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/shrinker.h>
  16#include <linux/mm_inline.h>
  17#include <linux/kthread.h>
  18#include <linux/khugepaged.h>
  19#include <linux/freezer.h>
  20#include <linux/mman.h>
  21#include <linux/pagemap.h>
  22#include <linux/migrate.h>
  23#include <linux/hashtable.h>
  24
  25#include <asm/tlb.h>
  26#include <asm/pgalloc.h>
  27#include "internal.h"
  28
  29/*
  30 * By default transparent hugepage support is enabled for all mappings
  31 * and khugepaged scans all mappings. Defrag is only invoked by
  32 * khugepaged hugepage allocations and by page faults inside
  33 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
  34 * allocations.
  35 */
  36unsigned long transparent_hugepage_flags __read_mostly =
  37#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  38        (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  39#endif
  40#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  41        (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  42#endif
  43        (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
  44        (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  45        (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  46
  47/* default scan 8*512 pte (or vmas) every 30 second */
  48static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
  49static unsigned int khugepaged_pages_collapsed;
  50static unsigned int khugepaged_full_scans;
  51static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  52/* during fragmentation poll the hugepage allocator once every minute */
  53static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  54static struct task_struct *khugepaged_thread __read_mostly;
  55static DEFINE_MUTEX(khugepaged_mutex);
  56static DEFINE_SPINLOCK(khugepaged_mm_lock);
  57static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  58/*
  59 * default collapse hugepages if there is at least one pte mapped like
  60 * it would have happened if the vma was large enough during page
  61 * fault.
  62 */
  63static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
  64
  65static int khugepaged(void *none);
  66static int khugepaged_slab_init(void);
  67
  68#define MM_SLOTS_HASH_BITS 10
  69static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
  70
  71static struct kmem_cache *mm_slot_cache __read_mostly;
  72
  73/**
  74 * struct mm_slot - hash lookup from mm to mm_slot
  75 * @hash: hash collision list
  76 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
  77 * @mm: the mm that this information is valid for
  78 */
  79struct mm_slot {
  80        struct hlist_node hash;
  81        struct list_head mm_node;
  82        struct mm_struct *mm;
  83};
  84
  85/**
  86 * struct khugepaged_scan - cursor for scanning
  87 * @mm_head: the head of the mm list to scan
  88 * @mm_slot: the current mm_slot we are scanning
  89 * @address: the next address inside that to be scanned
  90 *
  91 * There is only the one khugepaged_scan instance of this cursor structure.
  92 */
  93struct khugepaged_scan {
  94        struct list_head mm_head;
  95        struct mm_slot *mm_slot;
  96        unsigned long address;
  97};
  98static struct khugepaged_scan khugepaged_scan = {
  99        .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
 100};
 101
 102
 103static int set_recommended_min_free_kbytes(void)
 104{
 105        struct zone *zone;
 106        int nr_zones = 0;
 107        unsigned long recommended_min;
 108
 109        if (!khugepaged_enabled())
 110                return 0;
 111
 112        for_each_populated_zone(zone)
 113                nr_zones++;
 114
 115        /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
 116        recommended_min = pageblock_nr_pages * nr_zones * 2;
 117
 118        /*
 119         * Make sure that on average at least two pageblocks are almost free
 120         * of another type, one for a migratetype to fall back to and a
 121         * second to avoid subsequent fallbacks of other types There are 3
 122         * MIGRATE_TYPES we care about.
 123         */
 124        recommended_min += pageblock_nr_pages * nr_zones *
 125                           MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
 126
 127        /* don't ever allow to reserve more than 5% of the lowmem */
 128        recommended_min = min(recommended_min,
 129                              (unsigned long) nr_free_buffer_pages() / 20);
 130        recommended_min <<= (PAGE_SHIFT-10);
 131
 132        if (recommended_min > min_free_kbytes)
 133                min_free_kbytes = recommended_min;
 134        setup_per_zone_wmarks();
 135        return 0;
 136}
 137late_initcall(set_recommended_min_free_kbytes);
 138
 139static int start_khugepaged(void)
 140{
 141        int err = 0;
 142        if (khugepaged_enabled()) {
 143                if (!khugepaged_thread)
 144                        khugepaged_thread = kthread_run(khugepaged, NULL,
 145                                                        "khugepaged");
 146                if (unlikely(IS_ERR(khugepaged_thread))) {
 147                        printk(KERN_ERR
 148                               "khugepaged: kthread_run(khugepaged) failed\n");
 149                        err = PTR_ERR(khugepaged_thread);
 150                        khugepaged_thread = NULL;
 151                }
 152
 153                if (!list_empty(&khugepaged_scan.mm_head))
 154                        wake_up_interruptible(&khugepaged_wait);
 155
 156                set_recommended_min_free_kbytes();
 157        } else if (khugepaged_thread) {
 158                kthread_stop(khugepaged_thread);
 159                khugepaged_thread = NULL;
 160        }
 161
 162        return err;
 163}
 164
 165static atomic_t huge_zero_refcount;
 166static struct page *huge_zero_page __read_mostly;
 167
 168static inline bool is_huge_zero_page(struct page *page)
 169{
 170        return ACCESS_ONCE(huge_zero_page) == page;
 171}
 172
 173static inline bool is_huge_zero_pmd(pmd_t pmd)
 174{
 175        return is_huge_zero_page(pmd_page(pmd));
 176}
 177
 178static struct page *get_huge_zero_page(void)
 179{
 180        struct page *zero_page;
 181retry:
 182        if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 183                return ACCESS_ONCE(huge_zero_page);
 184
 185        zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 186                        HPAGE_PMD_ORDER);
 187        if (!zero_page) {
 188                count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 189                return NULL;
 190        }
 191        count_vm_event(THP_ZERO_PAGE_ALLOC);
 192        preempt_disable();
 193        if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 194                preempt_enable();
 195                __free_page(zero_page);
 196                goto retry;
 197        }
 198
 199        /* We take additional reference here. It will be put back by shrinker */
 200        atomic_set(&huge_zero_refcount, 2);
 201        preempt_enable();
 202        return ACCESS_ONCE(huge_zero_page);
 203}
 204
 205static void put_huge_zero_page(void)
 206{
 207        /*
 208         * Counter should never go to zero here. Only shrinker can put
 209         * last reference.
 210         */
 211        BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 212}
 213
 214static int shrink_huge_zero_page(struct shrinker *shrink,
 215                struct shrink_control *sc)
 216{
 217        if (!sc->nr_to_scan)
 218                /* we can free zero page only if last reference remains */
 219                return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 220
 221        if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 222                struct page *zero_page = xchg(&huge_zero_page, NULL);
 223                BUG_ON(zero_page == NULL);
 224                __free_page(zero_page);
 225        }
 226
 227        return 0;
 228}
 229
 230static struct shrinker huge_zero_page_shrinker = {
 231        .shrink = shrink_huge_zero_page,
 232        .seeks = DEFAULT_SEEKS,
 233};
 234
 235#ifdef CONFIG_SYSFS
 236
 237static ssize_t double_flag_show(struct kobject *kobj,
 238                                struct kobj_attribute *attr, char *buf,
 239                                enum transparent_hugepage_flag enabled,
 240                                enum transparent_hugepage_flag req_madv)
 241{
 242        if (test_bit(enabled, &transparent_hugepage_flags)) {
 243                VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
 244                return sprintf(buf, "[always] madvise never\n");
 245        } else if (test_bit(req_madv, &transparent_hugepage_flags))
 246                return sprintf(buf, "always [madvise] never\n");
 247        else
 248                return sprintf(buf, "always madvise [never]\n");
 249}
 250static ssize_t double_flag_store(struct kobject *kobj,
 251                                 struct kobj_attribute *attr,
 252                                 const char *buf, size_t count,
 253                                 enum transparent_hugepage_flag enabled,
 254                                 enum transparent_hugepage_flag req_madv)
 255{
 256        if (!memcmp("always", buf,
 257                    min(sizeof("always")-1, count))) {
 258                set_bit(enabled, &transparent_hugepage_flags);
 259                clear_bit(req_madv, &transparent_hugepage_flags);
 260        } else if (!memcmp("madvise", buf,
 261                           min(sizeof("madvise")-1, count))) {
 262                clear_bit(enabled, &transparent_hugepage_flags);
 263                set_bit(req_madv, &transparent_hugepage_flags);
 264        } else if (!memcmp("never", buf,
 265                           min(sizeof("never")-1, count))) {
 266                clear_bit(enabled, &transparent_hugepage_flags);
 267                clear_bit(req_madv, &transparent_hugepage_flags);
 268        } else
 269                return -EINVAL;
 270
 271        return count;
 272}
 273
 274static ssize_t enabled_show(struct kobject *kobj,
 275                            struct kobj_attribute *attr, char *buf)
 276{
 277        return double_flag_show(kobj, attr, buf,
 278                                TRANSPARENT_HUGEPAGE_FLAG,
 279                                TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 280}
 281static ssize_t enabled_store(struct kobject *kobj,
 282                             struct kobj_attribute *attr,
 283                             const char *buf, size_t count)
 284{
 285        ssize_t ret;
 286
 287        ret = double_flag_store(kobj, attr, buf, count,
 288                                TRANSPARENT_HUGEPAGE_FLAG,
 289                                TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 290
 291        if (ret > 0) {
 292                int err;
 293
 294                mutex_lock(&khugepaged_mutex);
 295                err = start_khugepaged();
 296                mutex_unlock(&khugepaged_mutex);
 297
 298                if (err)
 299                        ret = err;
 300        }
 301
 302        return ret;
 303}
 304static struct kobj_attribute enabled_attr =
 305        __ATTR(enabled, 0644, enabled_show, enabled_store);
 306
 307static ssize_t single_flag_show(struct kobject *kobj,
 308                                struct kobj_attribute *attr, char *buf,
 309                                enum transparent_hugepage_flag flag)
 310{
 311        return sprintf(buf, "%d\n",
 312                       !!test_bit(flag, &transparent_hugepage_flags));
 313}
 314
 315static ssize_t single_flag_store(struct kobject *kobj,
 316                                 struct kobj_attribute *attr,
 317                                 const char *buf, size_t count,
 318                                 enum transparent_hugepage_flag flag)
 319{
 320        unsigned long value;
 321        int ret;
 322
 323        ret = kstrtoul(buf, 10, &value);
 324        if (ret < 0)
 325                return ret;
 326        if (value > 1)
 327                return -EINVAL;
 328
 329        if (value)
 330                set_bit(flag, &transparent_hugepage_flags);
 331        else
 332                clear_bit(flag, &transparent_hugepage_flags);
 333
 334        return count;
 335}
 336
 337/*
 338 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 339 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 340 * memory just to allocate one more hugepage.
 341 */
 342static ssize_t defrag_show(struct kobject *kobj,
 343                           struct kobj_attribute *attr, char *buf)
 344{
 345        return double_flag_show(kobj, attr, buf,
 346                                TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 347                                TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 348}
 349static ssize_t defrag_store(struct kobject *kobj,
 350                            struct kobj_attribute *attr,
 351                            const char *buf, size_t count)
 352{
 353        return double_flag_store(kobj, attr, buf, count,
 354                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 355                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 356}
 357static struct kobj_attribute defrag_attr =
 358        __ATTR(defrag, 0644, defrag_show, defrag_store);
 359
 360static ssize_t use_zero_page_show(struct kobject *kobj,
 361                struct kobj_attribute *attr, char *buf)
 362{
 363        return single_flag_show(kobj, attr, buf,
 364                                TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 365}
 366static ssize_t use_zero_page_store(struct kobject *kobj,
 367                struct kobj_attribute *attr, const char *buf, size_t count)
 368{
 369        return single_flag_store(kobj, attr, buf, count,
 370                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 371}
 372static struct kobj_attribute use_zero_page_attr =
 373        __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 374#ifdef CONFIG_DEBUG_VM
 375static ssize_t debug_cow_show(struct kobject *kobj,
 376                                struct kobj_attribute *attr, char *buf)
 377{
 378        return single_flag_show(kobj, attr, buf,
 379                                TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 380}
 381static ssize_t debug_cow_store(struct kobject *kobj,
 382                               struct kobj_attribute *attr,
 383                               const char *buf, size_t count)
 384{
 385        return single_flag_store(kobj, attr, buf, count,
 386                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 387}
 388static struct kobj_attribute debug_cow_attr =
 389        __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 390#endif /* CONFIG_DEBUG_VM */
 391
 392static struct attribute *hugepage_attr[] = {
 393        &enabled_attr.attr,
 394        &defrag_attr.attr,
 395        &use_zero_page_attr.attr,
 396#ifdef CONFIG_DEBUG_VM
 397        &debug_cow_attr.attr,
 398#endif
 399        NULL,
 400};
 401
 402static struct attribute_group hugepage_attr_group = {
 403        .attrs = hugepage_attr,
 404};
 405
 406static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 407                                         struct kobj_attribute *attr,
 408                                         char *buf)
 409{
 410        return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 411}
 412
 413static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 414                                          struct kobj_attribute *attr,
 415                                          const char *buf, size_t count)
 416{
 417        unsigned long msecs;
 418        int err;
 419
 420        err = strict_strtoul(buf, 10, &msecs);
 421        if (err || msecs > UINT_MAX)
 422                return -EINVAL;
 423
 424        khugepaged_scan_sleep_millisecs = msecs;
 425        wake_up_interruptible(&khugepaged_wait);
 426
 427        return count;
 428}
 429static struct kobj_attribute scan_sleep_millisecs_attr =
 430        __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 431               scan_sleep_millisecs_store);
 432
 433static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 434                                          struct kobj_attribute *attr,
 435                                          char *buf)
 436{
 437        return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 438}
 439
 440static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 441                                           struct kobj_attribute *attr,
 442                                           const char *buf, size_t count)
 443{
 444        unsigned long msecs;
 445        int err;
 446
 447        err = strict_strtoul(buf, 10, &msecs);
 448        if (err || msecs > UINT_MAX)
 449                return -EINVAL;
 450
 451        khugepaged_alloc_sleep_millisecs = msecs;
 452        wake_up_interruptible(&khugepaged_wait);
 453
 454        return count;
 455}
 456static struct kobj_attribute alloc_sleep_millisecs_attr =
 457        __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 458               alloc_sleep_millisecs_store);
 459
 460static ssize_t pages_to_scan_show(struct kobject *kobj,
 461                                  struct kobj_attribute *attr,
 462                                  char *buf)
 463{
 464        return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 465}
 466static ssize_t pages_to_scan_store(struct kobject *kobj,
 467                                   struct kobj_attribute *attr,
 468                                   const char *buf, size_t count)
 469{
 470        int err;
 471        unsigned long pages;
 472
 473        err = strict_strtoul(buf, 10, &pages);
 474        if (err || !pages || pages > UINT_MAX)
 475                return -EINVAL;
 476
 477        khugepaged_pages_to_scan = pages;
 478
 479        return count;
 480}
 481static struct kobj_attribute pages_to_scan_attr =
 482        __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 483               pages_to_scan_store);
 484
 485static ssize_t pages_collapsed_show(struct kobject *kobj,
 486                                    struct kobj_attribute *attr,
 487                                    char *buf)
 488{
 489        return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 490}
 491static struct kobj_attribute pages_collapsed_attr =
 492        __ATTR_RO(pages_collapsed);
 493
 494static ssize_t full_scans_show(struct kobject *kobj,
 495                               struct kobj_attribute *attr,
 496                               char *buf)
 497{
 498        return sprintf(buf, "%u\n", khugepaged_full_scans);
 499}
 500static struct kobj_attribute full_scans_attr =
 501        __ATTR_RO(full_scans);
 502
 503static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 504                                      struct kobj_attribute *attr, char *buf)
 505{
 506        return single_flag_show(kobj, attr, buf,
 507                                TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 508}
 509static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 510                                       struct kobj_attribute *attr,
 511                                       const char *buf, size_t count)
 512{
 513        return single_flag_store(kobj, attr, buf, count,
 514                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 515}
 516static struct kobj_attribute khugepaged_defrag_attr =
 517        __ATTR(defrag, 0644, khugepaged_defrag_show,
 518               khugepaged_defrag_store);
 519
 520/*
 521 * max_ptes_none controls if khugepaged should collapse hugepages over
 522 * any unmapped ptes in turn potentially increasing the memory
 523 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 524 * reduce the available free memory in the system as it
 525 * runs. Increasing max_ptes_none will instead potentially reduce the
 526 * free memory in the system during the khugepaged scan.
 527 */
 528static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 529                                             struct kobj_attribute *attr,
 530                                             char *buf)
 531{
 532        return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 533}
 534static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 535                                              struct kobj_attribute *attr,
 536                                              const char *buf, size_t count)
 537{
 538        int err;
 539        unsigned long max_ptes_none;
 540
 541        err = strict_strtoul(buf, 10, &max_ptes_none);
 542        if (err || max_ptes_none > HPAGE_PMD_NR-1)
 543                return -EINVAL;
 544
 545        khugepaged_max_ptes_none = max_ptes_none;
 546
 547        return count;
 548}
 549static struct kobj_attribute khugepaged_max_ptes_none_attr =
 550        __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 551               khugepaged_max_ptes_none_store);
 552
 553static struct attribute *khugepaged_attr[] = {
 554        &khugepaged_defrag_attr.attr,
 555        &khugepaged_max_ptes_none_attr.attr,
 556        &pages_to_scan_attr.attr,
 557        &pages_collapsed_attr.attr,
 558        &full_scans_attr.attr,
 559        &scan_sleep_millisecs_attr.attr,
 560        &alloc_sleep_millisecs_attr.attr,
 561        NULL,
 562};
 563
 564static struct attribute_group khugepaged_attr_group = {
 565        .attrs = khugepaged_attr,
 566        .name = "khugepaged",
 567};
 568
 569static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 570{
 571        int err;
 572
 573        *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 574        if (unlikely(!*hugepage_kobj)) {
 575                printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n");
 576                return -ENOMEM;
 577        }
 578
 579        err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 580        if (err) {
 581                printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
 582                goto delete_obj;
 583        }
 584
 585        err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 586        if (err) {
 587                printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
 588                goto remove_hp_group;
 589        }
 590
 591        return 0;
 592
 593remove_hp_group:
 594        sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 595delete_obj:
 596        kobject_put(*hugepage_kobj);
 597        return err;
 598}
 599
 600static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 601{
 602        sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 603        sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 604        kobject_put(hugepage_kobj);
 605}
 606#else
 607static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 608{
 609        return 0;
 610}
 611
 612static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 613{
 614}
 615#endif /* CONFIG_SYSFS */
 616
 617static int __init hugepage_init(void)
 618{
 619        int err;
 620        struct kobject *hugepage_kobj;
 621
 622        if (!has_transparent_hugepage()) {
 623                transparent_hugepage_flags = 0;
 624                return -EINVAL;
 625        }
 626
 627        err = hugepage_init_sysfs(&hugepage_kobj);
 628        if (err)
 629                return err;
 630
 631        err = khugepaged_slab_init();
 632        if (err)
 633                goto out;
 634
 635        register_shrinker(&huge_zero_page_shrinker);
 636
 637        /*
 638         * By default disable transparent hugepages on smaller systems,
 639         * where the extra memory used could hurt more than TLB overhead
 640         * is likely to save.  The admin can still enable it through /sys.
 641         */
 642        if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
 643                transparent_hugepage_flags = 0;
 644
 645        start_khugepaged();
 646
 647        return 0;
 648out:
 649        hugepage_exit_sysfs(hugepage_kobj);
 650        return err;
 651}
 652module_init(hugepage_init)
 653
 654static int __init setup_transparent_hugepage(char *str)
 655{
 656        int ret = 0;
 657        if (!str)
 658                goto out;
 659        if (!strcmp(str, "always")) {
 660                set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 661                        &transparent_hugepage_flags);
 662                clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 663                          &transparent_hugepage_flags);
 664                ret = 1;
 665        } else if (!strcmp(str, "madvise")) {
 666                clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 667                          &transparent_hugepage_flags);
 668                set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 669                        &transparent_hugepage_flags);
 670                ret = 1;
 671        } else if (!strcmp(str, "never")) {
 672                clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 673                          &transparent_hugepage_flags);
 674                clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 675                          &transparent_hugepage_flags);
 676                ret = 1;
 677        }
 678out:
 679        if (!ret)
 680                printk(KERN_WARNING
 681                       "transparent_hugepage= cannot parse, ignored\n");
 682        return ret;
 683}
 684__setup("transparent_hugepage=", setup_transparent_hugepage);
 685
 686pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 687{
 688        if (likely(vma->vm_flags & VM_WRITE))
 689                pmd = pmd_mkwrite(pmd);
 690        return pmd;
 691}
 692
 693static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma)
 694{
 695        pmd_t entry;
 696        entry = mk_pmd(page, vma->vm_page_prot);
 697        entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 698        entry = pmd_mkhuge(entry);
 699        return entry;
 700}
 701
 702static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 703                                        struct vm_area_struct *vma,
 704                                        unsigned long haddr, pmd_t *pmd,
 705                                        struct page *page)
 706{
 707        pgtable_t pgtable;
 708
 709        VM_BUG_ON(!PageCompound(page));
 710        pgtable = pte_alloc_one(mm, haddr);
 711        if (unlikely(!pgtable))
 712                return VM_FAULT_OOM;
 713
 714        clear_huge_page(page, haddr, HPAGE_PMD_NR);
 715        /*
 716         * The memory barrier inside __SetPageUptodate makes sure that
 717         * clear_huge_page writes become visible before the set_pmd_at()
 718         * write.
 719         */
 720        __SetPageUptodate(page);
 721
 722        spin_lock(&mm->page_table_lock);
 723        if (unlikely(!pmd_none(*pmd))) {
 724                spin_unlock(&mm->page_table_lock);
 725                mem_cgroup_uncharge_page(page);
 726                put_page(page);
 727                pte_free(mm, pgtable);
 728        } else {
 729                pmd_t entry;
 730                entry = mk_huge_pmd(page, vma);
 731                page_add_new_anon_rmap(page, vma, haddr);
 732                set_pmd_at(mm, haddr, pmd, entry);
 733                pgtable_trans_huge_deposit(mm, pgtable);
 734                add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 735                mm->nr_ptes++;
 736                spin_unlock(&mm->page_table_lock);
 737        }
 738
 739        return 0;
 740}
 741
 742static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 743{
 744        return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
 745}
 746
 747static inline struct page *alloc_hugepage_vma(int defrag,
 748                                              struct vm_area_struct *vma,
 749                                              unsigned long haddr, int nd,
 750                                              gfp_t extra_gfp)
 751{
 752        return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
 753                               HPAGE_PMD_ORDER, vma, haddr, nd);
 754}
 755
 756#ifndef CONFIG_NUMA
 757static inline struct page *alloc_hugepage(int defrag)
 758{
 759        return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
 760                           HPAGE_PMD_ORDER);
 761}
 762#endif
 763
 764static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 765                struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 766                struct page *zero_page)
 767{
 768        pmd_t entry;
 769        if (!pmd_none(*pmd))
 770                return false;
 771        entry = mk_pmd(zero_page, vma->vm_page_prot);
 772        entry = pmd_wrprotect(entry);
 773        entry = pmd_mkhuge(entry);
 774        set_pmd_at(mm, haddr, pmd, entry);
 775        pgtable_trans_huge_deposit(mm, pgtable);
 776        mm->nr_ptes++;
 777        return true;
 778}
 779
 780int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 781                               unsigned long address, pmd_t *pmd,
 782                               unsigned int flags)
 783{
 784        struct page *page;
 785        unsigned long haddr = address & HPAGE_PMD_MASK;
 786        pte_t *pte;
 787
 788        if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
 789                if (unlikely(anon_vma_prepare(vma)))
 790                        return VM_FAULT_OOM;
 791                if (unlikely(khugepaged_enter(vma)))
 792                        return VM_FAULT_OOM;
 793                if (!(flags & FAULT_FLAG_WRITE) &&
 794                                transparent_hugepage_use_zero_page()) {
 795                        pgtable_t pgtable;
 796                        struct page *zero_page;
 797                        bool set;
 798                        pgtable = pte_alloc_one(mm, haddr);
 799                        if (unlikely(!pgtable))
 800                                return VM_FAULT_OOM;
 801                        zero_page = get_huge_zero_page();
 802                        if (unlikely(!zero_page)) {
 803                                pte_free(mm, pgtable);
 804                                count_vm_event(THP_FAULT_FALLBACK);
 805                                goto out;
 806                        }
 807                        spin_lock(&mm->page_table_lock);
 808                        set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
 809                                        zero_page);
 810                        spin_unlock(&mm->page_table_lock);
 811                        if (!set) {
 812                                pte_free(mm, pgtable);
 813                                put_huge_zero_page();
 814                        }
 815                        return 0;
 816                }
 817                page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
 818                                          vma, haddr, numa_node_id(), 0);
 819                if (unlikely(!page)) {
 820                        count_vm_event(THP_FAULT_FALLBACK);
 821                        goto out;
 822                }
 823                count_vm_event(THP_FAULT_ALLOC);
 824                if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
 825                        put_page(page);
 826                        goto out;
 827                }
 828                if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
 829                                                          page))) {
 830                        mem_cgroup_uncharge_page(page);
 831                        put_page(page);
 832                        goto out;
 833                }
 834
 835                return 0;
 836        }
 837out:
 838        /*
 839         * Use __pte_alloc instead of pte_alloc_map, because we can't
 840         * run pte_offset_map on the pmd, if an huge pmd could
 841         * materialize from under us from a different thread.
 842         */
 843        if (unlikely(pmd_none(*pmd)) &&
 844            unlikely(__pte_alloc(mm, vma, pmd, address)))
 845                return VM_FAULT_OOM;
 846        /* if an huge pmd materialized from under us just retry later */
 847        if (unlikely(pmd_trans_huge(*pmd)))
 848                return 0;
 849        /*
 850         * A regular pmd is established and it can't morph into a huge pmd
 851         * from under us anymore at this point because we hold the mmap_sem
 852         * read mode and khugepaged takes it in write mode. So now it's
 853         * safe to run pte_offset_map().
 854         */
 855        pte = pte_offset_map(pmd, address);
 856        return handle_pte_fault(mm, vma, address, pte, pmd, flags);
 857}
 858
 859int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 860                  pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 861                  struct vm_area_struct *vma)
 862{
 863        struct page *src_page;
 864        pmd_t pmd;
 865        pgtable_t pgtable;
 866        int ret;
 867
 868        ret = -ENOMEM;
 869        pgtable = pte_alloc_one(dst_mm, addr);
 870        if (unlikely(!pgtable))
 871                goto out;
 872
 873        spin_lock(&dst_mm->page_table_lock);
 874        spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
 875
 876        ret = -EAGAIN;
 877        pmd = *src_pmd;
 878        if (unlikely(!pmd_trans_huge(pmd))) {
 879                pte_free(dst_mm, pgtable);
 880                goto out_unlock;
 881        }
 882        /*
 883         * mm->page_table_lock is enough to be sure that huge zero pmd is not
 884         * under splitting since we don't split the page itself, only pmd to
 885         * a page table.
 886         */
 887        if (is_huge_zero_pmd(pmd)) {
 888                struct page *zero_page;
 889                bool set;
 890                /*
 891                 * get_huge_zero_page() will never allocate a new page here,
 892                 * since we already have a zero page to copy. It just takes a
 893                 * reference.
 894                 */
 895                zero_page = get_huge_zero_page();
 896                set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 897                                zero_page);
 898                BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
 899                ret = 0;
 900                goto out_unlock;
 901        }
 902        if (unlikely(pmd_trans_splitting(pmd))) {
 903                /* split huge page running from under us */
 904                spin_unlock(&src_mm->page_table_lock);
 905                spin_unlock(&dst_mm->page_table_lock);
 906                pte_free(dst_mm, pgtable);
 907
 908                wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
 909                goto out;
 910        }
 911        src_page = pmd_page(pmd);
 912        VM_BUG_ON(!PageHead(src_page));
 913        get_page(src_page);
 914        page_dup_rmap(src_page);
 915        add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 916
 917        pmdp_set_wrprotect(src_mm, addr, src_pmd);
 918        pmd = pmd_mkold(pmd_wrprotect(pmd));
 919        set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 920        pgtable_trans_huge_deposit(dst_mm, pgtable);
 921        dst_mm->nr_ptes++;
 922
 923        ret = 0;
 924out_unlock:
 925        spin_unlock(&src_mm->page_table_lock);
 926        spin_unlock(&dst_mm->page_table_lock);
 927out:
 928        return ret;
 929}
 930
 931void huge_pmd_set_accessed(struct mm_struct *mm,
 932                           struct vm_area_struct *vma,
 933                           unsigned long address,
 934                           pmd_t *pmd, pmd_t orig_pmd,
 935                           int dirty)
 936{
 937        pmd_t entry;
 938        unsigned long haddr;
 939
 940        spin_lock(&mm->page_table_lock);
 941        if (unlikely(!pmd_same(*pmd, orig_pmd)))
 942                goto unlock;
 943
 944        entry = pmd_mkyoung(orig_pmd);
 945        haddr = address & HPAGE_PMD_MASK;
 946        if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
 947                update_mmu_cache_pmd(vma, address, pmd);
 948
 949unlock:
 950        spin_unlock(&mm->page_table_lock);
 951}
 952
 953static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
 954                struct vm_area_struct *vma, unsigned long address,
 955                pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
 956{
 957        pgtable_t pgtable;
 958        pmd_t _pmd;
 959        struct page *page;
 960        int i, ret = 0;
 961        unsigned long mmun_start;       /* For mmu_notifiers */
 962        unsigned long mmun_end;         /* For mmu_notifiers */
 963
 964        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
 965        if (!page) {
 966                ret |= VM_FAULT_OOM;
 967                goto out;
 968        }
 969
 970        if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
 971                put_page(page);
 972                ret |= VM_FAULT_OOM;
 973                goto out;
 974        }
 975
 976        clear_user_highpage(page, address);
 977        __SetPageUptodate(page);
 978
 979        mmun_start = haddr;
 980        mmun_end   = haddr + HPAGE_PMD_SIZE;
 981        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 982
 983        spin_lock(&mm->page_table_lock);
 984        if (unlikely(!pmd_same(*pmd, orig_pmd)))
 985                goto out_free_page;
 986
 987        pmdp_clear_flush(vma, haddr, pmd);
 988        /* leave pmd empty until pte is filled */
 989
 990        pgtable = pgtable_trans_huge_withdraw(mm);
 991        pmd_populate(mm, &_pmd, pgtable);
 992
 993        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
 994                pte_t *pte, entry;
 995                if (haddr == (address & PAGE_MASK)) {
 996                        entry = mk_pte(page, vma->vm_page_prot);
 997                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 998                        page_add_new_anon_rmap(page, vma, haddr);
 999                } else {
1000                        entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1001                        entry = pte_mkspecial(entry);
1002                }
1003                pte = pte_offset_map(&_pmd, haddr);
1004                VM_BUG_ON(!pte_none(*pte));
1005                set_pte_at(mm, haddr, pte, entry);
1006                pte_unmap(pte);
1007        }
1008        smp_wmb(); /* make pte visible before pmd */
1009        pmd_populate(mm, pmd, pgtable);
1010        spin_unlock(&mm->page_table_lock);
1011        put_huge_zero_page();
1012        inc_mm_counter(mm, MM_ANONPAGES);
1013
1014        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1015
1016        ret |= VM_FAULT_WRITE;
1017out:
1018        return ret;
1019out_free_page:
1020        spin_unlock(&mm->page_table_lock);
1021        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1022        mem_cgroup_uncharge_page(page);
1023        put_page(page);
1024        goto out;
1025}
1026
1027static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1028                                        struct vm_area_struct *vma,
1029                                        unsigned long address,
1030                                        pmd_t *pmd, pmd_t orig_pmd,
1031                                        struct page *page,
1032                                        unsigned long haddr)
1033{
1034        pgtable_t pgtable;
1035        pmd_t _pmd;
1036        int ret = 0, i;
1037        struct page **pages;
1038        unsigned long mmun_start;       /* For mmu_notifiers */
1039        unsigned long mmun_end;         /* For mmu_notifiers */
1040
1041        pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1042                        GFP_KERNEL);
1043        if (unlikely(!pages)) {
1044                ret |= VM_FAULT_OOM;
1045                goto out;
1046        }
1047
1048        for (i = 0; i < HPAGE_PMD_NR; i++) {
1049                pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1050                                               __GFP_OTHER_NODE,
1051                                               vma, address, page_to_nid(page));
1052                if (unlikely(!pages[i] ||
1053                             mem_cgroup_newpage_charge(pages[i], mm,
1054                                                       GFP_KERNEL))) {
1055                        if (pages[i])
1056                                put_page(pages[i]);
1057                        mem_cgroup_uncharge_start();
1058                        while (--i >= 0) {
1059                                mem_cgroup_uncharge_page(pages[i]);
1060                                put_page(pages[i]);
1061                        }
1062                        mem_cgroup_uncharge_end();
1063                        kfree(pages);
1064                        ret |= VM_FAULT_OOM;
1065                        goto out;
1066                }
1067        }
1068
1069        for (i = 0; i < HPAGE_PMD_NR; i++) {
1070                copy_user_highpage(pages[i], page + i,
1071                                   haddr + PAGE_SIZE * i, vma);
1072                __SetPageUptodate(pages[i]);
1073                cond_resched();
1074        }
1075
1076        mmun_start = haddr;
1077        mmun_end   = haddr + HPAGE_PMD_SIZE;
1078        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1079
1080        spin_lock(&mm->page_table_lock);
1081        if (unlikely(!pmd_same(*pmd, orig_pmd)))
1082                goto out_free_pages;
1083        VM_BUG_ON(!PageHead(page));
1084
1085        pmdp_clear_flush(vma, haddr, pmd);
1086        /* leave pmd empty until pte is filled */
1087
1088        pgtable = pgtable_trans_huge_withdraw(mm);
1089        pmd_populate(mm, &_pmd, pgtable);
1090
1091        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1092                pte_t *pte, entry;
1093                entry = mk_pte(pages[i], vma->vm_page_prot);
1094                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1095                page_add_new_anon_rmap(pages[i], vma, haddr);
1096                pte = pte_offset_map(&_pmd, haddr);
1097                VM_BUG_ON(!pte_none(*pte));
1098                set_pte_at(mm, haddr, pte, entry);
1099                pte_unmap(pte);
1100        }
1101        kfree(pages);
1102
1103        smp_wmb(); /* make pte visible before pmd */
1104        pmd_populate(mm, pmd, pgtable);
1105        page_remove_rmap(page);
1106        spin_unlock(&mm->page_table_lock);
1107
1108        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1109
1110        ret |= VM_FAULT_WRITE;
1111        put_page(page);
1112
1113out:
1114        return ret;
1115
1116out_free_pages:
1117        spin_unlock(&mm->page_table_lock);
1118        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1119        mem_cgroup_uncharge_start();
1120        for (i = 0; i < HPAGE_PMD_NR; i++) {
1121                mem_cgroup_uncharge_page(pages[i]);
1122                put_page(pages[i]);
1123        }
1124        mem_cgroup_uncharge_end();
1125        kfree(pages);
1126        goto out;
1127}
1128
1129int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1130                        unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1131{
1132        int ret = 0;
1133        struct page *page = NULL, *new_page;
1134        unsigned long haddr;
1135        unsigned long mmun_start;       /* For mmu_notifiers */
1136        unsigned long mmun_end;         /* For mmu_notifiers */
1137
1138        VM_BUG_ON(!vma->anon_vma);
1139        haddr = address & HPAGE_PMD_MASK;
1140        if (is_huge_zero_pmd(orig_pmd))
1141                goto alloc;
1142        spin_lock(&mm->page_table_lock);
1143        if (unlikely(!pmd_same(*pmd, orig_pmd)))
1144                goto out_unlock;
1145
1146        page = pmd_page(orig_pmd);
1147        VM_BUG_ON(!PageCompound(page) || !PageHead(page));
1148        if (page_mapcount(page) == 1) {
1149                pmd_t entry;
1150                entry = pmd_mkyoung(orig_pmd);
1151                entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1152                if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1153                        update_mmu_cache_pmd(vma, address, pmd);
1154                ret |= VM_FAULT_WRITE;
1155                goto out_unlock;
1156        }
1157        get_page(page);
1158        spin_unlock(&mm->page_table_lock);
1159alloc:
1160        if (transparent_hugepage_enabled(vma) &&
1161            !transparent_hugepage_debug_cow())
1162                new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1163                                              vma, haddr, numa_node_id(), 0);
1164        else
1165                new_page = NULL;
1166
1167        if (unlikely(!new_page)) {
1168                count_vm_event(THP_FAULT_FALLBACK);
1169                if (is_huge_zero_pmd(orig_pmd)) {
1170                        ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1171                                        address, pmd, orig_pmd, haddr);
1172                } else {
1173                        ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1174                                        pmd, orig_pmd, page, haddr);
1175                        if (ret & VM_FAULT_OOM)
1176                                split_huge_page(page);
1177                        put_page(page);
1178                }
1179                goto out;
1180        }
1181        count_vm_event(THP_FAULT_ALLOC);
1182
1183        if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1184                put_page(new_page);
1185                if (page) {
1186                        split_huge_page(page);
1187                        put_page(page);
1188                }
1189                ret |= VM_FAULT_OOM;
1190                goto out;
1191        }
1192
1193        if (is_huge_zero_pmd(orig_pmd))
1194                clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1195        else
1196                copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1197        __SetPageUptodate(new_page);
1198
1199        mmun_start = haddr;
1200        mmun_end   = haddr + HPAGE_PMD_SIZE;
1201        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1202
1203        spin_lock(&mm->page_table_lock);
1204        if (page)
1205                put_page(page);
1206        if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1207                spin_unlock(&mm->page_table_lock);
1208                mem_cgroup_uncharge_page(new_page);
1209                put_page(new_page);
1210                goto out_mn;
1211        } else {
1212                pmd_t entry;
1213                entry = mk_huge_pmd(new_page, vma);
1214                pmdp_clear_flush(vma, haddr, pmd);
1215                page_add_new_anon_rmap(new_page, vma, haddr);
1216                set_pmd_at(mm, haddr, pmd, entry);
1217                update_mmu_cache_pmd(vma, address, pmd);
1218                if (is_huge_zero_pmd(orig_pmd)) {
1219                        add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1220                        put_huge_zero_page();
1221                } else {
1222                        VM_BUG_ON(!PageHead(page));
1223                        page_remove_rmap(page);
1224                        put_page(page);
1225                }
1226                ret |= VM_FAULT_WRITE;
1227        }
1228        spin_unlock(&mm->page_table_lock);
1229out_mn:
1230        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1231out:
1232        return ret;
1233out_unlock:
1234        spin_unlock(&mm->page_table_lock);
1235        return ret;
1236}
1237
1238struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1239                                   unsigned long addr,
1240                                   pmd_t *pmd,
1241                                   unsigned int flags)
1242{
1243        struct mm_struct *mm = vma->vm_mm;
1244        struct page *page = NULL;
1245
1246        assert_spin_locked(&mm->page_table_lock);
1247
1248        if (flags & FOLL_WRITE && !pmd_write(*pmd))
1249                goto out;
1250
1251        /* Avoid dumping huge zero page */
1252        if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1253                return ERR_PTR(-EFAULT);
1254
1255        page = pmd_page(*pmd);
1256        VM_BUG_ON(!PageHead(page));
1257        if (flags & FOLL_TOUCH) {
1258                pmd_t _pmd;
1259                /*
1260                 * We should set the dirty bit only for FOLL_WRITE but
1261                 * for now the dirty bit in the pmd is meaningless.
1262                 * And if the dirty bit will become meaningful and
1263                 * we'll only set it with FOLL_WRITE, an atomic
1264                 * set_bit will be required on the pmd to set the
1265                 * young bit, instead of the current set_pmd_at.
1266                 */
1267                _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1268                set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1269        }
1270        if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1271                if (page->mapping && trylock_page(page)) {
1272                        lru_add_drain();
1273                        if (page->mapping)
1274                                mlock_vma_page(page);
1275                        unlock_page(page);
1276                }
1277        }
1278        page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1279        VM_BUG_ON(!PageCompound(page));
1280        if (flags & FOLL_GET)
1281                get_page_foll(page);
1282
1283out:
1284        return page;
1285}
1286
1287/* NUMA hinting page fault entry point for trans huge pmds */
1288int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1289                                unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1290{
1291        struct page *page;
1292        unsigned long haddr = addr & HPAGE_PMD_MASK;
1293        int target_nid;
1294        int current_nid = -1;
1295        bool migrated;
1296
1297        spin_lock(&mm->page_table_lock);
1298        if (unlikely(!pmd_same(pmd, *pmdp)))
1299                goto out_unlock;
1300
1301        page = pmd_page(pmd);
1302        get_page(page);
1303        current_nid = page_to_nid(page);
1304        count_vm_numa_event(NUMA_HINT_FAULTS);
1305        if (current_nid == numa_node_id())
1306                count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1307
1308        target_nid = mpol_misplaced(page, vma, haddr);
1309        if (target_nid == -1) {
1310                put_page(page);
1311                goto clear_pmdnuma;
1312        }
1313
1314        /* Acquire the page lock to serialise THP migrations */
1315        spin_unlock(&mm->page_table_lock);
1316        lock_page(page);
1317
1318        /* Confirm the PTE did not while locked */
1319        spin_lock(&mm->page_table_lock);
1320        if (unlikely(!pmd_same(pmd, *pmdp))) {
1321                unlock_page(page);
1322                put_page(page);
1323                goto out_unlock;
1324        }
1325        spin_unlock(&mm->page_table_lock);
1326
1327        /* Migrate the THP to the requested node */
1328        migrated = migrate_misplaced_transhuge_page(mm, vma,
1329                                pmdp, pmd, addr, page, target_nid);
1330        if (!migrated)
1331                goto check_same;
1332
1333        task_numa_fault(target_nid, HPAGE_PMD_NR, true);
1334        return 0;
1335
1336check_same:
1337        spin_lock(&mm->page_table_lock);
1338        if (unlikely(!pmd_same(pmd, *pmdp)))
1339                goto out_unlock;
1340clear_pmdnuma:
1341        pmd = pmd_mknonnuma(pmd);
1342        set_pmd_at(mm, haddr, pmdp, pmd);
1343        VM_BUG_ON(pmd_numa(*pmdp));
1344        update_mmu_cache_pmd(vma, addr, pmdp);
1345out_unlock:
1346        spin_unlock(&mm->page_table_lock);
1347        if (current_nid != -1)
1348                task_numa_fault(current_nid, HPAGE_PMD_NR, false);
1349        return 0;
1350}
1351
1352int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1353                 pmd_t *pmd, unsigned long addr)
1354{
1355        int ret = 0;
1356
1357        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1358                struct page *page;
1359                pgtable_t pgtable;
1360                pmd_t orig_pmd;
1361                pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1362                orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1363                tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1364                if (is_huge_zero_pmd(orig_pmd)) {
1365                        tlb->mm->nr_ptes--;
1366                        spin_unlock(&tlb->mm->page_table_lock);
1367                        put_huge_zero_page();
1368                } else {
1369                        page = pmd_page(orig_pmd);
1370                        page_remove_rmap(page);
1371                        VM_BUG_ON(page_mapcount(page) < 0);
1372                        add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1373                        VM_BUG_ON(!PageHead(page));
1374                        tlb->mm->nr_ptes--;
1375                        spin_unlock(&tlb->mm->page_table_lock);
1376                        tlb_remove_page(tlb, page);
1377                }
1378                pte_free(tlb->mm, pgtable);
1379                ret = 1;
1380        }
1381        return ret;
1382}
1383
1384int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1385                unsigned long addr, unsigned long end,
1386                unsigned char *vec)
1387{
1388        int ret = 0;
1389
1390        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1391                /*
1392                 * All logical pages in the range are present
1393                 * if backed by a huge page.
1394                 */
1395                spin_unlock(&vma->vm_mm->page_table_lock);
1396                memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1397                ret = 1;
1398        }
1399
1400        return ret;
1401}
1402
1403int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1404                  unsigned long old_addr,
1405                  unsigned long new_addr, unsigned long old_end,
1406                  pmd_t *old_pmd, pmd_t *new_pmd)
1407{
1408        int ret = 0;
1409        pmd_t pmd;
1410
1411        struct mm_struct *mm = vma->vm_mm;
1412
1413        if ((old_addr & ~HPAGE_PMD_MASK) ||
1414            (new_addr & ~HPAGE_PMD_MASK) ||
1415            old_end - old_addr < HPAGE_PMD_SIZE ||
1416            (new_vma->vm_flags & VM_NOHUGEPAGE))
1417                goto out;
1418
1419        /*
1420         * The destination pmd shouldn't be established, free_pgtables()
1421         * should have release it.
1422         */
1423        if (WARN_ON(!pmd_none(*new_pmd))) {
1424                VM_BUG_ON(pmd_trans_huge(*new_pmd));
1425                goto out;
1426        }
1427
1428        ret = __pmd_trans_huge_lock(old_pmd, vma);
1429        if (ret == 1) {
1430                pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1431                VM_BUG_ON(!pmd_none(*new_pmd));
1432                set_pmd_at(mm, new_addr, new_pmd, pmd);
1433                spin_unlock(&mm->page_table_lock);
1434        }
1435out:
1436        return ret;
1437}
1438
1439int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1440                unsigned long addr, pgprot_t newprot, int prot_numa)
1441{
1442        struct mm_struct *mm = vma->vm_mm;
1443        int ret = 0;
1444
1445        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1446                pmd_t entry;
1447                entry = pmdp_get_and_clear(mm, addr, pmd);
1448                if (!prot_numa) {
1449                        entry = pmd_modify(entry, newprot);
1450                        BUG_ON(pmd_write(entry));
1451                } else {
1452                        struct page *page = pmd_page(*pmd);
1453
1454                        /* only check non-shared pages */
1455                        if (page_mapcount(page) == 1 &&
1456                            !pmd_numa(*pmd)) {
1457                                entry = pmd_mknuma(entry);
1458                        }
1459                }
1460                set_pmd_at(mm, addr, pmd, entry);
1461                spin_unlock(&vma->vm_mm->page_table_lock);
1462                ret = 1;
1463        }
1464
1465        return ret;
1466}
1467
1468/*
1469 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1470 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1471 *
1472 * Note that if it returns 1, this routine returns without unlocking page
1473 * table locks. So callers must unlock them.
1474 */
1475int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1476{
1477        spin_lock(&vma->vm_mm->page_table_lock);
1478        if (likely(pmd_trans_huge(*pmd))) {
1479                if (unlikely(pmd_trans_splitting(*pmd))) {
1480                        spin_unlock(&vma->vm_mm->page_table_lock);
1481                        wait_split_huge_page(vma->anon_vma, pmd);
1482                        return -1;
1483                } else {
1484                        /* Thp mapped by 'pmd' is stable, so we can
1485                         * handle it as it is. */
1486                        return 1;
1487                }
1488        }
1489        spin_unlock(&vma->vm_mm->page_table_lock);
1490        return 0;
1491}
1492
1493pmd_t *page_check_address_pmd(struct page *page,
1494                              struct mm_struct *mm,
1495                              unsigned long address,
1496                              enum page_check_address_pmd_flag flag)
1497{
1498        pmd_t *pmd, *ret = NULL;
1499
1500        if (address & ~HPAGE_PMD_MASK)
1501                goto out;
1502
1503        pmd = mm_find_pmd(mm, address);
1504        if (!pmd)
1505                goto out;
1506        if (pmd_none(*pmd))
1507                goto out;
1508        if (pmd_page(*pmd) != page)
1509                goto out;
1510        /*
1511         * split_vma() may create temporary aliased mappings. There is
1512         * no risk as long as all huge pmd are found and have their
1513         * splitting bit set before __split_huge_page_refcount
1514         * runs. Finding the same huge pmd more than once during the
1515         * same rmap walk is not a problem.
1516         */
1517        if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1518            pmd_trans_splitting(*pmd))
1519                goto out;
1520        if (pmd_trans_huge(*pmd)) {
1521                VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1522                          !pmd_trans_splitting(*pmd));
1523                ret = pmd;
1524        }
1525out:
1526        return ret;
1527}
1528
1529static int __split_huge_page_splitting(struct page *page,
1530                                       struct vm_area_struct *vma,
1531                                       unsigned long address)
1532{
1533        struct mm_struct *mm = vma->vm_mm;
1534        pmd_t *pmd;
1535        int ret = 0;
1536        /* For mmu_notifiers */
1537        const unsigned long mmun_start = address;
1538        const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1539
1540        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1541        spin_lock(&mm->page_table_lock);
1542        pmd = page_check_address_pmd(page, mm, address,
1543                                     PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1544        if (pmd) {
1545                /*
1546                 * We can't temporarily set the pmd to null in order
1547                 * to split it, the pmd must remain marked huge at all
1548                 * times or the VM won't take the pmd_trans_huge paths
1549                 * and it won't wait on the anon_vma->root->rwsem to
1550                 * serialize against split_huge_page*.
1551                 */
1552                pmdp_splitting_flush(vma, address, pmd);
1553                ret = 1;
1554        }
1555        spin_unlock(&mm->page_table_lock);
1556        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1557
1558        return ret;
1559}
1560
1561static void __split_huge_page_refcount(struct page *page,
1562                                       struct list_head *list)
1563{
1564        int i;
1565        struct zone *zone = page_zone(page);
1566        struct lruvec *lruvec;
1567        int tail_count = 0;
1568
1569        /* prevent PageLRU to go away from under us, and freeze lru stats */
1570        spin_lock_irq(&zone->lru_lock);
1571        lruvec = mem_cgroup_page_lruvec(page, zone);
1572
1573        compound_lock(page);
1574        /* complete memcg works before add pages to LRU */
1575        mem_cgroup_split_huge_fixup(page);
1576
1577        for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1578                struct page *page_tail = page + i;
1579
1580                /* tail_page->_mapcount cannot change */
1581                BUG_ON(page_mapcount(page_tail) < 0);
1582                tail_count += page_mapcount(page_tail);
1583                /* check for overflow */
1584                BUG_ON(tail_count < 0);
1585                BUG_ON(atomic_read(&page_tail->_count) != 0);
1586                /*
1587                 * tail_page->_count is zero and not changing from
1588                 * under us. But get_page_unless_zero() may be running
1589                 * from under us on the tail_page. If we used
1590                 * atomic_set() below instead of atomic_add(), we
1591                 * would then run atomic_set() concurrently with
1592                 * get_page_unless_zero(), and atomic_set() is
1593                 * implemented in C not using locked ops. spin_unlock
1594                 * on x86 sometime uses locked ops because of PPro
1595                 * errata 66, 92, so unless somebody can guarantee
1596                 * atomic_set() here would be safe on all archs (and
1597                 * not only on x86), it's safer to use atomic_add().
1598                 */
1599                atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1600                           &page_tail->_count);
1601
1602                /* after clearing PageTail the gup refcount can be released */
1603                smp_mb();
1604
1605                /*
1606                 * retain hwpoison flag of the poisoned tail page:
1607                 *   fix for the unsuitable process killed on Guest Machine(KVM)
1608                 *   by the memory-failure.
1609                 */
1610                page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1611                page_tail->flags |= (page->flags &
1612                                     ((1L << PG_referenced) |
1613                                      (1L << PG_swapbacked) |
1614                                      (1L << PG_mlocked) |
1615                                      (1L << PG_uptodate)));
1616                page_tail->flags |= (1L << PG_dirty);
1617
1618                /* clear PageTail before overwriting first_page */
1619                smp_wmb();
1620
1621                /*
1622                 * __split_huge_page_splitting() already set the
1623                 * splitting bit in all pmd that could map this
1624                 * hugepage, that will ensure no CPU can alter the
1625                 * mapcount on the head page. The mapcount is only
1626                 * accounted in the head page and it has to be
1627                 * transferred to all tail pages in the below code. So
1628                 * for this code to be safe, the split the mapcount
1629                 * can't change. But that doesn't mean userland can't
1630                 * keep changing and reading the page contents while
1631                 * we transfer the mapcount, so the pmd splitting
1632                 * status is achieved setting a reserved bit in the
1633                 * pmd, not by clearing the present bit.
1634                */
1635                page_tail->_mapcount = page->_mapcount;
1636
1637                BUG_ON(page_tail->mapping);
1638                page_tail->mapping = page->mapping;
1639
1640                page_tail->index = page->index + i;
1641                page_nid_xchg_last(page_tail, page_nid_last(page));
1642
1643                BUG_ON(!PageAnon(page_tail));
1644                BUG_ON(!PageUptodate(page_tail));
1645                BUG_ON(!PageDirty(page_tail));
1646                BUG_ON(!PageSwapBacked(page_tail));
1647
1648                lru_add_page_tail(page, page_tail, lruvec, list);
1649        }
1650        atomic_sub(tail_count, &page->_count);
1651        BUG_ON(atomic_read(&page->_count) <= 0);
1652
1653        __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1654        __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1655
1656        ClearPageCompound(page);
1657        compound_unlock(page);
1658        spin_unlock_irq(&zone->lru_lock);
1659
1660        for (i = 1; i < HPAGE_PMD_NR; i++) {
1661                struct page *page_tail = page + i;
1662                BUG_ON(page_count(page_tail) <= 0);
1663                /*
1664                 * Tail pages may be freed if there wasn't any mapping
1665                 * like if add_to_swap() is running on a lru page that
1666                 * had its mapping zapped. And freeing these pages
1667                 * requires taking the lru_lock so we do the put_page
1668                 * of the tail pages after the split is complete.
1669                 */
1670                put_page(page_tail);
1671        }
1672
1673        /*
1674         * Only the head page (now become a regular page) is required
1675         * to be pinned by the caller.
1676         */
1677        BUG_ON(page_count(page) <= 0);
1678}
1679
1680static int __split_huge_page_map(struct page *page,
1681                                 struct vm_area_struct *vma,
1682                                 unsigned long address)
1683{
1684        struct mm_struct *mm = vma->vm_mm;
1685        pmd_t *pmd, _pmd;
1686        int ret = 0, i;
1687        pgtable_t pgtable;
1688        unsigned long haddr;
1689
1690        spin_lock(&mm->page_table_lock);
1691        pmd = page_check_address_pmd(page, mm, address,
1692                                     PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1693        if (pmd) {
1694                pgtable = pgtable_trans_huge_withdraw(mm);
1695                pmd_populate(mm, &_pmd, pgtable);
1696
1697                haddr = address;
1698                for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1699                        pte_t *pte, entry;
1700                        BUG_ON(PageCompound(page+i));
1701                        entry = mk_pte(page + i, vma->vm_page_prot);
1702                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1703                        if (!pmd_write(*pmd))
1704                                entry = pte_wrprotect(entry);
1705                        else
1706                                BUG_ON(page_mapcount(page) != 1);
1707                        if (!pmd_young(*pmd))
1708                                entry = pte_mkold(entry);
1709                        if (pmd_numa(*pmd))
1710                                entry = pte_mknuma(entry);
1711                        pte = pte_offset_map(&_pmd, haddr);
1712                        BUG_ON(!pte_none(*pte));
1713                        set_pte_at(mm, haddr, pte, entry);
1714                        pte_unmap(pte);
1715                }
1716
1717                smp_wmb(); /* make pte visible before pmd */
1718                /*
1719                 * Up to this point the pmd is present and huge and
1720                 * userland has the whole access to the hugepage
1721                 * during the split (which happens in place). If we
1722                 * overwrite the pmd with the not-huge version
1723                 * pointing to the pte here (which of course we could
1724                 * if all CPUs were bug free), userland could trigger
1725                 * a small page size TLB miss on the small sized TLB
1726                 * while the hugepage TLB entry is still established
1727                 * in the huge TLB. Some CPU doesn't like that. See
1728                 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1729                 * Erratum 383 on page 93. Intel should be safe but is
1730                 * also warns that it's only safe if the permission
1731                 * and cache attributes of the two entries loaded in
1732                 * the two TLB is identical (which should be the case
1733                 * here). But it is generally safer to never allow
1734                 * small and huge TLB entries for the same virtual
1735                 * address to be loaded simultaneously. So instead of
1736                 * doing "pmd_populate(); flush_tlb_range();" we first
1737                 * mark the current pmd notpresent (atomically because
1738                 * here the pmd_trans_huge and pmd_trans_splitting
1739                 * must remain set at all times on the pmd until the
1740                 * split is complete for this pmd), then we flush the
1741                 * SMP TLB and finally we write the non-huge version
1742                 * of the pmd entry with pmd_populate.
1743                 */
1744                pmdp_invalidate(vma, address, pmd);
1745                pmd_populate(mm, pmd, pgtable);
1746                ret = 1;
1747        }
1748        spin_unlock(&mm->page_table_lock);
1749
1750        return ret;
1751}
1752
1753/* must be called with anon_vma->root->rwsem held */
1754static void __split_huge_page(struct page *page,
1755                              struct anon_vma *anon_vma,
1756                              struct list_head *list)
1757{
1758        int mapcount, mapcount2;
1759        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1760        struct anon_vma_chain *avc;
1761
1762        BUG_ON(!PageHead(page));
1763        BUG_ON(PageTail(page));
1764
1765        mapcount = 0;
1766        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1767                struct vm_area_struct *vma = avc->vma;
1768                unsigned long addr = vma_address(page, vma);
1769                BUG_ON(is_vma_temporary_stack(vma));
1770                mapcount += __split_huge_page_splitting(page, vma, addr);
1771        }
1772        /*
1773         * It is critical that new vmas are added to the tail of the
1774         * anon_vma list. This guarantes that if copy_huge_pmd() runs
1775         * and establishes a child pmd before
1776         * __split_huge_page_splitting() freezes the parent pmd (so if
1777         * we fail to prevent copy_huge_pmd() from running until the
1778         * whole __split_huge_page() is complete), we will still see
1779         * the newly established pmd of the child later during the
1780         * walk, to be able to set it as pmd_trans_splitting too.
1781         */
1782        if (mapcount != page_mapcount(page))
1783                printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1784                       mapcount, page_mapcount(page));
1785        BUG_ON(mapcount != page_mapcount(page));
1786
1787        __split_huge_page_refcount(page, list);
1788
1789        mapcount2 = 0;
1790        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1791                struct vm_area_struct *vma = avc->vma;
1792                unsigned long addr = vma_address(page, vma);
1793                BUG_ON(is_vma_temporary_stack(vma));
1794                mapcount2 += __split_huge_page_map(page, vma, addr);
1795        }
1796        if (mapcount != mapcount2)
1797                printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1798                       mapcount, mapcount2, page_mapcount(page));
1799        BUG_ON(mapcount != mapcount2);
1800}
1801
1802/*
1803 * Split a hugepage into normal pages. This doesn't change the position of head
1804 * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1805 * @list. Both head page and tail pages will inherit mapping, flags, and so on
1806 * from the hugepage.
1807 * Return 0 if the hugepage is split successfully otherwise return 1.
1808 */
1809int split_huge_page_to_list(struct page *page, struct list_head *list)
1810{
1811        struct anon_vma *anon_vma;
1812        int ret = 1;
1813
1814        BUG_ON(is_huge_zero_page(page));
1815        BUG_ON(!PageAnon(page));
1816
1817        /*
1818         * The caller does not necessarily hold an mmap_sem that would prevent
1819         * the anon_vma disappearing so we first we take a reference to it
1820         * and then lock the anon_vma for write. This is similar to
1821         * page_lock_anon_vma_read except the write lock is taken to serialise
1822         * against parallel split or collapse operations.
1823         */
1824        anon_vma = page_get_anon_vma(page);
1825        if (!anon_vma)
1826                goto out;
1827        anon_vma_lock_write(anon_vma);
1828
1829        ret = 0;
1830        if (!PageCompound(page))
1831                goto out_unlock;
1832
1833        BUG_ON(!PageSwapBacked(page));
1834        __split_huge_page(page, anon_vma, list);
1835        count_vm_event(THP_SPLIT);
1836
1837        BUG_ON(PageCompound(page));
1838out_unlock:
1839        anon_vma_unlock_write(anon_vma);
1840        put_anon_vma(anon_vma);
1841out:
1842        return ret;
1843}
1844
1845#define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1846
1847int hugepage_madvise(struct vm_area_struct *vma,
1848                     unsigned long *vm_flags, int advice)
1849{
1850        struct mm_struct *mm = vma->vm_mm;
1851
1852        switch (advice) {
1853        case MADV_HUGEPAGE:
1854                /*
1855                 * Be somewhat over-protective like KSM for now!
1856                 */
1857                if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1858                        return -EINVAL;
1859                if (mm->def_flags & VM_NOHUGEPAGE)
1860                        return -EINVAL;
1861                *vm_flags &= ~VM_NOHUGEPAGE;
1862                *vm_flags |= VM_HUGEPAGE;
1863                /*
1864                 * If the vma become good for khugepaged to scan,
1865                 * register it here without waiting a page fault that
1866                 * may not happen any time soon.
1867                 */
1868                if (unlikely(khugepaged_enter_vma_merge(vma)))
1869                        return -ENOMEM;
1870                break;
1871        case MADV_NOHUGEPAGE:
1872                /*
1873                 * Be somewhat over-protective like KSM for now!
1874                 */
1875                if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1876                        return -EINVAL;
1877                *vm_flags &= ~VM_HUGEPAGE;
1878                *vm_flags |= VM_NOHUGEPAGE;
1879                /*
1880                 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1881                 * this vma even if we leave the mm registered in khugepaged if
1882                 * it got registered before VM_NOHUGEPAGE was set.
1883                 */
1884                break;
1885        }
1886
1887        return 0;
1888}
1889
1890static int __init khugepaged_slab_init(void)
1891{
1892        mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1893                                          sizeof(struct mm_slot),
1894                                          __alignof__(struct mm_slot), 0, NULL);
1895        if (!mm_slot_cache)
1896                return -ENOMEM;
1897
1898        return 0;
1899}
1900
1901static inline struct mm_slot *alloc_mm_slot(void)
1902{
1903        if (!mm_slot_cache)     /* initialization failed */
1904                return NULL;
1905        return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1906}
1907
1908static inline void free_mm_slot(struct mm_slot *mm_slot)
1909{
1910        kmem_cache_free(mm_slot_cache, mm_slot);
1911}
1912
1913static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1914{
1915        struct mm_slot *mm_slot;
1916
1917        hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1918                if (mm == mm_slot->mm)
1919                        return mm_slot;
1920
1921        return NULL;
1922}
1923
1924static void insert_to_mm_slots_hash(struct mm_struct *mm,
1925                                    struct mm_slot *mm_slot)
1926{
1927        mm_slot->mm = mm;
1928        hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1929}
1930
1931static inline int khugepaged_test_exit(struct mm_struct *mm)
1932{
1933        return atomic_read(&mm->mm_users) == 0;
1934}
1935
1936int __khugepaged_enter(struct mm_struct *mm)
1937{
1938        struct mm_slot *mm_slot;
1939        int wakeup;
1940
1941        mm_slot = alloc_mm_slot();
1942        if (!mm_slot)
1943                return -ENOMEM;
1944
1945        /* __khugepaged_exit() must not run from under us */
1946        VM_BUG_ON(khugepaged_test_exit(mm));
1947        if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1948                free_mm_slot(mm_slot);
1949                return 0;
1950        }
1951
1952        spin_lock(&khugepaged_mm_lock);
1953        insert_to_mm_slots_hash(mm, mm_slot);
1954        /*
1955         * Insert just behind the scanning cursor, to let the area settle
1956         * down a little.
1957         */
1958        wakeup = list_empty(&khugepaged_scan.mm_head);
1959        list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1960        spin_unlock(&khugepaged_mm_lock);
1961
1962        atomic_inc(&mm->mm_count);
1963        if (wakeup)
1964                wake_up_interruptible(&khugepaged_wait);
1965
1966        return 0;
1967}
1968
1969int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1970{
1971        unsigned long hstart, hend;
1972        if (!vma->anon_vma)
1973                /*
1974                 * Not yet faulted in so we will register later in the
1975                 * page fault if needed.
1976                 */
1977                return 0;
1978        if (vma->vm_ops)
1979                /* khugepaged not yet working on file or special mappings */
1980                return 0;
1981        VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1982        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1983        hend = vma->vm_end & HPAGE_PMD_MASK;
1984        if (hstart < hend)
1985                return khugepaged_enter(vma);
1986        return 0;
1987}
1988
1989void __khugepaged_exit(struct mm_struct *mm)
1990{
1991        struct mm_slot *mm_slot;
1992        int free = 0;
1993
1994        spin_lock(&khugepaged_mm_lock);
1995        mm_slot = get_mm_slot(mm);
1996        if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1997                hash_del(&mm_slot->hash);
1998                list_del(&mm_slot->mm_node);
1999                free = 1;
2000        }
2001        spin_unlock(&khugepaged_mm_lock);
2002
2003        if (free) {
2004                clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2005                free_mm_slot(mm_slot);
2006                mmdrop(mm);
2007        } else if (mm_slot) {
2008                /*
2009                 * This is required to serialize against
2010                 * khugepaged_test_exit() (which is guaranteed to run
2011                 * under mmap sem read mode). Stop here (after we
2012                 * return all pagetables will be destroyed) until
2013                 * khugepaged has finished working on the pagetables
2014                 * under the mmap_sem.
2015                 */
2016                down_write(&mm->mmap_sem);
2017                up_write(&mm->mmap_sem);
2018        }
2019}
2020
2021static void release_pte_page(struct page *page)
2022{
2023        /* 0 stands for page_is_file_cache(page) == false */
2024        dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2025        unlock_page(page);
2026        putback_lru_page(page);
2027}
2028
2029static void release_pte_pages(pte_t *pte, pte_t *_pte)
2030{
2031        while (--_pte >= pte) {
2032                pte_t pteval = *_pte;
2033                if (!pte_none(pteval))
2034                        release_pte_page(pte_page(pteval));
2035        }
2036}
2037
2038static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2039                                        unsigned long address,
2040                                        pte_t *pte)
2041{
2042        struct page *page;
2043        pte_t *_pte;
2044        int referenced = 0, none = 0;
2045        for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2046             _pte++, address += PAGE_SIZE) {
2047                pte_t pteval = *_pte;
2048                if (pte_none(pteval)) {
2049                        if (++none <= khugepaged_max_ptes_none)
2050                                continue;
2051                        else
2052                                goto out;
2053                }
2054                if (!pte_present(pteval) || !pte_write(pteval))
2055                        goto out;
2056                page = vm_normal_page(vma, address, pteval);
2057                if (unlikely(!page))
2058                        goto out;
2059
2060                VM_BUG_ON(PageCompound(page));
2061                BUG_ON(!PageAnon(page));
2062                VM_BUG_ON(!PageSwapBacked(page));
2063
2064                /* cannot use mapcount: can't collapse if there's a gup pin */
2065                if (page_count(page) != 1)
2066                        goto out;
2067                /*
2068                 * We can do it before isolate_lru_page because the
2069                 * page can't be freed from under us. NOTE: PG_lock
2070                 * is needed to serialize against split_huge_page
2071                 * when invoked from the VM.
2072                 */
2073                if (!trylock_page(page))
2074                        goto out;
2075                /*
2076                 * Isolate the page to avoid collapsing an hugepage
2077                 * currently in use by the VM.
2078                 */
2079                if (isolate_lru_page(page)) {
2080                        unlock_page(page);
2081                        goto out;
2082                }
2083                /* 0 stands for page_is_file_cache(page) == false */
2084                inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2085                VM_BUG_ON(!PageLocked(page));
2086                VM_BUG_ON(PageLRU(page));
2087
2088                /* If there is no mapped pte young don't collapse the page */
2089                if (pte_young(pteval) || PageReferenced(page) ||
2090                    mmu_notifier_test_young(vma->vm_mm, address))
2091                        referenced = 1;
2092        }
2093        if (likely(referenced))
2094                return 1;
2095out:
2096        release_pte_pages(pte, _pte);
2097        return 0;
2098}
2099
2100static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2101                                      struct vm_area_struct *vma,
2102                                      unsigned long address,
2103                                      spinlock_t *ptl)
2104{
2105        pte_t *_pte;
2106        for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2107                pte_t pteval = *_pte;
2108                struct page *src_page;
2109
2110                if (pte_none(pteval)) {
2111                        clear_user_highpage(page, address);
2112                        add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2113                } else {
2114                        src_page = pte_page(pteval);
2115                        copy_user_highpage(page, src_page, address, vma);
2116                        VM_BUG_ON(page_mapcount(src_page) != 1);
2117                        release_pte_page(src_page);
2118                        /*
2119                         * ptl mostly unnecessary, but preempt has to
2120                         * be disabled to update the per-cpu stats
2121                         * inside page_remove_rmap().
2122                         */
2123                        spin_lock(ptl);
2124                        /*
2125                         * paravirt calls inside pte_clear here are
2126                         * superfluous.
2127                         */
2128                        pte_clear(vma->vm_mm, address, _pte);
2129                        page_remove_rmap(src_page);
2130                        spin_unlock(ptl);
2131                        free_page_and_swap_cache(src_page);
2132                }
2133
2134                address += PAGE_SIZE;
2135                page++;
2136        }
2137}
2138
2139static void khugepaged_alloc_sleep(void)
2140{
2141        wait_event_freezable_timeout(khugepaged_wait, false,
2142                        msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2143}
2144
2145#ifdef CONFIG_NUMA
2146static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2147{
2148        if (IS_ERR(*hpage)) {
2149                if (!*wait)
2150                        return false;
2151
2152                *wait = false;
2153                *hpage = NULL;
2154                khugepaged_alloc_sleep();
2155        } else if (*hpage) {
2156                put_page(*hpage);
2157                *hpage = NULL;
2158        }
2159
2160        return true;
2161}
2162
2163static struct page
2164*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2165                       struct vm_area_struct *vma, unsigned long address,
2166                       int node)
2167{
2168        VM_BUG_ON(*hpage);
2169        /*
2170         * Allocate the page while the vma is still valid and under
2171         * the mmap_sem read mode so there is no memory allocation
2172         * later when we take the mmap_sem in write mode. This is more
2173         * friendly behavior (OTOH it may actually hide bugs) to
2174         * filesystems in userland with daemons allocating memory in
2175         * the userland I/O paths.  Allocating memory with the
2176         * mmap_sem in read mode is good idea also to allow greater
2177         * scalability.
2178         */
2179        *hpage  = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2180                                      node, __GFP_OTHER_NODE);
2181
2182        /*
2183         * After allocating the hugepage, release the mmap_sem read lock in
2184         * preparation for taking it in write mode.
2185         */
2186        up_read(&mm->mmap_sem);
2187        if (unlikely(!*hpage)) {
2188                count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2189                *hpage = ERR_PTR(-ENOMEM);
2190                return NULL;
2191        }
2192
2193        count_vm_event(THP_COLLAPSE_ALLOC);
2194        return *hpage;
2195}
2196#else
2197static struct page *khugepaged_alloc_hugepage(bool *wait)
2198{
2199        struct page *hpage;
2200
2201        do {
2202                hpage = alloc_hugepage(khugepaged_defrag());
2203                if (!hpage) {
2204                        count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2205                        if (!*wait)
2206                                return NULL;
2207
2208                        *wait = false;
2209                        khugepaged_alloc_sleep();
2210                } else
2211                        count_vm_event(THP_COLLAPSE_ALLOC);
2212        } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2213
2214        return hpage;
2215}
2216
2217static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2218{
2219        if (!*hpage)
2220                *hpage = khugepaged_alloc_hugepage(wait);
2221
2222        if (unlikely(!*hpage))
2223                return false;
2224
2225        return true;
2226}
2227
2228static struct page
2229*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2230                       struct vm_area_struct *vma, unsigned long address,
2231                       int node)
2232{
2233        up_read(&mm->mmap_sem);
2234        VM_BUG_ON(!*hpage);
2235        return  *hpage;
2236}
2237#endif
2238
2239static bool hugepage_vma_check(struct vm_area_struct *vma)
2240{
2241        if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2242            (vma->vm_flags & VM_NOHUGEPAGE))
2243                return false;
2244
2245        if (!vma->anon_vma || vma->vm_ops)
2246                return false;
2247        if (is_vma_temporary_stack(vma))
2248                return false;
2249        VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2250        return true;
2251}
2252
2253static void collapse_huge_page(struct mm_struct *mm,
2254                                   unsigned long address,
2255                                   struct page **hpage,
2256                                   struct vm_area_struct *vma,
2257                                   int node)
2258{
2259        pmd_t *pmd, _pmd;
2260        pte_t *pte;
2261        pgtable_t pgtable;
2262        struct page *new_page;
2263        spinlock_t *ptl;
2264        int isolated;
2265        unsigned long hstart, hend;
2266        unsigned long mmun_start;       /* For mmu_notifiers */
2267        unsigned long mmun_end;         /* For mmu_notifiers */
2268
2269        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2270
2271        /* release the mmap_sem read lock. */
2272        new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2273        if (!new_page)
2274                return;
2275
2276        if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2277                return;
2278
2279        /*
2280         * Prevent all access to pagetables with the exception of
2281         * gup_fast later hanlded by the ptep_clear_flush and the VM
2282         * handled by the anon_vma lock + PG_lock.
2283         */
2284        down_write(&mm->mmap_sem);
2285        if (unlikely(khugepaged_test_exit(mm)))
2286                goto out;
2287
2288        vma = find_vma(mm, address);
2289        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2290        hend = vma->vm_end & HPAGE_PMD_MASK;
2291        if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2292                goto out;
2293        if (!hugepage_vma_check(vma))
2294                goto out;
2295        pmd = mm_find_pmd(mm, address);
2296        if (!pmd)
2297                goto out;
2298        if (pmd_trans_huge(*pmd))
2299                goto out;
2300
2301        anon_vma_lock_write(vma->anon_vma);
2302
2303        pte = pte_offset_map(pmd, address);
2304        ptl = pte_lockptr(mm, pmd);
2305
2306        mmun_start = address;
2307        mmun_end   = address + HPAGE_PMD_SIZE;
2308        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2309        spin_lock(&mm->page_table_lock); /* probably unnecessary */
2310        /*
2311         * After this gup_fast can't run anymore. This also removes
2312         * any huge TLB entry from the CPU so we won't allow
2313         * huge and small TLB entries for the same virtual address
2314         * to avoid the risk of CPU bugs in that area.
2315         */
2316        _pmd = pmdp_clear_flush(vma, address, pmd);
2317        spin_unlock(&mm->page_table_lock);
2318        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2319
2320        spin_lock(ptl);
2321        isolated = __collapse_huge_page_isolate(vma, address, pte);
2322        spin_unlock(ptl);
2323
2324        if (unlikely(!isolated)) {
2325                pte_unmap(pte);
2326                spin_lock(&mm->page_table_lock);
2327                BUG_ON(!pmd_none(*pmd));
2328                /*
2329                 * We can only use set_pmd_at when establishing
2330                 * hugepmds and never for establishing regular pmds that
2331                 * points to regular pagetables. Use pmd_populate for that
2332                 */
2333                pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2334                spin_unlock(&mm->page_table_lock);
2335                anon_vma_unlock_write(vma->anon_vma);
2336                goto out;
2337        }
2338
2339        /*
2340         * All pages are isolated and locked so anon_vma rmap
2341         * can't run anymore.
2342         */
2343        anon_vma_unlock_write(vma->anon_vma);
2344
2345        __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2346        pte_unmap(pte);
2347        __SetPageUptodate(new_page);
2348        pgtable = pmd_pgtable(_pmd);
2349
2350        _pmd = mk_huge_pmd(new_page, vma);
2351
2352        /*
2353         * spin_lock() below is not the equivalent of smp_wmb(), so
2354         * this is needed to avoid the copy_huge_page writes to become
2355         * visible after the set_pmd_at() write.
2356         */
2357        smp_wmb();
2358
2359        spin_lock(&mm->page_table_lock);
2360        BUG_ON(!pmd_none(*pmd));
2361        page_add_new_anon_rmap(new_page, vma, address);
2362        set_pmd_at(mm, address, pmd, _pmd);
2363        update_mmu_cache_pmd(vma, address, pmd);
2364        pgtable_trans_huge_deposit(mm, pgtable);
2365        spin_unlock(&mm->page_table_lock);
2366
2367        *hpage = NULL;
2368
2369        khugepaged_pages_collapsed++;
2370out_up_write:
2371        up_write(&mm->mmap_sem);
2372        return;
2373
2374out:
2375        mem_cgroup_uncharge_page(new_page);
2376        goto out_up_write;
2377}
2378
2379static int khugepaged_scan_pmd(struct mm_struct *mm,
2380                               struct vm_area_struct *vma,
2381                               unsigned long address,
2382                               struct page **hpage)
2383{
2384        pmd_t *pmd;
2385        pte_t *pte, *_pte;
2386        int ret = 0, referenced = 0, none = 0;
2387        struct page *page;
2388        unsigned long _address;
2389        spinlock_t *ptl;
2390        int node = NUMA_NO_NODE;
2391
2392        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2393
2394        pmd = mm_find_pmd(mm, address);
2395        if (!pmd)
2396                goto out;
2397        if (pmd_trans_huge(*pmd))
2398                goto out;
2399
2400        pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2401        for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2402             _pte++, _address += PAGE_SIZE) {
2403                pte_t pteval = *_pte;
2404                if (pte_none(pteval)) {
2405                        if (++none <= khugepaged_max_ptes_none)
2406                                continue;
2407                        else
2408                                goto out_unmap;
2409                }
2410                if (!pte_present(pteval) || !pte_write(pteval))
2411                        goto out_unmap;
2412                page = vm_normal_page(vma, _address, pteval);
2413                if (unlikely(!page))
2414                        goto out_unmap;
2415                /*
2416                 * Chose the node of the first page. This could
2417                 * be more sophisticated and look at more pages,
2418                 * but isn't for now.
2419                 */
2420                if (node == NUMA_NO_NODE)
2421                        node = page_to_nid(page);
2422                VM_BUG_ON(PageCompound(page));
2423                if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2424                        goto out_unmap;
2425                /* cannot use mapcount: can't collapse if there's a gup pin */
2426                if (page_count(page) != 1)
2427                        goto out_unmap;
2428                if (pte_young(pteval) || PageReferenced(page) ||
2429                    mmu_notifier_test_young(vma->vm_mm, address))
2430                        referenced = 1;
2431        }
2432        if (referenced)
2433                ret = 1;
2434out_unmap:
2435        pte_unmap_unlock(pte, ptl);
2436        if (ret)
2437                /* collapse_huge_page will return with the mmap_sem released */
2438                collapse_huge_page(mm, address, hpage, vma, node);
2439out:
2440        return ret;
2441}
2442
2443static void collect_mm_slot(struct mm_slot *mm_slot)
2444{
2445        struct mm_struct *mm = mm_slot->mm;
2446
2447        VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2448
2449        if (khugepaged_test_exit(mm)) {
2450                /* free mm_slot */
2451                hash_del(&mm_slot->hash);
2452                list_del(&mm_slot->mm_node);
2453
2454                /*
2455                 * Not strictly needed because the mm exited already.
2456                 *
2457                 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2458                 */
2459
2460                /* khugepaged_mm_lock actually not necessary for the below */
2461                free_mm_slot(mm_slot);
2462                mmdrop(mm);
2463        }
2464}
2465
2466static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2467                                            struct page **hpage)
2468        __releases(&khugepaged_mm_lock)
2469        __acquires(&khugepaged_mm_lock)
2470{
2471        struct mm_slot *mm_slot;
2472        struct mm_struct *mm;
2473        struct vm_area_struct *vma;
2474        int progress = 0;
2475
2476        VM_BUG_ON(!pages);
2477        VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2478
2479        if (khugepaged_scan.mm_slot)
2480                mm_slot = khugepaged_scan.mm_slot;
2481        else {
2482                mm_slot = list_entry(khugepaged_scan.mm_head.next,
2483                                     struct mm_slot, mm_node);
2484                khugepaged_scan.address = 0;
2485                khugepaged_scan.mm_slot = mm_slot;
2486        }
2487        spin_unlock(&khugepaged_mm_lock);
2488
2489        mm = mm_slot->mm;
2490        down_read(&mm->mmap_sem);
2491        if (unlikely(khugepaged_test_exit(mm)))
2492                vma = NULL;
2493        else
2494                vma = find_vma(mm, khugepaged_scan.address);
2495
2496        progress++;
2497        for (; vma; vma = vma->vm_next) {
2498                unsigned long hstart, hend;
2499
2500                cond_resched();
2501                if (unlikely(khugepaged_test_exit(mm))) {
2502                        progress++;
2503                        break;
2504                }
2505                if (!hugepage_vma_check(vma)) {
2506skip:
2507                        progress++;
2508                        continue;
2509                }
2510                hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2511                hend = vma->vm_end & HPAGE_PMD_MASK;
2512                if (hstart >= hend)
2513                        goto skip;
2514                if (khugepaged_scan.address > hend)
2515                        goto skip;
2516                if (khugepaged_scan.address < hstart)
2517                        khugepaged_scan.address = hstart;
2518                VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2519
2520                while (khugepaged_scan.address < hend) {
2521                        int ret;
2522                        cond_resched();
2523                        if (unlikely(khugepaged_test_exit(mm)))
2524                                goto breakouterloop;
2525
2526                        VM_BUG_ON(khugepaged_scan.address < hstart ||
2527                                  khugepaged_scan.address + HPAGE_PMD_SIZE >
2528                                  hend);
2529                        ret = khugepaged_scan_pmd(mm, vma,
2530                                                  khugepaged_scan.address,
2531                                                  hpage);
2532                        /* move to next address */
2533                        khugepaged_scan.address += HPAGE_PMD_SIZE;
2534                        progress += HPAGE_PMD_NR;
2535                        if (ret)
2536                                /* we released mmap_sem so break loop */
2537                                goto breakouterloop_mmap_sem;
2538                        if (progress >= pages)
2539                                goto breakouterloop;
2540                }
2541        }
2542breakouterloop:
2543        up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2544breakouterloop_mmap_sem:
2545
2546        spin_lock(&khugepaged_mm_lock);
2547        VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2548        /*
2549         * Release the current mm_slot if this mm is about to die, or
2550         * if we scanned all vmas of this mm.
2551         */
2552        if (khugepaged_test_exit(mm) || !vma) {
2553                /*
2554                 * Make sure that if mm_users is reaching zero while
2555                 * khugepaged runs here, khugepaged_exit will find
2556                 * mm_slot not pointing to the exiting mm.
2557                 */
2558                if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2559                        khugepaged_scan.mm_slot = list_entry(
2560                                mm_slot->mm_node.next,
2561                                struct mm_slot, mm_node);
2562                        khugepaged_scan.address = 0;
2563                } else {
2564                        khugepaged_scan.mm_slot = NULL;
2565                        khugepaged_full_scans++;
2566                }
2567
2568                collect_mm_slot(mm_slot);
2569        }
2570
2571        return progress;
2572}
2573
2574static int khugepaged_has_work(void)
2575{
2576        return !list_empty(&khugepaged_scan.mm_head) &&
2577                khugepaged_enabled();
2578}
2579
2580static int khugepaged_wait_event(void)
2581{
2582        return !list_empty(&khugepaged_scan.mm_head) ||
2583                kthread_should_stop();
2584}
2585
2586static void khugepaged_do_scan(void)
2587{
2588        struct page *hpage = NULL;
2589        unsigned int progress = 0, pass_through_head = 0;
2590        unsigned int pages = khugepaged_pages_to_scan;
2591        bool wait = true;
2592
2593        barrier(); /* write khugepaged_pages_to_scan to local stack */
2594
2595        while (progress < pages) {
2596                if (!khugepaged_prealloc_page(&hpage, &wait))
2597                        break;
2598
2599                cond_resched();
2600
2601                if (unlikely(kthread_should_stop() || freezing(current)))
2602                        break;
2603
2604                spin_lock(&khugepaged_mm_lock);
2605                if (!khugepaged_scan.mm_slot)
2606                        pass_through_head++;
2607                if (khugepaged_has_work() &&
2608                    pass_through_head < 2)
2609                        progress += khugepaged_scan_mm_slot(pages - progress,
2610                                                            &hpage);
2611                else
2612                        progress = pages;
2613                spin_unlock(&khugepaged_mm_lock);
2614        }
2615
2616        if (!IS_ERR_OR_NULL(hpage))
2617                put_page(hpage);
2618}
2619
2620static void khugepaged_wait_work(void)
2621{
2622        try_to_freeze();
2623
2624        if (khugepaged_has_work()) {
2625                if (!khugepaged_scan_sleep_millisecs)
2626                        return;
2627
2628                wait_event_freezable_timeout(khugepaged_wait,
2629                                             kthread_should_stop(),
2630                        msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2631                return;
2632        }
2633
2634        if (khugepaged_enabled())
2635                wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2636}
2637
2638static int khugepaged(void *none)
2639{
2640        struct mm_slot *mm_slot;
2641
2642        set_freezable();
2643        set_user_nice(current, 19);
2644
2645        while (!kthread_should_stop()) {
2646                khugepaged_do_scan();
2647                khugepaged_wait_work();
2648        }
2649
2650        spin_lock(&khugepaged_mm_lock);
2651        mm_slot = khugepaged_scan.mm_slot;
2652        khugepaged_scan.mm_slot = NULL;
2653        if (mm_slot)
2654                collect_mm_slot(mm_slot);
2655        spin_unlock(&khugepaged_mm_lock);
2656        return 0;
2657}
2658
2659static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2660                unsigned long haddr, pmd_t *pmd)
2661{
2662        struct mm_struct *mm = vma->vm_mm;
2663        pgtable_t pgtable;
2664        pmd_t _pmd;
2665        int i;
2666
2667        pmdp_clear_flush(vma, haddr, pmd);
2668        /* leave pmd empty until pte is filled */
2669
2670        pgtable = pgtable_trans_huge_withdraw(mm);
2671        pmd_populate(mm, &_pmd, pgtable);
2672
2673        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2674                pte_t *pte, entry;
2675                entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2676                entry = pte_mkspecial(entry);
2677                pte = pte_offset_map(&_pmd, haddr);
2678                VM_BUG_ON(!pte_none(*pte));
2679                set_pte_at(mm, haddr, pte, entry);
2680                pte_unmap(pte);
2681        }
2682        smp_wmb(); /* make pte visible before pmd */
2683        pmd_populate(mm, pmd, pgtable);
2684        put_huge_zero_page();
2685}
2686
2687void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2688                pmd_t *pmd)
2689{
2690        struct page *page;
2691        struct mm_struct *mm = vma->vm_mm;
2692        unsigned long haddr = address & HPAGE_PMD_MASK;
2693        unsigned long mmun_start;       /* For mmu_notifiers */
2694        unsigned long mmun_end;         /* For mmu_notifiers */
2695
2696        BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2697
2698        mmun_start = haddr;
2699        mmun_end   = haddr + HPAGE_PMD_SIZE;
2700        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2701        spin_lock(&mm->page_table_lock);
2702        if (unlikely(!pmd_trans_huge(*pmd))) {
2703                spin_unlock(&mm->page_table_lock);
2704                mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2705                return;
2706        }
2707        if (is_huge_zero_pmd(*pmd)) {
2708                __split_huge_zero_page_pmd(vma, haddr, pmd);
2709                spin_unlock(&mm->page_table_lock);
2710                mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2711                return;
2712        }
2713        page = pmd_page(*pmd);
2714        VM_BUG_ON(!page_count(page));
2715        get_page(page);
2716        spin_unlock(&mm->page_table_lock);
2717        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2718
2719        split_huge_page(page);
2720
2721        put_page(page);
2722        BUG_ON(pmd_trans_huge(*pmd));
2723}
2724
2725void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2726                pmd_t *pmd)
2727{
2728        struct vm_area_struct *vma;
2729
2730        vma = find_vma(mm, address);
2731        BUG_ON(vma == NULL);
2732        split_huge_page_pmd(vma, address, pmd);
2733}
2734
2735static void split_huge_page_address(struct mm_struct *mm,
2736                                    unsigned long address)
2737{
2738        pmd_t *pmd;
2739
2740        VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2741
2742        pmd = mm_find_pmd(mm, address);
2743        if (!pmd)
2744                return;
2745        /*
2746         * Caller holds the mmap_sem write mode, so a huge pmd cannot
2747         * materialize from under us.
2748         */
2749        split_huge_page_pmd_mm(mm, address, pmd);
2750}
2751
2752void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2753                             unsigned long start,
2754                             unsigned long end,
2755                             long adjust_next)
2756{
2757        /*
2758         * If the new start address isn't hpage aligned and it could
2759         * previously contain an hugepage: check if we need to split
2760         * an huge pmd.
2761         */
2762        if (start & ~HPAGE_PMD_MASK &&
2763            (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2764            (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2765                split_huge_page_address(vma->vm_mm, start);
2766
2767        /*
2768         * If the new end address isn't hpage aligned and it could
2769         * previously contain an hugepage: check if we need to split
2770         * an huge pmd.
2771         */
2772        if (end & ~HPAGE_PMD_MASK &&
2773            (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2774            (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2775                split_huge_page_address(vma->vm_mm, end);
2776
2777        /*
2778         * If we're also updating the vma->vm_next->vm_start, if the new
2779         * vm_next->vm_start isn't page aligned and it could previously
2780         * contain an hugepage: check if we need to split an huge pmd.
2781         */
2782        if (adjust_next > 0) {
2783                struct vm_area_struct *next = vma->vm_next;
2784                unsigned long nstart = next->vm_start;
2785                nstart += adjust_next << PAGE_SHIFT;
2786                if (nstart & ~HPAGE_PMD_MASK &&
2787                    (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2788                    (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2789                        split_huge_page_address(next->vm_mm, nstart);
2790        }
2791}
2792
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