arm: tegra: usb_phy: fix hsic suspend issue on xmm
[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_foll(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         int tail_count = 0;
1160
1161         /* prevent PageLRU to go away from under us, and freeze lru stats */
1162         spin_lock_irq(&zone->lru_lock);
1163         compound_lock(page);
1164
1165         for (i = 1; i < HPAGE_PMD_NR; i++) {
1166                 struct page *page_tail = page + i;
1167
1168                 /* tail_page->_mapcount cannot change */
1169                 BUG_ON(page_mapcount(page_tail) < 0);
1170                 tail_count += page_mapcount(page_tail);
1171                 /* check for overflow */
1172                 BUG_ON(tail_count < 0);
1173                 BUG_ON(atomic_read(&page_tail->_count) != 0);
1174                 /*
1175                  * tail_page->_count is zero and not changing from
1176                  * under us. But get_page_unless_zero() may be running
1177                  * from under us on the tail_page. If we used
1178                  * atomic_set() below instead of atomic_add(), we
1179                  * would then run atomic_set() concurrently with
1180                  * get_page_unless_zero(), and atomic_set() is
1181                  * implemented in C not using locked ops. spin_unlock
1182                  * on x86 sometime uses locked ops because of PPro
1183                  * errata 66, 92, so unless somebody can guarantee
1184                  * atomic_set() here would be safe on all archs (and
1185                  * not only on x86), it's safer to use atomic_add().
1186                  */
1187                 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1188                            &page_tail->_count);
1189
1190                 /* after clearing PageTail the gup refcount can be released */
1191                 smp_mb();
1192
1193                 /*
1194                  * retain hwpoison flag of the poisoned tail page:
1195                  *   fix for the unsuitable process killed on Guest Machine(KVM)
1196                  *   by the memory-failure.
1197                  */
1198                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1199                 page_tail->flags |= (page->flags &
1200                                      ((1L << PG_referenced) |
1201                                       (1L << PG_swapbacked) |
1202                                       (1L << PG_mlocked) |
1203                                       (1L << PG_uptodate)));
1204                 page_tail->flags |= (1L << PG_dirty);
1205
1206                 /* clear PageTail before overwriting first_page */
1207                 smp_wmb();
1208
1209                 /*
1210                  * __split_huge_page_splitting() already set the
1211                  * splitting bit in all pmd that could map this
1212                  * hugepage, that will ensure no CPU can alter the
1213                  * mapcount on the head page. The mapcount is only
1214                  * accounted in the head page and it has to be
1215                  * transferred to all tail pages in the below code. So
1216                  * for this code to be safe, the split the mapcount
1217                  * can't change. But that doesn't mean userland can't
1218                  * keep changing and reading the page contents while
1219                  * we transfer the mapcount, so the pmd splitting
1220                  * status is achieved setting a reserved bit in the
1221                  * pmd, not by clearing the present bit.
1222                 */
1223                 page_tail->_mapcount = page->_mapcount;
1224
1225                 BUG_ON(page_tail->mapping);
1226                 page_tail->mapping = page->mapping;
1227
1228                 page_tail->index = ++head_index;
1229
1230                 BUG_ON(!PageAnon(page_tail));
1231                 BUG_ON(!PageUptodate(page_tail));
1232                 BUG_ON(!PageDirty(page_tail));
1233                 BUG_ON(!PageSwapBacked(page_tail));
1234
1235                 mem_cgroup_split_huge_fixup(page, page_tail);
1236
1237                 lru_add_page_tail(zone, page, page_tail);
1238         }
1239         atomic_sub(tail_count, &page->_count);
1240         BUG_ON(atomic_read(&page->_count) <= 0);
1241
1242         __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1243         __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1244
1245         /*
1246          * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1247          * so adjust those appropriately if this page is on the LRU.
1248          */
1249         if (PageLRU(page)) {
1250                 zonestat = NR_LRU_BASE + page_lru(page);
1251                 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1252         }
1253
1254         ClearPageCompound(page);
1255         compound_unlock(page);
1256         spin_unlock_irq(&zone->lru_lock);
1257
1258         for (i = 1; i < HPAGE_PMD_NR; i++) {
1259                 struct page *page_tail = page + i;
1260                 BUG_ON(page_count(page_tail) <= 0);
1261                 /*
1262                  * Tail pages may be freed if there wasn't any mapping
1263                  * like if add_to_swap() is running on a lru page that
1264                  * had its mapping zapped. And freeing these pages
1265                  * requires taking the lru_lock so we do the put_page
1266                  * of the tail pages after the split is complete.
1267                  */
1268                 put_page(page_tail);
1269         }
1270
1271         /*
1272          * Only the head page (now become a regular page) is required
1273          * to be pinned by the caller.
1274          */
1275         BUG_ON(page_count(page) <= 0);
1276 }
1277
1278 static int __split_huge_page_map(struct page *page,
1279                                  struct vm_area_struct *vma,
1280                                  unsigned long address)
1281 {
1282         struct mm_struct *mm = vma->vm_mm;
1283         pmd_t *pmd, _pmd;
1284         int ret = 0, i;
1285         pgtable_t pgtable;
1286         unsigned long haddr;
1287
1288         spin_lock(&mm->page_table_lock);
1289         pmd = page_check_address_pmd(page, mm, address,
1290                                      PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1291         if (pmd) {
1292                 pgtable = get_pmd_huge_pte(mm);
1293                 pmd_populate(mm, &_pmd, pgtable);
1294
1295                 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1296                      i++, haddr += PAGE_SIZE) {
1297                         pte_t *pte, entry;
1298                         BUG_ON(PageCompound(page+i));
1299                         entry = mk_pte(page + i, vma->vm_page_prot);
1300                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1301                         if (!pmd_write(*pmd))
1302                                 entry = pte_wrprotect(entry);
1303                         else
1304                                 BUG_ON(page_mapcount(page) != 1);
1305                         if (!pmd_young(*pmd))
1306                                 entry = pte_mkold(entry);
1307                         pte = pte_offset_map(&_pmd, haddr);
1308                         BUG_ON(!pte_none(*pte));
1309                         set_pte_at(mm, haddr, pte, entry);
1310                         pte_unmap(pte);
1311                 }
1312
1313                 mm->nr_ptes++;
1314                 smp_wmb(); /* make pte visible before pmd */
1315                 /*
1316                  * Up to this point the pmd is present and huge and
1317                  * userland has the whole access to the hugepage
1318                  * during the split (which happens in place). If we
1319                  * overwrite the pmd with the not-huge version
1320                  * pointing to the pte here (which of course we could
1321                  * if all CPUs were bug free), userland could trigger
1322                  * a small page size TLB miss on the small sized TLB
1323                  * while the hugepage TLB entry is still established
1324                  * in the huge TLB. Some CPU doesn't like that. See
1325                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1326                  * Erratum 383 on page 93. Intel should be safe but is
1327                  * also warns that it's only safe if the permission
1328                  * and cache attributes of the two entries loaded in
1329                  * the two TLB is identical (which should be the case
1330                  * here). But it is generally safer to never allow
1331                  * small and huge TLB entries for the same virtual
1332                  * address to be loaded simultaneously. So instead of
1333                  * doing "pmd_populate(); flush_tlb_range();" we first
1334                  * mark the current pmd notpresent (atomically because
1335                  * here the pmd_trans_huge and pmd_trans_splitting
1336                  * must remain set at all times on the pmd until the
1337                  * split is complete for this pmd), then we flush the
1338                  * SMP TLB and finally we write the non-huge version
1339                  * of the pmd entry with pmd_populate.
1340                  */
1341                 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1342                 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1343                 pmd_populate(mm, pmd, pgtable);
1344                 ret = 1;
1345         }
1346         spin_unlock(&mm->page_table_lock);
1347
1348         return ret;
1349 }
1350
1351 /* must be called with anon_vma->root->mutex hold */
1352 static void __split_huge_page(struct page *page,
1353                               struct anon_vma *anon_vma)
1354 {
1355         int mapcount, mapcount2;
1356         struct anon_vma_chain *avc;
1357
1358         BUG_ON(!PageHead(page));
1359         BUG_ON(PageTail(page));
1360
1361         mapcount = 0;
1362         list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1363                 struct vm_area_struct *vma = avc->vma;
1364                 unsigned long addr = vma_address(page, vma);
1365                 BUG_ON(is_vma_temporary_stack(vma));
1366                 if (addr == -EFAULT)
1367                         continue;
1368                 mapcount += __split_huge_page_splitting(page, vma, addr);
1369         }
1370         /*
1371          * It is critical that new vmas are added to the tail of the
1372          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1373          * and establishes a child pmd before
1374          * __split_huge_page_splitting() freezes the parent pmd (so if
1375          * we fail to prevent copy_huge_pmd() from running until the
1376          * whole __split_huge_page() is complete), we will still see
1377          * the newly established pmd of the child later during the
1378          * walk, to be able to set it as pmd_trans_splitting too.
1379          */
1380         if (mapcount != page_mapcount(page))
1381                 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1382                        mapcount, page_mapcount(page));
1383         BUG_ON(mapcount != page_mapcount(page));
1384
1385         __split_huge_page_refcount(page);
1386
1387         mapcount2 = 0;
1388         list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1389                 struct vm_area_struct *vma = avc->vma;
1390                 unsigned long addr = vma_address(page, vma);
1391                 BUG_ON(is_vma_temporary_stack(vma));
1392                 if (addr == -EFAULT)
1393                         continue;
1394                 mapcount2 += __split_huge_page_map(page, vma, addr);
1395         }
1396         if (mapcount != mapcount2)
1397                 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1398                        mapcount, mapcount2, page_mapcount(page));
1399         BUG_ON(mapcount != mapcount2);
1400 }
1401
1402 int split_huge_page(struct page *page)
1403 {
1404         struct anon_vma *anon_vma;
1405         int ret = 1;
1406
1407         BUG_ON(!PageAnon(page));
1408         anon_vma = page_lock_anon_vma(page);
1409         if (!anon_vma)
1410                 goto out;
1411         ret = 0;
1412         if (!PageCompound(page))
1413                 goto out_unlock;
1414
1415         BUG_ON(!PageSwapBacked(page));
1416         __split_huge_page(page, anon_vma);
1417         count_vm_event(THP_SPLIT);
1418
1419         BUG_ON(PageCompound(page));
1420 out_unlock:
1421         page_unlock_anon_vma(anon_vma);
1422 out:
1423         return ret;
1424 }
1425
1426 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1427                    VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1428
1429 int hugepage_madvise(struct vm_area_struct *vma,
1430                      unsigned long *vm_flags, int advice)
1431 {
1432         switch (advice) {
1433         case MADV_HUGEPAGE:
1434                 /*
1435                  * Be somewhat over-protective like KSM for now!
1436                  */
1437                 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1438                         return -EINVAL;
1439                 *vm_flags &= ~VM_NOHUGEPAGE;
1440                 *vm_flags |= VM_HUGEPAGE;
1441                 /*
1442                  * If the vma become good for khugepaged to scan,
1443                  * register it here without waiting a page fault that
1444                  * may not happen any time soon.
1445                  */
1446                 if (unlikely(khugepaged_enter_vma_merge(vma)))
1447                         return -ENOMEM;
1448                 break;
1449         case MADV_NOHUGEPAGE:
1450                 /*
1451                  * Be somewhat over-protective like KSM for now!
1452                  */
1453                 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1454                         return -EINVAL;
1455                 *vm_flags &= ~VM_HUGEPAGE;
1456                 *vm_flags |= VM_NOHUGEPAGE;
1457                 /*
1458                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1459                  * this vma even if we leave the mm registered in khugepaged if
1460                  * it got registered before VM_NOHUGEPAGE was set.
1461                  */
1462                 break;
1463         }
1464
1465         return 0;
1466 }
1467
1468 static int __init khugepaged_slab_init(void)
1469 {
1470         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1471                                           sizeof(struct mm_slot),
1472                                           __alignof__(struct mm_slot), 0, NULL);
1473         if (!mm_slot_cache)
1474                 return -ENOMEM;
1475
1476         return 0;
1477 }
1478
1479 static void __init khugepaged_slab_free(void)
1480 {
1481         kmem_cache_destroy(mm_slot_cache);
1482         mm_slot_cache = NULL;
1483 }
1484
1485 static inline struct mm_slot *alloc_mm_slot(void)
1486 {
1487         if (!mm_slot_cache)     /* initialization failed */
1488                 return NULL;
1489         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1490 }
1491
1492 static inline void free_mm_slot(struct mm_slot *mm_slot)
1493 {
1494         kmem_cache_free(mm_slot_cache, mm_slot);
1495 }
1496
1497 static int __init mm_slots_hash_init(void)
1498 {
1499         mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1500                                 GFP_KERNEL);
1501         if (!mm_slots_hash)
1502                 return -ENOMEM;
1503         return 0;
1504 }
1505
1506 #if 0
1507 static void __init mm_slots_hash_free(void)
1508 {
1509         kfree(mm_slots_hash);
1510         mm_slots_hash = NULL;
1511 }
1512 #endif
1513
1514 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1515 {
1516         struct mm_slot *mm_slot;
1517         struct hlist_head *bucket;
1518         struct hlist_node *node;
1519
1520         bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1521                                 % MM_SLOTS_HASH_HEADS];
1522         hlist_for_each_entry(mm_slot, node, bucket, hash) {
1523                 if (mm == mm_slot->mm)
1524                         return mm_slot;
1525         }
1526         return NULL;
1527 }
1528
1529 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1530                                     struct mm_slot *mm_slot)
1531 {
1532         struct hlist_head *bucket;
1533
1534         bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1535                                 % MM_SLOTS_HASH_HEADS];
1536         mm_slot->mm = mm;
1537         hlist_add_head(&mm_slot->hash, bucket);
1538 }
1539
1540 static inline int khugepaged_test_exit(struct mm_struct *mm)
1541 {
1542         return atomic_read(&mm->mm_users) == 0;
1543 }
1544
1545 int __khugepaged_enter(struct mm_struct *mm)
1546 {
1547         struct mm_slot *mm_slot;
1548         int wakeup;
1549
1550         mm_slot = alloc_mm_slot();
1551         if (!mm_slot)
1552                 return -ENOMEM;
1553
1554         /* __khugepaged_exit() must not run from under us */
1555         VM_BUG_ON(khugepaged_test_exit(mm));
1556         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1557                 free_mm_slot(mm_slot);
1558                 return 0;
1559         }
1560
1561         spin_lock(&khugepaged_mm_lock);
1562         insert_to_mm_slots_hash(mm, mm_slot);
1563         /*
1564          * Insert just behind the scanning cursor, to let the area settle
1565          * down a little.
1566          */
1567         wakeup = list_empty(&khugepaged_scan.mm_head);
1568         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1569         spin_unlock(&khugepaged_mm_lock);
1570
1571         atomic_inc(&mm->mm_count);
1572         if (wakeup)
1573                 wake_up_interruptible(&khugepaged_wait);
1574
1575         return 0;
1576 }
1577
1578 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1579 {
1580         unsigned long hstart, hend;
1581         if (!vma->anon_vma)
1582                 /*
1583                  * Not yet faulted in so we will register later in the
1584                  * page fault if needed.
1585                  */
1586                 return 0;
1587         if (vma->vm_ops)
1588                 /* khugepaged not yet working on file or special mappings */
1589                 return 0;
1590         /*
1591          * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1592          * true too, verify it here.
1593          */
1594         VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1595         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1596         hend = vma->vm_end & HPAGE_PMD_MASK;
1597         if (hstart < hend)
1598                 return khugepaged_enter(vma);
1599         return 0;
1600 }
1601
1602 void __khugepaged_exit(struct mm_struct *mm)
1603 {
1604         struct mm_slot *mm_slot;
1605         int free = 0;
1606
1607         spin_lock(&khugepaged_mm_lock);
1608         mm_slot = get_mm_slot(mm);
1609         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1610                 hlist_del(&mm_slot->hash);
1611                 list_del(&mm_slot->mm_node);
1612                 free = 1;
1613         }
1614         spin_unlock(&khugepaged_mm_lock);
1615
1616         if (free) {
1617                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1618                 free_mm_slot(mm_slot);
1619                 mmdrop(mm);
1620         } else if (mm_slot) {
1621                 /*
1622                  * This is required to serialize against
1623                  * khugepaged_test_exit() (which is guaranteed to run
1624                  * under mmap sem read mode). Stop here (after we
1625                  * return all pagetables will be destroyed) until
1626                  * khugepaged has finished working on the pagetables
1627                  * under the mmap_sem.
1628                  */
1629                 down_write(&mm->mmap_sem);
1630                 up_write(&mm->mmap_sem);
1631         }
1632 }
1633
1634 static void release_pte_page(struct page *page)
1635 {
1636         /* 0 stands for page_is_file_cache(page) == false */
1637         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1638         unlock_page(page);
1639         putback_lru_page(page);
1640 }
1641
1642 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1643 {
1644         while (--_pte >= pte) {
1645                 pte_t pteval = *_pte;
1646                 if (!pte_none(pteval))
1647                         release_pte_page(pte_page(pteval));
1648         }
1649 }
1650
1651 static void release_all_pte_pages(pte_t *pte)
1652 {
1653         release_pte_pages(pte, pte + HPAGE_PMD_NR);
1654 }
1655
1656 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1657                                         unsigned long address,
1658                                         pte_t *pte)
1659 {
1660         struct page *page;
1661         pte_t *_pte;
1662         int referenced = 0, isolated = 0, none = 0;
1663         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1664              _pte++, address += PAGE_SIZE) {
1665                 pte_t pteval = *_pte;
1666                 if (pte_none(pteval)) {
1667                         if (++none <= khugepaged_max_ptes_none)
1668                                 continue;
1669                         else {
1670                                 release_pte_pages(pte, _pte);
1671                                 goto out;
1672                         }
1673                 }
1674                 if (!pte_present(pteval) || !pte_write(pteval)) {
1675                         release_pte_pages(pte, _pte);
1676                         goto out;
1677                 }
1678                 page = vm_normal_page(vma, address, pteval);
1679                 if (unlikely(!page)) {
1680                         release_pte_pages(pte, _pte);
1681                         goto out;
1682                 }
1683                 VM_BUG_ON(PageCompound(page));
1684                 BUG_ON(!PageAnon(page));
1685                 VM_BUG_ON(!PageSwapBacked(page));
1686
1687                 /* cannot use mapcount: can't collapse if there's a gup pin */
1688                 if (page_count(page) != 1) {
1689                         release_pte_pages(pte, _pte);
1690                         goto out;
1691                 }
1692                 /*
1693                  * We can do it before isolate_lru_page because the
1694                  * page can't be freed from under us. NOTE: PG_lock
1695                  * is needed to serialize against split_huge_page
1696                  * when invoked from the VM.
1697                  */
1698                 if (!trylock_page(page)) {
1699                         release_pte_pages(pte, _pte);
1700                         goto out;
1701                 }
1702                 /*
1703                  * Isolate the page to avoid collapsing an hugepage
1704                  * currently in use by the VM.
1705                  */
1706                 if (isolate_lru_page(page)) {
1707                         unlock_page(page);
1708                         release_pte_pages(pte, _pte);
1709                         goto out;
1710                 }
1711                 /* 0 stands for page_is_file_cache(page) == false */
1712                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1713                 VM_BUG_ON(!PageLocked(page));
1714                 VM_BUG_ON(PageLRU(page));
1715
1716                 /* If there is no mapped pte young don't collapse the page */
1717                 if (pte_young(pteval) || PageReferenced(page) ||
1718                     mmu_notifier_test_young(vma->vm_mm, address))
1719                         referenced = 1;
1720         }
1721         if (unlikely(!referenced))
1722                 release_all_pte_pages(pte);
1723         else
1724                 isolated = 1;
1725 out:
1726         return isolated;
1727 }
1728
1729 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1730                                       struct vm_area_struct *vma,
1731                                       unsigned long address,
1732                                       spinlock_t *ptl)
1733 {
1734         pte_t *_pte;
1735         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1736                 pte_t pteval = *_pte;
1737                 struct page *src_page;
1738
1739                 if (pte_none(pteval)) {
1740                         clear_user_highpage(page, address);
1741                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1742                 } else {
1743                         src_page = pte_page(pteval);
1744                         copy_user_highpage(page, src_page, address, vma);
1745                         VM_BUG_ON(page_mapcount(src_page) != 1);
1746                         VM_BUG_ON(page_count(src_page) != 2);
1747                         release_pte_page(src_page);
1748                         /*
1749                          * ptl mostly unnecessary, but preempt has to
1750                          * be disabled to update the per-cpu stats
1751                          * inside page_remove_rmap().
1752                          */
1753                         spin_lock(ptl);
1754                         /*
1755                          * paravirt calls inside pte_clear here are
1756                          * superfluous.
1757                          */
1758                         pte_clear(vma->vm_mm, address, _pte);
1759                         page_remove_rmap(src_page);
1760                         spin_unlock(ptl);
1761                         free_page_and_swap_cache(src_page);
1762                 }
1763
1764                 address += PAGE_SIZE;
1765                 page++;
1766         }
1767 }
1768
1769 static void collapse_huge_page(struct mm_struct *mm,
1770                                unsigned long address,
1771                                struct page **hpage,
1772                                struct vm_area_struct *vma,
1773                                int node)
1774 {
1775         pgd_t *pgd;
1776         pud_t *pud;
1777         pmd_t *pmd, _pmd;
1778         pte_t *pte;
1779         pgtable_t pgtable;
1780         struct page *new_page;
1781         spinlock_t *ptl;
1782         int isolated;
1783         unsigned long hstart, hend;
1784
1785         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1786 #ifndef CONFIG_NUMA
1787         up_read(&mm->mmap_sem);
1788         VM_BUG_ON(!*hpage);
1789         new_page = *hpage;
1790 #else
1791         VM_BUG_ON(*hpage);
1792         /*
1793          * Allocate the page while the vma is still valid and under
1794          * the mmap_sem read mode so there is no memory allocation
1795          * later when we take the mmap_sem in write mode. This is more
1796          * friendly behavior (OTOH it may actually hide bugs) to
1797          * filesystems in userland with daemons allocating memory in
1798          * the userland I/O paths.  Allocating memory with the
1799          * mmap_sem in read mode is good idea also to allow greater
1800          * scalability.
1801          */
1802         new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1803                                       node, __GFP_OTHER_NODE);
1804
1805         /*
1806          * After allocating the hugepage, release the mmap_sem read lock in
1807          * preparation for taking it in write mode.
1808          */
1809         up_read(&mm->mmap_sem);
1810         if (unlikely(!new_page)) {
1811                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1812                 *hpage = ERR_PTR(-ENOMEM);
1813                 return;
1814         }
1815 #endif
1816
1817         count_vm_event(THP_COLLAPSE_ALLOC);
1818         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1819 #ifdef CONFIG_NUMA
1820                 put_page(new_page);
1821 #endif
1822                 return;
1823         }
1824
1825         /*
1826          * Prevent all access to pagetables with the exception of
1827          * gup_fast later hanlded by the ptep_clear_flush and the VM
1828          * handled by the anon_vma lock + PG_lock.
1829          */
1830         down_write(&mm->mmap_sem);
1831         if (unlikely(khugepaged_test_exit(mm)))
1832                 goto out;
1833
1834         vma = find_vma(mm, address);
1835         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1836         hend = vma->vm_end & HPAGE_PMD_MASK;
1837         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1838                 goto out;
1839
1840         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1841             (vma->vm_flags & VM_NOHUGEPAGE))
1842                 goto out;
1843
1844         if (!vma->anon_vma || vma->vm_ops)
1845                 goto out;
1846         if (is_vma_temporary_stack(vma))
1847                 goto out;
1848         /*
1849          * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1850          * true too, verify it here.
1851          */
1852         VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1853
1854         pgd = pgd_offset(mm, address);
1855         if (!pgd_present(*pgd))
1856                 goto out;
1857
1858         pud = pud_offset(pgd, address);
1859         if (!pud_present(*pud))
1860                 goto out;
1861
1862         pmd = pmd_offset(pud, address);
1863         /* pmd can't go away or become huge under us */
1864         if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1865                 goto out;
1866
1867         anon_vma_lock(vma->anon_vma);
1868
1869         pte = pte_offset_map(pmd, address);
1870         ptl = pte_lockptr(mm, pmd);
1871
1872         spin_lock(&mm->page_table_lock); /* probably unnecessary */
1873         /*
1874          * After this gup_fast can't run anymore. This also removes
1875          * any huge TLB entry from the CPU so we won't allow
1876          * huge and small TLB entries for the same virtual address
1877          * to avoid the risk of CPU bugs in that area.
1878          */
1879         _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1880         spin_unlock(&mm->page_table_lock);
1881
1882         spin_lock(ptl);
1883         isolated = __collapse_huge_page_isolate(vma, address, pte);
1884         spin_unlock(ptl);
1885
1886         if (unlikely(!isolated)) {
1887                 pte_unmap(pte);
1888                 spin_lock(&mm->page_table_lock);
1889                 BUG_ON(!pmd_none(*pmd));
1890                 set_pmd_at(mm, address, pmd, _pmd);
1891                 spin_unlock(&mm->page_table_lock);
1892                 anon_vma_unlock(vma->anon_vma);
1893                 goto out;
1894         }
1895
1896         /*
1897          * All pages are isolated and locked so anon_vma rmap
1898          * can't run anymore.
1899          */
1900         anon_vma_unlock(vma->anon_vma);
1901
1902         __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1903         pte_unmap(pte);
1904         __SetPageUptodate(new_page);
1905         pgtable = pmd_pgtable(_pmd);
1906         VM_BUG_ON(page_count(pgtable) != 1);
1907         VM_BUG_ON(page_mapcount(pgtable) != 0);
1908
1909         _pmd = mk_pmd(new_page, vma->vm_page_prot);
1910         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1911         _pmd = pmd_mkhuge(_pmd);
1912
1913         /*
1914          * spin_lock() below is not the equivalent of smp_wmb(), so
1915          * this is needed to avoid the copy_huge_page writes to become
1916          * visible after the set_pmd_at() write.
1917          */
1918         smp_wmb();
1919
1920         spin_lock(&mm->page_table_lock);
1921         BUG_ON(!pmd_none(*pmd));
1922         page_add_new_anon_rmap(new_page, vma, address);
1923         set_pmd_at(mm, address, pmd, _pmd);
1924         update_mmu_cache(vma, address, entry);
1925         prepare_pmd_huge_pte(pgtable, mm);
1926         mm->nr_ptes--;
1927         spin_unlock(&mm->page_table_lock);
1928
1929 #ifndef CONFIG_NUMA
1930         *hpage = NULL;
1931 #endif
1932         khugepaged_pages_collapsed++;
1933 out_up_write:
1934         up_write(&mm->mmap_sem);
1935         return;
1936
1937 out:
1938         mem_cgroup_uncharge_page(new_page);
1939 #ifdef CONFIG_NUMA
1940         put_page(new_page);
1941 #endif
1942         goto out_up_write;
1943 }
1944
1945 static int khugepaged_scan_pmd(struct mm_struct *mm,
1946                                struct vm_area_struct *vma,
1947                                unsigned long address,
1948                                struct page **hpage)
1949 {
1950         pgd_t *pgd;
1951         pud_t *pud;
1952         pmd_t *pmd;
1953         pte_t *pte, *_pte;
1954         int ret = 0, referenced = 0, none = 0;
1955         struct page *page;
1956         unsigned long _address;
1957         spinlock_t *ptl;
1958         int node = -1;
1959
1960         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1961
1962         pgd = pgd_offset(mm, address);
1963         if (!pgd_present(*pgd))
1964                 goto out;
1965
1966         pud = pud_offset(pgd, address);
1967         if (!pud_present(*pud))
1968                 goto out;
1969
1970         pmd = pmd_offset(pud, address);
1971         if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1972                 goto out;
1973
1974         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1975         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1976              _pte++, _address += PAGE_SIZE) {
1977                 pte_t pteval = *_pte;
1978                 if (pte_none(pteval)) {
1979                         if (++none <= khugepaged_max_ptes_none)
1980                                 continue;
1981                         else
1982                                 goto out_unmap;
1983                 }
1984                 if (!pte_present(pteval) || !pte_write(pteval))
1985                         goto out_unmap;
1986                 page = vm_normal_page(vma, _address, pteval);
1987                 if (unlikely(!page))
1988                         goto out_unmap;
1989                 /*
1990                  * Chose the node of the first page. This could
1991                  * be more sophisticated and look at more pages,
1992                  * but isn't for now.
1993                  */
1994                 if (node == -1)
1995                         node = page_to_nid(page);
1996                 VM_BUG_ON(PageCompound(page));
1997                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1998                         goto out_unmap;
1999                 /* cannot use mapcount: can't collapse if there's a gup pin */
2000                 if (page_count(page) != 1)
2001                         goto out_unmap;
2002                 if (pte_young(pteval) || PageReferenced(page) ||
2003                     mmu_notifier_test_young(vma->vm_mm, address))
2004                         referenced = 1;
2005         }
2006         if (referenced)
2007                 ret = 1;
2008 out_unmap:
2009         pte_unmap_unlock(pte, ptl);
2010         if (ret)
2011                 /* collapse_huge_page will return with the mmap_sem released */
2012                 collapse_huge_page(mm, address, hpage, vma, node);
2013 out:
2014         return ret;
2015 }
2016
2017 static void collect_mm_slot(struct mm_slot *mm_slot)
2018 {
2019         struct mm_struct *mm = mm_slot->mm;
2020
2021         VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2022
2023         if (khugepaged_test_exit(mm)) {
2024                 /* free mm_slot */
2025                 hlist_del(&mm_slot->hash);
2026                 list_del(&mm_slot->mm_node);
2027
2028                 /*
2029                  * Not strictly needed because the mm exited already.
2030                  *
2031                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2032                  */
2033
2034                 /* khugepaged_mm_lock actually not necessary for the below */
2035                 free_mm_slot(mm_slot);
2036                 mmdrop(mm);
2037         }
2038 }
2039
2040 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2041                                             struct page **hpage)
2042 {
2043         struct mm_slot *mm_slot;
2044         struct mm_struct *mm;
2045         struct vm_area_struct *vma;
2046         int progress = 0;
2047
2048         VM_BUG_ON(!pages);
2049         VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2050
2051         if (khugepaged_scan.mm_slot)
2052                 mm_slot = khugepaged_scan.mm_slot;
2053         else {
2054                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2055                                      struct mm_slot, mm_node);
2056                 khugepaged_scan.address = 0;
2057                 khugepaged_scan.mm_slot = mm_slot;
2058         }
2059         spin_unlock(&khugepaged_mm_lock);
2060
2061         mm = mm_slot->mm;
2062         down_read(&mm->mmap_sem);
2063         if (unlikely(khugepaged_test_exit(mm)))
2064                 vma = NULL;
2065         else
2066                 vma = find_vma(mm, khugepaged_scan.address);
2067
2068         progress++;
2069         for (; vma; vma = vma->vm_next) {
2070                 unsigned long hstart, hend;
2071
2072                 cond_resched();
2073                 if (unlikely(khugepaged_test_exit(mm))) {
2074                         progress++;
2075                         break;
2076                 }
2077
2078                 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2079                      !khugepaged_always()) ||
2080                     (vma->vm_flags & VM_NOHUGEPAGE)) {
2081                 skip:
2082                         progress++;
2083                         continue;
2084                 }
2085                 if (!vma->anon_vma || vma->vm_ops)
2086                         goto skip;
2087                 if (is_vma_temporary_stack(vma))
2088                         goto skip;
2089                 /*
2090                  * If is_pfn_mapping() is true is_learn_pfn_mapping()
2091                  * must be true too, verify it here.
2092                  */
2093                 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2094                           vma->vm_flags & VM_NO_THP);
2095
2096                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2097                 hend = vma->vm_end & HPAGE_PMD_MASK;
2098                 if (hstart >= hend)
2099                         goto skip;
2100                 if (khugepaged_scan.address > hend)
2101                         goto skip;
2102                 if (khugepaged_scan.address < hstart)
2103                         khugepaged_scan.address = hstart;
2104                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2105
2106                 while (khugepaged_scan.address < hend) {
2107                         int ret;
2108                         cond_resched();
2109                         if (unlikely(khugepaged_test_exit(mm)))
2110                                 goto breakouterloop;
2111
2112                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2113                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2114                                   hend);
2115                         ret = khugepaged_scan_pmd(mm, vma,
2116                                                   khugepaged_scan.address,
2117                                                   hpage);
2118                         /* move to next address */
2119                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2120                         progress += HPAGE_PMD_NR;
2121                         if (ret)
2122                                 /* we released mmap_sem so break loop */
2123                                 goto breakouterloop_mmap_sem;
2124                         if (progress >= pages)
2125                                 goto breakouterloop;
2126                 }
2127         }
2128 breakouterloop:
2129         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2130 breakouterloop_mmap_sem:
2131
2132         spin_lock(&khugepaged_mm_lock);
2133         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2134         /*
2135          * Release the current mm_slot if this mm is about to die, or
2136          * if we scanned all vmas of this mm.
2137          */
2138         if (khugepaged_test_exit(mm) || !vma) {
2139                 /*
2140                  * Make sure that if mm_users is reaching zero while
2141                  * khugepaged runs here, khugepaged_exit will find
2142                  * mm_slot not pointing to the exiting mm.
2143                  */
2144                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2145                         khugepaged_scan.mm_slot = list_entry(
2146                                 mm_slot->mm_node.next,
2147                                 struct mm_slot, mm_node);
2148                         khugepaged_scan.address = 0;
2149                 } else {
2150                         khugepaged_scan.mm_slot = NULL;
2151                         khugepaged_full_scans++;
2152                 }
2153
2154                 collect_mm_slot(mm_slot);
2155         }
2156
2157         return progress;
2158 }
2159
2160 static int khugepaged_has_work(void)
2161 {
2162         return !list_empty(&khugepaged_scan.mm_head) &&
2163                 khugepaged_enabled();
2164 }
2165
2166 static int khugepaged_wait_event(void)
2167 {
2168         return !list_empty(&khugepaged_scan.mm_head) ||
2169                 !khugepaged_enabled();
2170 }
2171
2172 static void khugepaged_do_scan(struct page **hpage)
2173 {
2174         unsigned int progress = 0, pass_through_head = 0;
2175         unsigned int pages = khugepaged_pages_to_scan;
2176
2177         barrier(); /* write khugepaged_pages_to_scan to local stack */
2178
2179         while (progress < pages) {
2180                 cond_resched();
2181
2182 #ifndef CONFIG_NUMA
2183                 if (!*hpage) {
2184                         *hpage = alloc_hugepage(khugepaged_defrag());
2185                         if (unlikely(!*hpage)) {
2186                                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2187                                 break;
2188                         }
2189                         count_vm_event(THP_COLLAPSE_ALLOC);
2190                 }
2191 #else
2192                 if (IS_ERR(*hpage))
2193                         break;
2194 #endif
2195
2196                 if (unlikely(kthread_should_stop() || freezing(current)))
2197                         break;
2198
2199                 spin_lock(&khugepaged_mm_lock);
2200                 if (!khugepaged_scan.mm_slot)
2201                         pass_through_head++;
2202                 if (khugepaged_has_work() &&
2203                     pass_through_head < 2)
2204                         progress += khugepaged_scan_mm_slot(pages - progress,
2205                                                             hpage);
2206                 else
2207                         progress = pages;
2208                 spin_unlock(&khugepaged_mm_lock);
2209         }
2210 }
2211
2212 static void khugepaged_alloc_sleep(void)
2213 {
2214         DEFINE_WAIT(wait);
2215         add_wait_queue(&khugepaged_wait, &wait);
2216         schedule_timeout_interruptible(
2217                 msecs_to_jiffies(
2218                         khugepaged_alloc_sleep_millisecs));
2219         remove_wait_queue(&khugepaged_wait, &wait);
2220 }
2221
2222 #ifndef CONFIG_NUMA
2223 static struct page *khugepaged_alloc_hugepage(void)
2224 {
2225         struct page *hpage;
2226
2227         do {
2228                 hpage = alloc_hugepage(khugepaged_defrag());
2229                 if (!hpage) {
2230                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2231                         khugepaged_alloc_sleep();
2232                 } else
2233                         count_vm_event(THP_COLLAPSE_ALLOC);
2234         } while (unlikely(!hpage) &&
2235                  likely(khugepaged_enabled()));
2236         return hpage;
2237 }
2238 #endif
2239
2240 static void khugepaged_loop(void)
2241 {
2242         struct page *hpage;
2243
2244 #ifdef CONFIG_NUMA
2245         hpage = NULL;
2246 #endif
2247         while (likely(khugepaged_enabled())) {
2248 #ifndef CONFIG_NUMA
2249                 hpage = khugepaged_alloc_hugepage();
2250                 if (unlikely(!hpage))
2251                         break;
2252 #else
2253                 if (IS_ERR(hpage)) {
2254                         khugepaged_alloc_sleep();
2255                         hpage = NULL;
2256                 }
2257 #endif
2258
2259                 khugepaged_do_scan(&hpage);
2260 #ifndef CONFIG_NUMA
2261                 if (hpage)
2262                         put_page(hpage);
2263 #endif
2264                 try_to_freeze();
2265                 if (unlikely(kthread_should_stop()))
2266                         break;
2267                 if (khugepaged_has_work()) {
2268                         DEFINE_WAIT(wait);
2269                         if (!khugepaged_scan_sleep_millisecs)
2270                                 continue;
2271                         add_wait_queue(&khugepaged_wait, &wait);
2272                         schedule_timeout_interruptible(
2273                                 msecs_to_jiffies(
2274                                         khugepaged_scan_sleep_millisecs));
2275                         remove_wait_queue(&khugepaged_wait, &wait);
2276                 } else if (khugepaged_enabled())
2277                         wait_event_freezable(khugepaged_wait,
2278                                              khugepaged_wait_event());
2279         }
2280 }
2281
2282 static int khugepaged(void *none)
2283 {
2284         struct mm_slot *mm_slot;
2285
2286         set_freezable();
2287         set_user_nice(current, 19);
2288
2289         /* serialize with start_khugepaged() */
2290         mutex_lock(&khugepaged_mutex);
2291
2292         for (;;) {
2293                 mutex_unlock(&khugepaged_mutex);
2294                 VM_BUG_ON(khugepaged_thread != current);
2295                 khugepaged_loop();
2296                 VM_BUG_ON(khugepaged_thread != current);
2297
2298                 mutex_lock(&khugepaged_mutex);
2299                 if (!khugepaged_enabled())
2300                         break;
2301                 if (unlikely(kthread_should_stop()))
2302                         break;
2303         }
2304
2305         spin_lock(&khugepaged_mm_lock);
2306         mm_slot = khugepaged_scan.mm_slot;
2307         khugepaged_scan.mm_slot = NULL;
2308         if (mm_slot)
2309                 collect_mm_slot(mm_slot);
2310         spin_unlock(&khugepaged_mm_lock);
2311
2312         khugepaged_thread = NULL;
2313         mutex_unlock(&khugepaged_mutex);
2314
2315         return 0;
2316 }
2317
2318 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2319 {
2320         struct page *page;
2321
2322         spin_lock(&mm->page_table_lock);
2323         if (unlikely(!pmd_trans_huge(*pmd))) {
2324                 spin_unlock(&mm->page_table_lock);
2325                 return;
2326         }
2327         page = pmd_page(*pmd);
2328         VM_BUG_ON(!page_count(page));
2329         get_page(page);
2330         spin_unlock(&mm->page_table_lock);
2331
2332         split_huge_page(page);
2333
2334         put_page(page);
2335         BUG_ON(pmd_trans_huge(*pmd));
2336 }
2337
2338 static void split_huge_page_address(struct mm_struct *mm,
2339                                     unsigned long address)
2340 {
2341         pgd_t *pgd;
2342         pud_t *pud;
2343         pmd_t *pmd;
2344
2345         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2346
2347         pgd = pgd_offset(mm, address);
2348         if (!pgd_present(*pgd))
2349                 return;
2350
2351         pud = pud_offset(pgd, address);
2352         if (!pud_present(*pud))
2353                 return;
2354
2355         pmd = pmd_offset(pud, address);
2356         if (!pmd_present(*pmd))
2357                 return;
2358         /*
2359          * Caller holds the mmap_sem write mode, so a huge pmd cannot
2360          * materialize from under us.
2361          */
2362         split_huge_page_pmd(mm, pmd);
2363 }
2364
2365 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2366                              unsigned long start,
2367                              unsigned long end,
2368                              long adjust_next)
2369 {
2370         /*
2371          * If the new start address isn't hpage aligned and it could
2372          * previously contain an hugepage: check if we need to split
2373          * an huge pmd.
2374          */
2375         if (start & ~HPAGE_PMD_MASK &&
2376             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2377             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2378                 split_huge_page_address(vma->vm_mm, start);
2379
2380         /*
2381          * If the new end address isn't hpage aligned and it could
2382          * previously contain an hugepage: check if we need to split
2383          * an huge pmd.
2384          */
2385         if (end & ~HPAGE_PMD_MASK &&
2386             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2387             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2388                 split_huge_page_address(vma->vm_mm, end);
2389
2390         /*
2391          * If we're also updating the vma->vm_next->vm_start, if the new
2392          * vm_next->vm_start isn't page aligned and it could previously
2393          * contain an hugepage: check if we need to split an huge pmd.
2394          */
2395         if (adjust_next > 0) {
2396                 struct vm_area_struct *next = vma->vm_next;
2397                 unsigned long nstart = next->vm_start;
2398                 nstart += adjust_next << PAGE_SHIFT;
2399                 if (nstart & ~HPAGE_PMD_MASK &&
2400                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2401                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2402                         split_huge_page_address(next->vm_mm, nstart);
2403         }
2404 }