mm: vmscan: fix force-scanning small targets without swap
[linux-2.6.git] / mm / huge_memory.c
1 /*
2  *  Copyright (C) 2009  Red Hat, Inc.
3  *
4  *  This work is licensed under the terms of the GNU GPL, version 2. See
5  *  the COPYING file in the top-level directory.
6  */
7
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/highmem.h>
11 #include <linux/hugetlb.h>
12 #include <linux/mmu_notifier.h>
13 #include <linux/rmap.h>
14 #include <linux/swap.h>
15 #include <linux/mm_inline.h>
16 #include <linux/kthread.h>
17 #include <linux/khugepaged.h>
18 #include <linux/freezer.h>
19 #include <linux/mman.h>
20 #include <asm/tlb.h>
21 #include <asm/pgalloc.h>
22 #include "internal.h"
23
24 /*
25  * By default transparent hugepage support is enabled for all mappings
26  * and khugepaged scans all mappings. Defrag is only invoked by
27  * khugepaged hugepage allocations and by page faults inside
28  * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
29  * allocations.
30  */
31 unsigned long transparent_hugepage_flags __read_mostly =
32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
33         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
34 #endif
35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
36         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
37 #endif
38         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
39         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
40
41 /* default scan 8*512 pte (or vmas) every 30 second */
42 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
43 static unsigned int khugepaged_pages_collapsed;
44 static unsigned int khugepaged_full_scans;
45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
46 /* during fragmentation poll the hugepage allocator once every minute */
47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
48 static struct task_struct *khugepaged_thread __read_mostly;
49 static DEFINE_MUTEX(khugepaged_mutex);
50 static DEFINE_SPINLOCK(khugepaged_mm_lock);
51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
52 /*
53  * default collapse hugepages if there is at least one pte mapped like
54  * it would have happened if the vma was large enough during page
55  * fault.
56  */
57 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
58
59 static int khugepaged(void *none);
60 static int mm_slots_hash_init(void);
61 static int khugepaged_slab_init(void);
62 static void khugepaged_slab_free(void);
63
64 #define MM_SLOTS_HASH_HEADS 1024
65 static struct hlist_head *mm_slots_hash __read_mostly;
66 static struct kmem_cache *mm_slot_cache __read_mostly;
67
68 /**
69  * struct mm_slot - hash lookup from mm to mm_slot
70  * @hash: hash collision list
71  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
72  * @mm: the mm that this information is valid for
73  */
74 struct mm_slot {
75         struct hlist_node hash;
76         struct list_head mm_node;
77         struct mm_struct *mm;
78 };
79
80 /**
81  * struct khugepaged_scan - cursor for scanning
82  * @mm_head: the head of the mm list to scan
83  * @mm_slot: the current mm_slot we are scanning
84  * @address: the next address inside that to be scanned
85  *
86  * There is only the one khugepaged_scan instance of this cursor structure.
87  */
88 struct khugepaged_scan {
89         struct list_head mm_head;
90         struct mm_slot *mm_slot;
91         unsigned long address;
92 } khugepaged_scan = {
93         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
94 };
95
96
97 static int set_recommended_min_free_kbytes(void)
98 {
99         struct zone *zone;
100         int nr_zones = 0;
101         unsigned long recommended_min;
102         extern int min_free_kbytes;
103
104         if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
105                       &transparent_hugepage_flags) &&
106             !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
107                       &transparent_hugepage_flags))
108                 return 0;
109
110         for_each_populated_zone(zone)
111                 nr_zones++;
112
113         /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
114         recommended_min = pageblock_nr_pages * nr_zones * 2;
115
116         /*
117          * Make sure that on average at least two pageblocks are almost free
118          * of another type, one for a migratetype to fall back to and a
119          * second to avoid subsequent fallbacks of other types There are 3
120          * MIGRATE_TYPES we care about.
121          */
122         recommended_min += pageblock_nr_pages * nr_zones *
123                            MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
124
125         /* don't ever allow to reserve more than 5% of the lowmem */
126         recommended_min = min(recommended_min,
127                               (unsigned long) nr_free_buffer_pages() / 20);
128         recommended_min <<= (PAGE_SHIFT-10);
129
130         if (recommended_min > min_free_kbytes)
131                 min_free_kbytes = recommended_min;
132         setup_per_zone_wmarks();
133         return 0;
134 }
135 late_initcall(set_recommended_min_free_kbytes);
136
137 static int start_khugepaged(void)
138 {
139         int err = 0;
140         if (khugepaged_enabled()) {
141                 int wakeup;
142                 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
143                         err = -ENOMEM;
144                         goto out;
145                 }
146                 mutex_lock(&khugepaged_mutex);
147                 if (!khugepaged_thread)
148                         khugepaged_thread = kthread_run(khugepaged, NULL,
149                                                         "khugepaged");
150                 if (unlikely(IS_ERR(khugepaged_thread))) {
151                         printk(KERN_ERR
152                                "khugepaged: kthread_run(khugepaged) failed\n");
153                         err = PTR_ERR(khugepaged_thread);
154                         khugepaged_thread = NULL;
155                 }
156                 wakeup = !list_empty(&khugepaged_scan.mm_head);
157                 mutex_unlock(&khugepaged_mutex);
158                 if (wakeup)
159                         wake_up_interruptible(&khugepaged_wait);
160
161                 set_recommended_min_free_kbytes();
162         } else
163                 /* wakeup to exit */
164                 wake_up_interruptible(&khugepaged_wait);
165 out:
166         return err;
167 }
168
169 #ifdef CONFIG_SYSFS
170
171 static ssize_t double_flag_show(struct kobject *kobj,
172                                 struct kobj_attribute *attr, char *buf,
173                                 enum transparent_hugepage_flag enabled,
174                                 enum transparent_hugepage_flag req_madv)
175 {
176         if (test_bit(enabled, &transparent_hugepage_flags)) {
177                 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
178                 return sprintf(buf, "[always] madvise never\n");
179         } else if (test_bit(req_madv, &transparent_hugepage_flags))
180                 return sprintf(buf, "always [madvise] never\n");
181         else
182                 return sprintf(buf, "always madvise [never]\n");
183 }
184 static ssize_t double_flag_store(struct kobject *kobj,
185                                  struct kobj_attribute *attr,
186                                  const char *buf, size_t count,
187                                  enum transparent_hugepage_flag enabled,
188                                  enum transparent_hugepage_flag req_madv)
189 {
190         if (!memcmp("always", buf,
191                     min(sizeof("always")-1, count))) {
192                 set_bit(enabled, &transparent_hugepage_flags);
193                 clear_bit(req_madv, &transparent_hugepage_flags);
194         } else if (!memcmp("madvise", buf,
195                            min(sizeof("madvise")-1, count))) {
196                 clear_bit(enabled, &transparent_hugepage_flags);
197                 set_bit(req_madv, &transparent_hugepage_flags);
198         } else if (!memcmp("never", buf,
199                            min(sizeof("never")-1, count))) {
200                 clear_bit(enabled, &transparent_hugepage_flags);
201                 clear_bit(req_madv, &transparent_hugepage_flags);
202         } else
203                 return -EINVAL;
204
205         return count;
206 }
207
208 static ssize_t enabled_show(struct kobject *kobj,
209                             struct kobj_attribute *attr, char *buf)
210 {
211         return double_flag_show(kobj, attr, buf,
212                                 TRANSPARENT_HUGEPAGE_FLAG,
213                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
214 }
215 static ssize_t enabled_store(struct kobject *kobj,
216                              struct kobj_attribute *attr,
217                              const char *buf, size_t count)
218 {
219         ssize_t ret;
220
221         ret = double_flag_store(kobj, attr, buf, count,
222                                 TRANSPARENT_HUGEPAGE_FLAG,
223                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
224
225         if (ret > 0) {
226                 int err = start_khugepaged();
227                 if (err)
228                         ret = err;
229         }
230
231         if (ret > 0 &&
232             (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
233                       &transparent_hugepage_flags) ||
234              test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
235                       &transparent_hugepage_flags)))
236                 set_recommended_min_free_kbytes();
237
238         return ret;
239 }
240 static struct kobj_attribute enabled_attr =
241         __ATTR(enabled, 0644, enabled_show, enabled_store);
242
243 static ssize_t single_flag_show(struct kobject *kobj,
244                                 struct kobj_attribute *attr, char *buf,
245                                 enum transparent_hugepage_flag flag)
246 {
247         return sprintf(buf, "%d\n",
248                        !!test_bit(flag, &transparent_hugepage_flags));
249 }
250
251 static ssize_t single_flag_store(struct kobject *kobj,
252                                  struct kobj_attribute *attr,
253                                  const char *buf, size_t count,
254                                  enum transparent_hugepage_flag flag)
255 {
256         unsigned long value;
257         int ret;
258
259         ret = kstrtoul(buf, 10, &value);
260         if (ret < 0)
261                 return ret;
262         if (value > 1)
263                 return -EINVAL;
264
265         if (value)
266                 set_bit(flag, &transparent_hugepage_flags);
267         else
268                 clear_bit(flag, &transparent_hugepage_flags);
269
270         return count;
271 }
272
273 /*
274  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
275  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
276  * memory just to allocate one more hugepage.
277  */
278 static ssize_t defrag_show(struct kobject *kobj,
279                            struct kobj_attribute *attr, char *buf)
280 {
281         return double_flag_show(kobj, attr, buf,
282                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
283                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
284 }
285 static ssize_t defrag_store(struct kobject *kobj,
286                             struct kobj_attribute *attr,
287                             const char *buf, size_t count)
288 {
289         return double_flag_store(kobj, attr, buf, count,
290                                  TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
291                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
292 }
293 static struct kobj_attribute defrag_attr =
294         __ATTR(defrag, 0644, defrag_show, defrag_store);
295
296 #ifdef CONFIG_DEBUG_VM
297 static ssize_t debug_cow_show(struct kobject *kobj,
298                                 struct kobj_attribute *attr, char *buf)
299 {
300         return single_flag_show(kobj, attr, buf,
301                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
302 }
303 static ssize_t debug_cow_store(struct kobject *kobj,
304                                struct kobj_attribute *attr,
305                                const char *buf, size_t count)
306 {
307         return single_flag_store(kobj, attr, buf, count,
308                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
309 }
310 static struct kobj_attribute debug_cow_attr =
311         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
312 #endif /* CONFIG_DEBUG_VM */
313
314 static struct attribute *hugepage_attr[] = {
315         &enabled_attr.attr,
316         &defrag_attr.attr,
317 #ifdef CONFIG_DEBUG_VM
318         &debug_cow_attr.attr,
319 #endif
320         NULL,
321 };
322
323 static struct attribute_group hugepage_attr_group = {
324         .attrs = hugepage_attr,
325 };
326
327 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
328                                          struct kobj_attribute *attr,
329                                          char *buf)
330 {
331         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
332 }
333
334 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
335                                           struct kobj_attribute *attr,
336                                           const char *buf, size_t count)
337 {
338         unsigned long msecs;
339         int err;
340
341         err = strict_strtoul(buf, 10, &msecs);
342         if (err || msecs > UINT_MAX)
343                 return -EINVAL;
344
345         khugepaged_scan_sleep_millisecs = msecs;
346         wake_up_interruptible(&khugepaged_wait);
347
348         return count;
349 }
350 static struct kobj_attribute scan_sleep_millisecs_attr =
351         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
352                scan_sleep_millisecs_store);
353
354 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
355                                           struct kobj_attribute *attr,
356                                           char *buf)
357 {
358         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
359 }
360
361 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
362                                            struct kobj_attribute *attr,
363                                            const char *buf, size_t count)
364 {
365         unsigned long msecs;
366         int err;
367
368         err = strict_strtoul(buf, 10, &msecs);
369         if (err || msecs > UINT_MAX)
370                 return -EINVAL;
371
372         khugepaged_alloc_sleep_millisecs = msecs;
373         wake_up_interruptible(&khugepaged_wait);
374
375         return count;
376 }
377 static struct kobj_attribute alloc_sleep_millisecs_attr =
378         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
379                alloc_sleep_millisecs_store);
380
381 static ssize_t pages_to_scan_show(struct kobject *kobj,
382                                   struct kobj_attribute *attr,
383                                   char *buf)
384 {
385         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
386 }
387 static ssize_t pages_to_scan_store(struct kobject *kobj,
388                                    struct kobj_attribute *attr,
389                                    const char *buf, size_t count)
390 {
391         int err;
392         unsigned long pages;
393
394         err = strict_strtoul(buf, 10, &pages);
395         if (err || !pages || pages > UINT_MAX)
396                 return -EINVAL;
397
398         khugepaged_pages_to_scan = pages;
399
400         return count;
401 }
402 static struct kobj_attribute pages_to_scan_attr =
403         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
404                pages_to_scan_store);
405
406 static ssize_t pages_collapsed_show(struct kobject *kobj,
407                                     struct kobj_attribute *attr,
408                                     char *buf)
409 {
410         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
411 }
412 static struct kobj_attribute pages_collapsed_attr =
413         __ATTR_RO(pages_collapsed);
414
415 static ssize_t full_scans_show(struct kobject *kobj,
416                                struct kobj_attribute *attr,
417                                char *buf)
418 {
419         return sprintf(buf, "%u\n", khugepaged_full_scans);
420 }
421 static struct kobj_attribute full_scans_attr =
422         __ATTR_RO(full_scans);
423
424 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
425                                       struct kobj_attribute *attr, char *buf)
426 {
427         return single_flag_show(kobj, attr, buf,
428                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
429 }
430 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
431                                        struct kobj_attribute *attr,
432                                        const char *buf, size_t count)
433 {
434         return single_flag_store(kobj, attr, buf, count,
435                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
436 }
437 static struct kobj_attribute khugepaged_defrag_attr =
438         __ATTR(defrag, 0644, khugepaged_defrag_show,
439                khugepaged_defrag_store);
440
441 /*
442  * max_ptes_none controls if khugepaged should collapse hugepages over
443  * any unmapped ptes in turn potentially increasing the memory
444  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
445  * reduce the available free memory in the system as it
446  * runs. Increasing max_ptes_none will instead potentially reduce the
447  * free memory in the system during the khugepaged scan.
448  */
449 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
450                                              struct kobj_attribute *attr,
451                                              char *buf)
452 {
453         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
454 }
455 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
456                                               struct kobj_attribute *attr,
457                                               const char *buf, size_t count)
458 {
459         int err;
460         unsigned long max_ptes_none;
461
462         err = strict_strtoul(buf, 10, &max_ptes_none);
463         if (err || max_ptes_none > HPAGE_PMD_NR-1)
464                 return -EINVAL;
465
466         khugepaged_max_ptes_none = max_ptes_none;
467
468         return count;
469 }
470 static struct kobj_attribute khugepaged_max_ptes_none_attr =
471         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
472                khugepaged_max_ptes_none_store);
473
474 static struct attribute *khugepaged_attr[] = {
475         &khugepaged_defrag_attr.attr,
476         &khugepaged_max_ptes_none_attr.attr,
477         &pages_to_scan_attr.attr,
478         &pages_collapsed_attr.attr,
479         &full_scans_attr.attr,
480         &scan_sleep_millisecs_attr.attr,
481         &alloc_sleep_millisecs_attr.attr,
482         NULL,
483 };
484
485 static struct attribute_group khugepaged_attr_group = {
486         .attrs = khugepaged_attr,
487         .name = "khugepaged",
488 };
489 #endif /* CONFIG_SYSFS */
490
491 static int __init hugepage_init(void)
492 {
493         int err;
494 #ifdef CONFIG_SYSFS
495         static struct kobject *hugepage_kobj;
496 #endif
497
498         err = -EINVAL;
499         if (!has_transparent_hugepage()) {
500                 transparent_hugepage_flags = 0;
501                 goto out;
502         }
503
504 #ifdef CONFIG_SYSFS
505         err = -ENOMEM;
506         hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
507         if (unlikely(!hugepage_kobj)) {
508                 printk(KERN_ERR "hugepage: failed kobject create\n");
509                 goto out;
510         }
511
512         err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
513         if (err) {
514                 printk(KERN_ERR "hugepage: failed register hugeage group\n");
515                 goto out;
516         }
517
518         err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
519         if (err) {
520                 printk(KERN_ERR "hugepage: failed register hugeage group\n");
521                 goto out;
522         }
523 #endif
524
525         err = khugepaged_slab_init();
526         if (err)
527                 goto out;
528
529         err = mm_slots_hash_init();
530         if (err) {
531                 khugepaged_slab_free();
532                 goto out;
533         }
534
535         /*
536          * By default disable transparent hugepages on smaller systems,
537          * where the extra memory used could hurt more than TLB overhead
538          * is likely to save.  The admin can still enable it through /sys.
539          */
540         if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
541                 transparent_hugepage_flags = 0;
542
543         start_khugepaged();
544
545         set_recommended_min_free_kbytes();
546
547 out:
548         return err;
549 }
550 module_init(hugepage_init)
551
552 static int __init setup_transparent_hugepage(char *str)
553 {
554         int ret = 0;
555         if (!str)
556                 goto out;
557         if (!strcmp(str, "always")) {
558                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
559                         &transparent_hugepage_flags);
560                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
561                           &transparent_hugepage_flags);
562                 ret = 1;
563         } else if (!strcmp(str, "madvise")) {
564                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
565                           &transparent_hugepage_flags);
566                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
567                         &transparent_hugepage_flags);
568                 ret = 1;
569         } else if (!strcmp(str, "never")) {
570                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
571                           &transparent_hugepage_flags);
572                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
573                           &transparent_hugepage_flags);
574                 ret = 1;
575         }
576 out:
577         if (!ret)
578                 printk(KERN_WARNING
579                        "transparent_hugepage= cannot parse, ignored\n");
580         return ret;
581 }
582 __setup("transparent_hugepage=", setup_transparent_hugepage);
583
584 static void prepare_pmd_huge_pte(pgtable_t pgtable,
585                                  struct mm_struct *mm)
586 {
587         assert_spin_locked(&mm->page_table_lock);
588
589         /* FIFO */
590         if (!mm->pmd_huge_pte)
591                 INIT_LIST_HEAD(&pgtable->lru);
592         else
593                 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
594         mm->pmd_huge_pte = pgtable;
595 }
596
597 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
598 {
599         if (likely(vma->vm_flags & VM_WRITE))
600                 pmd = pmd_mkwrite(pmd);
601         return pmd;
602 }
603
604 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
605                                         struct vm_area_struct *vma,
606                                         unsigned long haddr, pmd_t *pmd,
607                                         struct page *page)
608 {
609         int ret = 0;
610         pgtable_t pgtable;
611
612         VM_BUG_ON(!PageCompound(page));
613         pgtable = pte_alloc_one(mm, haddr);
614         if (unlikely(!pgtable)) {
615                 mem_cgroup_uncharge_page(page);
616                 put_page(page);
617                 return VM_FAULT_OOM;
618         }
619
620         clear_huge_page(page, haddr, HPAGE_PMD_NR);
621         __SetPageUptodate(page);
622
623         spin_lock(&mm->page_table_lock);
624         if (unlikely(!pmd_none(*pmd))) {
625                 spin_unlock(&mm->page_table_lock);
626                 mem_cgroup_uncharge_page(page);
627                 put_page(page);
628                 pte_free(mm, pgtable);
629         } else {
630                 pmd_t entry;
631                 entry = mk_pmd(page, vma->vm_page_prot);
632                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
633                 entry = pmd_mkhuge(entry);
634                 /*
635                  * The spinlocking to take the lru_lock inside
636                  * page_add_new_anon_rmap() acts as a full memory
637                  * barrier to be sure clear_huge_page writes become
638                  * visible after the set_pmd_at() write.
639                  */
640                 page_add_new_anon_rmap(page, vma, haddr);
641                 set_pmd_at(mm, haddr, pmd, entry);
642                 prepare_pmd_huge_pte(pgtable, mm);
643                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
644                 spin_unlock(&mm->page_table_lock);
645         }
646
647         return ret;
648 }
649
650 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
651 {
652         return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
653 }
654
655 static inline struct page *alloc_hugepage_vma(int defrag,
656                                               struct vm_area_struct *vma,
657                                               unsigned long haddr, int nd,
658                                               gfp_t extra_gfp)
659 {
660         return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
661                                HPAGE_PMD_ORDER, vma, haddr, nd);
662 }
663
664 #ifndef CONFIG_NUMA
665 static inline struct page *alloc_hugepage(int defrag)
666 {
667         return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
668                            HPAGE_PMD_ORDER);
669 }
670 #endif
671
672 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
673                                unsigned long address, pmd_t *pmd,
674                                unsigned int flags)
675 {
676         struct page *page;
677         unsigned long haddr = address & HPAGE_PMD_MASK;
678         pte_t *pte;
679
680         if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
681                 if (unlikely(anon_vma_prepare(vma)))
682                         return VM_FAULT_OOM;
683                 if (unlikely(khugepaged_enter(vma)))
684                         return VM_FAULT_OOM;
685                 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
686                                           vma, haddr, numa_node_id(), 0);
687                 if (unlikely(!page)) {
688                         count_vm_event(THP_FAULT_FALLBACK);
689                         goto out;
690                 }
691                 count_vm_event(THP_FAULT_ALLOC);
692                 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
693                         put_page(page);
694                         goto out;
695                 }
696
697                 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
698         }
699 out:
700         /*
701          * Use __pte_alloc instead of pte_alloc_map, because we can't
702          * run pte_offset_map on the pmd, if an huge pmd could
703          * materialize from under us from a different thread.
704          */
705         if (unlikely(__pte_alloc(mm, vma, pmd, address)))
706                 return VM_FAULT_OOM;
707         /* if an huge pmd materialized from under us just retry later */
708         if (unlikely(pmd_trans_huge(*pmd)))
709                 return 0;
710         /*
711          * A regular pmd is established and it can't morph into a huge pmd
712          * from under us anymore at this point because we hold the mmap_sem
713          * read mode and khugepaged takes it in write mode. So now it's
714          * safe to run pte_offset_map().
715          */
716         pte = pte_offset_map(pmd, address);
717         return handle_pte_fault(mm, vma, address, pte, pmd, flags);
718 }
719
720 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
721                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
722                   struct vm_area_struct *vma)
723 {
724         struct page *src_page;
725         pmd_t pmd;
726         pgtable_t pgtable;
727         int ret;
728
729         ret = -ENOMEM;
730         pgtable = pte_alloc_one(dst_mm, addr);
731         if (unlikely(!pgtable))
732                 goto out;
733
734         spin_lock(&dst_mm->page_table_lock);
735         spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
736
737         ret = -EAGAIN;
738         pmd = *src_pmd;
739         if (unlikely(!pmd_trans_huge(pmd))) {
740                 pte_free(dst_mm, pgtable);
741                 goto out_unlock;
742         }
743         if (unlikely(pmd_trans_splitting(pmd))) {
744                 /* split huge page running from under us */
745                 spin_unlock(&src_mm->page_table_lock);
746                 spin_unlock(&dst_mm->page_table_lock);
747                 pte_free(dst_mm, pgtable);
748
749                 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
750                 goto out;
751         }
752         src_page = pmd_page(pmd);
753         VM_BUG_ON(!PageHead(src_page));
754         get_page(src_page);
755         page_dup_rmap(src_page);
756         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
757
758         pmdp_set_wrprotect(src_mm, addr, src_pmd);
759         pmd = pmd_mkold(pmd_wrprotect(pmd));
760         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
761         prepare_pmd_huge_pte(pgtable, dst_mm);
762
763         ret = 0;
764 out_unlock:
765         spin_unlock(&src_mm->page_table_lock);
766         spin_unlock(&dst_mm->page_table_lock);
767 out:
768         return ret;
769 }
770
771 /* no "address" argument so destroys page coloring of some arch */
772 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
773 {
774         pgtable_t pgtable;
775
776         assert_spin_locked(&mm->page_table_lock);
777
778         /* FIFO */
779         pgtable = mm->pmd_huge_pte;
780         if (list_empty(&pgtable->lru))
781                 mm->pmd_huge_pte = NULL;
782         else {
783                 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
784                                               struct page, lru);
785                 list_del(&pgtable->lru);
786         }
787         return pgtable;
788 }
789
790 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
791                                         struct vm_area_struct *vma,
792                                         unsigned long address,
793                                         pmd_t *pmd, pmd_t orig_pmd,
794                                         struct page *page,
795                                         unsigned long haddr)
796 {
797         pgtable_t pgtable;
798         pmd_t _pmd;
799         int ret = 0, i;
800         struct page **pages;
801
802         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
803                         GFP_KERNEL);
804         if (unlikely(!pages)) {
805                 ret |= VM_FAULT_OOM;
806                 goto out;
807         }
808
809         for (i = 0; i < HPAGE_PMD_NR; i++) {
810                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
811                                                __GFP_OTHER_NODE,
812                                                vma, address, page_to_nid(page));
813                 if (unlikely(!pages[i] ||
814                              mem_cgroup_newpage_charge(pages[i], mm,
815                                                        GFP_KERNEL))) {
816                         if (pages[i])
817                                 put_page(pages[i]);
818                         mem_cgroup_uncharge_start();
819                         while (--i >= 0) {
820                                 mem_cgroup_uncharge_page(pages[i]);
821                                 put_page(pages[i]);
822                         }
823                         mem_cgroup_uncharge_end();
824                         kfree(pages);
825                         ret |= VM_FAULT_OOM;
826                         goto out;
827                 }
828         }
829
830         for (i = 0; i < HPAGE_PMD_NR; i++) {
831                 copy_user_highpage(pages[i], page + i,
832                                    haddr + PAGE_SHIFT*i, vma);
833                 __SetPageUptodate(pages[i]);
834                 cond_resched();
835         }
836
837         spin_lock(&mm->page_table_lock);
838         if (unlikely(!pmd_same(*pmd, orig_pmd)))
839                 goto out_free_pages;
840         VM_BUG_ON(!PageHead(page));
841
842         pmdp_clear_flush_notify(vma, haddr, pmd);
843         /* leave pmd empty until pte is filled */
844
845         pgtable = get_pmd_huge_pte(mm);
846         pmd_populate(mm, &_pmd, pgtable);
847
848         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
849                 pte_t *pte, entry;
850                 entry = mk_pte(pages[i], vma->vm_page_prot);
851                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
852                 page_add_new_anon_rmap(pages[i], vma, haddr);
853                 pte = pte_offset_map(&_pmd, haddr);
854                 VM_BUG_ON(!pte_none(*pte));
855                 set_pte_at(mm, haddr, pte, entry);
856                 pte_unmap(pte);
857         }
858         kfree(pages);
859
860         mm->nr_ptes++;
861         smp_wmb(); /* make pte visible before pmd */
862         pmd_populate(mm, pmd, pgtable);
863         page_remove_rmap(page);
864         spin_unlock(&mm->page_table_lock);
865
866         ret |= VM_FAULT_WRITE;
867         put_page(page);
868
869 out:
870         return ret;
871
872 out_free_pages:
873         spin_unlock(&mm->page_table_lock);
874         mem_cgroup_uncharge_start();
875         for (i = 0; i < HPAGE_PMD_NR; i++) {
876                 mem_cgroup_uncharge_page(pages[i]);
877                 put_page(pages[i]);
878         }
879         mem_cgroup_uncharge_end();
880         kfree(pages);
881         goto out;
882 }
883
884 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
885                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
886 {
887         int ret = 0;
888         struct page *page, *new_page;
889         unsigned long haddr;
890
891         VM_BUG_ON(!vma->anon_vma);
892         spin_lock(&mm->page_table_lock);
893         if (unlikely(!pmd_same(*pmd, orig_pmd)))
894                 goto out_unlock;
895
896         page = pmd_page(orig_pmd);
897         VM_BUG_ON(!PageCompound(page) || !PageHead(page));
898         haddr = address & HPAGE_PMD_MASK;
899         if (page_mapcount(page) == 1) {
900                 pmd_t entry;
901                 entry = pmd_mkyoung(orig_pmd);
902                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
903                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
904                         update_mmu_cache(vma, address, entry);
905                 ret |= VM_FAULT_WRITE;
906                 goto out_unlock;
907         }
908         get_page(page);
909         spin_unlock(&mm->page_table_lock);
910
911         if (transparent_hugepage_enabled(vma) &&
912             !transparent_hugepage_debug_cow())
913                 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
914                                               vma, haddr, numa_node_id(), 0);
915         else
916                 new_page = NULL;
917
918         if (unlikely(!new_page)) {
919                 count_vm_event(THP_FAULT_FALLBACK);
920                 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
921                                                    pmd, orig_pmd, page, haddr);
922                 put_page(page);
923                 goto out;
924         }
925         count_vm_event(THP_FAULT_ALLOC);
926
927         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
928                 put_page(new_page);
929                 put_page(page);
930                 ret |= VM_FAULT_OOM;
931                 goto out;
932         }
933
934         copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
935         __SetPageUptodate(new_page);
936
937         spin_lock(&mm->page_table_lock);
938         put_page(page);
939         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
940                 mem_cgroup_uncharge_page(new_page);
941                 put_page(new_page);
942         } else {
943                 pmd_t entry;
944                 VM_BUG_ON(!PageHead(page));
945                 entry = mk_pmd(new_page, vma->vm_page_prot);
946                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
947                 entry = pmd_mkhuge(entry);
948                 pmdp_clear_flush_notify(vma, haddr, pmd);
949                 page_add_new_anon_rmap(new_page, vma, haddr);
950                 set_pmd_at(mm, haddr, pmd, entry);
951                 update_mmu_cache(vma, address, entry);
952                 page_remove_rmap(page);
953                 put_page(page);
954                 ret |= VM_FAULT_WRITE;
955         }
956 out_unlock:
957         spin_unlock(&mm->page_table_lock);
958 out:
959         return ret;
960 }
961
962 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
963                                    unsigned long addr,
964                                    pmd_t *pmd,
965                                    unsigned int flags)
966 {
967         struct page *page = NULL;
968
969         assert_spin_locked(&mm->page_table_lock);
970
971         if (flags & FOLL_WRITE && !pmd_write(*pmd))
972                 goto out;
973
974         page = pmd_page(*pmd);
975         VM_BUG_ON(!PageHead(page));
976         if (flags & FOLL_TOUCH) {
977                 pmd_t _pmd;
978                 /*
979                  * We should set the dirty bit only for FOLL_WRITE but
980                  * for now the dirty bit in the pmd is meaningless.
981                  * And if the dirty bit will become meaningful and
982                  * we'll only set it with FOLL_WRITE, an atomic
983                  * set_bit will be required on the pmd to set the
984                  * young bit, instead of the current set_pmd_at.
985                  */
986                 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
987                 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
988         }
989         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
990         VM_BUG_ON(!PageCompound(page));
991         if (flags & FOLL_GET)
992                 get_page(page);
993
994 out:
995         return page;
996 }
997
998 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
999                  pmd_t *pmd)
1000 {
1001         int ret = 0;
1002
1003         spin_lock(&tlb->mm->page_table_lock);
1004         if (likely(pmd_trans_huge(*pmd))) {
1005                 if (unlikely(pmd_trans_splitting(*pmd))) {
1006                         spin_unlock(&tlb->mm->page_table_lock);
1007                         wait_split_huge_page(vma->anon_vma,
1008                                              pmd);
1009                 } else {
1010                         struct page *page;
1011                         pgtable_t pgtable;
1012                         pgtable = get_pmd_huge_pte(tlb->mm);
1013                         page = pmd_page(*pmd);
1014                         pmd_clear(pmd);
1015                         page_remove_rmap(page);
1016                         VM_BUG_ON(page_mapcount(page) < 0);
1017                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1018                         VM_BUG_ON(!PageHead(page));
1019                         spin_unlock(&tlb->mm->page_table_lock);
1020                         tlb_remove_page(tlb, page);
1021                         pte_free(tlb->mm, pgtable);
1022                         ret = 1;
1023                 }
1024         } else
1025                 spin_unlock(&tlb->mm->page_table_lock);
1026
1027         return ret;
1028 }
1029
1030 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1031                 unsigned long addr, unsigned long end,
1032                 unsigned char *vec)
1033 {
1034         int ret = 0;
1035
1036         spin_lock(&vma->vm_mm->page_table_lock);
1037         if (likely(pmd_trans_huge(*pmd))) {
1038                 ret = !pmd_trans_splitting(*pmd);
1039                 spin_unlock(&vma->vm_mm->page_table_lock);
1040                 if (unlikely(!ret))
1041                         wait_split_huge_page(vma->anon_vma, pmd);
1042                 else {
1043                         /*
1044                          * All logical pages in the range are present
1045                          * if backed by a huge page.
1046                          */
1047                         memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1048                 }
1049         } else
1050                 spin_unlock(&vma->vm_mm->page_table_lock);
1051
1052         return ret;
1053 }
1054
1055 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1056                 unsigned long addr, pgprot_t newprot)
1057 {
1058         struct mm_struct *mm = vma->vm_mm;
1059         int ret = 0;
1060
1061         spin_lock(&mm->page_table_lock);
1062         if (likely(pmd_trans_huge(*pmd))) {
1063                 if (unlikely(pmd_trans_splitting(*pmd))) {
1064                         spin_unlock(&mm->page_table_lock);
1065                         wait_split_huge_page(vma->anon_vma, pmd);
1066                 } else {
1067                         pmd_t entry;
1068
1069                         entry = pmdp_get_and_clear(mm, addr, pmd);
1070                         entry = pmd_modify(entry, newprot);
1071                         set_pmd_at(mm, addr, pmd, entry);
1072                         spin_unlock(&vma->vm_mm->page_table_lock);
1073                         flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1074                         ret = 1;
1075                 }
1076         } else
1077                 spin_unlock(&vma->vm_mm->page_table_lock);
1078
1079         return ret;
1080 }
1081
1082 pmd_t *page_check_address_pmd(struct page *page,
1083                               struct mm_struct *mm,
1084                               unsigned long address,
1085                               enum page_check_address_pmd_flag flag)
1086 {
1087         pgd_t *pgd;
1088         pud_t *pud;
1089         pmd_t *pmd, *ret = NULL;
1090
1091         if (address & ~HPAGE_PMD_MASK)
1092                 goto out;
1093
1094         pgd = pgd_offset(mm, address);
1095         if (!pgd_present(*pgd))
1096                 goto out;
1097
1098         pud = pud_offset(pgd, address);
1099         if (!pud_present(*pud))
1100                 goto out;
1101
1102         pmd = pmd_offset(pud, address);
1103         if (pmd_none(*pmd))
1104                 goto out;
1105         if (pmd_page(*pmd) != page)
1106                 goto out;
1107         /*
1108          * split_vma() may create temporary aliased mappings. There is
1109          * no risk as long as all huge pmd are found and have their
1110          * splitting bit set before __split_huge_page_refcount
1111          * runs. Finding the same huge pmd more than once during the
1112          * same rmap walk is not a problem.
1113          */
1114         if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1115             pmd_trans_splitting(*pmd))
1116                 goto out;
1117         if (pmd_trans_huge(*pmd)) {
1118                 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1119                           !pmd_trans_splitting(*pmd));
1120                 ret = pmd;
1121         }
1122 out:
1123         return ret;
1124 }
1125
1126 static int __split_huge_page_splitting(struct page *page,
1127                                        struct vm_area_struct *vma,
1128                                        unsigned long address)
1129 {
1130         struct mm_struct *mm = vma->vm_mm;
1131         pmd_t *pmd;
1132         int ret = 0;
1133
1134         spin_lock(&mm->page_table_lock);
1135         pmd = page_check_address_pmd(page, mm, address,
1136                                      PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1137         if (pmd) {
1138                 /*
1139                  * We can't temporarily set the pmd to null in order
1140                  * to split it, the pmd must remain marked huge at all
1141                  * times or the VM won't take the pmd_trans_huge paths
1142                  * and it won't wait on the anon_vma->root->mutex to
1143                  * serialize against split_huge_page*.
1144                  */
1145                 pmdp_splitting_flush_notify(vma, address, pmd);
1146                 ret = 1;
1147         }
1148         spin_unlock(&mm->page_table_lock);
1149
1150         return ret;
1151 }
1152
1153 static void __split_huge_page_refcount(struct page *page)
1154 {
1155         int i;
1156         unsigned long head_index = page->index;
1157         struct zone *zone = page_zone(page);
1158         int zonestat;
1159
1160         /* prevent PageLRU to go away from under us, and freeze lru stats */
1161         spin_lock_irq(&zone->lru_lock);
1162         compound_lock(page);
1163
1164         for (i = 1; i < HPAGE_PMD_NR; i++) {
1165                 struct page *page_tail = page + i;
1166
1167                 /* tail_page->_count cannot change */
1168                 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1169                 BUG_ON(page_count(page) <= 0);
1170                 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1171                 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1172
1173                 /* after clearing PageTail the gup refcount can be released */
1174                 smp_mb();
1175
1176                 /*
1177                  * retain hwpoison flag of the poisoned tail page:
1178                  *   fix for the unsuitable process killed on Guest Machine(KVM)
1179                  *   by the memory-failure.
1180                  */
1181                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1182                 page_tail->flags |= (page->flags &
1183                                      ((1L << PG_referenced) |
1184                                       (1L << PG_swapbacked) |
1185                                       (1L << PG_mlocked) |
1186                                       (1L << PG_uptodate)));
1187                 page_tail->flags |= (1L << PG_dirty);
1188
1189                 /*
1190                  * 1) clear PageTail before overwriting first_page
1191                  * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1192                  */
1193                 smp_wmb();
1194
1195                 /*
1196                  * __split_huge_page_splitting() already set the
1197                  * splitting bit in all pmd that could map this
1198                  * hugepage, that will ensure no CPU can alter the
1199                  * mapcount on the head page. The mapcount is only
1200                  * accounted in the head page and it has to be
1201                  * transferred to all tail pages in the below code. So
1202                  * for this code to be safe, the split the mapcount
1203                  * can't change. But that doesn't mean userland can't
1204                  * keep changing and reading the page contents while
1205                  * we transfer the mapcount, so the pmd splitting
1206                  * status is achieved setting a reserved bit in the
1207                  * pmd, not by clearing the present bit.
1208                 */
1209                 BUG_ON(page_mapcount(page_tail));
1210                 page_tail->_mapcount = page->_mapcount;
1211
1212                 BUG_ON(page_tail->mapping);
1213                 page_tail->mapping = page->mapping;
1214
1215                 page_tail->index = ++head_index;
1216
1217                 BUG_ON(!PageAnon(page_tail));
1218                 BUG_ON(!PageUptodate(page_tail));
1219                 BUG_ON(!PageDirty(page_tail));
1220                 BUG_ON(!PageSwapBacked(page_tail));
1221
1222                 mem_cgroup_split_huge_fixup(page, page_tail);
1223
1224                 lru_add_page_tail(zone, page, page_tail);
1225         }
1226
1227         __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1228         __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1229
1230         /*
1231          * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1232          * so adjust those appropriately if this page is on the LRU.
1233          */
1234         if (PageLRU(page)) {
1235                 zonestat = NR_LRU_BASE + page_lru(page);
1236                 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1237         }
1238
1239         ClearPageCompound(page);
1240         compound_unlock(page);
1241         spin_unlock_irq(&zone->lru_lock);
1242
1243         for (i = 1; i < HPAGE_PMD_NR; i++) {
1244                 struct page *page_tail = page + i;
1245                 BUG_ON(page_count(page_tail) <= 0);
1246                 /*
1247                  * Tail pages may be freed if there wasn't any mapping
1248                  * like if add_to_swap() is running on a lru page that
1249                  * had its mapping zapped. And freeing these pages
1250                  * requires taking the lru_lock so we do the put_page
1251                  * of the tail pages after the split is complete.
1252                  */
1253                 put_page(page_tail);
1254         }
1255
1256         /*
1257          * Only the head page (now become a regular page) is required
1258          * to be pinned by the caller.
1259          */
1260         BUG_ON(page_count(page) <= 0);
1261 }
1262
1263 static int __split_huge_page_map(struct page *page,
1264                                  struct vm_area_struct *vma,
1265                                  unsigned long address)
1266 {
1267         struct mm_struct *mm = vma->vm_mm;
1268         pmd_t *pmd, _pmd;
1269         int ret = 0, i;
1270         pgtable_t pgtable;
1271         unsigned long haddr;
1272
1273         spin_lock(&mm->page_table_lock);
1274         pmd = page_check_address_pmd(page, mm, address,
1275                                      PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1276         if (pmd) {
1277                 pgtable = get_pmd_huge_pte(mm);
1278                 pmd_populate(mm, &_pmd, pgtable);
1279
1280                 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1281                      i++, haddr += PAGE_SIZE) {
1282                         pte_t *pte, entry;
1283                         BUG_ON(PageCompound(page+i));
1284                         entry = mk_pte(page + i, vma->vm_page_prot);
1285                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1286                         if (!pmd_write(*pmd))
1287                                 entry = pte_wrprotect(entry);
1288                         else
1289                                 BUG_ON(page_mapcount(page) != 1);
1290                         if (!pmd_young(*pmd))
1291                                 entry = pte_mkold(entry);
1292                         pte = pte_offset_map(&_pmd, haddr);
1293                         BUG_ON(!pte_none(*pte));
1294                         set_pte_at(mm, haddr, pte, entry);
1295                         pte_unmap(pte);
1296                 }
1297
1298                 mm->nr_ptes++;
1299                 smp_wmb(); /* make pte visible before pmd */
1300                 /*
1301                  * Up to this point the pmd is present and huge and
1302                  * userland has the whole access to the hugepage
1303                  * during the split (which happens in place). If we
1304                  * overwrite the pmd with the not-huge version
1305                  * pointing to the pte here (which of course we could
1306                  * if all CPUs were bug free), userland could trigger
1307                  * a small page size TLB miss on the small sized TLB
1308                  * while the hugepage TLB entry is still established
1309                  * in the huge TLB. Some CPU doesn't like that. See
1310                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1311                  * Erratum 383 on page 93. Intel should be safe but is
1312                  * also warns that it's only safe if the permission
1313                  * and cache attributes of the two entries loaded in
1314                  * the two TLB is identical (which should be the case
1315                  * here). But it is generally safer to never allow
1316                  * small and huge TLB entries for the same virtual
1317                  * address to be loaded simultaneously. So instead of
1318                  * doing "pmd_populate(); flush_tlb_range();" we first
1319                  * mark the current pmd notpresent (atomically because
1320                  * here the pmd_trans_huge and pmd_trans_splitting
1321                  * must remain set at all times on the pmd until the
1322                  * split is complete for this pmd), then we flush the
1323                  * SMP TLB and finally we write the non-huge version
1324                  * of the pmd entry with pmd_populate.
1325                  */
1326                 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1327                 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1328                 pmd_populate(mm, pmd, pgtable);
1329                 ret = 1;
1330         }
1331         spin_unlock(&mm->page_table_lock);
1332
1333         return ret;
1334 }
1335
1336 /* must be called with anon_vma->root->mutex hold */
1337 static void __split_huge_page(struct page *page,
1338                               struct anon_vma *anon_vma)
1339 {
1340         int mapcount, mapcount2;
1341         struct anon_vma_chain *avc;
1342
1343         BUG_ON(!PageHead(page));
1344         BUG_ON(PageTail(page));
1345
1346         mapcount = 0;
1347         list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1348                 struct vm_area_struct *vma = avc->vma;
1349                 unsigned long addr = vma_address(page, vma);
1350                 BUG_ON(is_vma_temporary_stack(vma));
1351                 if (addr == -EFAULT)
1352                         continue;
1353                 mapcount += __split_huge_page_splitting(page, vma, addr);
1354         }
1355         /*
1356          * It is critical that new vmas are added to the tail of the
1357          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1358          * and establishes a child pmd before
1359          * __split_huge_page_splitting() freezes the parent pmd (so if
1360          * we fail to prevent copy_huge_pmd() from running until the
1361          * whole __split_huge_page() is complete), we will still see
1362          * the newly established pmd of the child later during the
1363          * walk, to be able to set it as pmd_trans_splitting too.
1364          */
1365         if (mapcount != page_mapcount(page))
1366                 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1367                        mapcount, page_mapcount(page));
1368         BUG_ON(mapcount != page_mapcount(page));
1369
1370         __split_huge_page_refcount(page);
1371
1372         mapcount2 = 0;
1373         list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1374                 struct vm_area_struct *vma = avc->vma;
1375                 unsigned long addr = vma_address(page, vma);
1376                 BUG_ON(is_vma_temporary_stack(vma));
1377                 if (addr == -EFAULT)
1378                         continue;
1379                 mapcount2 += __split_huge_page_map(page, vma, addr);
1380         }
1381         if (mapcount != mapcount2)
1382                 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1383                        mapcount, mapcount2, page_mapcount(page));
1384         BUG_ON(mapcount != mapcount2);
1385 }
1386
1387 int split_huge_page(struct page *page)
1388 {
1389         struct anon_vma *anon_vma;
1390         int ret = 1;
1391
1392         BUG_ON(!PageAnon(page));
1393         anon_vma = page_lock_anon_vma(page);
1394         if (!anon_vma)
1395                 goto out;
1396         ret = 0;
1397         if (!PageCompound(page))
1398                 goto out_unlock;
1399
1400         BUG_ON(!PageSwapBacked(page));
1401         __split_huge_page(page, anon_vma);
1402         count_vm_event(THP_SPLIT);
1403
1404         BUG_ON(PageCompound(page));
1405 out_unlock:
1406         page_unlock_anon_vma(anon_vma);
1407 out:
1408         return ret;
1409 }
1410
1411 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1412                    VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1413
1414 int hugepage_madvise(struct vm_area_struct *vma,
1415                      unsigned long *vm_flags, int advice)
1416 {
1417         switch (advice) {
1418         case MADV_HUGEPAGE:
1419                 /*
1420                  * Be somewhat over-protective like KSM for now!
1421                  */
1422                 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1423                         return -EINVAL;
1424                 *vm_flags &= ~VM_NOHUGEPAGE;
1425                 *vm_flags |= VM_HUGEPAGE;
1426                 /*
1427                  * If the vma become good for khugepaged to scan,
1428                  * register it here without waiting a page fault that
1429                  * may not happen any time soon.
1430                  */
1431                 if (unlikely(khugepaged_enter_vma_merge(vma)))
1432                         return -ENOMEM;
1433                 break;
1434         case MADV_NOHUGEPAGE:
1435                 /*
1436                  * Be somewhat over-protective like KSM for now!
1437                  */
1438                 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1439                         return -EINVAL;
1440                 *vm_flags &= ~VM_HUGEPAGE;
1441                 *vm_flags |= VM_NOHUGEPAGE;
1442                 /*
1443                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1444                  * this vma even if we leave the mm registered in khugepaged if
1445                  * it got registered before VM_NOHUGEPAGE was set.
1446                  */
1447                 break;
1448         }
1449
1450         return 0;
1451 }
1452
1453 static int __init khugepaged_slab_init(void)
1454 {
1455         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1456                                           sizeof(struct mm_slot),
1457                                           __alignof__(struct mm_slot), 0, NULL);
1458         if (!mm_slot_cache)
1459                 return -ENOMEM;
1460
1461         return 0;
1462 }
1463
1464 static void __init khugepaged_slab_free(void)
1465 {
1466         kmem_cache_destroy(mm_slot_cache);
1467         mm_slot_cache = NULL;
1468 }
1469
1470 static inline struct mm_slot *alloc_mm_slot(void)
1471 {
1472         if (!mm_slot_cache)     /* initialization failed */
1473                 return NULL;
1474         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1475 }
1476
1477 static inline void free_mm_slot(struct mm_slot *mm_slot)
1478 {
1479         kmem_cache_free(mm_slot_cache, mm_slot);
1480 }
1481
1482 static int __init mm_slots_hash_init(void)
1483 {
1484         mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1485                                 GFP_KERNEL);
1486         if (!mm_slots_hash)
1487                 return -ENOMEM;
1488         return 0;
1489 }
1490
1491 #if 0
1492 static void __init mm_slots_hash_free(void)
1493 {
1494         kfree(mm_slots_hash);
1495         mm_slots_hash = NULL;
1496 }
1497 #endif
1498
1499 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1500 {
1501         struct mm_slot *mm_slot;
1502         struct hlist_head *bucket;
1503         struct hlist_node *node;
1504
1505         bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1506                                 % MM_SLOTS_HASH_HEADS];
1507         hlist_for_each_entry(mm_slot, node, bucket, hash) {
1508                 if (mm == mm_slot->mm)
1509                         return mm_slot;
1510         }
1511         return NULL;
1512 }
1513
1514 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1515                                     struct mm_slot *mm_slot)
1516 {
1517         struct hlist_head *bucket;
1518
1519         bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1520                                 % MM_SLOTS_HASH_HEADS];
1521         mm_slot->mm = mm;
1522         hlist_add_head(&mm_slot->hash, bucket);
1523 }
1524
1525 static inline int khugepaged_test_exit(struct mm_struct *mm)
1526 {
1527         return atomic_read(&mm->mm_users) == 0;
1528 }
1529
1530 int __khugepaged_enter(struct mm_struct *mm)
1531 {
1532         struct mm_slot *mm_slot;
1533         int wakeup;
1534
1535         mm_slot = alloc_mm_slot();
1536         if (!mm_slot)
1537                 return -ENOMEM;
1538
1539         /* __khugepaged_exit() must not run from under us */
1540         VM_BUG_ON(khugepaged_test_exit(mm));
1541         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1542                 free_mm_slot(mm_slot);
1543                 return 0;
1544         }
1545
1546         spin_lock(&khugepaged_mm_lock);
1547         insert_to_mm_slots_hash(mm, mm_slot);
1548         /*
1549          * Insert just behind the scanning cursor, to let the area settle
1550          * down a little.
1551          */
1552         wakeup = list_empty(&khugepaged_scan.mm_head);
1553         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1554         spin_unlock(&khugepaged_mm_lock);
1555
1556         atomic_inc(&mm->mm_count);
1557         if (wakeup)
1558                 wake_up_interruptible(&khugepaged_wait);
1559
1560         return 0;
1561 }
1562
1563 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1564 {
1565         unsigned long hstart, hend;
1566         if (!vma->anon_vma)
1567                 /*
1568                  * Not yet faulted in so we will register later in the
1569                  * page fault if needed.
1570                  */
1571                 return 0;
1572         if (vma->vm_ops)
1573                 /* khugepaged not yet working on file or special mappings */
1574                 return 0;
1575         /*
1576          * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1577          * true too, verify it here.
1578          */
1579         VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1580         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1581         hend = vma->vm_end & HPAGE_PMD_MASK;
1582         if (hstart < hend)
1583                 return khugepaged_enter(vma);
1584         return 0;
1585 }
1586
1587 void __khugepaged_exit(struct mm_struct *mm)
1588 {
1589         struct mm_slot *mm_slot;
1590         int free = 0;
1591
1592         spin_lock(&khugepaged_mm_lock);
1593         mm_slot = get_mm_slot(mm);
1594         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1595                 hlist_del(&mm_slot->hash);
1596                 list_del(&mm_slot->mm_node);
1597                 free = 1;
1598         }
1599         spin_unlock(&khugepaged_mm_lock);
1600
1601         if (free) {
1602                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1603                 free_mm_slot(mm_slot);
1604                 mmdrop(mm);
1605         } else if (mm_slot) {
1606                 /*
1607                  * This is required to serialize against
1608                  * khugepaged_test_exit() (which is guaranteed to run
1609                  * under mmap sem read mode). Stop here (after we
1610                  * return all pagetables will be destroyed) until
1611                  * khugepaged has finished working on the pagetables
1612                  * under the mmap_sem.
1613                  */
1614                 down_write(&mm->mmap_sem);
1615                 up_write(&mm->mmap_sem);
1616         }
1617 }
1618
1619 static void release_pte_page(struct page *page)
1620 {
1621         /* 0 stands for page_is_file_cache(page) == false */
1622         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1623         unlock_page(page);
1624         putback_lru_page(page);
1625 }
1626
1627 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1628 {
1629         while (--_pte >= pte) {
1630                 pte_t pteval = *_pte;
1631                 if (!pte_none(pteval))
1632                         release_pte_page(pte_page(pteval));
1633         }
1634 }
1635
1636 static void release_all_pte_pages(pte_t *pte)
1637 {
1638         release_pte_pages(pte, pte + HPAGE_PMD_NR);
1639 }
1640
1641 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1642                                         unsigned long address,
1643                                         pte_t *pte)
1644 {
1645         struct page *page;
1646         pte_t *_pte;
1647         int referenced = 0, isolated = 0, none = 0;
1648         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1649              _pte++, address += PAGE_SIZE) {
1650                 pte_t pteval = *_pte;
1651                 if (pte_none(pteval)) {
1652                         if (++none <= khugepaged_max_ptes_none)
1653                                 continue;
1654                         else {
1655                                 release_pte_pages(pte, _pte);
1656                                 goto out;
1657                         }
1658                 }
1659                 if (!pte_present(pteval) || !pte_write(pteval)) {
1660                         release_pte_pages(pte, _pte);
1661                         goto out;
1662                 }
1663                 page = vm_normal_page(vma, address, pteval);
1664                 if (unlikely(!page)) {
1665                         release_pte_pages(pte, _pte);
1666                         goto out;
1667                 }
1668                 VM_BUG_ON(PageCompound(page));
1669                 BUG_ON(!PageAnon(page));
1670                 VM_BUG_ON(!PageSwapBacked(page));
1671
1672                 /* cannot use mapcount: can't collapse if there's a gup pin */
1673                 if (page_count(page) != 1) {
1674                         release_pte_pages(pte, _pte);
1675                         goto out;
1676                 }
1677                 /*
1678                  * We can do it before isolate_lru_page because the
1679                  * page can't be freed from under us. NOTE: PG_lock
1680                  * is needed to serialize against split_huge_page
1681                  * when invoked from the VM.
1682                  */
1683                 if (!trylock_page(page)) {
1684                         release_pte_pages(pte, _pte);
1685                         goto out;
1686                 }
1687                 /*
1688                  * Isolate the page to avoid collapsing an hugepage
1689                  * currently in use by the VM.
1690                  */
1691                 if (isolate_lru_page(page)) {
1692                         unlock_page(page);
1693                         release_pte_pages(pte, _pte);
1694                         goto out;
1695                 }
1696                 /* 0 stands for page_is_file_cache(page) == false */
1697                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1698                 VM_BUG_ON(!PageLocked(page));
1699                 VM_BUG_ON(PageLRU(page));
1700
1701                 /* If there is no mapped pte young don't collapse the page */
1702                 if (pte_young(pteval) || PageReferenced(page) ||
1703                     mmu_notifier_test_young(vma->vm_mm, address))
1704                         referenced = 1;
1705         }
1706         if (unlikely(!referenced))
1707                 release_all_pte_pages(pte);
1708         else
1709                 isolated = 1;
1710 out:
1711         return isolated;
1712 }
1713
1714 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1715                                       struct vm_area_struct *vma,
1716                                       unsigned long address,
1717                                       spinlock_t *ptl)
1718 {
1719         pte_t *_pte;
1720         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1721                 pte_t pteval = *_pte;
1722                 struct page *src_page;
1723
1724                 if (pte_none(pteval)) {
1725                         clear_user_highpage(page, address);
1726                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1727                 } else {
1728                         src_page = pte_page(pteval);
1729                         copy_user_highpage(page, src_page, address, vma);
1730                         VM_BUG_ON(page_mapcount(src_page) != 1);
1731                         VM_BUG_ON(page_count(src_page) != 2);
1732                         release_pte_page(src_page);
1733                         /*
1734                          * ptl mostly unnecessary, but preempt has to
1735                          * be disabled to update the per-cpu stats
1736                          * inside page_remove_rmap().
1737                          */
1738                         spin_lock(ptl);
1739                         /*
1740                          * paravirt calls inside pte_clear here are
1741                          * superfluous.
1742                          */
1743                         pte_clear(vma->vm_mm, address, _pte);
1744                         page_remove_rmap(src_page);
1745                         spin_unlock(ptl);
1746                         free_page_and_swap_cache(src_page);
1747                 }
1748
1749                 address += PAGE_SIZE;
1750                 page++;
1751         }
1752 }
1753
1754 static void collapse_huge_page(struct mm_struct *mm,
1755                                unsigned long address,
1756                                struct page **hpage,
1757                                struct vm_area_struct *vma,
1758                                int node)
1759 {
1760         pgd_t *pgd;
1761         pud_t *pud;
1762         pmd_t *pmd, _pmd;
1763         pte_t *pte;
1764         pgtable_t pgtable;
1765         struct page *new_page;
1766         spinlock_t *ptl;
1767         int isolated;
1768         unsigned long hstart, hend;
1769
1770         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1771 #ifndef CONFIG_NUMA
1772         up_read(&mm->mmap_sem);
1773         VM_BUG_ON(!*hpage);
1774         new_page = *hpage;
1775 #else
1776         VM_BUG_ON(*hpage);
1777         /*
1778          * Allocate the page while the vma is still valid and under
1779          * the mmap_sem read mode so there is no memory allocation
1780          * later when we take the mmap_sem in write mode. This is more
1781          * friendly behavior (OTOH it may actually hide bugs) to
1782          * filesystems in userland with daemons allocating memory in
1783          * the userland I/O paths.  Allocating memory with the
1784          * mmap_sem in read mode is good idea also to allow greater
1785          * scalability.
1786          */
1787         new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1788                                       node, __GFP_OTHER_NODE);
1789
1790         /*
1791          * After allocating the hugepage, release the mmap_sem read lock in
1792          * preparation for taking it in write mode.
1793          */
1794         up_read(&mm->mmap_sem);
1795         if (unlikely(!new_page)) {
1796                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1797                 *hpage = ERR_PTR(-ENOMEM);
1798                 return;
1799         }
1800 #endif
1801
1802         count_vm_event(THP_COLLAPSE_ALLOC);
1803         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1804 #ifdef CONFIG_NUMA
1805                 put_page(new_page);
1806 #endif
1807                 return;
1808         }
1809
1810         /*
1811          * Prevent all access to pagetables with the exception of
1812          * gup_fast later hanlded by the ptep_clear_flush and the VM
1813          * handled by the anon_vma lock + PG_lock.
1814          */
1815         down_write(&mm->mmap_sem);
1816         if (unlikely(khugepaged_test_exit(mm)))
1817                 goto out;
1818
1819         vma = find_vma(mm, address);
1820         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1821         hend = vma->vm_end & HPAGE_PMD_MASK;
1822         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1823                 goto out;
1824
1825         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1826             (vma->vm_flags & VM_NOHUGEPAGE))
1827                 goto out;
1828
1829         if (!vma->anon_vma || vma->vm_ops)
1830                 goto out;
1831         if (is_vma_temporary_stack(vma))
1832                 goto out;
1833         /*
1834          * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1835          * true too, verify it here.
1836          */
1837         VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1838
1839         pgd = pgd_offset(mm, address);
1840         if (!pgd_present(*pgd))
1841                 goto out;
1842
1843         pud = pud_offset(pgd, address);
1844         if (!pud_present(*pud))
1845                 goto out;
1846
1847         pmd = pmd_offset(pud, address);
1848         /* pmd can't go away or become huge under us */
1849         if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1850                 goto out;
1851
1852         anon_vma_lock(vma->anon_vma);
1853
1854         pte = pte_offset_map(pmd, address);
1855         ptl = pte_lockptr(mm, pmd);
1856
1857         spin_lock(&mm->page_table_lock); /* probably unnecessary */
1858         /*
1859          * After this gup_fast can't run anymore. This also removes
1860          * any huge TLB entry from the CPU so we won't allow
1861          * huge and small TLB entries for the same virtual address
1862          * to avoid the risk of CPU bugs in that area.
1863          */
1864         _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1865         spin_unlock(&mm->page_table_lock);
1866
1867         spin_lock(ptl);
1868         isolated = __collapse_huge_page_isolate(vma, address, pte);
1869         spin_unlock(ptl);
1870
1871         if (unlikely(!isolated)) {
1872                 pte_unmap(pte);
1873                 spin_lock(&mm->page_table_lock);
1874                 BUG_ON(!pmd_none(*pmd));
1875                 set_pmd_at(mm, address, pmd, _pmd);
1876                 spin_unlock(&mm->page_table_lock);
1877                 anon_vma_unlock(vma->anon_vma);
1878                 goto out;
1879         }
1880
1881         /*
1882          * All pages are isolated and locked so anon_vma rmap
1883          * can't run anymore.
1884          */
1885         anon_vma_unlock(vma->anon_vma);
1886
1887         __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1888         pte_unmap(pte);
1889         __SetPageUptodate(new_page);
1890         pgtable = pmd_pgtable(_pmd);
1891         VM_BUG_ON(page_count(pgtable) != 1);
1892         VM_BUG_ON(page_mapcount(pgtable) != 0);
1893
1894         _pmd = mk_pmd(new_page, vma->vm_page_prot);
1895         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1896         _pmd = pmd_mkhuge(_pmd);
1897
1898         /*
1899          * spin_lock() below is not the equivalent of smp_wmb(), so
1900          * this is needed to avoid the copy_huge_page writes to become
1901          * visible after the set_pmd_at() write.
1902          */
1903         smp_wmb();
1904
1905         spin_lock(&mm->page_table_lock);
1906         BUG_ON(!pmd_none(*pmd));
1907         page_add_new_anon_rmap(new_page, vma, address);
1908         set_pmd_at(mm, address, pmd, _pmd);
1909         update_mmu_cache(vma, address, entry);
1910         prepare_pmd_huge_pte(pgtable, mm);
1911         mm->nr_ptes--;
1912         spin_unlock(&mm->page_table_lock);
1913
1914 #ifndef CONFIG_NUMA
1915         *hpage = NULL;
1916 #endif
1917         khugepaged_pages_collapsed++;
1918 out_up_write:
1919         up_write(&mm->mmap_sem);
1920         return;
1921
1922 out:
1923         mem_cgroup_uncharge_page(new_page);
1924 #ifdef CONFIG_NUMA
1925         put_page(new_page);
1926 #endif
1927         goto out_up_write;
1928 }
1929
1930 static int khugepaged_scan_pmd(struct mm_struct *mm,
1931                                struct vm_area_struct *vma,
1932                                unsigned long address,
1933                                struct page **hpage)
1934 {
1935         pgd_t *pgd;
1936         pud_t *pud;
1937         pmd_t *pmd;
1938         pte_t *pte, *_pte;
1939         int ret = 0, referenced = 0, none = 0;
1940         struct page *page;
1941         unsigned long _address;
1942         spinlock_t *ptl;
1943         int node = -1;
1944
1945         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1946
1947         pgd = pgd_offset(mm, address);
1948         if (!pgd_present(*pgd))
1949                 goto out;
1950
1951         pud = pud_offset(pgd, address);
1952         if (!pud_present(*pud))
1953                 goto out;
1954
1955         pmd = pmd_offset(pud, address);
1956         if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1957                 goto out;
1958
1959         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1960         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1961              _pte++, _address += PAGE_SIZE) {
1962                 pte_t pteval = *_pte;
1963                 if (pte_none(pteval)) {
1964                         if (++none <= khugepaged_max_ptes_none)
1965                                 continue;
1966                         else
1967                                 goto out_unmap;
1968                 }
1969                 if (!pte_present(pteval) || !pte_write(pteval))
1970                         goto out_unmap;
1971                 page = vm_normal_page(vma, _address, pteval);
1972                 if (unlikely(!page))
1973                         goto out_unmap;
1974                 /*
1975                  * Chose the node of the first page. This could
1976                  * be more sophisticated and look at more pages,
1977                  * but isn't for now.
1978                  */
1979                 if (node == -1)
1980                         node = page_to_nid(page);
1981                 VM_BUG_ON(PageCompound(page));
1982                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1983                         goto out_unmap;
1984                 /* cannot use mapcount: can't collapse if there's a gup pin */
1985                 if (page_count(page) != 1)
1986                         goto out_unmap;
1987                 if (pte_young(pteval) || PageReferenced(page) ||
1988                     mmu_notifier_test_young(vma->vm_mm, address))
1989                         referenced = 1;
1990         }
1991         if (referenced)
1992                 ret = 1;
1993 out_unmap:
1994         pte_unmap_unlock(pte, ptl);
1995         if (ret)
1996                 /* collapse_huge_page will return with the mmap_sem released */
1997                 collapse_huge_page(mm, address, hpage, vma, node);
1998 out:
1999         return ret;
2000 }
2001
2002 static void collect_mm_slot(struct mm_slot *mm_slot)
2003 {
2004         struct mm_struct *mm = mm_slot->mm;
2005
2006         VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2007
2008         if (khugepaged_test_exit(mm)) {
2009                 /* free mm_slot */
2010                 hlist_del(&mm_slot->hash);
2011                 list_del(&mm_slot->mm_node);
2012
2013                 /*
2014                  * Not strictly needed because the mm exited already.
2015                  *
2016                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2017                  */
2018
2019                 /* khugepaged_mm_lock actually not necessary for the below */
2020                 free_mm_slot(mm_slot);
2021                 mmdrop(mm);
2022         }
2023 }
2024
2025 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2026                                             struct page **hpage)
2027 {
2028         struct mm_slot *mm_slot;
2029         struct mm_struct *mm;
2030         struct vm_area_struct *vma;
2031         int progress = 0;
2032
2033         VM_BUG_ON(!pages);
2034         VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2035
2036         if (khugepaged_scan.mm_slot)
2037                 mm_slot = khugepaged_scan.mm_slot;
2038         else {
2039                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2040                                      struct mm_slot, mm_node);
2041                 khugepaged_scan.address = 0;
2042                 khugepaged_scan.mm_slot = mm_slot;
2043         }
2044         spin_unlock(&khugepaged_mm_lock);
2045
2046         mm = mm_slot->mm;
2047         down_read(&mm->mmap_sem);
2048         if (unlikely(khugepaged_test_exit(mm)))
2049                 vma = NULL;
2050         else
2051                 vma = find_vma(mm, khugepaged_scan.address);
2052
2053         progress++;
2054         for (; vma; vma = vma->vm_next) {
2055                 unsigned long hstart, hend;
2056
2057                 cond_resched();
2058                 if (unlikely(khugepaged_test_exit(mm))) {
2059                         progress++;
2060                         break;
2061                 }
2062
2063                 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2064                      !khugepaged_always()) ||
2065                     (vma->vm_flags & VM_NOHUGEPAGE)) {
2066                 skip:
2067                         progress++;
2068                         continue;
2069                 }
2070                 if (!vma->anon_vma || vma->vm_ops)
2071                         goto skip;
2072                 if (is_vma_temporary_stack(vma))
2073                         goto skip;
2074                 /*
2075                  * If is_pfn_mapping() is true is_learn_pfn_mapping()
2076                  * must be true too, verify it here.
2077                  */
2078                 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2079                           vma->vm_flags & VM_NO_THP);
2080
2081                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2082                 hend = vma->vm_end & HPAGE_PMD_MASK;
2083                 if (hstart >= hend)
2084                         goto skip;
2085                 if (khugepaged_scan.address > hend)
2086                         goto skip;
2087                 if (khugepaged_scan.address < hstart)
2088                         khugepaged_scan.address = hstart;
2089                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2090
2091                 while (khugepaged_scan.address < hend) {
2092                         int ret;
2093                         cond_resched();
2094                         if (unlikely(khugepaged_test_exit(mm)))
2095                                 goto breakouterloop;
2096
2097                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2098                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2099                                   hend);
2100                         ret = khugepaged_scan_pmd(mm, vma,
2101                                                   khugepaged_scan.address,
2102                                                   hpage);
2103                         /* move to next address */
2104                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2105                         progress += HPAGE_PMD_NR;
2106                         if (ret)
2107                                 /* we released mmap_sem so break loop */
2108                                 goto breakouterloop_mmap_sem;
2109                         if (progress >= pages)
2110                                 goto breakouterloop;
2111                 }
2112         }
2113 breakouterloop:
2114         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2115 breakouterloop_mmap_sem:
2116
2117         spin_lock(&khugepaged_mm_lock);
2118         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2119         /*
2120          * Release the current mm_slot if this mm is about to die, or
2121          * if we scanned all vmas of this mm.
2122          */
2123         if (khugepaged_test_exit(mm) || !vma) {
2124                 /*
2125                  * Make sure that if mm_users is reaching zero while
2126                  * khugepaged runs here, khugepaged_exit will find
2127                  * mm_slot not pointing to the exiting mm.
2128                  */
2129                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2130                         khugepaged_scan.mm_slot = list_entry(
2131                                 mm_slot->mm_node.next,
2132                                 struct mm_slot, mm_node);
2133                         khugepaged_scan.address = 0;
2134                 } else {
2135                         khugepaged_scan.mm_slot = NULL;
2136                         khugepaged_full_scans++;
2137                 }
2138
2139                 collect_mm_slot(mm_slot);
2140         }
2141
2142         return progress;
2143 }
2144
2145 static int khugepaged_has_work(void)
2146 {
2147         return !list_empty(&khugepaged_scan.mm_head) &&
2148                 khugepaged_enabled();
2149 }
2150
2151 static int khugepaged_wait_event(void)
2152 {
2153         return !list_empty(&khugepaged_scan.mm_head) ||
2154                 !khugepaged_enabled();
2155 }
2156
2157 static void khugepaged_do_scan(struct page **hpage)
2158 {
2159         unsigned int progress = 0, pass_through_head = 0;
2160         unsigned int pages = khugepaged_pages_to_scan;
2161
2162         barrier(); /* write khugepaged_pages_to_scan to local stack */
2163
2164         while (progress < pages) {
2165                 cond_resched();
2166
2167 #ifndef CONFIG_NUMA
2168                 if (!*hpage) {
2169                         *hpage = alloc_hugepage(khugepaged_defrag());
2170                         if (unlikely(!*hpage)) {
2171                                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2172                                 break;
2173                         }
2174                         count_vm_event(THP_COLLAPSE_ALLOC);
2175                 }
2176 #else
2177                 if (IS_ERR(*hpage))
2178                         break;
2179 #endif
2180
2181                 if (unlikely(kthread_should_stop() || freezing(current)))
2182                         break;
2183
2184                 spin_lock(&khugepaged_mm_lock);
2185                 if (!khugepaged_scan.mm_slot)
2186                         pass_through_head++;
2187                 if (khugepaged_has_work() &&
2188                     pass_through_head < 2)
2189                         progress += khugepaged_scan_mm_slot(pages - progress,
2190                                                             hpage);
2191                 else
2192                         progress = pages;
2193                 spin_unlock(&khugepaged_mm_lock);
2194         }
2195 }
2196
2197 static void khugepaged_alloc_sleep(void)
2198 {
2199         DEFINE_WAIT(wait);
2200         add_wait_queue(&khugepaged_wait, &wait);
2201         schedule_timeout_interruptible(
2202                 msecs_to_jiffies(
2203                         khugepaged_alloc_sleep_millisecs));
2204         remove_wait_queue(&khugepaged_wait, &wait);
2205 }
2206
2207 #ifndef CONFIG_NUMA
2208 static struct page *khugepaged_alloc_hugepage(void)
2209 {
2210         struct page *hpage;
2211
2212         do {
2213                 hpage = alloc_hugepage(khugepaged_defrag());
2214                 if (!hpage) {
2215                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2216                         khugepaged_alloc_sleep();
2217                 } else
2218                         count_vm_event(THP_COLLAPSE_ALLOC);
2219         } while (unlikely(!hpage) &&
2220                  likely(khugepaged_enabled()));
2221         return hpage;
2222 }
2223 #endif
2224
2225 static void khugepaged_loop(void)
2226 {
2227         struct page *hpage;
2228
2229 #ifdef CONFIG_NUMA
2230         hpage = NULL;
2231 #endif
2232         while (likely(khugepaged_enabled())) {
2233 #ifndef CONFIG_NUMA
2234                 hpage = khugepaged_alloc_hugepage();
2235                 if (unlikely(!hpage))
2236                         break;
2237 #else
2238                 if (IS_ERR(hpage)) {
2239                         khugepaged_alloc_sleep();
2240                         hpage = NULL;
2241                 }
2242 #endif
2243
2244                 khugepaged_do_scan(&hpage);
2245 #ifndef CONFIG_NUMA
2246                 if (hpage)
2247                         put_page(hpage);
2248 #endif
2249                 try_to_freeze();
2250                 if (unlikely(kthread_should_stop()))
2251                         break;
2252                 if (khugepaged_has_work()) {
2253                         DEFINE_WAIT(wait);
2254                         if (!khugepaged_scan_sleep_millisecs)
2255                                 continue;
2256                         add_wait_queue(&khugepaged_wait, &wait);
2257                         schedule_timeout_interruptible(
2258                                 msecs_to_jiffies(
2259                                         khugepaged_scan_sleep_millisecs));
2260                         remove_wait_queue(&khugepaged_wait, &wait);
2261                 } else if (khugepaged_enabled())
2262                         wait_event_freezable(khugepaged_wait,
2263                                              khugepaged_wait_event());
2264         }
2265 }
2266
2267 static int khugepaged(void *none)
2268 {
2269         struct mm_slot *mm_slot;
2270
2271         set_freezable();
2272         set_user_nice(current, 19);
2273
2274         /* serialize with start_khugepaged() */
2275         mutex_lock(&khugepaged_mutex);
2276
2277         for (;;) {
2278                 mutex_unlock(&khugepaged_mutex);
2279                 VM_BUG_ON(khugepaged_thread != current);
2280                 khugepaged_loop();
2281                 VM_BUG_ON(khugepaged_thread != current);
2282
2283                 mutex_lock(&khugepaged_mutex);
2284                 if (!khugepaged_enabled())
2285                         break;
2286                 if (unlikely(kthread_should_stop()))
2287                         break;
2288         }
2289
2290         spin_lock(&khugepaged_mm_lock);
2291         mm_slot = khugepaged_scan.mm_slot;
2292         khugepaged_scan.mm_slot = NULL;
2293         if (mm_slot)
2294                 collect_mm_slot(mm_slot);
2295         spin_unlock(&khugepaged_mm_lock);
2296
2297         khugepaged_thread = NULL;
2298         mutex_unlock(&khugepaged_mutex);
2299
2300         return 0;
2301 }
2302
2303 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2304 {
2305         struct page *page;
2306
2307         spin_lock(&mm->page_table_lock);
2308         if (unlikely(!pmd_trans_huge(*pmd))) {
2309                 spin_unlock(&mm->page_table_lock);
2310                 return;
2311         }
2312         page = pmd_page(*pmd);
2313         VM_BUG_ON(!page_count(page));
2314         get_page(page);
2315         spin_unlock(&mm->page_table_lock);
2316
2317         split_huge_page(page);
2318
2319         put_page(page);
2320         BUG_ON(pmd_trans_huge(*pmd));
2321 }
2322
2323 static void split_huge_page_address(struct mm_struct *mm,
2324                                     unsigned long address)
2325 {
2326         pgd_t *pgd;
2327         pud_t *pud;
2328         pmd_t *pmd;
2329
2330         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2331
2332         pgd = pgd_offset(mm, address);
2333         if (!pgd_present(*pgd))
2334                 return;
2335
2336         pud = pud_offset(pgd, address);
2337         if (!pud_present(*pud))
2338                 return;
2339
2340         pmd = pmd_offset(pud, address);
2341         if (!pmd_present(*pmd))
2342                 return;
2343         /*
2344          * Caller holds the mmap_sem write mode, so a huge pmd cannot
2345          * materialize from under us.
2346          */
2347         split_huge_page_pmd(mm, pmd);
2348 }
2349
2350 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2351                              unsigned long start,
2352                              unsigned long end,
2353                              long adjust_next)
2354 {
2355         /*
2356          * If the new start address isn't hpage aligned and it could
2357          * previously contain an hugepage: check if we need to split
2358          * an huge pmd.
2359          */
2360         if (start & ~HPAGE_PMD_MASK &&
2361             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2362             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2363                 split_huge_page_address(vma->vm_mm, start);
2364
2365         /*
2366          * If the new end address isn't hpage aligned and it could
2367          * previously contain an hugepage: check if we need to split
2368          * an huge pmd.
2369          */
2370         if (end & ~HPAGE_PMD_MASK &&
2371             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2372             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2373                 split_huge_page_address(vma->vm_mm, end);
2374
2375         /*
2376          * If we're also updating the vma->vm_next->vm_start, if the new
2377          * vm_next->vm_start isn't page aligned and it could previously
2378          * contain an hugepage: check if we need to split an huge pmd.
2379          */
2380         if (adjust_next > 0) {
2381                 struct vm_area_struct *next = vma->vm_next;
2382                 unsigned long nstart = next->vm_start;
2383                 nstart += adjust_next << PAGE_SHIFT;
2384                 if (nstart & ~HPAGE_PMD_MASK &&
2385                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2386                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2387                         split_huge_page_address(next->vm_mm, nstart);
2388         }
2389 }