Pileus Git - ~andy/linux/blob - mm/huge_memory.c

   1 /*
   2  *  Copyright (C) 2009  Red Hat, Inc.
   3  *
   4  *  This work is licensed under the terms of the GNU GPL, version 2. See
   5  *  the COPYING file in the top-level directory.
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/sched.h>
  10 #include <linux/highmem.h>
  11 #include <linux/hugetlb.h>
  12 #include <linux/mmu_notifier.h>
  13 #include <linux/rmap.h>
  14 #include <linux/swap.h>
  15 #include <linux/mm_inline.h>
  16 #include <linux/kthread.h>
  17 #include <linux/khugepaged.h>
  18 #include <linux/freezer.h>
  19 #include <linux/mman.h>
  20 #include <asm/tlb.h>
  21 #include <asm/pgalloc.h>
  22 #include "internal.h"
  23
  24 /*
  25  * By default transparent hugepage support is enabled for all mappings
  26  * and khugepaged scans all mappings. Defrag is only invoked by
  27  * khugepaged hugepage allocations and by page faults inside
  28  * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
  29  * allocations.
  30  */
  31 unsigned long transparent_hugepage_flags __read_mostly =
  32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  33         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  34 #endif
  35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  36         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  37 #endif
  38         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
  39         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
  40
  41 /* default scan 8*512 pte (or vmas) every 30 second */
  42 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
  43 static unsigned int khugepaged_pages_collapsed;
  44 static unsigned int khugepaged_full_scans;
  45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  46 /* during fragmentation poll the hugepage allocator once every minute */
  47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  48 static struct task_struct *khugepaged_thread __read_mostly;
  49 static DEFINE_MUTEX(khugepaged_mutex);
  50 static DEFINE_SPINLOCK(khugepaged_mm_lock);
  51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  52 /*
  53  * default collapse hugepages if there is at least one pte mapped like
  54  * it would have happened if the vma was large enough during page
  55  * fault.
  56  */
  57 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
  58
  59 static int khugepaged(void *none);
  60 static int mm_slots_hash_init(void);
  61 static int khugepaged_slab_init(void);
  62 static void khugepaged_slab_free(void);
  63
  64 #define MM_SLOTS_HASH_HEADS 1024
  65 static struct hlist_head *mm_slots_hash __read_mostly;
  66 static struct kmem_cache *mm_slot_cache __read_mostly;
  67
  68 /**
  69  * struct mm_slot - hash lookup from mm to mm_slot
  70  * @hash: hash collision list
  71  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
  72  * @mm: the mm that this information is valid for
  73  */
  74 struct mm_slot {
  75         struct hlist_node hash;
  76         struct list_head mm_node;
  77         struct mm_struct *mm;
  78 };
  79
  80 /**
  81  * struct khugepaged_scan - cursor for scanning
  82  * @mm_head: the head of the mm list to scan
  83  * @mm_slot: the current mm_slot we are scanning
  84  * @address: the next address inside that to be scanned
  85  *
  86  * There is only the one khugepaged_scan instance of this cursor structure.
  87  */
  88 struct khugepaged_scan {
  89         struct list_head mm_head;
  90         struct mm_slot *mm_slot;
  91         unsigned long address;
  92 };
  93 static struct khugepaged_scan khugepaged_scan = {
  94         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
  95 };
  96
  97
  98 static int set_recommended_min_free_kbytes(void)
  99 {
 100         struct zone *zone;
 101         int nr_zones = 0;
 102         unsigned long recommended_min;
 103         extern int min_free_kbytes;
 104
 105         if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
 106                       &transparent_hugepage_flags) &&
 107             !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 108                       &transparent_hugepage_flags))
 109                 return 0;
 110
 111         for_each_populated_zone(zone)
 112                 nr_zones++;
 113
 114         /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
 115         recommended_min = pageblock_nr_pages * nr_zones * 2;
 116
 117         /*
 118          * Make sure that on average at least two pageblocks are almost free
 119          * of another type, one for a migratetype to fall back to and a
 120          * second to avoid subsequent fallbacks of other types There are 3
 121          * MIGRATE_TYPES we care about.
 122          */
 123         recommended_min += pageblock_nr_pages * nr_zones *
 124                            MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
 125
 126         /* don't ever allow to reserve more than 5% of the lowmem */
 127         recommended_min = min(recommended_min,
 128                               (unsigned long) nr_free_buffer_pages() / 20);
 129         recommended_min <<= (PAGE_SHIFT-10);
 130
 131         if (recommended_min > min_free_kbytes)
 132                 min_free_kbytes = recommended_min;
 133         setup_per_zone_wmarks();
 134         return 0;
 135 }
 136 late_initcall(set_recommended_min_free_kbytes);
 137
 138 static int start_khugepaged(void)
 139 {
 140         int err = 0;
 141         if (khugepaged_enabled()) {
 142                 if (!khugepaged_thread)
 143                         khugepaged_thread = kthread_run(khugepaged, NULL,
 144                                                         "khugepaged");
 145                 if (unlikely(IS_ERR(khugepaged_thread))) {
 146                         printk(KERN_ERR
 147                                "khugepaged: kthread_run(khugepaged) failed\n");
 148                         err = PTR_ERR(khugepaged_thread);
 149                         khugepaged_thread = NULL;
 150                 }
 151
 152                 if (!list_empty(&khugepaged_scan.mm_head))
 153                         wake_up_interruptible(&khugepaged_wait);
 154
 155                 set_recommended_min_free_kbytes();
 156         } else if (khugepaged_thread) {
 157                 kthread_stop(khugepaged_thread);
 158                 khugepaged_thread = NULL;
 159         }
 160
 161         return err;
 162 }
 163
 164 #ifdef CONFIG_SYSFS
 165
 166 static ssize_t double_flag_show(struct kobject *kobj,
 167                                 struct kobj_attribute *attr, char *buf,
 168                                 enum transparent_hugepage_flag enabled,
 169                                 enum transparent_hugepage_flag req_madv)
 170 {
 171         if (test_bit(enabled, &transparent_hugepage_flags)) {
 172                 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
 173                 return sprintf(buf, "[always] madvise never\n");
 174         } else if (test_bit(req_madv, &transparent_hugepage_flags))
 175                 return sprintf(buf, "always [madvise] never\n");
 176         else
 177                 return sprintf(buf, "always madvise [never]\n");
 178 }
 179 static ssize_t double_flag_store(struct kobject *kobj,
 180                                  struct kobj_attribute *attr,
 181                                  const char *buf, size_t count,
 182                                  enum transparent_hugepage_flag enabled,
 183                                  enum transparent_hugepage_flag req_madv)
 184 {
 185         if (!memcmp("always", buf,
 186                     min(sizeof("always")-1, count))) {
 187                 set_bit(enabled, &transparent_hugepage_flags);
 188                 clear_bit(req_madv, &transparent_hugepage_flags);
 189         } else if (!memcmp("madvise", buf,
 190                            min(sizeof("madvise")-1, count))) {
 191                 clear_bit(enabled, &transparent_hugepage_flags);
 192                 set_bit(req_madv, &transparent_hugepage_flags);
 193         } else if (!memcmp("never", buf,
 194                            min(sizeof("never")-1, count))) {
 195                 clear_bit(enabled, &transparent_hugepage_flags);
 196                 clear_bit(req_madv, &transparent_hugepage_flags);
 197         } else
 198                 return -EINVAL;
 199
 200         return count;
 201 }
 202
 203 static ssize_t enabled_show(struct kobject *kobj,
 204                             struct kobj_attribute *attr, char *buf)
 205 {
 206         return double_flag_show(kobj, attr, buf,
 207                                 TRANSPARENT_HUGEPAGE_FLAG,
 208                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 209 }
 210 static ssize_t enabled_store(struct kobject *kobj,
 211                              struct kobj_attribute *attr,
 212                              const char *buf, size_t count)
 213 {
 214         ssize_t ret;
 215
 216         ret = double_flag_store(kobj, attr, buf, count,
 217                                 TRANSPARENT_HUGEPAGE_FLAG,
 218                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 219
 220         if (ret > 0) {
 221                 int err;
 222
 223                 mutex_lock(&khugepaged_mutex);
 224                 err = start_khugepaged();
 225                 mutex_unlock(&khugepaged_mutex);
 226
 227                 if (err)
 228                         ret = err;
 229         }
 230
 231         if (ret > 0 &&
 232             (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
 233                       &transparent_hugepage_flags) ||
 234              test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 235                       &transparent_hugepage_flags)))
 236                 set_recommended_min_free_kbytes();
 237
 238         return ret;
 239 }
 240 static struct kobj_attribute enabled_attr =
 241         __ATTR(enabled, 0644, enabled_show, enabled_store);
 242
 243 static ssize_t single_flag_show(struct kobject *kobj,
 244                                 struct kobj_attribute *attr, char *buf,
 245                                 enum transparent_hugepage_flag flag)
 246 {
 247         return sprintf(buf, "%d\n",
 248                        !!test_bit(flag, &transparent_hugepage_flags));
 249 }
 250
 251 static ssize_t single_flag_store(struct kobject *kobj,
 252                                  struct kobj_attribute *attr,
 253                                  const char *buf, size_t count,
 254                                  enum transparent_hugepage_flag flag)
 255 {
 256         unsigned long value;
 257         int ret;
 258
 259         ret = kstrtoul(buf, 10, &value);
 260         if (ret < 0)
 261                 return ret;
 262         if (value > 1)
 263                 return -EINVAL;
 264
 265         if (value)
 266                 set_bit(flag, &transparent_hugepage_flags);
 267         else
 268                 clear_bit(flag, &transparent_hugepage_flags);
 269
 270         return count;
 271 }
 272
 273 /*
 274  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 275  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 276  * memory just to allocate one more hugepage.
 277  */
 278 static ssize_t defrag_show(struct kobject *kobj,
 279                            struct kobj_attribute *attr, char *buf)
 280 {
 281         return double_flag_show(kobj, attr, buf,
 282                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 283                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 284 }
 285 static ssize_t defrag_store(struct kobject *kobj,
 286                             struct kobj_attribute *attr,
 287                             const char *buf, size_t count)
 288 {
 289         return double_flag_store(kobj, attr, buf, count,
 290                                  TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 291                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 292 }
 293 static struct kobj_attribute defrag_attr =
 294         __ATTR(defrag, 0644, defrag_show, defrag_store);
 295
 296 #ifdef CONFIG_DEBUG_VM
 297 static ssize_t debug_cow_show(struct kobject *kobj,
 298                                 struct kobj_attribute *attr, char *buf)
 299 {
 300         return single_flag_show(kobj, attr, buf,
 301                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 302 }
 303 static ssize_t debug_cow_store(struct kobject *kobj,
 304                                struct kobj_attribute *attr,
 305                                const char *buf, size_t count)
 306 {
 307         return single_flag_store(kobj, attr, buf, count,
 308                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 309 }
 310 static struct kobj_attribute debug_cow_attr =
 311         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 312 #endif /* CONFIG_DEBUG_VM */
 313
 314 static struct attribute *hugepage_attr[] = {
 315         &enabled_attr.attr,
 316         &defrag_attr.attr,
 317 #ifdef CONFIG_DEBUG_VM
 318         &debug_cow_attr.attr,
 319 #endif
 320         NULL,
 321 };
 322
 323 static struct attribute_group hugepage_attr_group = {
 324         .attrs = hugepage_attr,
 325 };
 326
 327 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 328                                          struct kobj_attribute *attr,
 329                                          char *buf)
 330 {
 331         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 332 }
 333
 334 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 335                                           struct kobj_attribute *attr,
 336                                           const char *buf, size_t count)
 337 {
 338         unsigned long msecs;
 339         int err;
 340
 341         err = strict_strtoul(buf, 10, &msecs);
 342         if (err || msecs > UINT_MAX)
 343                 return -EINVAL;
 344
 345         khugepaged_scan_sleep_millisecs = msecs;
 346         wake_up_interruptible(&khugepaged_wait);
 347
 348         return count;
 349 }
 350 static struct kobj_attribute scan_sleep_millisecs_attr =
 351         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 352                scan_sleep_millisecs_store);
 353
 354 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 355                                           struct kobj_attribute *attr,
 356                                           char *buf)
 357 {
 358         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 359 }
 360
 361 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 362                                            struct kobj_attribute *attr,
 363                                            const char *buf, size_t count)
 364 {
 365         unsigned long msecs;
 366         int err;
 367
 368         err = strict_strtoul(buf, 10, &msecs);
 369         if (err || msecs > UINT_MAX)
 370                 return -EINVAL;
 371
 372         khugepaged_alloc_sleep_millisecs = msecs;
 373         wake_up_interruptible(&khugepaged_wait);
 374
 375         return count;
 376 }
 377 static struct kobj_attribute alloc_sleep_millisecs_attr =
 378         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 379                alloc_sleep_millisecs_store);
 380
 381 static ssize_t pages_to_scan_show(struct kobject *kobj,
 382                                   struct kobj_attribute *attr,
 383                                   char *buf)
 384 {
 385         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 386 }
 387 static ssize_t pages_to_scan_store(struct kobject *kobj,
 388                                    struct kobj_attribute *attr,
 389                                    const char *buf, size_t count)
 390 {
 391         int err;
 392         unsigned long pages;
 393
 394         err = strict_strtoul(buf, 10, &pages);
 395         if (err || !pages || pages > UINT_MAX)
 396                 return -EINVAL;
 397
 398         khugepaged_pages_to_scan = pages;
 399
 400         return count;
 401 }
 402 static struct kobj_attribute pages_to_scan_attr =
 403         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 404                pages_to_scan_store);
 405
 406 static ssize_t pages_collapsed_show(struct kobject *kobj,
 407                                     struct kobj_attribute *attr,
 408                                     char *buf)
 409 {
 410         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 411 }
 412 static struct kobj_attribute pages_collapsed_attr =
 413         __ATTR_RO(pages_collapsed);
 414
 415 static ssize_t full_scans_show(struct kobject *kobj,
 416                                struct kobj_attribute *attr,
 417                                char *buf)
 418 {
 419         return sprintf(buf, "%u\n", khugepaged_full_scans);
 420 }
 421 static struct kobj_attribute full_scans_attr =
 422         __ATTR_RO(full_scans);
 423
 424 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 425                                       struct kobj_attribute *attr, char *buf)
 426 {
 427         return single_flag_show(kobj, attr, buf,
 428                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 429 }
 430 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 431                                        struct kobj_attribute *attr,
 432                                        const char *buf, size_t count)
 433 {
 434         return single_flag_store(kobj, attr, buf, count,
 435                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 436 }
 437 static struct kobj_attribute khugepaged_defrag_attr =
 438         __ATTR(defrag, 0644, khugepaged_defrag_show,
 439                khugepaged_defrag_store);
 440
 441 /*
 442  * max_ptes_none controls if khugepaged should collapse hugepages over
 443  * any unmapped ptes in turn potentially increasing the memory
 444  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 445  * reduce the available free memory in the system as it
 446  * runs. Increasing max_ptes_none will instead potentially reduce the
 447  * free memory in the system during the khugepaged scan.
 448  */
 449 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 450                                              struct kobj_attribute *attr,
 451                                              char *buf)
 452 {
 453         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 454 }
 455 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 456                                               struct kobj_attribute *attr,
 457                                               const char *buf, size_t count)
 458 {
 459         int err;
 460         unsigned long max_ptes_none;
 461
 462         err = strict_strtoul(buf, 10, &max_ptes_none);
 463         if (err || max_ptes_none > HPAGE_PMD_NR-1)
 464                 return -EINVAL;
 465
 466         khugepaged_max_ptes_none = max_ptes_none;
 467
 468         return count;
 469 }
 470 static struct kobj_attribute khugepaged_max_ptes_none_attr =
 471         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 472                khugepaged_max_ptes_none_store);
 473
 474 static struct attribute *khugepaged_attr[] = {
 475         &khugepaged_defrag_attr.attr,
 476         &khugepaged_max_ptes_none_attr.attr,
 477         &pages_to_scan_attr.attr,
 478         &pages_collapsed_attr.attr,
 479         &full_scans_attr.attr,
 480         &scan_sleep_millisecs_attr.attr,
 481         &alloc_sleep_millisecs_attr.attr,
 482         NULL,
 483 };
 484
 485 static struct attribute_group khugepaged_attr_group = {
 486         .attrs = khugepaged_attr,
 487         .name = "khugepaged",
 488 };
 489
 490 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 491 {
 492         int err;
 493
 494         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 495         if (unlikely(!*hugepage_kobj)) {
 496                 printk(KERN_ERR "hugepage: failed kobject create\n");
 497                 return -ENOMEM;
 498         }
 499
 500         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 501         if (err) {
 502                 printk(KERN_ERR "hugepage: failed register hugeage group\n");
 503                 goto delete_obj;
 504         }
 505
 506         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 507         if (err) {
 508                 printk(KERN_ERR "hugepage: failed register hugeage group\n");
 509                 goto remove_hp_group;
 510         }
 511
 512         return 0;
 513
 514 remove_hp_group:
 515         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 516 delete_obj:
 517         kobject_put(*hugepage_kobj);
 518         return err;
 519 }
 520
 521 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 522 {
 523         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 524         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 525         kobject_put(hugepage_kobj);
 526 }
 527 #else
 528 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 529 {
 530         return 0;
 531 }
 532
 533 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 534 {
 535 }
 536 #endif /* CONFIG_SYSFS */
 537
 538 static int __init hugepage_init(void)
 539 {
 540         int err;
 541         struct kobject *hugepage_kobj;
 542
 543         if (!has_transparent_hugepage()) {
 544                 transparent_hugepage_flags = 0;
 545                 return -EINVAL;
 546         }
 547
 548         err = hugepage_init_sysfs(&hugepage_kobj);
 549         if (err)
 550                 return err;
 551
 552         err = khugepaged_slab_init();
 553         if (err)
 554                 goto out;
 555
 556         err = mm_slots_hash_init();
 557         if (err) {
 558                 khugepaged_slab_free();
 559                 goto out;
 560         }
 561
 562         /*
 563          * By default disable transparent hugepages on smaller systems,
 564          * where the extra memory used could hurt more than TLB overhead
 565          * is likely to save.  The admin can still enable it through /sys.
 566          */
 567         if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
 568                 transparent_hugepage_flags = 0;
 569
 570         start_khugepaged();
 571
 572         set_recommended_min_free_kbytes();
 573
 574         return 0;
 575 out:
 576         hugepage_exit_sysfs(hugepage_kobj);
 577         return err;
 578 }
 579 module_init(hugepage_init)
 580
 581 static int __init setup_transparent_hugepage(char *str)
 582 {
 583         int ret = 0;
 584         if (!str)
 585                 goto out;
 586         if (!strcmp(str, "always")) {
 587                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 588                         &transparent_hugepage_flags);
 589                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 590                           &transparent_hugepage_flags);
 591                 ret = 1;
 592         } else if (!strcmp(str, "madvise")) {
 593                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 594                           &transparent_hugepage_flags);
 595                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 596                         &transparent_hugepage_flags);
 597                 ret = 1;
 598         } else if (!strcmp(str, "never")) {
 599                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 600                           &transparent_hugepage_flags);
 601                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 602                           &transparent_hugepage_flags);
 603                 ret = 1;
 604         }
 605 out:
 606         if (!ret)
 607                 printk(KERN_WARNING
 608                        "transparent_hugepage= cannot parse, ignored\n");
 609         return ret;
 610 }
 611 __setup("transparent_hugepage=", setup_transparent_hugepage);
 612
 613 static void prepare_pmd_huge_pte(pgtable_t pgtable,
 614                                  struct mm_struct *mm)
 615 {
 616         assert_spin_locked(&mm->page_table_lock);
 617
 618         /* FIFO */
 619         if (!mm->pmd_huge_pte)
 620                 INIT_LIST_HEAD(&pgtable->lru);
 621         else
 622                 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
 623         mm->pmd_huge_pte = pgtable;
 624 }
 625
 626 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 627 {
 628         if (likely(vma->vm_flags & VM_WRITE))
 629                 pmd = pmd_mkwrite(pmd);
 630         return pmd;
 631 }
 632
 633 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 634                                         struct vm_area_struct *vma,
 635                                         unsigned long haddr, pmd_t *pmd,
 636                                         struct page *page)
 637 {
 638         pgtable_t pgtable;
 639
 640         VM_BUG_ON(!PageCompound(page));
 641         pgtable = pte_alloc_one(mm, haddr);
 642         if (unlikely(!pgtable))
 643                 return VM_FAULT_OOM;
 644
 645         clear_huge_page(page, haddr, HPAGE_PMD_NR);
 646         __SetPageUptodate(page);
 647
 648         spin_lock(&mm->page_table_lock);
 649         if (unlikely(!pmd_none(*pmd))) {
 650                 spin_unlock(&mm->page_table_lock);
 651                 mem_cgroup_uncharge_page(page);
 652                 put_page(page);
 653                 pte_free(mm, pgtable);
 654         } else {
 655                 pmd_t entry;
 656                 entry = mk_pmd(page, vma->vm_page_prot);
 657                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 658                 entry = pmd_mkhuge(entry);
 659                 /*
 660                  * The spinlocking to take the lru_lock inside
 661                  * page_add_new_anon_rmap() acts as a full memory
 662                  * barrier to be sure clear_huge_page writes become
 663                  * visible after the set_pmd_at() write.
 664                  */
 665                 page_add_new_anon_rmap(page, vma, haddr);
 666                 set_pmd_at(mm, haddr, pmd, entry);
 667                 prepare_pmd_huge_pte(pgtable, mm);
 668                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 669                 mm->nr_ptes++;
 670                 spin_unlock(&mm->page_table_lock);
 671         }
 672
 673         return 0;
 674 }
 675
 676 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 677 {
 678         return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
 679 }
 680
 681 static inline struct page *alloc_hugepage_vma(int defrag,
 682                                               struct vm_area_struct *vma,
 683                                               unsigned long haddr, int nd,
 684                                               gfp_t extra_gfp)
 685 {
 686         return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
 687                                HPAGE_PMD_ORDER, vma, haddr, nd);
 688 }
 689
 690 #ifndef CONFIG_NUMA
 691 static inline struct page *alloc_hugepage(int defrag)
 692 {
 693         return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
 694                            HPAGE_PMD_ORDER);
 695 }
 696 #endif
 697
 698 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 699                                unsigned long address, pmd_t *pmd,
 700                                unsigned int flags)
 701 {
 702         struct page *page;
 703         unsigned long haddr = address & HPAGE_PMD_MASK;
 704         pte_t *pte;
 705
 706         if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
 707                 if (unlikely(anon_vma_prepare(vma)))
 708                         return VM_FAULT_OOM;
 709                 if (unlikely(khugepaged_enter(vma)))
 710                         return VM_FAULT_OOM;
 711                 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
 712                                           vma, haddr, numa_node_id(), 0);
 713                 if (unlikely(!page)) {
 714                         count_vm_event(THP_FAULT_FALLBACK);
 715                         goto out;
 716                 }
 717                 count_vm_event(THP_FAULT_ALLOC);
 718                 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
 719                         put_page(page);
 720                         goto out;
 721                 }
 722                 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
 723                                                           page))) {
 724                         mem_cgroup_uncharge_page(page);
 725                         put_page(page);
 726                         goto out;
 727                 }
 728
 729                 return 0;
 730         }
 731 out:
 732         /*
 733          * Use __pte_alloc instead of pte_alloc_map, because we can't
 734          * run pte_offset_map on the pmd, if an huge pmd could
 735          * materialize from under us from a different thread.
 736          */
 737         if (unlikely(__pte_alloc(mm, vma, pmd, address)))
 738                 return VM_FAULT_OOM;
 739         /* if an huge pmd materialized from under us just retry later */
 740         if (unlikely(pmd_trans_huge(*pmd)))
 741                 return 0;
 742         /*
 743          * A regular pmd is established and it can't morph into a huge pmd
 744          * from under us anymore at this point because we hold the mmap_sem
 745          * read mode and khugepaged takes it in write mode. So now it's
 746          * safe to run pte_offset_map().
 747          */
 748         pte = pte_offset_map(pmd, address);
 749         return handle_pte_fault(mm, vma, address, pte, pmd, flags);
 750 }
 751
 752 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 753                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 754                   struct vm_area_struct *vma)
 755 {
 756         struct page *src_page;
 757         pmd_t pmd;
 758         pgtable_t pgtable;
 759         int ret;
 760
 761         ret = -ENOMEM;
 762         pgtable = pte_alloc_one(dst_mm, addr);
 763         if (unlikely(!pgtable))
 764                 goto out;
 765
 766         spin_lock(&dst_mm->page_table_lock);
 767         spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
 768
 769         ret = -EAGAIN;
 770         pmd = *src_pmd;
 771         if (unlikely(!pmd_trans_huge(pmd))) {
 772                 pte_free(dst_mm, pgtable);
 773                 goto out_unlock;
 774         }
 775         if (unlikely(pmd_trans_splitting(pmd))) {
 776                 /* split huge page running from under us */
 777                 spin_unlock(&src_mm->page_table_lock);
 778                 spin_unlock(&dst_mm->page_table_lock);
 779                 pte_free(dst_mm, pgtable);
 780
 781                 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
 782                 goto out;
 783         }
 784         src_page = pmd_page(pmd);
 785         VM_BUG_ON(!PageHead(src_page));
 786         get_page(src_page);
 787         page_dup_rmap(src_page);
 788         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 789
 790         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 791         pmd = pmd_mkold(pmd_wrprotect(pmd));
 792         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 793         prepare_pmd_huge_pte(pgtable, dst_mm);
 794         dst_mm->nr_ptes++;
 795
 796         ret = 0;
 797 out_unlock:
 798         spin_unlock(&src_mm->page_table_lock);
 799         spin_unlock(&dst_mm->page_table_lock);
 800 out:
 801         return ret;
 802 }
 803
 804 /* no "address" argument so destroys page coloring of some arch */
 805 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
 806 {
 807         pgtable_t pgtable;
 808
 809         assert_spin_locked(&mm->page_table_lock);
 810
 811         /* FIFO */
 812         pgtable = mm->pmd_huge_pte;
 813         if (list_empty(&pgtable->lru))
 814                 mm->pmd_huge_pte = NULL;
 815         else {
 816                 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
 817                                               struct page, lru);
 818                 list_del(&pgtable->lru);
 819         }
 820         return pgtable;
 821 }
 822
 823 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
 824                                         struct vm_area_struct *vma,
 825                                         unsigned long address,
 826                                         pmd_t *pmd, pmd_t orig_pmd,
 827                                         struct page *page,
 828                                         unsigned long haddr)
 829 {
 830         pgtable_t pgtable;
 831         pmd_t _pmd;
 832         int ret = 0, i;
 833         struct page **pages;
 834
 835         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
 836                         GFP_KERNEL);
 837         if (unlikely(!pages)) {
 838                 ret |= VM_FAULT_OOM;
 839                 goto out;
 840         }
 841
 842         for (i = 0; i < HPAGE_PMD_NR; i++) {
 843                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
 844                                                __GFP_OTHER_NODE,
 845                                                vma, address, page_to_nid(page));
 846                 if (unlikely(!pages[i] ||
 847                              mem_cgroup_newpage_charge(pages[i], mm,
 848                                                        GFP_KERNEL))) {
 849                         if (pages[i])
 850                                 put_page(pages[i]);
 851                         mem_cgroup_uncharge_start();
 852                         while (--i >= 0) {
 853                                 mem_cgroup_uncharge_page(pages[i]);
 854                                 put_page(pages[i]);
 855                         }
 856                         mem_cgroup_uncharge_end();
 857                         kfree(pages);
 858                         ret |= VM_FAULT_OOM;
 859                         goto out;
 860                 }
 861         }
 862
 863         for (i = 0; i < HPAGE_PMD_NR; i++) {
 864                 copy_user_highpage(pages[i], page + i,
 865                                    haddr + PAGE_SIZE * i, vma);
 866                 __SetPageUptodate(pages[i]);
 867                 cond_resched();
 868         }
 869
 870         spin_lock(&mm->page_table_lock);
 871         if (unlikely(!pmd_same(*pmd, orig_pmd)))
 872                 goto out_free_pages;
 873         VM_BUG_ON(!PageHead(page));
 874
 875         pmdp_clear_flush_notify(vma, haddr, pmd);
 876         /* leave pmd empty until pte is filled */
 877
 878         pgtable = get_pmd_huge_pte(mm);
 879         pmd_populate(mm, &_pmd, pgtable);
 880
 881         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
 882                 pte_t *pte, entry;
 883                 entry = mk_pte(pages[i], vma->vm_page_prot);
 884                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 885                 page_add_new_anon_rmap(pages[i], vma, haddr);
 886                 pte = pte_offset_map(&_pmd, haddr);
 887                 VM_BUG_ON(!pte_none(*pte));
 888                 set_pte_at(mm, haddr, pte, entry);
 889                 pte_unmap(pte);
 890         }
 891         kfree(pages);
 892
 893         smp_wmb(); /* make pte visible before pmd */
 894         pmd_populate(mm, pmd, pgtable);
 895         page_remove_rmap(page);
 896         spin_unlock(&mm->page_table_lock);
 897
 898         ret |= VM_FAULT_WRITE;
 899         put_page(page);
 900
 901 out:
 902         return ret;
 903
 904 out_free_pages:
 905         spin_unlock(&mm->page_table_lock);
 906         mem_cgroup_uncharge_start();
 907         for (i = 0; i < HPAGE_PMD_NR; i++) {
 908                 mem_cgroup_uncharge_page(pages[i]);
 909                 put_page(pages[i]);
 910         }
 911         mem_cgroup_uncharge_end();
 912         kfree(pages);
 913         goto out;
 914 }
 915
 916 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 917                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
 918 {
 919         int ret = 0;
 920         struct page *page, *new_page;
 921         unsigned long haddr;
 922
 923         VM_BUG_ON(!vma->anon_vma);
 924         spin_lock(&mm->page_table_lock);
 925         if (unlikely(!pmd_same(*pmd, orig_pmd)))
 926                 goto out_unlock;
 927
 928         page = pmd_page(orig_pmd);
 929         VM_BUG_ON(!PageCompound(page) || !PageHead(page));
 930         haddr = address & HPAGE_PMD_MASK;
 931         if (page_mapcount(page) == 1) {
 932                 pmd_t entry;
 933                 entry = pmd_mkyoung(orig_pmd);
 934                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 935                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
 936                         update_mmu_cache(vma, address, entry);
 937                 ret |= VM_FAULT_WRITE;
 938                 goto out_unlock;
 939         }
 940         get_page(page);
 941         spin_unlock(&mm->page_table_lock);
 942
 943         if (transparent_hugepage_enabled(vma) &&
 944             !transparent_hugepage_debug_cow())
 945                 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
 946                                               vma, haddr, numa_node_id(), 0);
 947         else
 948                 new_page = NULL;
 949
 950         if (unlikely(!new_page)) {
 951                 count_vm_event(THP_FAULT_FALLBACK);
 952                 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
 953                                                    pmd, orig_pmd, page, haddr);
 954                 if (ret & VM_FAULT_OOM)
 955                         split_huge_page(page);
 956                 put_page(page);
 957                 goto out;
 958         }
 959         count_vm_event(THP_FAULT_ALLOC);
 960
 961         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
 962                 put_page(new_page);
 963                 split_huge_page(page);
 964                 put_page(page);
 965                 ret |= VM_FAULT_OOM;
 966                 goto out;
 967         }
 968
 969         copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
 970         __SetPageUptodate(new_page);
 971
 972         spin_lock(&mm->page_table_lock);
 973         put_page(page);
 974         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
 975                 spin_unlock(&mm->page_table_lock);
 976                 mem_cgroup_uncharge_page(new_page);
 977                 put_page(new_page);
 978                 goto out;
 979         } else {
 980                 pmd_t entry;
 981                 VM_BUG_ON(!PageHead(page));
 982                 entry = mk_pmd(new_page, vma->vm_page_prot);
 983                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 984                 entry = pmd_mkhuge(entry);
 985                 pmdp_clear_flush_notify(vma, haddr, pmd);
 986                 page_add_new_anon_rmap(new_page, vma, haddr);
 987                 set_pmd_at(mm, haddr, pmd, entry);
 988                 update_mmu_cache(vma, address, entry);
 989                 page_remove_rmap(page);
 990                 put_page(page);
 991                 ret |= VM_FAULT_WRITE;
 992         }
 993 out_unlock:
 994         spin_unlock(&mm->page_table_lock);
 995 out:
 996         return ret;
 997 }
 998
 999 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
1000                                    unsigned long addr,
1001                                    pmd_t *pmd,
1002                                    unsigned int flags)
1003 {
1004         struct page *page = NULL;
1005
1006         assert_spin_locked(&mm->page_table_lock);
1007
1008         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1009                 goto out;
1010
1011         page = pmd_page(*pmd);
1012         VM_BUG_ON(!PageHead(page));
1013         if (flags & FOLL_TOUCH) {
1014                 pmd_t _pmd;
1015                 /*
1016                  * We should set the dirty bit only for FOLL_WRITE but
1017                  * for now the dirty bit in the pmd is meaningless.
1018                  * And if the dirty bit will become meaningful and
1019                  * we'll only set it with FOLL_WRITE, an atomic
1020                  * set_bit will be required on the pmd to set the
1021                  * young bit, instead of the current set_pmd_at.
1022                  */
1023                 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1024                 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1025         }
1026         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1027         VM_BUG_ON(!PageCompound(page));
1028         if (flags & FOLL_GET)
1029                 get_page_foll(page);
1030
1031 out:
1032         return page;
1033 }
1034
1035 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1036                  pmd_t *pmd, unsigned long addr)
1037 {
1038         int ret = 0;
1039
1040         if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1041                 struct page *page;
1042                 pgtable_t pgtable;
1043                 pgtable = get_pmd_huge_pte(tlb->mm);
1044                 page = pmd_page(*pmd);
1045                 pmd_clear(pmd);
1046                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1047                 page_remove_rmap(page);
1048                 VM_BUG_ON(page_mapcount(page) < 0);
1049                 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1050                 VM_BUG_ON(!PageHead(page));
1051                 tlb->mm->nr_ptes--;
1052                 spin_unlock(&tlb->mm->page_table_lock);
1053                 tlb_remove_page(tlb, page);
1054                 pte_free(tlb->mm, pgtable);
1055                 ret = 1;
1056         }
1057         return ret;
1058 }
1059
1060 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1061                 unsigned long addr, unsigned long end,
1062                 unsigned char *vec)
1063 {
1064         int ret = 0;
1065
1066         if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1067                 /*
1068                  * All logical pages in the range are present
1069                  * if backed by a huge page.
1070                  */
1071                 spin_unlock(&vma->vm_mm->page_table_lock);
1072                 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1073                 ret = 1;
1074         }
1075
1076         return ret;
1077 }
1078
1079 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1080                   unsigned long old_addr,
1081                   unsigned long new_addr, unsigned long old_end,
1082                   pmd_t *old_pmd, pmd_t *new_pmd)
1083 {
1084         int ret = 0;
1085         pmd_t pmd;
1086
1087         struct mm_struct *mm = vma->vm_mm;
1088
1089         if ((old_addr & ~HPAGE_PMD_MASK) ||
1090             (new_addr & ~HPAGE_PMD_MASK) ||
1091             old_end - old_addr < HPAGE_PMD_SIZE ||
1092             (new_vma->vm_flags & VM_NOHUGEPAGE))
1093                 goto out;
1094
1095         /*
1096          * The destination pmd shouldn't be established, free_pgtables()
1097          * should have release it.
1098          */
1099         if (WARN_ON(!pmd_none(*new_pmd))) {
1100                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1101                 goto out;
1102         }
1103
1104         ret = __pmd_trans_huge_lock(old_pmd, vma);
1105         if (ret == 1) {
1106                 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1107                 VM_BUG_ON(!pmd_none(*new_pmd));
1108                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1109                 spin_unlock(&mm->page_table_lock);
1110         }
1111 out:
1112         return ret;
1113 }
1114
1115 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1116                 unsigned long addr, pgprot_t newprot)
1117 {
1118         struct mm_struct *mm = vma->vm_mm;
1119         int ret = 0;
1120
1121         if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1122                 pmd_t entry;
1123                 entry = pmdp_get_and_clear(mm, addr, pmd);
1124                 entry = pmd_modify(entry, newprot);
1125                 set_pmd_at(mm, addr, pmd, entry);
1126                 spin_unlock(&vma->vm_mm->page_table_lock);
1127                 ret = 1;
1128         }
1129
1130         return ret;
1131 }
1132
1133 /*
1134  * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1135  * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1136  *
1137  * Note that if it returns 1, this routine returns without unlocking page
1138  * table locks. So callers must unlock them.
1139  */
1140 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1141 {
1142         spin_lock(&vma->vm_mm->page_table_lock);
1143         if (likely(pmd_trans_huge(*pmd))) {
1144                 if (unlikely(pmd_trans_splitting(*pmd))) {
1145                         spin_unlock(&vma->vm_mm->page_table_lock);
1146                         wait_split_huge_page(vma->anon_vma, pmd);
1147                         return -1;
1148                 } else {
1149                         /* Thp mapped by 'pmd' is stable, so we can
1150                          * handle it as it is. */
1151                         return 1;
1152                 }
1153         }
1154         spin_unlock(&vma->vm_mm->page_table_lock);
1155         return 0;
1156 }
1157
1158 pmd_t *page_check_address_pmd(struct page *page,
1159                               struct mm_struct *mm,
1160                               unsigned long address,
1161                               enum page_check_address_pmd_flag flag)
1162 {
1163         pgd_t *pgd;
1164         pud_t *pud;
1165         pmd_t *pmd, *ret = NULL;
1166
1167         if (address & ~HPAGE_PMD_MASK)
1168                 goto out;
1169
1170         pgd = pgd_offset(mm, address);
1171         if (!pgd_present(*pgd))
1172                 goto out;
1173
1174         pud = pud_offset(pgd, address);
1175         if (!pud_present(*pud))
1176                 goto out;
1177
1178         pmd = pmd_offset(pud, address);
1179         if (pmd_none(*pmd))
1180                 goto out;
1181         if (pmd_page(*pmd) != page)
1182                 goto out;
1183         /*
1184          * split_vma() may create temporary aliased mappings. There is
1185          * no risk as long as all huge pmd are found and have their
1186          * splitting bit set before __split_huge_page_refcount
1187          * runs. Finding the same huge pmd more than once during the
1188          * same rmap walk is not a problem.
1189          */
1190         if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1191             pmd_trans_splitting(*pmd))
1192                 goto out;
1193         if (pmd_trans_huge(*pmd)) {
1194                 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1195                           !pmd_trans_splitting(*pmd));
1196                 ret = pmd;
1197         }
1198 out:
1199         return ret;
1200 }
1201
1202 static int __split_huge_page_splitting(struct page *page,
1203                                        struct vm_area_struct *vma,
1204                                        unsigned long address)
1205 {
1206         struct mm_struct *mm = vma->vm_mm;
1207         pmd_t *pmd;
1208         int ret = 0;
1209
1210         spin_lock(&mm->page_table_lock);
1211         pmd = page_check_address_pmd(page, mm, address,
1212                                      PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1213         if (pmd) {
1214                 /*
1215                  * We can't temporarily set the pmd to null in order
1216                  * to split it, the pmd must remain marked huge at all
1217                  * times or the VM won't take the pmd_trans_huge paths
1218                  * and it won't wait on the anon_vma->root->mutex to
1219                  * serialize against split_huge_page*.
1220                  */
1221                 pmdp_splitting_flush_notify(vma, address, pmd);
1222                 ret = 1;
1223         }
1224         spin_unlock(&mm->page_table_lock);
1225
1226         return ret;
1227 }
1228
1229 static void __split_huge_page_refcount(struct page *page)
1230 {
1231         int i;
1232         struct zone *zone = page_zone(page);
1233         struct lruvec *lruvec;
1234         int tail_count = 0;
1235
1236         /* prevent PageLRU to go away from under us, and freeze lru stats */
1237         spin_lock_irq(&zone->lru_lock);
1238         lruvec = mem_cgroup_page_lruvec(page, zone);
1239
1240         compound_lock(page);
1241         /* complete memcg works before add pages to LRU */
1242         mem_cgroup_split_huge_fixup(page);
1243
1244         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1245                 struct page *page_tail = page + i;
1246
1247                 /* tail_page->_mapcount cannot change */
1248                 BUG_ON(page_mapcount(page_tail) < 0);
1249                 tail_count += page_mapcount(page_tail);
1250                 /* check for overflow */
1251                 BUG_ON(tail_count < 0);
1252                 BUG_ON(atomic_read(&page_tail->_count) != 0);
1253                 /*
1254                  * tail_page->_count is zero and not changing from
1255                  * under us. But get_page_unless_zero() may be running
1256                  * from under us on the tail_page. If we used
1257                  * atomic_set() below instead of atomic_add(), we
1258                  * would then run atomic_set() concurrently with
1259                  * get_page_unless_zero(), and atomic_set() is
1260                  * implemented in C not using locked ops. spin_unlock
1261                  * on x86 sometime uses locked ops because of PPro
1262                  * errata 66, 92, so unless somebody can guarantee
1263                  * atomic_set() here would be safe on all archs (and
1264                  * not only on x86), it's safer to use atomic_add().
1265                  */
1266                 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1267                            &page_tail->_count);
1268
1269                 /* after clearing PageTail the gup refcount can be released */
1270                 smp_mb();
1271
1272                 /*
1273                  * retain hwpoison flag of the poisoned tail page:
1274                  *   fix for the unsuitable process killed on Guest Machine(KVM)
1275                  *   by the memory-failure.
1276                  */
1277                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1278                 page_tail->flags |= (page->flags &
1279                                      ((1L << PG_referenced) |
1280                                       (1L << PG_swapbacked) |
1281                                       (1L << PG_mlocked) |
1282                                       (1L << PG_uptodate)));
1283                 page_tail->flags |= (1L << PG_dirty);
1284
1285                 /* clear PageTail before overwriting first_page */
1286                 smp_wmb();
1287
1288                 /*
1289                  * __split_huge_page_splitting() already set the
1290                  * splitting bit in all pmd that could map this
1291                  * hugepage, that will ensure no CPU can alter the
1292                  * mapcount on the head page. The mapcount is only
1293                  * accounted in the head page and it has to be
1294                  * transferred to all tail pages in the below code. So
1295                  * for this code to be safe, the split the mapcount
1296                  * can't change. But that doesn't mean userland can't
1297                  * keep changing and reading the page contents while
1298                  * we transfer the mapcount, so the pmd splitting
1299                  * status is achieved setting a reserved bit in the
1300                  * pmd, not by clearing the present bit.
1301                 */
1302                 page_tail->_mapcount = page->_mapcount;
1303
1304                 BUG_ON(page_tail->mapping);
1305                 page_tail->mapping = page->mapping;
1306
1307                 page_tail->index = page->index + i;
1308
1309                 BUG_ON(!PageAnon(page_tail));
1310                 BUG_ON(!PageUptodate(page_tail));
1311                 BUG_ON(!PageDirty(page_tail));
1312                 BUG_ON(!PageSwapBacked(page_tail));
1313
1314                 lru_add_page_tail(page, page_tail, lruvec);
1315         }
1316         atomic_sub(tail_count, &page->_count);
1317         BUG_ON(atomic_read(&page->_count) <= 0);
1318
1319         __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1320         __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1321
1322         ClearPageCompound(page);
1323         compound_unlock(page);
1324         spin_unlock_irq(&zone->lru_lock);
1325
1326         for (i = 1; i < HPAGE_PMD_NR; i++) {
1327                 struct page *page_tail = page + i;
1328                 BUG_ON(page_count(page_tail) <= 0);
1329                 /*
1330                  * Tail pages may be freed if there wasn't any mapping
1331                  * like if add_to_swap() is running on a lru page that
1332                  * had its mapping zapped. And freeing these pages
1333                  * requires taking the lru_lock so we do the put_page
1334                  * of the tail pages after the split is complete.
1335                  */
1336                 put_page(page_tail);
1337         }
1338
1339         /*
1340          * Only the head page (now become a regular page) is required
1341          * to be pinned by the caller.
1342          */
1343         BUG_ON(page_count(page) <= 0);
1344 }
1345
1346 static int __split_huge_page_map(struct page *page,
1347                                  struct vm_area_struct *vma,
1348                                  unsigned long address)
1349 {
1350         struct mm_struct *mm = vma->vm_mm;
1351         pmd_t *pmd, _pmd;
1352         int ret = 0, i;
1353         pgtable_t pgtable;
1354         unsigned long haddr;
1355
1356         spin_lock(&mm->page_table_lock);
1357         pmd = page_check_address_pmd(page, mm, address,
1358                                      PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1359         if (pmd) {
1360                 pgtable = get_pmd_huge_pte(mm);
1361                 pmd_populate(mm, &_pmd, pgtable);
1362
1363                 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1364                      i++, haddr += PAGE_SIZE) {
1365                         pte_t *pte, entry;
1366                         BUG_ON(PageCompound(page+i));
1367                         entry = mk_pte(page + i, vma->vm_page_prot);
1368                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1369                         if (!pmd_write(*pmd))
1370                                 entry = pte_wrprotect(entry);
1371                         else
1372                                 BUG_ON(page_mapcount(page) != 1);
1373                         if (!pmd_young(*pmd))
1374                                 entry = pte_mkold(entry);
1375                         pte = pte_offset_map(&_pmd, haddr);
1376                         BUG_ON(!pte_none(*pte));
1377                         set_pte_at(mm, haddr, pte, entry);
1378                         pte_unmap(pte);
1379                 }
1380
1381                 smp_wmb(); /* make pte visible before pmd */
1382                 /*
1383                  * Up to this point the pmd is present and huge and
1384                  * userland has the whole access to the hugepage
1385                  * during the split (which happens in place). If we
1386                  * overwrite the pmd with the not-huge version
1387                  * pointing to the pte here (which of course we could
1388                  * if all CPUs were bug free), userland could trigger
1389                  * a small page size TLB miss on the small sized TLB
1390                  * while the hugepage TLB entry is still established
1391                  * in the huge TLB. Some CPU doesn't like that. See
1392                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1393                  * Erratum 383 on page 93. Intel should be safe but is
1394                  * also warns that it's only safe if the permission
1395                  * and cache attributes of the two entries loaded in
1396                  * the two TLB is identical (which should be the case
1397                  * here). But it is generally safer to never allow
1398                  * small and huge TLB entries for the same virtual
1399                  * address to be loaded simultaneously. So instead of
1400                  * doing "pmd_populate(); flush_tlb_range();" we first
1401                  * mark the current pmd notpresent (atomically because
1402                  * here the pmd_trans_huge and pmd_trans_splitting
1403                  * must remain set at all times on the pmd until the
1404                  * split is complete for this pmd), then we flush the
1405                  * SMP TLB and finally we write the non-huge version
1406                  * of the pmd entry with pmd_populate.
1407                  */
1408                 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1409                 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1410                 pmd_populate(mm, pmd, pgtable);
1411                 ret = 1;
1412         }
1413         spin_unlock(&mm->page_table_lock);
1414
1415         return ret;
1416 }
1417
1418 /* must be called with anon_vma->root->mutex hold */
1419 static void __split_huge_page(struct page *page,
1420                               struct anon_vma *anon_vma)
1421 {
1422         int mapcount, mapcount2;
1423         struct anon_vma_chain *avc;
1424
1425         BUG_ON(!PageHead(page));
1426         BUG_ON(PageTail(page));
1427
1428         mapcount = 0;
1429         list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1430                 struct vm_area_struct *vma = avc->vma;
1431                 unsigned long addr = vma_address(page, vma);
1432                 BUG_ON(is_vma_temporary_stack(vma));
1433                 if (addr == -EFAULT)
1434                         continue;
1435                 mapcount += __split_huge_page_splitting(page, vma, addr);
1436         }
1437         /*
1438          * It is critical that new vmas are added to the tail of the
1439          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1440          * and establishes a child pmd before
1441          * __split_huge_page_splitting() freezes the parent pmd (so if
1442          * we fail to prevent copy_huge_pmd() from running until the
1443          * whole __split_huge_page() is complete), we will still see
1444          * the newly established pmd of the child later during the
1445          * walk, to be able to set it as pmd_trans_splitting too.
1446          */
1447         if (mapcount != page_mapcount(page))
1448                 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1449                        mapcount, page_mapcount(page));
1450         BUG_ON(mapcount != page_mapcount(page));
1451
1452         __split_huge_page_refcount(page);
1453
1454         mapcount2 = 0;
1455         list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1456                 struct vm_area_struct *vma = avc->vma;
1457                 unsigned long addr = vma_address(page, vma);
1458                 BUG_ON(is_vma_temporary_stack(vma));
1459                 if (addr == -EFAULT)
1460                         continue;
1461                 mapcount2 += __split_huge_page_map(page, vma, addr);
1462         }
1463         if (mapcount != mapcount2)
1464                 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1465                        mapcount, mapcount2, page_mapcount(page));
1466         BUG_ON(mapcount != mapcount2);
1467 }
1468
1469 int split_huge_page(struct page *page)
1470 {
1471         struct anon_vma *anon_vma;
1472         int ret = 1;
1473
1474         BUG_ON(!PageAnon(page));
1475         anon_vma = page_lock_anon_vma(page);
1476         if (!anon_vma)
1477                 goto out;
1478         ret = 0;
1479         if (!PageCompound(page))
1480                 goto out_unlock;
1481
1482         BUG_ON(!PageSwapBacked(page));
1483         __split_huge_page(page, anon_vma);
1484         count_vm_event(THP_SPLIT);
1485
1486         BUG_ON(PageCompound(page));
1487 out_unlock:
1488         page_unlock_anon_vma(anon_vma);
1489 out:
1490         return ret;
1491 }
1492
1493 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1494
1495 int hugepage_madvise(struct vm_area_struct *vma,
1496                      unsigned long *vm_flags, int advice)
1497 {
1498         switch (advice) {
1499         case MADV_HUGEPAGE:
1500                 /*
1501                  * Be somewhat over-protective like KSM for now!
1502                  */
1503                 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1504                         return -EINVAL;
1505                 *vm_flags &= ~VM_NOHUGEPAGE;
1506                 *vm_flags |= VM_HUGEPAGE;
1507                 /*
1508                  * If the vma become good for khugepaged to scan,
1509                  * register it here without waiting a page fault that
1510                  * may not happen any time soon.
1511                  */
1512                 if (unlikely(khugepaged_enter_vma_merge(vma)))
1513                         return -ENOMEM;
1514                 break;
1515         case MADV_NOHUGEPAGE:
1516                 /*
1517                  * Be somewhat over-protective like KSM for now!
1518                  */
1519                 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1520                         return -EINVAL;
1521                 *vm_flags &= ~VM_HUGEPAGE;
1522                 *vm_flags |= VM_NOHUGEPAGE;
1523                 /*
1524                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1525                  * this vma even if we leave the mm registered in khugepaged if
1526                  * it got registered before VM_NOHUGEPAGE was set.
1527                  */
1528                 break;
1529         }
1530
1531         return 0;
1532 }
1533
1534 static int __init khugepaged_slab_init(void)
1535 {
1536         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1537                                           sizeof(struct mm_slot),
1538                                           __alignof__(struct mm_slot), 0, NULL);
1539         if (!mm_slot_cache)
1540                 return -ENOMEM;
1541
1542         return 0;
1543 }
1544
1545 static void __init khugepaged_slab_free(void)
1546 {
1547         kmem_cache_destroy(mm_slot_cache);
1548         mm_slot_cache = NULL;
1549 }
1550
1551 static inline struct mm_slot *alloc_mm_slot(void)
1552 {
1553         if (!mm_slot_cache)     /* initialization failed */
1554                 return NULL;
1555         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1556 }
1557
1558 static inline void free_mm_slot(struct mm_slot *mm_slot)
1559 {
1560         kmem_cache_free(mm_slot_cache, mm_slot);
1561 }
1562
1563 static int __init mm_slots_hash_init(void)
1564 {
1565         mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1566                                 GFP_KERNEL);
1567         if (!mm_slots_hash)
1568                 return -ENOMEM;
1569         return 0;
1570 }
1571
1572 #if 0
1573 static void __init mm_slots_hash_free(void)
1574 {
1575         kfree(mm_slots_hash);
1576         mm_slots_hash = NULL;
1577 }
1578 #endif
1579
1580 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1581 {
1582         struct mm_slot *mm_slot;
1583         struct hlist_head *bucket;
1584         struct hlist_node *node;
1585
1586         bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1587                                 % MM_SLOTS_HASH_HEADS];
1588         hlist_for_each_entry(mm_slot, node, bucket, hash) {
1589                 if (mm == mm_slot->mm)
1590                         return mm_slot;
1591         }
1592         return NULL;
1593 }
1594
1595 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1596                                     struct mm_slot *mm_slot)
1597 {
1598         struct hlist_head *bucket;
1599
1600         bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1601                                 % MM_SLOTS_HASH_HEADS];
1602         mm_slot->mm = mm;
1603         hlist_add_head(&mm_slot->hash, bucket);
1604 }
1605
1606 static inline int khugepaged_test_exit(struct mm_struct *mm)
1607 {
1608         return atomic_read(&mm->mm_users) == 0;
1609 }
1610
1611 int __khugepaged_enter(struct mm_struct *mm)
1612 {
1613         struct mm_slot *mm_slot;
1614         int wakeup;
1615
1616         mm_slot = alloc_mm_slot();
1617         if (!mm_slot)
1618                 return -ENOMEM;
1619
1620         /* __khugepaged_exit() must not run from under us */
1621         VM_BUG_ON(khugepaged_test_exit(mm));
1622         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1623                 free_mm_slot(mm_slot);
1624                 return 0;
1625         }
1626
1627         spin_lock(&khugepaged_mm_lock);
1628         insert_to_mm_slots_hash(mm, mm_slot);
1629         /*
1630          * Insert just behind the scanning cursor, to let the area settle
1631          * down a little.
1632          */
1633         wakeup = list_empty(&khugepaged_scan.mm_head);
1634         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1635         spin_unlock(&khugepaged_mm_lock);
1636
1637         atomic_inc(&mm->mm_count);
1638         if (wakeup)
1639                 wake_up_interruptible(&khugepaged_wait);
1640
1641         return 0;
1642 }
1643
1644 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1645 {
1646         unsigned long hstart, hend;
1647         if (!vma->anon_vma)
1648                 /*
1649                  * Not yet faulted in so we will register later in the
1650                  * page fault if needed.
1651                  */
1652                 return 0;
1653         if (vma->vm_ops)
1654                 /* khugepaged not yet working on file or special mappings */
1655                 return 0;
1656         VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1657         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1658         hend = vma->vm_end & HPAGE_PMD_MASK;
1659         if (hstart < hend)
1660                 return khugepaged_enter(vma);
1661         return 0;
1662 }
1663
1664 void __khugepaged_exit(struct mm_struct *mm)
1665 {
1666         struct mm_slot *mm_slot;
1667         int free = 0;
1668
1669         spin_lock(&khugepaged_mm_lock);
1670         mm_slot = get_mm_slot(mm);
1671         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1672                 hlist_del(&mm_slot->hash);
1673                 list_del(&mm_slot->mm_node);
1674                 free = 1;
1675         }
1676         spin_unlock(&khugepaged_mm_lock);
1677
1678         if (free) {
1679                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1680                 free_mm_slot(mm_slot);
1681                 mmdrop(mm);
1682         } else if (mm_slot) {
1683                 /*
1684                  * This is required to serialize against
1685                  * khugepaged_test_exit() (which is guaranteed to run
1686                  * under mmap sem read mode). Stop here (after we
1687                  * return all pagetables will be destroyed) until
1688                  * khugepaged has finished working on the pagetables
1689                  * under the mmap_sem.
1690                  */
1691                 down_write(&mm->mmap_sem);
1692                 up_write(&mm->mmap_sem);
1693         }
1694 }
1695
1696 static void release_pte_page(struct page *page)
1697 {
1698         /* 0 stands for page_is_file_cache(page) == false */
1699         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1700         unlock_page(page);
1701         putback_lru_page(page);
1702 }
1703
1704 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1705 {
1706         while (--_pte >= pte) {
1707                 pte_t pteval = *_pte;
1708                 if (!pte_none(pteval))
1709                         release_pte_page(pte_page(pteval));
1710         }
1711 }
1712
1713 static void release_all_pte_pages(pte_t *pte)
1714 {
1715         release_pte_pages(pte, pte + HPAGE_PMD_NR);
1716 }
1717
1718 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1719                                         unsigned long address,
1720                                         pte_t *pte)
1721 {
1722         struct page *page;
1723         pte_t *_pte;
1724         int referenced = 0, isolated = 0, none = 0;
1725         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1726              _pte++, address += PAGE_SIZE) {
1727                 pte_t pteval = *_pte;
1728                 if (pte_none(pteval)) {
1729                         if (++none <= khugepaged_max_ptes_none)
1730                                 continue;
1731                         else {
1732                                 release_pte_pages(pte, _pte);
1733                                 goto out;
1734                         }
1735                 }
1736                 if (!pte_present(pteval) || !pte_write(pteval)) {
1737                         release_pte_pages(pte, _pte);
1738                         goto out;
1739                 }
1740                 page = vm_normal_page(vma, address, pteval);
1741                 if (unlikely(!page)) {
1742                         release_pte_pages(pte, _pte);
1743                         goto out;
1744                 }
1745                 VM_BUG_ON(PageCompound(page));
1746                 BUG_ON(!PageAnon(page));
1747                 VM_BUG_ON(!PageSwapBacked(page));
1748
1749                 /* cannot use mapcount: can't collapse if there's a gup pin */
1750                 if (page_count(page) != 1) {
1751                         release_pte_pages(pte, _pte);
1752                         goto out;
1753                 }
1754                 /*
1755                  * We can do it before isolate_lru_page because the
1756                  * page can't be freed from under us. NOTE: PG_lock
1757                  * is needed to serialize against split_huge_page
1758                  * when invoked from the VM.
1759                  */
1760                 if (!trylock_page(page)) {
1761                         release_pte_pages(pte, _pte);
1762                         goto out;
1763                 }
1764                 /*
1765                  * Isolate the page to avoid collapsing an hugepage
1766                  * currently in use by the VM.
1767                  */
1768                 if (isolate_lru_page(page)) {
1769                         unlock_page(page);
1770                         release_pte_pages(pte, _pte);
1771                         goto out;
1772                 }
1773                 /* 0 stands for page_is_file_cache(page) == false */
1774                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1775                 VM_BUG_ON(!PageLocked(page));
1776                 VM_BUG_ON(PageLRU(page));
1777
1778                 /* If there is no mapped pte young don't collapse the page */
1779                 if (pte_young(pteval) || PageReferenced(page) ||
1780                     mmu_notifier_test_young(vma->vm_mm, address))
1781                         referenced = 1;
1782         }
1783         if (unlikely(!referenced))
1784                 release_all_pte_pages(pte);
1785         else
1786                 isolated = 1;
1787 out:
1788         return isolated;
1789 }
1790
1791 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1792                                       struct vm_area_struct *vma,
1793                                       unsigned long address,
1794                                       spinlock_t *ptl)
1795 {
1796         pte_t *_pte;
1797         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1798                 pte_t pteval = *_pte;
1799                 struct page *src_page;
1800
1801                 if (pte_none(pteval)) {
1802                         clear_user_highpage(page, address);
1803                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1804                 } else {
1805                         src_page = pte_page(pteval);
1806                         copy_user_highpage(page, src_page, address, vma);
1807                         VM_BUG_ON(page_mapcount(src_page) != 1);
1808                         release_pte_page(src_page);
1809                         /*
1810                          * ptl mostly unnecessary, but preempt has to
1811                          * be disabled to update the per-cpu stats
1812                          * inside page_remove_rmap().
1813                          */
1814                         spin_lock(ptl);
1815                         /*
1816                          * paravirt calls inside pte_clear here are
1817                          * superfluous.
1818                          */
1819                         pte_clear(vma->vm_mm, address, _pte);
1820                         page_remove_rmap(src_page);
1821                         spin_unlock(ptl);
1822                         free_page_and_swap_cache(src_page);
1823                 }
1824
1825                 address += PAGE_SIZE;
1826                 page++;
1827         }
1828 }
1829
1830 static void collapse_huge_page(struct mm_struct *mm,
1831                                unsigned long address,
1832                                struct page **hpage,
1833                                struct vm_area_struct *vma,
1834                                int node)
1835 {
1836         pgd_t *pgd;
1837         pud_t *pud;
1838         pmd_t *pmd, _pmd;
1839         pte_t *pte;
1840         pgtable_t pgtable;
1841         struct page *new_page;
1842         spinlock_t *ptl;
1843         int isolated;
1844         unsigned long hstart, hend;
1845
1846         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1847 #ifndef CONFIG_NUMA
1848         up_read(&mm->mmap_sem);
1849         VM_BUG_ON(!*hpage);
1850         new_page = *hpage;
1851 #else
1852         VM_BUG_ON(*hpage);
1853         /*
1854          * Allocate the page while the vma is still valid and under
1855          * the mmap_sem read mode so there is no memory allocation
1856          * later when we take the mmap_sem in write mode. This is more
1857          * friendly behavior (OTOH it may actually hide bugs) to
1858          * filesystems in userland with daemons allocating memory in
1859          * the userland I/O paths.  Allocating memory with the
1860          * mmap_sem in read mode is good idea also to allow greater
1861          * scalability.
1862          */
1863         new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1864                                       node, __GFP_OTHER_NODE);
1865
1866         /*
1867          * After allocating the hugepage, release the mmap_sem read lock in
1868          * preparation for taking it in write mode.
1869          */
1870         up_read(&mm->mmap_sem);
1871         if (unlikely(!new_page)) {
1872                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1873                 *hpage = ERR_PTR(-ENOMEM);
1874                 return;
1875         }
1876         count_vm_event(THP_COLLAPSE_ALLOC);
1877 #endif
1878
1879         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1880 #ifdef CONFIG_NUMA
1881                 put_page(new_page);
1882 #endif
1883                 return;
1884         }
1885
1886         /*
1887          * Prevent all access to pagetables with the exception of
1888          * gup_fast later hanlded by the ptep_clear_flush and the VM
1889          * handled by the anon_vma lock + PG_lock.
1890          */
1891         down_write(&mm->mmap_sem);
1892         if (unlikely(khugepaged_test_exit(mm)))
1893                 goto out;
1894
1895         vma = find_vma(mm, address);
1896         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1897         hend = vma->vm_end & HPAGE_PMD_MASK;
1898         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1899                 goto out;
1900
1901         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1902             (vma->vm_flags & VM_NOHUGEPAGE))
1903                 goto out;
1904
1905         if (!vma->anon_vma || vma->vm_ops)
1906                 goto out;
1907         if (is_vma_temporary_stack(vma))
1908                 goto out;
1909         VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1910
1911         pgd = pgd_offset(mm, address);
1912         if (!pgd_present(*pgd))
1913                 goto out;
1914
1915         pud = pud_offset(pgd, address);
1916         if (!pud_present(*pud))
1917                 goto out;
1918
1919         pmd = pmd_offset(pud, address);
1920         /* pmd can't go away or become huge under us */
1921         if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1922                 goto out;
1923
1924         anon_vma_lock(vma->anon_vma);
1925
1926         pte = pte_offset_map(pmd, address);
1927         ptl = pte_lockptr(mm, pmd);
1928
1929         spin_lock(&mm->page_table_lock); /* probably unnecessary */
1930         /*
1931          * After this gup_fast can't run anymore. This also removes
1932          * any huge TLB entry from the CPU so we won't allow
1933          * huge and small TLB entries for the same virtual address
1934          * to avoid the risk of CPU bugs in that area.
1935          */
1936         _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1937         spin_unlock(&mm->page_table_lock);
1938
1939         spin_lock(ptl);
1940         isolated = __collapse_huge_page_isolate(vma, address, pte);
1941         spin_unlock(ptl);
1942
1943         if (unlikely(!isolated)) {
1944                 pte_unmap(pte);
1945                 spin_lock(&mm->page_table_lock);
1946                 BUG_ON(!pmd_none(*pmd));
1947                 set_pmd_at(mm, address, pmd, _pmd);
1948                 spin_unlock(&mm->page_table_lock);
1949                 anon_vma_unlock(vma->anon_vma);
1950                 goto out;
1951         }
1952
1953         /*
1954          * All pages are isolated and locked so anon_vma rmap
1955          * can't run anymore.
1956          */
1957         anon_vma_unlock(vma->anon_vma);
1958
1959         __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1960         pte_unmap(pte);
1961         __SetPageUptodate(new_page);
1962         pgtable = pmd_pgtable(_pmd);
1963         VM_BUG_ON(page_count(pgtable) != 1);
1964         VM_BUG_ON(page_mapcount(pgtable) != 0);
1965
1966         _pmd = mk_pmd(new_page, vma->vm_page_prot);
1967         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1968         _pmd = pmd_mkhuge(_pmd);
1969
1970         /*
1971          * spin_lock() below is not the equivalent of smp_wmb(), so
1972          * this is needed to avoid the copy_huge_page writes to become
1973          * visible after the set_pmd_at() write.
1974          */
1975         smp_wmb();
1976
1977         spin_lock(&mm->page_table_lock);
1978         BUG_ON(!pmd_none(*pmd));
1979         page_add_new_anon_rmap(new_page, vma, address);
1980         set_pmd_at(mm, address, pmd, _pmd);
1981         update_mmu_cache(vma, address, _pmd);
1982         prepare_pmd_huge_pte(pgtable, mm);
1983         spin_unlock(&mm->page_table_lock);
1984
1985 #ifndef CONFIG_NUMA
1986         *hpage = NULL;
1987 #endif
1988         khugepaged_pages_collapsed++;
1989 out_up_write:
1990         up_write(&mm->mmap_sem);
1991         return;
1992
1993 out:
1994         mem_cgroup_uncharge_page(new_page);
1995 #ifdef CONFIG_NUMA
1996         put_page(new_page);
1997 #endif
1998         goto out_up_write;
1999 }
2000
2001 static int khugepaged_scan_pmd(struct mm_struct *mm,
2002                                struct vm_area_struct *vma,
2003                                unsigned long address,
2004                                struct page **hpage)
2005 {
2006         pgd_t *pgd;
2007         pud_t *pud;
2008         pmd_t *pmd;
2009         pte_t *pte, *_pte;
2010         int ret = 0, referenced = 0, none = 0;
2011         struct page *page;
2012         unsigned long _address;
2013         spinlock_t *ptl;
2014         int node = -1;
2015
2016         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2017
2018         pgd = pgd_offset(mm, address);
2019         if (!pgd_present(*pgd))
2020                 goto out;
2021
2022         pud = pud_offset(pgd, address);
2023         if (!pud_present(*pud))
2024                 goto out;
2025
2026         pmd = pmd_offset(pud, address);
2027         if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
2028                 goto out;
2029
2030         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2031         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2032              _pte++, _address += PAGE_SIZE) {
2033                 pte_t pteval = *_pte;
2034                 if (pte_none(pteval)) {
2035                         if (++none <= khugepaged_max_ptes_none)
2036                                 continue;
2037                         else
2038                                 goto out_unmap;
2039                 }
2040                 if (!pte_present(pteval) || !pte_write(pteval))
2041                         goto out_unmap;
2042                 page = vm_normal_page(vma, _address, pteval);
2043                 if (unlikely(!page))
2044                         goto out_unmap;
2045                 /*
2046                  * Chose the node of the first page. This could
2047                  * be more sophisticated and look at more pages,
2048                  * but isn't for now.
2049                  */
2050                 if (node == -1)
2051                         node = page_to_nid(page);
2052                 VM_BUG_ON(PageCompound(page));
2053                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2054                         goto out_unmap;
2055                 /* cannot use mapcount: can't collapse if there's a gup pin */
2056                 if (page_count(page) != 1)
2057                         goto out_unmap;
2058                 if (pte_young(pteval) || PageReferenced(page) ||
2059                     mmu_notifier_test_young(vma->vm_mm, address))
2060                         referenced = 1;
2061         }
2062         if (referenced)
2063                 ret = 1;
2064 out_unmap:
2065         pte_unmap_unlock(pte, ptl);
2066         if (ret)
2067                 /* collapse_huge_page will return with the mmap_sem released */
2068                 collapse_huge_page(mm, address, hpage, vma, node);
2069 out:
2070         return ret;
2071 }
2072
2073 static void collect_mm_slot(struct mm_slot *mm_slot)
2074 {
2075         struct mm_struct *mm = mm_slot->mm;
2076
2077         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2078
2079         if (khugepaged_test_exit(mm)) {
2080                 /* free mm_slot */
2081                 hlist_del(&mm_slot->hash);
2082                 list_del(&mm_slot->mm_node);
2083
2084                 /*
2085                  * Not strictly needed because the mm exited already.
2086                  *
2087                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2088                  */
2089
2090                 /* khugepaged_mm_lock actually not necessary for the below */
2091                 free_mm_slot(mm_slot);
2092                 mmdrop(mm);
2093         }
2094 }
2095
2096 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2097                                             struct page **hpage)
2098         __releases(&khugepaged_mm_lock)
2099         __acquires(&khugepaged_mm_lock)
2100 {
2101         struct mm_slot *mm_slot;
2102         struct mm_struct *mm;
2103         struct vm_area_struct *vma;
2104         int progress = 0;
2105
2106         VM_BUG_ON(!pages);
2107         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2108
2109         if (khugepaged_scan.mm_slot)
2110                 mm_slot = khugepaged_scan.mm_slot;
2111         else {
2112                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2113                                      struct mm_slot, mm_node);
2114                 khugepaged_scan.address = 0;
2115                 khugepaged_scan.mm_slot = mm_slot;
2116         }
2117         spin_unlock(&khugepaged_mm_lock);
2118
2119         mm = mm_slot->mm;
2120         down_read(&mm->mmap_sem);
2121         if (unlikely(khugepaged_test_exit(mm)))
2122                 vma = NULL;
2123         else
2124                 vma = find_vma(mm, khugepaged_scan.address);
2125
2126         progress++;
2127         for (; vma; vma = vma->vm_next) {
2128                 unsigned long hstart, hend;
2129
2130                 cond_resched();
2131                 if (unlikely(khugepaged_test_exit(mm))) {
2132                         progress++;
2133                         break;
2134                 }
2135
2136                 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2137                      !khugepaged_always()) ||
2138                     (vma->vm_flags & VM_NOHUGEPAGE)) {
2139                 skip:
2140                         progress++;
2141                         continue;
2142                 }
2143                 if (!vma->anon_vma || vma->vm_ops)
2144                         goto skip;
2145                 if (is_vma_temporary_stack(vma))
2146                         goto skip;
2147                 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2148
2149                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2150                 hend = vma->vm_end & HPAGE_PMD_MASK;
2151                 if (hstart >= hend)
2152                         goto skip;
2153                 if (khugepaged_scan.address > hend)
2154                         goto skip;
2155                 if (khugepaged_scan.address < hstart)
2156                         khugepaged_scan.address = hstart;
2157                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2158
2159                 while (khugepaged_scan.address < hend) {
2160                         int ret;
2161                         cond_resched();
2162                         if (unlikely(khugepaged_test_exit(mm)))
2163                                 goto breakouterloop;
2164
2165                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2166                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2167                                   hend);
2168                         ret = khugepaged_scan_pmd(mm, vma,
2169                                                   khugepaged_scan.address,
2170                                                   hpage);
2171                         /* move to next address */
2172                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2173                         progress += HPAGE_PMD_NR;
2174                         if (ret)
2175                                 /* we released mmap_sem so break loop */
2176                                 goto breakouterloop_mmap_sem;
2177                         if (progress >= pages)
2178                                 goto breakouterloop;
2179                 }
2180         }
2181 breakouterloop:
2182         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2183 breakouterloop_mmap_sem:
2184
2185         spin_lock(&khugepaged_mm_lock);
2186         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2187         /*
2188          * Release the current mm_slot if this mm is about to die, or
2189          * if we scanned all vmas of this mm.
2190          */
2191         if (khugepaged_test_exit(mm) || !vma) {
2192                 /*
2193                  * Make sure that if mm_users is reaching zero while
2194                  * khugepaged runs here, khugepaged_exit will find
2195                  * mm_slot not pointing to the exiting mm.
2196                  */
2197                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2198                         khugepaged_scan.mm_slot = list_entry(
2199                                 mm_slot->mm_node.next,
2200                                 struct mm_slot, mm_node);
2201                         khugepaged_scan.address = 0;
2202                 } else {
2203                         khugepaged_scan.mm_slot = NULL;
2204                         khugepaged_full_scans++;
2205                 }
2206
2207                 collect_mm_slot(mm_slot);
2208         }
2209
2210         return progress;
2211 }
2212
2213 static int khugepaged_has_work(void)
2214 {
2215         return !list_empty(&khugepaged_scan.mm_head) &&
2216                 khugepaged_enabled();
2217 }
2218
2219 static int khugepaged_wait_event(void)
2220 {
2221         return !list_empty(&khugepaged_scan.mm_head) ||
2222                 kthread_should_stop();
2223 }
2224
2225 static void khugepaged_do_scan(struct page **hpage)
2226 {
2227         unsigned int progress = 0, pass_through_head = 0;
2228         unsigned int pages = khugepaged_pages_to_scan;
2229
2230         barrier(); /* write khugepaged_pages_to_scan to local stack */
2231
2232         while (progress < pages) {
2233                 cond_resched();
2234
2235 #ifndef CONFIG_NUMA
2236                 if (!*hpage) {
2237                         *hpage = alloc_hugepage(khugepaged_defrag());
2238                         if (unlikely(!*hpage)) {
2239                                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2240                                 break;
2241                         }
2242                         count_vm_event(THP_COLLAPSE_ALLOC);
2243                 }
2244 #else
2245                 if (IS_ERR(*hpage))
2246                         break;
2247 #endif
2248
2249                 if (unlikely(kthread_should_stop() || freezing(current)))
2250                         break;
2251
2252                 spin_lock(&khugepaged_mm_lock);
2253                 if (!khugepaged_scan.mm_slot)
2254                         pass_through_head++;
2255                 if (khugepaged_has_work() &&
2256                     pass_through_head < 2)
2257                         progress += khugepaged_scan_mm_slot(pages - progress,
2258                                                             hpage);
2259                 else
2260                         progress = pages;
2261                 spin_unlock(&khugepaged_mm_lock);
2262         }
2263 }
2264
2265 static void khugepaged_alloc_sleep(void)
2266 {
2267         wait_event_freezable_timeout(khugepaged_wait, false,
2268                         msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2269 }
2270
2271 #ifndef CONFIG_NUMA
2272 static struct page *khugepaged_alloc_hugepage(void)
2273 {
2274         struct page *hpage;
2275
2276         do {
2277                 hpage = alloc_hugepage(khugepaged_defrag());
2278                 if (!hpage) {
2279                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2280                         khugepaged_alloc_sleep();
2281                 } else
2282                         count_vm_event(THP_COLLAPSE_ALLOC);
2283         } while (unlikely(!hpage) &&
2284                  likely(khugepaged_enabled()));
2285         return hpage;
2286 }
2287 #endif
2288
2289 static void khugepaged_wait_work(void)
2290 {
2291         try_to_freeze();
2292
2293         if (khugepaged_has_work()) {
2294                 if (!khugepaged_scan_sleep_millisecs)
2295                         return;
2296
2297                 wait_event_freezable_timeout(khugepaged_wait,
2298                                              kthread_should_stop(),
2299                         msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2300                 return;
2301         }
2302
2303         if (khugepaged_enabled())
2304                 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2305 }
2306
2307 static void khugepaged_loop(void)
2308 {
2309         struct page *hpage = NULL;
2310
2311         while (likely(khugepaged_enabled())) {
2312 #ifndef CONFIG_NUMA
2313                 hpage = khugepaged_alloc_hugepage();
2314                 if (unlikely(!hpage))
2315                         break;
2316 #else
2317                 if (IS_ERR(hpage)) {
2318                         khugepaged_alloc_sleep();
2319                         hpage = NULL;
2320                 }
2321 #endif
2322
2323                 khugepaged_do_scan(&hpage);
2324
2325                 if (!IS_ERR_OR_NULL(hpage))
2326                         put_page(hpage);
2327
2328                 khugepaged_wait_work();
2329         }
2330 }
2331
2332 static int khugepaged(void *none)
2333 {
2334         struct mm_slot *mm_slot;
2335
2336         set_freezable();
2337         set_user_nice(current, 19);
2338
2339         while (!kthread_should_stop())
2340                 khugepaged_loop();
2341
2342         spin_lock(&khugepaged_mm_lock);
2343         mm_slot = khugepaged_scan.mm_slot;
2344         khugepaged_scan.mm_slot = NULL;
2345         if (mm_slot)
2346                 collect_mm_slot(mm_slot);
2347         spin_unlock(&khugepaged_mm_lock);
2348         return 0;
2349 }
2350
2351 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2352 {
2353         struct page *page;
2354
2355         spin_lock(&mm->page_table_lock);
2356         if (unlikely(!pmd_trans_huge(*pmd))) {
2357                 spin_unlock(&mm->page_table_lock);
2358                 return;
2359         }
2360         page = pmd_page(*pmd);
2361         VM_BUG_ON(!page_count(page));
2362         get_page(page);
2363         spin_unlock(&mm->page_table_lock);
2364
2365         split_huge_page(page);
2366
2367         put_page(page);
2368         BUG_ON(pmd_trans_huge(*pmd));
2369 }
2370
2371 static void split_huge_page_address(struct mm_struct *mm,
2372                                     unsigned long address)
2373 {
2374         pgd_t *pgd;
2375         pud_t *pud;
2376         pmd_t *pmd;
2377
2378         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2379
2380         pgd = pgd_offset(mm, address);
2381         if (!pgd_present(*pgd))
2382                 return;
2383
2384         pud = pud_offset(pgd, address);
2385         if (!pud_present(*pud))
2386                 return;
2387
2388         pmd = pmd_offset(pud, address);
2389         if (!pmd_present(*pmd))
2390                 return;
2391         /*
2392          * Caller holds the mmap_sem write mode, so a huge pmd cannot
2393          * materialize from under us.
2394          */
2395         split_huge_page_pmd(mm, pmd);
2396 }
2397
2398 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2399                              unsigned long start,
2400                              unsigned long end,
2401                              long adjust_next)
2402 {
2403         /*
2404          * If the new start address isn't hpage aligned and it could
2405          * previously contain an hugepage: check if we need to split
2406          * an huge pmd.
2407          */
2408         if (start & ~HPAGE_PMD_MASK &&
2409             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2410             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2411                 split_huge_page_address(vma->vm_mm, start);
2412
2413         /*
2414          * If the new end address isn't hpage aligned and it could
2415          * previously contain an hugepage: check if we need to split
2416          * an huge pmd.
2417          */
2418         if (end & ~HPAGE_PMD_MASK &&
2419             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2420             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2421                 split_huge_page_address(vma->vm_mm, end);
2422
2423         /*
2424          * If we're also updating the vma->vm_next->vm_start, if the new
2425          * vm_next->vm_start isn't page aligned and it could previously
2426          * contain an hugepage: check if we need to split an huge pmd.
2427          */
2428         if (adjust_next > 0) {
2429                 struct vm_area_struct *next = vma->vm_next;
2430                 unsigned long nstart = next->vm_start;
2431                 nstart += adjust_next << PAGE_SHIFT;
2432                 if (nstart & ~HPAGE_PMD_MASK &&
2433                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2434                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2435                         split_huge_page_address(next->vm_mm, nstart);
2436         }
2437 }