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
  24#include <asm/tlb.h>
  25#include <asm/pgalloc.h>
  26#include "internal.h"
  27
  28/*
  29 * By default transparent hugepage support is enabled for all mappings
  30 * and khugepaged scans all mappings. Defrag is only invoked by
  31 * khugepaged hugepage allocations and by page faults inside
  32 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
  33 * allocations.
  34 */
  35unsigned long transparent_hugepage_flags __read_mostly =
  36#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  37        (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  38#endif
  39#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  40        (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  41#endif
  42        (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
  43        (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  44        (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  45
  46/* default scan 8*512 pte (or vmas) every 30 second */
  47static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
  48static unsigned int khugepaged_pages_collapsed;
  49static unsigned int khugepaged_full_scans;
  50static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  51/* during fragmentation poll the hugepage allocator once every minute */
  52static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  53static struct task_struct *khugepaged_thread __read_mostly;
  54static DEFINE_MUTEX(khugepaged_mutex);
  55static DEFINE_SPINLOCK(khugepaged_mm_lock);
  56static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  57/*
  58 * default collapse hugepages if there is at least one pte mapped like
  59 * it would have happened if the vma was large enough during page
  60 * fault.
  61 */
  62static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
  63
  64static int khugepaged(void *none);
  65static int mm_slots_hash_init(void);
  66static int khugepaged_slab_init(void);
  67static void khugepaged_slab_free(void);
  68
  69#define MM_SLOTS_HASH_HEADS 1024
  70static struct hlist_head *mm_slots_hash __read_mostly;
  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        extern int min_free_kbytes;
 109
 110        if (!khugepaged_enabled())
 111                return 0;
 112
 113        for_each_populated_zone(zone)
 114                nr_zones++;
 115
 116        /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
 117        recommended_min = pageblock_nr_pages * nr_zones * 2;
 118
 119        /*
 120         * Make sure that on average at least two pageblocks are almost free
 121         * of another type, one for a migratetype to fall back to and a
 122         * second to avoid subsequent fallbacks of other types There are 3
 123         * MIGRATE_TYPES we care about.
 124         */
 125        recommended_min += pageblock_nr_pages * nr_zones *
 126                           MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
 127
 128        /* don't ever allow to reserve more than 5% of the lowmem */
 129        recommended_min = min(recommended_min,
 130                              (unsigned long) nr_free_buffer_pages() / 20);
 131        recommended_min <<= (PAGE_SHIFT-10);
 132
 133        if (recommended_min > min_free_kbytes)
 134                min_free_kbytes = recommended_min;
 135        setup_per_zone_wmarks();
 136        return 0;
 137}
 138late_initcall(set_recommended_min_free_kbytes);
 139
 140static int start_khugepaged(void)
 141{
 142        int err = 0;
 143        if (khugepaged_enabled()) {
 144                if (!khugepaged_thread)
 145                        khugepaged_thread = kthread_run(khugepaged, NULL,
 146                                                        "khugepaged");
 147                if (unlikely(IS_ERR(khugepaged_thread))) {
 148                        printk(KERN_ERR
 149                               "khugepaged: kthread_run(khugepaged) failed\n");
 150                        err = PTR_ERR(khugepaged_thread);
 151                        khugepaged_thread = NULL;
 152                }
 153
 154                if (!list_empty(&khugepaged_scan.mm_head))
 155                        wake_up_interruptible(&khugepaged_wait);
 156
 157                set_recommended_min_free_kbytes();
 158        } else if (khugepaged_thread) {
 159                kthread_stop(khugepaged_thread);
 160                khugepaged_thread = NULL;
 161        }
 162
 163        return err;
 164}
 165
 166static atomic_t huge_zero_refcount;
 167static unsigned long huge_zero_pfn __read_mostly;
 168
 169static inline bool is_huge_zero_pfn(unsigned long pfn)
 170{
 171        unsigned long zero_pfn = ACCESS_ONCE(huge_zero_pfn);
 172        return zero_pfn && pfn == zero_pfn;
 173}
 174
 175static inline bool is_huge_zero_pmd(pmd_t pmd)
 176{
 177        return is_huge_zero_pfn(pmd_pfn(pmd));
 178}
 179
 180static unsigned long get_huge_zero_page(void)
 181{
 182        struct page *zero_page;
 183retry:
 184        if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 185                return ACCESS_ONCE(huge_zero_pfn);
 186
 187        zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 188                        HPAGE_PMD_ORDER);
 189        if (!zero_page) {
 190                count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 191                return 0;
 192        }
 193        count_vm_event(THP_ZERO_PAGE_ALLOC);
 194        preempt_disable();
 195        if (cmpxchg(&huge_zero_pfn, 0, page_to_pfn(zero_page))) {
 196                preempt_enable();
 197                __free_page(zero_page);
 198                goto retry;
 199        }
 200
 201        /* We take additional reference here. It will be put back by shrinker */
 202        atomic_set(&huge_zero_refcount, 2);
 203        preempt_enable();
 204        return ACCESS_ONCE(huge_zero_pfn);
 205}
 206
 207static void put_huge_zero_page(void)
 208{
 209        /*
 210         * Counter should never go to zero here. Only shrinker can put
 211         * last reference.
 212         */
 213        BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 214}
 215
 216static int shrink_huge_zero_page(struct shrinker *shrink,
 217                struct shrink_control *sc)
 218{
 219        if (!sc->nr_to_scan)
 220                /* we can free zero page only if last reference remains */
 221                return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 222
 223        if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 224                unsigned long zero_pfn = xchg(&huge_zero_pfn, 0);
 225                BUG_ON(zero_pfn == 0);
 226                __free_page(__pfn_to_page(zero_pfn));
 227        }
 228
 229        return 0;
 230}
 231
 232static struct shrinker huge_zero_page_shrinker = {
 233        .shrink = shrink_huge_zero_page,
 234        .seeks = DEFAULT_SEEKS,
 235};
 236
 237#ifdef CONFIG_SYSFS
 238
 239static ssize_t double_flag_show(struct kobject *kobj,
 240                                struct kobj_attribute *attr, char *buf,
 241                                enum transparent_hugepage_flag enabled,
 242                                enum transparent_hugepage_flag req_madv)
 243{
 244        if (test_bit(enabled, &transparent_hugepage_flags)) {
 245                VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
 246                return sprintf(buf, "[always] madvise never\n");
 247        } else if (test_bit(req_madv, &transparent_hugepage_flags))
 248                return sprintf(buf, "always [madvise] never\n");
 249        else
 250                return sprintf(buf, "always madvise [never]\n");
 251}
 252static ssize_t double_flag_store(struct kobject *kobj,
 253                                 struct kobj_attribute *attr,
 254                                 const char *buf, size_t count,
 255                                 enum transparent_hugepage_flag enabled,
 256                                 enum transparent_hugepage_flag req_madv)
 257{
 258        if (!memcmp("always", buf,
 259                    min(sizeof("always")-1, count))) {
 260                set_bit(enabled, &transparent_hugepage_flags);
 261                clear_bit(req_madv, &transparent_hugepage_flags);
 262        } else if (!memcmp("madvise", buf,
 263                           min(sizeof("madvise")-1, count))) {
 264                clear_bit(enabled, &transparent_hugepage_flags);
 265                set_bit(req_madv, &transparent_hugepage_flags);
 266        } else if (!memcmp("never", buf,
 267                           min(sizeof("never")-1, count))) {
 268                clear_bit(enabled, &transparent_hugepage_flags);
 269                clear_bit(req_madv, &transparent_hugepage_flags);
 270        } else
 271                return -EINVAL;
 272
 273        return count;
 274}
 275
 276static ssize_t enabled_show(struct kobject *kobj,
 277                            struct kobj_attribute *attr, char *buf)
 278{
 279        return double_flag_show(kobj, attr, buf,
 280                                TRANSPARENT_HUGEPAGE_FLAG,
 281                                TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 282}
 283static ssize_t enabled_store(struct kobject *kobj,
 284                             struct kobj_attribute *attr,
 285                             const char *buf, size_t count)
 286{
 287        ssize_t ret;
 288
 289        ret = double_flag_store(kobj, attr, buf, count,
 290                                TRANSPARENT_HUGEPAGE_FLAG,
 291                                TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 292
 293        if (ret > 0) {
 294                int err;
 295
 296                mutex_lock(&khugepaged_mutex);
 297                err = start_khugepaged();
 298                mutex_unlock(&khugepaged_mutex);
 299
 300                if (err)
 301                        ret = err;
 302        }
 303
 304        return ret;
 305}
 306static struct kobj_attribute enabled_attr =
 307        __ATTR(enabled, 0644, enabled_show, enabled_store);
 308
 309static ssize_t single_flag_show(struct kobject *kobj,
 310                                struct kobj_attribute *attr, char *buf,
 311                                enum transparent_hugepage_flag flag)
 312{
 313        return sprintf(buf, "%d\n",
 314                       !!test_bit(flag, &transparent_hugepage_flags));
 315}
 316
 317static ssize_t single_flag_store(struct kobject *kobj,
 318                                 struct kobj_attribute *attr,
 319                                 const char *buf, size_t count,
 320                                 enum transparent_hugepage_flag flag)
 321{
 322        unsigned long value;
 323        int ret;
 324
 325        ret = kstrtoul(buf, 10, &value);
 326        if (ret < 0)
 327                return ret;
 328        if (value > 1)
 329                return -EINVAL;
 330
 331        if (value)
 332                set_bit(flag, &transparent_hugepage_flags);
 333        else
 334                clear_bit(flag, &transparent_hugepage_flags);
 335
 336        return count;
 337}
 338
 339/*
 340 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 341 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 342 * memory just to allocate one more hugepage.
 343 */
 344static ssize_t defrag_show(struct kobject *kobj,
 345                           struct kobj_attribute *attr, char *buf)
 346{
 347        return double_flag_show(kobj, attr, buf,
 348                                TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 349                                TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 350}
 351static ssize_t defrag_store(struct kobject *kobj,
 352                            struct kobj_attribute *attr,
 353                            const char *buf, size_t count)
 354{
 355        return double_flag_store(kobj, attr, buf, count,
 356                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 357                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 358}
 359static struct kobj_attribute defrag_attr =
 360        __ATTR(defrag, 0644, defrag_show, defrag_store);
 361
 362static ssize_t use_zero_page_show(struct kobject *kobj,
 363                struct kobj_attribute *attr, char *buf)
 364{
 365        return single_flag_show(kobj, attr, buf,
 366                                TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 367}
 368static ssize_t use_zero_page_store(struct kobject *kobj,
 369                struct kobj_attribute *attr, const char *buf, size_t count)
 370{
 371        return single_flag_store(kobj, attr, buf, count,
 372                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 373}
 374static struct kobj_attribute use_zero_page_attr =
 375        __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 376#ifdef CONFIG_DEBUG_VM
 377static ssize_t debug_cow_show(struct kobject *kobj,
 378                                struct kobj_attribute *attr, char *buf)
 379{
 380        return single_flag_show(kobj, attr, buf,
 381                                TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 382}
 383static ssize_t debug_cow_store(struct kobject *kobj,
 384                               struct kobj_attribute *attr,
 385                               const char *buf, size_t count)
 386{
 387        return single_flag_store(kobj, attr, buf, count,
 388                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 389}
 390static struct kobj_attribute debug_cow_attr =
 391        __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 392#endif /* CONFIG_DEBUG_VM */
 393
 394static struct attribute *hugepage_attr[] = {
 395        &enabled_attr.attr,
 396        &defrag_attr.attr,
 397        &use_zero_page_attr.attr,
 398#ifdef CONFIG_DEBUG_VM
 399        &debug_cow_attr.attr,
 400#endif
 401        NULL,
 402};
 403
 404static struct attribute_group hugepage_attr_group = {
 405        .attrs = hugepage_attr,
 406};
 407
 408static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 409                                         struct kobj_attribute *attr,
 410                                         char *buf)
 411{
 412        return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 413}
 414
 415static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 416                                          struct kobj_attribute *attr,
 417                                          const char *buf, size_t count)
 418{
 419        unsigned long msecs;
 420        int err;
 421
 422        err = strict_strtoul(buf, 10, &msecs);
 423        if (err || msecs > UINT_MAX)
 424                return -EINVAL;
 425
 426        khugepaged_scan_sleep_millisecs = msecs;
 427        wake_up_interruptible(&khugepaged_wait);
 428
 429        return count;
 430}
 431static struct kobj_attribute scan_sleep_millisecs_attr =
 432        __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 433               scan_sleep_millisecs_store);
 434
 435static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 436                                          struct kobj_attribute *attr,
 437                                          char *buf)
 438{
 439        return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 440}
 441
 442static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 443                                           struct kobj_attribute *attr,
 444                                           const char *buf, size_t count)
 445{
 446        unsigned long msecs;
 447        int err;
 448
 449        err = strict_strtoul(buf, 10, &msecs);
 450        if (err || msecs > UINT_MAX)
 451                return -EINVAL;
 452
 453        khugepaged_alloc_sleep_millisecs = msecs;
 454        wake_up_interruptible(&khugepaged_wait);
 455
 456        return count;
 457}
 458static struct kobj_attribute alloc_sleep_millisecs_attr =
 459        __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 460               alloc_sleep_millisecs_store);
 461
 462static ssize_t pages_to_scan_show(struct kobject *kobj,
 463                                  struct kobj_attribute *attr,
 464                                  char *buf)
 465{
 466        return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 467}
 468static ssize_t pages_to_scan_store(struct kobject *kobj,
 469                                   struct kobj_attribute *attr,
 470                                   const char *buf, size_t count)
 471{
 472        int err;
 473        unsigned long pages;
 474
 475        err = strict_strtoul(buf, 10, &pages);
 476        if (err || !pages || pages > UINT_MAX)
 477                return -EINVAL;
 478
 479        khugepaged_pages_to_scan = pages;
 480
 481        return count;
 482}
 483static struct kobj_attribute pages_to_scan_attr =
 484        __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 485               pages_to_scan_store);
 486
 487static ssize_t pages_collapsed_show(struct kobject *kobj,
 488                                    struct kobj_attribute *attr,
 489                                    char *buf)
 490{
 491        return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 492}
 493static struct kobj_attribute pages_collapsed_attr =
 494        __ATTR_RO(pages_collapsed);
 495
 496static ssize_t full_scans_show(struct kobject *kobj,
 497                               struct kobj_attribute *attr,
 498                               char *buf)
 499{
 500        return sprintf(buf, "%u\n", khugepaged_full_scans);
 501}
 502static struct kobj_attribute full_scans_attr =
 503        __ATTR_RO(full_scans);
 504
 505static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 506                                      struct kobj_attribute *attr, char *buf)
 507{
 508        return single_flag_show(kobj, attr, buf,
 509                                TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 510}
 511static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 512                                       struct kobj_attribute *attr,
 513                                       const char *buf, size_t count)
 514{
 515        return single_flag_store(kobj, attr, buf, count,
 516                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 517}
 518static struct kobj_attribute khugepaged_defrag_attr =
 519        __ATTR(defrag, 0644, khugepaged_defrag_show,
 520               khugepaged_defrag_store);
 521
 522/*
 523 * max_ptes_none controls if khugepaged should collapse hugepages over
 524 * any unmapped ptes in turn potentially increasing the memory
 525 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 526 * reduce the available free memory in the system as it
 527 * runs. Increasing max_ptes_none will instead potentially reduce the
 528 * free memory in the system during the khugepaged scan.
 529 */
 530static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 531                                             struct kobj_attribute *attr,
 532                                             char *buf)
 533{
 534        return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 535}
 536static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 537                                              struct kobj_attribute *attr,
 538                                              const char *buf, size_t count)
 539{
 540        int err;
 541        unsigned long max_ptes_none;
 542
 543        err = strict_strtoul(buf, 10, &max_ptes_none);
 544        if (err || max_ptes_none > HPAGE_PMD_NR-1)
 545                return -EINVAL;
 546
 547        khugepaged_max_ptes_none = max_ptes_none;
 548
 549        return count;
 550}
 551static struct kobj_attribute khugepaged_max_ptes_none_attr =
 552        __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 553               khugepaged_max_ptes_none_store);
 554
 555static struct attribute *khugepaged_attr[] = {
 556        &khugepaged_defrag_attr.attr,
 557        &khugepaged_max_ptes_none_attr.attr,
 558        &pages_to_scan_attr.attr,
 559        &pages_collapsed_attr.attr,
 560        &full_scans_attr.attr,
 561        &scan_sleep_millisecs_attr.attr,
 562        &alloc_sleep_millisecs_attr.attr,
 563        NULL,
 564};
 565
 566static struct attribute_group khugepaged_attr_group = {
 567        .attrs = khugepaged_attr,
 568        .name = "khugepaged",
 569};
 570
 571static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 572{
 573        int err;
 574
 575        *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 576        if (unlikely(!*hugepage_kobj)) {
 577                printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n");
 578                return -ENOMEM;
 579        }
 580
 581        err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 582        if (err) {
 583                printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
 584                goto delete_obj;
 585        }
 586
 587        err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 588        if (err) {
 589                printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
 590                goto remove_hp_group;
 591        }
 592
 593        return 0;
 594
 595remove_hp_group:
 596        sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 597delete_obj:
 598        kobject_put(*hugepage_kobj);
 599        return err;
 600}
 601
 602static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 603{
 604        sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 605        sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 606        kobject_put(hugepage_kobj);
 607}
 608#else
 609static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 610{
 611        return 0;
 612}
 613
 614static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 615{
 616}
 617#endif /* CONFIG_SYSFS */
 618
 619static int __init hugepage_init(void)
 620{
 621        int err;
 622        struct kobject *hugepage_kobj;
 623
 624        if (!has_transparent_hugepage()) {
 625                transparent_hugepage_flags = 0;
 626                return -EINVAL;
 627        }
 628
 629        err = hugepage_init_sysfs(&hugepage_kobj);
 630        if (err)
 631                return err;
 632
 633        err = khugepaged_slab_init();
 634        if (err)
 635                goto out;
 636
 637        err = mm_slots_hash_init();
 638        if (err) {
 639                khugepaged_slab_free();
 640                goto out;
 641        }
 642
 643        register_shrinker(&huge_zero_page_shrinker);
 644
 645        /*
 646         * By default disable transparent hugepages on smaller systems,
 647         * where the extra memory used could hurt more than TLB overhead
 648         * is likely to save.  The admin can still enable it through /sys.
 649         */
 650        if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
 651                transparent_hugepage_flags = 0;
 652
 653        start_khugepaged();
 654
 655        return 0;
 656out:
 657        hugepage_exit_sysfs(hugepage_kobj);
 658        return err;
 659}
 660module_init(hugepage_init)
 661
 662static int __init setup_transparent_hugepage(char *str)
 663{
 664        int ret = 0;
 665        if (!str)
 666                goto out;
 667        if (!strcmp(str, "always")) {
 668                set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 669                        &transparent_hugepage_flags);
 670                clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 671                          &transparent_hugepage_flags);
 672                ret = 1;
 673        } else if (!strcmp(str, "madvise")) {
 674                clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 675                          &transparent_hugepage_flags);
 676                set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 677                        &transparent_hugepage_flags);
 678                ret = 1;
 679        } else if (!strcmp(str, "never")) {
 680                clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 681                          &transparent_hugepage_flags);
 682                clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 683                          &transparent_hugepage_flags);
 684                ret = 1;
 685        }
 686out:
 687        if (!ret)
 688                printk(KERN_WARNING
 689                       "transparent_hugepage= cannot parse, ignored\n");
 690        return ret;
 691}
 692__setup("transparent_hugepage=", setup_transparent_hugepage);
 693
 694pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 695{
 696        if (likely(vma->vm_flags & VM_WRITE))
 697                pmd = pmd_mkwrite(pmd);
 698        return pmd;
 699}
 700
 701static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma)
 702{
 703        pmd_t entry;
 704        entry = mk_pmd(page, vma->vm_page_prot);
 705        entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 706        entry = pmd_mkhuge(entry);
 707        return entry;
 708}
 709
 710static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 711                                        struct vm_area_struct *vma,
 712                                        unsigned long haddr, pmd_t *pmd,
 713                                        struct page *page)
 714{
 715        pgtable_t pgtable;
 716
 717        VM_BUG_ON(!PageCompound(page));
 718        pgtable = pte_alloc_one(mm, haddr);
 719        if (unlikely(!pgtable))
 720                return VM_FAULT_OOM;
 721
 722        clear_huge_page(page, haddr, HPAGE_PMD_NR);
 723        __SetPageUptodate(page);
 724
 725        spin_lock(&mm->page_table_lock);
 726        if (unlikely(!pmd_none(*pmd))) {
 727                spin_unlock(&mm->page_table_lock);
 728                mem_cgroup_uncharge_page(page);
 729                put_page(page);
 730                pte_free(mm, pgtable);
 731        } else {
 732                pmd_t entry;
 733                entry = mk_huge_pmd(page, vma);
 734                /*
 735                 * The spinlocking to take the lru_lock inside
 736                 * page_add_new_anon_rmap() acts as a full memory
 737                 * barrier to be sure clear_huge_page writes become
 738                 * visible after the set_pmd_at() write.
 739                 */
 740                page_add_new_anon_rmap(page, vma, haddr);
 741                set_pmd_at(mm, haddr, pmd, entry);
 742                pgtable_trans_huge_deposit(mm, pgtable);
 743                add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 744                mm->nr_ptes++;
 745                spin_unlock(&mm->page_table_lock);
 746        }
 747
 748        return 0;
 749}
 750
 751static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 752{
 753        return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
 754}
 755
 756static inline struct page *alloc_hugepage_vma(int defrag,
 757                                              struct vm_area_struct *vma,
 758                                              unsigned long haddr, int nd,
 759                                              gfp_t extra_gfp)
 760{
 761        return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
 762                               HPAGE_PMD_ORDER, vma, haddr, nd);
 763}
 764
 765#ifndef CONFIG_NUMA
 766static inline struct page *alloc_hugepage(int defrag)
 767{
 768        return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
 769                           HPAGE_PMD_ORDER);
 770}
 771#endif
 772
 773static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 774                struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 775                unsigned long zero_pfn)
 776{
 777        pmd_t entry;
 778        if (!pmd_none(*pmd))
 779                return false;
 780        entry = pfn_pmd(zero_pfn, vma->vm_page_prot);
 781        entry = pmd_wrprotect(entry);
 782        entry = pmd_mkhuge(entry);
 783        set_pmd_at(mm, haddr, pmd, entry);
 784        pgtable_trans_huge_deposit(mm, pgtable);
 785        mm->nr_ptes++;
 786        return true;
 787}
 788
 789int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 790                               unsigned long address, pmd_t *pmd,
 791                               unsigned int flags)
 792{
 793        struct page *page;
 794        unsigned long haddr = address & HPAGE_PMD_MASK;
 795        pte_t *pte;
 796
 797        if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
 798                if (unlikely(anon_vma_prepare(vma)))
 799                        return VM_FAULT_OOM;
 800                if (unlikely(khugepaged_enter(vma)))
 801                        return VM_FAULT_OOM;
 802                if (!(flags & FAULT_FLAG_WRITE) &&
 803                                transparent_hugepage_use_zero_page()) {
 804                        pgtable_t pgtable;
 805                        unsigned long zero_pfn;
 806                        bool set;
 807                        pgtable = pte_alloc_one(mm, haddr);
 808                        if (unlikely(!pgtable))
 809                                return VM_FAULT_OOM;
 810                        zero_pfn = get_huge_zero_page();
 811                        if (unlikely(!zero_pfn)) {
 812                                pte_free(mm, pgtable);
 813                                count_vm_event(THP_FAULT_FALLBACK);
 814                                goto out;
 815                        }
 816                        spin_lock(&mm->page_table_lock);
 817                        set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
 818                                        zero_pfn);
 819                        spin_unlock(&mm->page_table_lock);
 820                        if (!set) {
 821                                pte_free(mm, pgtable);
 822                                put_huge_zero_page();
 823                        }
 824                        return 0;
 825                }
 826                page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
 827                                          vma, haddr, numa_node_id(), 0);
 828                if (unlikely(!page)) {
 829                        count_vm_event(THP_FAULT_FALLBACK);
 830                        goto out;
 831                }
 832                count_vm_event(THP_FAULT_ALLOC);
 833                if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
 834                        put_page(page);
 835                        goto out;
 836                }
 837                if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
 838                                                          page))) {
 839                        mem_cgroup_uncharge_page(page);
 840                        put_page(page);
 841                        goto out;
 842                }
 843
 844                return 0;
 845        }
 846out:
 847        /*
 848         * Use __pte_alloc instead of pte_alloc_map, because we can't
 849         * run pte_offset_map on the pmd, if an huge pmd could
 850         * materialize from under us from a different thread.
 851         */
 852        if (unlikely(pmd_none(*pmd)) &&
 853            unlikely(__pte_alloc(mm, vma, pmd, address)))
 854                return VM_FAULT_OOM;
 855        /* if an huge pmd materialized from under us just retry later */
 856        if (unlikely(pmd_trans_huge(*pmd)))
 857                return 0;
 858        /*
 859         * A regular pmd is established and it can't morph into a huge pmd
 860         * from under us anymore at this point because we hold the mmap_sem
 861         * read mode and khugepaged takes it in write mode. So now it's
 862         * safe to run pte_offset_map().
 863         */
 864        pte = pte_offset_map(pmd, address);
 865        return handle_pte_fault(mm, vma, address, pte, pmd, flags);
 866}
 867
 868int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 869                  pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 870                  struct vm_area_struct *vma)
 871{
 872        struct page *src_page;
 873        pmd_t pmd;
 874        pgtable_t pgtable;
 875        int ret;
 876
 877        ret = -ENOMEM;
 878        pgtable = pte_alloc_one(dst_mm, addr);
 879        if (unlikely(!pgtable))
 880                goto out;
 881
 882        spin_lock(&dst_mm->page_table_lock);
 883        spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
 884
 885        ret = -EAGAIN;
 886        pmd = *src_pmd;
 887        if (unlikely(!pmd_trans_huge(pmd))) {
 888                pte_free(dst_mm, pgtable);
 889                goto out_unlock;
 890        }
 891        /*
 892         * mm->page_table_lock is enough to be sure that huge zero pmd is not
 893         * under splitting since we don't split the page itself, only pmd to
 894         * a page table.
 895         */
 896        if (is_huge_zero_pmd(pmd)) {
 897                unsigned long zero_pfn;
 898                bool set;
 899                /*
 900                 * get_huge_zero_page() will never allocate a new page here,
 901                 * since we already have a zero page to copy. It just takes a
 902                 * reference.
 903                 */
 904                zero_pfn = get_huge_zero_page();
 905                set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 906                                zero_pfn);
 907                BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
 908                ret = 0;
 909                goto out_unlock;
 910        }
 911        if (unlikely(pmd_trans_splitting(pmd))) {
 912                /* split huge page running from under us */
 913                spin_unlock(&src_mm->page_table_lock);
 914                spin_unlock(&dst_mm->page_table_lock);
 915                pte_free(dst_mm, pgtable);
 916
 917                wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
 918                goto out;
 919        }
 920        src_page = pmd_page(pmd);
 921        VM_BUG_ON(!PageHead(src_page));
 922        get_page(src_page);
 923        page_dup_rmap(src_page);
 924        add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 925
 926        pmdp_set_wrprotect(src_mm, addr, src_pmd);
 927        pmd = pmd_mkold(pmd_wrprotect(pmd));
 928        set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 929        pgtable_trans_huge_deposit(dst_mm, pgtable);
 930        dst_mm->nr_ptes++;
 931
 932        ret = 0;
 933out_unlock:
 934        spin_unlock(&src_mm->page_table_lock);
 935        spin_unlock(&dst_mm->page_table_lock);
 936out:
 937        return ret;
 938}
 939
 940void huge_pmd_set_accessed(struct mm_struct *mm,
 941                           struct vm_area_struct *vma,
 942                           unsigned long address,
 943                           pmd_t *pmd, pmd_t orig_pmd,
 944                           int dirty)
 945{
 946        pmd_t entry;
 947        unsigned long haddr;
 948
 949        spin_lock(&mm->page_table_lock);
 950        if (unlikely(!pmd_same(*pmd, orig_pmd)))
 951                goto unlock;
 952
 953        entry = pmd_mkyoung(orig_pmd);
 954        haddr = address & HPAGE_PMD_MASK;
 955        if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
 956                update_mmu_cache_pmd(vma, address, pmd);
 957
 958unlock:
 959        spin_unlock(&mm->page_table_lock);
 960}
 961
 962static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
 963                struct vm_area_struct *vma, unsigned long address,
 964                pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
 965{
 966        pgtable_t pgtable;
 967        pmd_t _pmd;
 968        struct page *page;
 969        int i, ret = 0;
 970        unsigned long mmun_start;       /* For mmu_notifiers */
 971        unsigned long mmun_end;         /* For mmu_notifiers */
 972
 973        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
 974        if (!page) {
 975                ret |= VM_FAULT_OOM;
 976                goto out;
 977        }
 978
 979        if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
 980                put_page(page);
 981                ret |= VM_FAULT_OOM;
 982                goto out;
 983        }
 984
 985        clear_user_highpage(page, address);
 986        __SetPageUptodate(page);
 987
 988        mmun_start = haddr;
 989        mmun_end   = haddr + HPAGE_PMD_SIZE;
 990        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 991
 992        spin_lock(&mm->page_table_lock);
 993        if (unlikely(!pmd_same(*pmd, orig_pmd)))
 994                goto out_free_page;
 995
 996        pmdp_clear_flush(vma, haddr, pmd);
 997        /* leave pmd empty until pte is filled */
 998
 999        pgtable = pgtable_trans_huge_withdraw(mm);
1000        pmd_populate(mm, &_pmd, pgtable);
1001
1002        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1003                pte_t *pte, entry;
1004                if (haddr == (address & PAGE_MASK)) {
1005                        entry = mk_pte(page, vma->vm_page_prot);
1006                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1007                        page_add_new_anon_rmap(page, vma, haddr);
1008                } else {
1009                        entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1010                        entry = pte_mkspecial(entry);
1011                }
1012                pte = pte_offset_map(&_pmd, haddr);
1013                VM_BUG_ON(!pte_none(*pte));
1014                set_pte_at(mm, haddr, pte, entry);
1015                pte_unmap(pte);
1016        }
1017        smp_wmb(); /* make pte visible before pmd */
1018        pmd_populate(mm, pmd, pgtable);
1019        spin_unlock(&mm->page_table_lock);
1020        put_huge_zero_page();
1021        inc_mm_counter(mm, MM_ANONPAGES);
1022
1023        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1024
1025        ret |= VM_FAULT_WRITE;
1026out:
1027        return ret;
1028out_free_page:
1029        spin_unlock(&mm->page_table_lock);
1030        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1031        mem_cgroup_uncharge_page(page);
1032        put_page(page);
1033        goto out;
1034}
1035
1036static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1037                                        struct vm_area_struct *vma,
1038                                        unsigned long address,
1039                                        pmd_t *pmd, pmd_t orig_pmd,
1040                                        struct page *page,
1041                                        unsigned long haddr)
1042{
1043        pgtable_t pgtable;
1044        pmd_t _pmd;
1045        int ret = 0, i;
1046        struct page **pages;
1047        unsigned long mmun_start;       /* For mmu_notifiers */
1048        unsigned long mmun_end;         /* For mmu_notifiers */
1049
1050        pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1051                        GFP_KERNEL);
1052        if (unlikely(!pages)) {
1053                ret |= VM_FAULT_OOM;
1054                goto out;
1055        }
1056
1057        for (i = 0; i < HPAGE_PMD_NR; i++) {
1058                pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1059                                               __GFP_OTHER_NODE,
1060                                               vma, address, page_to_nid(page));
1061                if (unlikely(!pages[i] ||
1062                             mem_cgroup_newpage_charge(pages[i], mm,
1063                                                       GFP_KERNEL))) {
1064                        if (pages[i])
1065                                put_page(pages[i]);
1066                        mem_cgroup_uncharge_start();
1067                        while (--i >= 0) {
1068                                mem_cgroup_uncharge_page(pages[i]);
1069                                put_page(pages[i]);
1070                        }
1071                        mem_cgroup_uncharge_end();
1072                        kfree(pages);
1073                        ret |= VM_FAULT_OOM;
1074                        goto out;
1075                }
1076        }
1077
1078        for (i = 0; i < HPAGE_PMD_NR; i++) {
1079                copy_user_highpage(pages[i], page + i,
1080                                   haddr + PAGE_SIZE * i, vma);
1081                __SetPageUptodate(pages[i]);
1082                cond_resched();
1083        }
1084
1085        mmun_start = haddr;
1086        mmun_end   = haddr + HPAGE_PMD_SIZE;
1087        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1088
1089        spin_lock(&mm->page_table_lock);
1090        if (unlikely(!pmd_same(*pmd, orig_pmd)))
1091                goto out_free_pages;
1092        VM_BUG_ON(!PageHead(page));
1093
1094        pmdp_clear_flush(vma, haddr, pmd);
1095        /* leave pmd empty until pte is filled */
1096
1097        pgtable = pgtable_trans_huge_withdraw(mm);
1098        pmd_populate(mm, &_pmd, pgtable);
1099
1100        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1101                pte_t *pte, entry;
1102                entry = mk_pte(pages[i], vma->vm_page_prot);
1103                entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1104                page_add_new_anon_rmap(pages[i], vma, haddr);
1105                pte = pte_offset_map(&_pmd, haddr);
1106                VM_BUG_ON(!pte_none(*pte));
1107                set_pte_at(mm, haddr, pte, entry);
1108                pte_unmap(pte);
1109        }
1110        kfree(pages);
1111
1112        smp_wmb(); /* make pte visible before pmd */
1113        pmd_populate(mm, pmd, pgtable);
1114        page_remove_rmap(page);
1115        spin_unlock(&mm->page_table_lock);
1116
1117        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1118
1119        ret |= VM_FAULT_WRITE;
1120        put_page(page);
1121
1122out:
1123        return ret;
1124
1125out_free_pages:
1126        spin_unlock(&mm->page_table_lock);
1127        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1128        mem_cgroup_uncharge_start();
1129        for (i = 0; i < HPAGE_PMD_NR; i++) {
1130                mem_cgroup_uncharge_page(pages[i]);
1131                put_page(pages[i]);
1132        }
1133        mem_cgroup_uncharge_end();
1134        kfree(pages);
1135        goto out;
1136}
1137
1138int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1139                        unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1140{
1141        int ret = 0;
1142        struct page *page = NULL, *new_page;
1143        unsigned long haddr;
1144        unsigned long mmun_start;       /* For mmu_notifiers */
1145        unsigned long mmun_end;         /* For mmu_notifiers */
1146
1147        VM_BUG_ON(!vma->anon_vma);
1148        haddr = address & HPAGE_PMD_MASK;
1149        if (is_huge_zero_pmd(orig_pmd))
1150                goto alloc;
1151        spin_lock(&mm->page_table_lock);
1152        if (unlikely(!pmd_same(*pmd, orig_pmd)))
1153                goto out_unlock;
1154
1155        page = pmd_page(orig_pmd);
1156        VM_BUG_ON(!PageCompound(page) || !PageHead(page));
1157        if (page_mapcount(page) == 1) {
1158                pmd_t entry;
1159                entry = pmd_mkyoung(orig_pmd);
1160                entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1161                if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1162                        update_mmu_cache_pmd(vma, address, pmd);
1163                ret |= VM_FAULT_WRITE;
1164                goto out_unlock;
1165        }
1166        get_page(page);
1167        spin_unlock(&mm->page_table_lock);
1168alloc:
1169        if (transparent_hugepage_enabled(vma) &&
1170            !transparent_hugepage_debug_cow())
1171                new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1172                                              vma, haddr, numa_node_id(), 0);
1173        else
1174                new_page = NULL;
1175
1176        if (unlikely(!new_page)) {
1177                count_vm_event(THP_FAULT_FALLBACK);
1178                if (is_huge_zero_pmd(orig_pmd)) {
1179                        ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1180                                        address, pmd, orig_pmd, haddr);
1181                } else {
1182                        ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1183                                        pmd, orig_pmd, page, haddr);
1184                        if (ret & VM_FAULT_OOM)
1185                                split_huge_page(page);
1186                        put_page(page);
1187                }
1188                goto out;
1189        }
1190        count_vm_event(THP_FAULT_ALLOC);
1191
1192        if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1193                put_page(new_page);
1194                if (page) {
1195                        split_huge_page(page);
1196                        put_page(page);
1197                }
1198                ret |= VM_FAULT_OOM;
1199                goto out;
1200        }
1201
1202        if (is_huge_zero_pmd(orig_pmd))
1203                clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1204        else
1205                copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1206        __SetPageUptodate(new_page);
1207
1208        mmun_start = haddr;
1209        mmun_end   = haddr + HPAGE_PMD_SIZE;
1210        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1211
1212        spin_lock(&mm->page_table_lock);
1213        if (page)
1214                put_page(page);
1215        if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1216                spin_unlock(&mm->page_table_lock);
1217                mem_cgroup_uncharge_page(new_page);
1218                put_page(new_page);
1219                goto out_mn;
1220        } else {
1221                pmd_t entry;
1222                entry = mk_huge_pmd(new_page, vma);
1223                pmdp_clear_flush(vma, haddr, pmd);
1224                page_add_new_anon_rmap(new_page, vma, haddr);
1225                set_pmd_at(mm, haddr, pmd, entry);
1226                update_mmu_cache_pmd(vma, address, pmd);
1227                if (is_huge_zero_pmd(orig_pmd)) {
1228                        add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1229                        put_huge_zero_page();
1230                } else {
1231                        VM_BUG_ON(!PageHead(page));
1232                        page_remove_rmap(page);
1233                        put_page(page);
1234                }
1235                ret |= VM_FAULT_WRITE;
1236        }
1237        spin_unlock(&mm->page_table_lock);
1238out_mn:
1239        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1240out:
1241        return ret;
1242out_unlock:
1243        spin_unlock(&mm->page_table_lock);
1244        return ret;
1245}
1246
1247struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1248                                   unsigned long addr,
1249                                   pmd_t *pmd,
1250                                   unsigned int flags)
1251{
1252        struct mm_struct *mm = vma->vm_mm;
1253        struct page *page = NULL;
1254
1255        assert_spin_locked(&mm->page_table_lock);
1256
1257        if (flags & FOLL_WRITE && !pmd_write(*pmd))
1258                goto out;
1259
1260        /* Avoid dumping huge zero page */
1261        if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1262                return ERR_PTR(-EFAULT);
1263
1264        page = pmd_page(*pmd);
1265        VM_BUG_ON(!PageHead(page));
1266        if (flags & FOLL_TOUCH) {
1267                pmd_t _pmd;
1268                /*
1269                 * We should set the dirty bit only for FOLL_WRITE but
1270                 * for now the dirty bit in the pmd is meaningless.
1271                 * And if the dirty bit will become meaningful and
1272                 * we'll only set it with FOLL_WRITE, an atomic
1273                 * set_bit will be required on the pmd to set the
1274                 * young bit, instead of the current set_pmd_at.
1275                 */
1276                _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1277                set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1278        }
1279        if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1280                if (page->mapping && trylock_page(page)) {
1281                        lru_add_drain();
1282                        if (page->mapping)
1283                                mlock_vma_page(page);
1284                        unlock_page(page);
1285                }
1286        }
1287        page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1288        VM_BUG_ON(!PageCompound(page));
1289        if (flags & FOLL_GET)
1290                get_page_foll(page);
1291
1292out:
1293        return page;
1294}
1295
1296/* NUMA hinting page fault entry point for trans huge pmds */
1297int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1298                                unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1299{
1300        struct page *page;
1301        unsigned long haddr = addr & HPAGE_PMD_MASK;
1302        int target_nid;
1303        int current_nid = -1;
1304        bool migrated;
1305        bool page_locked = false;
1306
1307        spin_lock(&mm->page_table_lock);
1308        if (unlikely(!pmd_same(pmd, *pmdp)))
1309                goto out_unlock;
1310
1311        page = pmd_page(pmd);
1312        get_page(page);
1313        current_nid = page_to_nid(page);
1314        count_vm_numa_event(NUMA_HINT_FAULTS);
1315        if (current_nid == numa_node_id())
1316                count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1317
1318        target_nid = mpol_misplaced(page, vma, haddr);
1319        if (target_nid == -1) {
1320                put_page(page);
1321                goto clear_pmdnuma;
1322        }
1323
1324        /* Acquire the page lock to serialise THP migrations */
1325        spin_unlock(&mm->page_table_lock);
1326        lock_page(page);
1327        page_locked = true;
1328
1329        /* Confirm the PTE did not while locked */
1330        spin_lock(&mm->page_table_lock);
1331        if (unlikely(!pmd_same(pmd, *pmdp))) {
1332                unlock_page(page);
1333                put_page(page);
1334                goto out_unlock;
1335        }
1336        spin_unlock(&mm->page_table_lock);
1337
1338        /* Migrate the THP to the requested node */
1339        migrated = migrate_misplaced_transhuge_page(mm, vma,
1340                                pmdp, pmd, addr,
1341                                page, target_nid);
1342        if (migrated)
1343                current_nid = target_nid;
1344        else {
1345                spin_lock(&mm->page_table_lock);
1346                if (unlikely(!pmd_same(pmd, *pmdp))) {
1347                        unlock_page(page);
1348                        goto out_unlock;
1349                }
1350                goto clear_pmdnuma;
1351        }
1352
1353        task_numa_fault(current_nid, HPAGE_PMD_NR, migrated);
1354        return 0;
1355
1356clear_pmdnuma:
1357        pmd = pmd_mknonnuma(pmd);
1358        set_pmd_at(mm, haddr, pmdp, pmd);
1359        VM_BUG_ON(pmd_numa(*pmdp));
1360        update_mmu_cache_pmd(vma, addr, pmdp);
1361        if (page_locked)
1362                unlock_page(page);
1363
1364out_unlock:
1365        spin_unlock(&mm->page_table_lock);
1366        if (current_nid != -1)
1367                task_numa_fault(current_nid, HPAGE_PMD_NR, migrated);
1368        return 0;
1369}
1370
1371int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1372                 pmd_t *pmd, unsigned long addr)
1373{
1374        int ret = 0;
1375
1376        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1377                struct page *page;
1378                pgtable_t pgtable;
1379                pmd_t orig_pmd;
1380                pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1381                orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1382                tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1383                if (is_huge_zero_pmd(orig_pmd)) {
1384                        tlb->mm->nr_ptes--;
1385                        spin_unlock(&tlb->mm->page_table_lock);
1386                        put_huge_zero_page();
1387                } else {
1388                        page = pmd_page(orig_pmd);
1389                        page_remove_rmap(page);
1390                        VM_BUG_ON(page_mapcount(page) < 0);
1391                        add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1392                        VM_BUG_ON(!PageHead(page));
1393                        tlb->mm->nr_ptes--;
1394                        spin_unlock(&tlb->mm->page_table_lock);
1395                        tlb_remove_page(tlb, page);
1396                }
1397                pte_free(tlb->mm, pgtable);
1398                ret = 1;
1399        }
1400        return ret;
1401}
1402
1403int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1404                unsigned long addr, unsigned long end,
1405                unsigned char *vec)
1406{
1407        int ret = 0;
1408
1409        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1410                /*
1411                 * All logical pages in the range are present
1412                 * if backed by a huge page.
1413                 */
1414                spin_unlock(&vma->vm_mm->page_table_lock);
1415                memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1416                ret = 1;
1417        }
1418
1419        return ret;
1420}
1421
1422int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1423                  unsigned long old_addr,
1424                  unsigned long new_addr, unsigned long old_end,
1425                  pmd_t *old_pmd, pmd_t *new_pmd)
1426{
1427        int ret = 0;
1428        pmd_t pmd;
1429
1430        struct mm_struct *mm = vma->vm_mm;
1431
1432        if ((old_addr & ~HPAGE_PMD_MASK) ||
1433            (new_addr & ~HPAGE_PMD_MASK) ||
1434            old_end - old_addr < HPAGE_PMD_SIZE ||
1435            (new_vma->vm_flags & VM_NOHUGEPAGE))
1436                goto out;
1437
1438        /*
1439         * The destination pmd shouldn't be established, free_pgtables()
1440         * should have release it.
1441         */
1442        if (WARN_ON(!pmd_none(*new_pmd))) {
1443                VM_BUG_ON(pmd_trans_huge(*new_pmd));
1444                goto out;
1445        }
1446
1447        ret = __pmd_trans_huge_lock(old_pmd, vma);
1448        if (ret == 1) {
1449                pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1450                VM_BUG_ON(!pmd_none(*new_pmd));
1451                set_pmd_at(mm, new_addr, new_pmd, pmd);
1452                spin_unlock(&mm->page_table_lock);
1453        }
1454out:
1455        return ret;
1456}
1457
1458int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1459                unsigned long addr, pgprot_t newprot, int prot_numa)
1460{
1461        struct mm_struct *mm = vma->vm_mm;
1462        int ret = 0;
1463
1464        if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1465                pmd_t entry;
1466                entry = pmdp_get_and_clear(mm, addr, pmd);
1467                if (!prot_numa) {
1468                        entry = pmd_modify(entry, newprot);
1469                        BUG_ON(pmd_write(entry));
1470                } else {
1471                        struct page *page = pmd_page(*pmd);
1472
1473                        /* only check non-shared pages */
1474                        if (page_mapcount(page) == 1 &&
1475                            !pmd_numa(*pmd)) {
1476                                entry = pmd_mknuma(entry);
1477                        }
1478                }
1479                set_pmd_at(mm, addr, pmd, entry);
1480                spin_unlock(&vma->vm_mm->page_table_lock);
1481                ret = 1;
1482        }
1483
1484        return ret;
1485}
1486
1487/*
1488 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1489 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1490 *
1491 * Note that if it returns 1, this routine returns without unlocking page
1492 * table locks. So callers must unlock them.
1493 */
1494int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1495{
1496        spin_lock(&vma->vm_mm->page_table_lock);
1497        if (likely(pmd_trans_huge(*pmd))) {
1498                if (unlikely(pmd_trans_splitting(*pmd))) {
1499                        spin_unlock(&vma->vm_mm->page_table_lock);
1500                        wait_split_huge_page(vma->anon_vma, pmd);
1501                        return -1;
1502                } else {
1503                        /* Thp mapped by 'pmd' is stable, so we can
1504                         * handle it as it is. */
1505                        return 1;
1506                }
1507        }
1508        spin_unlock(&vma->vm_mm->page_table_lock);
1509        return 0;
1510}
1511
1512pmd_t *page_check_address_pmd(struct page *page,
1513                              struct mm_struct *mm,
1514                              unsigned long address,
1515                              enum page_check_address_pmd_flag flag)
1516{
1517        pmd_t *pmd, *ret = NULL;
1518
1519        if (address & ~HPAGE_PMD_MASK)
1520                goto out;
1521
1522        pmd = mm_find_pmd(mm, address);
1523        if (!pmd)
1524                goto out;
1525        if (pmd_none(*pmd))
1526                goto out;
1527        if (pmd_page(*pmd) != page)
1528                goto out;
1529        /*
1530         * split_vma() may create temporary aliased mappings. There is
1531         * no risk as long as all huge pmd are found and have their
1532         * splitting bit set before __split_huge_page_refcount
1533         * runs. Finding the same huge pmd more than once during the
1534         * same rmap walk is not a problem.
1535         */
1536        if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1537            pmd_trans_splitting(*pmd))
1538                goto out;
1539        if (pmd_trans_huge(*pmd)) {
1540                VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1541                          !pmd_trans_splitting(*pmd));
1542                ret = pmd;
1543        }
1544out:
1545        return ret;
1546}
1547
1548static int __split_huge_page_splitting(struct page *page,
1549                                       struct vm_area_struct *vma,
1550                                       unsigned long address)
1551{
1552        struct mm_struct *mm = vma->vm_mm;
1553        pmd_t *pmd;
1554        int ret = 0;
1555        /* For mmu_notifiers */
1556        const unsigned long mmun_start = address;
1557        const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1558
1559        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1560        spin_lock(&mm->page_table_lock);
1561        pmd = page_check_address_pmd(page, mm, address,
1562                                     PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1563        if (pmd) {
1564                /*
1565                 * We can't temporarily set the pmd to null in order
1566                 * to split it, the pmd must remain marked huge at all
1567                 * times or the VM won't take the pmd_trans_huge paths
1568                 * and it won't wait on the anon_vma->root->rwsem to
1569                 * serialize against split_huge_page*.
1570                 */
1571                pmdp_splitting_flush(vma, address, pmd);
1572                ret = 1;
1573        }
1574        spin_unlock(&mm->page_table_lock);
1575        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1576
1577        return ret;
1578}
1579
1580static void __split_huge_page_refcount(struct page *page)
1581{
1582        int i;
1583        struct zone *zone = page_zone(page);
1584        struct lruvec *lruvec;
1585        int tail_count = 0;
1586
1587        /* prevent PageLRU to go away from under us, and freeze lru stats */
1588        spin_lock_irq(&zone->lru_lock);
1589        lruvec = mem_cgroup_page_lruvec(page, zone);
1590
1591        compound_lock(page);
1592        /* complete memcg works before add pages to LRU */
1593        mem_cgroup_split_huge_fixup(page);
1594
1595        for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1596                struct page *page_tail = page + i;
1597
1598                /* tail_page->_mapcount cannot change */
1599                BUG_ON(page_mapcount(page_tail) < 0);
1600                tail_count += page_mapcount(page_tail);
1601                /* check for overflow */
1602                BUG_ON(tail_count < 0);
1603                BUG_ON(atomic_read(&page_tail->_count) != 0);
1604                /*
1605                 * tail_page->_count is zero and not changing from
1606                 * under us. But get_page_unless_zero() may be running
1607                 * from under us on the tail_page. If we used
1608                 * atomic_set() below instead of atomic_add(), we
1609                 * would then run atomic_set() concurrently with
1610                 * get_page_unless_zero(), and atomic_set() is
1611                 * implemented in C not using locked ops. spin_unlock
1612                 * on x86 sometime uses locked ops because of PPro
1613                 * errata 66, 92, so unless somebody can guarantee
1614                 * atomic_set() here would be safe on all archs (and
1615                 * not only on x86), it's safer to use atomic_add().
1616                 */
1617                atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1618                           &page_tail->_count);
1619
1620                /* after clearing PageTail the gup refcount can be released */
1621                smp_mb();
1622
1623                /*
1624                 * retain hwpoison flag of the poisoned tail page:
1625                 *   fix for the unsuitable process killed on Guest Machine(KVM)
1626                 *   by the memory-failure.
1627                 */
1628                page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1629                page_tail->flags |= (page->flags &
1630                                     ((1L << PG_referenced) |
1631                                      (1L << PG_swapbacked) |
1632                                      (1L << PG_mlocked) |
1633                                      (1L << PG_uptodate)));
1634                page_tail->flags |= (1L << PG_dirty);
1635
1636                /* clear PageTail before overwriting first_page */
1637                smp_wmb();
1638
1639                /*
1640                 * __split_huge_page_splitting() already set the
1641                 * splitting bit in all pmd that could map this
1642                 * hugepage, that will ensure no CPU can alter the
1643                 * mapcount on the head page. The mapcount is only
1644                 * accounted in the head page and it has to be
1645                 * transferred to all tail pages in the below code. So
1646                 * for this code to be safe, the split the mapcount
1647                 * can't change. But that doesn't mean userland can't
1648                 * keep changing and reading the page contents while
1649                 * we transfer the mapcount, so the pmd splitting
1650                 * status is achieved setting a reserved bit in the
1651                 * pmd, not by clearing the present bit.
1652                */
1653                page_tail->_mapcount = page->_mapcount;
1654
1655                BUG_ON(page_tail->mapping);
1656                page_tail->mapping = page->mapping;
1657
1658                page_tail->index = page->index + i;
1659                page_xchg_last_nid(page_tail, page_last_nid(page));
1660
1661                BUG_ON(!PageAnon(page_tail));
1662                BUG_ON(!PageUptodate(page_tail));
1663                BUG_ON(!PageDirty(page_tail));
1664                BUG_ON(!PageSwapBacked(page_tail));
1665
1666                lru_add_page_tail(page, page_tail, lruvec);
1667        }
1668        atomic_sub(tail_count, &page->_count);
1669        BUG_ON(atomic_read(&page->_count) <= 0);
1670
1671        __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1672        __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1673
1674        ClearPageCompound(page);
1675        compound_unlock(page);
1676        spin_unlock_irq(&zone->lru_lock);
1677
1678        for (i = 1; i < HPAGE_PMD_NR; i++) {
1679                struct page *page_tail = page + i;
1680                BUG_ON(page_count(page_tail) <= 0);
1681                /*
1682                 * Tail pages may be freed if there wasn't any mapping
1683                 * like if add_to_swap() is running on a lru page that
1684                 * had its mapping zapped. And freeing these pages
1685                 * requires taking the lru_lock so we do the put_page
1686                 * of the tail pages after the split is complete.
1687                 */
1688                put_page(page_tail);
1689        }
1690
1691        /*
1692         * Only the head page (now become a regular page) is required
1693         * to be pinned by the caller.
1694         */
1695        BUG_ON(page_count(page) <= 0);
1696}
1697
1698static int __split_huge_page_map(struct page *page,
1699                                 struct vm_area_struct *vma,
1700                                 unsigned long address)
1701{
1702        struct mm_struct *mm = vma->vm_mm;
1703        pmd_t *pmd, _pmd;
1704        int ret = 0, i;
1705        pgtable_t pgtable;
1706        unsigned long haddr;
1707
1708        spin_lock(&mm->page_table_lock);
1709        pmd = page_check_address_pmd(page, mm, address,
1710                                     PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1711        if (pmd) {
1712                pgtable = pgtable_trans_huge_withdraw(mm);
1713                pmd_populate(mm, &_pmd, pgtable);
1714
1715                haddr = address;
1716                for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1717                        pte_t *pte, entry;
1718                        BUG_ON(PageCompound(page+i));
1719                        entry = mk_pte(page + i, vma->vm_page_prot);
1720                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1721                        if (!pmd_write(*pmd))
1722                                entry = pte_wrprotect(entry);
1723                        else
1724                                BUG_ON(page_mapcount(page) != 1);
1725                        if (!pmd_young(*pmd))
1726                                entry = pte_mkold(entry);
1727                        if (pmd_numa(*pmd))
1728                                entry = pte_mknuma(entry);
1729                        pte = pte_offset_map(&_pmd, haddr);
1730                        BUG_ON(!pte_none(*pte));
1731                        set_pte_at(mm, haddr, pte, entry);
1732                        pte_unmap(pte);
1733                }
1734
1735                smp_wmb(); /* make pte visible before pmd */
1736                /*
1737                 * Up to this point the pmd is present and huge and
1738                 * userland has the whole access to the hugepage
1739                 * during the split (which happens in place). If we
1740                 * overwrite the pmd with the not-huge version
1741                 * pointing to the pte here (which of course we could
1742                 * if all CPUs were bug free), userland could trigger
1743                 * a small page size TLB miss on the small sized TLB
1744                 * while the hugepage TLB entry is still established
1745                 * in the huge TLB. Some CPU doesn't like that. See
1746                 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1747                 * Erratum 383 on page 93. Intel should be safe but is
1748                 * also warns that it's only safe if the permission
1749                 * and cache attributes of the two entries loaded in
1750                 * the two TLB is identical (which should be the case
1751                 * here). But it is generally safer to never allow
1752                 * small and huge TLB entries for the same virtual
1753                 * address to be loaded simultaneously. So instead of
1754                 * doing "pmd_populate(); flush_tlb_range();" we first
1755                 * mark the current pmd notpresent (atomically because
1756                 * here the pmd_trans_huge and pmd_trans_splitting
1757                 * must remain set at all times on the pmd until the
1758                 * split is complete for this pmd), then we flush the
1759                 * SMP TLB and finally we write the non-huge version
1760                 * of the pmd entry with pmd_populate.
1761                 */
1762                pmdp_invalidate(vma, address, pmd);
1763                pmd_populate(mm, pmd, pgtable);
1764                ret = 1;
1765        }
1766        spin_unlock(&mm->page_table_lock);
1767
1768        return ret;
1769}
1770
1771/* must be called with anon_vma->root->rwsem held */
1772static void __split_huge_page(struct page *page,
1773                              struct anon_vma *anon_vma)
1774{
1775        int mapcount, mapcount2;
1776        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1777        struct anon_vma_chain *avc;
1778
1779        BUG_ON(!PageHead(page));
1780        BUG_ON(PageTail(page));
1781
1782        mapcount = 0;
1783        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1784                struct vm_area_struct *vma = avc->vma;
1785                unsigned long addr = vma_address(page, vma);
1786                BUG_ON(is_vma_temporary_stack(vma));
1787                mapcount += __split_huge_page_splitting(page, vma, addr);
1788        }
1789        /*
1790         * It is critical that new vmas are added to the tail of the
1791         * anon_vma list. This guarantes that if copy_huge_pmd() runs
1792         * and establishes a child pmd before
1793         * __split_huge_page_splitting() freezes the parent pmd (so if
1794         * we fail to prevent copy_huge_pmd() from running until the
1795         * whole __split_huge_page() is complete), we will still see
1796         * the newly established pmd of the child later during the
1797         * walk, to be able to set it as pmd_trans_splitting too.
1798         */
1799        if (mapcount != page_mapcount(page))
1800                printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1801                       mapcount, page_mapcount(page));
1802        BUG_ON(mapcount != page_mapcount(page));
1803
1804        __split_huge_page_refcount(page);
1805
1806        mapcount2 = 0;
1807        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1808                struct vm_area_struct *vma = avc->vma;
1809                unsigned long addr = vma_address(page, vma);
1810                BUG_ON(is_vma_temporary_stack(vma));
1811                mapcount2 += __split_huge_page_map(page, vma, addr);
1812        }
1813        if (mapcount != mapcount2)
1814                printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1815                       mapcount, mapcount2, page_mapcount(page));
1816        BUG_ON(mapcount != mapcount2);
1817}
1818
1819int split_huge_page(struct page *page)
1820{
1821        struct anon_vma *anon_vma;
1822        int ret = 1;
1823
1824        BUG_ON(is_huge_zero_pfn(page_to_pfn(page)));
1825        BUG_ON(!PageAnon(page));
1826
1827        /*
1828         * The caller does not necessarily hold an mmap_sem that would prevent
1829         * the anon_vma disappearing so we first we take a reference to it
1830         * and then lock the anon_vma for write. This is similar to
1831         * page_lock_anon_vma_read except the write lock is taken to serialise
1832         * against parallel split or collapse operations.
1833         */
1834        anon_vma = page_get_anon_vma(page);
1835        if (!anon_vma)
1836                goto out;
1837        anon_vma_lock_write(anon_vma);
1838
1839        ret = 0;
1840        if (!PageCompound(page))
1841                goto out_unlock;
1842
1843        BUG_ON(!PageSwapBacked(page));
1844        __split_huge_page(page, anon_vma);
1845        count_vm_event(THP_SPLIT);
1846
1847        BUG_ON(PageCompound(page));
1848out_unlock:
1849        anon_vma_unlock(anon_vma);
1850        put_anon_vma(anon_vma);
1851out:
1852        return ret;
1853}
1854
1855#define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1856
1857int hugepage_madvise(struct vm_area_struct *vma,
1858                     unsigned long *vm_flags, int advice)
1859{
1860        struct mm_struct *mm = vma->vm_mm;
1861
1862        switch (advice) {
1863        case MADV_HUGEPAGE:
1864                /*
1865                 * Be somewhat over-protective like KSM for now!
1866                 */
1867                if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1868                        return -EINVAL;
1869                if (mm->def_flags & VM_NOHUGEPAGE)
1870                        return -EINVAL;
1871                *vm_flags &= ~VM_NOHUGEPAGE;
1872                *vm_flags |= VM_HUGEPAGE;
1873                /*
1874                 * If the vma become good for khugepaged to scan,
1875                 * register it here without waiting a page fault that
1876                 * may not happen any time soon.
1877                 */
1878                if (unlikely(khugepaged_enter_vma_merge(vma)))
1879                        return -ENOMEM;
1880                break;
1881        case MADV_NOHUGEPAGE:
1882                /*
1883                 * Be somewhat over-protective like KSM for now!
1884                 */
1885                if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1886                        return -EINVAL;
1887                *vm_flags &= ~VM_HUGEPAGE;
1888                *vm_flags |= VM_NOHUGEPAGE;
1889                /*
1890                 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1891                 * this vma even if we leave the mm registered in khugepaged if
1892                 * it got registered before VM_NOHUGEPAGE was set.
1893                 */
1894                break;
1895        }
1896
1897        return 0;
1898}
1899
1900static int __init khugepaged_slab_init(void)
1901{
1902        mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1903                                          sizeof(struct mm_slot),
1904                                          __alignof__(struct mm_slot), 0, NULL);
1905        if (!mm_slot_cache)
1906                return -ENOMEM;
1907
1908        return 0;
1909}
1910
1911static void __init khugepaged_slab_free(void)
1912{
1913        kmem_cache_destroy(mm_slot_cache);
1914        mm_slot_cache = NULL;
1915}
1916
1917static inline struct mm_slot *alloc_mm_slot(void)
1918{
1919        if (!mm_slot_cache)     /* initialization failed */
1920                return NULL;
1921        return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1922}
1923
1924static inline void free_mm_slot(struct mm_slot *mm_slot)
1925{
1926        kmem_cache_free(mm_slot_cache, mm_slot);
1927}
1928
1929static int __init mm_slots_hash_init(void)
1930{
1931        mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1932                                GFP_KERNEL);
1933        if (!mm_slots_hash)
1934                return -ENOMEM;
1935        return 0;
1936}
1937
1938#if 0
1939static void __init mm_slots_hash_free(void)
1940{
1941        kfree(mm_slots_hash);
1942        mm_slots_hash = NULL;
1943}
1944#endif
1945
1946static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1947{
1948        struct mm_slot *mm_slot;
1949        struct hlist_head *bucket;
1950        struct hlist_node *node;
1951
1952        bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1953                                % MM_SLOTS_HASH_HEADS];
1954        hlist_for_each_entry(mm_slot, node, bucket, hash) {
1955                if (mm == mm_slot->mm)
1956                        return mm_slot;
1957        }
1958        return NULL;
1959}
1960
1961static void insert_to_mm_slots_hash(struct mm_struct *mm,
1962                                    struct mm_slot *mm_slot)
1963{
1964        struct hlist_head *bucket;
1965
1966        bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1967                                % MM_SLOTS_HASH_HEADS];
1968        mm_slot->mm = mm;
1969        hlist_add_head(&mm_slot->hash, bucket);
1970}
1971
1972static inline int khugepaged_test_exit(struct mm_struct *mm)
1973{
1974        return atomic_read(&mm->mm_users) == 0;
1975}
1976
1977int __khugepaged_enter(struct mm_struct *mm)
1978{
1979        struct mm_slot *mm_slot;
1980        int wakeup;
1981
1982        mm_slot = alloc_mm_slot();
1983        if (!mm_slot)
1984                return -ENOMEM;
1985
1986        /* __khugepaged_exit() must not run from under us */
1987        VM_BUG_ON(khugepaged_test_exit(mm));
1988        if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1989                free_mm_slot(mm_slot);
1990                return 0;
1991        }
1992
1993        spin_lock(&khugepaged_mm_lock);
1994        insert_to_mm_slots_hash(mm, mm_slot);
1995        /*
1996         * Insert just behind the scanning cursor, to let the area settle
1997         * down a little.
1998         */
1999        wakeup = list_empty(&khugepaged_scan.mm_head);
2000        list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
2001        spin_unlock(&khugepaged_mm_lock);
2002
2003        atomic_inc(&mm->mm_count);
2004        if (wakeup)
2005                wake_up_interruptible(&khugepaged_wait);
2006
2007        return 0;
2008}
2009
2010int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
2011{
2012        unsigned long hstart, hend;
2013        if (!vma->anon_vma)
2014                /*
2015                 * Not yet faulted in so we will register later in the
2016                 * page fault if needed.
2017                 */
2018                return 0;
2019        if (vma->vm_ops)
2020                /* khugepaged not yet working on file or special mappings */
2021                return 0;
2022        VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2023        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2024        hend = vma->vm_end & HPAGE_PMD_MASK;
2025        if (hstart < hend)
2026                return khugepaged_enter(vma);
2027        return 0;
2028}
2029
2030void __khugepaged_exit(struct mm_struct *mm)
2031{
2032        struct mm_slot *mm_slot;
2033        int free = 0;
2034
2035        spin_lock(&khugepaged_mm_lock);
2036        mm_slot = get_mm_slot(mm);
2037        if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2038                hlist_del(&mm_slot->hash);
2039                list_del(&mm_slot->mm_node);
2040                free = 1;
2041        }
2042        spin_unlock(&khugepaged_mm_lock);
2043
2044        if (free) {
2045                clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2046                free_mm_slot(mm_slot);
2047                mmdrop(mm);
2048        } else if (mm_slot) {
2049                /*
2050                 * This is required to serialize against
2051                 * khugepaged_test_exit() (which is guaranteed to run
2052                 * under mmap sem read mode). Stop here (after we
2053                 * return all pagetables will be destroyed) until
2054                 * khugepaged has finished working on the pagetables
2055                 * under the mmap_sem.
2056                 */
2057                down_write(&mm->mmap_sem);
2058                up_write(&mm->mmap_sem);
2059        }
2060}
2061
2062static void release_pte_page(struct page *page)
2063{
2064        /* 0 stands for page_is_file_cache(page) == false */
2065        dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2066        unlock_page(page);
2067        putback_lru_page(page);
2068}
2069
2070static void release_pte_pages(pte_t *pte, pte_t *_pte)
2071{
2072        while (--_pte >= pte) {
2073                pte_t pteval = *_pte;
2074                if (!pte_none(pteval))
2075                        release_pte_page(pte_page(pteval));
2076        }
2077}
2078
2079static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2080                                        unsigned long address,
2081                                        pte_t *pte)
2082{
2083        struct page *page;
2084        pte_t *_pte;
2085        int referenced = 0, none = 0;
2086        for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2087             _pte++, address += PAGE_SIZE) {
2088                pte_t pteval = *_pte;
2089                if (pte_none(pteval)) {
2090                        if (++none <= khugepaged_max_ptes_none)
2091                                continue;
2092                        else
2093                                goto out;
2094                }
2095                if (!pte_present(pteval) || !pte_write(pteval))
2096                        goto out;
2097                page = vm_normal_page(vma, address, pteval);
2098                if (unlikely(!page))
2099                        goto out;
2100
2101                VM_BUG_ON(PageCompound(page));
2102                BUG_ON(!PageAnon(page));
2103                VM_BUG_ON(!PageSwapBacked(page));
2104
2105                /* cannot use mapcount: can't collapse if there's a gup pin */
2106                if (page_count(page) != 1)
2107                        goto out;
2108                /*
2109                 * We can do it before isolate_lru_page because the
2110                 * page can't be freed from under us. NOTE: PG_lock
2111                 * is needed to serialize against split_huge_page
2112                 * when invoked from the VM.
2113                 */
2114                if (!trylock_page(page))
2115                        goto out;
2116                /*
2117                 * Isolate the page to avoid collapsing an hugepage
2118                 * currently in use by the VM.
2119                 */
2120                if (isolate_lru_page(page)) {
2121                        unlock_page(page);
2122                        goto out;
2123                }
2124                /* 0 stands for page_is_file_cache(page) == false */
2125                inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2126                VM_BUG_ON(!PageLocked(page));
2127                VM_BUG_ON(PageLRU(page));
2128
2129                /* If there is no mapped pte young don't collapse the page */
2130                if (pte_young(pteval) || PageReferenced(page) ||
2131                    mmu_notifier_test_young(vma->vm_mm, address))
2132                        referenced = 1;
2133        }
2134        if (likely(referenced))
2135                return 1;
2136out:
2137        release_pte_pages(pte, _pte);
2138        return 0;
2139}
2140
2141static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2142                                      struct vm_area_struct *vma,
2143                                      unsigned long address,
2144                                      spinlock_t *ptl)
2145{
2146        pte_t *_pte;
2147        for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2148                pte_t pteval = *_pte;
2149                struct page *src_page;
2150
2151                if (pte_none(pteval)) {
2152                        clear_user_highpage(page, address);
2153                        add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2154                } else {
2155                        src_page = pte_page(pteval);
2156                        copy_user_highpage(page, src_page, address, vma);
2157                        VM_BUG_ON(page_mapcount(src_page) != 1);
2158                        release_pte_page(src_page);
2159                        /*
2160                         * ptl mostly unnecessary, but preempt has to
2161                         * be disabled to update the per-cpu stats
2162                         * inside page_remove_rmap().
2163                         */
2164                        spin_lock(ptl);
2165                        /*
2166                         * paravirt calls inside pte_clear here are
2167                         * superfluous.
2168                         */
2169                        pte_clear(vma->vm_mm, address, _pte);
2170                        page_remove_rmap(src_page);
2171                        spin_unlock(ptl);
2172                        free_page_and_swap_cache(src_page);
2173                }
2174
2175                address += PAGE_SIZE;
2176                page++;
2177        }
2178}
2179
2180static void khugepaged_alloc_sleep(void)
2181{
2182        wait_event_freezable_timeout(khugepaged_wait, false,
2183                        msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2184}
2185
2186#ifdef CONFIG_NUMA
2187static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2188{
2189        if (IS_ERR(*hpage)) {
2190                if (!*wait)
2191                        return false;
2192
2193                *wait = false;
2194                *hpage = NULL;
2195                khugepaged_alloc_sleep();
2196        } else if (*hpage) {
2197                put_page(*hpage);
2198                *hpage = NULL;
2199        }
2200
2201        return true;
2202}
2203
2204static struct page
2205*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2206                       struct vm_area_struct *vma, unsigned long address,
2207                       int node)
2208{
2209        VM_BUG_ON(*hpage);
2210        /*
2211         * Allocate the page while the vma is still valid and under
2212         * the mmap_sem read mode so there is no memory allocation
2213         * later when we take the mmap_sem in write mode. This is more
2214         * friendly behavior (OTOH it may actually hide bugs) to
2215         * filesystems in userland with daemons allocating memory in
2216         * the userland I/O paths.  Allocating memory with the
2217         * mmap_sem in read mode is good idea also to allow greater
2218         * scalability.
2219         */
2220        *hpage  = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2221                                      node, __GFP_OTHER_NODE);
2222
2223        /*
2224         * After allocating the hugepage, release the mmap_sem read lock in
2225         * preparation for taking it in write mode.
2226         */
2227        up_read(&mm->mmap_sem);
2228        if (unlikely(!*hpage)) {
2229                count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2230                *hpage = ERR_PTR(-ENOMEM);
2231                return NULL;
2232        }
2233
2234        count_vm_event(THP_COLLAPSE_ALLOC);
2235        return *hpage;
2236}
2237#else
2238static struct page *khugepaged_alloc_hugepage(bool *wait)
2239{
2240        struct page *hpage;
2241
2242        do {
2243                hpage = alloc_hugepage(khugepaged_defrag());
2244                if (!hpage) {
2245                        count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2246                        if (!*wait)
2247                                return NULL;
2248
2249                        *wait = false;
2250                        khugepaged_alloc_sleep();
2251                } else
2252                        count_vm_event(THP_COLLAPSE_ALLOC);
2253        } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2254
2255        return hpage;
2256}
2257
2258static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2259{
2260        if (!*hpage)
2261                *hpage = khugepaged_alloc_hugepage(wait);
2262
2263        if (unlikely(!*hpage))
2264                return false;
2265
2266        return true;
2267}
2268
2269static struct page
2270*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2271                       struct vm_area_struct *vma, unsigned long address,
2272                       int node)
2273{
2274        up_read(&mm->mmap_sem);
2275        VM_BUG_ON(!*hpage);
2276        return  *hpage;
2277}
2278#endif
2279
2280static bool hugepage_vma_check(struct vm_area_struct *vma)
2281{
2282        if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2283            (vma->vm_flags & VM_NOHUGEPAGE))
2284                return false;
2285
2286        if (!vma->anon_vma || vma->vm_ops)
2287                return false;
2288        if (is_vma_temporary_stack(vma))
2289                return false;
2290        VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2291        return true;
2292}
2293
2294static void collapse_huge_page(struct mm_struct *mm,
2295                                   unsigned long address,
2296                                   struct page **hpage,
2297                                   struct vm_area_struct *vma,
2298                                   int node)
2299{
2300        pmd_t *pmd, _pmd;
2301        pte_t *pte;
2302        pgtable_t pgtable;
2303        struct page *new_page;
2304        spinlock_t *ptl;
2305        int isolated;
2306        unsigned long hstart, hend;
2307        unsigned long mmun_start;       /* For mmu_notifiers */
2308        unsigned long mmun_end;         /* For mmu_notifiers */
2309
2310        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2311
2312        /* release the mmap_sem read lock. */
2313        new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2314        if (!new_page)
2315                return;
2316
2317        if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2318                return;
2319
2320        /*
2321         * Prevent all access to pagetables with the exception of
2322         * gup_fast later hanlded by the ptep_clear_flush and the VM
2323         * handled by the anon_vma lock + PG_lock.
2324         */
2325        down_write(&mm->mmap_sem);
2326        if (unlikely(khugepaged_test_exit(mm)))
2327                goto out;
2328
2329        vma = find_vma(mm, address);
2330        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2331        hend = vma->vm_end & HPAGE_PMD_MASK;
2332        if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2333                goto out;
2334        if (!hugepage_vma_check(vma))
2335                goto out;
2336        pmd = mm_find_pmd(mm, address);
2337        if (!pmd)
2338                goto out;
2339        if (pmd_trans_huge(*pmd))
2340                goto out;
2341
2342        anon_vma_lock_write(vma->anon_vma);
2343
2344        pte = pte_offset_map(pmd, address);
2345        ptl = pte_lockptr(mm, pmd);
2346
2347        mmun_start = address;
2348        mmun_end   = address + HPAGE_PMD_SIZE;
2349        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2350        spin_lock(&mm->page_table_lock); /* probably unnecessary */
2351        /*
2352         * After this gup_fast can't run anymore. This also removes
2353         * any huge TLB entry from the CPU so we won't allow
2354         * huge and small TLB entries for the same virtual address
2355         * to avoid the risk of CPU bugs in that area.
2356         */
2357        _pmd = pmdp_clear_flush(vma, address, pmd);
2358        spin_unlock(&mm->page_table_lock);
2359        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2360
2361        spin_lock(ptl);
2362        isolated = __collapse_huge_page_isolate(vma, address, pte);
2363        spin_unlock(ptl);
2364
2365        if (unlikely(!isolated)) {
2366                pte_unmap(pte);
2367                spin_lock(&mm->page_table_lock);
2368                BUG_ON(!pmd_none(*pmd));
2369                set_pmd_at(mm, address, pmd, _pmd);
2370                spin_unlock(&mm->page_table_lock);
2371                anon_vma_unlock(vma->anon_vma);
2372                goto out;
2373        }
2374
2375        /*
2376         * All pages are isolated and locked so anon_vma rmap
2377         * can't run anymore.
2378         */
2379        anon_vma_unlock(vma->anon_vma);
2380
2381        __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2382        pte_unmap(pte);
2383        __SetPageUptodate(new_page);
2384        pgtable = pmd_pgtable(_pmd);
2385
2386        _pmd = mk_huge_pmd(new_page, vma);
2387
2388        /*
2389         * spin_lock() below is not the equivalent of smp_wmb(), so
2390         * this is needed to avoid the copy_huge_page writes to become
2391         * visible after the set_pmd_at() write.
2392         */
2393        smp_wmb();
2394
2395        spin_lock(&mm->page_table_lock);
2396        BUG_ON(!pmd_none(*pmd));
2397        page_add_new_anon_rmap(new_page, vma, address);
2398        set_pmd_at(mm, address, pmd, _pmd);
2399        update_mmu_cache_pmd(vma, address, pmd);
2400        pgtable_trans_huge_deposit(mm, pgtable);
2401        spin_unlock(&mm->page_table_lock);
2402
2403        *hpage = NULL;
2404
2405        khugepaged_pages_collapsed++;
2406out_up_write:
2407        up_write(&mm->mmap_sem);
2408        return;
2409
2410out:
2411        mem_cgroup_uncharge_page(new_page);
2412        goto out_up_write;
2413}
2414
2415static int khugepaged_scan_pmd(struct mm_struct *mm,
2416                               struct vm_area_struct *vma,
2417                               unsigned long address,
2418                               struct page **hpage)
2419{
2420        pmd_t *pmd;
2421        pte_t *pte, *_pte;
2422        int ret = 0, referenced = 0, none = 0;
2423        struct page *page;
2424        unsigned long _address;
2425        spinlock_t *ptl;
2426        int node = -1;
2427
2428        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2429
2430        pmd = mm_find_pmd(mm, address);
2431        if (!pmd)
2432                goto out;
2433        if (pmd_trans_huge(*pmd))
2434                goto out;
2435
2436        pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2437        for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2438             _pte++, _address += PAGE_SIZE) {
2439                pte_t pteval = *_pte;
2440                if (pte_none(pteval)) {
2441                        if (++none <= khugepaged_max_ptes_none)
2442                                continue;
2443                        else
2444                                goto out_unmap;
2445                }
2446                if (!pte_present(pteval) || !pte_write(pteval))
2447                        goto out_unmap;
2448                page = vm_normal_page(vma, _address, pteval);
2449                if (unlikely(!page))
2450                        goto out_unmap;
2451                /*
2452                 * Chose the node of the first page. This could
2453                 * be more sophisticated and look at more pages,
2454                 * but isn't for now.
2455                 */
2456                if (node == -1)
2457                        node = page_to_nid(page);
2458                VM_BUG_ON(PageCompound(page));
2459                if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2460                        goto out_unmap;
2461                /* cannot use mapcount: can't collapse if there's a gup pin */
2462                if (page_count(page) != 1)
2463                        goto out_unmap;
2464                if (pte_young(pteval) || PageReferenced(page) ||
2465                    mmu_notifier_test_young(vma->vm_mm, address))
2466                        referenced = 1;
2467        }
2468        if (referenced)
2469                ret = 1;
2470out_unmap:
2471        pte_unmap_unlock(pte, ptl);
2472        if (ret)
2473                /* collapse_huge_page will return with the mmap_sem released */
2474                collapse_huge_page(mm, address, hpage, vma, node);
2475out:
2476        return ret;
2477}
2478
2479static void collect_mm_slot(struct mm_slot *mm_slot)
2480{
2481        struct mm_struct *mm = mm_slot->mm;
2482
2483        VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2484
2485        if (khugepaged_test_exit(mm)) {
2486                /* free mm_slot */
2487                hlist_del(&mm_slot->hash);
2488                list_del(&mm_slot->mm_node);
2489
2490                /*
2491                 * Not strictly needed because the mm exited already.
2492                 *
2493                 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2494                 */
2495
2496                /* khugepaged_mm_lock actually not necessary for the below */
2497                free_mm_slot(mm_slot);
2498                mmdrop(mm);
2499        }
2500}
2501
2502static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2503                                            struct page **hpage)
2504        __releases(&khugepaged_mm_lock)
2505        __acquires(&khugepaged_mm_lock)
2506{
2507        struct mm_slot *mm_slot;
2508        struct mm_struct *mm;
2509        struct vm_area_struct *vma;
2510        int progress = 0;
2511
2512        VM_BUG_ON(!pages);
2513        VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2514
2515        if (khugepaged_scan.mm_slot)
2516                mm_slot = khugepaged_scan.mm_slot;
2517        else {
2518                mm_slot = list_entry(khugepaged_scan.mm_head.next,
2519                                     struct mm_slot, mm_node);
2520                khugepaged_scan.address = 0;
2521                khugepaged_scan.mm_slot = mm_slot;
2522        }
2523        spin_unlock(&khugepaged_mm_lock);
2524
2525        mm = mm_slot->mm;
2526        down_read(&mm->mmap_sem);
2527        if (unlikely(khugepaged_test_exit(mm)))
2528                vma = NULL;
2529        else
2530                vma = find_vma(mm, khugepaged_scan.address);
2531
2532        progress++;
2533        for (; vma; vma = vma->vm_next) {
2534                unsigned long hstart, hend;
2535
2536                cond_resched();
2537                if (unlikely(khugepaged_test_exit(mm))) {
2538                        progress++;
2539                        break;
2540                }
2541                if (!hugepage_vma_check(vma)) {
2542skip:
2543                        progress++;
2544                        continue;
2545                }
2546                hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2547                hend = vma->vm_end & HPAGE_PMD_MASK;
2548                if (hstart >= hend)
2549                        goto skip;
2550                if (khugepaged_scan.address > hend)
2551                        goto skip;
2552                if (khugepaged_scan.address < hstart)
2553                        khugepaged_scan.address = hstart;
2554                VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2555
2556                while (khugepaged_scan.address < hend) {
2557                        int ret;
2558                        cond_resched();
2559                        if (unlikely(khugepaged_test_exit(mm)))
2560                                goto breakouterloop;
2561
2562                        VM_BUG_ON(khugepaged_scan.address < hstart ||
2563                                  khugepaged_scan.address + HPAGE_PMD_SIZE >
2564                                  hend);
2565                        ret = khugepaged_scan_pmd(mm, vma,
2566                                                  khugepaged_scan.address,
2567                                                  hpage);
2568                        /* move to next address */
2569                        khugepaged_scan.address += HPAGE_PMD_SIZE;
2570                        progress += HPAGE_PMD_NR;
2571                        if (ret)
2572                                /* we released mmap_sem so break loop */
2573                                goto breakouterloop_mmap_sem;
2574                        if (progress >= pages)
2575                                goto breakouterloop;
2576                }
2577        }
2578breakouterloop:
2579        up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2580breakouterloop_mmap_sem:
2581
2582        spin_lock(&khugepaged_mm_lock);
2583        VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2584        /*
2585         * Release the current mm_slot if this mm is about to die, or
2586         * if we scanned all vmas of this mm.
2587         */
2588        if (khugepaged_test_exit(mm) || !vma) {
2589                /*
2590                 * Make sure that if mm_users is reaching zero while
2591                 * khugepaged runs here, khugepaged_exit will find
2592                 * mm_slot not pointing to the exiting mm.
2593                 */
2594                if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2595                        khugepaged_scan.mm_slot = list_entry(
2596                                mm_slot->mm_node.next,
2597                                struct mm_slot, mm_node);
2598                        khugepaged_scan.address = 0;
2599                } else {
2600                        khugepaged_scan.mm_slot = NULL;
2601                        khugepaged_full_scans++;
2602                }
2603
2604                collect_mm_slot(mm_slot);
2605        }
2606
2607        return progress;
2608}
2609
2610static int khugepaged_has_work(void)
2611{
2612        return !list_empty(&khugepaged_scan.mm_head) &&
2613                khugepaged_enabled();
2614}
2615
2616static int khugepaged_wait_event(void)
2617{
2618        return !list_empty(&khugepaged_scan.mm_head) ||
2619                kthread_should_stop();
2620}
2621
2622static void khugepaged_do_scan(void)
2623{
2624        struct page *hpage = NULL;
2625        unsigned int progress = 0, pass_through_head = 0;
2626        unsigned int pages = khugepaged_pages_to_scan;
2627        bool wait = true;
2628
2629        barrier(); /* write khugepaged_pages_to_scan to local stack */
2630
2631        while (progress < pages) {
2632                if (!khugepaged_prealloc_page(&hpage, &wait))
2633                        break;
2634
2635                cond_resched();
2636
2637                if (unlikely(kthread_should_stop() || freezing(current)))
2638                        break;
2639
2640                spin_lock(&khugepaged_mm_lock);
2641                if (!khugepaged_scan.mm_slot)
2642                        pass_through_head++;
2643                if (khugepaged_has_work() &&
2644                    pass_through_head < 2)
2645                        progress += khugepaged_scan_mm_slot(pages - progress,
2646                                                            &hpage);
2647                else
2648                        progress = pages;
2649                spin_unlock(&khugepaged_mm_lock);
2650        }
2651
2652        if (!IS_ERR_OR_NULL(hpage))
2653                put_page(hpage);
2654}
2655
2656static void khugepaged_wait_work(void)
2657{
2658        try_to_freeze();
2659
2660        if (khugepaged_has_work()) {
2661                if (!khugepaged_scan_sleep_millisecs)
2662                        return;
2663
2664                wait_event_freezable_timeout(khugepaged_wait,
2665                                             kthread_should_stop(),
2666                        msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2667                return;
2668        }
2669
2670        if (khugepaged_enabled())
2671                wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2672}
2673
2674static int khugepaged(void *none)
2675{
2676        struct mm_slot *mm_slot;
2677
2678        set_freezable();
2679        set_user_nice(current, 19);
2680
2681        while (!kthread_should_stop()) {
2682                khugepaged_do_scan();
2683                khugepaged_wait_work();
2684        }
2685
2686        spin_lock(&khugepaged_mm_lock);
2687        mm_slot = khugepaged_scan.mm_slot;
2688        khugepaged_scan.mm_slot = NULL;
2689        if (mm_slot)
2690                collect_mm_slot(mm_slot);
2691        spin_unlock(&khugepaged_mm_lock);
2692        return 0;
2693}
2694
2695static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2696                unsigned long haddr, pmd_t *pmd)
2697{
2698        struct mm_struct *mm = vma->vm_mm;
2699        pgtable_t pgtable;
2700        pmd_t _pmd;
2701        int i;
2702
2703        pmdp_clear_flush(vma, haddr, pmd);
2704        /* leave pmd empty until pte is filled */
2705
2706        pgtable = pgtable_trans_huge_withdraw(mm);
2707        pmd_populate(mm, &_pmd, pgtable);
2708
2709        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2710                pte_t *pte, entry;
2711                entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2712                entry = pte_mkspecial(entry);
2713                pte = pte_offset_map(&_pmd, haddr);
2714                VM_BUG_ON(!pte_none(*pte));
2715                set_pte_at(mm, haddr, pte, entry);
2716                pte_unmap(pte);
2717        }
2718        smp_wmb(); /* make pte visible before pmd */
2719        pmd_populate(mm, pmd, pgtable);
2720        put_huge_zero_page();
2721}
2722
2723void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2724                pmd_t *pmd)
2725{
2726        struct page *page;
2727        struct mm_struct *mm = vma->vm_mm;
2728        unsigned long haddr = address & HPAGE_PMD_MASK;
2729        unsigned long mmun_start;       /* For mmu_notifiers */
2730        unsigned long mmun_end;         /* For mmu_notifiers */
2731
2732        BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2733
2734        mmun_start = haddr;
2735        mmun_end   = haddr + HPAGE_PMD_SIZE;
2736        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2737        spin_lock(&mm->page_table_lock);
2738        if (unlikely(!pmd_trans_huge(*pmd))) {
2739                spin_unlock(&mm->page_table_lock);
2740                mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2741                return;
2742        }
2743        if (is_huge_zero_pmd(*pmd)) {
2744                __split_huge_zero_page_pmd(vma, haddr, pmd);
2745                spin_unlock(&mm->page_table_lock);
2746                mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2747                return;
2748        }
2749        page = pmd_page(*pmd);
2750        VM_BUG_ON(!page_count(page));
2751        get_page(page);
2752        spin_unlock(&mm->page_table_lock);
2753        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2754
2755        split_huge_page(page);
2756
2757        put_page(page);
2758        BUG_ON(pmd_trans_huge(*pmd));
2759}
2760
2761void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2762                pmd_t *pmd)
2763{
2764        struct vm_area_struct *vma;
2765
2766        vma = find_vma(mm, address);
2767        BUG_ON(vma == NULL);
2768        split_huge_page_pmd(vma, address, pmd);
2769}
2770
2771static void split_huge_page_address(struct mm_struct *mm,
2772                                    unsigned long address)
2773{
2774        pmd_t *pmd;
2775
2776        VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2777
2778        pmd = mm_find_pmd(mm, address);
2779        if (!pmd)
2780                return;
2781        /*
2782         * Caller holds the mmap_sem write mode, so a huge pmd cannot
2783         * materialize from under us.
2784         */
2785        split_huge_page_pmd_mm(mm, address, pmd);
2786}
2787
2788void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2789                             unsigned long start,
2790                             unsigned long end,
2791                             long adjust_next)
2792{
2793        /*
2794         * If the new start address isn't hpage aligned and it could
2795         * previously contain an hugepage: check if we need to split
2796         * an huge pmd.
2797         */
2798        if (start & ~HPAGE_PMD_MASK &&
2799            (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2800            (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2801                split_huge_page_address(vma->vm_mm, start);
2802
2803        /*
2804         * If the new end address isn't hpage aligned and it could
2805         * previously contain an hugepage: check if we need to split
2806         * an huge pmd.
2807         */
2808        if (end & ~HPAGE_PMD_MASK &&
2809            (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2810            (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2811                split_huge_page_address(vma->vm_mm, end);
2812
2813        /*
2814         * If we're also updating the vma->vm_next->vm_start, if the new
2815         * vm_next->vm_start isn't page aligned and it could previously
2816         * contain an hugepage: check if we need to split an huge pmd.
2817         */
2818        if (adjust_next > 0) {
2819                struct vm_area_struct *next = vma->vm_next;
2820                unsigned long nstart = next->vm_start;
2821                nstart += adjust_next << PAGE_SHIFT;
2822                if (nstart & ~HPAGE_PMD_MASK &&
2823                    (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2824                    (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2825                        split_huge_page_address(next->vm_mm, nstart);
2826        }
2827}
2828
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