linux/mm/huge_memory.c
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   1/*
   2 *  Copyright (C) 2009  Red Hat, Inc.
   3 *
   4 *  This work is licensed under the terms of the GNU GPL, version 2. See
   5 *  the COPYING file in the top-level directory.
   6 */
   7
   8#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 <linux/pagemap.h>
  21#include <asm/tlb.h>
  22#include <asm/pgalloc.h>
  23#include "internal.h"
  24
  25/*
  26 * By default transparent hugepage support is enabled for all mappings
  27 * and khugepaged scans all mappings. Defrag is only invoked by
  28 * khugepaged hugepage allocations and by page faults inside
  29 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
  30 * allocations.
  31 */
  32unsigned long transparent_hugepage_flags __read_mostly =
  33#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  34        (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  35#endif
  36#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  37        (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  38#endif
  39        (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
  40        (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
  41
  42/* default scan 8*512 pte (or vmas) every 30 second */
  43static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
  44static unsigned int khugepaged_pages_collapsed;
  45static unsigned int khugepaged_full_scans;
  46static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  47/* during fragmentation poll the hugepage allocator once every minute */
  48static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  49static struct task_struct *khugepaged_thread __read_mostly;
  50static DEFINE_MUTEX(khugepaged_mutex);
  51static DEFINE_SPINLOCK(khugepaged_mm_lock);
  52static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  53/*
  54 * default collapse hugepages if there is at least one pte mapped like
  55 * it would have happened if the vma was large enough during page
  56 * fault.
  57 */
  58static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
  59
  60static int khugepaged(void *none);
  61static int mm_slots_hash_init(void);
  62static int khugepaged_slab_init(void);
  63static void khugepaged_slab_free(void);
  64
  65#define MM_SLOTS_HASH_HEADS 1024
  66static struct hlist_head *mm_slots_hash __read_mostly;
  67static struct kmem_cache *mm_slot_cache __read_mostly;
  68
  69/**
  70 * struct mm_slot - hash lookup from mm to mm_slot
  71 * @hash: hash collision list
  72 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
  73 * @mm: the mm that this information is valid for
  74 */
  75struct mm_slot {
  76        struct hlist_node hash;
  77        struct list_head mm_node;
  78        struct mm_struct *mm;
  79};
  80
  81/**
  82 * struct khugepaged_scan - cursor for scanning
  83 * @mm_head: the head of the mm list to scan
  84 * @mm_slot: the current mm_slot we are scanning
  85 * @address: the next address inside that to be scanned
  86 *
  87 * There is only the one khugepaged_scan instance of this cursor structure.
  88 */
  89struct khugepaged_scan {
  90        struct list_head mm_head;
  91        struct mm_slot *mm_slot;
  92        unsigned long address;
  93};
  94static struct khugepaged_scan khugepaged_scan = {
  95        .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
  96};
  97
  98
  99static int set_recommended_min_free_kbytes(void)
 100{
 101        struct zone *zone;
 102        int nr_zones = 0;
 103        unsigned long recommended_min;
 104        extern int min_free_kbytes;
 105
 106        if (!khugepaged_enabled())
 107                return 0;
 108
 109        for_each_populated_zone(zone)
 110                nr_zones++;
 111
 112        /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
 113        recommended_min = pageblock_nr_pages * nr_zones * 2;
 114
 115        /*
 116         * Make sure that on average at least two pageblocks are almost free
 117         * of another type, one for a migratetype to fall back to and a
 118         * second to avoid subsequent fallbacks of other types There are 3
 119         * MIGRATE_TYPES we care about.
 120         */
 121        recommended_min += pageblock_nr_pages * nr_zones *
 122                           MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
 123
 124        /* don't ever allow to reserve more than 5% of the lowmem */
 125        recommended_min = min(recommended_min,
 126                              (unsigned long) nr_free_buffer_pages() / 20);
 127        recommended_min <<= (PAGE_SHIFT-10);
 128
 129        if (recommended_min > min_free_kbytes)
 130                min_free_kbytes = recommended_min;
 131        setup_per_zone_wmarks();
 132        return 0;
 133}
 134late_initcall(set_recommended_min_free_kbytes);
 135
 136static int start_khugepaged(void)
 137{
 138        int err = 0;
 139        if (khugepaged_enabled()) {
 140                if (!khugepaged_thread)
 141                        khugepaged_thread = kthread_run(khugepaged, NULL,
 142                                                        "khugepaged");
 143                if (unlikely(IS_ERR(khugepaged_thread))) {
 144                        printk(KERN_ERR
 145                               "khugepaged: kthread_run(khugepaged) failed\n");
 146                        err = PTR_ERR(khugepaged_thread);
 147                        khugepaged_thread = NULL;
 148                }
 149
 150                if (!list_empty(&khugepaged_scan.mm_head))
 151                        wake_up_interruptible(&khugepaged_wait);
 152
 153                set_recommended_min_free_kbytes();
 154        } else if (khugepaged_thread) {
 155                kthread_stop(khugepaged_thread);
 156                khugepaged_thread = NULL;
 157        }
 158
 159        return err;
 160}
 161
 162#ifdef CONFIG_SYSFS
 163
 164static ssize_t double_flag_show(struct kobject *kobj,
 165                                struct kobj_attribute *attr, char *buf,
 166                                enum transparent_hugepage_flag enabled,
 167                                enum transparent_hugepage_flag req_madv)
 168{
 169        if (test_bit(enabled, &transparent_hugepage_flags)) {
 170                VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
 171                return sprintf(buf, "[always] madvise never\n");
 172        } else if (test_bit(req_madv, &transparent_hugepage_flags))
 173                return sprintf(buf, "always [madvise] never\n");
 174        else
 175                return sprintf(buf, "always madvise [never]\n");
 176}
 177static ssize_t double_flag_store(struct kobject *kobj,
 178                                 struct kobj_attribute *attr,
 179                                 const char *buf, size_t count,
 180                                 enum transparent_hugepage_flag enabled,
 181                                 enum transparent_hugepage_flag req_madv)
 182{
 183        if (!memcmp("always", buf,
 184                    min(sizeof("always")-1, count))) {
 185                set_bit(enabled, &transparent_hugepage_flags);
 186                clear_bit(req_madv, &transparent_hugepage_flags);
 187        } else if (!memcmp("madvise", buf,
 188                           min(sizeof("madvise")-1, count))) {
 189                clear_bit(enabled, &transparent_hugepage_flags);
 190                set_bit(req_madv, &transparent_hugepage_flags);
 191        } else if (!memcmp("never", buf,
 192                           min(sizeof("never")-1, count))) {
 193                clear_bit(enabled, &transparent_hugepage_flags);
 194                clear_bit(req_madv, &transparent_hugepage_flags);
 195        } else
 196                return -EINVAL;
 197
 198        return count;
 199}
 200
 201static ssize_t enabled_show(struct kobject *kobj,
 202                            struct kobj_attribute *attr, char *buf)
 203{
 204        return double_flag_show(kobj, attr, buf,
 205                                TRANSPARENT_HUGEPAGE_FLAG,
 206                                TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 207}
 208static ssize_t enabled_store(struct kobject *kobj,
 209                             struct kobj_attribute *attr,
 210                             const char *buf, size_t count)
 211{
 212        ssize_t ret;
 213
 214        ret = double_flag_store(kobj, attr, buf, count,
 215                                TRANSPARENT_HUGEPAGE_FLAG,
 216                                TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 217
 218        if (ret > 0) {
 219                int err;
 220
 221                mutex_lock(&khugepaged_mutex);
 222                err = start_khugepaged();
 223                mutex_unlock(&khugepaged_mutex);
 224
 225                if (err)
 226                        ret = err;
 227        }
 228
 229        return ret;
 230}
 231static struct kobj_attribute enabled_attr =
 232        __ATTR(enabled, 0644, enabled_show, enabled_store);
 233
 234static ssize_t single_flag_show(struct kobject *kobj,
 235                                struct kobj_attribute *attr, char *buf,
 236                                enum transparent_hugepage_flag flag)
 237{
 238        return sprintf(buf, "%d\n",
 239                       !!test_bit(flag, &transparent_hugepage_flags));
 240}
 241
 242static ssize_t single_flag_store(struct kobject *kobj,
 243                                 struct kobj_attribute *attr,
 244                                 const char *buf, size_t count,
 245                                 enum transparent_hugepage_flag flag)
 246{
 247        unsigned long value;
 248        int ret;
 249
 250        ret = kstrtoul(buf, 10, &value);
 251        if (ret < 0)
 252                return ret;
 253        if (value > 1)
 254                return -EINVAL;
 255
 256        if (value)
 257                set_bit(flag, &transparent_hugepage_flags);
 258        else
 259                clear_bit(flag, &transparent_hugepage_flags);
 260
 261        return count;
 262}
 263
 264/*
 265 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 266 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 267 * memory just to allocate one more hugepage.
 268 */
 269static ssize_t defrag_show(struct kobject *kobj,
 270                           struct kobj_attribute *attr, char *buf)
 271{
 272        return double_flag_show(kobj, attr, buf,
 273                                TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 274                                TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 275}
 276static ssize_t defrag_store(struct kobject *kobj,
 277                            struct kobj_attribute *attr,
 278                            const char *buf, size_t count)
 279{
 280        return double_flag_store(kobj, attr, buf, count,
 281                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 282                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 283}
 284static struct kobj_attribute defrag_attr =
 285        __ATTR(defrag, 0644, defrag_show, defrag_store);
 286
 287#ifdef CONFIG_DEBUG_VM
 288static ssize_t debug_cow_show(struct kobject *kobj,
 289                                struct kobj_attribute *attr, char *buf)
 290{
 291        return single_flag_show(kobj, attr, buf,
 292                                TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 293}
 294static ssize_t debug_cow_store(struct kobject *kobj,
 295                               struct kobj_attribute *attr,
 296                               const char *buf, size_t count)
 297{
 298        return single_flag_store(kobj, attr, buf, count,
 299                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 300}
 301static struct kobj_attribute debug_cow_attr =
 302        __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 303#endif /* CONFIG_DEBUG_VM */
 304
 305static struct attribute *hugepage_attr[] = {
 306        &enabled_attr.attr,
 307        &defrag_attr.attr,
 308#ifdef CONFIG_DEBUG_VM
 309        &debug_cow_attr.attr,
 310#endif
 311        NULL,
 312};
 313
 314static struct attribute_group hugepage_attr_group = {
 315        .attrs = hugepage_attr,
 316};
 317
 318static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 319                                         struct kobj_attribute *attr,
 320                                         char *buf)
 321{
 322        return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 323}
 324
 325static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 326                                          struct kobj_attribute *attr,
 327                                          const char *buf, size_t count)
 328{
 329        unsigned long msecs;
 330        int err;
 331
 332        err = strict_strtoul(buf, 10, &msecs);
 333        if (err || msecs > UINT_MAX)
 334                return -EINVAL;
 335
 336        khugepaged_scan_sleep_millisecs = msecs;
 337        wake_up_interruptible(&khugepaged_wait);
 338
 339        return count;
 340}
 341static struct kobj_attribute scan_sleep_millisecs_attr =
 342        __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 343               scan_sleep_millisecs_store);
 344
 345static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 346                                          struct kobj_attribute *attr,
 347                                          char *buf)
 348{
 349        return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 350}
 351
 352static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 353                                           struct kobj_attribute *attr,
 354                                           const char *buf, size_t count)
 355{
 356        unsigned long msecs;
 357        int err;
 358
 359        err = strict_strtoul(buf, 10, &msecs);
 360        if (err || msecs > UINT_MAX)
 361                return -EINVAL;
 362
 363        khugepaged_alloc_sleep_millisecs = msecs;
 364        wake_up_interruptible(&khugepaged_wait);
 365
 366        return count;
 367}
 368static struct kobj_attribute alloc_sleep_millisecs_attr =
 369        __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 370               alloc_sleep_millisecs_store);
 371
 372static ssize_t pages_to_scan_show(struct kobject *kobj,
 373                                  struct kobj_attribute *attr,
 374                                  char *buf)
 375{
 376        return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 377}
 378static ssize_t pages_to_scan_store(struct kobject *kobj,
 379                                   struct kobj_attribute *attr,
 380                                   const char *buf, size_t count)
 381{
 382        int err;
 383        unsigned long pages;
 384
 385        err = strict_strtoul(buf, 10, &pages);
 386        if (err || !pages || pages > UINT_MAX)
 387                return -EINVAL;
 388
 389        khugepaged_pages_to_scan = pages;
 390
 391        return count;
 392}
 393static struct kobj_attribute pages_to_scan_attr =
 394        __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 395               pages_to_scan_store);
 396
 397static ssize_t pages_collapsed_show(struct kobject *kobj,
 398                                    struct kobj_attribute *attr,
 399                                    char *buf)
 400{
 401        return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 402}
 403static struct kobj_attribute pages_collapsed_attr =
 404        __ATTR_RO(pages_collapsed);
 405
 406static ssize_t full_scans_show(struct kobject *kobj,
 407                               struct kobj_attribute *attr,
 408                               char *buf)
 409{
 410        return sprintf(buf, "%u\n", khugepaged_full_scans);
 411}
 412static struct kobj_attribute full_scans_attr =
 413        __ATTR_RO(full_scans);
 414
 415static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 416                                      struct kobj_attribute *attr, char *buf)
 417{
 418        return single_flag_show(kobj, attr, buf,
 419                                TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 420}
 421static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 422                                       struct kobj_attribute *attr,
 423                                       const char *buf, size_t count)
 424{
 425        return single_flag_store(kobj, attr, buf, count,
 426                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 427}
 428static struct kobj_attribute khugepaged_defrag_attr =
 429        __ATTR(defrag, 0644, khugepaged_defrag_show,
 430               khugepaged_defrag_store);
 431
 432/*
 433 * max_ptes_none controls if khugepaged should collapse hugepages over
 434 * any unmapped ptes in turn potentially increasing the memory
 435 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 436 * reduce the available free memory in the system as it
 437 * runs. Increasing max_ptes_none will instead potentially reduce the
 438 * free memory in the system during the khugepaged scan.
 439 */
 440static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 441                                             struct kobj_attribute *attr,
 442                                             char *buf)
 443{
 444        return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 445}
 446static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 447                                              struct kobj_attribute *attr,
 448                                              const char *buf, size_t count)
 449{
 450        int err;
 451        unsigned long max_ptes_none;
 452
 453        err = strict_strtoul(buf, 10, &max_ptes_none);
 454        if (err || max_ptes_none > HPAGE_PMD_NR-1)
 455                return -EINVAL;
 456
 457        khugepaged_max_ptes_none = max_ptes_none;
 458
 459        return count;
 460}
 461static struct kobj_attribute khugepaged_max_ptes_none_attr =
 462        __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 463               khugepaged_max_ptes_none_store);
 464
 465static struct attribute *khugepaged_attr[] = {
 466        &khugepaged_defrag_attr.attr,
 467        &khugepaged_max_ptes_none_attr.attr,
 468        &pages_to_scan_attr.attr,
 469        &pages_collapsed_attr.attr,
 470        &full_scans_attr.attr,
 471        &scan_sleep_millisecs_attr.attr,
 472        &alloc_sleep_millisecs_attr.attr,
 473        NULL,
 474};
 475
 476static struct attribute_group khugepaged_attr_group = {
 477        .attrs = khugepaged_attr,
 478        .name = "khugepaged",
 479};
 480
 481static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 482{
 483        int err;
 484
 485        *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 486        if (unlikely(!*hugepage_kobj)) {
 487                printk(KERN_ERR "hugepage: failed kobject create\n");
 488                return -ENOMEM;
 489        }
 490
 491        err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 492        if (err) {
 493                printk(KERN_ERR "hugepage: failed register hugeage group\n");
 494                goto delete_obj;
 495        }
 496
 497        err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 498        if (err) {
 499                printk(KERN_ERR "hugepage: failed register hugeage group\n");
 500                goto remove_hp_group;
 501        }
 502
 503        return 0;
 504
 505remove_hp_group:
 506        sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 507delete_obj:
 508        kobject_put(*hugepage_kobj);
 509        return err;
 510}
 511
 512static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 513{
 514        sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 515        sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 516        kobject_put(hugepage_kobj);
 517}
 518#else
 519static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 520{
 521        return 0;
 522}
 523
 524static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 525{
 526}
 527#endif /* CONFIG_SYSFS */
 528
 529static int __init hugepage_init(void)
 530{
 531        int err;
 532        struct kobject *hugepage_kobj;
 533
 534        if (!has_transparent_hugepage()) {
 535                transparent_hugepage_flags = 0;
 536                return -EINVAL;
 537        }
 538
 539        err = hugepage_init_sysfs(&hugepage_kobj);
 540        if (err)
 541                return err;
 542
 543        err = khugepaged_slab_init();
 544        if (err)
 545                goto out;
 546
 547        err = mm_slots_hash_init();
 548        if (err) {
 549                khugepaged_slab_free();
 550                goto out;
 551        }
 552
 553        /*
 554         * By default disable transparent hugepages on smaller systems,
 555         * where the extra memory used could hurt more than TLB overhead
 556         * is likely to save.  The admin can still enable it through /sys.
 557         */
 558        if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
 559                transparent_hugepage_flags = 0;
 560
 561        start_khugepaged();
 562
 563        return 0;
 564out:
 565        hugepage_exit_sysfs(hugepage_kobj);
 566        return err;
 567}
 568module_init(hugepage_init)
 569
 570static int __init setup_transparent_hugepage(char *str)
 571{
 572        int ret = 0;
 573        if (!str)
 574                goto out;
 575        if (!strcmp(str, "always")) {
 576                set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 577                        &transparent_hugepage_flags);
 578                clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 579                          &transparent_hugepage_flags);
 580                ret = 1;
 581        } else if (!strcmp(str, "madvise")) {
 582                clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 583                          &transparent_hugepage_flags);
 584                set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 585                        &transparent_hugepage_flags);
 586                ret = 1;
 587        } else if (!strcmp(str, "never")) {
 588                clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 589                          &transparent_hugepage_flags);
 590                clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 591                          &transparent_hugepage_flags);
 592                ret = 1;
 593        }
 594out:
 595        if (!ret)
 596                printk(KERN_WARNING
 597                       "transparent_hugepage= cannot parse, ignored\n");
 598        return ret;
 599}
 600__setup("transparent_hugepage=", setup_transparent_hugepage);
 601
 602static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 603{
 604        if (likely(vma->vm_flags & VM_WRITE))
 605                pmd = pmd_mkwrite(pmd);
 606        return pmd;
 607}
 608
 609static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 610                                        struct vm_area_struct *vma,
 611                                        unsigned long haddr, pmd_t *pmd,
 612                                        struct page *page)
 613{
 614        pgtable_t pgtable;
 615
 616        VM_BUG_ON(!PageCompound(page));
 617        pgtable = pte_alloc_one(mm, haddr);
 618        if (unlikely(!pgtable))
 619                return VM_FAULT_OOM;
 620
 621        clear_huge_page(page, haddr, HPAGE_PMD_NR);
 622        __SetPageUptodate(page);
 623
 624        spin_lock(&mm->page_table_lock);
 625        if (unlikely(!pmd_none(*pmd))) {
 626                spin_unlock(&mm->page_table_lock);
 627                mem_cgroup_uncharge_page(page);
 628                put_page(page);
 629                pte_free(mm, pgtable);
 630        } else {
 631                pmd_t entry;
 632                entry = mk_pmd(page, vma->vm_page_prot);
 633                entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 634                entry = pmd_mkhuge(entry);
 635                /*
 636                 * The spinlocking to take the lru_lock inside
 637                 * page_add_new_anon_rmap() acts as a full memory
 638                 * barrier to be sure clear_huge_page writes become
 639                 * visible after the set_pmd_at() write.
 640                 */
 641                page_add_new_anon_rmap(page, vma, haddr);
 642                set_pmd_at(mm, haddr, pmd, entry);
 643                pgtable_trans_huge_deposit(mm, pgtable);
 644                add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 645                mm->nr_ptes++;
 646                spin_unlock(&mm->page_table_lock);
 647        }
 648
 649        return 0;
 650}
 651
 652static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 653{
 654        return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
 655}
 656
 657static inline struct page *alloc_hugepage_vma(int defrag,
 658                                              struct vm_area_struct *vma,
 659                                              unsigned long haddr, int nd,
 660                                              gfp_t extra_gfp)
 661{
 662        return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
 663                               HPAGE_PMD_ORDER, vma, haddr, nd);
 664}
 665
 666#ifndef CONFIG_NUMA
 667static inline struct page *alloc_hugepage(int defrag)
 668{
 669        return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
 670                           HPAGE_PMD_ORDER);
 671}
 672#endif
 673
 674int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 675                               unsigned long address, pmd_t *pmd,
 676                               unsigned int flags)
 677{
 678        struct page *page;
 679        unsigned long haddr = address & HPAGE_PMD_MASK;
 680        pte_t *pte;
 681
 682        if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
 683                if (unlikely(anon_vma_prepare(vma)))
 684                        return VM_FAULT_OOM;
 685                if (unlikely(khugepaged_enter(vma)))
 686                        return VM_FAULT_OOM;
 687                page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
 688                                          vma, haddr, numa_node_id(), 0);
 689                if (unlikely(!page)) {
 690                        count_vm_event(THP_FAULT_FALLBACK);
 691                        goto out;
 692                }
 693                count_vm_event(THP_FAULT_ALLOC);
 694                if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
 695                        put_page(page);
 696                        goto out;
 697                }
 698                if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
 699                                                          page))) {
 700                        mem_cgroup_uncharge_page(page);
 701                        put_page(page);
 702                        goto out;
 703                }
 704
 705                return 0;
 706        }
 707out:
 708        /*
 709         * Use __pte_alloc instead of pte_alloc_map, because we can't
 710         * run pte_offset_map on the pmd, if an huge pmd could
 711         * materialize from under us from a different thread.
 712         */
 713        if (unlikely(__pte_alloc(mm, vma, pmd, address)))
 714                return VM_FAULT_OOM;
 715        /* if an huge pmd materialized from under us just retry later */
 716        if (unlikely(pmd_trans_huge(*pmd)))
 717                return 0;
 718        /*
 719         * A regular pmd is established and it can't morph into a huge pmd
 720         * from under us anymore at this point because we hold the mmap_sem
 721         * read mode and khugepaged takes it in write mode. So now it's
 722         * safe to run pte_offset_map().
 723         */
 724        pte = pte_offset_map(pmd, address);
 725        return handle_pte_fault(mm, vma, address, pte, pmd, flags);
 726}
 727
 728int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 729                  pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 730                  struct vm_area_struct *vma)
 731{
 732        struct page *src_page;
 733        pmd_t pmd;
 734        pgtable_t pgtable;
 735        int ret;
 736
 737        ret = -ENOMEM;
 738        pgtable = pte_alloc_one(dst_mm, addr);
 739        if (unlikely(!pgtable))
 740                goto out;
 741
 742        spin_lock(&dst_mm->page_table_lock);
 743        spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
 744
 745        ret = -EAGAIN;
 746        pmd = *src_pmd;
 747        if (unlikely(!pmd_trans_huge(pmd))) {
 748                pte_free(dst_mm, pgtable);
 749                goto out_unlock;
 750        }
 751        if (unlikely(pmd_trans_splitting(pmd))) {
 752                /* split huge page running from under us */
 753                spin_unlock(&src_mm->page_table_lock);
 754                spin_unlock(&dst_mm->page_table_lock);
 755                pte_free(dst_mm, pgtable);
 756
 757                wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
 758                goto out;
 759        }
 760        src_page = pmd_page(pmd);
 761        VM_BUG_ON(!PageHead(src_page));
 762        get_page(src_page);
 763        page_dup_rmap(src_page);
 764        add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 765
 766        pmdp_set_wrprotect(src_mm, addr, src_pmd);
 767        pmd = pmd_mkold(pmd_wrprotect(pmd));
 768        set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 769        pgtable_trans_huge_deposit(dst_mm, pgtable);
 770        dst_mm->nr_ptes++;
 771
 772        ret = 0;
 773out_unlock:
 774        spin_unlock(&src_mm->page_table_lock);
 775        spin_unlock(&dst_mm->page_table_lock);
 776out:
 777        return ret;
 778}
 779
 780static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
 781                                        struct vm_area_struct *vma,
 782                                        unsigned long address,
 783                                        pmd_t *pmd, pmd_t orig_pmd,
 784                                        struct page *page,
 785                                        unsigned long haddr)
 786{
 787        pgtable_t pgtable;
 788        pmd_t _pmd;
 789        int ret = 0, i;
 790        struct page **pages;
 791        unsigned long mmun_start;       /* For mmu_notifiers */
 792        unsigned long mmun_end;         /* For mmu_notifiers */
 793
 794        pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
 795                        GFP_KERNEL);
 796        if (unlikely(!pages)) {
 797                ret |= VM_FAULT_OOM;
 798                goto out;
 799        }
 800
 801        for (i = 0; i < HPAGE_PMD_NR; i++) {
 802                pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
 803                                               __GFP_OTHER_NODE,
 804                                               vma, address, page_to_nid(page));
 805                if (unlikely(!pages[i] ||
 806                             mem_cgroup_newpage_charge(pages[i], mm,
 807                                                       GFP_KERNEL))) {
 808                        if (pages[i])
 809                                put_page(pages[i]);
 810                        mem_cgroup_uncharge_start();
 811                        while (--i >= 0) {
 812                                mem_cgroup_uncharge_page(pages[i]);
 813                                put_page(pages[i]);
 814                        }
 815                        mem_cgroup_uncharge_end();
 816                        kfree(pages);
 817                        ret |= VM_FAULT_OOM;
 818                        goto out;
 819                }
 820        }
 821
 822        for (i = 0; i < HPAGE_PMD_NR; i++) {
 823                copy_user_highpage(pages[i], page + i,
 824                                   haddr + PAGE_SIZE * i, vma);
 825                __SetPageUptodate(pages[i]);
 826                cond_resched();
 827        }
 828
 829        mmun_start = haddr;
 830        mmun_end   = haddr + HPAGE_PMD_SIZE;
 831        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 832
 833        spin_lock(&mm->page_table_lock);
 834        if (unlikely(!pmd_same(*pmd, orig_pmd)))
 835                goto out_free_pages;
 836        VM_BUG_ON(!PageHead(page));
 837
 838        pmdp_clear_flush(vma, haddr, pmd);
 839        /* leave pmd empty until pte is filled */
 840
 841        pgtable = pgtable_trans_huge_withdraw(mm);
 842        pmd_populate(mm, &_pmd, pgtable);
 843
 844        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
 845                pte_t *pte, entry;
 846                entry = mk_pte(pages[i], vma->vm_page_prot);
 847                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 848                page_add_new_anon_rmap(pages[i], vma, haddr);
 849                pte = pte_offset_map(&_pmd, haddr);
 850                VM_BUG_ON(!pte_none(*pte));
 851                set_pte_at(mm, haddr, pte, entry);
 852                pte_unmap(pte);
 853        }
 854        kfree(pages);
 855
 856        smp_wmb(); /* make pte visible before pmd */
 857        pmd_populate(mm, pmd, pgtable);
 858        page_remove_rmap(page);
 859        spin_unlock(&mm->page_table_lock);
 860
 861        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 862
 863        ret |= VM_FAULT_WRITE;
 864        put_page(page);
 865
 866out:
 867        return ret;
 868
 869out_free_pages:
 870        spin_unlock(&mm->page_table_lock);
 871        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 872        mem_cgroup_uncharge_start();
 873        for (i = 0; i < HPAGE_PMD_NR; i++) {
 874                mem_cgroup_uncharge_page(pages[i]);
 875                put_page(pages[i]);
 876        }
 877        mem_cgroup_uncharge_end();
 878        kfree(pages);
 879        goto out;
 880}
 881
 882int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 883                        unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
 884{
 885        int ret = 0;
 886        struct page *page, *new_page;
 887        unsigned long haddr;
 888        unsigned long mmun_start;       /* For mmu_notifiers */
 889        unsigned long mmun_end;         /* For mmu_notifiers */
 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_pmd(vma, address, pmd);
 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                if (ret & VM_FAULT_OOM)
 923                        split_huge_page(page);
 924                put_page(page);
 925                goto out;
 926        }
 927        count_vm_event(THP_FAULT_ALLOC);
 928
 929        if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
 930                put_page(new_page);
 931                split_huge_page(page);
 932                put_page(page);
 933                ret |= VM_FAULT_OOM;
 934                goto out;
 935        }
 936
 937        copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
 938        __SetPageUptodate(new_page);
 939
 940        mmun_start = haddr;
 941        mmun_end   = haddr + HPAGE_PMD_SIZE;
 942        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 943
 944        spin_lock(&mm->page_table_lock);
 945        put_page(page);
 946        if (unlikely(!pmd_same(*pmd, orig_pmd))) {
 947                spin_unlock(&mm->page_table_lock);
 948                mem_cgroup_uncharge_page(new_page);
 949                put_page(new_page);
 950                goto out_mn;
 951        } else {
 952                pmd_t entry;
 953                VM_BUG_ON(!PageHead(page));
 954                entry = mk_pmd(new_page, vma->vm_page_prot);
 955                entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 956                entry = pmd_mkhuge(entry);
 957                pmdp_clear_flush(vma, haddr, pmd);
 958                page_add_new_anon_rmap(new_page, vma, haddr);
 959                set_pmd_at(mm, haddr, pmd, entry);
 960                update_mmu_cache_pmd(vma, address, pmd);
 961                page_remove_rmap(page);
 962                put_page(page);
 963                ret |= VM_FAULT_WRITE;
 964        }
 965        spin_unlock(&mm->page_table_lock);
 966out_mn:
 967        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 968out:
 969        return ret;
 970out_unlock:
 971        spin_unlock(&mm->page_table_lock);
 972        return ret;
 973}
 974
 975struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
 976                                   unsigned long addr,
 977                                   pmd_t *pmd,
 978                                   unsigned int flags)
 979{
 980        struct mm_struct *mm = vma->vm_mm;
 981        struct page *page = NULL;
 982
 983        assert_spin_locked(&mm->page_table_lock);
 984
 985        if (flags & FOLL_WRITE && !pmd_write(*pmd))
 986                goto out;
 987
 988        page = pmd_page(*pmd);
 989        VM_BUG_ON(!PageHead(page));
 990        if (flags & FOLL_TOUCH) {
 991                pmd_t _pmd;
 992                /*
 993                 * We should set the dirty bit only for FOLL_WRITE but
 994                 * for now the dirty bit in the pmd is meaningless.
 995                 * And if the dirty bit will become meaningful and
 996                 * we'll only set it with FOLL_WRITE, an atomic
 997                 * set_bit will be required on the pmd to set the
 998                 * young bit, instead of the current set_pmd_at.
 999                 */
1000                _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1001                set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1002        }
1003        if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1004                if (page->mapping && trylock_page(page)) {
1005                        lru_add_drain();
1006                        if (page->mapping)
1007                                mlock_vma_page(page);
1008                        unlock_page(page);
1009                }
1010        }
1011        page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1012        VM_BUG_ON(!PageCompound(page));
1013        if (flags & FOLL_GET)
1014                get_page_foll(page);
1015
1016out:
1017        return page;
1018}
1019
1020int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1021                 pmd_t *pmd, unsigned long addr)
1022{
1023        int ret = 0;
1024
1025        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1026                struct page *page;
1027                pgtable_t pgtable;
1028                pmd_t orig_pmd;
1029                pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1030                orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1031                page = pmd_page(orig_pmd);
1032                tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1033                page_remove_rmap(page);
1034                VM_BUG_ON(page_mapcount(page) < 0);
1035                add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1036                VM_BUG_ON(!PageHead(page));
1037                tlb->mm->nr_ptes--;
1038                spin_unlock(&tlb->mm->page_table_lock);
1039                tlb_remove_page(tlb, page);
1040                pte_free(tlb->mm, pgtable);
1041                ret = 1;
1042        }
1043        return ret;
1044}
1045
1046int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1047                unsigned long addr, unsigned long end,
1048                unsigned char *vec)
1049{
1050        int ret = 0;
1051
1052        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1053                /*
1054                 * All logical pages in the range are present
1055                 * if backed by a huge page.
1056                 */
1057                spin_unlock(&vma->vm_mm->page_table_lock);
1058                memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1059                ret = 1;
1060        }
1061
1062        return ret;
1063}
1064
1065int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1066                  unsigned long old_addr,
1067                  unsigned long new_addr, unsigned long old_end,
1068                  pmd_t *old_pmd, pmd_t *new_pmd)
1069{
1070        int ret = 0;
1071        pmd_t pmd;
1072
1073        struct mm_struct *mm = vma->vm_mm;
1074
1075        if ((old_addr & ~HPAGE_PMD_MASK) ||
1076            (new_addr & ~HPAGE_PMD_MASK) ||
1077            old_end - old_addr < HPAGE_PMD_SIZE ||
1078            (new_vma->vm_flags & VM_NOHUGEPAGE))
1079                goto out;
1080
1081        /*
1082         * The destination pmd shouldn't be established, free_pgtables()
1083         * should have release it.
1084         */
1085        if (WARN_ON(!pmd_none(*new_pmd))) {
1086                VM_BUG_ON(pmd_trans_huge(*new_pmd));
1087                goto out;
1088        }
1089
1090        ret = __pmd_trans_huge_lock(old_pmd, vma);
1091        if (ret == 1) {
1092                pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1093                VM_BUG_ON(!pmd_none(*new_pmd));
1094                set_pmd_at(mm, new_addr, new_pmd, pmd);
1095                spin_unlock(&mm->page_table_lock);
1096        }
1097out:
1098        return ret;
1099}
1100
1101int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1102                unsigned long addr, pgprot_t newprot)
1103{
1104        struct mm_struct *mm = vma->vm_mm;
1105        int ret = 0;
1106
1107        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1108                pmd_t entry;
1109                entry = pmdp_get_and_clear(mm, addr, pmd);
1110                entry = pmd_modify(entry, newprot);
1111                set_pmd_at(mm, addr, pmd, entry);
1112                spin_unlock(&vma->vm_mm->page_table_lock);
1113                ret = 1;
1114        }
1115
1116        return ret;
1117}
1118
1119/*
1120 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1121 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1122 *
1123 * Note that if it returns 1, this routine returns without unlocking page
1124 * table locks. So callers must unlock them.
1125 */
1126int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1127{
1128        spin_lock(&vma->vm_mm->page_table_lock);
1129        if (likely(pmd_trans_huge(*pmd))) {
1130                if (unlikely(pmd_trans_splitting(*pmd))) {
1131                        spin_unlock(&vma->vm_mm->page_table_lock);
1132                        wait_split_huge_page(vma->anon_vma, pmd);
1133                        return -1;
1134                } else {
1135                        /* Thp mapped by 'pmd' is stable, so we can
1136                         * handle it as it is. */
1137                        return 1;
1138                }
1139        }
1140        spin_unlock(&vma->vm_mm->page_table_lock);
1141        return 0;
1142}
1143
1144pmd_t *page_check_address_pmd(struct page *page,
1145                              struct mm_struct *mm,
1146                              unsigned long address,
1147                              enum page_check_address_pmd_flag flag)
1148{
1149        pgd_t *pgd;
1150        pud_t *pud;
1151        pmd_t *pmd, *ret = NULL;
1152
1153        if (address & ~HPAGE_PMD_MASK)
1154                goto out;
1155
1156        pgd = pgd_offset(mm, address);
1157        if (!pgd_present(*pgd))
1158                goto out;
1159
1160        pud = pud_offset(pgd, address);
1161        if (!pud_present(*pud))
1162                goto out;
1163
1164        pmd = pmd_offset(pud, address);
1165        if (pmd_none(*pmd))
1166                goto out;
1167        if (pmd_page(*pmd) != page)
1168                goto out;
1169        /*
1170         * split_vma() may create temporary aliased mappings. There is
1171         * no risk as long as all huge pmd are found and have their
1172         * splitting bit set before __split_huge_page_refcount
1173         * runs. Finding the same huge pmd more than once during the
1174         * same rmap walk is not a problem.
1175         */
1176        if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1177            pmd_trans_splitting(*pmd))
1178                goto out;
1179        if (pmd_trans_huge(*pmd)) {
1180                VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1181                          !pmd_trans_splitting(*pmd));
1182                ret = pmd;
1183        }
1184out:
1185        return ret;
1186}
1187
1188static int __split_huge_page_splitting(struct page *page,
1189                                       struct vm_area_struct *vma,
1190                                       unsigned long address)
1191{
1192        struct mm_struct *mm = vma->vm_mm;
1193        pmd_t *pmd;
1194        int ret = 0;
1195        /* For mmu_notifiers */
1196        const unsigned long mmun_start = address;
1197        const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1198
1199        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1200        spin_lock(&mm->page_table_lock);
1201        pmd = page_check_address_pmd(page, mm, address,
1202                                     PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1203        if (pmd) {
1204                /*
1205                 * We can't temporarily set the pmd to null in order
1206                 * to split it, the pmd must remain marked huge at all
1207                 * times or the VM won't take the pmd_trans_huge paths
1208                 * and it won't wait on the anon_vma->root->mutex to
1209                 * serialize against split_huge_page*.
1210                 */
1211                pmdp_splitting_flush(vma, address, pmd);
1212                ret = 1;
1213        }
1214        spin_unlock(&mm->page_table_lock);
1215        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1216
1217        return ret;
1218}
1219
1220static void __split_huge_page_refcount(struct page *page)
1221{
1222        int i;
1223        struct zone *zone = page_zone(page);
1224        struct lruvec *lruvec;
1225        int tail_count = 0;
1226
1227        /* prevent PageLRU to go away from under us, and freeze lru stats */
1228        spin_lock_irq(&zone->lru_lock);
1229        lruvec = mem_cgroup_page_lruvec(page, zone);
1230
1231        compound_lock(page);
1232        /* complete memcg works before add pages to LRU */
1233        mem_cgroup_split_huge_fixup(page);
1234
1235        for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1236                struct page *page_tail = page + i;
1237
1238                /* tail_page->_mapcount cannot change */
1239                BUG_ON(page_mapcount(page_tail) < 0);
1240                tail_count += page_mapcount(page_tail);
1241                /* check for overflow */
1242                BUG_ON(tail_count < 0);
1243                BUG_ON(atomic_read(&page_tail->_count) != 0);
1244                /*
1245                 * tail_page->_count is zero and not changing from
1246                 * under us. But get_page_unless_zero() may be running
1247                 * from under us on the tail_page. If we used
1248                 * atomic_set() below instead of atomic_add(), we
1249                 * would then run atomic_set() concurrently with
1250                 * get_page_unless_zero(), and atomic_set() is
1251                 * implemented in C not using locked ops. spin_unlock
1252                 * on x86 sometime uses locked ops because of PPro
1253                 * errata 66, 92, so unless somebody can guarantee
1254                 * atomic_set() here would be safe on all archs (and
1255                 * not only on x86), it's safer to use atomic_add().
1256                 */
1257                atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1258                           &page_tail->_count);
1259
1260                /* after clearing PageTail the gup refcount can be released */
1261                smp_mb();
1262
1263                /*
1264                 * retain hwpoison flag of the poisoned tail page:
1265                 *   fix for the unsuitable process killed on Guest Machine(KVM)
1266                 *   by the memory-failure.
1267                 */
1268                page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1269                page_tail->flags |= (page->flags &
1270                                     ((1L << PG_referenced) |
1271                                      (1L << PG_swapbacked) |
1272                                      (1L << PG_mlocked) |
1273                                      (1L << PG_uptodate)));
1274                page_tail->flags |= (1L << PG_dirty);
1275
1276                /* clear PageTail before overwriting first_page */
1277                smp_wmb();
1278
1279                /*
1280                 * __split_huge_page_splitting() already set the
1281                 * splitting bit in all pmd that could map this
1282                 * hugepage, that will ensure no CPU can alter the
1283                 * mapcount on the head page. The mapcount is only
1284                 * accounted in the head page and it has to be
1285                 * transferred to all tail pages in the below code. So
1286                 * for this code to be safe, the split the mapcount
1287                 * can't change. But that doesn't mean userland can't
1288                 * keep changing and reading the page contents while
1289                 * we transfer the mapcount, so the pmd splitting
1290                 * status is achieved setting a reserved bit in the
1291                 * pmd, not by clearing the present bit.
1292                */
1293                page_tail->_mapcount = page->_mapcount;
1294
1295                BUG_ON(page_tail->mapping);
1296                page_tail->mapping = page->mapping;
1297
1298                page_tail->index = page->index + i;
1299
1300                BUG_ON(!PageAnon(page_tail));
1301                BUG_ON(!PageUptodate(page_tail));
1302                BUG_ON(!PageDirty(page_tail));
1303                BUG_ON(!PageSwapBacked(page_tail));
1304
1305                lru_add_page_tail(page, page_tail, lruvec);
1306        }
1307        atomic_sub(tail_count, &page->_count);
1308        BUG_ON(atomic_read(&page->_count) <= 0);
1309
1310        __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1311        __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1312
1313        ClearPageCompound(page);
1314        compound_unlock(page);
1315        spin_unlock_irq(&zone->lru_lock);
1316
1317        for (i = 1; i < HPAGE_PMD_NR; i++) {
1318                struct page *page_tail = page + i;
1319                BUG_ON(page_count(page_tail) <= 0);
1320                /*
1321                 * Tail pages may be freed if there wasn't any mapping
1322                 * like if add_to_swap() is running on a lru page that
1323                 * had its mapping zapped. And freeing these pages
1324                 * requires taking the lru_lock so we do the put_page
1325                 * of the tail pages after the split is complete.
1326                 */
1327                put_page(page_tail);
1328        }
1329
1330        /*
1331         * Only the head page (now become a regular page) is required
1332         * to be pinned by the caller.
1333         */
1334        BUG_ON(page_count(page) <= 0);
1335}
1336
1337static int __split_huge_page_map(struct page *page,
1338                                 struct vm_area_struct *vma,
1339                                 unsigned long address)
1340{
1341        struct mm_struct *mm = vma->vm_mm;
1342        pmd_t *pmd, _pmd;
1343        int ret = 0, i;
1344        pgtable_t pgtable;
1345        unsigned long haddr;
1346
1347        spin_lock(&mm->page_table_lock);
1348        pmd = page_check_address_pmd(page, mm, address,
1349                                     PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1350        if (pmd) {
1351                pgtable = pgtable_trans_huge_withdraw(mm);
1352                pmd_populate(mm, &_pmd, pgtable);
1353
1354                haddr = address;
1355                for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1356                        pte_t *pte, entry;
1357                        BUG_ON(PageCompound(page+i));
1358                        entry = mk_pte(page + i, vma->vm_page_prot);
1359                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1360                        if (!pmd_write(*pmd))
1361                                entry = pte_wrprotect(entry);
1362                        else
1363                                BUG_ON(page_mapcount(page) != 1);
1364                        if (!pmd_young(*pmd))
1365                                entry = pte_mkold(entry);
1366                        pte = pte_offset_map(&_pmd, haddr);
1367                        BUG_ON(!pte_none(*pte));
1368                        set_pte_at(mm, haddr, pte, entry);
1369                        pte_unmap(pte);
1370                }
1371
1372                smp_wmb(); /* make pte visible before pmd */
1373                /*
1374                 * Up to this point the pmd is present and huge and
1375                 * userland has the whole access to the hugepage
1376                 * during the split (which happens in place). If we
1377                 * overwrite the pmd with the not-huge version
1378                 * pointing to the pte here (which of course we could
1379                 * if all CPUs were bug free), userland could trigger
1380                 * a small page size TLB miss on the small sized TLB
1381                 * while the hugepage TLB entry is still established
1382                 * in the huge TLB. Some CPU doesn't like that. See
1383                 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1384                 * Erratum 383 on page 93. Intel should be safe but is
1385                 * also warns that it's only safe if the permission
1386                 * and cache attributes of the two entries loaded in
1387                 * the two TLB is identical (which should be the case
1388                 * here). But it is generally safer to never allow
1389                 * small and huge TLB entries for the same virtual
1390                 * address to be loaded simultaneously. So instead of
1391                 * doing "pmd_populate(); flush_tlb_range();" we first
1392                 * mark the current pmd notpresent (atomically because
1393                 * here the pmd_trans_huge and pmd_trans_splitting
1394                 * must remain set at all times on the pmd until the
1395                 * split is complete for this pmd), then we flush the
1396                 * SMP TLB and finally we write the non-huge version
1397                 * of the pmd entry with pmd_populate.
1398                 */
1399                pmdp_invalidate(vma, address, pmd);
1400                pmd_populate(mm, pmd, pgtable);
1401                ret = 1;
1402        }
1403        spin_unlock(&mm->page_table_lock);
1404
1405        return ret;
1406}
1407
1408/* must be called with anon_vma->root->mutex hold */
1409static void __split_huge_page(struct page *page,
1410                              struct anon_vma *anon_vma)
1411{
1412        int mapcount, mapcount2;
1413        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1414        struct anon_vma_chain *avc;
1415
1416        BUG_ON(!PageHead(page));
1417        BUG_ON(PageTail(page));
1418
1419        mapcount = 0;
1420        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1421                struct vm_area_struct *vma = avc->vma;
1422                unsigned long addr = vma_address(page, vma);
1423                BUG_ON(is_vma_temporary_stack(vma));
1424                mapcount += __split_huge_page_splitting(page, vma, addr);
1425        }
1426        /*
1427         * It is critical that new vmas are added to the tail of the
1428         * anon_vma list. This guarantes that if copy_huge_pmd() runs
1429         * and establishes a child pmd before
1430         * __split_huge_page_splitting() freezes the parent pmd (so if
1431         * we fail to prevent copy_huge_pmd() from running until the
1432         * whole __split_huge_page() is complete), we will still see
1433         * the newly established pmd of the child later during the
1434         * walk, to be able to set it as pmd_trans_splitting too.
1435         */
1436        if (mapcount != page_mapcount(page))
1437                printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1438                       mapcount, page_mapcount(page));
1439        BUG_ON(mapcount != page_mapcount(page));
1440
1441        __split_huge_page_refcount(page);
1442
1443        mapcount2 = 0;
1444        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1445                struct vm_area_struct *vma = avc->vma;
1446                unsigned long addr = vma_address(page, vma);
1447                BUG_ON(is_vma_temporary_stack(vma));
1448                mapcount2 += __split_huge_page_map(page, vma, addr);
1449        }
1450        if (mapcount != mapcount2)
1451                printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1452                       mapcount, mapcount2, page_mapcount(page));
1453        BUG_ON(mapcount != mapcount2);
1454}
1455
1456int split_huge_page(struct page *page)
1457{
1458        struct anon_vma *anon_vma;
1459        int ret = 1;
1460
1461        BUG_ON(!PageAnon(page));
1462        anon_vma = page_lock_anon_vma(page);
1463        if (!anon_vma)
1464                goto out;
1465        ret = 0;
1466        if (!PageCompound(page))
1467                goto out_unlock;
1468
1469        BUG_ON(!PageSwapBacked(page));
1470        __split_huge_page(page, anon_vma);
1471        count_vm_event(THP_SPLIT);
1472
1473        BUG_ON(PageCompound(page));
1474out_unlock:
1475        page_unlock_anon_vma(anon_vma);
1476out:
1477        return ret;
1478}
1479
1480#define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1481
1482int hugepage_madvise(struct vm_area_struct *vma,
1483                     unsigned long *vm_flags, int advice)
1484{
1485        struct mm_struct *mm = vma->vm_mm;
1486
1487        switch (advice) {
1488        case MADV_HUGEPAGE:
1489                /*
1490                 * Be somewhat over-protective like KSM for now!
1491                 */
1492                if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1493                        return -EINVAL;
1494                if (mm->def_flags & VM_NOHUGEPAGE)
1495                        return -EINVAL;
1496                *vm_flags &= ~VM_NOHUGEPAGE;
1497                *vm_flags |= VM_HUGEPAGE;
1498                /*
1499                 * If the vma become good for khugepaged to scan,
1500                 * register it here without waiting a page fault that
1501                 * may not happen any time soon.
1502                 */
1503                if (unlikely(khugepaged_enter_vma_merge(vma)))
1504                        return -ENOMEM;
1505                break;
1506        case MADV_NOHUGEPAGE:
1507                /*
1508                 * Be somewhat over-protective like KSM for now!
1509                 */
1510                if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1511                        return -EINVAL;
1512                *vm_flags &= ~VM_HUGEPAGE;
1513                *vm_flags |= VM_NOHUGEPAGE;
1514                /*
1515                 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1516                 * this vma even if we leave the mm registered in khugepaged if
1517                 * it got registered before VM_NOHUGEPAGE was set.
1518                 */
1519                break;
1520        }
1521
1522        return 0;
1523}
1524
1525static int __init khugepaged_slab_init(void)
1526{
1527        mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1528                                          sizeof(struct mm_slot),
1529                                          __alignof__(struct mm_slot), 0, NULL);
1530        if (!mm_slot_cache)
1531                return -ENOMEM;
1532
1533        return 0;
1534}
1535
1536static void __init khugepaged_slab_free(void)
1537{
1538        kmem_cache_destroy(mm_slot_cache);
1539        mm_slot_cache = NULL;
1540}
1541
1542static inline struct mm_slot *alloc_mm_slot(void)
1543{
1544        if (!mm_slot_cache)     /* initialization failed */
1545                return NULL;
1546        return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1547}
1548
1549static inline void free_mm_slot(struct mm_slot *mm_slot)
1550{
1551        kmem_cache_free(mm_slot_cache, mm_slot);
1552}
1553
1554static int __init mm_slots_hash_init(void)
1555{
1556        mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1557                                GFP_KERNEL);
1558        if (!mm_slots_hash)
1559                return -ENOMEM;
1560        return 0;
1561}
1562
1563#if 0
1564static void __init mm_slots_hash_free(void)
1565{
1566        kfree(mm_slots_hash);
1567        mm_slots_hash = NULL;
1568}
1569#endif
1570
1571static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1572{
1573        struct mm_slot *mm_slot;
1574        struct hlist_head *bucket;
1575        struct hlist_node *node;
1576
1577        bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1578                                % MM_SLOTS_HASH_HEADS];
1579        hlist_for_each_entry(mm_slot, node, bucket, hash) {
1580                if (mm == mm_slot->mm)
1581                        return mm_slot;
1582        }
1583        return NULL;
1584}
1585
1586static void insert_to_mm_slots_hash(struct mm_struct *mm,
1587                                    struct mm_slot *mm_slot)
1588{
1589        struct hlist_head *bucket;
1590
1591        bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1592                                % MM_SLOTS_HASH_HEADS];
1593        mm_slot->mm = mm;
1594        hlist_add_head(&mm_slot->hash, bucket);
1595}
1596
1597static inline int khugepaged_test_exit(struct mm_struct *mm)
1598{
1599        return atomic_read(&mm->mm_users) == 0;
1600}
1601
1602int __khugepaged_enter(struct mm_struct *mm)
1603{
1604        struct mm_slot *mm_slot;
1605        int wakeup;
1606
1607        mm_slot = alloc_mm_slot();
1608        if (!mm_slot)
1609                return -ENOMEM;
1610
1611        /* __khugepaged_exit() must not run from under us */
1612        VM_BUG_ON(khugepaged_test_exit(mm));
1613        if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1614                free_mm_slot(mm_slot);
1615                return 0;
1616        }
1617
1618        spin_lock(&khugepaged_mm_lock);
1619        insert_to_mm_slots_hash(mm, mm_slot);
1620        /*
1621         * Insert just behind the scanning cursor, to let the area settle
1622         * down a little.
1623         */
1624        wakeup = list_empty(&khugepaged_scan.mm_head);
1625        list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1626        spin_unlock(&khugepaged_mm_lock);
1627
1628        atomic_inc(&mm->mm_count);
1629        if (wakeup)
1630                wake_up_interruptible(&khugepaged_wait);
1631
1632        return 0;
1633}
1634
1635int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1636{
1637        unsigned long hstart, hend;
1638        if (!vma->anon_vma)
1639                /*
1640                 * Not yet faulted in so we will register later in the
1641                 * page fault if needed.
1642                 */
1643                return 0;
1644        if (vma->vm_ops)
1645                /* khugepaged not yet working on file or special mappings */
1646                return 0;
1647        VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1648        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1649        hend = vma->vm_end & HPAGE_PMD_MASK;
1650        if (hstart < hend)
1651                return khugepaged_enter(vma);
1652        return 0;
1653}
1654
1655void __khugepaged_exit(struct mm_struct *mm)
1656{
1657        struct mm_slot *mm_slot;
1658        int free = 0;
1659
1660        spin_lock(&khugepaged_mm_lock);
1661        mm_slot = get_mm_slot(mm);
1662        if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1663                hlist_del(&mm_slot->hash);
1664                list_del(&mm_slot->mm_node);
1665                free = 1;
1666        }
1667        spin_unlock(&khugepaged_mm_lock);
1668
1669        if (free) {
1670                clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1671                free_mm_slot(mm_slot);
1672                mmdrop(mm);
1673        } else if (mm_slot) {
1674                /*
1675                 * This is required to serialize against
1676                 * khugepaged_test_exit() (which is guaranteed to run
1677                 * under mmap sem read mode). Stop here (after we
1678                 * return all pagetables will be destroyed) until
1679                 * khugepaged has finished working on the pagetables
1680                 * under the mmap_sem.
1681                 */
1682                down_write(&mm->mmap_sem);
1683                up_write(&mm->mmap_sem);
1684        }
1685}
1686
1687static void release_pte_page(struct page *page)
1688{
1689        /* 0 stands for page_is_file_cache(page) == false */
1690        dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1691        unlock_page(page);
1692        putback_lru_page(page);
1693}
1694
1695static void release_pte_pages(pte_t *pte, pte_t *_pte)
1696{
1697        while (--_pte >= pte) {
1698                pte_t pteval = *_pte;
1699                if (!pte_none(pteval))
1700                        release_pte_page(pte_page(pteval));
1701        }
1702}
1703
1704static void release_all_pte_pages(pte_t *pte)
1705{
1706        release_pte_pages(pte, pte + HPAGE_PMD_NR);
1707}
1708
1709static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1710                                        unsigned long address,
1711                                        pte_t *pte)
1712{
1713        struct page *page;
1714        pte_t *_pte;
1715        int referenced = 0, isolated = 0, none = 0;
1716        for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1717             _pte++, address += PAGE_SIZE) {
1718                pte_t pteval = *_pte;
1719                if (pte_none(pteval)) {
1720                        if (++none <= khugepaged_max_ptes_none)
1721                                continue;
1722                        else {
1723                                release_pte_pages(pte, _pte);
1724                                goto out;
1725                        }
1726                }
1727                if (!pte_present(pteval) || !pte_write(pteval)) {
1728                        release_pte_pages(pte, _pte);
1729                        goto out;
1730                }
1731                page = vm_normal_page(vma, address, pteval);
1732                if (unlikely(!page)) {
1733                        release_pte_pages(pte, _pte);
1734                        goto out;
1735                }
1736                VM_BUG_ON(PageCompound(page));
1737                BUG_ON(!PageAnon(page));
1738                VM_BUG_ON(!PageSwapBacked(page));
1739
1740                /* cannot use mapcount: can't collapse if there's a gup pin */
1741                if (page_count(page) != 1) {
1742                        release_pte_pages(pte, _pte);
1743                        goto out;
1744                }
1745                /*
1746                 * We can do it before isolate_lru_page because the
1747                 * page can't be freed from under us. NOTE: PG_lock
1748                 * is needed to serialize against split_huge_page
1749                 * when invoked from the VM.
1750                 */
1751                if (!trylock_page(page)) {
1752                        release_pte_pages(pte, _pte);
1753                        goto out;
1754                }
1755                /*
1756                 * Isolate the page to avoid collapsing an hugepage
1757                 * currently in use by the VM.
1758                 */
1759                if (isolate_lru_page(page)) {
1760                        unlock_page(page);
1761                        release_pte_pages(pte, _pte);
1762                        goto out;
1763                }
1764                /* 0 stands for page_is_file_cache(page) == false */
1765                inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1766                VM_BUG_ON(!PageLocked(page));
1767                VM_BUG_ON(PageLRU(page));
1768
1769                /* If there is no mapped pte young don't collapse the page */
1770                if (pte_young(pteval) || PageReferenced(page) ||
1771                    mmu_notifier_test_young(vma->vm_mm, address))
1772                        referenced = 1;
1773        }
1774        if (unlikely(!referenced))
1775                release_all_pte_pages(pte);
1776        else
1777                isolated = 1;
1778out:
1779        return isolated;
1780}
1781
1782static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1783                                      struct vm_area_struct *vma,
1784                                      unsigned long address,
1785                                      spinlock_t *ptl)
1786{
1787        pte_t *_pte;
1788        for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1789                pte_t pteval = *_pte;
1790                struct page *src_page;
1791
1792                if (pte_none(pteval)) {
1793                        clear_user_highpage(page, address);
1794                        add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1795                } else {
1796                        src_page = pte_page(pteval);
1797                        copy_user_highpage(page, src_page, address, vma);
1798                        VM_BUG_ON(page_mapcount(src_page) != 1);
1799                        release_pte_page(src_page);
1800                        /*
1801                         * ptl mostly unnecessary, but preempt has to
1802                         * be disabled to update the per-cpu stats
1803                         * inside page_remove_rmap().
1804                         */
1805                        spin_lock(ptl);
1806                        /*
1807                         * paravirt calls inside pte_clear here are
1808                         * superfluous.
1809                         */
1810                        pte_clear(vma->vm_mm, address, _pte);
1811                        page_remove_rmap(src_page);
1812                        spin_unlock(ptl);
1813                        free_page_and_swap_cache(src_page);
1814                }
1815
1816                address += PAGE_SIZE;
1817                page++;
1818        }
1819}
1820
1821static void khugepaged_alloc_sleep(void)
1822{
1823        wait_event_freezable_timeout(khugepaged_wait, false,
1824                        msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
1825}
1826
1827#ifdef CONFIG_NUMA
1828static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
1829{
1830        if (IS_ERR(*hpage)) {
1831                if (!*wait)
1832                        return false;
1833
1834                *wait = false;
1835                *hpage = NULL;
1836                khugepaged_alloc_sleep();
1837        } else if (*hpage) {
1838                put_page(*hpage);
1839                *hpage = NULL;
1840        }
1841
1842        return true;
1843}
1844
1845static struct page
1846*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
1847                       struct vm_area_struct *vma, unsigned long address,
1848                       int node)
1849{
1850        VM_BUG_ON(*hpage);
1851        /*
1852         * Allocate the page while the vma is still valid and under
1853         * the mmap_sem read mode so there is no memory allocation
1854         * later when we take the mmap_sem in write mode. This is more
1855         * friendly behavior (OTOH it may actually hide bugs) to
1856         * filesystems in userland with daemons allocating memory in
1857         * the userland I/O paths.  Allocating memory with the
1858         * mmap_sem in read mode is good idea also to allow greater
1859         * scalability.
1860         */
1861        *hpage  = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1862                                      node, __GFP_OTHER_NODE);
1863
1864        /*
1865         * After allocating the hugepage, release the mmap_sem read lock in
1866         * preparation for taking it in write mode.
1867         */
1868        up_read(&mm->mmap_sem);
1869        if (unlikely(!*hpage)) {
1870                count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1871                *hpage = ERR_PTR(-ENOMEM);
1872                return NULL;
1873        }
1874
1875        count_vm_event(THP_COLLAPSE_ALLOC);
1876        return *hpage;
1877}
1878#else
1879static struct page *khugepaged_alloc_hugepage(bool *wait)
1880{
1881        struct page *hpage;
1882
1883        do {
1884                hpage = alloc_hugepage(khugepaged_defrag());
1885                if (!hpage) {
1886                        count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1887                        if (!*wait)
1888                                return NULL;
1889
1890                        *wait = false;
1891                        khugepaged_alloc_sleep();
1892                } else
1893                        count_vm_event(THP_COLLAPSE_ALLOC);
1894        } while (unlikely(!hpage) && likely(khugepaged_enabled()));
1895
1896        return hpage;
1897}
1898
1899static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
1900{
1901        if (!*hpage)
1902                *hpage = khugepaged_alloc_hugepage(wait);
1903
1904        if (unlikely(!*hpage))
1905                return false;
1906
1907        return true;
1908}
1909
1910static struct page
1911*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
1912                       struct vm_area_struct *vma, unsigned long address,
1913                       int node)
1914{
1915        up_read(&mm->mmap_sem);
1916        VM_BUG_ON(!*hpage);
1917        return  *hpage;
1918}
1919#endif
1920
1921static void collapse_huge_page(struct mm_struct *mm,
1922                                   unsigned long address,
1923                                   struct page **hpage,
1924                                   struct vm_area_struct *vma,
1925                                   int node)
1926{
1927        pgd_t *pgd;
1928        pud_t *pud;
1929        pmd_t *pmd, _pmd;
1930        pte_t *pte;
1931        pgtable_t pgtable;
1932        struct page *new_page;
1933        spinlock_t *ptl;
1934        int isolated;
1935        unsigned long hstart, hend;
1936        unsigned long mmun_start;       /* For mmu_notifiers */
1937        unsigned long mmun_end;         /* For mmu_notifiers */
1938
1939        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1940
1941        /* release the mmap_sem read lock. */
1942        new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
1943        if (!new_page)
1944                return;
1945
1946        if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
1947                return;
1948
1949        /*
1950         * Prevent all access to pagetables with the exception of
1951         * gup_fast later hanlded by the ptep_clear_flush and the VM
1952         * handled by the anon_vma lock + PG_lock.
1953         */
1954        down_write(&mm->mmap_sem);
1955        if (unlikely(khugepaged_test_exit(mm)))
1956                goto out;
1957
1958        vma = find_vma(mm, address);
1959        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1960        hend = vma->vm_end & HPAGE_PMD_MASK;
1961        if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1962                goto out;
1963
1964        if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1965            (vma->vm_flags & VM_NOHUGEPAGE))
1966                goto out;
1967
1968        if (!vma->anon_vma || vma->vm_ops)
1969                goto out;
1970        if (is_vma_temporary_stack(vma))
1971                goto out;
1972        VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1973
1974        pgd = pgd_offset(mm, address);
1975        if (!pgd_present(*pgd))
1976                goto out;
1977
1978        pud = pud_offset(pgd, address);
1979        if (!pud_present(*pud))
1980                goto out;
1981
1982        pmd = pmd_offset(pud, address);
1983        /* pmd can't go away or become huge under us */
1984        if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1985                goto out;
1986
1987        anon_vma_lock(vma->anon_vma);
1988
1989        pte = pte_offset_map(pmd, address);
1990        ptl = pte_lockptr(mm, pmd);
1991
1992        mmun_start = address;
1993        mmun_end   = address + HPAGE_PMD_SIZE;
1994        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1995        spin_lock(&mm->page_table_lock); /* probably unnecessary */
1996        /*
1997         * After this gup_fast can't run anymore. This also removes
1998         * any huge TLB entry from the CPU so we won't allow
1999         * huge and small TLB entries for the same virtual address
2000         * to avoid the risk of CPU bugs in that area.
2001         */
2002        _pmd = pmdp_clear_flush(vma, address, pmd);
2003        spin_unlock(&mm->page_table_lock);
2004        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2005
2006        spin_lock(ptl);
2007        isolated = __collapse_huge_page_isolate(vma, address, pte);
2008        spin_unlock(ptl);
2009
2010        if (unlikely(!isolated)) {
2011                pte_unmap(pte);
2012                spin_lock(&mm->page_table_lock);
2013                BUG_ON(!pmd_none(*pmd));
2014                set_pmd_at(mm, address, pmd, _pmd);
2015                spin_unlock(&mm->page_table_lock);
2016                anon_vma_unlock(vma->anon_vma);
2017                goto out;
2018        }
2019
2020        /*
2021         * All pages are isolated and locked so anon_vma rmap
2022         * can't run anymore.
2023         */
2024        anon_vma_unlock(vma->anon_vma);
2025
2026        __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2027        pte_unmap(pte);
2028        __SetPageUptodate(new_page);
2029        pgtable = pmd_pgtable(_pmd);
2030
2031        _pmd = mk_pmd(new_page, vma->vm_page_prot);
2032        _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2033        _pmd = pmd_mkhuge(_pmd);
2034
2035        /*
2036         * spin_lock() below is not the equivalent of smp_wmb(), so
2037         * this is needed to avoid the copy_huge_page writes to become
2038         * visible after the set_pmd_at() write.
2039         */
2040        smp_wmb();
2041
2042        spin_lock(&mm->page_table_lock);
2043        BUG_ON(!pmd_none(*pmd));
2044        page_add_new_anon_rmap(new_page, vma, address);
2045        set_pmd_at(mm, address, pmd, _pmd);
2046        update_mmu_cache_pmd(vma, address, pmd);
2047        pgtable_trans_huge_deposit(mm, pgtable);
2048        spin_unlock(&mm->page_table_lock);
2049
2050        *hpage = NULL;
2051
2052        khugepaged_pages_collapsed++;
2053out_up_write:
2054        up_write(&mm->mmap_sem);
2055        return;
2056
2057out:
2058        mem_cgroup_uncharge_page(new_page);
2059        goto out_up_write;
2060}
2061
2062static int khugepaged_scan_pmd(struct mm_struct *mm,
2063                               struct vm_area_struct *vma,
2064                               unsigned long address,
2065                               struct page **hpage)
2066{
2067        pgd_t *pgd;
2068        pud_t *pud;
2069        pmd_t *pmd;
2070        pte_t *pte, *_pte;
2071        int ret = 0, referenced = 0, none = 0;
2072        struct page *page;
2073        unsigned long _address;
2074        spinlock_t *ptl;
2075        int node = -1;
2076
2077        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2078
2079        pgd = pgd_offset(mm, address);
2080        if (!pgd_present(*pgd))
2081                goto out;
2082
2083        pud = pud_offset(pgd, address);
2084        if (!pud_present(*pud))
2085                goto out;
2086
2087        pmd = pmd_offset(pud, address);
2088        if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
2089                goto out;
2090
2091        pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2092        for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2093             _pte++, _address += PAGE_SIZE) {
2094                pte_t pteval = *_pte;
2095                if (pte_none(pteval)) {
2096                        if (++none <= khugepaged_max_ptes_none)
2097                                continue;
2098                        else
2099                                goto out_unmap;
2100                }
2101                if (!pte_present(pteval) || !pte_write(pteval))
2102                        goto out_unmap;
2103                page = vm_normal_page(vma, _address, pteval);
2104                if (unlikely(!page))
2105                        goto out_unmap;
2106                /*
2107                 * Chose the node of the first page. This could
2108                 * be more sophisticated and look at more pages,
2109                 * but isn't for now.
2110                 */
2111                if (node == -1)
2112                        node = page_to_nid(page);
2113                VM_BUG_ON(PageCompound(page));
2114                if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2115                        goto out_unmap;
2116                /* cannot use mapcount: can't collapse if there's a gup pin */
2117                if (page_count(page) != 1)
2118                        goto out_unmap;
2119                if (pte_young(pteval) || PageReferenced(page) ||
2120                    mmu_notifier_test_young(vma->vm_mm, address))
2121                        referenced = 1;
2122        }
2123        if (referenced)
2124                ret = 1;
2125out_unmap:
2126        pte_unmap_unlock(pte, ptl);
2127        if (ret)
2128                /* collapse_huge_page will return with the mmap_sem released */
2129                collapse_huge_page(mm, address, hpage, vma, node);
2130out:
2131        return ret;
2132}
2133
2134static void collect_mm_slot(struct mm_slot *mm_slot)
2135{
2136        struct mm_struct *mm = mm_slot->mm;
2137
2138        VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2139
2140        if (khugepaged_test_exit(mm)) {
2141                /* free mm_slot */
2142                hlist_del(&mm_slot->hash);
2143                list_del(&mm_slot->mm_node);
2144
2145                /*
2146                 * Not strictly needed because the mm exited already.
2147                 *
2148                 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2149                 */
2150
2151                /* khugepaged_mm_lock actually not necessary for the below */
2152                free_mm_slot(mm_slot);
2153                mmdrop(mm);
2154        }
2155}
2156
2157static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2158                                            struct page **hpage)
2159        __releases(&khugepaged_mm_lock)
2160        __acquires(&khugepaged_mm_lock)
2161{
2162        struct mm_slot *mm_slot;
2163        struct mm_struct *mm;
2164        struct vm_area_struct *vma;
2165        int progress = 0;
2166
2167        VM_BUG_ON(!pages);
2168        VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2169
2170        if (khugepaged_scan.mm_slot)
2171                mm_slot = khugepaged_scan.mm_slot;
2172        else {
2173                mm_slot = list_entry(khugepaged_scan.mm_head.next,
2174                                     struct mm_slot, mm_node);
2175                khugepaged_scan.address = 0;
2176                khugepaged_scan.mm_slot = mm_slot;
2177        }
2178        spin_unlock(&khugepaged_mm_lock);
2179
2180        mm = mm_slot->mm;
2181        down_read(&mm->mmap_sem);
2182        if (unlikely(khugepaged_test_exit(mm)))
2183                vma = NULL;
2184        else
2185                vma = find_vma(mm, khugepaged_scan.address);
2186
2187        progress++;
2188        for (; vma; vma = vma->vm_next) {
2189                unsigned long hstart, hend;
2190
2191                cond_resched();
2192                if (unlikely(khugepaged_test_exit(mm))) {
2193                        progress++;
2194                        break;
2195                }
2196
2197                if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2198                     !khugepaged_always()) ||
2199                    (vma->vm_flags & VM_NOHUGEPAGE)) {
2200                skip:
2201                        progress++;
2202                        continue;
2203                }
2204                if (!vma->anon_vma || vma->vm_ops)
2205                        goto skip;
2206                if (is_vma_temporary_stack(vma))
2207                        goto skip;
2208                VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2209
2210                hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2211                hend = vma->vm_end & HPAGE_PMD_MASK;
2212                if (hstart >= hend)
2213                        goto skip;
2214                if (khugepaged_scan.address > hend)
2215                        goto skip;
2216                if (khugepaged_scan.address < hstart)
2217                        khugepaged_scan.address = hstart;
2218                VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2219
2220                while (khugepaged_scan.address < hend) {
2221                        int ret;
2222                        cond_resched();
2223                        if (unlikely(khugepaged_test_exit(mm)))
2224                                goto breakouterloop;
2225
2226                        VM_BUG_ON(khugepaged_scan.address < hstart ||
2227                                  khugepaged_scan.address + HPAGE_PMD_SIZE >
2228                                  hend);
2229                        ret = khugepaged_scan_pmd(mm, vma,
2230                                                  khugepaged_scan.address,
2231                                                  hpage);
2232                        /* move to next address */
2233                        khugepaged_scan.address += HPAGE_PMD_SIZE;
2234                        progress += HPAGE_PMD_NR;
2235                        if (ret)
2236                                /* we released mmap_sem so break loop */
2237                                goto breakouterloop_mmap_sem;
2238                        if (progress >= pages)
2239                                goto breakouterloop;
2240                }
2241        }
2242breakouterloop:
2243        up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2244breakouterloop_mmap_sem:
2245
2246        spin_lock(&khugepaged_mm_lock);
2247        VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2248        /*
2249         * Release the current mm_slot if this mm is about to die, or
2250         * if we scanned all vmas of this mm.
2251         */
2252        if (khugepaged_test_exit(mm) || !vma) {
2253                /*
2254                 * Make sure that if mm_users is reaching zero while
2255                 * khugepaged runs here, khugepaged_exit will find
2256                 * mm_slot not pointing to the exiting mm.
2257                 */
2258                if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2259                        khugepaged_scan.mm_slot = list_entry(
2260                                mm_slot->mm_node.next,
2261                                struct mm_slot, mm_node);
2262                        khugepaged_scan.address = 0;
2263                } else {
2264                        khugepaged_scan.mm_slot = NULL;
2265                        khugepaged_full_scans++;
2266                }
2267
2268                collect_mm_slot(mm_slot);
2269        }
2270
2271        return progress;
2272}
2273
2274static int khugepaged_has_work(void)
2275{
2276        return !list_empty(&khugepaged_scan.mm_head) &&
2277                khugepaged_enabled();
2278}
2279
2280static int khugepaged_wait_event(void)
2281{
2282        return !list_empty(&khugepaged_scan.mm_head) ||
2283                kthread_should_stop();
2284}
2285
2286static void khugepaged_do_scan(void)
2287{
2288        struct page *hpage = NULL;
2289        unsigned int progress = 0, pass_through_head = 0;
2290        unsigned int pages = khugepaged_pages_to_scan;
2291        bool wait = true;
2292
2293        barrier(); /* write khugepaged_pages_to_scan to local stack */
2294
2295        while (progress < pages) {
2296                if (!khugepaged_prealloc_page(&hpage, &wait))
2297                        break;
2298
2299                cond_resched();
2300
2301                if (unlikely(kthread_should_stop() || freezing(current)))
2302                        break;
2303
2304                spin_lock(&khugepaged_mm_lock);
2305                if (!khugepaged_scan.mm_slot)
2306                        pass_through_head++;
2307                if (khugepaged_has_work() &&
2308                    pass_through_head < 2)
2309                        progress += khugepaged_scan_mm_slot(pages - progress,
2310                                                            &hpage);
2311                else
2312                        progress = pages;
2313                spin_unlock(&khugepaged_mm_lock);
2314        }
2315
2316        if (!IS_ERR_OR_NULL(hpage))
2317                put_page(hpage);
2318}
2319
2320static void khugepaged_wait_work(void)
2321{
2322        try_to_freeze();
2323
2324        if (khugepaged_has_work()) {
2325                if (!khugepaged_scan_sleep_millisecs)
2326                        return;
2327
2328                wait_event_freezable_timeout(khugepaged_wait,
2329                                             kthread_should_stop(),
2330                        msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2331                return;
2332        }
2333
2334        if (khugepaged_enabled())
2335                wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2336}
2337
2338static int khugepaged(void *none)
2339{
2340        struct mm_slot *mm_slot;
2341
2342        set_freezable();
2343        set_user_nice(current, 19);
2344
2345        while (!kthread_should_stop()) {
2346                khugepaged_do_scan();
2347                khugepaged_wait_work();
2348        }
2349
2350        spin_lock(&khugepaged_mm_lock);
2351        mm_slot = khugepaged_scan.mm_slot;
2352        khugepaged_scan.mm_slot = NULL;
2353        if (mm_slot)
2354                collect_mm_slot(mm_slot);
2355        spin_unlock(&khugepaged_mm_lock);
2356        return 0;
2357}
2358
2359void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2360{
2361        struct page *page;
2362
2363        spin_lock(&mm->page_table_lock);
2364        if (unlikely(!pmd_trans_huge(*pmd))) {
2365                spin_unlock(&mm->page_table_lock);
2366                return;
2367        }
2368        page = pmd_page(*pmd);
2369        VM_BUG_ON(!page_count(page));
2370        get_page(page);
2371        spin_unlock(&mm->page_table_lock);
2372
2373        split_huge_page(page);
2374
2375        put_page(page);
2376        BUG_ON(pmd_trans_huge(*pmd));
2377}
2378
2379static void split_huge_page_address(struct mm_struct *mm,
2380                                    unsigned long address)
2381{
2382        pgd_t *pgd;
2383        pud_t *pud;
2384        pmd_t *pmd;
2385
2386        VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2387
2388        pgd = pgd_offset(mm, address);
2389        if (!pgd_present(*pgd))
2390                return;
2391
2392        pud = pud_offset(pgd, address);
2393        if (!pud_present(*pud))
2394                return;
2395
2396        pmd = pmd_offset(pud, address);
2397        if (!pmd_present(*pmd))
2398                return;
2399        /*
2400         * Caller holds the mmap_sem write mode, so a huge pmd cannot
2401         * materialize from under us.
2402         */
2403        split_huge_page_pmd(mm, pmd);
2404}
2405
2406void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2407                             unsigned long start,
2408                             unsigned long end,
2409                             long adjust_next)
2410{
2411        /*
2412         * If the new start address isn't hpage aligned and it could
2413         * previously contain an hugepage: check if we need to split
2414         * an huge pmd.
2415         */
2416        if (start & ~HPAGE_PMD_MASK &&
2417            (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2418            (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2419                split_huge_page_address(vma->vm_mm, start);
2420
2421        /*
2422         * If the new end address isn't hpage aligned and it could
2423         * previously contain an hugepage: check if we need to split
2424         * an huge pmd.
2425         */
2426        if (end & ~HPAGE_PMD_MASK &&
2427            (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2428            (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2429                split_huge_page_address(vma->vm_mm, end);
2430
2431        /*
2432         * If we're also updating the vma->vm_next->vm_start, if the new
2433         * vm_next->vm_start isn't page aligned and it could previously
2434         * contain an hugepage: check if we need to split an huge pmd.
2435         */
2436        if (adjust_next > 0) {
2437                struct vm_area_struct *next = vma->vm_next;
2438                unsigned long nstart = next->vm_start;
2439                nstart += adjust_next << PAGE_SHIFT;
2440                if (nstart & ~HPAGE_PMD_MASK &&
2441                    (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2442                    (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2443                        split_huge_page_address(next->vm_mm, nstart);
2444        }
2445}
2446
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