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1 /*
2  *  Copyright (C) 2009  Red Hat, Inc.
3  *
4  *  This work is licensed under the terms of the GNU GPL, version 2. See
5  *  the COPYING file in the top-level directory.
6  */
7
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10 #include <linux/mm.h>
11 #include <linux/sched.h>
12 #include <linux/highmem.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mmu_notifier.h>
15 #include <linux/rmap.h>
16 #include <linux/swap.h>
17 #include <linux/shrinker.h>
18 #include <linux/mm_inline.h>
19 #include <linux/kthread.h>
20 #include <linux/khugepaged.h>
21 #include <linux/freezer.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/migrate.h>
25 #include <linux/hashtable.h>
26
27 #include <asm/tlb.h>
28 #include <asm/pgalloc.h>
29 #include "internal.h"
30
31 /*
32  * By default transparent hugepage support is disabled in order that avoid
33  * to risk increase the memory footprint of applications without a guaranteed
34  * benefit. When transparent hugepage support is enabled, is for all mappings,
35  * and khugepaged scans all mappings.
36  * Defrag is invoked by khugepaged hugepage allocations and by page faults
37  * for all hugepage allocations.
38  */
39 unsigned long transparent_hugepage_flags __read_mostly =
40 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
41         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
42 #endif
43 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
44         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
45 #endif
46         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
47         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
48         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
49
50 /* default scan 8*512 pte (or vmas) every 30 second */
51 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
52 static unsigned int khugepaged_pages_collapsed;
53 static unsigned int khugepaged_full_scans;
54 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
55 /* during fragmentation poll the hugepage allocator once every minute */
56 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
57 static struct task_struct *khugepaged_thread __read_mostly;
58 static DEFINE_MUTEX(khugepaged_mutex);
59 static DEFINE_SPINLOCK(khugepaged_mm_lock);
60 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
61 /*
62  * default collapse hugepages if there is at least one pte mapped like
63  * it would have happened if the vma was large enough during page
64  * fault.
65  */
66 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
67
68 static int khugepaged(void *none);
69 static int khugepaged_slab_init(void);
70
71 #define MM_SLOTS_HASH_BITS 10
72 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
73
74 static struct kmem_cache *mm_slot_cache __read_mostly;
75
76 /**
77  * struct mm_slot - hash lookup from mm to mm_slot
78  * @hash: hash collision list
79  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
80  * @mm: the mm that this information is valid for
81  */
82 struct mm_slot {
83         struct hlist_node hash;
84         struct list_head mm_node;
85         struct mm_struct *mm;
86 };
87
88 /**
89  * struct khugepaged_scan - cursor for scanning
90  * @mm_head: the head of the mm list to scan
91  * @mm_slot: the current mm_slot we are scanning
92  * @address: the next address inside that to be scanned
93  *
94  * There is only the one khugepaged_scan instance of this cursor structure.
95  */
96 struct khugepaged_scan {
97         struct list_head mm_head;
98         struct mm_slot *mm_slot;
99         unsigned long address;
100 };
101 static struct khugepaged_scan khugepaged_scan = {
102         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
103 };
104
105
106 static int set_recommended_min_free_kbytes(void)
107 {
108         struct zone *zone;
109         int nr_zones = 0;
110         unsigned long recommended_min;
111
112         if (!khugepaged_enabled())
113                 return 0;
114
115         for_each_populated_zone(zone)
116                 nr_zones++;
117
118         /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
119         recommended_min = pageblock_nr_pages * nr_zones * 2;
120
121         /*
122          * Make sure that on average at least two pageblocks are almost free
123          * of another type, one for a migratetype to fall back to and a
124          * second to avoid subsequent fallbacks of other types There are 3
125          * MIGRATE_TYPES we care about.
126          */
127         recommended_min += pageblock_nr_pages * nr_zones *
128                            MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
129
130         /* don't ever allow to reserve more than 5% of the lowmem */
131         recommended_min = min(recommended_min,
132                               (unsigned long) nr_free_buffer_pages() / 20);
133         recommended_min <<= (PAGE_SHIFT-10);
134
135         if (recommended_min > min_free_kbytes) {
136                 if (user_min_free_kbytes >= 0)
137                         pr_info("raising min_free_kbytes from %d to %lu "
138                                 "to help transparent hugepage allocations\n",
139                                 min_free_kbytes, recommended_min);
140
141                 min_free_kbytes = recommended_min;
142         }
143         setup_per_zone_wmarks();
144         return 0;
145 }
146 late_initcall(set_recommended_min_free_kbytes);
147
148 static int start_khugepaged(void)
149 {
150         int err = 0;
151         if (khugepaged_enabled()) {
152                 if (!khugepaged_thread)
153                         khugepaged_thread = kthread_run(khugepaged, NULL,
154                                                         "khugepaged");
155                 if (unlikely(IS_ERR(khugepaged_thread))) {
156                         pr_err("khugepaged: kthread_run(khugepaged) failed\n");
157                         err = PTR_ERR(khugepaged_thread);
158                         khugepaged_thread = NULL;
159                 }
160
161                 if (!list_empty(&khugepaged_scan.mm_head))
162                         wake_up_interruptible(&khugepaged_wait);
163
164                 set_recommended_min_free_kbytes();
165         } else if (khugepaged_thread) {
166                 kthread_stop(khugepaged_thread);
167                 khugepaged_thread = NULL;
168         }
169
170         return err;
171 }
172
173 static atomic_t huge_zero_refcount;
174 struct page *huge_zero_page __read_mostly;
175
176 static inline bool is_huge_zero_pmd(pmd_t pmd)
177 {
178         return is_huge_zero_page(pmd_page(pmd));
179 }
180
181 static struct page *get_huge_zero_page(void)
182 {
183         struct page *zero_page;
184 retry:
185         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
186                 return ACCESS_ONCE(huge_zero_page);
187
188         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
189                         HPAGE_PMD_ORDER);
190         if (!zero_page) {
191                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
192                 return NULL;
193         }
194         count_vm_event(THP_ZERO_PAGE_ALLOC);
195         preempt_disable();
196         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
197                 preempt_enable();
198                 __free_pages(zero_page, compound_order(zero_page));
199                 goto retry;
200         }
201
202         /* We take additional reference here. It will be put back by shrinker */
203         atomic_set(&huge_zero_refcount, 2);
204         preempt_enable();
205         return ACCESS_ONCE(huge_zero_page);
206 }
207
208 static void put_huge_zero_page(void)
209 {
210         /*
211          * Counter should never go to zero here. Only shrinker can put
212          * last reference.
213          */
214         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
215 }
216
217 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
218                                         struct shrink_control *sc)
219 {
220         /* we can free zero page only if last reference remains */
221         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
222 }
223
224 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
225                                        struct shrink_control *sc)
226 {
227         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
228                 struct page *zero_page = xchg(&huge_zero_page, NULL);
229                 BUG_ON(zero_page == NULL);
230                 __free_pages(zero_page, compound_order(zero_page));
231                 return HPAGE_PMD_NR;
232         }
233
234         return 0;
235 }
236
237 static struct shrinker huge_zero_page_shrinker = {
238         .count_objects = shrink_huge_zero_page_count,
239         .scan_objects = shrink_huge_zero_page_scan,
240         .seeks = DEFAULT_SEEKS,
241 };
242
243 #ifdef CONFIG_SYSFS
244
245 static ssize_t double_flag_show(struct kobject *kobj,
246                                 struct kobj_attribute *attr, char *buf,
247                                 enum transparent_hugepage_flag enabled,
248                                 enum transparent_hugepage_flag req_madv)
249 {
250         if (test_bit(enabled, &transparent_hugepage_flags)) {
251                 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
252                 return sprintf(buf, "[always] madvise never\n");
253         } else if (test_bit(req_madv, &transparent_hugepage_flags))
254                 return sprintf(buf, "always [madvise] never\n");
255         else
256                 return sprintf(buf, "always madvise [never]\n");
257 }
258 static ssize_t double_flag_store(struct kobject *kobj,
259                                  struct kobj_attribute *attr,
260                                  const char *buf, size_t count,
261                                  enum transparent_hugepage_flag enabled,
262                                  enum transparent_hugepage_flag req_madv)
263 {
264         if (!memcmp("always", buf,
265                     min(sizeof("always")-1, count))) {
266                 set_bit(enabled, &transparent_hugepage_flags);
267                 clear_bit(req_madv, &transparent_hugepage_flags);
268         } else if (!memcmp("madvise", buf,
269                            min(sizeof("madvise")-1, count))) {
270                 clear_bit(enabled, &transparent_hugepage_flags);
271                 set_bit(req_madv, &transparent_hugepage_flags);
272         } else if (!memcmp("never", buf,
273                            min(sizeof("never")-1, count))) {
274                 clear_bit(enabled, &transparent_hugepage_flags);
275                 clear_bit(req_madv, &transparent_hugepage_flags);
276         } else
277                 return -EINVAL;
278
279         return count;
280 }
281
282 static ssize_t enabled_show(struct kobject *kobj,
283                             struct kobj_attribute *attr, char *buf)
284 {
285         return double_flag_show(kobj, attr, buf,
286                                 TRANSPARENT_HUGEPAGE_FLAG,
287                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
288 }
289 static ssize_t enabled_store(struct kobject *kobj,
290                              struct kobj_attribute *attr,
291                              const char *buf, size_t count)
292 {
293         ssize_t ret;
294
295         ret = double_flag_store(kobj, attr, buf, count,
296                                 TRANSPARENT_HUGEPAGE_FLAG,
297                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
298
299         if (ret > 0) {
300                 int err;
301
302                 mutex_lock(&khugepaged_mutex);
303                 err = start_khugepaged();
304                 mutex_unlock(&khugepaged_mutex);
305
306                 if (err)
307                         ret = err;
308         }
309
310         return ret;
311 }
312 static struct kobj_attribute enabled_attr =
313         __ATTR(enabled, 0644, enabled_show, enabled_store);
314
315 static ssize_t single_flag_show(struct kobject *kobj,
316                                 struct kobj_attribute *attr, char *buf,
317                                 enum transparent_hugepage_flag flag)
318 {
319         return sprintf(buf, "%d\n",
320                        !!test_bit(flag, &transparent_hugepage_flags));
321 }
322
323 static ssize_t single_flag_store(struct kobject *kobj,
324                                  struct kobj_attribute *attr,
325                                  const char *buf, size_t count,
326                                  enum transparent_hugepage_flag flag)
327 {
328         unsigned long value;
329         int ret;
330
331         ret = kstrtoul(buf, 10, &value);
332         if (ret < 0)
333                 return ret;
334         if (value > 1)
335                 return -EINVAL;
336
337         if (value)
338                 set_bit(flag, &transparent_hugepage_flags);
339         else
340                 clear_bit(flag, &transparent_hugepage_flags);
341
342         return count;
343 }
344
345 /*
346  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
347  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
348  * memory just to allocate one more hugepage.
349  */
350 static ssize_t defrag_show(struct kobject *kobj,
351                            struct kobj_attribute *attr, char *buf)
352 {
353         return double_flag_show(kobj, attr, buf,
354                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
355                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
356 }
357 static ssize_t defrag_store(struct kobject *kobj,
358                             struct kobj_attribute *attr,
359                             const char *buf, size_t count)
360 {
361         return double_flag_store(kobj, attr, buf, count,
362                                  TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
363                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
364 }
365 static struct kobj_attribute defrag_attr =
366         __ATTR(defrag, 0644, defrag_show, defrag_store);
367
368 static ssize_t use_zero_page_show(struct kobject *kobj,
369                 struct kobj_attribute *attr, char *buf)
370 {
371         return single_flag_show(kobj, attr, buf,
372                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
373 }
374 static ssize_t use_zero_page_store(struct kobject *kobj,
375                 struct kobj_attribute *attr, const char *buf, size_t count)
376 {
377         return single_flag_store(kobj, attr, buf, count,
378                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
379 }
380 static struct kobj_attribute use_zero_page_attr =
381         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
382 #ifdef CONFIG_DEBUG_VM
383 static ssize_t debug_cow_show(struct kobject *kobj,
384                                 struct kobj_attribute *attr, char *buf)
385 {
386         return single_flag_show(kobj, attr, buf,
387                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
388 }
389 static ssize_t debug_cow_store(struct kobject *kobj,
390                                struct kobj_attribute *attr,
391                                const char *buf, size_t count)
392 {
393         return single_flag_store(kobj, attr, buf, count,
394                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
395 }
396 static struct kobj_attribute debug_cow_attr =
397         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
398 #endif /* CONFIG_DEBUG_VM */
399
400 static struct attribute *hugepage_attr[] = {
401         &enabled_attr.attr,
402         &defrag_attr.attr,
403         &use_zero_page_attr.attr,
404 #ifdef CONFIG_DEBUG_VM
405         &debug_cow_attr.attr,
406 #endif
407         NULL,
408 };
409
410 static struct attribute_group hugepage_attr_group = {
411         .attrs = hugepage_attr,
412 };
413
414 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
415                                          struct kobj_attribute *attr,
416                                          char *buf)
417 {
418         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
419 }
420
421 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
422                                           struct kobj_attribute *attr,
423                                           const char *buf, size_t count)
424 {
425         unsigned long msecs;
426         int err;
427
428         err = kstrtoul(buf, 10, &msecs);
429         if (err || msecs > UINT_MAX)
430                 return -EINVAL;
431
432         khugepaged_scan_sleep_millisecs = msecs;
433         wake_up_interruptible(&khugepaged_wait);
434
435         return count;
436 }
437 static struct kobj_attribute scan_sleep_millisecs_attr =
438         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
439                scan_sleep_millisecs_store);
440
441 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
442                                           struct kobj_attribute *attr,
443                                           char *buf)
444 {
445         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
446 }
447
448 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
449                                            struct kobj_attribute *attr,
450                                            const char *buf, size_t count)
451 {
452         unsigned long msecs;
453         int err;
454
455         err = kstrtoul(buf, 10, &msecs);
456         if (err || msecs > UINT_MAX)
457                 return -EINVAL;
458
459         khugepaged_alloc_sleep_millisecs = msecs;
460         wake_up_interruptible(&khugepaged_wait);
461
462         return count;
463 }
464 static struct kobj_attribute alloc_sleep_millisecs_attr =
465         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
466                alloc_sleep_millisecs_store);
467
468 static ssize_t pages_to_scan_show(struct kobject *kobj,
469                                   struct kobj_attribute *attr,
470                                   char *buf)
471 {
472         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
473 }
474 static ssize_t pages_to_scan_store(struct kobject *kobj,
475                                    struct kobj_attribute *attr,
476                                    const char *buf, size_t count)
477 {
478         int err;
479         unsigned long pages;
480
481         err = kstrtoul(buf, 10, &pages);
482         if (err || !pages || pages > UINT_MAX)
483                 return -EINVAL;
484
485         khugepaged_pages_to_scan = pages;
486
487         return count;
488 }
489 static struct kobj_attribute pages_to_scan_attr =
490         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
491                pages_to_scan_store);
492
493 static ssize_t pages_collapsed_show(struct kobject *kobj,
494                                     struct kobj_attribute *attr,
495                                     char *buf)
496 {
497         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
498 }
499 static struct kobj_attribute pages_collapsed_attr =
500         __ATTR_RO(pages_collapsed);
501
502 static ssize_t full_scans_show(struct kobject *kobj,
503                                struct kobj_attribute *attr,
504                                char *buf)
505 {
506         return sprintf(buf, "%u\n", khugepaged_full_scans);
507 }
508 static struct kobj_attribute full_scans_attr =
509         __ATTR_RO(full_scans);
510
511 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
512                                       struct kobj_attribute *attr, char *buf)
513 {
514         return single_flag_show(kobj, attr, buf,
515                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
516 }
517 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
518                                        struct kobj_attribute *attr,
519                                        const char *buf, size_t count)
520 {
521         return single_flag_store(kobj, attr, buf, count,
522                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
523 }
524 static struct kobj_attribute khugepaged_defrag_attr =
525         __ATTR(defrag, 0644, khugepaged_defrag_show,
526                khugepaged_defrag_store);
527
528 /*
529  * max_ptes_none controls if khugepaged should collapse hugepages over
530  * any unmapped ptes in turn potentially increasing the memory
531  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
532  * reduce the available free memory in the system as it
533  * runs. Increasing max_ptes_none will instead potentially reduce the
534  * free memory in the system during the khugepaged scan.
535  */
536 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
537                                              struct kobj_attribute *attr,
538                                              char *buf)
539 {
540         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
541 }
542 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
543                                               struct kobj_attribute *attr,
544                                               const char *buf, size_t count)
545 {
546         int err;
547         unsigned long max_ptes_none;
548
549         err = kstrtoul(buf, 10, &max_ptes_none);
550         if (err || max_ptes_none > HPAGE_PMD_NR-1)
551                 return -EINVAL;
552
553         khugepaged_max_ptes_none = max_ptes_none;
554
555         return count;
556 }
557 static struct kobj_attribute khugepaged_max_ptes_none_attr =
558         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
559                khugepaged_max_ptes_none_store);
560
561 static struct attribute *khugepaged_attr[] = {
562         &khugepaged_defrag_attr.attr,
563         &khugepaged_max_ptes_none_attr.attr,
564         &pages_to_scan_attr.attr,
565         &pages_collapsed_attr.attr,
566         &full_scans_attr.attr,
567         &scan_sleep_millisecs_attr.attr,
568         &alloc_sleep_millisecs_attr.attr,
569         NULL,
570 };
571
572 static struct attribute_group khugepaged_attr_group = {
573         .attrs = khugepaged_attr,
574         .name = "khugepaged",
575 };
576
577 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
578 {
579         int err;
580
581         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
582         if (unlikely(!*hugepage_kobj)) {
583                 pr_err("failed to create transparent hugepage kobject\n");
584                 return -ENOMEM;
585         }
586
587         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
588         if (err) {
589                 pr_err("failed to register transparent hugepage group\n");
590                 goto delete_obj;
591         }
592
593         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
594         if (err) {
595                 pr_err("failed to register transparent hugepage group\n");
596                 goto remove_hp_group;
597         }
598
599         return 0;
600
601 remove_hp_group:
602         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
603 delete_obj:
604         kobject_put(*hugepage_kobj);
605         return err;
606 }
607
608 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
609 {
610         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
611         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
612         kobject_put(hugepage_kobj);
613 }
614 #else
615 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
616 {
617         return 0;
618 }
619
620 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
621 {
622 }
623 #endif /* CONFIG_SYSFS */
624
625 static int __init hugepage_init(void)
626 {
627         int err;
628         struct kobject *hugepage_kobj;
629
630         if (!has_transparent_hugepage()) {
631                 transparent_hugepage_flags = 0;
632                 return -EINVAL;
633         }
634
635         err = hugepage_init_sysfs(&hugepage_kobj);
636         if (err)
637                 return err;
638
639         err = khugepaged_slab_init();
640         if (err)
641                 goto out;
642
643         register_shrinker(&huge_zero_page_shrinker);
644
645         /*
646          * By default disable transparent hugepages on smaller systems,
647          * where the extra memory used could hurt more than TLB overhead
648          * is likely to save.  The admin can still enable it through /sys.
649          */
650         if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
651                 transparent_hugepage_flags = 0;
652
653         start_khugepaged();
654
655         return 0;
656 out:
657         hugepage_exit_sysfs(hugepage_kobj);
658         return err;
659 }
660 subsys_initcall(hugepage_init);
661
662 static int __init setup_transparent_hugepage(char *str)
663 {
664         int ret = 0;
665         if (!str)
666                 goto out;
667         if (!strcmp(str, "always")) {
668                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
669                         &transparent_hugepage_flags);
670                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
671                           &transparent_hugepage_flags);
672                 ret = 1;
673         } else if (!strcmp(str, "madvise")) {
674                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
675                           &transparent_hugepage_flags);
676                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
677                         &transparent_hugepage_flags);
678                 ret = 1;
679         } else if (!strcmp(str, "never")) {
680                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
681                           &transparent_hugepage_flags);
682                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
683                           &transparent_hugepage_flags);
684                 ret = 1;
685         }
686 out:
687         if (!ret)
688                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
689         return ret;
690 }
691 __setup("transparent_hugepage=", setup_transparent_hugepage);
692
693 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
694 {
695         if (likely(vma->vm_flags & VM_WRITE))
696                 pmd = pmd_mkwrite(pmd);
697         return pmd;
698 }
699
700 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
701 {
702         pmd_t entry;
703         entry = mk_pmd(page, prot);
704         entry = pmd_mkhuge(entry);
705         return entry;
706 }
707
708 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
709                                         struct vm_area_struct *vma,
710                                         unsigned long haddr, pmd_t *pmd,
711                                         struct page *page)
712 {
713         struct mem_cgroup *memcg;
714         pgtable_t pgtable;
715         spinlock_t *ptl;
716
717         VM_BUG_ON_PAGE(!PageCompound(page), page);
718
719         if (mem_cgroup_try_charge(page, mm, GFP_TRANSHUGE, &memcg))
720                 return VM_FAULT_OOM;
721
722         pgtable = pte_alloc_one(mm, haddr);
723         if (unlikely(!pgtable)) {
724                 mem_cgroup_cancel_charge(page, memcg);
725                 return VM_FAULT_OOM;
726         }
727
728         clear_huge_page(page, haddr, HPAGE_PMD_NR);
729         /*
730          * The memory barrier inside __SetPageUptodate makes sure that
731          * clear_huge_page writes become visible before the set_pmd_at()
732          * write.
733          */
734         __SetPageUptodate(page);
735
736         ptl = pmd_lock(mm, pmd);
737         if (unlikely(!pmd_none(*pmd))) {
738                 spin_unlock(ptl);
739                 mem_cgroup_cancel_charge(page, memcg);
740                 put_page(page);
741                 pte_free(mm, pgtable);
742         } else {
743                 pmd_t entry;
744                 entry = mk_huge_pmd(page, vma->vm_page_prot);
745                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
746                 page_add_new_anon_rmap(page, vma, haddr);
747                 mem_cgroup_commit_charge(page, memcg, false);
748                 lru_cache_add_active_or_unevictable(page, vma);
749                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
750                 set_pmd_at(mm, haddr, pmd, entry);
751                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
752                 atomic_long_inc(&mm->nr_ptes);
753                 spin_unlock(ptl);
754         }
755
756         return 0;
757 }
758
759 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
760 {
761         return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
762 }
763
764 /* Caller must hold page table lock. */
765 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
766                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
767                 struct page *zero_page)
768 {
769         pmd_t entry;
770         if (!pmd_none(*pmd))
771                 return false;
772         entry = mk_pmd(zero_page, vma->vm_page_prot);
773         entry = pmd_mkhuge(entry);
774         pgtable_trans_huge_deposit(mm, pmd, pgtable);
775         set_pmd_at(mm, haddr, pmd, entry);
776         atomic_long_inc(&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         gfp_t gfp;
785         struct page *page;
786         unsigned long haddr = address & HPAGE_PMD_MASK;
787
788         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
789                 return VM_FAULT_FALLBACK;
790         if (unlikely(anon_vma_prepare(vma)))
791                 return VM_FAULT_OOM;
792         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
793                 return VM_FAULT_OOM;
794         if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
795                         transparent_hugepage_use_zero_page()) {
796                 spinlock_t *ptl;
797                 pgtable_t pgtable;
798                 struct page *zero_page;
799                 bool set;
800                 pgtable = pte_alloc_one(mm, haddr);
801                 if (unlikely(!pgtable))
802                         return VM_FAULT_OOM;
803                 zero_page = get_huge_zero_page();
804                 if (unlikely(!zero_page)) {
805                         pte_free(mm, pgtable);
806                         count_vm_event(THP_FAULT_FALLBACK);
807                         return VM_FAULT_FALLBACK;
808                 }
809                 ptl = pmd_lock(mm, pmd);
810                 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
811                                 zero_page);
812                 spin_unlock(ptl);
813                 if (!set) {
814                         pte_free(mm, pgtable);
815                         put_huge_zero_page();
816                 }
817                 return 0;
818         }
819         gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
820         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
821         if (unlikely(!page)) {
822                 count_vm_event(THP_FAULT_FALLBACK);
823                 return VM_FAULT_FALLBACK;
824         }
825         if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) {
826                 put_page(page);
827                 count_vm_event(THP_FAULT_FALLBACK);
828                 return VM_FAULT_FALLBACK;
829         }
830
831         count_vm_event(THP_FAULT_ALLOC);
832         return 0;
833 }
834
835 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
836                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
837                   struct vm_area_struct *vma)
838 {
839         spinlock_t *dst_ptl, *src_ptl;
840         struct page *src_page;
841         pmd_t pmd;
842         pgtable_t pgtable;
843         int ret;
844
845         ret = -ENOMEM;
846         pgtable = pte_alloc_one(dst_mm, addr);
847         if (unlikely(!pgtable))
848                 goto out;
849
850         dst_ptl = pmd_lock(dst_mm, dst_pmd);
851         src_ptl = pmd_lockptr(src_mm, src_pmd);
852         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
853
854         ret = -EAGAIN;
855         pmd = *src_pmd;
856         if (unlikely(!pmd_trans_huge(pmd))) {
857                 pte_free(dst_mm, pgtable);
858                 goto out_unlock;
859         }
860         /*
861          * When page table lock is held, the huge zero pmd should not be
862          * under splitting since we don't split the page itself, only pmd to
863          * a page table.
864          */
865         if (is_huge_zero_pmd(pmd)) {
866                 struct page *zero_page;
867                 bool set;
868                 /*
869                  * get_huge_zero_page() will never allocate a new page here,
870                  * since we already have a zero page to copy. It just takes a
871                  * reference.
872                  */
873                 zero_page = get_huge_zero_page();
874                 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
875                                 zero_page);
876                 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
877                 ret = 0;
878                 goto out_unlock;
879         }
880
881         if (unlikely(pmd_trans_splitting(pmd))) {
882                 /* split huge page running from under us */
883                 spin_unlock(src_ptl);
884                 spin_unlock(dst_ptl);
885                 pte_free(dst_mm, pgtable);
886
887                 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
888                 goto out;
889         }
890         src_page = pmd_page(pmd);
891         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
892         get_page(src_page);
893         page_dup_rmap(src_page);
894         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
895
896         pmdp_set_wrprotect(src_mm, addr, src_pmd);
897         pmd = pmd_mkold(pmd_wrprotect(pmd));
898         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
899         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
900         atomic_long_inc(&dst_mm->nr_ptes);
901
902         ret = 0;
903 out_unlock:
904         spin_unlock(src_ptl);
905         spin_unlock(dst_ptl);
906 out:
907         return ret;
908 }
909
910 void huge_pmd_set_accessed(struct mm_struct *mm,
911                            struct vm_area_struct *vma,
912                            unsigned long address,
913                            pmd_t *pmd, pmd_t orig_pmd,
914                            int dirty)
915 {
916         spinlock_t *ptl;
917         pmd_t entry;
918         unsigned long haddr;
919
920         ptl = pmd_lock(mm, pmd);
921         if (unlikely(!pmd_same(*pmd, orig_pmd)))
922                 goto unlock;
923
924         entry = pmd_mkyoung(orig_pmd);
925         haddr = address & HPAGE_PMD_MASK;
926         if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
927                 update_mmu_cache_pmd(vma, address, pmd);
928
929 unlock:
930         spin_unlock(ptl);
931 }
932
933 /*
934  * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages
935  * during copy_user_huge_page()'s copy_page_rep(): in the case when
936  * the source page gets split and a tail freed before copy completes.
937  * Called under pmd_lock of checked pmd, so safe from splitting itself.
938  */
939 static void get_user_huge_page(struct page *page)
940 {
941         if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
942                 struct page *endpage = page + HPAGE_PMD_NR;
943
944                 atomic_add(HPAGE_PMD_NR, &page->_count);
945                 while (++page < endpage)
946                         get_huge_page_tail(page);
947         } else {
948                 get_page(page);
949         }
950 }
951
952 static void put_user_huge_page(struct page *page)
953 {
954         if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
955                 struct page *endpage = page + HPAGE_PMD_NR;
956
957                 while (page < endpage)
958                         put_page(page++);
959         } else {
960                 put_page(page);
961         }
962 }
963
964 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
965                                         struct vm_area_struct *vma,
966                                         unsigned long address,
967                                         pmd_t *pmd, pmd_t orig_pmd,
968                                         struct page *page,
969                                         unsigned long haddr)
970 {
971         struct mem_cgroup *memcg;
972         spinlock_t *ptl;
973         pgtable_t pgtable;
974         pmd_t _pmd;
975         int ret = 0, i;
976         struct page **pages;
977         unsigned long mmun_start;       /* For mmu_notifiers */
978         unsigned long mmun_end;         /* For mmu_notifiers */
979
980         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
981                         GFP_KERNEL);
982         if (unlikely(!pages)) {
983                 ret |= VM_FAULT_OOM;
984                 goto out;
985         }
986
987         for (i = 0; i < HPAGE_PMD_NR; i++) {
988                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
989                                                __GFP_OTHER_NODE,
990                                                vma, address, page_to_nid(page));
991                 if (unlikely(!pages[i] ||
992                              mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
993                                                    &memcg))) {
994                         if (pages[i])
995                                 put_page(pages[i]);
996                         while (--i >= 0) {
997                                 memcg = (void *)page_private(pages[i]);
998                                 set_page_private(pages[i], 0);
999                                 mem_cgroup_cancel_charge(pages[i], memcg);
1000                                 put_page(pages[i]);
1001                         }
1002                         kfree(pages);
1003                         ret |= VM_FAULT_OOM;
1004                         goto out;
1005                 }
1006                 set_page_private(pages[i], (unsigned long)memcg);
1007         }
1008
1009         for (i = 0; i < HPAGE_PMD_NR; i++) {
1010                 copy_user_highpage(pages[i], page + i,
1011                                    haddr + PAGE_SIZE * i, vma);
1012                 __SetPageUptodate(pages[i]);
1013                 cond_resched();
1014         }
1015
1016         mmun_start = haddr;
1017         mmun_end   = haddr + HPAGE_PMD_SIZE;
1018         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1019
1020         ptl = pmd_lock(mm, pmd);
1021         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1022                 goto out_free_pages;
1023         VM_BUG_ON_PAGE(!PageHead(page), page);
1024
1025         pmdp_clear_flush_notify(vma, haddr, pmd);
1026         /* leave pmd empty until pte is filled */
1027
1028         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1029         pmd_populate(mm, &_pmd, pgtable);
1030
1031         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1032                 pte_t *pte, entry;
1033                 entry = mk_pte(pages[i], vma->vm_page_prot);
1034                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1035                 memcg = (void *)page_private(pages[i]);
1036                 set_page_private(pages[i], 0);
1037                 page_add_new_anon_rmap(pages[i], vma, haddr);
1038                 mem_cgroup_commit_charge(pages[i], memcg, false);
1039                 lru_cache_add_active_or_unevictable(pages[i], vma);
1040                 pte = pte_offset_map(&_pmd, haddr);
1041                 VM_BUG_ON(!pte_none(*pte));
1042                 set_pte_at(mm, haddr, pte, entry);
1043                 pte_unmap(pte);
1044         }
1045         kfree(pages);
1046
1047         smp_wmb(); /* make pte visible before pmd */
1048         pmd_populate(mm, pmd, pgtable);
1049         page_remove_rmap(page);
1050         spin_unlock(ptl);
1051
1052         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1053
1054         ret |= VM_FAULT_WRITE;
1055         put_page(page);
1056
1057 out:
1058         return ret;
1059
1060 out_free_pages:
1061         spin_unlock(ptl);
1062         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1063         for (i = 0; i < HPAGE_PMD_NR; i++) {
1064                 memcg = (void *)page_private(pages[i]);
1065                 set_page_private(pages[i], 0);
1066                 mem_cgroup_cancel_charge(pages[i], memcg);
1067                 put_page(pages[i]);
1068         }
1069         kfree(pages);
1070         goto out;
1071 }
1072
1073 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1074                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1075 {
1076         spinlock_t *ptl;
1077         int ret = 0;
1078         struct page *page = NULL, *new_page;
1079         struct mem_cgroup *memcg;
1080         unsigned long haddr;
1081         unsigned long mmun_start;       /* For mmu_notifiers */
1082         unsigned long mmun_end;         /* For mmu_notifiers */
1083
1084         ptl = pmd_lockptr(mm, pmd);
1085         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1086         haddr = address & HPAGE_PMD_MASK;
1087         if (is_huge_zero_pmd(orig_pmd))
1088                 goto alloc;
1089         spin_lock(ptl);
1090         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1091                 goto out_unlock;
1092
1093         page = pmd_page(orig_pmd);
1094         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1095         if (page_mapcount(page) == 1) {
1096                 pmd_t entry;
1097                 entry = pmd_mkyoung(orig_pmd);
1098                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1099                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1100                         update_mmu_cache_pmd(vma, address, pmd);
1101                 ret |= VM_FAULT_WRITE;
1102                 goto out_unlock;
1103         }
1104         get_user_huge_page(page);
1105         spin_unlock(ptl);
1106 alloc:
1107         if (transparent_hugepage_enabled(vma) &&
1108             !transparent_hugepage_debug_cow()) {
1109                 gfp_t gfp;
1110
1111                 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1112                 new_page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
1113         } else
1114                 new_page = NULL;
1115
1116         if (unlikely(!new_page)) {
1117                 if (!page) {
1118                         split_huge_page_pmd(vma, address, pmd);
1119                         ret |= VM_FAULT_FALLBACK;
1120                 } else {
1121                         ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1122                                         pmd, orig_pmd, page, haddr);
1123                         if (ret & VM_FAULT_OOM) {
1124                                 split_huge_page(page);
1125                                 ret |= VM_FAULT_FALLBACK;
1126                         }
1127                         put_user_huge_page(page);
1128                 }
1129                 count_vm_event(THP_FAULT_FALLBACK);
1130                 goto out;
1131         }
1132
1133         if (unlikely(mem_cgroup_try_charge(new_page, mm,
1134                                            GFP_TRANSHUGE, &memcg))) {
1135                 put_page(new_page);
1136                 if (page) {
1137                         split_huge_page(page);
1138                         put_user_huge_page(page);
1139                 } else
1140                         split_huge_page_pmd(vma, address, pmd);
1141                 ret |= VM_FAULT_FALLBACK;
1142                 count_vm_event(THP_FAULT_FALLBACK);
1143                 goto out;
1144         }
1145
1146         count_vm_event(THP_FAULT_ALLOC);
1147
1148         if (!page)
1149                 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1150         else
1151                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1152         __SetPageUptodate(new_page);
1153
1154         mmun_start = haddr;
1155         mmun_end   = haddr + HPAGE_PMD_SIZE;
1156         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1157
1158         spin_lock(ptl);
1159         if (page)
1160                 put_user_huge_page(page);
1161         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1162                 spin_unlock(ptl);
1163                 mem_cgroup_cancel_charge(new_page, memcg);
1164                 put_page(new_page);
1165                 goto out_mn;
1166         } else {
1167                 pmd_t entry;
1168                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1169                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1170                 pmdp_clear_flush_notify(vma, haddr, pmd);
1171                 page_add_new_anon_rmap(new_page, vma, haddr);
1172                 mem_cgroup_commit_charge(new_page, memcg, false);
1173                 lru_cache_add_active_or_unevictable(new_page, vma);
1174                 set_pmd_at(mm, haddr, pmd, entry);
1175                 update_mmu_cache_pmd(vma, address, pmd);
1176                 if (!page) {
1177                         add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1178                         put_huge_zero_page();
1179                 } else {
1180                         VM_BUG_ON_PAGE(!PageHead(page), page);
1181                         page_remove_rmap(page);
1182                         put_page(page);
1183                 }
1184                 ret |= VM_FAULT_WRITE;
1185         }
1186         spin_unlock(ptl);
1187 out_mn:
1188         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1189 out:
1190         return ret;
1191 out_unlock:
1192         spin_unlock(ptl);
1193         return ret;
1194 }
1195
1196 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1197                                    unsigned long addr,
1198                                    pmd_t *pmd,
1199                                    unsigned int flags)
1200 {
1201         struct mm_struct *mm = vma->vm_mm;
1202         struct page *page = NULL;
1203
1204         assert_spin_locked(pmd_lockptr(mm, pmd));
1205
1206         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1207                 goto out;
1208
1209         /* Avoid dumping huge zero page */
1210         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1211                 return ERR_PTR(-EFAULT);
1212
1213         /* Full NUMA hinting faults to serialise migration in fault paths */
1214         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1215                 goto out;
1216
1217         page = pmd_page(*pmd);
1218         VM_BUG_ON_PAGE(!PageHead(page), page);
1219         if (flags & FOLL_TOUCH) {
1220                 pmd_t _pmd;
1221                 /*
1222                  * We should set the dirty bit only for FOLL_WRITE but
1223                  * for now the dirty bit in the pmd is meaningless.
1224                  * And if the dirty bit will become meaningful and
1225                  * we'll only set it with FOLL_WRITE, an atomic
1226                  * set_bit will be required on the pmd to set the
1227                  * young bit, instead of the current set_pmd_at.
1228                  */
1229                 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1230                 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1231                                           pmd, _pmd,  1))
1232                         update_mmu_cache_pmd(vma, addr, pmd);
1233         }
1234         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1235                 if (page->mapping && trylock_page(page)) {
1236                         lru_add_drain();
1237                         if (page->mapping)
1238                                 mlock_vma_page(page);
1239                         unlock_page(page);
1240                 }
1241         }
1242         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1243         VM_BUG_ON_PAGE(!PageCompound(page), page);
1244         if (flags & FOLL_GET)
1245                 get_page_foll(page);
1246
1247 out:
1248         return page;
1249 }
1250
1251 /* NUMA hinting page fault entry point for trans huge pmds */
1252 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1253                                 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1254 {
1255         spinlock_t *ptl;
1256         struct anon_vma *anon_vma = NULL;
1257         struct page *page;
1258         unsigned long haddr = addr & HPAGE_PMD_MASK;
1259         int page_nid = -1, this_nid = numa_node_id();
1260         int target_nid, last_cpupid = -1;
1261         bool page_locked;
1262         bool migrated = false;
1263         bool was_writable;
1264         int flags = 0;
1265
1266         /* A PROT_NONE fault should not end up here */
1267         BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1268
1269         ptl = pmd_lock(mm, pmdp);
1270         if (unlikely(!pmd_same(pmd, *pmdp)))
1271                 goto out_unlock;
1272
1273         /*
1274          * If there are potential migrations, wait for completion and retry
1275          * without disrupting NUMA hinting information. Do not relock and
1276          * check_same as the page may no longer be mapped.
1277          */
1278         if (unlikely(pmd_trans_migrating(*pmdp))) {
1279                 page = pmd_page(*pmdp);
1280                 spin_unlock(ptl);
1281                 wait_on_page_locked(page);
1282                 goto out;
1283         }
1284
1285         page = pmd_page(pmd);
1286         BUG_ON(is_huge_zero_page(page));
1287         page_nid = page_to_nid(page);
1288         last_cpupid = page_cpupid_last(page);
1289         count_vm_numa_event(NUMA_HINT_FAULTS);
1290         if (page_nid == this_nid) {
1291                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1292                 flags |= TNF_FAULT_LOCAL;
1293         }
1294
1295         /* See similar comment in do_numa_page for explanation */
1296         if (!(vma->vm_flags & VM_WRITE))
1297                 flags |= TNF_NO_GROUP;
1298
1299         /*
1300          * Acquire the page lock to serialise THP migrations but avoid dropping
1301          * page_table_lock if at all possible
1302          */
1303         page_locked = trylock_page(page);
1304         target_nid = mpol_misplaced(page, vma, haddr);
1305         if (target_nid == -1) {
1306                 /* If the page was locked, there are no parallel migrations */
1307                 if (page_locked)
1308                         goto clear_pmdnuma;
1309         }
1310
1311         /* Migration could have started since the pmd_trans_migrating check */
1312         if (!page_locked) {
1313                 spin_unlock(ptl);
1314                 wait_on_page_locked(page);
1315                 page_nid = -1;
1316                 goto out;
1317         }
1318
1319         /*
1320          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1321          * to serialises splits
1322          */
1323         get_page(page);
1324         spin_unlock(ptl);
1325         anon_vma = page_lock_anon_vma_read(page);
1326
1327         /* Confirm the PMD did not change while page_table_lock was released */
1328         spin_lock(ptl);
1329         if (unlikely(!pmd_same(pmd, *pmdp))) {
1330                 unlock_page(page);
1331                 put_page(page);
1332                 page_nid = -1;
1333                 goto out_unlock;
1334         }
1335
1336         /* Bail if we fail to protect against THP splits for any reason */
1337         if (unlikely(!anon_vma)) {
1338                 put_page(page);
1339                 page_nid = -1;
1340                 goto clear_pmdnuma;
1341         }
1342
1343         /*
1344          * Migrate the THP to the requested node, returns with page unlocked
1345          * and access rights restored.
1346          */
1347         spin_unlock(ptl);
1348         migrated = migrate_misplaced_transhuge_page(mm, vma,
1349                                 pmdp, pmd, addr, page, target_nid);
1350         if (migrated) {
1351                 flags |= TNF_MIGRATED;
1352                 page_nid = target_nid;
1353         } else
1354                 flags |= TNF_MIGRATE_FAIL;
1355
1356         goto out;
1357 clear_pmdnuma:
1358         BUG_ON(!PageLocked(page));
1359         was_writable = pmd_write(pmd);
1360         pmd = pmd_modify(pmd, vma->vm_page_prot);
1361         if (was_writable)
1362                 pmd = pmd_mkwrite(pmd);
1363         set_pmd_at(mm, haddr, pmdp, pmd);
1364         update_mmu_cache_pmd(vma, addr, pmdp);
1365         unlock_page(page);
1366 out_unlock:
1367         spin_unlock(ptl);
1368
1369 out:
1370         if (anon_vma)
1371                 page_unlock_anon_vma_read(anon_vma);
1372
1373         if (page_nid != -1)
1374                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1375
1376         return 0;
1377 }
1378
1379 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1380                  pmd_t *pmd, unsigned long addr)
1381 {
1382         spinlock_t *ptl;
1383         int ret = 0;
1384
1385         if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1386                 struct page *page;
1387                 pgtable_t pgtable;
1388                 pmd_t orig_pmd;
1389                 /*
1390                  * For architectures like ppc64 we look at deposited pgtable
1391                  * when calling pmdp_get_and_clear. So do the
1392                  * pgtable_trans_huge_withdraw after finishing pmdp related
1393                  * operations.
1394                  */
1395                 orig_pmd = pmdp_get_and_clear_full(tlb->mm, addr, pmd,
1396                                                    tlb->fullmm);
1397                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1398                 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1399                 if (is_huge_zero_pmd(orig_pmd)) {
1400                         atomic_long_dec(&tlb->mm->nr_ptes);
1401                         spin_unlock(ptl);
1402                         put_huge_zero_page();
1403                 } else {
1404                         page = pmd_page(orig_pmd);
1405                         page_remove_rmap(page);
1406                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1407                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1408                         VM_BUG_ON_PAGE(!PageHead(page), page);
1409                         atomic_long_dec(&tlb->mm->nr_ptes);
1410                         spin_unlock(ptl);
1411                         tlb_remove_page(tlb, page);
1412                 }
1413                 pte_free(tlb->mm, pgtable);
1414                 ret = 1;
1415         }
1416         return ret;
1417 }
1418
1419 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1420                   unsigned long old_addr,
1421                   unsigned long new_addr, unsigned long old_end,
1422                   pmd_t *old_pmd, pmd_t *new_pmd)
1423 {
1424         spinlock_t *old_ptl, *new_ptl;
1425         int ret = 0;
1426         pmd_t pmd;
1427
1428         struct mm_struct *mm = vma->vm_mm;
1429
1430         if ((old_addr & ~HPAGE_PMD_MASK) ||
1431             (new_addr & ~HPAGE_PMD_MASK) ||
1432             old_end - old_addr < HPAGE_PMD_SIZE ||
1433             (new_vma->vm_flags & VM_NOHUGEPAGE))
1434                 goto out;
1435
1436         /*
1437          * The destination pmd shouldn't be established, free_pgtables()
1438          * should have release it.
1439          */
1440         if (WARN_ON(!pmd_none(*new_pmd))) {
1441                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1442                 goto out;
1443         }
1444
1445         /*
1446          * We don't have to worry about the ordering of src and dst
1447          * ptlocks because exclusive mmap_sem prevents deadlock.
1448          */
1449         ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
1450         if (ret == 1) {
1451                 new_ptl = pmd_lockptr(mm, new_pmd);
1452                 if (new_ptl != old_ptl)
1453                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1454                 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1455                 VM_BUG_ON(!pmd_none(*new_pmd));
1456
1457                 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1458                         pgtable_t pgtable;
1459                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1460                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1461                 }
1462                 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1463                 if (new_ptl != old_ptl)
1464                         spin_unlock(new_ptl);
1465                 spin_unlock(old_ptl);
1466         }
1467 out:
1468         return ret;
1469 }
1470
1471 /*
1472  * Returns
1473  *  - 0 if PMD could not be locked
1474  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1475  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1476  */
1477 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1478                 unsigned long addr, pgprot_t newprot, int prot_numa)
1479 {
1480         struct mm_struct *mm = vma->vm_mm;
1481         spinlock_t *ptl;
1482         int ret = 0;
1483
1484         if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1485                 pmd_t entry;
1486                 bool preserve_write = prot_numa && pmd_write(*pmd);
1487                 ret = 1;
1488
1489                 /*
1490                  * Avoid trapping faults against the zero page. The read-only
1491                  * data is likely to be read-cached on the local CPU and
1492                  * local/remote hits to the zero page are not interesting.
1493                  */
1494                 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1495                         spin_unlock(ptl);
1496                         return ret;
1497                 }
1498
1499                 if (!prot_numa || !pmd_protnone(*pmd)) {
1500                         entry = pmdp_get_and_clear_notify(mm, addr, pmd);
1501                         entry = pmd_modify(entry, newprot);
1502                         if (preserve_write)
1503                                 entry = pmd_mkwrite(entry);
1504                         ret = HPAGE_PMD_NR;
1505                         set_pmd_at(mm, addr, pmd, entry);
1506                         BUG_ON(!preserve_write && pmd_write(entry));
1507                 }
1508                 spin_unlock(ptl);
1509         }
1510
1511         return ret;
1512 }
1513
1514 /*
1515  * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1516  * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1517  *
1518  * Note that if it returns 1, this routine returns without unlocking page
1519  * table locks. So callers must unlock them.
1520  */
1521 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1522                 spinlock_t **ptl)
1523 {
1524         *ptl = pmd_lock(vma->vm_mm, pmd);
1525         if (likely(pmd_trans_huge(*pmd))) {
1526                 if (unlikely(pmd_trans_splitting(*pmd))) {
1527                         spin_unlock(*ptl);
1528                         wait_split_huge_page(vma->anon_vma, pmd);
1529                         return -1;
1530                 } else {
1531                         /* Thp mapped by 'pmd' is stable, so we can
1532                          * handle it as it is. */
1533                         return 1;
1534                 }
1535         }
1536         spin_unlock(*ptl);
1537         return 0;
1538 }
1539
1540 /*
1541  * This function returns whether a given @page is mapped onto the @address
1542  * in the virtual space of @mm.
1543  *
1544  * When it's true, this function returns *pmd with holding the page table lock
1545  * and passing it back to the caller via @ptl.
1546  * If it's false, returns NULL without holding the page table lock.
1547  */
1548 pmd_t *page_check_address_pmd(struct page *page,
1549                               struct mm_struct *mm,
1550                               unsigned long address,
1551                               enum page_check_address_pmd_flag flag,
1552                               spinlock_t **ptl)
1553 {
1554         pgd_t *pgd;
1555         pud_t *pud;
1556         pmd_t *pmd;
1557
1558         if (address & ~HPAGE_PMD_MASK)
1559                 return NULL;
1560
1561         pgd = pgd_offset(mm, address);
1562         if (!pgd_present(*pgd))
1563                 return NULL;
1564         pud = pud_offset(pgd, address);
1565         if (!pud_present(*pud))
1566                 return NULL;
1567         pmd = pmd_offset(pud, address);
1568
1569         *ptl = pmd_lock(mm, pmd);
1570         if (!pmd_present(*pmd))
1571                 goto unlock;
1572         if (pmd_page(*pmd) != page)
1573                 goto unlock;
1574         /*
1575          * split_vma() may create temporary aliased mappings. There is
1576          * no risk as long as all huge pmd are found and have their
1577          * splitting bit set before __split_huge_page_refcount
1578          * runs. Finding the same huge pmd more than once during the
1579          * same rmap walk is not a problem.
1580          */
1581         if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1582             pmd_trans_splitting(*pmd))
1583                 goto unlock;
1584         if (pmd_trans_huge(*pmd)) {
1585                 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1586                           !pmd_trans_splitting(*pmd));
1587                 return pmd;
1588         }
1589 unlock:
1590         spin_unlock(*ptl);
1591         return NULL;
1592 }
1593
1594 static int __split_huge_page_splitting(struct page *page,
1595                                        struct vm_area_struct *vma,
1596                                        unsigned long address)
1597 {
1598         struct mm_struct *mm = vma->vm_mm;
1599         spinlock_t *ptl;
1600         pmd_t *pmd;
1601         int ret = 0;
1602         /* For mmu_notifiers */
1603         const unsigned long mmun_start = address;
1604         const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1605
1606         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1607         pmd = page_check_address_pmd(page, mm, address,
1608                         PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl);
1609         if (pmd) {
1610                 /*
1611                  * We can't temporarily set the pmd to null in order
1612                  * to split it, the pmd must remain marked huge at all
1613                  * times or the VM won't take the pmd_trans_huge paths
1614                  * and it won't wait on the anon_vma->root->rwsem to
1615                  * serialize against split_huge_page*.
1616                  */
1617                 pmdp_splitting_flush(vma, address, pmd);
1618
1619                 ret = 1;
1620                 spin_unlock(ptl);
1621         }
1622         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1623
1624         return ret;
1625 }
1626
1627 static void __split_huge_page_refcount(struct page *page,
1628                                        struct list_head *list)
1629 {
1630         int i;
1631         struct zone *zone = page_zone(page);
1632         struct lruvec *lruvec;
1633         int tail_count = 0;
1634
1635         /* prevent PageLRU to go away from under us, and freeze lru stats */
1636         spin_lock_irq(&zone->lru_lock);
1637         lruvec = mem_cgroup_page_lruvec(page, zone);
1638
1639         compound_lock(page);
1640         /* complete memcg works before add pages to LRU */
1641         mem_cgroup_split_huge_fixup(page);
1642
1643         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1644                 struct page *page_tail = page + i;
1645
1646                 /* tail_page->_mapcount cannot change */
1647                 BUG_ON(page_mapcount(page_tail) < 0);
1648                 tail_count += page_mapcount(page_tail);
1649                 /* check for overflow */
1650                 BUG_ON(tail_count < 0);
1651                 BUG_ON(atomic_read(&page_tail->_count) != 0);
1652                 /*
1653                  * tail_page->_count is zero and not changing from
1654                  * under us. But get_page_unless_zero() may be running
1655                  * from under us on the tail_page. If we used
1656                  * atomic_set() below instead of atomic_add(), we
1657                  * would then run atomic_set() concurrently with
1658                  * get_page_unless_zero(), and atomic_set() is
1659                  * implemented in C not using locked ops. spin_unlock
1660                  * on x86 sometime uses locked ops because of PPro
1661                  * errata 66, 92, so unless somebody can guarantee
1662                  * atomic_set() here would be safe on all archs (and
1663                  * not only on x86), it's safer to use atomic_add().
1664                  */
1665                 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1666                            &page_tail->_count);
1667
1668                 /* after clearing PageTail the gup refcount can be released */
1669                 smp_mb__after_atomic();
1670
1671                 /*
1672                  * retain hwpoison flag of the poisoned tail page:
1673                  *   fix for the unsuitable process killed on Guest Machine(KVM)
1674                  *   by the memory-failure.
1675                  */
1676                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1677                 page_tail->flags |= (page->flags &
1678                                      ((1L << PG_referenced) |
1679                                       (1L << PG_swapbacked) |
1680                                       (1L << PG_mlocked) |
1681                                       (1L << PG_uptodate) |
1682                                       (1L << PG_active) |
1683                                       (1L << PG_unevictable)));
1684                 page_tail->flags |= (1L << PG_dirty);
1685
1686                 /* clear PageTail before overwriting first_page */
1687                 smp_wmb();
1688
1689                 /*
1690                  * __split_huge_page_splitting() already set the
1691                  * splitting bit in all pmd that could map this
1692                  * hugepage, that will ensure no CPU can alter the
1693                  * mapcount on the head page. The mapcount is only
1694                  * accounted in the head page and it has to be
1695                  * transferred to all tail pages in the below code. So
1696                  * for this code to be safe, the split the mapcount
1697                  * can't change. But that doesn't mean userland can't
1698                  * keep changing and reading the page contents while
1699                  * we transfer the mapcount, so the pmd splitting
1700                  * status is achieved setting a reserved bit in the
1701                  * pmd, not by clearing the present bit.
1702                 */
1703                 page_tail->_mapcount = page->_mapcount;
1704
1705                 BUG_ON(page_tail->mapping);
1706                 page_tail->mapping = page->mapping;
1707
1708                 page_tail->index = page->index + i;
1709                 page_cpupid_xchg_last(page_tail, page_cpupid_last(page));
1710
1711                 BUG_ON(!PageAnon(page_tail));
1712                 BUG_ON(!PageUptodate(page_tail));
1713                 BUG_ON(!PageDirty(page_tail));
1714                 BUG_ON(!PageSwapBacked(page_tail));
1715
1716                 lru_add_page_tail(page, page_tail, lruvec, list);
1717         }
1718         atomic_sub(tail_count, &page->_count);
1719         BUG_ON(atomic_read(&page->_count) <= 0);
1720
1721         __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1722
1723         ClearPageCompound(page);
1724         compound_unlock(page);
1725         spin_unlock_irq(&zone->lru_lock);
1726
1727         for (i = 1; i < HPAGE_PMD_NR; i++) {
1728                 struct page *page_tail = page + i;
1729                 BUG_ON(page_count(page_tail) <= 0);
1730                 /*
1731                  * Tail pages may be freed if there wasn't any mapping
1732                  * like if add_to_swap() is running on a lru page that
1733                  * had its mapping zapped. And freeing these pages
1734                  * requires taking the lru_lock so we do the put_page
1735                  * of the tail pages after the split is complete.
1736                  */
1737                 put_page(page_tail);
1738         }
1739
1740         /*
1741          * Only the head page (now become a regular page) is required
1742          * to be pinned by the caller.
1743          */
1744         BUG_ON(page_count(page) <= 0);
1745 }
1746
1747 static int __split_huge_page_map(struct page *page,
1748                                  struct vm_area_struct *vma,
1749                                  unsigned long address)
1750 {
1751         struct mm_struct *mm = vma->vm_mm;
1752         spinlock_t *ptl;
1753         pmd_t *pmd, _pmd;
1754         int ret = 0, i;
1755         pgtable_t pgtable;
1756         unsigned long haddr;
1757
1758         pmd = page_check_address_pmd(page, mm, address,
1759                         PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl);
1760         if (pmd) {
1761                 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1762                 pmd_populate(mm, &_pmd, pgtable);
1763                 if (pmd_write(*pmd))
1764                         BUG_ON(page_mapcount(page) != 1);
1765
1766                 haddr = address;
1767                 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1768                         pte_t *pte, entry;
1769                         BUG_ON(PageCompound(page+i));
1770                         /*
1771                          * Note that NUMA hinting access restrictions are not
1772                          * transferred to avoid any possibility of altering
1773                          * permissions across VMAs.
1774                          */
1775                         entry = mk_pte(page + i, vma->vm_page_prot);
1776                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1777                         if (!pmd_write(*pmd))
1778                                 entry = pte_wrprotect(entry);
1779                         if (!pmd_young(*pmd))
1780                                 entry = pte_mkold(entry);
1781                         pte = pte_offset_map(&_pmd, haddr);
1782                         BUG_ON(!pte_none(*pte));
1783                         set_pte_at(mm, haddr, pte, entry);
1784                         pte_unmap(pte);
1785                 }
1786
1787                 smp_wmb(); /* make pte visible before pmd */
1788                 /*
1789                  * Up to this point the pmd is present and huge and
1790                  * userland has the whole access to the hugepage
1791                  * during the split (which happens in place). If we
1792                  * overwrite the pmd with the not-huge version
1793                  * pointing to the pte here (which of course we could
1794                  * if all CPUs were bug free), userland could trigger
1795                  * a small page size TLB miss on the small sized TLB
1796                  * while the hugepage TLB entry is still established
1797                  * in the huge TLB. Some CPU doesn't like that. See
1798                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1799                  * Erratum 383 on page 93. Intel should be safe but is
1800                  * also warns that it's only safe if the permission
1801                  * and cache attributes of the two entries loaded in
1802                  * the two TLB is identical (which should be the case
1803                  * here). But it is generally safer to never allow
1804                  * small and huge TLB entries for the same virtual
1805                  * address to be loaded simultaneously. So instead of
1806                  * doing "pmd_populate(); flush_tlb_range();" we first
1807                  * mark the current pmd notpresent (atomically because
1808                  * here the pmd_trans_huge and pmd_trans_splitting
1809                  * must remain set at all times on the pmd until the
1810                  * split is complete for this pmd), then we flush the
1811                  * SMP TLB and finally we write the non-huge version
1812                  * of the pmd entry with pmd_populate.
1813                  */
1814                 pmdp_invalidate(vma, address, pmd);
1815                 pmd_populate(mm, pmd, pgtable);
1816                 ret = 1;
1817                 spin_unlock(ptl);
1818         }
1819
1820         return ret;
1821 }
1822
1823 /* must be called with anon_vma->root->rwsem held */
1824 static void __split_huge_page(struct page *page,
1825                               struct anon_vma *anon_vma,
1826                               struct list_head *list)
1827 {
1828         int mapcount, mapcount2;
1829         pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1830         struct anon_vma_chain *avc;
1831
1832         BUG_ON(!PageHead(page));
1833         BUG_ON(PageTail(page));
1834
1835         mapcount = 0;
1836         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1837                 struct vm_area_struct *vma = avc->vma;
1838                 unsigned long addr = vma_address(page, vma);
1839                 BUG_ON(is_vma_temporary_stack(vma));
1840                 mapcount += __split_huge_page_splitting(page, vma, addr);
1841         }
1842         /*
1843          * It is critical that new vmas are added to the tail of the
1844          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1845          * and establishes a child pmd before
1846          * __split_huge_page_splitting() freezes the parent pmd (so if
1847          * we fail to prevent copy_huge_pmd() from running until the
1848          * whole __split_huge_page() is complete), we will still see
1849          * the newly established pmd of the child later during the
1850          * walk, to be able to set it as pmd_trans_splitting too.
1851          */
1852         if (mapcount != page_mapcount(page)) {
1853                 pr_err("mapcount %d page_mapcount %d\n",
1854                         mapcount, page_mapcount(page));
1855                 BUG();
1856         }
1857
1858         __split_huge_page_refcount(page, list);
1859
1860         mapcount2 = 0;
1861         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1862                 struct vm_area_struct *vma = avc->vma;
1863                 unsigned long addr = vma_address(page, vma);
1864                 BUG_ON(is_vma_temporary_stack(vma));
1865                 mapcount2 += __split_huge_page_map(page, vma, addr);
1866         }
1867         if (mapcount != mapcount2) {
1868                 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n",
1869                         mapcount, mapcount2, page_mapcount(page));
1870                 BUG();
1871         }
1872 }
1873
1874 /*
1875  * Split a hugepage into normal pages. This doesn't change the position of head
1876  * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1877  * @list. Both head page and tail pages will inherit mapping, flags, and so on
1878  * from the hugepage.
1879  * Return 0 if the hugepage is split successfully otherwise return 1.
1880  */
1881 int split_huge_page_to_list(struct page *page, struct list_head *list)
1882 {
1883         struct anon_vma *anon_vma;
1884         int ret = 1;
1885
1886         BUG_ON(is_huge_zero_page(page));
1887         BUG_ON(!PageAnon(page));
1888
1889         /*
1890          * The caller does not necessarily hold an mmap_sem that would prevent
1891          * the anon_vma disappearing so we first we take a reference to it
1892          * and then lock the anon_vma for write. This is similar to
1893          * page_lock_anon_vma_read except the write lock is taken to serialise
1894          * against parallel split or collapse operations.
1895          */
1896         anon_vma = page_get_anon_vma(page);
1897         if (!anon_vma)
1898                 goto out;
1899         anon_vma_lock_write(anon_vma);
1900
1901         ret = 0;
1902         if (!PageCompound(page))
1903                 goto out_unlock;
1904
1905         BUG_ON(!PageSwapBacked(page));
1906         __split_huge_page(page, anon_vma, list);
1907         count_vm_event(THP_SPLIT);
1908
1909         BUG_ON(PageCompound(page));
1910 out_unlock:
1911         anon_vma_unlock_write(anon_vma);
1912         put_anon_vma(anon_vma);
1913 out:
1914         return ret;
1915 }
1916
1917 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1918
1919 int hugepage_madvise(struct vm_area_struct *vma,
1920                      unsigned long *vm_flags, int advice)
1921 {
1922         switch (advice) {
1923         case MADV_HUGEPAGE:
1924 #ifdef CONFIG_S390
1925                 /*
1926                  * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1927                  * can't handle this properly after s390_enable_sie, so we simply
1928                  * ignore the madvise to prevent qemu from causing a SIGSEGV.
1929                  */
1930                 if (mm_has_pgste(vma->vm_mm))
1931                         return 0;
1932 #endif
1933                 /*
1934                  * Be somewhat over-protective like KSM for now!
1935                  */
1936                 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1937                         return -EINVAL;
1938                 *vm_flags &= ~VM_NOHUGEPAGE;
1939                 *vm_flags |= VM_HUGEPAGE;
1940                 /*
1941                  * If the vma become good for khugepaged to scan,
1942                  * register it here without waiting a page fault that
1943                  * may not happen any time soon.
1944                  */
1945                 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1946                         return -ENOMEM;
1947                 break;
1948         case MADV_NOHUGEPAGE:
1949                 /*
1950                  * Be somewhat over-protective like KSM for now!
1951                  */
1952                 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1953                         return -EINVAL;
1954                 *vm_flags &= ~VM_HUGEPAGE;
1955                 *vm_flags |= VM_NOHUGEPAGE;
1956                 /*
1957                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1958                  * this vma even if we leave the mm registered in khugepaged if
1959                  * it got registered before VM_NOHUGEPAGE was set.
1960                  */
1961                 break;
1962         }
1963
1964         return 0;
1965 }
1966
1967 static int __init khugepaged_slab_init(void)
1968 {
1969         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1970                                           sizeof(struct mm_slot),
1971                                           __alignof__(struct mm_slot), 0, NULL);
1972         if (!mm_slot_cache)
1973                 return -ENOMEM;
1974
1975         return 0;
1976 }
1977
1978 static inline struct mm_slot *alloc_mm_slot(void)
1979 {
1980         if (!mm_slot_cache)     /* initialization failed */
1981                 return NULL;
1982         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1983 }
1984
1985 static inline void free_mm_slot(struct mm_slot *mm_slot)
1986 {
1987         kmem_cache_free(mm_slot_cache, mm_slot);
1988 }
1989
1990 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1991 {
1992         struct mm_slot *mm_slot;
1993
1994         hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1995                 if (mm == mm_slot->mm)
1996                         return mm_slot;
1997
1998         return NULL;
1999 }
2000
2001 static void insert_to_mm_slots_hash(struct mm_struct *mm,
2002                                     struct mm_slot *mm_slot)
2003 {
2004         mm_slot->mm = mm;
2005         hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
2006 }
2007
2008 static inline int khugepaged_test_exit(struct mm_struct *mm)
2009 {
2010         return atomic_read(&mm->mm_users) == 0;
2011 }
2012
2013 int __khugepaged_enter(struct mm_struct *mm)
2014 {
2015         struct mm_slot *mm_slot;
2016         int wakeup;
2017
2018         mm_slot = alloc_mm_slot();
2019         if (!mm_slot)
2020                 return -ENOMEM;
2021
2022         /* __khugepaged_exit() must not run from under us */
2023         VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
2024         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
2025                 free_mm_slot(mm_slot);
2026                 return 0;
2027         }
2028
2029         spin_lock(&khugepaged_mm_lock);
2030         insert_to_mm_slots_hash(mm, mm_slot);
2031         /*
2032          * Insert just behind the scanning cursor, to let the area settle
2033          * down a little.
2034          */
2035         wakeup = list_empty(&khugepaged_scan.mm_head);
2036         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
2037         spin_unlock(&khugepaged_mm_lock);
2038
2039         atomic_inc(&mm->mm_count);
2040         if (wakeup)
2041                 wake_up_interruptible(&khugepaged_wait);
2042
2043         return 0;
2044 }
2045
2046 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
2047                                unsigned long vm_flags)
2048 {
2049         unsigned long hstart, hend;
2050         if (!vma->anon_vma)
2051                 /*
2052                  * Not yet faulted in so we will register later in the
2053                  * page fault if needed.
2054                  */
2055                 return 0;
2056         if (vma->vm_ops)
2057                 /* khugepaged not yet working on file or special mappings */
2058                 return 0;
2059         VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
2060         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2061         hend = vma->vm_end & HPAGE_PMD_MASK;
2062         if (hstart < hend)
2063                 return khugepaged_enter(vma, vm_flags);
2064         return 0;
2065 }
2066
2067 void __khugepaged_exit(struct mm_struct *mm)
2068 {
2069         struct mm_slot *mm_slot;
2070         int free = 0;
2071
2072         spin_lock(&khugepaged_mm_lock);
2073         mm_slot = get_mm_slot(mm);
2074         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2075                 hash_del(&mm_slot->hash);
2076                 list_del(&mm_slot->mm_node);
2077                 free = 1;
2078         }
2079         spin_unlock(&khugepaged_mm_lock);
2080
2081         if (free) {
2082                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2083                 free_mm_slot(mm_slot);
2084                 mmdrop(mm);
2085         } else if (mm_slot) {
2086                 /*
2087                  * This is required to serialize against
2088                  * khugepaged_test_exit() (which is guaranteed to run
2089                  * under mmap sem read mode). Stop here (after we
2090                  * return all pagetables will be destroyed) until
2091                  * khugepaged has finished working on the pagetables
2092                  * under the mmap_sem.
2093                  */
2094                 down_write(&mm->mmap_sem);
2095                 up_write(&mm->mmap_sem);
2096         }
2097 }
2098
2099 static void release_pte_page(struct page *page)
2100 {
2101         /* 0 stands for page_is_file_cache(page) == false */
2102         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2103         unlock_page(page);
2104         putback_lru_page(page);
2105 }
2106
2107 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2108 {
2109         while (--_pte >= pte) {
2110                 pte_t pteval = *_pte;
2111                 if (!pte_none(pteval))
2112                         release_pte_page(pte_page(pteval));
2113         }
2114 }
2115
2116 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2117                                         unsigned long address,
2118                                         pte_t *pte)
2119 {
2120         struct page *page;
2121         pte_t *_pte;
2122         int none = 0;
2123         bool referenced = false, writable = false;
2124         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2125              _pte++, address += PAGE_SIZE) {
2126                 pte_t pteval = *_pte;
2127                 if (pte_none(pteval)) {
2128                         if (++none <= khugepaged_max_ptes_none)
2129                                 continue;
2130                         else
2131                                 goto out;
2132                 }
2133                 if (!pte_present(pteval))
2134                         goto out;
2135                 page = vm_normal_page(vma, address, pteval);
2136                 if (unlikely(!page))
2137                         goto out;
2138
2139                 VM_BUG_ON_PAGE(PageCompound(page), page);
2140                 VM_BUG_ON_PAGE(!PageAnon(page), page);
2141                 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2142
2143                 /*
2144                  * We can do it before isolate_lru_page because the
2145                  * page can't be freed from under us. NOTE: PG_lock
2146                  * is needed to serialize against split_huge_page
2147                  * when invoked from the VM.
2148                  */
2149                 if (!trylock_page(page))
2150                         goto out;
2151
2152                 /*
2153                  * cannot use mapcount: can't collapse if there's a gup pin.
2154                  * The page must only be referenced by the scanned process
2155                  * and page swap cache.
2156                  */
2157                 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2158                         unlock_page(page);
2159                         goto out;
2160                 }
2161                 if (pte_write(pteval)) {
2162                         writable = true;
2163                 } else {
2164                         if (PageSwapCache(page) && !reuse_swap_page(page)) {
2165                                 unlock_page(page);
2166                                 goto out;
2167                         }
2168                         /*
2169                          * Page is not in the swap cache. It can be collapsed
2170                          * into a THP.
2171                          */
2172                 }
2173
2174                 /*
2175                  * Isolate the page to avoid collapsing an hugepage
2176                  * currently in use by the VM.
2177                  */
2178                 if (isolate_lru_page(page)) {
2179                         unlock_page(page);
2180                         goto out;
2181                 }
2182                 /* 0 stands for page_is_file_cache(page) == false */
2183                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2184                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2185                 VM_BUG_ON_PAGE(PageLRU(page), page);
2186
2187                 /* If there is no mapped pte young don't collapse the page */
2188                 if (pte_young(pteval) || PageReferenced(page) ||
2189                     mmu_notifier_test_young(vma->vm_mm, address))
2190                         referenced = true;
2191         }
2192         if (likely(referenced && writable))
2193                 return 1;
2194 out:
2195         release_pte_pages(pte, _pte);
2196         return 0;
2197 }
2198
2199 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2200                                       struct vm_area_struct *vma,
2201                                       unsigned long address,
2202                                       spinlock_t *ptl)
2203 {
2204         pte_t *_pte;
2205         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2206                 pte_t pteval = *_pte;
2207                 struct page *src_page;
2208
2209                 if (pte_none(pteval)) {
2210                         clear_user_highpage(page, address);
2211                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2212                 } else {
2213                         src_page = pte_page(pteval);
2214                         copy_user_highpage(page, src_page, address, vma);
2215                         VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2216                         release_pte_page(src_page);
2217                         /*
2218                          * ptl mostly unnecessary, but preempt has to
2219                          * be disabled to update the per-cpu stats
2220                          * inside page_remove_rmap().
2221                          */
2222                         spin_lock(ptl);
2223                         /*
2224                          * paravirt calls inside pte_clear here are
2225                          * superfluous.
2226                          */
2227                         pte_clear(vma->vm_mm, address, _pte);
2228                         page_remove_rmap(src_page);
2229                         spin_unlock(ptl);
2230                         free_page_and_swap_cache(src_page);
2231                 }
2232
2233                 address += PAGE_SIZE;
2234                 page++;
2235         }
2236 }
2237
2238 static void khugepaged_alloc_sleep(void)
2239 {
2240         wait_event_freezable_timeout(khugepaged_wait, false,
2241                         msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2242 }
2243
2244 static int khugepaged_node_load[MAX_NUMNODES];
2245
2246 static bool khugepaged_scan_abort(int nid)
2247 {
2248         int i;
2249
2250         /*
2251          * If zone_reclaim_mode is disabled, then no extra effort is made to
2252          * allocate memory locally.
2253          */
2254         if (!zone_reclaim_mode)
2255                 return false;
2256
2257         /* If there is a count for this node already, it must be acceptable */
2258         if (khugepaged_node_load[nid])
2259                 return false;
2260
2261         for (i = 0; i < MAX_NUMNODES; i++) {
2262                 if (!khugepaged_node_load[i])
2263                         continue;
2264                 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2265                         return true;
2266         }
2267         return false;
2268 }
2269
2270 #ifdef CONFIG_NUMA
2271 static int khugepaged_find_target_node(void)
2272 {
2273         static int last_khugepaged_target_node = NUMA_NO_NODE;
2274         int nid, target_node = 0, max_value = 0;
2275
2276         /* find first node with max normal pages hit */
2277         for (nid = 0; nid < MAX_NUMNODES; nid++)
2278                 if (khugepaged_node_load[nid] > max_value) {
2279                         max_value = khugepaged_node_load[nid];
2280                         target_node = nid;
2281                 }
2282
2283         /* do some balance if several nodes have the same hit record */
2284         if (target_node <= last_khugepaged_target_node)
2285                 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2286                                 nid++)
2287                         if (max_value == khugepaged_node_load[nid]) {
2288                                 target_node = nid;
2289                                 break;
2290                         }
2291
2292         last_khugepaged_target_node = target_node;
2293         return target_node;
2294 }
2295
2296 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2297 {
2298         if (IS_ERR(*hpage)) {
2299                 if (!*wait)
2300                         return false;
2301
2302                 *wait = false;
2303                 *hpage = NULL;
2304                 khugepaged_alloc_sleep();
2305         } else if (*hpage) {
2306                 put_page(*hpage);
2307                 *hpage = NULL;
2308         }
2309
2310         return true;
2311 }
2312
2313 static struct page
2314 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2315                        struct vm_area_struct *vma, unsigned long address,
2316                        int node)
2317 {
2318         VM_BUG_ON_PAGE(*hpage, *hpage);
2319
2320         /*
2321          * Before allocating the hugepage, release the mmap_sem read lock.
2322          * The allocation can take potentially a long time if it involves
2323          * sync compaction, and we do not need to hold the mmap_sem during
2324          * that. We will recheck the vma after taking it again in write mode.
2325          */
2326         up_read(&mm->mmap_sem);
2327
2328         *hpage = alloc_pages_exact_node(node, alloc_hugepage_gfpmask(
2329                 khugepaged_defrag(), __GFP_OTHER_NODE), HPAGE_PMD_ORDER);
2330         if (unlikely(!*hpage)) {
2331                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2332                 *hpage = ERR_PTR(-ENOMEM);
2333                 return NULL;
2334         }
2335
2336         count_vm_event(THP_COLLAPSE_ALLOC);
2337         return *hpage;
2338 }
2339 #else
2340 static int khugepaged_find_target_node(void)
2341 {
2342         return 0;
2343 }
2344
2345 static inline struct page *alloc_hugepage(int defrag)
2346 {
2347         return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
2348                            HPAGE_PMD_ORDER);
2349 }
2350
2351 static struct page *khugepaged_alloc_hugepage(bool *wait)
2352 {
2353         struct page *hpage;
2354
2355         do {
2356                 hpage = alloc_hugepage(khugepaged_defrag());
2357                 if (!hpage) {
2358                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2359                         if (!*wait)
2360                                 return NULL;
2361
2362                         *wait = false;
2363                         khugepaged_alloc_sleep();
2364                 } else
2365                         count_vm_event(THP_COLLAPSE_ALLOC);
2366         } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2367
2368         return hpage;
2369 }
2370
2371 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2372 {
2373         if (!*hpage)
2374                 *hpage = khugepaged_alloc_hugepage(wait);
2375
2376         if (unlikely(!*hpage))
2377                 return false;
2378
2379         return true;
2380 }
2381
2382 static struct page
2383 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2384                        struct vm_area_struct *vma, unsigned long address,
2385                        int node)
2386 {
2387         up_read(&mm->mmap_sem);
2388         VM_BUG_ON(!*hpage);
2389         return  *hpage;
2390 }
2391 #endif
2392
2393 static bool hugepage_vma_check(struct vm_area_struct *vma)
2394 {
2395         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2396             (vma->vm_flags & VM_NOHUGEPAGE))
2397                 return false;
2398
2399         if (!vma->anon_vma || vma->vm_ops)
2400                 return false;
2401         if (is_vma_temporary_stack(vma))
2402                 return false;
2403         VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2404         return true;
2405 }
2406
2407 static void collapse_huge_page(struct mm_struct *mm,
2408                                    unsigned long address,
2409                                    struct page **hpage,
2410                                    struct vm_area_struct *vma,
2411                                    int node)
2412 {
2413         pmd_t *pmd, _pmd;
2414         pte_t *pte;
2415         pgtable_t pgtable;
2416         struct page *new_page;
2417         spinlock_t *pmd_ptl, *pte_ptl;
2418         int isolated;
2419         unsigned long hstart, hend;
2420         struct mem_cgroup *memcg;
2421         unsigned long mmun_start;       /* For mmu_notifiers */
2422         unsigned long mmun_end;         /* For mmu_notifiers */
2423
2424         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2425
2426         /* release the mmap_sem read lock. */
2427         new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2428         if (!new_page)
2429                 return;
2430
2431         if (unlikely(mem_cgroup_try_charge(new_page, mm,
2432                                            GFP_TRANSHUGE, &memcg)))
2433                 return;
2434
2435         /*
2436          * Prevent all access to pagetables with the exception of
2437          * gup_fast later hanlded by the ptep_clear_flush and the VM
2438          * handled by the anon_vma lock + PG_lock.
2439          */
2440         down_write(&mm->mmap_sem);
2441         if (unlikely(khugepaged_test_exit(mm)))
2442                 goto out;
2443
2444         vma = find_vma(mm, address);
2445         if (!vma)
2446                 goto out;
2447         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2448         hend = vma->vm_end & HPAGE_PMD_MASK;
2449         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2450                 goto out;
2451         if (!hugepage_vma_check(vma))
2452                 goto out;
2453         pmd = mm_find_pmd(mm, address);
2454         if (!pmd)
2455                 goto out;
2456
2457         anon_vma_lock_write(vma->anon_vma);
2458
2459         pte = pte_offset_map(pmd, address);
2460         pte_ptl = pte_lockptr(mm, pmd);
2461
2462         mmun_start = address;
2463         mmun_end   = address + HPAGE_PMD_SIZE;
2464         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2465         pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2466         /*
2467          * After this gup_fast can't run anymore. This also removes
2468          * any huge TLB entry from the CPU so we won't allow
2469          * huge and small TLB entries for the same virtual address
2470          * to avoid the risk of CPU bugs in that area.
2471          */
2472         _pmd = pmdp_clear_flush(vma, address, pmd);
2473         spin_unlock(pmd_ptl);
2474         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2475
2476         spin_lock(pte_ptl);
2477         isolated = __collapse_huge_page_isolate(vma, address, pte);
2478         spin_unlock(pte_ptl);
2479
2480         if (unlikely(!isolated)) {
2481                 pte_unmap(pte);
2482                 spin_lock(pmd_ptl);
2483                 BUG_ON(!pmd_none(*pmd));
2484                 /*
2485                  * We can only use set_pmd_at when establishing
2486                  * hugepmds and never for establishing regular pmds that
2487                  * points to regular pagetables. Use pmd_populate for that
2488                  */
2489                 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2490                 spin_unlock(pmd_ptl);
2491                 anon_vma_unlock_write(vma->anon_vma);
2492                 goto out;
2493         }
2494
2495         /*
2496          * All pages are isolated and locked so anon_vma rmap
2497          * can't run anymore.
2498          */
2499         anon_vma_unlock_write(vma->anon_vma);
2500
2501         __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2502         pte_unmap(pte);
2503         __SetPageUptodate(new_page);
2504         pgtable = pmd_pgtable(_pmd);
2505
2506         _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2507         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2508
2509         /*
2510          * spin_lock() below is not the equivalent of smp_wmb(), so
2511          * this is needed to avoid the copy_huge_page writes to become
2512          * visible after the set_pmd_at() write.
2513          */
2514         smp_wmb();
2515
2516         spin_lock(pmd_ptl);
2517         BUG_ON(!pmd_none(*pmd));
2518         page_add_new_anon_rmap(new_page, vma, address);
2519         mem_cgroup_commit_charge(new_page, memcg, false);
2520         lru_cache_add_active_or_unevictable(new_page, vma);
2521         pgtable_trans_huge_deposit(mm, pmd, pgtable);
2522         set_pmd_at(mm, address, pmd, _pmd);
2523         update_mmu_cache_pmd(vma, address, pmd);
2524         spin_unlock(pmd_ptl);
2525
2526         *hpage = NULL;
2527
2528         khugepaged_pages_collapsed++;
2529 out_up_write:
2530         up_write(&mm->mmap_sem);
2531         return;
2532
2533 out:
2534         mem_cgroup_cancel_charge(new_page, memcg);
2535         goto out_up_write;
2536 }
2537
2538 static int khugepaged_scan_pmd(struct mm_struct *mm,
2539                                struct vm_area_struct *vma,
2540                                unsigned long address,
2541                                struct page **hpage)
2542 {
2543         pmd_t *pmd;
2544         pte_t *pte, *_pte;
2545         int ret = 0, none = 0;
2546         struct page *page;
2547         unsigned long _address;
2548         spinlock_t *ptl;
2549         int node = NUMA_NO_NODE;
2550         bool writable = false, referenced = false;
2551
2552         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2553
2554         pmd = mm_find_pmd(mm, address);
2555         if (!pmd)
2556                 goto out;
2557
2558         memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2559         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2560         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2561              _pte++, _address += PAGE_SIZE) {
2562                 pte_t pteval = *_pte;
2563                 if (pte_none(pteval)) {
2564                         if (++none <= khugepaged_max_ptes_none)
2565                                 continue;
2566                         else
2567                                 goto out_unmap;
2568                 }
2569                 if (!pte_present(pteval))
2570                         goto out_unmap;
2571                 if (pte_write(pteval))
2572                         writable = true;
2573
2574                 page = vm_normal_page(vma, _address, pteval);
2575                 if (unlikely(!page))
2576                         goto out_unmap;
2577                 /*
2578                  * Record which node the original page is from and save this
2579                  * information to khugepaged_node_load[].
2580                  * Khupaged will allocate hugepage from the node has the max
2581                  * hit record.
2582                  */
2583                 node = page_to_nid(page);
2584                 if (khugepaged_scan_abort(node))
2585                         goto out_unmap;
2586                 khugepaged_node_load[node]++;
2587                 VM_BUG_ON_PAGE(PageCompound(page), page);
2588                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2589                         goto out_unmap;
2590                 /*
2591                  * cannot use mapcount: can't collapse if there's a gup pin.
2592                  * The page must only be referenced by the scanned process
2593                  * and page swap cache.
2594                  */
2595                 if (page_count(page) != 1 + !!PageSwapCache(page))
2596                         goto out_unmap;
2597                 if (pte_young(pteval) || PageReferenced(page) ||
2598                     mmu_notifier_test_young(vma->vm_mm, address))
2599                         referenced = true;
2600         }
2601         if (referenced && writable)
2602                 ret = 1;
2603 out_unmap:
2604         pte_unmap_unlock(pte, ptl);
2605         if (ret) {
2606                 node = khugepaged_find_target_node();
2607                 /* collapse_huge_page will return with the mmap_sem released */
2608                 collapse_huge_page(mm, address, hpage, vma, node);
2609         }
2610 out:
2611         return ret;
2612 }
2613
2614 static void collect_mm_slot(struct mm_slot *mm_slot)
2615 {
2616         struct mm_struct *mm = mm_slot->mm;
2617
2618         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2619
2620         if (khugepaged_test_exit(mm)) {
2621                 /* free mm_slot */
2622                 hash_del(&mm_slot->hash);
2623                 list_del(&mm_slot->mm_node);
2624
2625                 /*
2626                  * Not strictly needed because the mm exited already.
2627                  *
2628                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2629                  */
2630
2631                 /* khugepaged_mm_lock actually not necessary for the below */
2632                 free_mm_slot(mm_slot);
2633                 mmdrop(mm);
2634         }
2635 }
2636
2637 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2638                                             struct page **hpage)
2639         __releases(&khugepaged_mm_lock)
2640         __acquires(&khugepaged_mm_lock)
2641 {
2642         struct mm_slot *mm_slot;
2643         struct mm_struct *mm;
2644         struct vm_area_struct *vma;
2645         int progress = 0;
2646
2647         VM_BUG_ON(!pages);
2648         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2649
2650         if (khugepaged_scan.mm_slot)
2651                 mm_slot = khugepaged_scan.mm_slot;
2652         else {
2653                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2654                                      struct mm_slot, mm_node);
2655                 khugepaged_scan.address = 0;
2656                 khugepaged_scan.mm_slot = mm_slot;
2657         }
2658         spin_unlock(&khugepaged_mm_lock);
2659
2660         mm = mm_slot->mm;
2661         down_read(&mm->mmap_sem);
2662         if (unlikely(khugepaged_test_exit(mm)))
2663                 vma = NULL;
2664         else
2665                 vma = find_vma(mm, khugepaged_scan.address);
2666
2667         progress++;
2668         for (; vma; vma = vma->vm_next) {
2669                 unsigned long hstart, hend;
2670
2671                 cond_resched();
2672                 if (unlikely(khugepaged_test_exit(mm))) {
2673                         progress++;
2674                         break;
2675                 }
2676                 if (!hugepage_vma_check(vma)) {
2677 skip:
2678                         progress++;
2679                         continue;
2680                 }
2681                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2682                 hend = vma->vm_end & HPAGE_PMD_MASK;
2683                 if (hstart >= hend)
2684                         goto skip;
2685                 if (khugepaged_scan.address > hend)
2686                         goto skip;
2687                 if (khugepaged_scan.address < hstart)
2688                         khugepaged_scan.address = hstart;
2689                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2690
2691                 while (khugepaged_scan.address < hend) {
2692                         int ret;
2693                         cond_resched();
2694                         if (unlikely(khugepaged_test_exit(mm)))
2695                                 goto breakouterloop;
2696
2697                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2698                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2699                                   hend);
2700                         ret = khugepaged_scan_pmd(mm, vma,
2701                                                   khugepaged_scan.address,
2702                                                   hpage);
2703                         /* move to next address */
2704                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2705                         progress += HPAGE_PMD_NR;
2706                         if (ret)
2707                                 /* we released mmap_sem so break loop */
2708                                 goto breakouterloop_mmap_sem;
2709                         if (progress >= pages)
2710                                 goto breakouterloop;
2711                 }
2712         }
2713 breakouterloop:
2714         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2715 breakouterloop_mmap_sem:
2716
2717         spin_lock(&khugepaged_mm_lock);
2718         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2719         /*
2720          * Release the current mm_slot if this mm is about to die, or
2721          * if we scanned all vmas of this mm.
2722          */
2723         if (khugepaged_test_exit(mm) || !vma) {
2724                 /*
2725                  * Make sure that if mm_users is reaching zero while
2726                  * khugepaged runs here, khugepaged_exit will find
2727                  * mm_slot not pointing to the exiting mm.
2728                  */
2729                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2730                         khugepaged_scan.mm_slot = list_entry(
2731                                 mm_slot->mm_node.next,
2732                                 struct mm_slot, mm_node);
2733                         khugepaged_scan.address = 0;
2734                 } else {
2735                         khugepaged_scan.mm_slot = NULL;
2736                         khugepaged_full_scans++;
2737                 }
2738
2739                 collect_mm_slot(mm_slot);
2740         }
2741
2742         return progress;
2743 }
2744
2745 static int khugepaged_has_work(void)
2746 {
2747         return !list_empty(&khugepaged_scan.mm_head) &&
2748                 khugepaged_enabled();
2749 }
2750
2751 static int khugepaged_wait_event(void)
2752 {
2753         return !list_empty(&khugepaged_scan.mm_head) ||
2754                 kthread_should_stop();
2755 }
2756
2757 static void khugepaged_do_scan(void)
2758 {
2759         struct page *hpage = NULL;
2760         unsigned int progress = 0, pass_through_head = 0;
2761         unsigned int pages = khugepaged_pages_to_scan;
2762         bool wait = true;
2763
2764         barrier(); /* write khugepaged_pages_to_scan to local stack */
2765
2766         while (progress < pages) {
2767                 if (!khugepaged_prealloc_page(&hpage, &wait))
2768                         break;
2769
2770                 cond_resched();
2771
2772                 if (unlikely(kthread_should_stop() || freezing(current)))
2773                         break;
2774
2775                 spin_lock(&khugepaged_mm_lock);
2776                 if (!khugepaged_scan.mm_slot)
2777                         pass_through_head++;
2778                 if (khugepaged_has_work() &&
2779                     pass_through_head < 2)
2780                         progress += khugepaged_scan_mm_slot(pages - progress,
2781                                                             &hpage);
2782                 else
2783                         progress = pages;
2784                 spin_unlock(&khugepaged_mm_lock);
2785         }
2786
2787         if (!IS_ERR_OR_NULL(hpage))
2788                 put_page(hpage);
2789 }
2790
2791 static void khugepaged_wait_work(void)
2792 {
2793         try_to_freeze();
2794
2795         if (khugepaged_has_work()) {
2796                 if (!khugepaged_scan_sleep_millisecs)
2797                         return;
2798
2799                 wait_event_freezable_timeout(khugepaged_wait,
2800                                              kthread_should_stop(),
2801                         msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2802                 return;
2803         }
2804
2805         if (khugepaged_enabled())
2806                 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2807 }
2808
2809 static int khugepaged(void *none)
2810 {
2811         struct mm_slot *mm_slot;
2812
2813         set_freezable();
2814         set_user_nice(current, MAX_NICE);
2815
2816         while (!kthread_should_stop()) {
2817                 khugepaged_do_scan();
2818                 khugepaged_wait_work();
2819         }
2820
2821         spin_lock(&khugepaged_mm_lock);
2822         mm_slot = khugepaged_scan.mm_slot;
2823         khugepaged_scan.mm_slot = NULL;
2824         if (mm_slot)
2825                 collect_mm_slot(mm_slot);
2826         spin_unlock(&khugepaged_mm_lock);
2827         return 0;
2828 }
2829
2830 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2831                 unsigned long haddr, pmd_t *pmd)
2832 {
2833         struct mm_struct *mm = vma->vm_mm;
2834         pgtable_t pgtable;
2835         pmd_t _pmd;
2836         int i;
2837
2838         pmdp_clear_flush_notify(vma, haddr, pmd);
2839         /* leave pmd empty until pte is filled */
2840
2841         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2842         pmd_populate(mm, &_pmd, pgtable);
2843
2844         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2845                 pte_t *pte, entry;
2846                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2847                 entry = pte_mkspecial(entry);
2848                 pte = pte_offset_map(&_pmd, haddr);
2849                 VM_BUG_ON(!pte_none(*pte));
2850                 set_pte_at(mm, haddr, pte, entry);
2851                 pte_unmap(pte);
2852         }
2853         smp_wmb(); /* make pte visible before pmd */
2854         pmd_populate(mm, pmd, pgtable);
2855         put_huge_zero_page();
2856 }
2857
2858 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2859                 pmd_t *pmd)
2860 {
2861         spinlock_t *ptl;
2862         struct page *page;
2863         struct mm_struct *mm = vma->vm_mm;
2864         unsigned long haddr = address & HPAGE_PMD_MASK;
2865         unsigned long mmun_start;       /* For mmu_notifiers */
2866         unsigned long mmun_end;         /* For mmu_notifiers */
2867
2868         BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2869
2870         mmun_start = haddr;
2871         mmun_end   = haddr + HPAGE_PMD_SIZE;
2872 again:
2873         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2874         ptl = pmd_lock(mm, pmd);
2875         if (unlikely(!pmd_trans_huge(*pmd))) {
2876                 spin_unlock(ptl);
2877                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2878                 return;
2879         }
2880         if (is_huge_zero_pmd(*pmd)) {
2881                 __split_huge_zero_page_pmd(vma, haddr, pmd);
2882                 spin_unlock(ptl);
2883                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2884                 return;
2885         }
2886         page = pmd_page(*pmd);
2887         VM_BUG_ON_PAGE(!page_count(page), page);
2888         get_page(page);
2889         spin_unlock(ptl);
2890         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2891
2892         split_huge_page(page);
2893
2894         put_page(page);
2895
2896         /*
2897          * We don't always have down_write of mmap_sem here: a racing
2898          * do_huge_pmd_wp_page() might have copied-on-write to another
2899          * huge page before our split_huge_page() got the anon_vma lock.
2900          */
2901         if (unlikely(pmd_trans_huge(*pmd)))
2902                 goto again;
2903 }
2904
2905 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2906                 pmd_t *pmd)
2907 {
2908         struct vm_area_struct *vma;
2909
2910         vma = find_vma(mm, address);
2911         BUG_ON(vma == NULL);
2912         split_huge_page_pmd(vma, address, pmd);
2913 }
2914
2915 static void split_huge_page_address(struct mm_struct *mm,
2916                                     unsigned long address)
2917 {
2918         pgd_t *pgd;
2919         pud_t *pud;
2920         pmd_t *pmd;
2921
2922         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2923
2924         pgd = pgd_offset(mm, address);
2925         if (!pgd_present(*pgd))
2926                 return;
2927
2928         pud = pud_offset(pgd, address);
2929         if (!pud_present(*pud))
2930                 return;
2931
2932         pmd = pmd_offset(pud, address);
2933         if (!pmd_present(*pmd))
2934                 return;
2935         /*
2936          * Caller holds the mmap_sem write mode, so a huge pmd cannot
2937          * materialize from under us.
2938          */
2939         split_huge_page_pmd_mm(mm, address, pmd);
2940 }
2941
2942 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2943                              unsigned long start,
2944                              unsigned long end,
2945                              long adjust_next)
2946 {
2947         /*
2948          * If the new start address isn't hpage aligned and it could
2949          * previously contain an hugepage: check if we need to split
2950          * an huge pmd.
2951          */
2952         if (start & ~HPAGE_PMD_MASK &&
2953             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2954             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2955                 split_huge_page_address(vma->vm_mm, start);
2956
2957         /*
2958          * If the new end address isn't hpage aligned and it could
2959          * previously contain an hugepage: check if we need to split
2960          * an huge pmd.
2961          */
2962         if (end & ~HPAGE_PMD_MASK &&
2963             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2964             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2965                 split_huge_page_address(vma->vm_mm, end);
2966
2967         /*
2968          * If we're also updating the vma->vm_next->vm_start, if the new
2969          * vm_next->vm_start isn't page aligned and it could previously
2970          * contain an hugepage: check if we need to split an huge pmd.
2971          */
2972         if (adjust_next > 0) {
2973                 struct vm_area_struct *next = vma->vm_next;
2974                 unsigned long nstart = next->vm_start;
2975                 nstart += adjust_next << PAGE_SHIFT;
2976                 if (nstart & ~HPAGE_PMD_MASK &&
2977                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2978                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2979                         split_huge_page_address(next->vm_mm, nstart);
2980         }
2981 }