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