mm/huge_memory.c

   1 /*
   2  *  Copyright (C) 2009  Red Hat, Inc.
   3  *
   4  *  This work is licensed under the terms of the GNU GPL, version 2. See
   5  *  the COPYING file in the top-level directory.
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/sched.h>
  10 #include <linux/highmem.h>
  11 #include <linux/hugetlb.h>
  12 #include <linux/mmu_notifier.h>
  13 #include <linux/rmap.h>
  14 #include <linux/swap.h>
  15 #include <linux/shrinker.h>
  16 #include <linux/mm_inline.h>
  17 #include <linux/kthread.h>
  18 #include <linux/khugepaged.h>
  19 #include <linux/freezer.h>
  20 #include <linux/mman.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/migrate.h>
  23 #include <linux/hashtable.h>
  24
  25 #include <asm/tlb.h>
  26 #include <asm/pgalloc.h>
  27 #include "internal.h"
  28
  29 /*
  30  * By default transparent hugepage support is disabled in order that avoid
  31  * to risk increase the memory footprint of applications without a guaranteed
  32  * benefit. When transparent hugepage support is enabled, is for all mappings,
  33  * and khugepaged scans all mappings.
  34  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  35  * for all hugepage allocations.
  36  */
  37 unsigned long transparent_hugepage_flags __read_mostly =
  38 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  39         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  40 #endif
  41 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  42         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  43 #endif
  44         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
  45         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  46         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  47
  48 /* default scan 8*512 pte (or vmas) every 30 second */
  49 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
  50 static unsigned int khugepaged_pages_collapsed;
  51 static unsigned int khugepaged_full_scans;
  52 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  53 /* during fragmentation poll the hugepage allocator once every minute */
  54 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  55 static struct task_struct *khugepaged_thread __read_mostly;
  56 static DEFINE_MUTEX(khugepaged_mutex);
  57 static DEFINE_SPINLOCK(khugepaged_mm_lock);
  58 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  59 /*
  60  * default collapse hugepages if there is at least one pte mapped like
  61  * it would have happened if the vma was large enough during page
  62  * fault.
  63  */
  64 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
  65
  66 static int khugepaged(void *none);
  67 static int khugepaged_slab_init(void);
  68
  69 #define MM_SLOTS_HASH_BITS 10
  70 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
  71
  72 static struct kmem_cache *mm_slot_cache __read_mostly;
  73
  74 /**
  75  * struct mm_slot - hash lookup from mm to mm_slot
  76  * @hash: hash collision list
  77  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
  78  * @mm: the mm that this information is valid for
  79  */
  80 struct mm_slot {
  81         struct hlist_node hash;
  82         struct list_head mm_node;
  83         struct mm_struct *mm;
  84 };
  85
  86 /**
  87  * struct khugepaged_scan - cursor for scanning
  88  * @mm_head: the head of the mm list to scan
  89  * @mm_slot: the current mm_slot we are scanning
  90  * @address: the next address inside that to be scanned
  91  *
  92  * There is only the one khugepaged_scan instance of this cursor structure.
  93  */
  94 struct khugepaged_scan {
  95         struct list_head mm_head;
  96         struct mm_slot *mm_slot;
  97         unsigned long address;
  98 };
  99 static struct khugepaged_scan khugepaged_scan = {
 100         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
 101 };
 102
 103
 104 static int set_recommended_min_free_kbytes(void)
 105 {
 106         struct zone *zone;
 107         int nr_zones = 0;
 108         unsigned long recommended_min;
 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                 if (user_min_free_kbytes >= 0)
 135                         pr_info("raising min_free_kbytes from %d to %lu "
 136                                 "to help transparent hugepage allocations\n",
 137                                 min_free_kbytes, recommended_min);
 138
 139                 min_free_kbytes = recommended_min;
 140         }
 141         setup_per_zone_wmarks();
 142         return 0;
 143 }
 144 late_initcall(set_recommended_min_free_kbytes);
 145
 146 static int start_khugepaged(void)
 147 {
 148         int err = 0;
 149         if (khugepaged_enabled()) {
 150                 if (!khugepaged_thread)
 151                         khugepaged_thread = kthread_run(khugepaged, NULL,
 152                                                         "khugepaged");
 153                 if (unlikely(IS_ERR(khugepaged_thread))) {
 154                         printk(KERN_ERR
 155                                "khugepaged: kthread_run(khugepaged) failed\n");
 156                         err = PTR_ERR(khugepaged_thread);
 157                         khugepaged_thread = NULL;
 158                 }
 159
 160                 if (!list_empty(&khugepaged_scan.mm_head))
 161                         wake_up_interruptible(&khugepaged_wait);
 162
 163                 set_recommended_min_free_kbytes();
 164         } else if (khugepaged_thread) {
 165                 kthread_stop(khugepaged_thread);
 166                 khugepaged_thread = NULL;
 167         }
 168
 169         return err;
 170 }
 171
 172 static atomic_t huge_zero_refcount;
 173 static struct page *huge_zero_page __read_mostly;
 174
 175 static inline bool is_huge_zero_page(struct page *page)
 176 {
 177         return ACCESS_ONCE(huge_zero_page) == page;
 178 }
 179
 180 static inline bool is_huge_zero_pmd(pmd_t pmd)
 181 {
 182         return is_huge_zero_page(pmd_page(pmd));
 183 }
 184
 185 static struct page *get_huge_zero_page(void)
 186 {
 187         struct page *zero_page;
 188 retry:
 189         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 190                 return ACCESS_ONCE(huge_zero_page);
 191
 192         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 193                         HPAGE_PMD_ORDER);
 194         if (!zero_page) {
 195                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 196                 return NULL;
 197         }
 198         count_vm_event(THP_ZERO_PAGE_ALLOC);
 199         preempt_disable();
 200         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 201                 preempt_enable();
 202                 __free_page(zero_page);
 203                 goto retry;
 204         }
 205
 206         /* We take additional reference here. It will be put back by shrinker */
 207         atomic_set(&huge_zero_refcount, 2);
 208         preempt_enable();
 209         return ACCESS_ONCE(huge_zero_page);
 210 }
 211
 212 static void put_huge_zero_page(void)
 213 {
 214         /*
 215          * Counter should never go to zero here. Only shrinker can put
 216          * last reference.
 217          */
 218         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 219 }
 220
 221 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 222                                         struct shrink_control *sc)
 223 {
 224         /* we can free zero page only if last reference remains */
 225         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 226 }
 227
 228 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 229                                        struct shrink_control *sc)
 230 {
 231         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 232                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 233                 BUG_ON(zero_page == NULL);
 234                 __free_page(zero_page);
 235                 return HPAGE_PMD_NR;
 236         }
 237
 238         return 0;
 239 }
 240
 241 static struct shrinker huge_zero_page_shrinker = {
 242         .count_objects = shrink_huge_zero_page_count,
 243         .scan_objects = shrink_huge_zero_page_scan,
 244         .seeks = DEFAULT_SEEKS,
 245 };
 246
 247 #ifdef CONFIG_SYSFS
 248
 249 static ssize_t double_flag_show(struct kobject *kobj,
 250                                 struct kobj_attribute *attr, char *buf,
 251                                 enum transparent_hugepage_flag enabled,
 252                                 enum transparent_hugepage_flag req_madv)
 253 {
 254         if (test_bit(enabled, &transparent_hugepage_flags)) {
 255                 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
 256                 return sprintf(buf, "[always] madvise never\n");
 257         } else if (test_bit(req_madv, &transparent_hugepage_flags))
 258                 return sprintf(buf, "always [madvise] never\n");
 259         else
 260                 return sprintf(buf, "always madvise [never]\n");
 261 }
 262 static ssize_t double_flag_store(struct kobject *kobj,
 263                                  struct kobj_attribute *attr,
 264                                  const char *buf, size_t count,
 265                                  enum transparent_hugepage_flag enabled,
 266                                  enum transparent_hugepage_flag req_madv)
 267 {
 268         if (!memcmp("always", buf,
 269                     min(sizeof("always")-1, count))) {
 270                 set_bit(enabled, &transparent_hugepage_flags);
 271                 clear_bit(req_madv, &transparent_hugepage_flags);
 272         } else if (!memcmp("madvise", buf,
 273                            min(sizeof("madvise")-1, count))) {
 274                 clear_bit(enabled, &transparent_hugepage_flags);
 275                 set_bit(req_madv, &transparent_hugepage_flags);
 276         } else if (!memcmp("never", buf,
 277                            min(sizeof("never")-1, count))) {
 278                 clear_bit(enabled, &transparent_hugepage_flags);
 279                 clear_bit(req_madv, &transparent_hugepage_flags);
 280         } else
 281                 return -EINVAL;
 282
 283         return count;
 284 }
 285
 286 static ssize_t enabled_show(struct kobject *kobj,
 287                             struct kobj_attribute *attr, char *buf)
 288 {
 289         return double_flag_show(kobj, attr, buf,
 290                                 TRANSPARENT_HUGEPAGE_FLAG,
 291                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 292 }
 293 static ssize_t enabled_store(struct kobject *kobj,
 294                              struct kobj_attribute *attr,
 295                              const char *buf, size_t count)
 296 {
 297         ssize_t ret;
 298
 299         ret = double_flag_store(kobj, attr, buf, count,
 300                                 TRANSPARENT_HUGEPAGE_FLAG,
 301                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 302
 303         if (ret > 0) {
 304                 int err;
 305
 306                 mutex_lock(&khugepaged_mutex);
 307                 err = start_khugepaged();
 308                 mutex_unlock(&khugepaged_mutex);
 309
 310                 if (err)
 311                         ret = err;
 312         }
 313
 314         return ret;
 315 }
 316 static struct kobj_attribute enabled_attr =
 317         __ATTR(enabled, 0644, enabled_show, enabled_store);
 318
 319 static ssize_t single_flag_show(struct kobject *kobj,
 320                                 struct kobj_attribute *attr, char *buf,
 321                                 enum transparent_hugepage_flag flag)
 322 {
 323         return sprintf(buf, "%d\n",
 324                        !!test_bit(flag, &transparent_hugepage_flags));
 325 }
 326
 327 static ssize_t single_flag_store(struct kobject *kobj,
 328                                  struct kobj_attribute *attr,
 329                                  const char *buf, size_t count,
 330                                  enum transparent_hugepage_flag flag)
 331 {
 332         unsigned long value;
 333         int ret;
 334
 335         ret = kstrtoul(buf, 10, &value);
 336         if (ret < 0)
 337                 return ret;
 338         if (value > 1)
 339                 return -EINVAL;
 340
 341         if (value)
 342                 set_bit(flag, &transparent_hugepage_flags);
 343         else
 344                 clear_bit(flag, &transparent_hugepage_flags);
 345
 346         return count;
 347 }
 348
 349 /*
 350  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 351  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 352  * memory just to allocate one more hugepage.
 353  */
 354 static ssize_t defrag_show(struct kobject *kobj,
 355                            struct kobj_attribute *attr, char *buf)
 356 {
 357         return double_flag_show(kobj, attr, buf,
 358                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 359                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 360 }
 361 static ssize_t defrag_store(struct kobject *kobj,
 362                             struct kobj_attribute *attr,
 363                             const char *buf, size_t count)
 364 {
 365         return double_flag_store(kobj, attr, buf, count,
 366                                  TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 367                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 368 }
 369 static struct kobj_attribute defrag_attr =
 370         __ATTR(defrag, 0644, defrag_show, defrag_store);
 371
 372 static ssize_t use_zero_page_show(struct kobject *kobj,
 373                 struct kobj_attribute *attr, char *buf)
 374 {
 375         return single_flag_show(kobj, attr, buf,
 376                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 377 }
 378 static ssize_t use_zero_page_store(struct kobject *kobj,
 379                 struct kobj_attribute *attr, const char *buf, size_t count)
 380 {
 381         return single_flag_store(kobj, attr, buf, count,
 382                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 383 }
 384 static struct kobj_attribute use_zero_page_attr =
 385         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 386 #ifdef CONFIG_DEBUG_VM
 387 static ssize_t debug_cow_show(struct kobject *kobj,
 388                                 struct kobj_attribute *attr, char *buf)
 389 {
 390         return single_flag_show(kobj, attr, buf,
 391                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 392 }
 393 static ssize_t debug_cow_store(struct kobject *kobj,
 394                                struct kobj_attribute *attr,
 395                                const char *buf, size_t count)
 396 {
 397         return single_flag_store(kobj, attr, buf, count,
 398                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 399 }
 400 static struct kobj_attribute debug_cow_attr =
 401         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 402 #endif /* CONFIG_DEBUG_VM */
 403
 404 static struct attribute *hugepage_attr[] = {
 405         &enabled_attr.attr,
 406         &defrag_attr.attr,
 407         &use_zero_page_attr.attr,
 408 #ifdef CONFIG_DEBUG_VM
 409         &debug_cow_attr.attr,
 410 #endif
 411         NULL,
 412 };
 413
 414 static struct attribute_group hugepage_attr_group = {
 415         .attrs = hugepage_attr,
 416 };
 417
 418 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 419                                          struct kobj_attribute *attr,
 420                                          char *buf)
 421 {
 422         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 423 }
 424
 425 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 426                                           struct kobj_attribute *attr,
 427                                           const char *buf, size_t count)
 428 {
 429         unsigned long msecs;
 430         int err;
 431
 432         err = kstrtoul(buf, 10, &msecs);
 433         if (err || msecs > UINT_MAX)
 434                 return -EINVAL;
 435
 436         khugepaged_scan_sleep_millisecs = msecs;
 437         wake_up_interruptible(&khugepaged_wait);
 438
 439         return count;
 440 }
 441 static struct kobj_attribute scan_sleep_millisecs_attr =
 442         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 443                scan_sleep_millisecs_store);
 444
 445 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 446                                           struct kobj_attribute *attr,
 447                                           char *buf)
 448 {
 449         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 450 }
 451
 452 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 453                                            struct kobj_attribute *attr,
 454                                            const char *buf, size_t count)
 455 {
 456         unsigned long msecs;
 457         int err;
 458
 459         err = kstrtoul(buf, 10, &msecs);
 460         if (err || msecs > UINT_MAX)
 461                 return -EINVAL;
 462
 463         khugepaged_alloc_sleep_millisecs = msecs;
 464         wake_up_interruptible(&khugepaged_wait);
 465
 466         return count;
 467 }
 468 static struct kobj_attribute alloc_sleep_millisecs_attr =
 469         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 470                alloc_sleep_millisecs_store);
 471
 472 static ssize_t pages_to_scan_show(struct kobject *kobj,
 473                                   struct kobj_attribute *attr,
 474                                   char *buf)
 475 {
 476         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 477 }
 478 static ssize_t pages_to_scan_store(struct kobject *kobj,
 479                                    struct kobj_attribute *attr,
 480                                    const char *buf, size_t count)
 481 {
 482         int err;
 483         unsigned long pages;
 484
 485         err = kstrtoul(buf, 10, &pages);
 486         if (err || !pages || pages > UINT_MAX)
 487                 return -EINVAL;
 488
 489         khugepaged_pages_to_scan = pages;
 490
 491         return count;
 492 }
 493 static struct kobj_attribute pages_to_scan_attr =
 494         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 495                pages_to_scan_store);
 496
 497 static ssize_t pages_collapsed_show(struct kobject *kobj,
 498                                     struct kobj_attribute *attr,
 499                                     char *buf)
 500 {
 501         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 502 }
 503 static struct kobj_attribute pages_collapsed_attr =
 504         __ATTR_RO(pages_collapsed);
 505
 506 static ssize_t full_scans_show(struct kobject *kobj,
 507                                struct kobj_attribute *attr,
 508                                char *buf)
 509 {
 510         return sprintf(buf, "%u\n", khugepaged_full_scans);
 511 }
 512 static struct kobj_attribute full_scans_attr =
 513         __ATTR_RO(full_scans);
 514
 515 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 516                                       struct kobj_attribute *attr, char *buf)
 517 {
 518         return single_flag_show(kobj, attr, buf,
 519                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 520 }
 521 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 522                                        struct kobj_attribute *attr,
 523                                        const char *buf, size_t count)
 524 {
 525         return single_flag_store(kobj, attr, buf, count,
 526                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 527 }
 528 static struct kobj_attribute khugepaged_defrag_attr =
 529         __ATTR(defrag, 0644, khugepaged_defrag_show,
 530                khugepaged_defrag_store);
 531
 532 /*
 533  * max_ptes_none controls if khugepaged should collapse hugepages over
 534  * any unmapped ptes in turn potentially increasing the memory
 535  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 536  * reduce the available free memory in the system as it
 537  * runs. Increasing max_ptes_none will instead potentially reduce the
 538  * free memory in the system during the khugepaged scan.
 539  */
 540 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 541                                              struct kobj_attribute *attr,
 542                                              char *buf)
 543 {
 544         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 545 }
 546 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 547                                               struct kobj_attribute *attr,
 548                                               const char *buf, size_t count)
 549 {
 550         int err;
 551         unsigned long max_ptes_none;
 552
 553         err = kstrtoul(buf, 10, &max_ptes_none);
 554         if (err || max_ptes_none > HPAGE_PMD_NR-1)
 555                 return -EINVAL;
 556
 557         khugepaged_max_ptes_none = max_ptes_none;
 558
 559         return count;
 560 }
 561 static struct kobj_attribute khugepaged_max_ptes_none_attr =
 562         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 563                khugepaged_max_ptes_none_store);
 564
 565 static struct attribute *khugepaged_attr[] = {
 566         &khugepaged_defrag_attr.attr,
 567         &khugepaged_max_ptes_none_attr.attr,
 568         &pages_to_scan_attr.attr,
 569         &pages_collapsed_attr.attr,
 570         &full_scans_attr.attr,
 571         &scan_sleep_millisecs_attr.attr,
 572         &alloc_sleep_millisecs_attr.attr,
 573         NULL,
 574 };
 575
 576 static struct attribute_group khugepaged_attr_group = {
 577         .attrs = khugepaged_attr,
 578         .name = "khugepaged",
 579 };
 580
 581 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 582 {
 583         int err;
 584
 585         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 586         if (unlikely(!*hugepage_kobj)) {
 587                 printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n");
 588                 return -ENOMEM;
 589         }
 590
 591         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 592         if (err) {
 593                 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
 594                 goto delete_obj;
 595         }
 596
 597         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 598         if (err) {
 599                 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
 600                 goto remove_hp_group;
 601         }
 602
 603         return 0;
 604
 605 remove_hp_group:
 606         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 607 delete_obj:
 608         kobject_put(*hugepage_kobj);
 609         return err;
 610 }
 611
 612 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 613 {
 614         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 615         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 616         kobject_put(hugepage_kobj);
 617 }
 618 #else
 619 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 620 {
 621         return 0;
 622 }
 623
 624 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 625 {
 626 }
 627 #endif /* CONFIG_SYSFS */
 628
 629 static int __init hugepage_init(void)
 630 {
 631         int err;
 632         struct kobject *hugepage_kobj;
 633
 634         if (!has_transparent_hugepage()) {
 635                 transparent_hugepage_flags = 0;
 636                 return -EINVAL;
 637         }
 638
 639         err = hugepage_init_sysfs(&hugepage_kobj);
 640         if (err)
 641                 return err;
 642
 643         err = khugepaged_slab_init();
 644         if (err)
 645                 goto out;
 646
 647         register_shrinker(&huge_zero_page_shrinker);
 648
 649         /*
 650          * By default disable transparent hugepages on smaller systems,
 651          * where the extra memory used could hurt more than TLB overhead
 652          * is likely to save.  The admin can still enable it through /sys.
 653          */
 654         if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
 655                 transparent_hugepage_flags = 0;
 656
 657         start_khugepaged();
 658
 659         return 0;
 660 out:
 661         hugepage_exit_sysfs(hugepage_kobj);
 662         return err;
 663 }
 664 subsys_initcall(hugepage_init);
 665
 666 static int __init setup_transparent_hugepage(char *str)
 667 {
 668         int ret = 0;
 669         if (!str)
 670                 goto out;
 671         if (!strcmp(str, "always")) {
 672                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 673                         &transparent_hugepage_flags);
 674                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 675                           &transparent_hugepage_flags);
 676                 ret = 1;
 677         } else if (!strcmp(str, "madvise")) {
 678                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 679                           &transparent_hugepage_flags);
 680                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 681                         &transparent_hugepage_flags);
 682                 ret = 1;
 683         } else if (!strcmp(str, "never")) {
 684                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 685                           &transparent_hugepage_flags);
 686                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 687                           &transparent_hugepage_flags);
 688                 ret = 1;
 689         }
 690 out:
 691         if (!ret)
 692                 printk(KERN_WARNING
 693                        "transparent_hugepage= cannot parse, ignored\n");
 694         return ret;
 695 }
 696 __setup("transparent_hugepage=", setup_transparent_hugepage);
 697
 698 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 699 {
 700         if (likely(vma->vm_flags & VM_WRITE))
 701                 pmd = pmd_mkwrite(pmd);
 702         return pmd;
 703 }
 704
 705 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
 706 {
 707         pmd_t entry;
 708         entry = mk_pmd(page, prot);
 709         entry = pmd_mkhuge(entry);
 710         return entry;
 711 }
 712
 713 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 714                                         struct vm_area_struct *vma,
 715                                         unsigned long haddr, pmd_t *pmd,
 716                                         struct page *page)
 717 {
 718         pgtable_t pgtable;
 719         spinlock_t *ptl;
 720
 721         VM_BUG_ON_PAGE(!PageCompound(page), page);
 722         pgtable = pte_alloc_one(mm, haddr);
 723         if (unlikely(!pgtable))
 724                 return VM_FAULT_OOM;
 725
 726         clear_huge_page(page, haddr, HPAGE_PMD_NR);
 727         /*
 728          * The memory barrier inside __SetPageUptodate makes sure that
 729          * clear_huge_page writes become visible before the set_pmd_at()
 730          * write.
 731          */
 732         __SetPageUptodate(page);
 733
 734         ptl = pmd_lock(mm, pmd);
 735         if (unlikely(!pmd_none(*pmd))) {
 736                 spin_unlock(ptl);
 737                 mem_cgroup_uncharge_page(page);
 738                 put_page(page);
 739                 pte_free(mm, pgtable);
 740         } else {
 741                 pmd_t entry;
 742                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 743                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 744                 page_add_new_anon_rmap(page, vma, haddr);
 745                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 746                 set_pmd_at(mm, haddr, pmd, entry);
 747                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 748                 atomic_long_inc(&mm->nr_ptes);
 749                 spin_unlock(ptl);
 750         }
 751
 752         return 0;
 753 }
 754
 755 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 756 {
 757         return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
 758 }
 759
 760 static inline struct page *alloc_hugepage_vma(int defrag,
 761                                               struct vm_area_struct *vma,
 762                                               unsigned long haddr, int nd,
 763                                               gfp_t extra_gfp)
 764 {
 765         return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
 766                                HPAGE_PMD_ORDER, vma, haddr, nd);
 767 }
 768
 769 /* Caller must hold page table lock. */
 770 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 771                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 772                 struct page *zero_page)
 773 {
 774         pmd_t entry;
 775         if (!pmd_none(*pmd))
 776                 return false;
 777         entry = mk_pmd(zero_page, vma->vm_page_prot);
 778         entry = pmd_wrprotect(entry);
 779         entry = pmd_mkhuge(entry);
 780         pgtable_trans_huge_deposit(mm, pmd, pgtable);
 781         set_pmd_at(mm, haddr, pmd, entry);
 782         atomic_long_inc(&mm->nr_ptes);
 783         return true;
 784 }
 785
 786 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 787                                unsigned long address, pmd_t *pmd,
 788                                unsigned int flags)
 789 {
 790         struct page *page;
 791         unsigned long haddr = address & HPAGE_PMD_MASK;
 792
 793         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 794                 return VM_FAULT_FALLBACK;
 795         if (unlikely(anon_vma_prepare(vma)))
 796                 return VM_FAULT_OOM;
 797         if (unlikely(khugepaged_enter(vma)))
 798                 return VM_FAULT_OOM;
 799         if (!(flags & FAULT_FLAG_WRITE) &&
 800                         transparent_hugepage_use_zero_page()) {
 801                 spinlock_t *ptl;
 802                 pgtable_t pgtable;
 803                 struct page *zero_page;
 804                 bool set;
 805                 pgtable = pte_alloc_one(mm, haddr);
 806                 if (unlikely(!pgtable))
 807                         return VM_FAULT_OOM;
 808                 zero_page = get_huge_zero_page();
 809                 if (unlikely(!zero_page)) {
 810                         pte_free(mm, pgtable);
 811                         count_vm_event(THP_FAULT_FALLBACK);
 812                         return VM_FAULT_FALLBACK;
 813                 }
 814                 ptl = pmd_lock(mm, pmd);
 815                 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
 816                                 zero_page);
 817                 spin_unlock(ptl);
 818                 if (!set) {
 819                         pte_free(mm, pgtable);
 820                         put_huge_zero_page();
 821                 }
 822                 return 0;
 823         }
 824         page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
 825                         vma, haddr, numa_node_id(), 0);
 826         if (unlikely(!page)) {
 827                 count_vm_event(THP_FAULT_FALLBACK);
 828                 return VM_FAULT_FALLBACK;
 829         }
 830         if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
 831                 put_page(page);
 832                 count_vm_event(THP_FAULT_FALLBACK);
 833                 return VM_FAULT_FALLBACK;
 834         }
 835         if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) {
 836                 mem_cgroup_uncharge_page(page);
 837                 put_page(page);
 838                 count_vm_event(THP_FAULT_FALLBACK);
 839                 return VM_FAULT_FALLBACK;
 840         }
 841
 842         count_vm_event(THP_FAULT_ALLOC);
 843         return 0;
 844 }
 845
 846 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 847                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 848                   struct vm_area_struct *vma)
 849 {
 850         spinlock_t *dst_ptl, *src_ptl;
 851         struct page *src_page;
 852         pmd_t pmd;
 853         pgtable_t pgtable;
 854         int ret;
 855
 856         ret = -ENOMEM;
 857         pgtable = pte_alloc_one(dst_mm, addr);
 858         if (unlikely(!pgtable))
 859                 goto out;
 860
 861         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 862         src_ptl = pmd_lockptr(src_mm, src_pmd);
 863         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 864
 865         ret = -EAGAIN;
 866         pmd = *src_pmd;
 867         if (unlikely(!pmd_trans_huge(pmd))) {
 868                 pte_free(dst_mm, pgtable);
 869                 goto out_unlock;
 870         }
 871         /*
 872          * When page table lock is held, the huge zero pmd should not be
 873          * under splitting since we don't split the page itself, only pmd to
 874          * a page table.
 875          */
 876         if (is_huge_zero_pmd(pmd)) {
 877                 struct page *zero_page;
 878                 bool set;
 879                 /*
 880                  * get_huge_zero_page() will never allocate a new page here,
 881                  * since we already have a zero page to copy. It just takes a
 882                  * reference.
 883                  */
 884                 zero_page = get_huge_zero_page();
 885                 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 886                                 zero_page);
 887                 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
 888                 ret = 0;
 889                 goto out_unlock;
 890         }
 891
 892         if (unlikely(pmd_trans_splitting(pmd))) {
 893                 /* split huge page running from under us */
 894                 spin_unlock(src_ptl);
 895                 spin_unlock(dst_ptl);
 896                 pte_free(dst_mm, pgtable);
 897
 898                 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
 899                 goto out;
 900         }
 901         src_page = pmd_page(pmd);
 902         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 903         get_page(src_page);
 904         page_dup_rmap(src_page);
 905         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 906
 907         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 908         pmd = pmd_mkold(pmd_wrprotect(pmd));
 909         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 910         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 911         atomic_long_inc(&dst_mm->nr_ptes);
 912
 913         ret = 0;
 914 out_unlock:
 915         spin_unlock(src_ptl);
 916         spin_unlock(dst_ptl);
 917 out:
 918         return ret;
 919 }
 920
 921 void huge_pmd_set_accessed(struct mm_struct *mm,
 922                            struct vm_area_struct *vma,
 923                            unsigned long address,
 924                            pmd_t *pmd, pmd_t orig_pmd,
 925                            int dirty)
 926 {
 927         spinlock_t *ptl;
 928         pmd_t entry;
 929         unsigned long haddr;
 930
 931         ptl = pmd_lock(mm, pmd);
 932         if (unlikely(!pmd_same(*pmd, orig_pmd)))
 933                 goto unlock;
 934
 935         entry = pmd_mkyoung(orig_pmd);
 936         haddr = address & HPAGE_PMD_MASK;
 937         if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
 938                 update_mmu_cache_pmd(vma, address, pmd);
 939
 940 unlock:
 941         spin_unlock(ptl);
 942 }
 943
 944 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
 945                 struct vm_area_struct *vma, unsigned long address,
 946                 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
 947 {
 948         spinlock_t *ptl;
 949         pgtable_t pgtable;
 950         pmd_t _pmd;
 951         struct page *page;
 952         int i, ret = 0;
 953         unsigned long mmun_start;       /* For mmu_notifiers */
 954         unsigned long mmun_end;         /* For mmu_notifiers */
 955
 956         page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
 957         if (!page) {
 958                 ret |= VM_FAULT_OOM;
 959                 goto out;
 960         }
 961
 962         if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
 963                 put_page(page);
 964                 ret |= VM_FAULT_OOM;
 965                 goto out;
 966         }
 967
 968         clear_user_highpage(page, address);
 969         __SetPageUptodate(page);
 970
 971         mmun_start = haddr;
 972         mmun_end   = haddr + HPAGE_PMD_SIZE;
 973         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 974
 975         ptl = pmd_lock(mm, pmd);
 976         if (unlikely(!pmd_same(*pmd, orig_pmd)))
 977                 goto out_free_page;
 978
 979         pmdp_clear_flush(vma, haddr, pmd);
 980         /* leave pmd empty until pte is filled */
 981
 982         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
 983         pmd_populate(mm, &_pmd, pgtable);
 984
 985         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
 986                 pte_t *pte, entry;
 987                 if (haddr == (address & PAGE_MASK)) {
 988                         entry = mk_pte(page, vma->vm_page_prot);
 989                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 990                         page_add_new_anon_rmap(page, vma, haddr);
 991                 } else {
 992                         entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
 993                         entry = pte_mkspecial(entry);
 994                 }
 995                 pte = pte_offset_map(&_pmd, haddr);
 996                 VM_BUG_ON(!pte_none(*pte));
 997                 set_pte_at(mm, haddr, pte, entry);
 998                 pte_unmap(pte);
 999         }
1000         smp_wmb(); /* make pte visible before pmd */
1001         pmd_populate(mm, pmd, pgtable);
1002         spin_unlock(ptl);
1003         put_huge_zero_page();
1004         inc_mm_counter(mm, MM_ANONPAGES);
1005
1006         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1007
1008         ret |= VM_FAULT_WRITE;
1009 out:
1010         return ret;
1011 out_free_page:
1012         spin_unlock(ptl);
1013         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1014         mem_cgroup_uncharge_page(page);
1015         put_page(page);
1016         goto out;
1017 }
1018
1019 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1020                                         struct vm_area_struct *vma,
1021                                         unsigned long address,
1022                                         pmd_t *pmd, pmd_t orig_pmd,
1023                                         struct page *page,
1024                                         unsigned long haddr)
1025 {
1026         spinlock_t *ptl;
1027         pgtable_t pgtable;
1028         pmd_t _pmd;
1029         int ret = 0, i;
1030         struct page **pages;
1031         unsigned long mmun_start;       /* For mmu_notifiers */
1032         unsigned long mmun_end;         /* For mmu_notifiers */
1033
1034         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1035                         GFP_KERNEL);
1036         if (unlikely(!pages)) {
1037                 ret |= VM_FAULT_OOM;
1038                 goto out;
1039         }
1040
1041         for (i = 0; i < HPAGE_PMD_NR; i++) {
1042                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1043                                                __GFP_OTHER_NODE,
1044                                                vma, address, page_to_nid(page));
1045                 if (unlikely(!pages[i] ||
1046                              mem_cgroup_newpage_charge(pages[i], mm,
1047                                                        GFP_KERNEL))) {
1048                         if (pages[i])
1049                                 put_page(pages[i]);
1050                         mem_cgroup_uncharge_start();
1051                         while (--i >= 0) {
1052                                 mem_cgroup_uncharge_page(pages[i]);
1053                                 put_page(pages[i]);
1054                         }
1055                         mem_cgroup_uncharge_end();
1056                         kfree(pages);
1057                         ret |= VM_FAULT_OOM;
1058                         goto out;
1059                 }
1060         }
1061
1062         for (i = 0; i < HPAGE_PMD_NR; i++) {
1063                 copy_user_highpage(pages[i], page + i,
1064                                    haddr + PAGE_SIZE * i, vma);
1065                 __SetPageUptodate(pages[i]);
1066                 cond_resched();
1067         }
1068
1069         mmun_start = haddr;
1070         mmun_end   = haddr + HPAGE_PMD_SIZE;
1071         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1072
1073         ptl = pmd_lock(mm, pmd);
1074         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1075                 goto out_free_pages;
1076         VM_BUG_ON_PAGE(!PageHead(page), page);
1077
1078         pmdp_clear_flush(vma, haddr, pmd);
1079         /* leave pmd empty until pte is filled */
1080
1081         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1082         pmd_populate(mm, &_pmd, pgtable);
1083
1084         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1085                 pte_t *pte, entry;
1086                 entry = mk_pte(pages[i], vma->vm_page_prot);
1087                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1088                 page_add_new_anon_rmap(pages[i], vma, haddr);
1089                 pte = pte_offset_map(&_pmd, haddr);
1090                 VM_BUG_ON(!pte_none(*pte));
1091                 set_pte_at(mm, haddr, pte, entry);
1092                 pte_unmap(pte);
1093         }
1094         kfree(pages);
1095
1096         smp_wmb(); /* make pte visible before pmd */
1097         pmd_populate(mm, pmd, pgtable);
1098         page_remove_rmap(page);
1099         spin_unlock(ptl);
1100
1101         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1102
1103         ret |= VM_FAULT_WRITE;
1104         put_page(page);
1105
1106 out:
1107         return ret;
1108
1109 out_free_pages:
1110         spin_unlock(ptl);
1111         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1112         mem_cgroup_uncharge_start();
1113         for (i = 0; i < HPAGE_PMD_NR; i++) {
1114                 mem_cgroup_uncharge_page(pages[i]);
1115                 put_page(pages[i]);
1116         }
1117         mem_cgroup_uncharge_end();
1118         kfree(pages);
1119         goto out;
1120 }
1121
1122 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1123                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1124 {
1125         spinlock_t *ptl;
1126         int ret = 0;
1127         struct page *page = NULL, *new_page;
1128         unsigned long haddr;
1129         unsigned long mmun_start;       /* For mmu_notifiers */
1130         unsigned long mmun_end;         /* For mmu_notifiers */
1131
1132         ptl = pmd_lockptr(mm, pmd);
1133         VM_BUG_ON(!vma->anon_vma);
1134         haddr = address & HPAGE_PMD_MASK;
1135         if (is_huge_zero_pmd(orig_pmd))
1136                 goto alloc;
1137         spin_lock(ptl);
1138         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1139                 goto out_unlock;
1140
1141         page = pmd_page(orig_pmd);
1142         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1143         if (page_mapcount(page) == 1) {
1144                 pmd_t entry;
1145                 entry = pmd_mkyoung(orig_pmd);
1146                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1147                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1148                         update_mmu_cache_pmd(vma, address, pmd);
1149                 ret |= VM_FAULT_WRITE;
1150                 goto out_unlock;
1151         }
1152         get_page(page);
1153         spin_unlock(ptl);
1154 alloc:
1155         if (transparent_hugepage_enabled(vma) &&
1156             !transparent_hugepage_debug_cow())
1157                 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1158                                               vma, haddr, numa_node_id(), 0);
1159         else
1160                 new_page = NULL;
1161
1162         if (unlikely(!new_page)) {
1163                 if (!page) {
1164                         ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1165                                         address, pmd, orig_pmd, haddr);
1166                 } else {
1167                         ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1168                                         pmd, orig_pmd, page, haddr);
1169                         if (ret & VM_FAULT_OOM)
1170                                 split_huge_page(page);
1171                         put_page(page);
1172                 }
1173                 count_vm_event(THP_FAULT_FALLBACK);
1174                 goto out;
1175         }
1176
1177         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1178                 put_page(new_page);
1179                 if (page) {
1180                         split_huge_page(page);
1181                         put_page(page);
1182                 }
1183                 count_vm_event(THP_FAULT_FALLBACK);
1184                 ret |= VM_FAULT_OOM;
1185                 goto out;
1186         }
1187
1188         count_vm_event(THP_FAULT_ALLOC);
1189
1190         if (!page)
1191                 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1192         else
1193                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1194         __SetPageUptodate(new_page);
1195
1196         mmun_start = haddr;
1197         mmun_end   = haddr + HPAGE_PMD_SIZE;
1198         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1199
1200         spin_lock(ptl);
1201         if (page)
1202                 put_page(page);
1203         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1204                 spin_unlock(ptl);
1205                 mem_cgroup_uncharge_page(new_page);
1206                 put_page(new_page);
1207                 goto out_mn;
1208         } else {
1209                 pmd_t entry;
1210                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1211                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1212                 pmdp_clear_flush(vma, haddr, pmd);
1213                 page_add_new_anon_rmap(new_page, vma, haddr);
1214                 set_pmd_at(mm, haddr, pmd, entry);
1215                 update_mmu_cache_pmd(vma, address, pmd);
1216                 if (!page) {
1217                         add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1218                         put_huge_zero_page();
1219                 } else {
1220                         VM_BUG_ON_PAGE(!PageHead(page), page);
1221                         page_remove_rmap(page);
1222                         put_page(page);
1223                 }
1224                 ret |= VM_FAULT_WRITE;
1225         }
1226         spin_unlock(ptl);
1227 out_mn:
1228         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1229 out:
1230         return ret;
1231 out_unlock:
1232         spin_unlock(ptl);
1233         return ret;
1234 }
1235
1236 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1237                                    unsigned long addr,
1238                                    pmd_t *pmd,
1239                                    unsigned int flags)
1240 {
1241         struct mm_struct *mm = vma->vm_mm;
1242         struct page *page = NULL;
1243
1244         assert_spin_locked(pmd_lockptr(mm, pmd));
1245
1246         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1247                 goto out;
1248
1249         /* Avoid dumping huge zero page */
1250         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1251                 return ERR_PTR(-EFAULT);
1252
1253         /* Full NUMA hinting faults to serialise migration in fault paths */
1254         if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
1255                 goto out;
1256
1257         page = pmd_page(*pmd);
1258         VM_BUG_ON_PAGE(!PageHead(page), page);
1259         if (flags & FOLL_TOUCH) {
1260                 pmd_t _pmd;
1261                 /*
1262                  * We should set the dirty bit only for FOLL_WRITE but
1263                  * for now the dirty bit in the pmd is meaningless.
1264                  * And if the dirty bit will become meaningful and
1265                  * we'll only set it with FOLL_WRITE, an atomic
1266                  * set_bit will be required on the pmd to set the
1267                  * young bit, instead of the current set_pmd_at.
1268                  */
1269                 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1270                 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1271                                           pmd, _pmd,  1))
1272                         update_mmu_cache_pmd(vma, addr, pmd);
1273         }
1274         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1275                 if (page->mapping && trylock_page(page)) {
1276                         lru_add_drain();
1277                         if (page->mapping)
1278                                 mlock_vma_page(page);
1279                         unlock_page(page);
1280                 }
1281         }
1282         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1283         VM_BUG_ON_PAGE(!PageCompound(page), page);
1284         if (flags & FOLL_GET)
1285                 get_page_foll(page);
1286
1287 out:
1288         return page;
1289 }
1290
1291 /* NUMA hinting page fault entry point for trans huge pmds */
1292 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1293                                 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1294 {
1295         spinlock_t *ptl;
1296         struct anon_vma *anon_vma = NULL;
1297         struct page *page;
1298         unsigned long haddr = addr & HPAGE_PMD_MASK;
1299         int page_nid = -1, this_nid = numa_node_id();
1300         int target_nid, last_cpupid = -1;
1301         bool page_locked;
1302         bool migrated = false;
1303         int flags = 0;
1304
1305         ptl = pmd_lock(mm, pmdp);
1306         if (unlikely(!pmd_same(pmd, *pmdp)))
1307                 goto out_unlock;
1308
1309         /*
1310          * If there are potential migrations, wait for completion and retry
1311          * without disrupting NUMA hinting information. Do not relock and
1312          * check_same as the page may no longer be mapped.
1313          */
1314         if (unlikely(pmd_trans_migrating(*pmdp))) {
1315                 spin_unlock(ptl);
1316                 wait_migrate_huge_page(vma->anon_vma, pmdp);
1317                 goto out;
1318         }
1319
1320         page = pmd_page(pmd);
1321         BUG_ON(is_huge_zero_page(page));
1322         page_nid = page_to_nid(page);
1323         last_cpupid = page_cpupid_last(page);
1324         count_vm_numa_event(NUMA_HINT_FAULTS);
1325         if (page_nid == this_nid) {
1326                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1327                 flags |= TNF_FAULT_LOCAL;
1328         }
1329
1330         /*
1331          * Avoid grouping on DSO/COW pages in specific and RO pages
1332          * in general, RO pages shouldn't hurt as much anyway since
1333          * they can be in shared cache state.
1334          */
1335         if (!pmd_write(pmd))
1336                 flags |= TNF_NO_GROUP;
1337
1338         /*
1339          * Acquire the page lock to serialise THP migrations but avoid dropping
1340          * page_table_lock if at all possible
1341          */
1342         page_locked = trylock_page(page);
1343         target_nid = mpol_misplaced(page, vma, haddr);
1344         if (target_nid == -1) {
1345                 /* If the page was locked, there are no parallel migrations */
1346                 if (page_locked)
1347                         goto clear_pmdnuma;
1348         }
1349
1350         /* Migration could have started since the pmd_trans_migrating check */
1351         if (!page_locked) {
1352                 spin_unlock(ptl);
1353                 wait_on_page_locked(page);
1354                 page_nid = -1;
1355                 goto out;
1356         }
1357
1358         /*
1359          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1360          * to serialises splits
1361          */
1362         get_page(page);
1363         spin_unlock(ptl);
1364         anon_vma = page_lock_anon_vma_read(page);
1365
1366         /* Confirm the PMD did not change while page_table_lock was released */
1367         spin_lock(ptl);
1368         if (unlikely(!pmd_same(pmd, *pmdp))) {
1369                 unlock_page(page);
1370                 put_page(page);
1371                 page_nid = -1;
1372                 goto out_unlock;
1373         }
1374
1375         /* Bail if we fail to protect against THP splits for any reason */
1376         if (unlikely(!anon_vma)) {
1377                 put_page(page);
1378                 page_nid = -1;
1379                 goto clear_pmdnuma;
1380         }
1381
1382         /*
1383          * Migrate the THP to the requested node, returns with page unlocked
1384          * and pmd_numa cleared.
1385          */
1386         spin_unlock(ptl);
1387         migrated = migrate_misplaced_transhuge_page(mm, vma,
1388                                 pmdp, pmd, addr, page, target_nid);
1389         if (migrated) {
1390                 flags |= TNF_MIGRATED;
1391                 page_nid = target_nid;
1392         }
1393
1394         goto out;
1395 clear_pmdnuma:
1396         BUG_ON(!PageLocked(page));
1397         pmd = pmd_mknonnuma(pmd);
1398         set_pmd_at(mm, haddr, pmdp, pmd);
1399         VM_BUG_ON(pmd_numa(*pmdp));
1400         update_mmu_cache_pmd(vma, addr, pmdp);
1401         unlock_page(page);
1402 out_unlock:
1403         spin_unlock(ptl);
1404
1405 out:
1406         if (anon_vma)
1407                 page_unlock_anon_vma_read(anon_vma);
1408
1409         if (page_nid != -1)
1410                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1411
1412         return 0;
1413 }
1414
1415 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1416                  pmd_t *pmd, unsigned long addr)
1417 {
1418         spinlock_t *ptl;
1419         int ret = 0;
1420
1421         if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1422                 struct page *page;
1423                 pgtable_t pgtable;
1424                 pmd_t orig_pmd;
1425                 /*
1426                  * For architectures like ppc64 we look at deposited pgtable
1427                  * when calling pmdp_get_and_clear. So do the
1428                  * pgtable_trans_huge_withdraw after finishing pmdp related
1429                  * operations.
1430                  */
1431                 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1432                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1433                 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1434                 if (is_huge_zero_pmd(orig_pmd)) {
1435                         atomic_long_dec(&tlb->mm->nr_ptes);
1436                         spin_unlock(ptl);
1437                         put_huge_zero_page();
1438                 } else {
1439                         page = pmd_page(orig_pmd);
1440                         page_remove_rmap(page);
1441                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1442                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1443                         VM_BUG_ON_PAGE(!PageHead(page), page);
1444                         atomic_long_dec(&tlb->mm->nr_ptes);
1445                         spin_unlock(ptl);
1446                         tlb_remove_page(tlb, page);
1447                 }
1448                 pte_free(tlb->mm, pgtable);
1449                 ret = 1;
1450         }
1451         return ret;
1452 }
1453
1454 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1455                 unsigned long addr, unsigned long end,
1456                 unsigned char *vec)
1457 {
1458         spinlock_t *ptl;
1459         int ret = 0;
1460
1461         if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1462                 /*
1463                  * All logical pages in the range are present
1464                  * if backed by a huge page.
1465                  */
1466                 spin_unlock(ptl);
1467                 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1468                 ret = 1;
1469         }
1470
1471         return ret;
1472 }
1473
1474 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1475                   unsigned long old_addr,
1476                   unsigned long new_addr, unsigned long old_end,
1477                   pmd_t *old_pmd, pmd_t *new_pmd)
1478 {
1479         spinlock_t *old_ptl, *new_ptl;
1480         int ret = 0;
1481         pmd_t pmd;
1482
1483         struct mm_struct *mm = vma->vm_mm;
1484
1485         if ((old_addr & ~HPAGE_PMD_MASK) ||
1486             (new_addr & ~HPAGE_PMD_MASK) ||
1487             old_end - old_addr < HPAGE_PMD_SIZE ||
1488             (new_vma->vm_flags & VM_NOHUGEPAGE))
1489                 goto out;
1490
1491         /*
1492          * The destination pmd shouldn't be established, free_pgtables()
1493          * should have release it.
1494          */
1495         if (WARN_ON(!pmd_none(*new_pmd))) {
1496                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1497                 goto out;
1498         }
1499
1500         /*
1501          * We don't have to worry about the ordering of src and dst
1502          * ptlocks because exclusive mmap_sem prevents deadlock.
1503          */
1504         ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
1505         if (ret == 1) {
1506                 new_ptl = pmd_lockptr(mm, new_pmd);
1507                 if (new_ptl != old_ptl)
1508                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1509                 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1510                 VM_BUG_ON(!pmd_none(*new_pmd));
1511
1512                 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1513                         pgtable_t pgtable;
1514                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1515                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1516                 }
1517                 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1518                 if (new_ptl != old_ptl)
1519                         spin_unlock(new_ptl);
1520                 spin_unlock(old_ptl);
1521         }
1522 out:
1523         return ret;
1524 }
1525
1526 /*
1527  * Returns
1528  *  - 0 if PMD could not be locked
1529  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1530  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1531  */
1532 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1533                 unsigned long addr, pgprot_t newprot, int prot_numa)
1534 {
1535         struct mm_struct *mm = vma->vm_mm;
1536         spinlock_t *ptl;
1537         int ret = 0;
1538
1539         if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
1540                 pmd_t entry;
1541                 ret = 1;
1542                 if (!prot_numa) {
1543                         entry = pmdp_get_and_clear(mm, addr, pmd);
1544                         if (pmd_numa(entry))
1545                                 entry = pmd_mknonnuma(entry);
1546                         entry = pmd_modify(entry, newprot);
1547                         ret = HPAGE_PMD_NR;
1548                         set_pmd_at(mm, addr, pmd, entry);
1549                         BUG_ON(pmd_write(entry));
1550                 } else {
1551                         struct page *page = pmd_page(*pmd);
1552
1553                         /*
1554                          * Do not trap faults against the zero page. The
1555                          * read-only data is likely to be read-cached on the
1556                          * local CPU cache and it is less useful to know about
1557                          * local vs remote hits on the zero page.
1558                          */
1559                         if (!is_huge_zero_page(page) &&
1560                             !pmd_numa(*pmd)) {
1561                                 pmdp_set_numa(mm, addr, pmd);
1562                                 ret = HPAGE_PMD_NR;
1563                         }
1564                 }
1565                 spin_unlock(ptl);
1566         }
1567
1568         return ret;
1569 }
1570
1571 /*
1572  * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1573  * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1574  *
1575  * Note that if it returns 1, this routine returns without unlocking page
1576  * table locks. So callers must unlock them.
1577  */
1578 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1579                 spinlock_t **ptl)
1580 {
1581         *ptl = pmd_lock(vma->vm_mm, pmd);
1582         if (likely(pmd_trans_huge(*pmd))) {
1583                 if (unlikely(pmd_trans_splitting(*pmd))) {
1584                         spin_unlock(*ptl);
1585                         wait_split_huge_page(vma->anon_vma, pmd);
1586                         return -1;
1587                 } else {
1588                         /* Thp mapped by 'pmd' is stable, so we can
1589                          * handle it as it is. */
1590                         return 1;
1591                 }
1592         }
1593         spin_unlock(*ptl);
1594         return 0;
1595 }
1596
1597 /*
1598  * This function returns whether a given @page is mapped onto the @address
1599  * in the virtual space of @mm.
1600  *
1601  * When it's true, this function returns *pmd with holding the page table lock
1602  * and passing it back to the caller via @ptl.
1603  * If it's false, returns NULL without holding the page table lock.
1604  */
1605 pmd_t *page_check_address_pmd(struct page *page,
1606                               struct mm_struct *mm,
1607                               unsigned long address,
1608                               enum page_check_address_pmd_flag flag,
1609                               spinlock_t **ptl)
1610 {
1611         pmd_t *pmd;
1612
1613         if (address & ~HPAGE_PMD_MASK)
1614                 return NULL;
1615
1616         pmd = mm_find_pmd(mm, address);
1617         if (!pmd)
1618                 return NULL;
1619         *ptl = pmd_lock(mm, pmd);
1620         if (pmd_none(*pmd))
1621                 goto unlock;
1622         if (pmd_page(*pmd) != page)
1623                 goto unlock;
1624         /*
1625          * split_vma() may create temporary aliased mappings. There is
1626          * no risk as long as all huge pmd are found and have their
1627          * splitting bit set before __split_huge_page_refcount
1628          * runs. Finding the same huge pmd more than once during the
1629          * same rmap walk is not a problem.
1630          */
1631         if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1632             pmd_trans_splitting(*pmd))
1633                 goto unlock;
1634         if (pmd_trans_huge(*pmd)) {
1635                 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1636                           !pmd_trans_splitting(*pmd));
1637                 return pmd;
1638         }
1639 unlock:
1640         spin_unlock(*ptl);
1641         return NULL;
1642 }
1643
1644 static int __split_huge_page_splitting(struct page *page,
1645                                        struct vm_area_struct *vma,
1646                                        unsigned long address)
1647 {
1648         struct mm_struct *mm = vma->vm_mm;
1649         spinlock_t *ptl;
1650         pmd_t *pmd;
1651         int ret = 0;
1652         /* For mmu_notifiers */
1653         const unsigned long mmun_start = address;
1654         const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1655
1656         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1657         pmd = page_check_address_pmd(page, mm, address,
1658                         PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl);
1659         if (pmd) {
1660                 /*
1661                  * We can't temporarily set the pmd to null in order
1662                  * to split it, the pmd must remain marked huge at all
1663                  * times or the VM won't take the pmd_trans_huge paths
1664                  * and it won't wait on the anon_vma->root->rwsem to
1665                  * serialize against split_huge_page*.
1666                  */
1667                 pmdp_splitting_flush(vma, address, pmd);
1668                 ret = 1;
1669                 spin_unlock(ptl);
1670         }
1671         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1672
1673         return ret;
1674 }
1675
1676 static void __split_huge_page_refcount(struct page *page,
1677                                        struct list_head *list)
1678 {
1679         int i;
1680         struct zone *zone = page_zone(page);
1681         struct lruvec *lruvec;
1682         int tail_count = 0;
1683
1684         /* prevent PageLRU to go away from under us, and freeze lru stats */
1685         spin_lock_irq(&zone->lru_lock);
1686         lruvec = mem_cgroup_page_lruvec(page, zone);
1687
1688         compound_lock(page);
1689         /* complete memcg works before add pages to LRU */
1690         mem_cgroup_split_huge_fixup(page);
1691
1692         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1693                 struct page *page_tail = page + i;
1694
1695                 /* tail_page->_mapcount cannot change */
1696                 BUG_ON(page_mapcount(page_tail) < 0);
1697                 tail_count += page_mapcount(page_tail);
1698                 /* check for overflow */
1699                 BUG_ON(tail_count < 0);
1700                 BUG_ON(atomic_read(&page_tail->_count) != 0);
1701                 /*
1702                  * tail_page->_count is zero and not changing from
1703                  * under us. But get_page_unless_zero() may be running
1704                  * from under us on the tail_page. If we used
1705                  * atomic_set() below instead of atomic_add(), we
1706                  * would then run atomic_set() concurrently with
1707                  * get_page_unless_zero(), and atomic_set() is
1708                  * implemented in C not using locked ops. spin_unlock
1709                  * on x86 sometime uses locked ops because of PPro
1710                  * errata 66, 92, so unless somebody can guarantee
1711                  * atomic_set() here would be safe on all archs (and
1712                  * not only on x86), it's safer to use atomic_add().
1713                  */
1714                 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1715                            &page_tail->_count);
1716
1717                 /* after clearing PageTail the gup refcount can be released */
1718                 smp_mb();
1719
1720                 /*
1721                  * retain hwpoison flag of the poisoned tail page:
1722                  *   fix for the unsuitable process killed on Guest Machine(KVM)
1723                  *   by the memory-failure.
1724                  */
1725                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1726                 page_tail->flags |= (page->flags &
1727                                      ((1L << PG_referenced) |
1728                                       (1L << PG_swapbacked) |
1729                                       (1L << PG_mlocked) |
1730                                       (1L << PG_uptodate) |
1731                                       (1L << PG_active) |
1732                                       (1L << PG_unevictable)));
1733                 page_tail->flags |= (1L << PG_dirty);
1734
1735                 /* clear PageTail before overwriting first_page */
1736                 smp_wmb();
1737
1738                 /*
1739                  * __split_huge_page_splitting() already set the
1740                  * splitting bit in all pmd that could map this
1741                  * hugepage, that will ensure no CPU can alter the
1742                  * mapcount on the head page. The mapcount is only
1743                  * accounted in the head page and it has to be
1744                  * transferred to all tail pages in the below code. So
1745                  * for this code to be safe, the split the mapcount
1746                  * can't change. But that doesn't mean userland can't
1747                  * keep changing and reading the page contents while
1748                  * we transfer the mapcount, so the pmd splitting
1749                  * status is achieved setting a reserved bit in the
1750                  * pmd, not by clearing the present bit.
1751                 */
1752                 page_tail->_mapcount = page->_mapcount;
1753
1754                 BUG_ON(page_tail->mapping);
1755                 page_tail->mapping = page->mapping;
1756
1757                 page_tail->index = page->index + i;
1758                 page_cpupid_xchg_last(page_tail, page_cpupid_last(page));
1759
1760                 BUG_ON(!PageAnon(page_tail));
1761                 BUG_ON(!PageUptodate(page_tail));
1762                 BUG_ON(!PageDirty(page_tail));
1763                 BUG_ON(!PageSwapBacked(page_tail));
1764
1765                 lru_add_page_tail(page, page_tail, lruvec, list);
1766         }
1767         atomic_sub(tail_count, &page->_count);
1768         BUG_ON(atomic_read(&page->_count) <= 0);
1769
1770         __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1771
1772         ClearPageCompound(page);
1773         compound_unlock(page);
1774         spin_unlock_irq(&zone->lru_lock);
1775
1776         for (i = 1; i < HPAGE_PMD_NR; i++) {
1777                 struct page *page_tail = page + i;
1778                 BUG_ON(page_count(page_tail) <= 0);
1779                 /*
1780                  * Tail pages may be freed if there wasn't any mapping
1781                  * like if add_to_swap() is running on a lru page that
1782                  * had its mapping zapped. And freeing these pages
1783                  * requires taking the lru_lock so we do the put_page
1784                  * of the tail pages after the split is complete.
1785                  */
1786                 put_page(page_tail);
1787         }
1788
1789         /*
1790          * Only the head page (now become a regular page) is required
1791          * to be pinned by the caller.
1792          */
1793         BUG_ON(page_count(page) <= 0);
1794 }
1795
1796 static int __split_huge_page_map(struct page *page,
1797                                  struct vm_area_struct *vma,
1798                                  unsigned long address)
1799 {
1800         struct mm_struct *mm = vma->vm_mm;
1801         spinlock_t *ptl;
1802         pmd_t *pmd, _pmd;
1803         int ret = 0, i;
1804         pgtable_t pgtable;
1805         unsigned long haddr;
1806
1807         pmd = page_check_address_pmd(page, mm, address,
1808                         PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl);
1809         if (pmd) {
1810                 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1811                 pmd_populate(mm, &_pmd, pgtable);
1812
1813                 haddr = address;
1814                 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1815                         pte_t *pte, entry;
1816                         BUG_ON(PageCompound(page+i));
1817                         entry = mk_pte(page + i, vma->vm_page_prot);
1818                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1819                         if (!pmd_write(*pmd))
1820                                 entry = pte_wrprotect(entry);
1821                         else
1822                                 BUG_ON(page_mapcount(page) != 1);
1823                         if (!pmd_young(*pmd))
1824                                 entry = pte_mkold(entry);
1825                         if (pmd_numa(*pmd))
1826                                 entry = pte_mknuma(entry);
1827                         pte = pte_offset_map(&_pmd, haddr);
1828                         BUG_ON(!pte_none(*pte));
1829                         set_pte_at(mm, haddr, pte, entry);
1830                         pte_unmap(pte);
1831                 }
1832
1833                 smp_wmb(); /* make pte visible before pmd */
1834                 /*
1835                  * Up to this point the pmd is present and huge and
1836                  * userland has the whole access to the hugepage
1837                  * during the split (which happens in place). If we
1838                  * overwrite the pmd with the not-huge version
1839                  * pointing to the pte here (which of course we could
1840                  * if all CPUs were bug free), userland could trigger
1841                  * a small page size TLB miss on the small sized TLB
1842                  * while the hugepage TLB entry is still established
1843                  * in the huge TLB. Some CPU doesn't like that. See
1844                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1845                  * Erratum 383 on page 93. Intel should be safe but is
1846                  * also warns that it's only safe if the permission
1847                  * and cache attributes of the two entries loaded in
1848                  * the two TLB is identical (which should be the case
1849                  * here). But it is generally safer to never allow
1850                  * small and huge TLB entries for the same virtual
1851                  * address to be loaded simultaneously. So instead of
1852                  * doing "pmd_populate(); flush_tlb_range();" we first
1853                  * mark the current pmd notpresent (atomically because
1854                  * here the pmd_trans_huge and pmd_trans_splitting
1855                  * must remain set at all times on the pmd until the
1856                  * split is complete for this pmd), then we flush the
1857                  * SMP TLB and finally we write the non-huge version
1858                  * of the pmd entry with pmd_populate.
1859                  */
1860                 pmdp_invalidate(vma, address, pmd);
1861                 pmd_populate(mm, pmd, pgtable);
1862                 ret = 1;
1863                 spin_unlock(ptl);
1864         }
1865
1866         return ret;
1867 }
1868
1869 /* must be called with anon_vma->root->rwsem held */
1870 static void __split_huge_page(struct page *page,
1871                               struct anon_vma *anon_vma,
1872                               struct list_head *list)
1873 {
1874         int mapcount, mapcount2;
1875         pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1876         struct anon_vma_chain *avc;
1877
1878         BUG_ON(!PageHead(page));
1879         BUG_ON(PageTail(page));
1880
1881         mapcount = 0;
1882         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1883                 struct vm_area_struct *vma = avc->vma;
1884                 unsigned long addr = vma_address(page, vma);
1885                 BUG_ON(is_vma_temporary_stack(vma));
1886                 mapcount += __split_huge_page_splitting(page, vma, addr);
1887         }
1888         /*
1889          * It is critical that new vmas are added to the tail of the
1890          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1891          * and establishes a child pmd before
1892          * __split_huge_page_splitting() freezes the parent pmd (so if
1893          * we fail to prevent copy_huge_pmd() from running until the
1894          * whole __split_huge_page() is complete), we will still see
1895          * the newly established pmd of the child later during the
1896          * walk, to be able to set it as pmd_trans_splitting too.
1897          */
1898         if (mapcount != page_mapcount(page))
1899                 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1900                        mapcount, page_mapcount(page));
1901         BUG_ON(mapcount != page_mapcount(page));
1902
1903         __split_huge_page_refcount(page, list);
1904
1905         mapcount2 = 0;
1906         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1907                 struct vm_area_struct *vma = avc->vma;
1908                 unsigned long addr = vma_address(page, vma);
1909                 BUG_ON(is_vma_temporary_stack(vma));
1910                 mapcount2 += __split_huge_page_map(page, vma, addr);
1911         }
1912         if (mapcount != mapcount2)
1913                 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1914                        mapcount, mapcount2, page_mapcount(page));
1915         BUG_ON(mapcount != mapcount2);
1916 }
1917
1918 /*
1919  * Split a hugepage into normal pages. This doesn't change the position of head
1920  * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1921  * @list. Both head page and tail pages will inherit mapping, flags, and so on
1922  * from the hugepage.
1923  * Return 0 if the hugepage is split successfully otherwise return 1.
1924  */
1925 int split_huge_page_to_list(struct page *page, struct list_head *list)
1926 {
1927         struct anon_vma *anon_vma;
1928         int ret = 1;
1929
1930         BUG_ON(is_huge_zero_page(page));
1931         BUG_ON(!PageAnon(page));
1932
1933         /*
1934          * The caller does not necessarily hold an mmap_sem that would prevent
1935          * the anon_vma disappearing so we first we take a reference to it
1936          * and then lock the anon_vma for write. This is similar to
1937          * page_lock_anon_vma_read except the write lock is taken to serialise
1938          * against parallel split or collapse operations.
1939          */
1940         anon_vma = page_get_anon_vma(page);
1941         if (!anon_vma)
1942                 goto out;
1943         anon_vma_lock_write(anon_vma);
1944
1945         ret = 0;
1946         if (!PageCompound(page))
1947                 goto out_unlock;
1948
1949         BUG_ON(!PageSwapBacked(page));
1950         __split_huge_page(page, anon_vma, list);
1951         count_vm_event(THP_SPLIT);
1952
1953         BUG_ON(PageCompound(page));
1954 out_unlock:
1955         anon_vma_unlock_write(anon_vma);
1956         put_anon_vma(anon_vma);
1957 out:
1958         return ret;
1959 }
1960
1961 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1962
1963 int hugepage_madvise(struct vm_area_struct *vma,
1964                      unsigned long *vm_flags, int advice)
1965 {
1966         struct mm_struct *mm = vma->vm_mm;
1967
1968         switch (advice) {
1969         case MADV_HUGEPAGE:
1970                 /*
1971                  * Be somewhat over-protective like KSM for now!
1972                  */
1973                 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1974                         return -EINVAL;
1975                 if (mm->def_flags & VM_NOHUGEPAGE)
1976                         return -EINVAL;
1977                 *vm_flags &= ~VM_NOHUGEPAGE;
1978                 *vm_flags |= VM_HUGEPAGE;
1979                 /*
1980                  * If the vma become good for khugepaged to scan,
1981                  * register it here without waiting a page fault that
1982                  * may not happen any time soon.
1983                  */
1984                 if (unlikely(khugepaged_enter_vma_merge(vma)))
1985                         return -ENOMEM;
1986                 break;
1987         case MADV_NOHUGEPAGE:
1988                 /*
1989                  * Be somewhat over-protective like KSM for now!
1990                  */
1991                 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1992                         return -EINVAL;
1993                 *vm_flags &= ~VM_HUGEPAGE;
1994                 *vm_flags |= VM_NOHUGEPAGE;
1995                 /*
1996                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1997                  * this vma even if we leave the mm registered in khugepaged if
1998                  * it got registered before VM_NOHUGEPAGE was set.
1999                  */
2000                 break;
2001         }
2002
2003         return 0;
2004 }
2005
2006 static int __init khugepaged_slab_init(void)
2007 {
2008         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
2009                                           sizeof(struct mm_slot),
2010                                           __alignof__(struct mm_slot), 0, NULL);
2011         if (!mm_slot_cache)
2012                 return -ENOMEM;
2013
2014         return 0;
2015 }
2016
2017 static inline struct mm_slot *alloc_mm_slot(void)
2018 {
2019         if (!mm_slot_cache)     /* initialization failed */
2020                 return NULL;
2021         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
2022 }
2023
2024 static inline void free_mm_slot(struct mm_slot *mm_slot)
2025 {
2026         kmem_cache_free(mm_slot_cache, mm_slot);
2027 }
2028
2029 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
2030 {
2031         struct mm_slot *mm_slot;
2032
2033         hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
2034                 if (mm == mm_slot->mm)
2035                         return mm_slot;
2036
2037         return NULL;
2038 }
2039
2040 static void insert_to_mm_slots_hash(struct mm_struct *mm,
2041                                     struct mm_slot *mm_slot)
2042 {
2043         mm_slot->mm = mm;
2044         hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
2045 }
2046
2047 static inline int khugepaged_test_exit(struct mm_struct *mm)
2048 {
2049         return atomic_read(&mm->mm_users) == 0;
2050 }
2051
2052 int __khugepaged_enter(struct mm_struct *mm)
2053 {
2054         struct mm_slot *mm_slot;
2055         int wakeup;
2056
2057         mm_slot = alloc_mm_slot();
2058         if (!mm_slot)
2059                 return -ENOMEM;
2060
2061         /* __khugepaged_exit() must not run from under us */
2062         VM_BUG_ON(khugepaged_test_exit(mm));
2063         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
2064                 free_mm_slot(mm_slot);
2065                 return 0;
2066         }
2067
2068         spin_lock(&khugepaged_mm_lock);
2069         insert_to_mm_slots_hash(mm, mm_slot);
2070         /*
2071          * Insert just behind the scanning cursor, to let the area settle
2072          * down a little.
2073          */
2074         wakeup = list_empty(&khugepaged_scan.mm_head);
2075         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
2076         spin_unlock(&khugepaged_mm_lock);
2077
2078         atomic_inc(&mm->mm_count);
2079         if (wakeup)
2080                 wake_up_interruptible(&khugepaged_wait);
2081
2082         return 0;
2083 }
2084
2085 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
2086 {
2087         unsigned long hstart, hend;
2088         if (!vma->anon_vma)
2089                 /*
2090                  * Not yet faulted in so we will register later in the
2091                  * page fault if needed.
2092                  */
2093                 return 0;
2094         if (vma->vm_ops)
2095                 /* khugepaged not yet working on file or special mappings */
2096                 return 0;
2097         VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2098         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2099         hend = vma->vm_end & HPAGE_PMD_MASK;
2100         if (hstart < hend)
2101                 return khugepaged_enter(vma);
2102         return 0;
2103 }
2104
2105 void __khugepaged_exit(struct mm_struct *mm)
2106 {
2107         struct mm_slot *mm_slot;
2108         int free = 0;
2109
2110         spin_lock(&khugepaged_mm_lock);
2111         mm_slot = get_mm_slot(mm);
2112         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2113                 hash_del(&mm_slot->hash);
2114                 list_del(&mm_slot->mm_node);
2115                 free = 1;
2116         }
2117         spin_unlock(&khugepaged_mm_lock);
2118
2119         if (free) {
2120                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2121                 free_mm_slot(mm_slot);
2122                 mmdrop(mm);
2123         } else if (mm_slot) {
2124                 /*
2125                  * This is required to serialize against
2126                  * khugepaged_test_exit() (which is guaranteed to run
2127                  * under mmap sem read mode). Stop here (after we
2128                  * return all pagetables will be destroyed) until
2129                  * khugepaged has finished working on the pagetables
2130                  * under the mmap_sem.
2131                  */
2132                 down_write(&mm->mmap_sem);
2133                 up_write(&mm->mmap_sem);
2134         }
2135 }
2136
2137 static void release_pte_page(struct page *page)
2138 {
2139         /* 0 stands for page_is_file_cache(page) == false */
2140         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2141         unlock_page(page);
2142         putback_lru_page(page);
2143 }
2144
2145 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2146 {
2147         while (--_pte >= pte) {
2148                 pte_t pteval = *_pte;
2149                 if (!pte_none(pteval))
2150                         release_pte_page(pte_page(pteval));
2151         }
2152 }
2153
2154 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2155                                         unsigned long address,
2156                                         pte_t *pte)
2157 {
2158         struct page *page;
2159         pte_t *_pte;
2160         int referenced = 0, none = 0;
2161         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2162              _pte++, address += PAGE_SIZE) {
2163                 pte_t pteval = *_pte;
2164                 if (pte_none(pteval)) {
2165                         if (++none <= khugepaged_max_ptes_none)
2166                                 continue;
2167                         else
2168                                 goto out;
2169                 }
2170                 if (!pte_present(pteval) || !pte_write(pteval))
2171                         goto out;
2172                 page = vm_normal_page(vma, address, pteval);
2173                 if (unlikely(!page))
2174                         goto out;
2175
2176                 VM_BUG_ON_PAGE(PageCompound(page), page);
2177                 VM_BUG_ON_PAGE(!PageAnon(page), page);
2178                 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2179
2180                 /* cannot use mapcount: can't collapse if there's a gup pin */
2181                 if (page_count(page) != 1)
2182                         goto out;
2183                 /*
2184                  * We can do it before isolate_lru_page because the
2185                  * page can't be freed from under us. NOTE: PG_lock
2186                  * is needed to serialize against split_huge_page
2187                  * when invoked from the VM.
2188                  */
2189                 if (!trylock_page(page))
2190                         goto out;
2191                 /*
2192                  * Isolate the page to avoid collapsing an hugepage
2193                  * currently in use by the VM.
2194                  */
2195                 if (isolate_lru_page(page)) {
2196                         unlock_page(page);
2197                         goto out;
2198                 }
2199                 /* 0 stands for page_is_file_cache(page) == false */
2200                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2201                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2202                 VM_BUG_ON_PAGE(PageLRU(page), page);
2203
2204                 /* If there is no mapped pte young don't collapse the page */
2205                 if (pte_young(pteval) || PageReferenced(page) ||
2206                     mmu_notifier_test_young(vma->vm_mm, address))
2207                         referenced = 1;
2208         }
2209         if (likely(referenced))
2210                 return 1;
2211 out:
2212         release_pte_pages(pte, _pte);
2213         return 0;
2214 }
2215
2216 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2217                                       struct vm_area_struct *vma,
2218                                       unsigned long address,
2219                                       spinlock_t *ptl)
2220 {
2221         pte_t *_pte;
2222         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2223                 pte_t pteval = *_pte;
2224                 struct page *src_page;
2225
2226                 if (pte_none(pteval)) {
2227                         clear_user_highpage(page, address);
2228                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2229                 } else {
2230                         src_page = pte_page(pteval);
2231                         copy_user_highpage(page, src_page, address, vma);
2232                         VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2233                         release_pte_page(src_page);
2234                         /*
2235                          * ptl mostly unnecessary, but preempt has to
2236                          * be disabled to update the per-cpu stats
2237                          * inside page_remove_rmap().
2238                          */
2239                         spin_lock(ptl);
2240                         /*
2241                          * paravirt calls inside pte_clear here are
2242                          * superfluous.
2243                          */
2244                         pte_clear(vma->vm_mm, address, _pte);
2245                         page_remove_rmap(src_page);
2246                         spin_unlock(ptl);
2247                         free_page_and_swap_cache(src_page);
2248                 }
2249
2250                 address += PAGE_SIZE;
2251                 page++;
2252         }
2253 }
2254
2255 static void khugepaged_alloc_sleep(void)
2256 {
2257         wait_event_freezable_timeout(khugepaged_wait, false,
2258                         msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2259 }
2260
2261 static int khugepaged_node_load[MAX_NUMNODES];
2262
2263 #ifdef CONFIG_NUMA
2264 static int khugepaged_find_target_node(void)
2265 {
2266         static int last_khugepaged_target_node = NUMA_NO_NODE;
2267         int nid, target_node = 0, max_value = 0;
2268
2269         /* find first node with max normal pages hit */
2270         for (nid = 0; nid < MAX_NUMNODES; nid++)
2271                 if (khugepaged_node_load[nid] > max_value) {
2272                         max_value = khugepaged_node_load[nid];
2273                         target_node = nid;
2274                 }
2275
2276         /* do some balance if several nodes have the same hit record */
2277         if (target_node <= last_khugepaged_target_node)
2278                 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2279                                 nid++)
2280                         if (max_value == khugepaged_node_load[nid]) {
2281                                 target_node = nid;
2282                                 break;
2283                         }
2284
2285         last_khugepaged_target_node = target_node;
2286         return target_node;
2287 }
2288
2289 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2290 {
2291         if (IS_ERR(*hpage)) {
2292                 if (!*wait)
2293                         return false;
2294
2295                 *wait = false;
2296                 *hpage = NULL;
2297                 khugepaged_alloc_sleep();
2298         } else if (*hpage) {
2299                 put_page(*hpage);
2300                 *hpage = NULL;
2301         }
2302
2303         return true;
2304 }
2305
2306 static struct page
2307 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2308                        struct vm_area_struct *vma, unsigned long address,
2309                        int node)
2310 {
2311         VM_BUG_ON_PAGE(*hpage, *hpage);
2312         /*
2313          * Allocate the page while the vma is still valid and under
2314          * the mmap_sem read mode so there is no memory allocation
2315          * later when we take the mmap_sem in write mode. This is more
2316          * friendly behavior (OTOH it may actually hide bugs) to
2317          * filesystems in userland with daemons allocating memory in
2318          * the userland I/O paths.  Allocating memory with the
2319          * mmap_sem in read mode is good idea also to allow greater
2320          * scalability.
2321          */
2322         *hpage = alloc_pages_exact_node(node, alloc_hugepage_gfpmask(
2323                 khugepaged_defrag(), __GFP_OTHER_NODE), HPAGE_PMD_ORDER);
2324         /*
2325          * After allocating the hugepage, release the mmap_sem read lock in
2326          * preparation for taking it in write mode.
2327          */
2328         up_read(&mm->mmap_sem);
2329         if (unlikely(!*hpage)) {
2330                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2331                 *hpage = ERR_PTR(-ENOMEM);
2332                 return NULL;
2333         }
2334
2335         count_vm_event(THP_COLLAPSE_ALLOC);
2336         return *hpage;
2337 }
2338 #else
2339 static int khugepaged_find_target_node(void)
2340 {
2341         return 0;
2342 }
2343
2344 static inline struct page *alloc_hugepage(int defrag)
2345 {
2346         return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
2347                            HPAGE_PMD_ORDER);
2348 }
2349
2350 static struct page *khugepaged_alloc_hugepage(bool *wait)
2351 {
2352         struct page *hpage;
2353
2354         do {
2355                 hpage = alloc_hugepage(khugepaged_defrag());
2356                 if (!hpage) {
2357                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2358                         if (!*wait)
2359                                 return NULL;
2360
2361                         *wait = false;
2362                         khugepaged_alloc_sleep();
2363                 } else
2364                         count_vm_event(THP_COLLAPSE_ALLOC);
2365         } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2366
2367         return hpage;
2368 }
2369
2370 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2371 {
2372         if (!*hpage)
2373                 *hpage = khugepaged_alloc_hugepage(wait);
2374
2375         if (unlikely(!*hpage))
2376                 return false;
2377
2378         return true;
2379 }
2380
2381 static struct page
2382 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2383                        struct vm_area_struct *vma, unsigned long address,
2384                        int node)
2385 {
2386         up_read(&mm->mmap_sem);
2387         VM_BUG_ON(!*hpage);
2388         return  *hpage;
2389 }
2390 #endif
2391
2392 static bool hugepage_vma_check(struct vm_area_struct *vma)
2393 {
2394         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2395             (vma->vm_flags & VM_NOHUGEPAGE))
2396                 return false;
2397
2398         if (!vma->anon_vma || vma->vm_ops)
2399                 return false;
2400         if (is_vma_temporary_stack(vma))
2401                 return false;
2402         VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2403         return true;
2404 }
2405
2406 static void collapse_huge_page(struct mm_struct *mm,
2407                                    unsigned long address,
2408                                    struct page **hpage,
2409                                    struct vm_area_struct *vma,
2410                                    int node)
2411 {
2412         pmd_t *pmd, _pmd;
2413         pte_t *pte;
2414         pgtable_t pgtable;
2415         struct page *new_page;
2416         spinlock_t *pmd_ptl, *pte_ptl;
2417         int isolated;
2418         unsigned long hstart, hend;
2419         unsigned long mmun_start;       /* For mmu_notifiers */
2420         unsigned long mmun_end;         /* For mmu_notifiers */
2421
2422         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2423
2424         /* release the mmap_sem read lock. */
2425         new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2426         if (!new_page)
2427                 return;
2428
2429         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2430                 return;
2431
2432         /*
2433          * Prevent all access to pagetables with the exception of
2434          * gup_fast later hanlded by the ptep_clear_flush and the VM
2435          * handled by the anon_vma lock + PG_lock.
2436          */
2437         down_write(&mm->mmap_sem);
2438         if (unlikely(khugepaged_test_exit(mm)))
2439                 goto out;
2440
2441         vma = find_vma(mm, address);
2442         if (!vma)
2443                 goto out;
2444         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2445         hend = vma->vm_end & HPAGE_PMD_MASK;
2446         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2447                 goto out;
2448         if (!hugepage_vma_check(vma))
2449                 goto out;
2450         pmd = mm_find_pmd(mm, address);
2451         if (!pmd)
2452                 goto out;
2453         if (pmd_trans_huge(*pmd))
2454                 goto out;
2455
2456         anon_vma_lock_write(vma->anon_vma);
2457
2458         pte = pte_offset_map(pmd, address);
2459         pte_ptl = pte_lockptr(mm, pmd);
2460
2461         mmun_start = address;
2462         mmun_end   = address + HPAGE_PMD_SIZE;
2463         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2464         pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2465         /*
2466          * After this gup_fast can't run anymore. This also removes
2467          * any huge TLB entry from the CPU so we won't allow
2468          * huge and small TLB entries for the same virtual address
2469          * to avoid the risk of CPU bugs in that area.
2470          */
2471         _pmd = pmdp_clear_flush(vma, address, pmd);
2472         spin_unlock(pmd_ptl);
2473         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2474
2475         spin_lock(pte_ptl);
2476         isolated = __collapse_huge_page_isolate(vma, address, pte);
2477         spin_unlock(pte_ptl);
2478
2479         if (unlikely(!isolated)) {
2480                 pte_unmap(pte);
2481                 spin_lock(pmd_ptl);
2482                 BUG_ON(!pmd_none(*pmd));
2483                 /*
2484                  * We can only use set_pmd_at when establishing
2485                  * hugepmds and never for establishing regular pmds that
2486                  * points to regular pagetables. Use pmd_populate for that
2487                  */
2488                 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2489                 spin_unlock(pmd_ptl);
2490                 anon_vma_unlock_write(vma->anon_vma);
2491                 goto out;
2492         }
2493
2494         /*
2495          * All pages are isolated and locked so anon_vma rmap
2496          * can't run anymore.
2497          */
2498         anon_vma_unlock_write(vma->anon_vma);
2499
2500         __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2501         pte_unmap(pte);
2502         __SetPageUptodate(new_page);
2503         pgtable = pmd_pgtable(_pmd);
2504
2505         _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2506         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2507
2508         /*
2509          * spin_lock() below is not the equivalent of smp_wmb(), so
2510          * this is needed to avoid the copy_huge_page writes to become
2511          * visible after the set_pmd_at() write.
2512          */
2513         smp_wmb();
2514
2515         spin_lock(pmd_ptl);
2516         BUG_ON(!pmd_none(*pmd));
2517         page_add_new_anon_rmap(new_page, vma, address);
2518         pgtable_trans_huge_deposit(mm, pmd, pgtable);
2519         set_pmd_at(mm, address, pmd, _pmd);
2520         update_mmu_cache_pmd(vma, address, pmd);
2521         spin_unlock(pmd_ptl);
2522
2523         *hpage = NULL;
2524
2525         khugepaged_pages_collapsed++;
2526 out_up_write:
2527         up_write(&mm->mmap_sem);
2528         return;
2529
2530 out:
2531         mem_cgroup_uncharge_page(new_page);
2532         goto out_up_write;
2533 }
2534
2535 static int khugepaged_scan_pmd(struct mm_struct *mm,
2536                                struct vm_area_struct *vma,
2537                                unsigned long address,
2538                                struct page **hpage)
2539 {
2540         pmd_t *pmd;
2541         pte_t *pte, *_pte;
2542         int ret = 0, referenced = 0, none = 0;
2543         struct page *page;
2544         unsigned long _address;
2545         spinlock_t *ptl;
2546         int node = NUMA_NO_NODE;
2547
2548         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2549
2550         pmd = mm_find_pmd(mm, address);
2551         if (!pmd)
2552                 goto out;
2553         if (pmd_trans_huge(*pmd))
2554                 goto out;
2555
2556         memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2557         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2558         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2559              _pte++, _address += PAGE_SIZE) {
2560                 pte_t pteval = *_pte;
2561                 if (pte_none(pteval)) {
2562                         if (++none <= khugepaged_max_ptes_none)
2563                                 continue;
2564                         else
2565                                 goto out_unmap;
2566                 }
2567                 if (!pte_present(pteval) || !pte_write(pteval))
2568                         goto out_unmap;
2569                 page = vm_normal_page(vma, _address, pteval);
2570                 if (unlikely(!page))
2571                         goto out_unmap;
2572                 /*
2573                  * Record which node the original page is from and save this
2574                  * information to khugepaged_node_load[].
2575                  * Khupaged will allocate hugepage from the node has the max
2576                  * hit record.
2577                  */
2578                 node = page_to_nid(page);
2579                 khugepaged_node_load[node]++;
2580                 VM_BUG_ON_PAGE(PageCompound(page), page);
2581                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2582                         goto out_unmap;
2583                 /* cannot use mapcount: can't collapse if there's a gup pin */
2584                 if (page_count(page) != 1)
2585                         goto out_unmap;
2586                 if (pte_young(pteval) || PageReferenced(page) ||
2587                     mmu_notifier_test_young(vma->vm_mm, address))
2588                         referenced = 1;
2589         }
2590         if (referenced)
2591                 ret = 1;
2592 out_unmap:
2593         pte_unmap_unlock(pte, ptl);
2594         if (ret) {
2595                 node = khugepaged_find_target_node();
2596                 /* collapse_huge_page will return with the mmap_sem released */
2597                 collapse_huge_page(mm, address, hpage, vma, node);
2598         }
2599 out:
2600         return ret;
2601 }
2602
2603 static void collect_mm_slot(struct mm_slot *mm_slot)
2604 {
2605         struct mm_struct *mm = mm_slot->mm;
2606
2607         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2608
2609         if (khugepaged_test_exit(mm)) {
2610                 /* free mm_slot */
2611                 hash_del(&mm_slot->hash);
2612                 list_del(&mm_slot->mm_node);
2613
2614                 /*
2615                  * Not strictly needed because the mm exited already.
2616                  *
2617                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2618                  */
2619
2620                 /* khugepaged_mm_lock actually not necessary for the below */
2621                 free_mm_slot(mm_slot);
2622                 mmdrop(mm);
2623         }
2624 }
2625
2626 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2627                                             struct page **hpage)
2628         __releases(&khugepaged_mm_lock)
2629         __acquires(&khugepaged_mm_lock)
2630 {
2631         struct mm_slot *mm_slot;
2632         struct mm_struct *mm;
2633         struct vm_area_struct *vma;
2634         int progress = 0;
2635
2636         VM_BUG_ON(!pages);
2637         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2638
2639         if (khugepaged_scan.mm_slot)
2640                 mm_slot = khugepaged_scan.mm_slot;
2641         else {
2642                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2643                                      struct mm_slot, mm_node);
2644                 khugepaged_scan.address = 0;
2645                 khugepaged_scan.mm_slot = mm_slot;
2646         }
2647         spin_unlock(&khugepaged_mm_lock);
2648
2649         mm = mm_slot->mm;
2650         down_read(&mm->mmap_sem);
2651         if (unlikely(khugepaged_test_exit(mm)))
2652                 vma = NULL;
2653         else
2654                 vma = find_vma(mm, khugepaged_scan.address);
2655
2656         progress++;
2657         for (; vma; vma = vma->vm_next) {
2658                 unsigned long hstart, hend;
2659
2660                 cond_resched();
2661                 if (unlikely(khugepaged_test_exit(mm))) {
2662                         progress++;
2663                         break;
2664                 }
2665                 if (!hugepage_vma_check(vma)) {
2666 skip:
2667                         progress++;
2668                         continue;
2669                 }
2670                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2671                 hend = vma->vm_end & HPAGE_PMD_MASK;
2672                 if (hstart >= hend)
2673                         goto skip;
2674                 if (khugepaged_scan.address > hend)
2675                         goto skip;
2676                 if (khugepaged_scan.address < hstart)
2677                         khugepaged_scan.address = hstart;
2678                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2679
2680                 while (khugepaged_scan.address < hend) {
2681                         int ret;
2682                         cond_resched();
2683                         if (unlikely(khugepaged_test_exit(mm)))
2684                                 goto breakouterloop;
2685
2686                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2687                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2688                                   hend);
2689                         ret = khugepaged_scan_pmd(mm, vma,
2690                                                   khugepaged_scan.address,
2691                                                   hpage);
2692                         /* move to next address */
2693                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2694                         progress += HPAGE_PMD_NR;
2695                         if (ret)
2696                                 /* we released mmap_sem so break loop */
2697                                 goto breakouterloop_mmap_sem;
2698                         if (progress >= pages)
2699                                 goto breakouterloop;
2700                 }
2701         }
2702 breakouterloop:
2703         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2704 breakouterloop_mmap_sem:
2705
2706         spin_lock(&khugepaged_mm_lock);
2707         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2708         /*
2709          * Release the current mm_slot if this mm is about to die, or
2710          * if we scanned all vmas of this mm.
2711          */
2712         if (khugepaged_test_exit(mm) || !vma) {
2713                 /*
2714                  * Make sure that if mm_users is reaching zero while
2715                  * khugepaged runs here, khugepaged_exit will find
2716                  * mm_slot not pointing to the exiting mm.
2717                  */
2718                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2719                         khugepaged_scan.mm_slot = list_entry(
2720                                 mm_slot->mm_node.next,
2721                                 struct mm_slot, mm_node);
2722                         khugepaged_scan.address = 0;
2723                 } else {
2724                         khugepaged_scan.mm_slot = NULL;
2725                         khugepaged_full_scans++;
2726                 }
2727
2728                 collect_mm_slot(mm_slot);
2729         }
2730
2731         return progress;
2732 }
2733
2734 static int khugepaged_has_work(void)
2735 {
2736         return !list_empty(&khugepaged_scan.mm_head) &&
2737                 khugepaged_enabled();
2738 }
2739
2740 static int khugepaged_wait_event(void)
2741 {
2742         return !list_empty(&khugepaged_scan.mm_head) ||
2743                 kthread_should_stop();
2744 }
2745
2746 static void khugepaged_do_scan(void)
2747 {
2748         struct page *hpage = NULL;
2749         unsigned int progress = 0, pass_through_head = 0;
2750         unsigned int pages = khugepaged_pages_to_scan;
2751         bool wait = true;
2752
2753         barrier(); /* write khugepaged_pages_to_scan to local stack */
2754
2755         while (progress < pages) {
2756                 if (!khugepaged_prealloc_page(&hpage, &wait))
2757                         break;
2758
2759                 cond_resched();
2760
2761                 if (unlikely(kthread_should_stop() || freezing(current)))
2762                         break;
2763
2764                 spin_lock(&khugepaged_mm_lock);
2765                 if (!khugepaged_scan.mm_slot)
2766                         pass_through_head++;
2767                 if (khugepaged_has_work() &&
2768                     pass_through_head < 2)
2769                         progress += khugepaged_scan_mm_slot(pages - progress,
2770                                                             &hpage);
2771                 else
2772                         progress = pages;
2773                 spin_unlock(&khugepaged_mm_lock);
2774         }
2775
2776         if (!IS_ERR_OR_NULL(hpage))
2777                 put_page(hpage);
2778 }
2779
2780 static void khugepaged_wait_work(void)
2781 {
2782         try_to_freeze();
2783
2784         if (khugepaged_has_work()) {
2785                 if (!khugepaged_scan_sleep_millisecs)
2786                         return;
2787
2788                 wait_event_freezable_timeout(khugepaged_wait,
2789                                              kthread_should_stop(),
2790                         msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2791                 return;
2792         }
2793
2794         if (khugepaged_enabled())
2795                 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2796 }
2797
2798 static int khugepaged(void *none)
2799 {
2800         struct mm_slot *mm_slot;
2801
2802         set_freezable();
2803         set_user_nice(current, 19);
2804
2805         while (!kthread_should_stop()) {
2806                 khugepaged_do_scan();
2807                 khugepaged_wait_work();
2808         }
2809
2810         spin_lock(&khugepaged_mm_lock);
2811         mm_slot = khugepaged_scan.mm_slot;
2812         khugepaged_scan.mm_slot = NULL;
2813         if (mm_slot)
2814                 collect_mm_slot(mm_slot);
2815         spin_unlock(&khugepaged_mm_lock);
2816         return 0;
2817 }
2818
2819 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2820                 unsigned long haddr, pmd_t *pmd)
2821 {
2822         struct mm_struct *mm = vma->vm_mm;
2823         pgtable_t pgtable;
2824         pmd_t _pmd;
2825         int i;
2826
2827         pmdp_clear_flush(vma, haddr, pmd);
2828         /* leave pmd empty until pte is filled */
2829
2830         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2831         pmd_populate(mm, &_pmd, pgtable);
2832
2833         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2834                 pte_t *pte, entry;
2835                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2836                 entry = pte_mkspecial(entry);
2837                 pte = pte_offset_map(&_pmd, haddr);
2838                 VM_BUG_ON(!pte_none(*pte));
2839                 set_pte_at(mm, haddr, pte, entry);
2840                 pte_unmap(pte);
2841         }
2842         smp_wmb(); /* make pte visible before pmd */
2843         pmd_populate(mm, pmd, pgtable);
2844         put_huge_zero_page();
2845 }
2846
2847 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2848                 pmd_t *pmd)
2849 {
2850         spinlock_t *ptl;
2851         struct page *page;
2852         struct mm_struct *mm = vma->vm_mm;
2853         unsigned long haddr = address & HPAGE_PMD_MASK;
2854         unsigned long mmun_start;       /* For mmu_notifiers */
2855         unsigned long mmun_end;         /* For mmu_notifiers */
2856
2857         BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2858
2859         mmun_start = haddr;
2860         mmun_end   = haddr + HPAGE_PMD_SIZE;
2861 again:
2862         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2863         ptl = pmd_lock(mm, pmd);
2864         if (unlikely(!pmd_trans_huge(*pmd))) {
2865                 spin_unlock(ptl);
2866                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2867                 return;
2868         }
2869         if (is_huge_zero_pmd(*pmd)) {
2870                 __split_huge_zero_page_pmd(vma, haddr, pmd);
2871                 spin_unlock(ptl);
2872                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2873                 return;
2874         }
2875         page = pmd_page(*pmd);
2876         VM_BUG_ON_PAGE(!page_count(page), page);
2877         get_page(page);
2878         spin_unlock(ptl);
2879         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2880
2881         split_huge_page(page);
2882
2883         put_page(page);
2884
2885         /*
2886          * We don't always have down_write of mmap_sem here: a racing
2887          * do_huge_pmd_wp_page() might have copied-on-write to another
2888          * huge page before our split_huge_page() got the anon_vma lock.
2889          */
2890         if (unlikely(pmd_trans_huge(*pmd)))
2891                 goto again;
2892 }
2893
2894 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2895                 pmd_t *pmd)
2896 {
2897         struct vm_area_struct *vma;
2898
2899         vma = find_vma(mm, address);
2900         BUG_ON(vma == NULL);
2901         split_huge_page_pmd(vma, address, pmd);
2902 }
2903
2904 static void split_huge_page_address(struct mm_struct *mm,
2905                                     unsigned long address)
2906 {
2907         pmd_t *pmd;
2908
2909         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2910
2911         pmd = mm_find_pmd(mm, address);
2912         if (!pmd)
2913                 return;
2914         /*
2915          * Caller holds the mmap_sem write mode, so a huge pmd cannot
2916          * materialize from under us.
2917          */
2918         split_huge_page_pmd_mm(mm, address, pmd);
2919 }
2920
2921 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2922                              unsigned long start,
2923                              unsigned long end,
2924                              long adjust_next)
2925 {
2926         /*
2927          * If the new start address isn't hpage aligned and it could
2928          * previously contain an hugepage: check if we need to split
2929          * an huge pmd.
2930          */
2931         if (start & ~HPAGE_PMD_MASK &&
2932             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2933             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2934                 split_huge_page_address(vma->vm_mm, start);
2935
2936         /*
2937          * If the new end address isn't hpage aligned and it could
2938          * previously contain an hugepage: check if we need to split
2939          * an huge pmd.
2940          */
2941         if (end & ~HPAGE_PMD_MASK &&
2942             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2943             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2944                 split_huge_page_address(vma->vm_mm, end);
2945
2946         /*
2947          * If we're also updating the vma->vm_next->vm_start, if the new
2948          * vm_next->vm_start isn't page aligned and it could previously
2949          * contain an hugepage: check if we need to split an huge pmd.
2950          */
2951         if (adjust_next > 0) {
2952                 struct vm_area_struct *next = vma->vm_next;
2953                 unsigned long nstart = next->vm_start;
2954                 nstart += adjust_next << PAGE_SHIFT;
2955                 if (nstart & ~HPAGE_PMD_MASK &&
2956                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2957                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2958                         split_huge_page_address(next->vm_mm, nstart);
2959         }
2960 }