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

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