page = xchg(&huge_zero_page, NULL);
223                 BUG_ON(zero_page == NULL);
224                 __free_page(zero_page);
225         }
226
227         return 0;
228 }
229
230 static struct shrinker huge_zero_page_shrinker = {
231         .shrink = shrink_huge_zero_page,
232         .seeks = DEFAULT_SEEKS,
233 };
234
235 #ifdef CONFIG_SYSFS
236
237 static ssize_t double_flag_show(struct kobject *kobj,
238                                 struct kobj_attribute *attr, char *buf,
239                                 enum transparent_hugepage_flag enabled,
240                                 enum transparent_hugepage_flag req_madv)
241 {
242         if (test_bit(enabled, &transparent_hugepage_flags)) {
243                 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
244                 return sprintf(buf, "[always] madvise never\n");
245         } else if (test_bit(req_madv, &transparent_hugepage_flags))
246                 return sprintf(buf, "always [madvise] never\n");
247         else
248                 return sprintf(buf, "always madvise [never]\n");
249 }
250 static ssize_t double_flag_store(struct kobject *kobj,
251                                  struct kobj_attribute *attr,
252                                  const char *buf, size_t count,
253                                  enum transparent_hugepage_flag enabled,
254                                  enum transparent_hugepage_flag req_madv)
255 {
256         if (!memcmp("always", buf,
257                     min(sizeof("always")-1, count))) {
258                 set_bit(enabled, &transparent_hugepage_flags);
259                 clear_bit(req_madv, &transparent_hugepage_flags);
260         } else if (!memcmp("madvise", buf,
261                            min(sizeof("madvise")-1, count))) {
262                 clear_bit(enabled, &transparent_hugepage_flags);
263                 set_bit(req_madv, &transparent_hugepage_flags);
264         } else if (!memcmp("never", buf,
265                            min(sizeof("never")-1, count))) {
266                 clear_bit(enabled, &transparent_hugepage_flags);
267                 clear_bit(req_madv, &transparent_hugepage_flags);
268         } else
269                 return -EINVAL;
270
271         return count;
272 }
273
274 static ssize_t enabled_show(struct kobject *kobj,
275                             struct kobj_attribute *attr, char *buf)
276 {
277         return double_flag_show(kobj, attr, buf,
278                                 TRANSPARENT_HUGEPAGE_FLAG,
279                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
280 }
281 static ssize_t enabled_store(struct kobject *kobj,
282                              struct kobj_attribute *attr,
283                              const char *buf, size_t count)
284 {
285         ssize_t ret;
286
287         ret = double_flag_store(kobj, attr, buf, count,
288                                 TRANSPARENT_HUGEPAGE_FLAG,
289                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
290
291         if (ret > 0) {
292                 int err;
293
294                 mutex_lock(&khugepaged_mutex);
295                 err = start_khugepaged();
296                 mutex_unlock(&khugepaged_mutex);
297
298                 if (err)
299                         ret = err;
300         }
301
302         return ret;
303 }
304 static struct kobj_attribute enabled_attr =
305         __ATTR(enabled, 0644, enabled_show, enabled_store);
306
307 static ssize_t single_flag_show(struct kobject *kobj,
308                                 struct kobj_attribute *attr, char *buf,
309                                 enum transparent_hugepage_flag flag)
310 {
311         return sprintf(buf, "%d\n",
312                        !!test_bit(flag, &transparent_hugepage_flags));
313 }
314
315 static ssize_t single_flag_store(struct kobject *kobj,
316                                  struct kobj_attribute *attr,
317                                  const char *buf, size_t count,
318                                  enum transparent_hugepage_flag flag)
319 {
320         unsigned long value;
321         int ret;
322
323         ret = kstrtoul(buf, 10, &value);
324         if (ret < 0)
325                 return ret;
326         if (value > 1)
327                 return -EINVAL;
328
329         if (value)
330                 set_bit(flag, &transparent_hugepage_flags);
331         else
332                 clear_bit(flag, &transparent_hugepage_flags);
333
334         return count;
335 }
336
337 /*
338  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
339  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
340  * memory just to allocate one more hugepage.
341  */
342 static ssize_t defrag_show(struct kobject *kobj,
343                            struct kobj_attribute *attr, char *buf)
344 {
345         return double_flag_show(kobj, attr, buf,
346                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
347                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
348 }
349 static ssize_t defrag_store(struct kobject *kobj,
350                             struct kobj_attribute *attr,
351                             const char *buf, size_t count)
352 {
353         return double_flag_store(kobj, attr, buf, count,
354                                  TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
355                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
356 }
357 static struct kobj_attribute defrag_attr =
358         __ATTR(defrag, 0644, defrag_show, defrag_store);
359
360 static ssize_t use_zero_page_show(struct kobject *kobj,
361                 struct kobj_attribute *attr, char *buf)
362 {
363         return single_flag_show(kobj, attr, buf,
364                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
365 }
366 static ssize_t use_zero_page_store(struct kobject *kobj,
367                 struct kobj_attribute *attr, const char *buf, size_t count)
368 {
369         return single_flag_store(kobj, attr, buf, count,
370                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
371 }
372 static struct kobj_attribute use_zero_page_attr =
373         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
374 #ifdef CONFIG_DEBUG_VM
375 static ssize_t debug_cow_show(struct kobject *kobj,
376                                 struct kobj_attribute *attr, char *buf)
377 {
378         return single_flag_show(kobj, attr, buf,
379                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
380 }
381 static ssize_t debug_cow_store(struct kobject *kobj,
382                                struct kobj_attribute *attr,
383                                const char *buf, size_t count)
384 {
385         return single_flag_store(kobj, attr, buf, count,
386                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
387 }
388 static struct kobj_attribute debug_cow_attr =
389         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
390 #endif /* CONFIG_DEBUG_VM */
391
392 static struct attribute *hugepage_attr[] = {
393         &enabled_attr.attr,
394         &defrag_attr.attr,
395         &use_zero_page_attr.attr,
396 #ifdef CONFIG_DEBUG_VM
397         &debug_cow_attr.attr,
398 #endif
399         NULL,
400 };
401
402 static struct attribute_group hugepage_attr_group = {
403         .attrs = hugepage_attr,
404 };
405
406 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
407                                          struct kobj_attribute *attr,
408                                          char *buf)
409 {
410         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
411 }
412
413 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
414                                           struct kobj_attribute *attr,
415                                           const char *buf, size_t count)
416 {
417         unsigned long msecs;
418         int err;
419
420         err = strict_strtoul(buf, 10, &msecs);
421         if (err || msecs > UINT_MAX)
422                 return -EINVAL;
423
424         khugepaged_scan_sleep_millisecs = msecs;
425         wake_up_interruptible(&khugepaged_wait);
426
427         return count;
428 }
429 static struct kobj_attribute scan_sleep_millisecs_attr =
430         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
431                scan_sleep_millisecs_store);
432
433 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
434                                           struct kobj_attribute *attr,
435                                           char *buf)
436 {
437         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
438 }
439
440 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
441                                            struct kobj_attribute *attr,
442                                            const char *buf, size_t count)
443 {
444         unsigned long msecs;
445         int err;
446
447         err = strict_strtoul(buf, 10, &msecs);
448         if (err || msecs > UINT_MAX)
449                 return -EINVAL;
450
451         khugepaged_alloc_sleep_millisecs = msecs;
452         wake_up_interruptible(&khugepaged_wait);
453
454         return count;
455 }
456 static struct kobj_attribute alloc_sleep_millisecs_attr =
457         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
458                alloc_sleep_millisecs_store);
459
460 static ssize_t pages_to_scan_show(struct kobject *kobj,
461                                   struct kobj_attribute *attr,
462                                   char *buf)
463 {
464         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
465 }
466 static ssize_t pages_to_scan_store(struct kobject *kobj,
467                                    struct kobj_attribute *attr,
468                                    const char *buf, size_t count)
469 {
470         int err;
471         unsigned long pages;
472
473         err = strict_strtoul(buf, 10, &pages);
474         if (err || !pages || pages > UINT_MAX)
475                 return -EINVAL;
476
477         khugepaged_pages_to_scan = pages;
478
479         return count;
480 }
481 static struct kobj_attribute pages_to_scan_attr =
482         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
483                pages_to_scan_store);
484
485 static ssize_t pages_collapsed_show(struct kobject *kobj,
486                                     struct kobj_attribute *attr,
487                                     char *buf)
488 {
489         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
490 }
491 static struct kobj_attribute pages_collapsed_attr =
492         __ATTR_RO(pages_collapsed);
493
494 static ssize_t full_scans_show(struct kobject *kobj,
495                                struct kobj_attribute *attr,
496                                char *buf)
497 {
498         return sprintf(buf, "%u\n", khugepaged_full_scans);
499 }
500 static struct kobj_attribute full_scans_attr =
501         __ATTR_RO(full_scans);
502
503 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
504                                       struct kobj_attribute *attr, char *buf)
505 {
506         return single_flag_show(kobj, attr, buf,
507                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
508 }
509 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
510                                        struct kobj_attribute *attr,
511                                        const char *buf, size_t count)
512 {
513         return single_flag_store(kobj, attr, buf, count,
514                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
515 }
516 static struct kobj_attribute khugepaged_defrag_attr =
517         __ATTR(defrag, 0644, khugepaged_defrag_show,
518                khugepaged_defrag_store);
519
520 /*
521  * max_ptes_none controls if khugepaged should collapse hugepages over
522  * any unmapped ptes in turn potentially increasing the memory
523  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
524  * reduce the available free memory in the system as it
525  * runs. Increasing max_ptes_none will instead potentially reduce the
526  * free memory in the system during the khugepaged scan.
527  */
528 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
529                                              struct kobj_attribute *attr,
530                                              char *buf)
531 {
532         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
533 }
534 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
535                                               struct kobj_attribute *attr,
536                                               const char *buf, size_t count)
537 {
538         int err;
539         unsigned long max_ptes_none;
540
541         err = strict_strtoul(buf, 10, &max_ptes_none);
542         if (err || max_ptes_none > HPAGE_PMD_NR-1)
543                 return -EINVAL;
544
545         khugepaged_max_ptes_none = max_ptes_none;
546
547         return count;
548 }
549 static struct kobj_attribute khugepaged_max_ptes_none_attr =
550         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
551                khugepaged_max_ptes_none_store);
552
553 static struct attribute *khugepaged_attr[] = {
554         &khugepaged_defrag_attr.attr,
555         &khugepaged_max_ptes_none_attr.attr,
556         &pages_to_scan_attr.attr,
557         &pages_collapsed_attr.attr,
558         &full_scans_attr.attr,
559         &scan_sleep_millisecs_attr.attr,
560         &alloc_sleep_millisecs_attr.attr,
561         NULL,
562 };
563
564 static struct attribute_group khugepaged_attr_group = {
565         .attrs = khugepaged_attr,
566         .name = "khugepaged",
567 };
568
569 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
570 {
571         int err;
572
573         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
574         if (unlikely(!*hugepage_kobj)) {
575                 printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n");
576                 return -ENOMEM;
577         }
578
579         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
580         if (err) {
581                 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
582                 goto delete_obj;
583         }
584
585         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
586         if (err) {
587                 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
588                 goto remove_hp_group;
589         }
590
591         return 0;
592
593 remove_hp_group:
594         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
595 delete_obj:
596         kobject_put(*hugepage_kobj);
597         return err;
598 }
599
600 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
601 {
602         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
603         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
604         kobject_put(hugepage_kobj);
605 }
606 #else
607 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
608 {
609         return 0;
610 }
611
612 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
613 {
614 }
615 #endif /* CONFIG_SYSFS */
616
617 static int __init hugepage_init(void)
618 {
619         int err;
620         struct kobject *hugepage_kobj;
621
622         if (!has_transparent_hugepage()) {
623                 transparent_hugepage_flags = 0;
624                 return -EINVAL;
625         }
626
627         err = hugepage_init_sysfs(&hugepage_kobj);
628         if (err)
629                 return err;
630
631         err = khugepaged_slab_init();
632         if (err)
633                 goto out;
634
635         register_shrinker(&huge_zero_page_shrinker);
636
637         /*
638          * By default disable transparent hugepages on smaller systems,
639          * where the extra memory used could hurt more than TLB overhead
640          * is likely to save.  The admin can still enable it through /sys.
641          */
642         if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
643                 transparent_hugepage_flags = 0;
644
645         start_khugepaged();
646
647         return 0;
648 out:
649         hugepage_exit_sysfs(hugepage_kobj);
650         return err;
651 }
652 module_init(hugepage_init)
653
654 static int __init setup_transparent_hugepage(char *str)
655 {
656         int ret = 0;
657         if (!str)
658                 goto out;
659         if (!strcmp(str, "always")) {
660                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
661                         &transparent_hugepage_flags);
662                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
663                           &transparent_hugepage_flags);
664                 ret = 1;
665         } else if (!strcmp(str, "madvise")) {
666                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
667                           &transparent_hugepage_flags);
668                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
669                         &transparent_hugepage_flags);
670                 ret = 1;
671         } else if (!strcmp(str, "never")) {
672                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
673                           &transparent_hugepage_flags);
674                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
675                           &transparent_hugepage_flags);
676                 ret = 1;
677         }
678 out:
679         if (!ret)
680                 printk(KERN_WARNING
681                        "transparent_hugepage= cannot parse, ignored\n");
682         return ret;
683 }
684 __setup("transparent_hugepage=", setup_transparent_hugepage);
685
686 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
687 {
688         if (likely(vma->vm_flags & VM_WRITE))
689                 pmd = pmd_mkwrite(pmd);
690         return pmd;
691 }
692
693 static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma)
694 {
695         pmd_t entry;
696         entry = mk_pmd(page, vma->vm_page_prot);
697         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
698         entry = pmd_mkhuge(entry);
699         return entry;
700 }
701
702 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
703                                         struct vm_area_struct *vma,
704                                         unsigned long haddr, pmd_t *pmd,
705                                         struct page *page)
706 {
707         pgtable_t pgtable;
708
709         VM_BUG_ON(!PageCompound(page));
710         pgtable = pte_alloc_one(mm, haddr);
711         if (unlikely(!pgtable))
712                 return VM_FAULT_OOM;
713
714         clear_huge_page(page, haddr, HPAGE_PMD_NR);
715         /*
716          * The memory barrier inside __SetPageUptodate makes sure that
717          * clear_huge_page writes become visible before the set_pmd_at()
718          * write.
719          */
720         __SetPageUptodate(page);
721
722         spin_lock(&mm->page_table_lock);
723         if (unlikely(!pmd_none(*pmd))) {
724                 spin_unlock(&mm->page_table_lock);
725                 mem_cgroup_uncharge_page(page);
726                 put_page(page);
727                 pte_free(mm, pgtable);
728         } else {
729                 pmd_t entry;
730                 entry = mk_huge_pmd(page, vma);
731                 page_add_new_anon_rmap(page, vma, haddr);
732                 set_pmd_at(mm, haddr, pmd, entry);
733                 pgtable_trans_huge_deposit(mm, pgtable);
734                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
735                 mm->nr_ptes++;
736                 spin_unlock(&mm->page_table_lock);
737         }
738
739         return 0;
740 }
741
742 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
743 {
744         return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
745 }
746
747 static inline struct page *alloc_hugepage_vma(int defrag,
748                                               struct vm_area_struct *vma,
749                                               unsigned long haddr, int nd,
750                                               gfp_t extra_gfp)
751 {
752         return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
753                                HPAGE_PMD_ORDER, vma, haddr, nd);
754 }
755
756 #ifndef CONFIG_NUMA
757 static inline struct page *alloc_hugepage(int defrag)
758 {
759         return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
760                            HPAGE_PMD_ORDER);
761 }
762 #endif
763
764 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
765                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
766                 struct page *zero_page)
767 {
768         pmd_t entry;
769         if (!pmd_none(*pmd))
770                 return false;
771         entry = mk_pmd(zero_page, vma->vm_page_prot);
772         entry = pmd_wrprotect(entry);
773         entry = pmd_mkhuge(entry);
774         set_pmd_at(mm, haddr, pmd, entry);
775         pgtable_trans_huge_deposit(mm, pgtable);
776         mm->nr_ptes++;
777         return true;
778 }
779
780 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
781                                unsigned long address, pmd_t *pmd,
782                                unsigned int flags)
783 {
784         struct page *page;
785         unsigned long haddr = address & HPAGE_PMD_MASK;
786         pte_t *pte;
787
788         if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
789                 if (unlikely(anon_vma_prepare(vma)))
790                         return VM_FAULT_OOM;
791                 if (unlikely(khugepaged_enter(vma)))
792                         return VM_FAULT_OOM;
793                 if (!(flags & FAULT_FLAG_WRITE) &&
794                                 transparent_hugepage_use_zero_page()) {
795                         pgtable_t pgtable;
796                         struct page *zero_page;
797                         bool set;
798                         pgtable = pte_alloc_one(mm, haddr);
799                         if (unlikely(!pgtable))
800                                 return VM_FAULT_OOM;
801                         zero_page = get_huge_zero_page();
802                         if (unlikely(!zero_page)) {
803                                 pte_free(mm, pgtable);
804                                 count_vm_event(THP_FAULT_FALLBACK);
805                                 goto out;
806                         }
807                         spin_lock(&mm->page_table_lock);
808                         set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
809                                         zero_page);
810                         spin_unlock(&mm->page_table_lock);
811                         if (!set) {
812                                 pte_free(mm, pgtable);
813                                 put_huge_zero_page();
814                         }
815                         return 0;
816                 }
817                 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
818                                           vma, haddr, numa_node_id(), 0);
819                 if (unlikely(!page)) {
820                         count_vm_event(THP_FAULT_FALLBACK);
821                         goto out;
822                 }
823                 count_vm_event(THP_FAULT_ALLOC);
824                 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
825                         put_page(page);
826                         goto out;
827                 }
828                 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
829                                                           page))) {
830                         mem_cgroup_uncharge_page(page);
831                         put_page(page);
832                         goto out;
833                 }
834
835                 return 0;
836         }
837 out:
838         /*
839          * Use __pte_alloc instead of pte_alloc_map, because we can't
840          * run pte_offset_map on the pmd, if an huge pmd could
841          * materialize from under us from a different thread.
842          */
843         if (unlikely(pmd_none(*pmd)) &&
844             unlikely(__pte_alloc(mm, vma, pmd, address)))
845                 return VM_FAULT_OOM;
846         /* if an huge pmd materialized from under us just retry later */
847         if (unlikely(pmd_trans_huge(*pmd)))
848                 return 0;
849         /*
850          * A regular pmd is established and it can't morph into a huge pmd
851          * from under us anymore at this point because we hold the mmap_sem
852          * read mode and khugepaged takes it in write mode. So now it's
853          * safe to run pte_offset_map().
854          */
855         pte = pte_offset_map(pmd, address);
856         return handle_pte_fault(mm, vma, address, pte, pmd, flags);
857 }
858
859 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
860                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
861                   struct vm_area_struct *vma)
862 {
863         struct page *src_page;
864         pmd_t pmd;
865         pgtable_t pgtable;
866         int ret;
867
868         ret = -ENOMEM;
869         pgtable = pte_alloc_one(dst_mm, addr);
870         if (unlikely(!pgtable))
871                 goto out;
872
873         spin_lock(&dst_mm->page_table_lock);
874         spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
875
876         ret = -EAGAIN;
877         pmd = *src_pmd;
878         if (unlikely(!pmd_trans_huge(pmd))) {
879                 pte_free(dst_mm, pgtable);
880                 goto out_unlock;
881         }
882         /*
883          * mm->page_table_lock is enough to be sure that huge zero pmd is not
884          * under splitting since we don't split the page itself, only pmd to
885          * a page table.
886          */
887         if (is_huge_zero_pmd(pmd)) {
888                 struct page *zero_page;
889                 bool set;
890                 /*
891                  * get_huge_zero_page() will never allocate a new page here,
892                  * since we already have a zero page to copy. It just takes a
893                  * reference.
894                  */
895                 zero_page = get_huge_zero_page();
896                 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
897                                 zero_page);
898                 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
899                 ret = 0;
900                 goto out_unlock;
901         }
902         if (unlikely(pmd_trans_splitting(pmd))) {
903                 /* split huge page running from under us */
904                 spin_unlock(&src_mm->page_table_lock);
905                 spin_unlock(&dst_mm->page_table_lock);
906                 pte_free(dst_mm, pgtable);
907
908                 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
909                 goto out;
910         }
911         src_page = pmd_page(pmd);
912         VM_BUG_ON(!PageHead(src_page));
913         get_page(src_page);
914         page_dup_rmap(src_page);
915         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
916
917         pmdp_set_wrprotect(src_mm, addr, src_pmd);
918         pmd = pmd_mkold(pmd_wrprotect(pmd));
919         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
920         pgtable_trans_huge_deposit(dst_mm, pgtable);
921         dst_mm->nr_ptes++;
922
923         ret = 0;
924 out_unlock:
925         spin_unlock(&src_mm->page_table_lock);
926         spin_unlock(&dst_mm->page_table_lock);
927 out:
928         return ret;
929 }
930
931 void huge_pmd_set_accessed(struct mm_struct *mm,
932                            struct vm_area_struct *vma,
933                            unsigned long address,
934                            pmd_t *pmd, pmd_t orig_pmd,
935                            int dirty)
936 {
937         pmd_t entry;
938         unsigned long haddr;
939
940         spin_lock(&mm->page_table_lock);
941         if (unlikely(!pmd_same(*pmd, orig_pmd)))
942                 goto unlock;
943
944         entry = pmd_mkyoung(orig_pmd);
945         haddr = address & HPAGE_PMD_MASK;
946         if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
947                 update_mmu_cache_pmd(vma, address, pmd);
948
949 unlock:
950         spin_unlock(&mm->page_table_lock);
951 }
952
953 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
954                 struct vm_area_struct *vma, unsigned long address,
955                 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
956 {
957         pgtable_t pgtable;
958         pmd_t _pmd;
959         struct page *page;
960         int i, ret = 0;
961         unsigned long mmun_start;       /* For mmu_notifiers */
962         unsigned long mmun_end;         /* For mmu_notifiers */
963
964         page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
965         if (!page) {
966                 ret |= VM_FAULT_OOM;
967                 goto out;
968         }
969
970         if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
971                 put_page(page);
972                 ret |= VM_FAULT_OOM;
973                 goto out;
974         }
975
976         clear_user_highpage(page, address);
977         __SetPageUptodate(page);
978
979         mmun_start = haddr;
980         mmun_end   = haddr + HPAGE_PMD_SIZE;
981         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
982
983         spin_lock(&mm->page_table_lock);
984         if (unlikely(!pmd_same(*pmd, orig_pmd)))
985                 goto out_free_page;
986
987         pmdp_clear_flush(vma, haddr, pmd);
988         /* leave pmd empty until pte is filled */
989
990         pgtable = pgtable_trans_huge_withdraw(mm);
991         pmd_populate(mm, &_pmd, pgtable);
992
993         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
994                 pte_t *pte, entry;
995                 if (haddr == (address & PAGE_MASK)) {
996                         entry = mk_pte(page, vma->vm_page_prot);
997                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
998                         page_add_new_anon_rmap(page, vma, haddr);
999                 } else {
1000                         entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1001                         entry = pte_mkspecial(entry);
1002                 }
1003                 pte = pte_offset_map(&_pmd, haddr);
1004                 VM_BUG_ON(!pte_none(*pte));
1005                 set_pte_at(mm, haddr, pte, entry);
1006                 pte_unmap(pte);
1007         }
1008         smp_wmb(); /* make pte visible before pmd */
1009         pmd_populate(mm, pmd, pgtable);
1010         spin_unlock(&mm->page_table_lock);
1011         put_huge_zero_page();
1012         inc_mm_counter(mm, MM_ANONPAGES);
1013
1014         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1015
1016         ret |= VM_FAULT_WRITE;
1017 out:
1018         return ret;
1019 out_free_page:
1020         spin_unlock(&mm->page_table_lock);
1021         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1022         mem_cgroup_uncharge_page(page);
1023         put_page(page);
1024         goto out;
1025 }
1026
1027 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1028                                         struct vm_area_struct *vma,
1029                                         unsigned long address,
1030                                         pmd_t *pmd, pmd_t orig_pmd,
1031                                         struct page *page,
1032                                         unsigned long haddr)
1033 {
1034         pgtable_t pgtable;
1035         pmd_t _pmd;
1036         int ret = 0, i;
1037         struct page **pages;
1038         unsigned long mmun_start;       /* For mmu_notifiers */
1039         unsigned long mmun_end;         /* For mmu_notifiers */
1040
1041         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1042                         GFP_KERNEL);
1043         if (unlikely(!pages)) {
1044                 ret |= VM_FAULT_OOM;
1045                 goto out;
1046         }
1047
1048         for (i = 0; i < HPAGE_PMD_NR; i++) {
1049                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1050                                                __GFP_OTHER_NODE,
1051                                                vma, address, page_to_nid(page));
1052                 if (unlikely(!pages[i] ||
1053                              mem_cgroup_newpage_charge(pages[i], mm,
1054                                                        GFP_KERNEL))) {
1055                         if (pages[i])
1056                                 put_page(pages[i]);
1057                         mem_cgroup_uncharge_start();
1058                         while (--i >= 0) {
1059                                 mem_cgroup_uncharge_page(pages[i]);
1060                                 put_page(pages[i]);
1061                         }
1062                         mem_cgroup_uncharge_end();
1063                         kfree(pages);
1064                         ret |= VM_FAULT_OOM;
1065                         goto out;
1066                 }
1067         }
1068
1069         for (i = 0; i < HPAGE_PMD_NR; i++) {
1070                 copy_user_highpage(pages[i], page + i,
1071                                    haddr + PAGE_SIZE * i, vma);
1072                 __SetPageUptodate(pages[i]);
1073                 cond_resched();
1074         }
1075
1076         mmun_start = haddr;
1077         mmun_end   = haddr + HPAGE_PMD_SIZE;
1078         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1079
1080         spin_lock(&mm->page_table_lock);
1081         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1082                 goto out_free_pages;
1083         VM_BUG_ON(!PageHead(page));
1084
1085         pmdp_clear_flush(vma, haddr, pmd);
1086         /* leave pmd empty until pte is filled */
1087
1088         pgtable = pgtable_trans_huge_withdraw(mm);
1089         pmd_populate(mm, &_pmd, pgtable);
1090
1091         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1092                 pte_t *pte, entry;
1093                 entry = mk_pte(pages[i], vma->vm_page_prot);
1094                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1095                 page_add_new_anon_rmap(pages[i], vma, haddr);
1096                 pte = pte_offset_map(&_pmd, haddr);
1097                 VM_BUG_ON(!pte_none(*pte));
1098                 set_pte_at(mm, haddr, pte, entry);
1099                 pte_unmap(pte);
1100         }
1101         kfree(pages);
1102
1103         smp_wmb(); /* make pte visible before pmd */
1104         pmd_populate(mm, pmd, pgtable);
1105         page_remove_rmap(page);
1106         spin_unlock(&mm->page_table_lock);
1107
1108         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1109
1110         ret |= VM_FAULT_WRITE;
1111         put_page(page);
1112
1113 out:
1114         return ret;
1115
1116 out_free_pages:
1117         spin_unlock(&mm->page_table_lock);
1118         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1119         mem_cgroup_uncharge_start();
1120         for (i = 0; i < HPAGE_PMD_NR; i++) {
1121                 mem_cgroup_uncharge_page(pages[i]);
1122                 put_page(pages[i]);
1123         }
1124         mem_cgroup_uncharge_end();
1125         kfree(pages);
1126         goto out;
1127 }
1128
1129 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1130                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1131 {
1132         int ret = 0;
1133         struct page *page = NULL, *new_page;
1134         unsigned long haddr;
1135         unsigned long mmun_start;       /* For mmu_notifiers */
1136         unsigned long mmun_end;         /* For mmu_notifiers */
1137
1138         VM_BUG_ON(!vma->anon_vma);
1139         haddr = address & HPAGE_PMD_MASK;
1140         if (is_huge_zero_pmd(orig_pmd))
1141                 goto alloc;
1142         spin_lock(&mm->page_table_lock);
1143         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1144                 goto out_unlock;
1145
1146         page = pmd_page(orig_pmd);
1147         VM_BUG_ON(!PageCompound(page) || !PageHead(page));
1148         if (page_mapcount(page) == 1) {
1149                 pmd_t entry;
1150                 entry = pmd_mkyoung(orig_pmd);
1151                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1152                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1153                         update_mmu_cache_pmd(vma, address, pmd);
1154                 ret |= VM_FAULT_WRITE;
1155                 goto out_unlock;
1156         }
1157         get_page(page);
1158         spin_unlock(&mm->page_table_lock);
1159 alloc:
1160         if (transparent_hugepage_enabled(vma) &&
1161             !transparent_hugepage_debug_cow())
1162                 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1163                                               vma, haddr, numa_node_id(), 0);
1164         else
1165                 new_page = NULL;
1166
1167         if (unlikely(!new_page)) {
1168                 count_vm_event(THP_FAULT_FALLBACK);
1169                 if (is_huge_zero_pmd(orig_pmd)) {
1170                         ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1171                                         address, pmd, orig_pmd, haddr);
1172                 } else {
1173                         ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1174                                         pmd, orig_pmd, page, haddr);
1175                         if (ret & VM_FAULT_OOM)
1176                                 split_huge_page(page);
1177                         put_page(page);
1178                 }
1179                 goto out;
1180         }
1181         count_vm_event(THP_FAULT_ALLOC);
1182
1183         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1184                 put_page(new_page);
1185                 if (page) {
1186                         split_huge_page(page);
1187                         put_page(page);
1188                 }
1189                 ret |= VM_FAULT_OOM;
1190                 goto out;
1191         }
1192
1193         if (is_huge_zero_pmd(orig_pmd))
1194                 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1195         else
1196                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1197         __SetPageUptodate(new_page);
1198
1199         mmun_start = haddr;
1200         mmun_end   = haddr + HPAGE_PMD_SIZE;
1201         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1202
1203         spin_lock(&mm->page_table_lock);
1204         if (page)
1205                 put_page(page);
1206         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1207                 spin_unlock(&mm->page_table_lock);
1208                 mem_cgroup_uncharge_page(new_page);
1209                 put_page(new_page);
1210                 goto out_mn;
1211         } else {
1212                 pmd_t entry;
1213                 entry = mk_huge_pmd(new_page, vma);
1214                 pmdp_clear_flush(vma, haddr, pmd);
1215                 page_add_new_anon_rmap(new_page, vma, haddr);
1216                 set_pmd_at(mm, haddr, pmd, entry);
1217                 update_mmu_cache_pmd(vma, address, pmd);
1218                 if (is_huge_zero_pmd(orig_pmd)) {
1219                         add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1220                         put_huge_zero_page();
1221                 } else {
1222                         VM_BUG_ON(!PageHead(page));
1223                         page_remove_rmap(page);
1224                         put_page(page);
1225                 }
1226                 ret |= VM_FAULT_WRITE;
1227         }
1228         spin_unlock(&mm->page_table_lock);
1229 out_mn:
1230         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1231 out:
1232         return ret;
1233 out_unlock:
1234         spin_unlock(&mm->page_table_lock);
1235         return ret;
1236 }
1237
1238 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1239                                    unsigned long addr,
1240                                    pmd_t *pmd,
1241                                    unsigned int flags)
1242 {
1243         struct mm_struct *mm = vma->vm_mm;
1244         struct page *page = NULL;
1245
1246         assert_spin_locked(&mm->page_table_lock);
1247
1248         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1249                 goto out;
1250
1251         /* Avoid dumping huge zero page */
1252         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1253                 return ERR_PTR(-EFAULT);
1254
1255         page = pmd_page(*pmd);
1256         VM_BUG_ON(!PageHead(page));
1257         if (flags & FOLL_TOUCH) {
1258                 pmd_t _pmd;
1259                 /*
1260                  * We should set the dirty bit only for FOLL_WRITE but
1261                  * for now the dirty bit in the pmd is meaningless.
1262                  * And if the dirty bit will become meaningful and
1263                  * we'll only set it with FOLL_WRITE, an atomic
1264                  * set_bit will be required on the pmd to set the
1265                  * young bit, instead of the current set_pmd_at.
1266                  */
1267                 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1268                 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1269         }
1270         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1271                 if (page->mapping && trylock_page(page)) {
1272                         lru_add_drain();
1273                         if (page->mapping)
1274                                 mlock_vma_page(page);
1275                         unlock_page(page);
1276                 }
1277         }
1278         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1279         VM_BUG_ON(!PageCompound(page));
1280         if (flags & FOLL_GET)
1281                 get_page_foll(page);
1282
1283 out:
1284         return page;
1285 }
1286
1287 /* NUMA hinting page fault entry point for trans huge pmds */
1288 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1289                                 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1290 {
1291         struct anon_vma *anon_vma = NULL;
1292         struct page *page;
1293         unsigned long haddr = addr & HPAGE_PMD_MASK;
1294         int page_nid = -1, this_nid = numa_node_id();
1295         int target_nid;
1296         bool page_locked;
1297         bool migrated = false;
1298
1299         spin_lock(&mm->page_table_lock);
1300         if (unlikely(!pmd_same(pmd, *pmdp)))
1301                 goto out_unlock;
1302
1303         page = pmd_page(pmd);
1304         page_nid = page_to_nid(page);
1305         count_vm_numa_event(NUMA_HINT_FAULTS);
1306         if (page_nid == this_nid)
1307                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1308
1309         /*
1310          * Acquire the page lock to serialise THP migrations but avoid dropping
1311          * page_table_lock if at all possible
1312          */
1313         page_locked = trylock_page(page);
1314         target_nid = mpol_misplaced(page, vma, haddr);
1315         if (target_nid == -1) {
1316                 /* If the page was locked, there are no parallel migrations */
1317                 if (page_locked)
1318                         goto clear_pmdnuma;
1319
1320                 /*
1321                  * Otherwise wait for potential migrations and retry. We do
1322                  * relock and check_same as the page may no longer be mapped.
1323                  * As the fault is being retried, do not account for it.
1324                  */
1325                 spin_unlock(&mm->page_table_lock);
1326                 wait_on_page_locked(page);
1327                 page_nid = -1;
1328                 goto out;
1329         }
1330
1331         /* Page is misplaced, serialise migrations and parallel THP splits */
1332         get_page(page);
1333         spin_unlock(&mm->page_table_lock);
1334         if (!page_locked)
1335                 lock_page(page);
1336         anon_vma = page_lock_anon_vma_read(page);
1337
1338         /* Confirm the PTE did not while locked */
1339         spin_lock(&mm->page_table_lock);
1340         if (unlikely(!pmd_same(pmd, *pmdp))) {
1341                 unlock_page(page);
1342                 put_page(page);
1343                 page_nid = -1;
1344                 goto out_unlock;
1345         }
1346
1347         /*
1348          * Migrate the THP to the requested node, returns with page unlocked
1349          * and pmd_numa cleared.
1350          */
1351         spin_unlock(&mm->page_table_lock);
1352         migrated = migrate_misplaced_transhuge_page(mm, vma,
1353                                 pmdp, pmd, addr, page, target_nid);
1354         if (migrated)
1355                 page_nid = target_nid;
1356
1357         goto out;
1358 clear_pmdnuma:
1359         BUG_ON(!PageLocked(page));
1360         pmd = pmd_mknonnuma(pmd);
1361         set_pmd_at(mm, haddr, pmdp, pmd);
1362         VM_BUG_ON(pmd_numa(*pmdp));
1363         update_mmu_cache_pmd(vma, addr, pmdp);
1364         unlock_page(page);
1365 out_unlock:
1366         spin_unlock(&mm->page_table_lock);
1367
1368 out:
1369         if (anon_vma)
1370                 page_unlock_anon_vma_read(anon_vma);
1371
1372         if (page_nid != -1)
1373                 task_numa_fault(page_nid, HPAGE_PMD_NR, migrated);
1374
1375         return 0;
1376 }
1377
1378 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1379                  pmd_t *pmd, unsigned long addr)
1380 {
1381         int ret = 0;
1382
1383         if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1384                 struct page *page;
1385                 pgtable_t pgtable;
1386                 pmd_t orig_pmd;
1387                 pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1388                 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1389                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1390                 if (is_huge_zero_pmd(orig_pmd)) {
1391                         tlb->mm->nr_ptes--;
1392                         spin_unlock(&tlb->mm->page_table_lock);
1393                         put_huge_zero_page();
1394                 } else {
1395                         page = pmd_page(orig_pmd);
1396                         page_remove_rmap(page);
1397                         VM_BUG_ON(page_mapcount(page) < 0);
1398                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1399                         VM_BUG_ON(!PageHead(page));
1400                         tlb->mm->nr_ptes--;
1401                         spin_unlock(&tlb->mm->page_table_lock);
1402                         tlb_remove_page(tlb, page);
1403                 }
1404                 pte_free(tlb->mm, pgtable);
1405                 ret = 1;
1406         }
1407         return ret;
1408 }
1409
1410 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1411                 unsigned long addr, unsigned long end,
1412                 unsigned char *vec)
1413 {
1414         int ret = 0;
1415
1416         if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1417                 /*
1418                  * All logical pages in the range are present
1419                  * if backed by a huge page.
1420                  */
1421                 spin_unlock(&vma->vm_mm->page_table_lock);
1422                 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1423                 ret = 1;
1424         }
1425
1426         return ret;
1427 }
1428
1429 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1430                   unsigned long old_addr,
1431                   unsigned long new_addr, unsigned long old_end,
1432                   pmd_t *old_pmd, pmd_t *new_pmd)
1433 {
1434         int ret = 0;
1435         pmd_t pmd;
1436
1437         struct mm_struct *mm = vma->vm_mm;
1438
1439         if ((old_addr & ~HPAGE_PMD_MASK) ||
1440             (new_addr & ~HPAGE_PMD_MASK) ||
1441             old_end - old_addr < HPAGE_PMD_SIZE ||
1442             (new_vma->vm_flags & VM_NOHUGEPAGE))
1443                 goto out;
1444
1445         /*
1446          * The destination pmd shouldn't be established, free_pgtables()
1447          * should have release it.
1448          */
1449         if (WARN_ON(!pmd_none(*new_pmd))) {
1450                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1451                 goto out;
1452         }
1453
1454         ret = __pmd_trans_huge_lock(old_pmd, vma);
1455         if (ret == 1) {
1456                 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1457                 VM_BUG_ON(!pmd_none(*new_pmd));
1458                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1459                 spin_unlock(&mm->page_table_lock);
1460         }
1461 out:
1462         return ret;
1463 }
1464
1465 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1466                 unsigned long addr, pgprot_t newprot, int prot_numa)
1467 {
1468         struct mm_struct *mm = vma->vm_mm;
1469         int ret = 0;
1470
1471         if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1472                 pmd_t entry;
1473                 entry = pmdp_get_and_clear(mm, addr, pmd);
1474                 if (!prot_numa) {
1475                         entry = pmd_modify(entry, newprot);
1476                         BUG_ON(pmd_write(entry));
1477                 } else {
1478                         struct page *page = pmd_page(*pmd);
1479
1480                         /* only check non-shared pages */
1481                         if (page_mapcount(page) == 1 &&
1482                             !pmd_numa(*pmd)) {
1483                                 entry = pmd_mknuma(entry);
1484                         }
1485                 }
1486                 set_pmd_at(mm, addr, pmd, entry);
1487                 spin_unlock(&vma->vm_mm->page_table_lock);
1488                 ret = 1;
1489         }
1490
1491         return ret;
1492 }
1493
1494 /*
1495  * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1496  * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1497  *
1498  * Note that if it returns 1, this routine returns without unlocking page
1499  * table locks. So callers must unlock them.
1500  */
1501 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1502 {
1503         spin_lock(&vma->vm_mm->page_table_lock);
1504         if (likely(pmd_trans_huge(*pmd))) {
1505                 if (unlikely(pmd_trans_splitting(*pmd))) {
1506                         spin_unlock(&vma->vm_mm->page_table_lock);
1507                         wait_split_huge_page(vma->anon_vma, pmd);
1508                         return -1;
1509                 } else {
1510                         /* Thp mapped by 'pmd' is stable, so we can
1511                          * handle it as it is. */
1512                         return 1;
1513                 }
1514         }
1515         spin_unlock(&vma->vm_mm->page_table_lock);
1516         return 0;
1517 }
1518
1519 pmd_t *page_check_address_pmd(struct page *page,
1520                               struct mm_struct *mm,
1521                               unsigned long address,
1522                               enum page_check_address_pmd_flag flag)
1523 {
1524         pmd_t *pmd, *ret = NULL;
1525
1526         if (address & ~HPAGE_PMD_MASK)
1527                 goto out;
1528
1529         pmd = mm_find_pmd(mm, address);
1530         if (!pmd)
1531                 goto out;
1532         if (pmd_none(*pmd))
1533                 goto out;
1534         if (pmd_page(*pmd) != page)
1535                 goto out;
1536         /*
1537          * split_vma() may create temporary aliased mappings. There is
1538          * no risk as long as all huge pmd are found and have their
1539          * splitting bit set before __split_huge_page_refcount
1540          * runs. Finding the same huge pmd more than once during the
1541          * same rmap walk is not a problem.
1542          */
1543         if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1544             pmd_trans_splitting(*pmd))
1545                 goto out;
1546         if (pmd_trans_huge(*pmd)) {
1547                 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1548                           !pmd_trans_splitting(*pmd));
1549                 ret = pmd;
1550         }
1551 out:
1552         return ret;
1553 }
1554
1555 static int __split_huge_page_splitting(struct page *page,
1556                                        struct vm_area_struct *vma,
1557                                        unsigned long address)
1558 {
1559         struct mm_struct *mm = vma->vm_mm;
1560         pmd_t *pmd;
1561         int ret = 0;
1562         /* For mmu_notifiers */
1563         const unsigned long mmun_start = address;
1564         const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1565
1566         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1567         spin_lock(&mm->page_table_lock);
1568         pmd = page_check_address_pmd(page, mm, address,
1569                                      PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1570         if (pmd) {
1571                 /*
1572                  * We can't temporarily set the pmd to null in order
1573                  * to split it, the pmd must remain marked huge at all
1574                  * times or the VM won't take the pmd_trans_huge paths
1575                  * and it won't wait on the anon_vma->root->rwsem to
1576                  * serialize against split_huge_page*.
1577                  */
1578                 pmdp_splitting_flush(vma, address, pmd);
1579                 ret = 1;
1580         }
1581         spin_unlock(&mm->page_table_lock);
1582         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1583
1584         return ret;
1585 }
1586
1587 static void __split_huge_page_refcount(struct page *page,
1588                                        struct list_head *list)
1589 {
1590         int i;
1591         struct zone *zone = page_zone(page);
1592         struct lruvec *lruvec;
1593         int tail_count = 0;
1594
1595         /* prevent PageLRU to go away from under us, and freeze lru stats */
1596         spin_lock_irq(&zone->lru_lock);
1597         lruvec = mem_cgroup_page_lruvec(page, zone);
1598
1599         compound_lock(page);
1600         /* complete memcg works before add pages to LRU */
1601         mem_cgroup_split_huge_fixup(page);
1602
1603         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1604                 struct page *page_tail = page + i;
1605
1606                 /* tail_page->_mapcount cannot change */
1607                 BUG_ON(page_mapcount(page_tail) < 0);
1608                 tail_count += page_mapcount(page_tail);
1609                 /* check for overflow */
1610                 BUG_ON(tail_count < 0);
1611                 BUG_ON(atomic_read(&page_tail->_count) != 0);
1612                 /*
1613                  * tail_page->_count is zero and not changing from
1614                  * under us. But get_page_unless_zero() may be running
1615                  * from under us on the tail_page. If we used
1616                  * atomic_set() below instead of atomic_add(), we
1617                  * would then run atomic_set() concurrently with
1618                  * get_page_unless_zero(), and atomic_set() is
1619                  * implemented in C not using locked ops. spin_unlock
1620                  * on x86 sometime uses locked ops because of PPro
1621                  * errata 66, 92, so unless somebody can guarantee
1622                  * atomic_set() here would be safe on all archs (and
1623                  * not only on x86), it's safer to use atomic_add().
1624                  */
1625                 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1626                            &page_tail->_count);
1627
1628                 /* after clearing PageTail the gup refcount can be released */
1629                 smp_mb();
1630
1631                 /*
1632                  * retain hwpoison flag of the poisoned tail page:
1633                  *   fix for the unsuitable process killed on Guest Machine(KVM)
1634                  *   by the memory-failure.
1635                  */
1636                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1637                 page_tail->flags |= (page->flags &
1638                                      ((1L << PG_referenced) |
1639                                       (1L << PG_swapbacked) |
1640                                       (1L << PG_mlocked) |
1641                                       (1L << PG_uptodate)));
1642                 page_tail->flags |= (1L << PG_dirty);
1643
1644                 /* clear PageTail before overwriting first_page */
1645                 smp_wmb();
1646
1647                 /*
1648                  * __split_huge_page_splitting() already set the
1649                  * splitting bit in all pmd that could map this
1650                  * hugepage, that will ensure no CPU can alter the
1651                  * mapcount on the head page. The mapcount is only
1652                  * accounted in the head page and it has to be
1653                  * transferred to all tail pages in the below code. So
1654                  * for this code to be safe, the split the mapcount
1655                  * can't change. But that doesn't mean userland can't
1656                  * keep changing and reading the page contents while
1657                  * we transfer the mapcount, so the pmd splitting
1658                  * status is achieved setting a reserved bit in the
1659                  * pmd, not by clearing the present bit.
1660                 */
1661                 page_tail->_mapcount = page->_mapcount;
1662
1663                 BUG_ON(page_tail->mapping);
1664                 page_tail->mapping = page->mapping;
1665
1666                 page_tail->index = page->index + i;
1667                 page_nid_xchg_last(page_tail, page_nid_last(page));
1668
1669                 BUG_ON(!PageAnon(page_tail));
1670                 BUG_ON(!PageUptodate(page_tail));
1671                 BUG_ON(!PageDirty(page_tail));
1672                 BUG_ON(!PageSwapBacked(page_tail));
1673
1674                 lru_add_page_tail(page, page_tail, lruvec, list);
1675         }
1676         atomic_sub(tail_count, &page->_count);
1677         BUG_ON(atomic_read(&page->_count) <= 0);
1678
1679         __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1680         __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1681
1682         ClearPageCompound(page);
1683         compound_unlock(page);
1684         spin_unlock_irq(&zone->lru_lock);
1685
1686         for (i = 1; i < HPAGE_PMD_NR; i++) {
1687                 struct page *page_tail = page + i;
1688                 BUG_ON(page_count(page_tail) <= 0);
1689                 /*
1690                  * Tail pages may be freed if there wasn't any mapping
1691                  * like if add_to_swap() is running on a lru page that
1692                  * had its mapping zapped. And freeing these pages
1693                  * requires taking the lru_lock so we do the put_page
1694                  * of the tail pages after the split is complete.
1695                  */
1696                 put_page(page_tail);
1697         }
1698
1699         /*
1700          * Only the head page (now become a regular page) is required
1701          * to be pinned by the caller.
1702          */
1703         BUG_ON(page_count(page) <= 0);
1704 }
1705
1706 static int __split_huge_page_map(struct page *page,
1707                                  struct vm_area_struct *vma,
1708                                  unsigned long address)
1709 {
1710         struct mm_struct *mm = vma->vm_mm;
1711         pmd_t *pmd, _pmd;
1712         int ret = 0, i;
1713         pgtable_t pgtable;
1714         unsigned long haddr;
1715
1716         spin_lock(&mm->page_table_lock);
1717         pmd = page_check_address_pmd(page, mm, address,
1718                                      PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1719         if (pmd) {
1720                 pgtable = pgtable_trans_huge_withdraw(mm);
1721                 pmd_populate(mm, &_pmd, pgtable);
1722
1723                 haddr = address;
1724                 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1725                         pte_t *pte, entry;
1726                         BUG_ON(PageCompound(page+i));
1727                         entry = mk_pte(page + i, vma->vm_page_prot);
1728                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1729                         if (!pmd_write(*pmd))
1730                                 entry = pte_wrprotect(entry);
1731                         else
1732                                 BUG_ON(page_mapcount(page) != 1);
1733                         if (!pmd_young(*pmd))
1734                                 entry = pte_mkold(entry);
1735                         if (pmd_numa(*pmd))
1736                                 entry = pte_mknuma(entry);
1737                         pte = pte_offset_map(&_pmd, haddr);
1738                         BUG_ON(!pte_none(*pte));
1739                         set_pte_at(mm, haddr, pte, entry);
1740                         pte_unmap(pte);
1741                 }
1742
1743                 smp_wmb(); /* make pte visible before pmd */
1744                 /*
1745                  * Up to this point the pmd is present and huge and
1746                  * userland has the whole access to the hugepage
1747                  * during the split (which happens in place). If we
1748                  * overwrite the pmd with the not-huge version
1749                  * pointing to the pte here (which of course we could
1750                  * if all CPUs were bug free), userland could trigger
1751                  * a small page size TLB miss on the small sized TLB
1752                  * while the hugepage TLB entry is still established
1753                  * in the huge TLB. Some CPU doesn't like that. See
1754                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1755                  * Erratum 383 on page 93. Intel should be safe but is
1756                  * also warns that it's only safe if the permission
1757                  * and cache attributes of the two entries loaded in
1758                  * the two TLB is identical (which should be the case
1759                  * here). But it is generally safer to never allow
1760                  * small and huge TLB entries for the same virtual
1761                  * address to be loaded simultaneously. So instead of
1762                  * doing "pmd_populate(); flush_tlb_range();" we first
1763                  * mark the current pmd notpresent (atomically because
1764                  * here the pmd_trans_huge and pmd_trans_splitting
1765                  * must remain set at all times on the pmd until the
1766                  * split is complete for this pmd), then we flush the
1767                  * SMP TLB and finally we write the non-huge version
1768                  * of the pmd entry with pmd_populate.
1769                  */
1770                 pmdp_invalidate(vma, address, pmd);
1771                 pmd_populate(mm, pmd, pgtable);
1772                 ret = 1;
1773         }
1774         spin_unlock(&mm->page_table_lock);
1775
1776         return ret;
1777 }
1778
1779 /* must be called with anon_vma->root->rwsem held */
1780 static void __split_huge_page(struct page *page,
1781                               struct anon_vma *anon_vma,
1782                               struct list_head *list)
1783 {
1784         int mapcount, mapcount2;
1785         pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1786         struct anon_vma_chain *avc;
1787
1788         BUG_ON(!PageHead(page));
1789         BUG_ON(PageTail(page));
1790
1791         mapcount = 0;
1792         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1793                 struct vm_area_struct *vma = avc->vma;
1794                 unsigned long addr = vma_address(page, vma);
1795                 BUG_ON(is_vma_temporary_stack(vma));
1796                 mapcount += __split_huge_page_splitting(page, vma, addr);
1797         }
1798         /*
1799          * It is critical that new vmas are added to the tail of the
1800          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1801          * and establishes a child pmd before
1802          * __split_huge_page_splitting() freezes the parent pmd (so if
1803          * we fail to prevent copy_huge_pmd() from running until the
1804          * whole __split_huge_page() is complete), we will still see
1805          * the newly established pmd of the child later during the
1806          * walk, to be able to set it as pmd_trans_splitting too.
1807          */
1808         if (mapcount != page_mapcount(page))
1809                 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1810                        mapcount, page_mapcount(page));
1811         BUG_ON(mapcount != page_mapcount(page));
1812
1813         __split_huge_page_refcount(page, list);
1814
1815         mapcount2 = 0;
1816         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1817                 struct vm_area_struct *vma = avc->vma;
1818                 unsigned long addr = vma_address(page, vma);
1819                 BUG_ON(is_vma_temporary_stack(vma));
1820                 mapcount2 += __split_huge_page_map(page, vma, addr);
1821         }
1822         if (mapcount != mapcount2)
1823                 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1824                        mapcount, mapcount2, page_mapcount(page));
1825         BUG_ON(mapcount != mapcount2);
1826 }
1827
1828 /*
1829  * Split a hugepage into normal pages. This doesn't change the position of head
1830  * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1831  * @list. Both head page and tail pages will inherit mapping, flags, and so on
1832  * from the hugepage.
1833  * Return 0 if the hugepage is split successfully otherwise return 1.
1834  */
1835 int split_huge_page_to_list(struct page *page, struct list_head *list)
1836 {
1837         struct anon_vma *anon_vma;
1838         int ret = 1;
1839
1840         BUG_ON(is_huge_zero_page(page));
1841         BUG_ON(!PageAnon(page));
1842
1843         /*
1844          * The caller does not necessarily hold an mmap_sem that would prevent
1845          * the anon_vma disappearing so we first we take a reference to it
1846          * and then lock the anon_vma for write. This is similar to
1847          * page_lock_anon_vma_read except the write lock is taken to serialise
1848          * against parallel split or collapse operations.
1849          */
1850         anon_vma = page_get_anon_vma(page);
1851         if (!anon_vma)
1852                 goto out;
1853         anon_vma_lock_write(anon_vma);
1854
1855         ret = 0;
1856         if (!PageCompound(page))
1857                 goto out_unlock;
1858
1859         BUG_ON(!PageSwapBacked(page));
1860         __split_huge_page(page, anon_vma, list);
1861         count_vm_event(THP_SPLIT);
1862
1863         BUG_ON(PageCompound(page));
1864 out_unlock:
1865         anon_vma_unlock_write(anon_vma);
1866         put_anon_vma(anon_vma);
1867 out:
1868         return ret;
1869 }
1870
1871 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1872
1873 int hugepage_madvise(struct vm_area_struct *vma,
1874                      unsigned long *vm_flags, int advice)
1875 {
1876         struct mm_struct *mm = vma->vm_mm;
1877
1878         switch (advice) {
1879         case MADV_HUGEPAGE:
1880                 /*
1881                  * Be somewhat over-protective like KSM for now!
1882                  */
1883                 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1884                         return -EINVAL;
1885                 if (mm->def_flags & VM_NOHUGEPAGE)
1886                         return -EINVAL;
1887                 *vm_flags &= ~VM_NOHUGEPAGE;
1888                 *vm_flags |= VM_HUGEPAGE;
1889                 /*
1890                  * If the vma become good for khugepaged to scan,
1891                  * register it here without waiting a page fault that
1892                  * may not happen any time soon.
1893                  */
1894                 if (unlikely(khugepaged_enter_vma_merge(vma)))
1895                         return -ENOMEM;
1896                 break;
1897         case MADV_NOHUGEPAGE:
1898                 /*
1899                  * Be somewhat over-protective like KSM for now!
1900                  */
1901                 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1902                         return -EINVAL;
1903                 *vm_flags &= ~VM_HUGEPAGE;
1904                 *vm_flags |= VM_NOHUGEPAGE;
1905                 /*
1906                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1907                  * this vma even if we leave the mm registered in khugepaged if
1908                  * it got registered before VM_NOHUGEPAGE was set.
1909                  */
1910                 break;
1911         }
1912
1913         return 0;
1914 }
1915
1916 static int __init khugepaged_slab_init(void)
1917 {
1918         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1919                                           sizeof(struct mm_slot),
1920                                           __alignof__(struct mm_slot), 0, NULL);
1921         if (!mm_slot_cache)
1922                 return -ENOMEM;
1923
1924         return 0;
1925 }
1926
1927 static inline struct mm_slot *alloc_mm_slot(void)
1928 {
1929         if (!mm_slot_cache)     /* initialization failed */
1930                 return NULL;
1931         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1932 }
1933
1934 static inline void free_mm_slot(struct mm_slot *mm_slot)
1935 {
1936         kmem_cache_free(mm_slot_cache, mm_slot);
1937 }
1938
1939 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1940 {
1941         struct mm_slot *mm_slot;
1942
1943         hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1944                 if (mm == mm_slot->mm)
1945                         return mm_slot;
1946
1947         return NULL;
1948 }
1949
1950 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1951                                     struct mm_slot *mm_slot)
1952 {
1953         mm_slot->mm = mm;
1954         hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1955 }
1956
1957 static inline int khugepaged_test_exit(struct mm_struct *mm)
1958 {
1959         return atomic_read(&mm->mm_users) == 0;
1960 }
1961
1962 int __khugepaged_enter(struct mm_struct *mm)
1963 {
1964         struct mm_slot *mm_slot;
1965         int wakeup;
1966
1967         mm_slot = alloc_mm_slot();
1968         if (!mm_slot)
1969                 return -ENOMEM;
1970
1971         /* __khugepaged_exit() must not run from under us */
1972         VM_BUG_ON(khugepaged_test_exit(mm));
1973         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1974                 free_mm_slot(mm_slot);
1975                 return 0;
1976         }
1977
1978         spin_lock(&khugepaged_mm_lock);
1979         insert_to_mm_slots_hash(mm, mm_slot);
1980         /*
1981          * Insert just behind the scanning cursor, to let the area settle
1982          * down a little.
1983          */
1984         wakeup = list_empty(&khugepaged_scan.mm_head);
1985         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1986         spin_unlock(&khugepaged_mm_lock);
1987
1988         atomic_inc(&mm->mm_count);
1989         if (wakeup)
1990                 wake_up_interruptible(&khugepaged_wait);
1991
1992         return 0;
1993 }
1994
1995 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1996 {
1997         unsigned long hstart, hend;
1998         if (!vma->anon_vma)
1999                 /*
2000                  * Not yet faulted in so we will register later in the
2001                  * page fault if needed.
2002                  */
2003                 return 0;
2004         if (vma->vm_ops)
2005                 /* khugepaged not yet working on file or special mappings */
2006                 return 0;
2007         VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2008         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2009         hend = vma->vm_end & HPAGE_PMD_MASK;
2010         if (hstart < hend)
2011                 return khugepaged_enter(vma);
2012         return 0;
2013 }
2014
2015 void __khugepaged_exit(struct mm_struct *mm)
2016 {
2017         struct mm_slot *mm_slot;
2018         int free = 0;
2019
2020         spin_lock(&khugepaged_mm_lock);
2021         mm_slot = get_mm_slot(mm);
2022         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2023                 hash_del(&mm_slot->hash);
2024                 list_del(&mm_slot->mm_node);
2025                 free = 1;
2026         }
2027         spin_unlock(&khugepaged_mm_lock);
2028
2029         if (free) {
2030                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2031                 free_mm_slot(mm_slot);
2032                 mmdrop(mm);
2033         } else if (mm_slot) {
2034                 /*
2035                  * This is required to serialize against
2036                  * khugepaged_test_exit() (which is guaranteed to run
2037                  * under mmap sem read mode). Stop here (after we
2038                  * return all pagetables will be destroyed) until
2039                  * khugepaged has finished working on the pagetables
2040                  * under the mmap_sem.
2041                  */
2042                 down_write(&mm->mmap_sem);
2043                 up_write(&mm->mmap_sem);
2044         }
2045 }
2046
2047 static void release_pte_page(struct page *page)
2048 {
2049         /* 0 stands for page_is_file_cache(page) == false */
2050         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2051         unlock_page(page);
2052         putback_lru_page(page);
2053 }
2054
2055 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2056 {
2057         while (--_pte >= pte) {
2058                 pte_t pteval = *_pte;
2059                 if (!pte_none(pteval))
2060                         release_pte_page(pte_page(pteval));
2061         }
2062 }
2063
2064 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2065                                         unsigned long address,
2066                                         pte_t *pte)
2067 {
2068         struct page *page;
2069         pte_t *_pte;
2070         int referenced = 0, none = 0;
2071         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2072              _pte++, address += PAGE_SIZE) {
2073                 pte_t pteval = *_pte;
2074                 if (pte_none(pteval)) {
2075                         if (++none <= khugepaged_max_ptes_none)
2076                                 continue;
2077                         else
2078                                 goto out;
2079                 }
2080                 if (!pte_present(pteval) || !pte_write(pteval))
2081                         goto out;
2082                 page = vm_normal_page(vma, address, pteval);
2083                 if (unlikely(!page))
2084                         goto out;
2085
2086                 VM_BUG_ON(PageCompound(page));
2087                 BUG_ON(!PageAnon(page));
2088                 VM_BUG_ON(!PageSwapBacked(page));
2089
2090                 /* cannot use mapcount: can't collapse if there's a gup pin */
2091                 if (page_count(page) != 1)
2092                         goto out;
2093                 /*
2094                  * We can do it before isolate_lru_page because the
2095                  * page can't be freed from under us. NOTE: PG_lock
2096                  * is needed to serialize against split_huge_page
2097                  * when invoked from the VM.
2098                  */
2099                 if (!trylock_page(page))
2100                         goto out;
2101                 /*
2102                  * Isolate the page to avoid collapsing an hugepage
2103                  * currently in use by the VM.
2104                  */
2105                 if (isolate_lru_page(page)) {
2106                         unlock_page(page);
2107                         goto out;
2108                 }
2109                 /* 0 stands for page_is_file_cache(page) == false */
2110                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2111                 VM_BUG_ON(!PageLocked(page));
2112                 VM_BUG_ON(PageLRU(page));
2113
2114                 /* If there is no mapped pte young don't collapse the page */
2115                 if (pte_young(pteval) || PageReferenced(page) ||
2116                     mmu_notifier_test_young(vma->vm_mm, address))
2117                         referenced = 1;
2118         }
2119         if (likely(referenced))
2120                 return 1;
2121 out:
2122         release_pte_pages(pte, _pte);
2123         return 0;
2124 }
2125
2126 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2127                                       struct vm_area_struct *vma,
2128                                       unsigned long address,
2129                                       spinlock_t *ptl)
2130 {
2131         pte_t *_pte;
2132         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2133                 pte_t pteval = *_pte;
2134                 struct page *src_page;
2135
2136                 if (pte_none(pteval)) {
2137                         clear_user_highpage(page, address);
2138                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2139                 } else {
2140                         src_page = pte_page(pteval);
2141                         copy_user_highpage(page, src_page, address, vma);
2142                         VM_BUG_ON(page_mapcount(src_page) != 1);
2143                         release_pte_page(src_page);
2144                         /*
2145                          * ptl mostly unnecessary, but preempt has to
2146                          * be disabled to update the per-cpu stats
2147                          * inside page_remove_rmap().
2148                          */
2149                         spin_lock(ptl);
2150                         /*
2151                          * paravirt calls inside pte_clear here are
2152                          * superfluous.
2153                          */
2154                         pte_clear(vma->vm_mm, address, _pte);
2155                         page_remove_rmap(src_page);
2156                         spin_unlock(ptl);
2157                         free_page_and_swap_cache(src_page);
2158                 }
2159
2160                 address += PAGE_SIZE;
2161                 page++;
2162         }
2163 }
2164
2165 static void khugepaged_alloc_sleep(void)
2166 {
2167         wait_event_freezable_timeout(khugepaged_wait, false,
2168                         msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2169 }
2170
2171 #ifdef CONFIG_NUMA
2172 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2173 {
2174         if (IS_ERR(*hpage)) {
2175                 if (!*wait)
2176                         return false;
2177
2178                 *wait = false;
2179                 *hpage = NULL;
2180                 khugepaged_alloc_sleep();
2181         } else if (*hpage) {
2182                 put_page(*hpage);
2183                 *hpage = NULL;
2184         }
2185
2186         return true;
2187 }
2188
2189 static struct page
2190 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2191                        struct vm_area_struct *vma, unsigned long address,
2192                        int node)
2193 {
2194         VM_BUG_ON(*hpage);
2195         /*
2196          * Allocate the page while the vma is still valid and under
2197          * the mmap_sem read mode so there is no memory allocation
2198          * later when we take the mmap_sem in write mode. This is more
2199          * friendly behavior (OTOH it may actually hide bugs) to
2200          * filesystems in userland with daemons allocating memory in
2201          * the userland I/O paths.  Allocating memory with the
2202          * mmap_sem in read mode is good idea also to allow greater
2203          * scalability.
2204          */
2205         *hpage  = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2206                                       node, __GFP_OTHER_NODE);
2207
2208         /*
2209          * After allocating the hugepage, release the mmap_sem read lock in
2210          * preparation for taking it in write mode.
2211          */
2212         up_read(&mm->mmap_sem);
2213         if (unlikely(!*hpage)) {
2214                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2215                 *hpage = ERR_PTR(-ENOMEM);
2216                 return NULL;
2217         }
2218
2219         count_vm_event(THP_COLLAPSE_ALLOC);
2220         return *hpage;
2221 }
2222 #else
2223 static struct page *khugepaged_alloc_hugepage(bool *wait)
2224 {
2225         struct page *hpage;
2226
2227         do {
2228                 hpage = alloc_hugepage(khugepaged_defrag());
2229                 if (!hpage) {
2230                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2231                         if (!*wait)
2232                                 return NULL;
2233
2234                         *wait = false;
2235                         khugepaged_alloc_sleep();
2236                 } else
2237                         count_vm_event(THP_COLLAPSE_ALLOC);
2238         } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2239
2240         return hpage;
2241 }
2242
2243 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2244 {
2245         if (!*hpage)
2246                 *hpage = khugepaged_alloc_hugepage(wait);
2247
2248         if (unlikely(!*hpage))
2249                 return false;
2250
2251         return true;
2252 }
2253
2254 static struct page
2255 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2256                        struct vm_area_struct *vma, unsigned long address,
2257                        int node)
2258 {
2259         up_read(&mm->mmap_sem);
2260         VM_BUG_ON(!*hpage);
2261         return  *hpage;
2262 }
2263 #endif
2264
2265 static bool hugepage_vma_check(struct vm_area_struct *vma)
2266 {
2267         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2268             (vma->vm_flags & VM_NOHUGEPAGE))
2269                 return false;
2270
2271         if (!vma->anon_vma || vma->vm_ops)
2272                 return false;
2273         if (is_vma_temporary_stack(vma))
2274                 return false;
2275         VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2276         return true;
2277 }
2278
2279 static void collapse_huge_page(struct mm_struct *mm,
2280                                    unsigned long address,
2281                                    struct page **hpage,
2282                                    struct vm_area_struct *vma,
2283                                    int node)
2284 {
2285         pmd_t *pmd, _pmd;
2286         pte_t *pte;
2287         pgtable_t pgtable;
2288         struct page *new_page;
2289         spinlock_t *ptl;
2290         int isolated;
2291         unsigned long hstart, hend;
2292         unsigned long mmun_start;       /* For mmu_notifiers */
2293         unsigned long mmun_end;         /* For mmu_notifiers */
2294
2295         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2296
2297         /* release the mmap_sem read lock. */
2298         new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2299         if (!new_page)
2300                 return;
2301
2302         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2303                 return;
2304
2305         /*
2306          * Prevent all access to pagetables with the exception of
2307          * gup_fast later hanlded by the ptep_clear_flush and the VM
2308          * handled by the anon_vma lock + PG_lock.
2309          */
2310         down_write(&mm->mmap_sem);
2311         if (unlikely(khugepaged_test_exit(mm)))
2312                 goto out;
2313
2314         vma = find_vma(mm, address);
2315         if (!vma)
2316                 goto out;
2317         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2318         hend = vma->vm_end & HPAGE_PMD_MASK;
2319         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2320                 goto out;
2321         if (!hugepage_vma_check(vma))
2322                 goto out;
2323         pmd = mm_find_pmd(mm, address);
2324         if (!pmd)
2325                 goto out;
2326         if (pmd_trans_huge(*pmd))
2327                 goto out;
2328
2329         anon_vma_lock_write(vma->anon_vma);
2330
2331         pte = pte_offset_map(pmd, address);
2332         ptl = pte_lockptr(mm, pmd);
2333
2334         mmun_start = address;
2335         mmun_end   = address + HPAGE_PMD_SIZE;
2336         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2337         spin_lock(&mm->page_table_lock); /* probably unnecessary */
2338         /*
2339          * After this gup_fast can't run anymore. This also removes
2340          * any huge TLB entry from the CPU so we won't allow
2341          * huge and small TLB entries for the same virtual address
2342          * to avoid the risk of CPU bugs in that area.
2343          */
2344         _pmd = pmdp_clear_flush(vma, address, pmd);
2345         spin_unlock(&mm->page_table_lock);
2346         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2347
2348         spin_lock(ptl);
2349         isolated = __collapse_huge_page_isolate(vma, address, pte);
2350         spin_unlock(ptl);
2351
2352         if (unlikely(!isolated)) {
2353                 pte_unmap(pte);
2354                 spin_lock(&mm->page_table_lock);
2355                 BUG_ON(!pmd_none(*pmd));
2356                 /*
2357                  * We can only use set_pmd_at when establishing
2358                  * hugepmds and never for establishing regular pmds that
2359                  * points to regular pagetables. Use pmd_populate for that
2360                  */
2361                 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2362                 spin_unlock(&mm->page_table_lock);
2363                 anon_vma_unlock_write(vma->anon_vma);
2364                 goto out;
2365         }
2366
2367         /*
2368          * All pages are isolated and locked so anon_vma rmap
2369          * can't run anymore.
2370          */
2371         anon_vma_unlock_write(vma->anon_vma);
2372
2373         __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2374         pte_unmap(pte);
2375         __SetPageUptodate(new_page);
2376         pgtable = pmd_pgtable(_pmd);
2377
2378         _pmd = mk_huge_pmd(new_page, vma);
2379
2380         /*
2381          * spin_lock() below is not the equivalent of smp_wmb(), so
2382          * this is needed to avoid the copy_huge_page writes to become
2383          * visible after the set_pmd_at() write.
2384          */
2385         smp_wmb();
2386
2387         spin_lock(&mm->page_table_lock);
2388         BUG_ON(!pmd_none(*pmd));
2389         page_add_new_anon_rmap(new_page, vma, address);
2390         set_pmd_at(mm, address, pmd, _pmd);
2391         update_mmu_cache_pmd(vma, address, pmd);
2392         pgtable_trans_huge_deposit(mm, pgtable);
2393         spin_unlock(&mm->page_table_lock);
2394
2395         *hpage = NULL;
2396
2397         khugepaged_pages_collapsed++;
2398 out_up_write:
2399         up_write(&mm->mmap_sem);
2400         return;
2401
2402 out:
2403         mem_cgroup_uncharge_page(new_page);
2404         goto out_up_write;
2405 }
2406
2407 static int khugepaged_scan_pmd(struct mm_struct *mm,
2408                                struct vm_area_struct *vma,
2409                                unsigned long address,
2410                                struct page **hpage)
2411 {
2412         pmd_t *pmd;
2413         pte_t *pte, *_pte;
2414         int ret = 0, referenced = 0, none = 0;
2415         struct page *page;
2416         unsigned long _address;
2417         spinlock_t *ptl;
2418         int node = NUMA_NO_NODE;
2419
2420         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2421
2422         pmd = mm_find_pmd(mm, address);
2423         if (!pmd)
2424                 goto out;
2425         if (pmd_trans_huge(*pmd))
2426                 goto out;
2427
2428         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2429         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2430              _pte++, _address += PAGE_SIZE) {
2431                 pte_t pteval = *_pte;
2432                 if (pte_none(pteval)) {
2433                         if (++none <= khugepaged_max_ptes_none)
2434                                 continue;
2435                         else
2436                                 goto out_unmap;
2437                 }
2438                 if (!pte_present(pteval) || !pte_write(pteval))
2439                         goto out_unmap;
2440                 page = vm_normal_page(vma, _address, pteval);
2441                 if (unlikely(!page))
2442                         goto out_unmap;
2443                 /*
2444                  * Chose the node of the first page. This could
2445                  * be more sophisticated and look at more pages,
2446                  * but isn't for now.
2447                  */
2448                 if (node == NUMA_NO_NODE)
2449                         node = page_to_nid(page);
2450                 VM_BUG_ON(PageCompound(page));
2451                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2452                         goto out_unmap;
2453                 /* cannot use mapcount: can't collapse if there's a gup pin */
2454                 if (page_count(page) != 1)
2455                         goto out_unmap;
2456                 if (pte_young(pteval) || PageReferenced(page) ||
2457                     mmu_notifier_test_young(vma->vm_mm, address))
2458                         referenced = 1;
2459         }
2460         if (referenced)
2461                 ret = 1;
2462 out_unmap:
2463         pte_unmap_unlock(pte, ptl);
2464         if (ret)
2465                 /* collapse_huge_page will return with the mmap_sem released */
2466                 collapse_huge_page(mm, address, hpage, vma, node);
2467 out:
2468         return ret;
2469 }
2470
2471 static void collect_mm_slot(struct mm_slot *mm_slot)
2472 {
2473         struct mm_struct *mm = mm_slot->mm;
2474
2475         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2476
2477         if (khugepaged_test_exit(mm)) {
2478                 /* free mm_slot */
2479                 hash_del(&mm_slot->hash);
2480                 list_del(&mm_slot->mm_node);
2481
2482                 /*
2483                  * Not strictly needed because the mm exited already.
2484                  *
2485                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2486                  */
2487
2488                 /* khugepaged_mm_lock actually not necessary for the below */
2489                 free_mm_slot(mm_slot);
2490                 mmdrop(mm);
2491         }
2492 }
2493
2494 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2495                                             struct page **hpage)
2496         __releases(&khugepaged_mm_lock)
2497         __acquires(&khugepaged_mm_lock)
2498 {
2499         struct mm_slot *mm_slot;
2500         struct mm_struct *mm;
2501         struct vm_area_struct *vma;
2502         int progress = 0;
2503
2504         VM_BUG_ON(!pages);
2505         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2506
2507         if (khugepaged_scan.mm_slot)
2508                 mm_slot = khugepaged_scan.mm_slot;
2509         else {
2510                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2511                                      struct mm_slot, mm_node);
2512                 khugepaged_scan.address = 0;
2513                 khugepaged_scan.mm_slot = mm_slot;
2514         }
2515         spin_unlock(&khugepaged_mm_lock);
2516
2517         mm = mm_slot->mm;
2518         down_read(&mm->mmap_sem);
2519         if (unlikely(khugepaged_test_exit(mm)))
2520                 vma = NULL;
2521         else
2522                 vma = find_vma(mm, khugepaged_scan.address);
2523
2524         progress++;
2525         for (; vma; vma = vma->vm_next) {
2526                 unsigned long hstart, hend;
2527
2528                 cond_resched();
2529                 if (unlikely(khugepaged_test_exit(mm))) {
2530                         progress++;
2531                         break;
2532                 }
2533                 if (!hugepage_vma_check(vma)) {
2534 skip:
2535                         progress++;
2536                         continue;
2537                 }
2538                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2539                 hend = vma->vm_end & HPAGE_PMD_MASK;
2540                 if (hstart >= hend)
2541                         goto skip;
2542                 if (khugepaged_scan.address > hend)
2543                         goto skip;
2544                 if (khugepaged_scan.address < hstart)
2545                         khugepaged_scan.address = hstart;
2546                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2547
2548                 while (khugepaged_scan.address < hend) {
2549                         int ret;
2550                         cond_resched();
2551                         if (unlikely(khugepaged_test_exit(mm)))
2552                                 goto breakouterloop;
2553
2554                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2555                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2556                                   hend);
2557                         ret = khugepaged_scan_pmd(mm, vma,
2558                                                   khugepaged_scan.address,
2559                                                   hpage);
2560                         /* move to next address */
2561                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2562                         progress += HPAGE_PMD_NR;
2563                         if (ret)
2564                                 /* we released mmap_sem so break loop */
2565                                 goto breakouterloop_mmap_sem;
2566                         if (progress >= pages)
2567                                 goto breakouterloop;
2568                 }
2569         }
2570 breakouterloop:
2571         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2572 breakouterloop_mmap_sem:
2573
2574         spin_lock(&khugepaged_mm_lock);
2575         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2576         /*
2577          * Release the current mm_slot if this mm is about to die, or
2578          * if we scanned all vmas of this mm.
2579          */
2580         if (khugepaged_test_exit(mm) || !vma) {
2581                 /*
2582                  * Make sure that if mm_users is reaching zero while
2583                  * khugepaged runs here, khugepaged_exit will find
2584                  * mm_slot not pointing to the exiting mm.
2585                  */
2586                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2587                         khugepaged_scan.mm_slot = list_entry(
2588                                 mm_slot->mm_node.next,
2589                                 struct mm_slot, mm_node);
2590                         khugepaged_scan.address = 0;
2591                 } else {
2592                         khugepaged_scan.mm_slot = NULL;
2593                         khugepaged_full_scans++;
2594                 }
2595
2596                 collect_mm_slot(mm_slot);
2597         }
2598
2599         return progress;
2600 }
2601
2602 static int khugepaged_has_work(void)
2603 {
2604         return !list_empty(&khugepaged_scan.mm_head) &&
2605                 khugepaged_enabled();
2606 }
2607
2608 static int khugepaged_wait_event(void)
2609 {
2610         return !list_empty(&khugepaged_scan.mm_head) ||
2611                 kthread_should_stop();
2612 }
2613
2614 static void khugepaged_do_scan(void)
2615 {
2616         struct page *hpage = NULL;
2617         unsigned int progress = 0, pass_through_head = 0;
2618         unsigned int pages = khugepaged_pages_to_scan;
2619         bool wait = true;
2620
2621         barrier(); /* write khugepaged_pages_to_scan to local stack */
2622
2623         while (progress < pages) {
2624                 if (!khugepaged_prealloc_page(&hpage, &wait))
2625                         break;
2626
2627                 cond_resched();
2628
2629                 if (unlikely(kthread_should_stop() || freezing(current)))
2630                         break;
2631
2632                 spin_lock(&khugepaged_mm_lock);
2633                 if (!khugepaged_scan.mm_slot)
2634                         pass_through_head++;
2635                 if (khugepaged_has_work() &&
2636                     pass_through_head < 2)
2637                         progress += khugepaged_scan_mm_slot(pages - progress,
2638                                                             &hpage);
2639                 else
2640                         progress = pages;
2641                 spin_unlock(&khugepaged_mm_lock);
2642         }
2643
2644         if (!IS_ERR_OR_NULL(hpage))
2645                 put_page(hpage);
2646 }
2647
2648 static void khugepaged_wait_work(void)
2649 {
2650         try_to_freeze();
2651
2652         if (khugepaged_has_work()) {
2653                 if (!khugepaged_scan_sleep_millisecs)
2654                         return;
2655
2656                 wait_event_freezable_timeout(khugepaged_wait,
2657                                              kthread_should_stop(),
2658                         msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2659                 return;
2660         }
2661
2662         if (khugepaged_enabled())
2663                 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2664 }
2665
2666 static int khugepaged(void *none)
2667 {
2668         struct mm_slot *mm_slot;
2669
2670         set_freezable();
2671         set_user_nice(current, 19);
2672
2673         while (!kthread_should_stop()) {
2674                 khugepaged_do_scan();
2675                 khugepaged_wait_work();
2676         }
2677
2678         spin_lock(&khugepaged_mm_lock);
2679         mm_slot = khugepaged_scan.mm_slot;
2680         khugepaged_scan.mm_slot = NULL;
2681         if (mm_slot)
2682                 collect_mm_slot(mm_slot);
2683         spin_unlock(&khugepaged_mm_lock);
2684         return 0;
2685 }
2686
2687 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2688                 unsigned long haddr, pmd_t *pmd)
2689 {
2690         struct mm_struct *mm = vma->vm_mm;
2691         pgtable_t pgtable;
2692         pmd_t _pmd;
2693         int i;
2694
2695         pmdp_clear_flush(vma, haddr, pmd);
2696         /* leave pmd empty until pte is filled */
2697
2698         pgtable = pgtable_trans_huge_withdraw(mm);
2699         pmd_populate(mm, &_pmd, pgtable);
2700
2701         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2702                 pte_t *pte, entry;
2703                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2704                 entry = pte_mkspecial(entry);
2705                 pte = pte_offset_map(&_pmd, haddr);
2706                 VM_BUG_ON(!pte_none(*pte));
2707                 set_pte_at(mm, haddr, pte, entry);
2708                 pte_unmap(pte);
2709         }
2710         smp_wmb(); /* make pte visible before pmd */
2711         pmd_populate(mm, pmd, pgtable);
2712         put_huge_zero_page();
2713 }
2714
2715 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2716                 pmd_t *pmd)
2717 {
2718         struct page *page;
2719         struct mm_struct *mm = vma->vm_mm;
2720         unsigned long haddr = address & HPAGE_PMD_MASK;
2721         unsigned long mmun_start;       /* For mmu_notifiers */
2722         unsigned long mmun_end;         /* For mmu_notifiers */
2723
2724         BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2725
2726         mmun_start = haddr;
2727         mmun_end   = haddr + HPAGE_PMD_SIZE;
2728 again:
2729         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2730         spin_lock(&mm->page_table_lock);
2731         if (unlikely(!pmd_trans_huge(*pmd))) {
2732                 spin_unlock(&mm->page_table_lock);
2733                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2734                 return;
2735         }
2736         if (is_huge_zero_pmd(*pmd)) {
2737                 __split_huge_zero_page_pmd(vma, haddr, pmd);
2738                 spin_unlock(&mm->page_table_lock);
2739                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2740                 return;
2741         }
2742         page = pmd_page(*pmd);
2743         VM_BUG_ON(!page_count(page));
2744         get_page(page);
2745         spin_unlock(&mm->page_table_lock);
2746         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2747
2748         split_huge_page(page);
2749
2750         put_page(page);
2751
2752         /*
2753          * We don't always have down_write of mmap_sem here: a racing
2754          * do_huge_pmd_wp_page() might have copied-on-write to another
2755          * huge page before our split_huge_page() got the anon_vma lock.
2756          */
2757         if (unlikely(pmd_trans_huge(*pmd)))
2758                 goto again;
2759 }
2760
2761 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2762                 pmd_t *pmd)
2763 {
2764         struct vm_area_struct *vma;
2765
2766         vma = find_vma(mm, address);
2767         BUG_ON(vma == NULL);
2768         split_huge_page_pmd(vma, address, pmd);
2769 }
2770
2771 static void split_huge_page_address(struct mm_struct *mm,
2772                                     unsigned long address)
2773 {
2774         pmd_t *pmd;
2775
2776         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2777
2778         pmd = mm_find_pmd(mm, address);
2779         if (!pmd)
2780                 return;
2781         /*
2782          * Caller holds the mmap_sem write mode, so a huge pmd cannot
2783          * materialize from under us.
2784          */
2785         split_huge_page_pmd_mm(mm, address, pmd);
2786 }
2787
2788 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2789                              unsigned long start,
2790                              unsigned long end,
2791                              long adjust_next)
2792 {
2793         /*
2794          * If the new start address isn't hpage aligned and it could
2795          * previously contain an hugepage: check if we need to split
2796          * an huge pmd.
2797          */
2798         if (start & ~HPAGE_PMD_MASK &&
2799             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2800             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2801                 split_huge_page_address(vma->vm_mm, start);
2802
2803         /*
2804          * If the new end address isn't hpage aligned and it could
2805          * previously contain an hugepage: check if we need to split
2806          * an huge pmd.
2807          */
2808         if (end & ~HPAGE_PMD_MASK &&
2809             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2810             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2811                 split_huge_page_address(vma->vm_mm, end);
2812
2813         /*
2814          * If we're also updating the vma->vm_next->vm_start, if the new
2815          * vm_next->vm_start isn't page aligned and it could previously
2816          * contain an hugepage: check if we need to split an huge pmd.
2817          */
2818         if (adjust_next > 0) {
2819                 struct vm_area_struct *next = vma->vm_next;
2820                 unsigned long nstart = next->vm_start;
2821                 nstart += adjust_next << PAGE_SHIFT;
2822                 if (nstart & ~HPAGE_PMD_MASK &&
2823                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2824                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2825                         split_huge_page_address(next->vm_mm, nstart);
2826         }
2827 }