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