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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/mm.h>
  11 #include <linux/sched.h>
  12 #include <linux/highmem.h>
  13 #include <linux/hugetlb.h>
  14 #include <linux/mmu_notifier.h>
  15 #include <linux/rmap.h>
  16 #include <linux/swap.h>
  17 #include <linux/shrinker.h>
  18 #include <linux/mm_inline.h>
  19 #include <linux/dax.h>
  20 #include <linux/kthread.h>
  21 #include <linux/khugepaged.h>
  22 #include <linux/freezer.h>
  23 #include <linux/mman.h>
  24 #include <linux/pagemap.h>
  25 #include <linux/migrate.h>
  26 #include <linux/hashtable.h>
  27 #include <linux/userfaultfd_k.h>
  28 #include <linux/page_idle.h>
  29
  30 #include <asm/tlb.h>
  31 #include <asm/pgalloc.h>
  32 #include "internal.h"
  33
  34 /*
  35  * By default transparent hugepage support is disabled in order that avoid
  36  * to risk increase the memory footprint of applications without a guaranteed
  37  * benefit. When transparent hugepage support is enabled, is for all mappings,
  38  * and khugepaged scans all mappings.
  39  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  40  * for all hugepage allocations.
  41  */
  42 unsigned long transparent_hugepage_flags __read_mostly =
  43 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  44         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  45 #endif
  46 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  47         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  48 #endif
  49         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
  50         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  51         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  52
  53 /* default scan 8*512 pte (or vmas) every 30 second */
  54 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
  55 static unsigned int khugepaged_pages_collapsed;
  56 static unsigned int khugepaged_full_scans;
  57 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  58 /* during fragmentation poll the hugepage allocator once every minute */
  59 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  60 static struct task_struct *khugepaged_thread __read_mostly;
  61 static DEFINE_MUTEX(khugepaged_mutex);
  62 static DEFINE_SPINLOCK(khugepaged_mm_lock);
  63 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  64 /*
  65  * default collapse hugepages if there is at least one pte mapped like
  66  * it would have happened if the vma was large enough during page
  67  * fault.
  68  */
  69 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
  70
  71 static int khugepaged(void *none);
  72 static int khugepaged_slab_init(void);
  73 static void khugepaged_slab_exit(void);
  74
  75 #define MM_SLOTS_HASH_BITS 10
  76 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
  77
  78 static struct kmem_cache *mm_slot_cache __read_mostly;
  79
  80 /**
  81  * struct mm_slot - hash lookup from mm to mm_slot
  82  * @hash: hash collision list
  83  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
  84  * @mm: the mm that this information is valid for
  85  */
  86 struct mm_slot {
  87         struct hlist_node hash;
  88         struct list_head mm_node;
  89         struct mm_struct *mm;
  90 };
  91
  92 /**
  93  * struct khugepaged_scan - cursor for scanning
  94  * @mm_head: the head of the mm list to scan
  95  * @mm_slot: the current mm_slot we are scanning
  96  * @address: the next address inside that to be scanned
  97  *
  98  * There is only the one khugepaged_scan instance of this cursor structure.
  99  */
 100 struct khugepaged_scan {
 101         struct list_head mm_head;
 102         struct mm_slot *mm_slot;
 103         unsigned long address;
 104 };
 105 static struct khugepaged_scan khugepaged_scan = {
 106         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
 107 };
 108
 109
 110 static void set_recommended_min_free_kbytes(void)
 111 {
 112         struct zone *zone;
 113         int nr_zones = 0;
 114         unsigned long recommended_min;
 115
 116         for_each_populated_zone(zone)
 117                 nr_zones++;
 118
 119         /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
 120         recommended_min = pageblock_nr_pages * nr_zones * 2;
 121
 122         /*
 123          * Make sure that on average at least two pageblocks are almost free
 124          * of another type, one for a migratetype to fall back to and a
 125          * second to avoid subsequent fallbacks of other types There are 3
 126          * MIGRATE_TYPES we care about.
 127          */
 128         recommended_min += pageblock_nr_pages * nr_zones *
 129                            MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
 130
 131         /* don't ever allow to reserve more than 5% of the lowmem */
 132         recommended_min = min(recommended_min,
 133                               (unsigned long) nr_free_buffer_pages() / 20);
 134         recommended_min <<= (PAGE_SHIFT-10);
 135
 136         if (recommended_min > min_free_kbytes) {
 137                 if (user_min_free_kbytes >= 0)
 138                         pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
 139                                 min_free_kbytes, recommended_min);
 140
 141                 min_free_kbytes = recommended_min;
 142         }
 143         setup_per_zone_wmarks();
 144 }
 145
 146 static int start_stop_khugepaged(void)
 147 {
 148         int err = 0;
 149         if (khugepaged_enabled()) {
 150                 if (!khugepaged_thread)
 151                         khugepaged_thread = kthread_run(khugepaged, NULL,
 152                                                         "khugepaged");
 153                 if (IS_ERR(khugepaged_thread)) {
 154                         pr_err("khugepaged: kthread_run(khugepaged) failed\n");
 155                         err = PTR_ERR(khugepaged_thread);
 156                         khugepaged_thread = NULL;
 157                         goto fail;
 158                 }
 159
 160                 if (!list_empty(&khugepaged_scan.mm_head))
 161                         wake_up_interruptible(&khugepaged_wait);
 162
 163                 set_recommended_min_free_kbytes();
 164         } else if (khugepaged_thread) {
 165                 kthread_stop(khugepaged_thread);
 166                 khugepaged_thread = NULL;
 167         }
 168 fail:
 169         return err;
 170 }
 171
 172 static atomic_t huge_zero_refcount;
 173 struct page *huge_zero_page __read_mostly;
 174
 175 struct page *get_huge_zero_page(void)
 176 {
 177         struct page *zero_page;
 178 retry:
 179         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 180                 return READ_ONCE(huge_zero_page);
 181
 182         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 183                         HPAGE_PMD_ORDER);
 184         if (!zero_page) {
 185                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 186                 return NULL;
 187         }
 188         count_vm_event(THP_ZERO_PAGE_ALLOC);
 189         preempt_disable();
 190         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 191                 preempt_enable();
 192                 __free_pages(zero_page, compound_order(zero_page));
 193                 goto retry;
 194         }
 195
 196         /* We take additional reference here. It will be put back by shrinker */
 197         atomic_set(&huge_zero_refcount, 2);
 198         preempt_enable();
 199         return READ_ONCE(huge_zero_page);
 200 }
 201
 202 static void put_huge_zero_page(void)
 203 {
 204         /*
 205          * Counter should never go to zero here. Only shrinker can put
 206          * last reference.
 207          */
 208         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 209 }
 210
 211 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 212                                         struct shrink_control *sc)
 213 {
 214         /* we can free zero page only if last reference remains */
 215         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 216 }
 217
 218 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 219                                        struct shrink_control *sc)
 220 {
 221         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 222                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 223                 BUG_ON(zero_page == NULL);
 224                 __free_pages(zero_page, compound_order(zero_page));
 225                 return HPAGE_PMD_NR;
 226         }
 227
 228         return 0;
 229 }
 230
 231 static struct shrinker huge_zero_page_shrinker = {
 232         .count_objects = shrink_huge_zero_page_count,
 233         .scan_objects = shrink_huge_zero_page_scan,
 234         .seeks = DEFAULT_SEEKS,
 235 };
 236
 237 #ifdef CONFIG_SYSFS
 238
 239 static ssize_t double_flag_show(struct kobject *kobj,
 240                                 struct kobj_attribute *attr, char *buf,
 241                                 enum transparent_hugepage_flag enabled,
 242                                 enum transparent_hugepage_flag req_madv)
 243 {
 244         if (test_bit(enabled, &transparent_hugepage_flags)) {
 245                 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
 246                 return sprintf(buf, "[always] madvise never\n");
 247         } else if (test_bit(req_madv, &transparent_hugepage_flags))
 248                 return sprintf(buf, "always [madvise] never\n");
 249         else
 250                 return sprintf(buf, "always madvise [never]\n");
 251 }
 252 static ssize_t double_flag_store(struct kobject *kobj,
 253                                  struct kobj_attribute *attr,
 254                                  const char *buf, size_t count,
 255                                  enum transparent_hugepage_flag enabled,
 256                                  enum transparent_hugepage_flag req_madv)
 257 {
 258         if (!memcmp("always", buf,
 259                     min(sizeof("always")-1, count))) {
 260                 set_bit(enabled, &transparent_hugepage_flags);
 261                 clear_bit(req_madv, &transparent_hugepage_flags);
 262         } else if (!memcmp("madvise", buf,
 263                            min(sizeof("madvise")-1, count))) {
 264                 clear_bit(enabled, &transparent_hugepage_flags);
 265                 set_bit(req_madv, &transparent_hugepage_flags);
 266         } else if (!memcmp("never", buf,
 267                            min(sizeof("never")-1, count))) {
 268                 clear_bit(enabled, &transparent_hugepage_flags);
 269                 clear_bit(req_madv, &transparent_hugepage_flags);
 270         } else
 271                 return -EINVAL;
 272
 273         return count;
 274 }
 275
 276 static ssize_t enabled_show(struct kobject *kobj,
 277                             struct kobj_attribute *attr, char *buf)
 278 {
 279         return double_flag_show(kobj, attr, buf,
 280                                 TRANSPARENT_HUGEPAGE_FLAG,
 281                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 282 }
 283 static ssize_t enabled_store(struct kobject *kobj,
 284                              struct kobj_attribute *attr,
 285                              const char *buf, size_t count)
 286 {
 287         ssize_t ret;
 288
 289         ret = double_flag_store(kobj, attr, buf, count,
 290                                 TRANSPARENT_HUGEPAGE_FLAG,
 291                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 292
 293         if (ret > 0) {
 294                 int err;
 295
 296                 mutex_lock(&khugepaged_mutex);
 297                 err = start_stop_khugepaged();
 298                 mutex_unlock(&khugepaged_mutex);
 299
 300                 if (err)
 301                         ret = err;
 302         }
 303
 304         return ret;
 305 }
 306 static struct kobj_attribute enabled_attr =
 307         __ATTR(enabled, 0644, enabled_show, enabled_store);
 308
 309 static ssize_t single_flag_show(struct kobject *kobj,
 310                                 struct kobj_attribute *attr, char *buf,
 311                                 enum transparent_hugepage_flag flag)
 312 {
 313         return sprintf(buf, "%d\n",
 314                        !!test_bit(flag, &transparent_hugepage_flags));
 315 }
 316
 317 static ssize_t single_flag_store(struct kobject *kobj,
 318                                  struct kobj_attribute *attr,
 319                                  const char *buf, size_t count,
 320                                  enum transparent_hugepage_flag flag)
 321 {
 322         unsigned long value;
 323         int ret;
 324
 325         ret = kstrtoul(buf, 10, &value);
 326         if (ret < 0)
 327                 return ret;
 328         if (value > 1)
 329                 return -EINVAL;
 330
 331         if (value)
 332                 set_bit(flag, &transparent_hugepage_flags);
 333         else
 334                 clear_bit(flag, &transparent_hugepage_flags);
 335
 336         return count;
 337 }
 338
 339 /*
 340  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 341  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 342  * memory just to allocate one more hugepage.
 343  */
 344 static ssize_t defrag_show(struct kobject *kobj,
 345                            struct kobj_attribute *attr, char *buf)
 346 {
 347         return double_flag_show(kobj, attr, buf,
 348                                 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 349                                 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 350 }
 351 static ssize_t defrag_store(struct kobject *kobj,
 352                             struct kobj_attribute *attr,
 353                             const char *buf, size_t count)
 354 {
 355         return double_flag_store(kobj, attr, buf, count,
 356                                  TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
 357                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 358 }
 359 static struct kobj_attribute defrag_attr =
 360         __ATTR(defrag, 0644, defrag_show, defrag_store);
 361
 362 static ssize_t use_zero_page_show(struct kobject *kobj,
 363                 struct kobj_attribute *attr, char *buf)
 364 {
 365         return single_flag_show(kobj, attr, buf,
 366                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 367 }
 368 static ssize_t use_zero_page_store(struct kobject *kobj,
 369                 struct kobj_attribute *attr, const char *buf, size_t count)
 370 {
 371         return single_flag_store(kobj, attr, buf, count,
 372                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 373 }
 374 static struct kobj_attribute use_zero_page_attr =
 375         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 376 #ifdef CONFIG_DEBUG_VM
 377 static ssize_t debug_cow_show(struct kobject *kobj,
 378                                 struct kobj_attribute *attr, char *buf)
 379 {
 380         return single_flag_show(kobj, attr, buf,
 381                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 382 }
 383 static ssize_t debug_cow_store(struct kobject *kobj,
 384                                struct kobj_attribute *attr,
 385                                const char *buf, size_t count)
 386 {
 387         return single_flag_store(kobj, attr, buf, count,
 388                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 389 }
 390 static struct kobj_attribute debug_cow_attr =
 391         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 392 #endif /* CONFIG_DEBUG_VM */
 393
 394 static struct attribute *hugepage_attr[] = {
 395         &enabled_attr.attr,
 396         &defrag_attr.attr,
 397         &use_zero_page_attr.attr,
 398 #ifdef CONFIG_DEBUG_VM
 399         &debug_cow_attr.attr,
 400 #endif
 401         NULL,
 402 };
 403
 404 static struct attribute_group hugepage_attr_group = {
 405         .attrs = hugepage_attr,
 406 };
 407
 408 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 409                                          struct kobj_attribute *attr,
 410                                          char *buf)
 411 {
 412         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 413 }
 414
 415 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 416                                           struct kobj_attribute *attr,
 417                                           const char *buf, size_t count)
 418 {
 419         unsigned long msecs;
 420         int err;
 421
 422         err = kstrtoul(buf, 10, &msecs);
 423         if (err || msecs > UINT_MAX)
 424                 return -EINVAL;
 425
 426         khugepaged_scan_sleep_millisecs = msecs;
 427         wake_up_interruptible(&khugepaged_wait);
 428
 429         return count;
 430 }
 431 static struct kobj_attribute scan_sleep_millisecs_attr =
 432         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 433                scan_sleep_millisecs_store);
 434
 435 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 436                                           struct kobj_attribute *attr,
 437                                           char *buf)
 438 {
 439         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 440 }
 441
 442 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 443                                            struct kobj_attribute *attr,
 444                                            const char *buf, size_t count)
 445 {
 446         unsigned long msecs;
 447         int err;
 448
 449         err = kstrtoul(buf, 10, &msecs);
 450         if (err || msecs > UINT_MAX)
 451                 return -EINVAL;
 452
 453         khugepaged_alloc_sleep_millisecs = msecs;
 454         wake_up_interruptible(&khugepaged_wait);
 455
 456         return count;
 457 }
 458 static struct kobj_attribute alloc_sleep_millisecs_attr =
 459         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 460                alloc_sleep_millisecs_store);
 461
 462 static ssize_t pages_to_scan_show(struct kobject *kobj,
 463                                   struct kobj_attribute *attr,
 464                                   char *buf)
 465 {
 466         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 467 }
 468 static ssize_t pages_to_scan_store(struct kobject *kobj,
 469                                    struct kobj_attribute *attr,
 470                                    const char *buf, size_t count)
 471 {
 472         int err;
 473         unsigned long pages;
 474
 475         err = kstrtoul(buf, 10, &pages);
 476         if (err || !pages || pages > UINT_MAX)
 477                 return -EINVAL;
 478
 479         khugepaged_pages_to_scan = pages;
 480
 481         return count;
 482 }
 483 static struct kobj_attribute pages_to_scan_attr =
 484         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 485                pages_to_scan_store);
 486
 487 static ssize_t pages_collapsed_show(struct kobject *kobj,
 488                                     struct kobj_attribute *attr,
 489                                     char *buf)
 490 {
 491         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 492 }
 493 static struct kobj_attribute pages_collapsed_attr =
 494         __ATTR_RO(pages_collapsed);
 495
 496 static ssize_t full_scans_show(struct kobject *kobj,
 497                                struct kobj_attribute *attr,
 498                                char *buf)
 499 {
 500         return sprintf(buf, "%u\n", khugepaged_full_scans);
 501 }
 502 static struct kobj_attribute full_scans_attr =
 503         __ATTR_RO(full_scans);
 504
 505 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 506                                       struct kobj_attribute *attr, char *buf)
 507 {
 508         return single_flag_show(kobj, attr, buf,
 509                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 510 }
 511 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 512                                        struct kobj_attribute *attr,
 513                                        const char *buf, size_t count)
 514 {
 515         return single_flag_store(kobj, attr, buf, count,
 516                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 517 }
 518 static struct kobj_attribute khugepaged_defrag_attr =
 519         __ATTR(defrag, 0644, khugepaged_defrag_show,
 520                khugepaged_defrag_store);
 521
 522 /*
 523  * max_ptes_none controls if khugepaged should collapse hugepages over
 524  * any unmapped ptes in turn potentially increasing the memory
 525  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 526  * reduce the available free memory in the system as it
 527  * runs. Increasing max_ptes_none will instead potentially reduce the
 528  * free memory in the system during the khugepaged scan.
 529  */
 530 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 531                                              struct kobj_attribute *attr,
 532                                              char *buf)
 533 {
 534         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 535 }
 536 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 537                                               struct kobj_attribute *attr,
 538                                               const char *buf, size_t count)
 539 {
 540         int err;
 541         unsigned long max_ptes_none;
 542
 543         err = kstrtoul(buf, 10, &max_ptes_none);
 544         if (err || max_ptes_none > HPAGE_PMD_NR-1)
 545                 return -EINVAL;
 546
 547         khugepaged_max_ptes_none = max_ptes_none;
 548
 549         return count;
 550 }
 551 static struct kobj_attribute khugepaged_max_ptes_none_attr =
 552         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 553                khugepaged_max_ptes_none_store);
 554
 555 static struct attribute *khugepaged_attr[] = {
 556         &khugepaged_defrag_attr.attr,
 557         &khugepaged_max_ptes_none_attr.attr,
 558         &pages_to_scan_attr.attr,
 559         &pages_collapsed_attr.attr,
 560         &full_scans_attr.attr,
 561         &scan_sleep_millisecs_attr.attr,
 562         &alloc_sleep_millisecs_attr.attr,
 563         NULL,
 564 };
 565
 566 static struct attribute_group khugepaged_attr_group = {
 567         .attrs = khugepaged_attr,
 568         .name = "khugepaged",
 569 };
 570
 571 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 572 {
 573         int err;
 574
 575         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 576         if (unlikely(!*hugepage_kobj)) {
 577                 pr_err("failed to create transparent hugepage kobject\n");
 578                 return -ENOMEM;
 579         }
 580
 581         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 582         if (err) {
 583                 pr_err("failed to register transparent hugepage group\n");
 584                 goto delete_obj;
 585         }
 586
 587         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 588         if (err) {
 589                 pr_err("failed to register transparent hugepage group\n");
 590                 goto remove_hp_group;
 591         }
 592
 593         return 0;
 594
 595 remove_hp_group:
 596         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 597 delete_obj:
 598         kobject_put(*hugepage_kobj);
 599         return err;
 600 }
 601
 602 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 603 {
 604         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 605         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 606         kobject_put(hugepage_kobj);
 607 }
 608 #else
 609 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 610 {
 611         return 0;
 612 }
 613
 614 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 615 {
 616 }
 617 #endif /* CONFIG_SYSFS */
 618
 619 static int __init hugepage_init(void)
 620 {
 621         int err;
 622         struct kobject *hugepage_kobj;
 623
 624         if (!has_transparent_hugepage()) {
 625                 transparent_hugepage_flags = 0;
 626                 return -EINVAL;
 627         }
 628
 629         err = hugepage_init_sysfs(&hugepage_kobj);
 630         if (err)
 631                 goto err_sysfs;
 632
 633         err = khugepaged_slab_init();
 634         if (err)
 635                 goto err_slab;
 636
 637         err = register_shrinker(&huge_zero_page_shrinker);
 638         if (err)
 639                 goto err_hzp_shrinker;
 640
 641         /*
 642          * By default disable transparent hugepages on smaller systems,
 643          * where the extra memory used could hurt more than TLB overhead
 644          * is likely to save.  The admin can still enable it through /sys.
 645          */
 646         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
 647                 transparent_hugepage_flags = 0;
 648                 return 0;
 649         }
 650
 651         err = start_stop_khugepaged();
 652         if (err)
 653                 goto err_khugepaged;
 654
 655         return 0;
 656 err_khugepaged:
 657         unregister_shrinker(&huge_zero_page_shrinker);
 658 err_hzp_shrinker:
 659         khugepaged_slab_exit();
 660 err_slab:
 661         hugepage_exit_sysfs(hugepage_kobj);
 662 err_sysfs:
 663         return err;
 664 }
 665 subsys_initcall(hugepage_init);
 666
 667 static int __init setup_transparent_hugepage(char *str)
 668 {
 669         int ret = 0;
 670         if (!str)
 671                 goto out;
 672         if (!strcmp(str, "always")) {
 673                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 674                         &transparent_hugepage_flags);
 675                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 676                           &transparent_hugepage_flags);
 677                 ret = 1;
 678         } else if (!strcmp(str, "madvise")) {
 679                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 680                           &transparent_hugepage_flags);
 681                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 682                         &transparent_hugepage_flags);
 683                 ret = 1;
 684         } else if (!strcmp(str, "never")) {
 685                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 686                           &transparent_hugepage_flags);
 687                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 688                           &transparent_hugepage_flags);
 689                 ret = 1;
 690         }
 691 out:
 692         if (!ret)
 693                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 694         return ret;
 695 }
 696 __setup("transparent_hugepage=", setup_transparent_hugepage);
 697
 698 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 699 {
 700         if (likely(vma->vm_flags & VM_WRITE))
 701                 pmd = pmd_mkwrite(pmd);
 702         return pmd;
 703 }
 704
 705 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
 706 {
 707         pmd_t entry;
 708         entry = mk_pmd(page, prot);
 709         entry = pmd_mkhuge(entry);
 710         return entry;
 711 }
 712
 713 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 714                                         struct vm_area_struct *vma,
 715                                         unsigned long address, pmd_t *pmd,
 716                                         struct page *page, gfp_t gfp,
 717                                         unsigned int flags)
 718 {
 719         struct mem_cgroup *memcg;
 720         pgtable_t pgtable;
 721         spinlock_t *ptl;
 722         unsigned long haddr = address & HPAGE_PMD_MASK;
 723
 724         VM_BUG_ON_PAGE(!PageCompound(page), page);
 725
 726         if (mem_cgroup_try_charge(page, mm, gfp, &memcg)) {
 727                 put_page(page);
 728                 count_vm_event(THP_FAULT_FALLBACK);
 729                 return VM_FAULT_FALLBACK;
 730         }
 731
 732         pgtable = pte_alloc_one(mm, haddr);
 733         if (unlikely(!pgtable)) {
 734                 mem_cgroup_cancel_charge(page, memcg);
 735                 put_page(page);
 736                 return VM_FAULT_OOM;
 737         }
 738
 739         clear_huge_page(page, haddr, HPAGE_PMD_NR);
 740         /*
 741          * The memory barrier inside __SetPageUptodate makes sure that
 742          * clear_huge_page writes become visible before the set_pmd_at()
 743          * write.
 744          */
 745         __SetPageUptodate(page);
 746
 747         ptl = pmd_lock(mm, pmd);
 748         if (unlikely(!pmd_none(*pmd))) {
 749                 spin_unlock(ptl);
 750                 mem_cgroup_cancel_charge(page, memcg);
 751                 put_page(page);
 752                 pte_free(mm, pgtable);
 753         } else {
 754                 pmd_t entry;
 755
 756                 /* Deliver the page fault to userland */
 757                 if (userfaultfd_missing(vma)) {
 758                         int ret;
 759
 760                         spin_unlock(ptl);
 761                         mem_cgroup_cancel_charge(page, memcg);
 762                         put_page(page);
 763                         pte_free(mm, pgtable);
 764                         ret = handle_userfault(vma, address, flags,
 765                                                VM_UFFD_MISSING);
 766                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 767                         return ret;
 768                 }
 769
 770                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 771                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 772                 page_add_new_anon_rmap(page, vma, haddr);
 773                 mem_cgroup_commit_charge(page, memcg, false);
 774                 lru_cache_add_active_or_unevictable(page, vma);
 775                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 776                 set_pmd_at(mm, haddr, pmd, entry);
 777                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 778                 atomic_long_inc(&mm->nr_ptes);
 779                 spin_unlock(ptl);
 780                 count_vm_event(THP_FAULT_ALLOC);
 781         }
 782
 783         return 0;
 784 }
 785
 786 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 787 {
 788         return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_RECLAIM)) | extra_gfp;
 789 }
 790
 791 /* Caller must hold page table lock. */
 792 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 793                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 794                 struct page *zero_page)
 795 {
 796         pmd_t entry;
 797         if (!pmd_none(*pmd))
 798                 return false;
 799         entry = mk_pmd(zero_page, vma->vm_page_prot);
 800         entry = pmd_mkhuge(entry);
 801         pgtable_trans_huge_deposit(mm, pmd, pgtable);
 802         set_pmd_at(mm, haddr, pmd, entry);
 803         atomic_long_inc(&mm->nr_ptes);
 804         return true;
 805 }
 806
 807 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 808                                unsigned long address, pmd_t *pmd,
 809                                unsigned int flags)
 810 {
 811         gfp_t gfp;
 812         struct page *page;
 813         unsigned long haddr = address & HPAGE_PMD_MASK;
 814
 815         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 816                 return VM_FAULT_FALLBACK;
 817         if (unlikely(anon_vma_prepare(vma)))
 818                 return VM_FAULT_OOM;
 819         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 820                 return VM_FAULT_OOM;
 821         if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
 822                         transparent_hugepage_use_zero_page()) {
 823                 spinlock_t *ptl;
 824                 pgtable_t pgtable;
 825                 struct page *zero_page;
 826                 bool set;
 827                 int ret;
 828                 pgtable = pte_alloc_one(mm, haddr);
 829                 if (unlikely(!pgtable))
 830                         return VM_FAULT_OOM;
 831                 zero_page = get_huge_zero_page();
 832                 if (unlikely(!zero_page)) {
 833                         pte_free(mm, pgtable);
 834                         count_vm_event(THP_FAULT_FALLBACK);
 835                         return VM_FAULT_FALLBACK;
 836                 }
 837                 ptl = pmd_lock(mm, pmd);
 838                 ret = 0;
 839                 set = false;
 840                 if (pmd_none(*pmd)) {
 841                         if (userfaultfd_missing(vma)) {
 842                                 spin_unlock(ptl);
 843                                 ret = handle_userfault(vma, address, flags,
 844                                                        VM_UFFD_MISSING);
 845                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 846                         } else {
 847                                 set_huge_zero_page(pgtable, mm, vma,
 848                                                    haddr, pmd,
 849                                                    zero_page);
 850                                 spin_unlock(ptl);
 851                                 set = true;
 852                         }
 853                 } else
 854                         spin_unlock(ptl);
 855                 if (!set) {
 856                         pte_free(mm, pgtable);
 857                         put_huge_zero_page();
 858                 }
 859                 return ret;
 860         }
 861         gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
 862         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 863         if (unlikely(!page)) {
 864                 count_vm_event(THP_FAULT_FALLBACK);
 865                 return VM_FAULT_FALLBACK;
 866         }
 867         return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
 868                                             flags);
 869 }
 870
 871 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 872                 pmd_t *pmd, unsigned long pfn, pgprot_t prot, bool write)
 873 {
 874         struct mm_struct *mm = vma->vm_mm;
 875         pmd_t entry;
 876         spinlock_t *ptl;
 877
 878         ptl = pmd_lock(mm, pmd);
 879         if (pmd_none(*pmd)) {
 880                 entry = pmd_mkhuge(pfn_pmd(pfn, prot));
 881                 if (write) {
 882                         entry = pmd_mkyoung(pmd_mkdirty(entry));
 883                         entry = maybe_pmd_mkwrite(entry, vma);
 884                 }
 885                 set_pmd_at(mm, addr, pmd, entry);
 886                 update_mmu_cache_pmd(vma, addr, pmd);
 887         }
 888         spin_unlock(ptl);
 889 }
 890
 891 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 892                         pmd_t *pmd, unsigned long pfn, bool write)
 893 {
 894         pgprot_t pgprot = vma->vm_page_prot;
 895         /*
 896          * If we had pmd_special, we could avoid all these restrictions,
 897          * but we need to be consistent with PTEs and architectures that
 898          * can't support a 'special' bit.
 899          */
 900         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
 901         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 902                                                 (VM_PFNMAP|VM_MIXEDMAP));
 903         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 904         BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
 905
 906         if (addr < vma->vm_start || addr >= vma->vm_end)
 907                 return VM_FAULT_SIGBUS;
 908         if (track_pfn_insert(vma, &pgprot, pfn))
 909                 return VM_FAULT_SIGBUS;
 910         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
 911         return VM_FAULT_NOPAGE;
 912 }
 913
 914 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 915                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 916                   struct vm_area_struct *vma)
 917 {
 918         spinlock_t *dst_ptl, *src_ptl;
 919         struct page *src_page;
 920         pmd_t pmd;
 921         pgtable_t pgtable;
 922         int ret;
 923
 924         ret = -ENOMEM;
 925         pgtable = pte_alloc_one(dst_mm, addr);
 926         if (unlikely(!pgtable))
 927                 goto out;
 928
 929         dst_ptl = pmd_lock(dst_mm, dst_pmd);
 930         src_ptl = pmd_lockptr(src_mm, src_pmd);
 931         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 932
 933         ret = -EAGAIN;
 934         pmd = *src_pmd;
 935         if (unlikely(!pmd_trans_huge(pmd))) {
 936                 pte_free(dst_mm, pgtable);
 937                 goto out_unlock;
 938         }
 939         /*
 940          * When page table lock is held, the huge zero pmd should not be
 941          * under splitting since we don't split the page itself, only pmd to
 942          * a page table.
 943          */
 944         if (is_huge_zero_pmd(pmd)) {
 945                 struct page *zero_page;
 946                 /*
 947                  * get_huge_zero_page() will never allocate a new page here,
 948                  * since we already have a zero page to copy. It just takes a
 949                  * reference.
 950                  */
 951                 zero_page = get_huge_zero_page();
 952                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
 953                                 zero_page);
 954                 ret = 0;
 955                 goto out_unlock;
 956         }
 957
 958         if (unlikely(pmd_trans_splitting(pmd))) {
 959                 /* split huge page running from under us */
 960                 spin_unlock(src_ptl);
 961                 spin_unlock(dst_ptl);
 962                 pte_free(dst_mm, pgtable);
 963
 964                 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
 965                 goto out;
 966         }
 967         src_page = pmd_page(pmd);
 968         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
 969         get_page(src_page);
 970         page_dup_rmap(src_page);
 971         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 972
 973         pmdp_set_wrprotect(src_mm, addr, src_pmd);
 974         pmd = pmd_mkold(pmd_wrprotect(pmd));
 975         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 976         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 977         atomic_long_inc(&dst_mm->nr_ptes);
 978
 979         ret = 0;
 980 out_unlock:
 981         spin_unlock(src_ptl);
 982         spin_unlock(dst_ptl);
 983 out:
 984         return ret;
 985 }
 986
 987 void huge_pmd_set_accessed(struct mm_struct *mm,
 988                            struct vm_area_struct *vma,
 989                            unsigned long address,
 990                            pmd_t *pmd, pmd_t orig_pmd,
 991                            int dirty)
 992 {
 993         spinlock_t *ptl;
 994         pmd_t entry;
 995         unsigned long haddr;
 996
 997         ptl = pmd_lock(mm, pmd);
 998         if (unlikely(!pmd_same(*pmd, orig_pmd)))
 999                 goto unlock;
1000
1001         entry = pmd_mkyoung(orig_pmd);
1002         haddr = address & HPAGE_PMD_MASK;
1003         if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1004                 update_mmu_cache_pmd(vma, address, pmd);
1005
1006 unlock:
1007         spin_unlock(ptl);
1008 }
1009
1010 /*
1011  * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages
1012  * during copy_user_huge_page()'s copy_page_rep(): in the case when
1013  * the source page gets split and a tail freed before copy completes.
1014  * Called under pmd_lock of checked pmd, so safe from splitting itself.
1015  */
1016 static void get_user_huge_page(struct page *page)
1017 {
1018         if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
1019                 struct page *endpage = page + HPAGE_PMD_NR;
1020
1021                 atomic_add(HPAGE_PMD_NR, &page->_count);
1022                 while (++page < endpage)
1023                         get_huge_page_tail(page);
1024         } else {
1025                 get_page(page);
1026         }
1027 }
1028
1029 static void put_user_huge_page(struct page *page)
1030 {
1031         if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) {
1032                 struct page *endpage = page + HPAGE_PMD_NR;
1033
1034                 while (page < endpage)
1035                         put_page(page++);
1036         } else {
1037                 put_page(page);
1038         }
1039 }
1040
1041 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1042                                         struct vm_area_struct *vma,
1043                                         unsigned long address,
1044                                         pmd_t *pmd, pmd_t orig_pmd,
1045                                         struct page *page,
1046                                         unsigned long haddr)
1047 {
1048         struct mem_cgroup *memcg;
1049         spinlock_t *ptl;
1050         pgtable_t pgtable;
1051         pmd_t _pmd;
1052         int ret = 0, i;
1053         struct page **pages;
1054         unsigned long mmun_start;       /* For mmu_notifiers */
1055         unsigned long mmun_end;         /* For mmu_notifiers */
1056
1057         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1058                         GFP_KERNEL);
1059         if (unlikely(!pages)) {
1060                 ret |= VM_FAULT_OOM;
1061                 goto out;
1062         }
1063
1064         for (i = 0; i < HPAGE_PMD_NR; i++) {
1065                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1066                                                __GFP_OTHER_NODE,
1067                                                vma, address, page_to_nid(page));
1068                 if (unlikely(!pages[i] ||
1069                              mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1070                                                    &memcg))) {
1071                         if (pages[i])
1072                                 put_page(pages[i]);
1073                         while (--i >= 0) {
1074                                 memcg = (void *)page_private(pages[i]);
1075                                 set_page_private(pages[i], 0);
1076                                 mem_cgroup_cancel_charge(pages[i], memcg);
1077                                 put_page(pages[i]);
1078                         }
1079                         kfree(pages);
1080                         ret |= VM_FAULT_OOM;
1081                         goto out;
1082                 }
1083                 set_page_private(pages[i], (unsigned long)memcg);
1084         }
1085
1086         for (i = 0; i < HPAGE_PMD_NR; i++) {
1087                 copy_user_highpage(pages[i], page + i,
1088                                    haddr + PAGE_SIZE * i, vma);
1089                 __SetPageUptodate(pages[i]);
1090                 cond_resched();
1091         }
1092
1093         mmun_start = haddr;
1094         mmun_end   = haddr + HPAGE_PMD_SIZE;
1095         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1096
1097         ptl = pmd_lock(mm, pmd);
1098         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1099                 goto out_free_pages;
1100         VM_BUG_ON_PAGE(!PageHead(page), page);
1101
1102         pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1103         /* leave pmd empty until pte is filled */
1104
1105         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1106         pmd_populate(mm, &_pmd, pgtable);
1107
1108         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1109                 pte_t *pte, entry;
1110                 entry = mk_pte(pages[i], vma->vm_page_prot);
1111                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1112                 memcg = (void *)page_private(pages[i]);
1113                 set_page_private(pages[i], 0);
1114                 page_add_new_anon_rmap(pages[i], vma, haddr);
1115                 mem_cgroup_commit_charge(pages[i], memcg, false);
1116                 lru_cache_add_active_or_unevictable(pages[i], vma);
1117                 pte = pte_offset_map(&_pmd, haddr);
1118                 VM_BUG_ON(!pte_none(*pte));
1119                 set_pte_at(mm, haddr, pte, entry);
1120                 pte_unmap(pte);
1121         }
1122         kfree(pages);
1123
1124         smp_wmb(); /* make pte visible before pmd */
1125         pmd_populate(mm, pmd, pgtable);
1126         page_remove_rmap(page);
1127         spin_unlock(ptl);
1128
1129         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1130
1131         ret |= VM_FAULT_WRITE;
1132         put_page(page);
1133
1134 out:
1135         return ret;
1136
1137 out_free_pages:
1138         spin_unlock(ptl);
1139         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1140         for (i = 0; i < HPAGE_PMD_NR; i++) {
1141                 memcg = (void *)page_private(pages[i]);
1142                 set_page_private(pages[i], 0);
1143                 mem_cgroup_cancel_charge(pages[i], memcg);
1144                 put_page(pages[i]);
1145         }
1146         kfree(pages);
1147         goto out;
1148 }
1149
1150 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1151                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1152 {
1153         spinlock_t *ptl;
1154         int ret = 0;
1155         struct page *page = NULL, *new_page;
1156         struct mem_cgroup *memcg;
1157         unsigned long haddr;
1158         unsigned long mmun_start;       /* For mmu_notifiers */
1159         unsigned long mmun_end;         /* For mmu_notifiers */
1160         gfp_t huge_gfp;                 /* for allocation and charge */
1161
1162         ptl = pmd_lockptr(mm, pmd);
1163         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1164         haddr = address & HPAGE_PMD_MASK;
1165         if (is_huge_zero_pmd(orig_pmd))
1166                 goto alloc;
1167         spin_lock(ptl);
1168         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1169                 goto out_unlock;
1170
1171         page = pmd_page(orig_pmd);
1172         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1173         if (page_mapcount(page) == 1) {
1174                 pmd_t entry;
1175                 entry = pmd_mkyoung(orig_pmd);
1176                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1177                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1178                         update_mmu_cache_pmd(vma, address, pmd);
1179                 ret |= VM_FAULT_WRITE;
1180                 goto out_unlock;
1181         }
1182         get_user_huge_page(page);
1183         spin_unlock(ptl);
1184 alloc:
1185         if (transparent_hugepage_enabled(vma) &&
1186             !transparent_hugepage_debug_cow()) {
1187                 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1188                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1189         } else
1190                 new_page = NULL;
1191
1192         if (unlikely(!new_page)) {
1193                 if (!page) {
1194                         split_huge_page_pmd(vma, address, pmd);
1195                         ret |= VM_FAULT_FALLBACK;
1196                 } else {
1197                         ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1198                                         pmd, orig_pmd, page, haddr);
1199                         if (ret & VM_FAULT_OOM) {
1200                                 split_huge_page(page);
1201                                 ret |= VM_FAULT_FALLBACK;
1202                         }
1203                         put_user_huge_page(page);
1204                 }
1205                 count_vm_event(THP_FAULT_FALLBACK);
1206                 goto out;
1207         }
1208
1209         if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) {
1210                 put_page(new_page);
1211                 if (page) {
1212                         split_huge_page(page);
1213                         put_user_huge_page(page);
1214                 } else
1215                         split_huge_page_pmd(vma, address, pmd);
1216                 ret |= VM_FAULT_FALLBACK;
1217                 count_vm_event(THP_FAULT_FALLBACK);
1218                 goto out;
1219         }
1220
1221         count_vm_event(THP_FAULT_ALLOC);
1222
1223         if (!page)
1224                 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1225         else
1226                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1227         __SetPageUptodate(new_page);
1228
1229         mmun_start = haddr;
1230         mmun_end   = haddr + HPAGE_PMD_SIZE;
1231         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1232
1233         spin_lock(ptl);
1234         if (page)
1235                 put_user_huge_page(page);
1236         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1237                 spin_unlock(ptl);
1238                 mem_cgroup_cancel_charge(new_page, memcg);
1239                 put_page(new_page);
1240                 goto out_mn;
1241         } else {
1242                 pmd_t entry;
1243                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1244                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1245                 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1246                 page_add_new_anon_rmap(new_page, vma, haddr);
1247                 mem_cgroup_commit_charge(new_page, memcg, false);
1248                 lru_cache_add_active_or_unevictable(new_page, vma);
1249                 set_pmd_at(mm, haddr, pmd, entry);
1250                 update_mmu_cache_pmd(vma, address, pmd);
1251                 if (!page) {
1252                         add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1253                         put_huge_zero_page();
1254                 } else {
1255                         VM_BUG_ON_PAGE(!PageHead(page), page);
1256                         page_remove_rmap(page);
1257                         put_page(page);
1258                 }
1259                 ret |= VM_FAULT_WRITE;
1260         }
1261         spin_unlock(ptl);
1262 out_mn:
1263         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1264 out:
1265         return ret;
1266 out_unlock:
1267         spin_unlock(ptl);
1268         return ret;
1269 }
1270
1271 /*
1272  * FOLL_FORCE can write to even unwritable pmd's, but only
1273  * after we've gone through a COW cycle and they are dirty.
1274  */
1275 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1276 {
1277         return pmd_write(pmd) ||
1278                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1279 }
1280
1281 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1282                                    unsigned long addr,
1283                                    pmd_t *pmd,
1284                                    unsigned int flags)
1285 {
1286         struct mm_struct *mm = vma->vm_mm;
1287         struct page *page = NULL;
1288
1289         assert_spin_locked(pmd_lockptr(mm, pmd));
1290
1291         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1292                 goto out;
1293
1294         /* Avoid dumping huge zero page */
1295         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1296                 return ERR_PTR(-EFAULT);
1297
1298         /* Full NUMA hinting faults to serialise migration in fault paths */
1299         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1300                 goto out;
1301
1302         page = pmd_page(*pmd);
1303         VM_BUG_ON_PAGE(!PageHead(page), page);
1304         if (flags & FOLL_TOUCH) {
1305                 pmd_t _pmd;
1306                 _pmd = pmd_mkyoung(*pmd);
1307                 if (flags & FOLL_WRITE)
1308                         _pmd = pmd_mkdirty(_pmd);
1309                 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1310                                           pmd, _pmd, flags & FOLL_WRITE))
1311                         update_mmu_cache_pmd(vma, addr, pmd);
1312         }
1313         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1314                 if (page->mapping && trylock_page(page)) {
1315                         lru_add_drain();
1316                         if (page->mapping)
1317                                 mlock_vma_page(page);
1318                         unlock_page(page);
1319                 }
1320         }
1321         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1322         VM_BUG_ON_PAGE(!PageCompound(page), page);
1323         if (flags & FOLL_GET)
1324                 get_page_foll(page);
1325
1326 out:
1327         return page;
1328 }
1329
1330 /* NUMA hinting page fault entry point for trans huge pmds */
1331 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1332                                 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1333 {
1334         spinlock_t *ptl;
1335         struct anon_vma *anon_vma = NULL;
1336         struct page *page;
1337         unsigned long haddr = addr & HPAGE_PMD_MASK;
1338         int page_nid = -1, this_nid = numa_node_id();
1339         int target_nid, last_cpupid = -1;
1340         bool page_locked;
1341         bool migrated = false;
1342         bool was_writable;
1343         int flags = 0;
1344
1345         /* A PROT_NONE fault should not end up here */
1346         BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1347
1348         ptl = pmd_lock(mm, pmdp);
1349         if (unlikely(!pmd_same(pmd, *pmdp)))
1350                 goto out_unlock;
1351
1352         /*
1353          * If there are potential migrations, wait for completion and retry
1354          * without disrupting NUMA hinting information. Do not relock and
1355          * check_same as the page may no longer be mapped.
1356          */
1357         if (unlikely(pmd_trans_migrating(*pmdp))) {
1358                 page = pmd_page(*pmdp);
1359                 if (!get_page_unless_zero(page))
1360                         goto out_unlock;
1361                 spin_unlock(ptl);
1362                 wait_on_page_locked(page);
1363                 put_page(page);
1364                 goto out;
1365         }
1366
1367         page = pmd_page(pmd);
1368         BUG_ON(is_huge_zero_page(page));
1369         page_nid = page_to_nid(page);
1370         last_cpupid = page_cpupid_last(page);
1371         count_vm_numa_event(NUMA_HINT_FAULTS);
1372         if (page_nid == this_nid) {
1373                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1374                 flags |= TNF_FAULT_LOCAL;
1375         }
1376
1377         /* See similar comment in do_numa_page for explanation */
1378         if (!(vma->vm_flags & VM_WRITE))
1379                 flags |= TNF_NO_GROUP;
1380
1381         /*
1382          * Acquire the page lock to serialise THP migrations but avoid dropping
1383          * page_table_lock if at all possible
1384          */
1385         page_locked = trylock_page(page);
1386         target_nid = mpol_misplaced(page, vma, haddr);
1387         if (target_nid == -1) {
1388                 /* If the page was locked, there are no parallel migrations */
1389                 if (page_locked)
1390                         goto clear_pmdnuma;
1391         }
1392
1393         /* Migration could have started since the pmd_trans_migrating check */
1394         if (!page_locked) {
1395                 if (!get_page_unless_zero(page))
1396                         goto out_unlock;
1397                 spin_unlock(ptl);
1398                 wait_on_page_locked(page);
1399                 put_page(page);
1400                 page_nid = -1;
1401                 goto out;
1402         }
1403
1404         /*
1405          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1406          * to serialises splits
1407          */
1408         get_page(page);
1409         spin_unlock(ptl);
1410         anon_vma = page_lock_anon_vma_read(page);
1411
1412         /* Confirm the PMD did not change while page_table_lock was released */
1413         spin_lock(ptl);
1414         if (unlikely(!pmd_same(pmd, *pmdp))) {
1415                 unlock_page(page);
1416                 put_page(page);
1417                 page_nid = -1;
1418                 goto out_unlock;
1419         }
1420
1421         /* Bail if we fail to protect against THP splits for any reason */
1422         if (unlikely(!anon_vma)) {
1423                 put_page(page);
1424                 page_nid = -1;
1425                 goto clear_pmdnuma;
1426         }
1427
1428         /*
1429          * Migrate the THP to the requested node, returns with page unlocked
1430          * and access rights restored.
1431          */
1432         spin_unlock(ptl);
1433         migrated = migrate_misplaced_transhuge_page(mm, vma,
1434                                 pmdp, pmd, addr, page, target_nid);
1435         if (migrated) {
1436                 flags |= TNF_MIGRATED;
1437                 page_nid = target_nid;
1438         } else
1439                 flags |= TNF_MIGRATE_FAIL;
1440
1441         goto out;
1442 clear_pmdnuma:
1443         BUG_ON(!PageLocked(page));
1444         was_writable = pmd_write(pmd);
1445         pmd = pmd_modify(pmd, vma->vm_page_prot);
1446         pmd = pmd_mkyoung(pmd);
1447         if (was_writable)
1448                 pmd = pmd_mkwrite(pmd);
1449         set_pmd_at(mm, haddr, pmdp, pmd);
1450         update_mmu_cache_pmd(vma, addr, pmdp);
1451         unlock_page(page);
1452 out_unlock:
1453         spin_unlock(ptl);
1454
1455 out:
1456         if (anon_vma)
1457                 page_unlock_anon_vma_read(anon_vma);
1458
1459         if (page_nid != -1)
1460                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1461
1462         return 0;
1463 }
1464
1465 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1466                  pmd_t *pmd, unsigned long addr)
1467 {
1468         pmd_t orig_pmd;
1469         spinlock_t *ptl;
1470
1471         if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1)
1472                 return 0;
1473         /*
1474          * For architectures like ppc64 we look at deposited pgtable
1475          * when calling pmdp_huge_get_and_clear. So do the
1476          * pgtable_trans_huge_withdraw after finishing pmdp related
1477          * operations.
1478          */
1479         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1480                         tlb->fullmm);
1481         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1482         if (vma_is_dax(vma)) {
1483                 spin_unlock(ptl);
1484                 if (is_huge_zero_pmd(orig_pmd))
1485                         put_huge_zero_page();
1486         } else if (is_huge_zero_pmd(orig_pmd)) {
1487                 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1488                 atomic_long_dec(&tlb->mm->nr_ptes);
1489                 spin_unlock(ptl);
1490                 put_huge_zero_page();
1491         } else {
1492                 struct page *page = pmd_page(orig_pmd);
1493                 page_remove_rmap(page);
1494                 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1495                 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1496                 VM_BUG_ON_PAGE(!PageHead(page), page);
1497                 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1498                 atomic_long_dec(&tlb->mm->nr_ptes);
1499                 spin_unlock(ptl);
1500                 tlb_remove_page(tlb, page);
1501         }
1502         return 1;
1503 }
1504
1505 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1506                   unsigned long old_addr,
1507                   unsigned long new_addr, unsigned long old_end,
1508                   pmd_t *old_pmd, pmd_t *new_pmd)
1509 {
1510         spinlock_t *old_ptl, *new_ptl;
1511         int ret = 0;
1512         pmd_t pmd;
1513
1514         struct mm_struct *mm = vma->vm_mm;
1515
1516         if ((old_addr & ~HPAGE_PMD_MASK) ||
1517             (new_addr & ~HPAGE_PMD_MASK) ||
1518             old_end - old_addr < HPAGE_PMD_SIZE ||
1519             (new_vma->vm_flags & VM_NOHUGEPAGE))
1520                 goto out;
1521
1522         /*
1523          * The destination pmd shouldn't be established, free_pgtables()
1524          * should have release it.
1525          */
1526         if (WARN_ON(!pmd_none(*new_pmd))) {
1527                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1528                 goto out;
1529         }
1530
1531         /*
1532          * We don't have to worry about the ordering of src and dst
1533          * ptlocks because exclusive mmap_sem prevents deadlock.
1534          */
1535         ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
1536         if (ret == 1) {
1537                 new_ptl = pmd_lockptr(mm, new_pmd);
1538                 if (new_ptl != old_ptl)
1539                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1540                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1541                 VM_BUG_ON(!pmd_none(*new_pmd));
1542
1543                 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1544                         pgtable_t pgtable;
1545                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1546                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1547                 }
1548                 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1549                 if (new_ptl != old_ptl)
1550                         spin_unlock(new_ptl);
1551                 spin_unlock(old_ptl);
1552         }
1553 out:
1554         return ret;
1555 }
1556
1557 /*
1558  * Returns
1559  *  - 0 if PMD could not be locked
1560  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1561  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1562  */
1563 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1564                 unsigned long addr, pgprot_t newprot, int prot_numa)
1565 {
1566         struct mm_struct *mm = vma->vm_mm;
1567         spinlock_t *ptl;
1568         pmd_t entry;
1569         bool preserve_write;
1570
1571         int ret = 0;
1572
1573         if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1)
1574                 return 0;
1575
1576         preserve_write = prot_numa && pmd_write(*pmd);
1577         ret = 1;
1578
1579         /*
1580          * Avoid trapping faults against the zero page. The read-only
1581          * data is likely to be read-cached on the local CPU and
1582          * local/remote hits to the zero page are not interesting.
1583          */
1584         if (prot_numa && is_huge_zero_pmd(*pmd))
1585                 goto unlock;
1586
1587         if (prot_numa && pmd_protnone(*pmd))
1588                 goto unlock;
1589
1590         /*
1591          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1592          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1593          * which is also under down_read(mmap_sem):
1594          *
1595          *      CPU0:                           CPU1:
1596          *                              change_huge_pmd(prot_numa=1)
1597          *                               pmdp_huge_get_and_clear_notify()
1598          * madvise_dontneed()
1599          *  zap_pmd_range()
1600          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1601          *   // skip the pmd
1602          *                               set_pmd_at();
1603          *                               // pmd is re-established
1604          *
1605          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1606          * which may break userspace.
1607          *
1608          * pmdp_invalidate() is required to make sure we don't miss
1609          * dirty/young flags set by hardware.
1610          */
1611         entry = *pmd;
1612         pmdp_invalidate(vma, addr, pmd);
1613
1614         /*
1615          * Recover dirty/young flags.  It relies on pmdp_invalidate to not
1616          * corrupt them.
1617          */
1618         if (pmd_dirty(*pmd))
1619                 entry = pmd_mkdirty(entry);
1620         if (pmd_young(*pmd))
1621                 entry = pmd_mkyoung(entry);
1622
1623         entry = pmd_modify(entry, newprot);
1624         if (preserve_write)
1625                 entry = pmd_mkwrite(entry);
1626         ret = HPAGE_PMD_NR;
1627         set_pmd_at(mm, addr, pmd, entry);
1628         BUG_ON(!preserve_write && pmd_write(entry));
1629 unlock:
1630         spin_unlock(ptl);
1631         return ret;
1632 }
1633
1634 /*
1635  * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1636  * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1637  *
1638  * Note that if it returns 1, this routine returns without unlocking page
1639  * table locks. So callers must unlock them.
1640  */
1641 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
1642                 spinlock_t **ptl)
1643 {
1644         *ptl = pmd_lock(vma->vm_mm, pmd);
1645         if (likely(pmd_trans_huge(*pmd))) {
1646                 if (unlikely(pmd_trans_splitting(*pmd))) {
1647                         spin_unlock(*ptl);
1648                         wait_split_huge_page(vma->anon_vma, pmd);
1649                         return -1;
1650                 } else {
1651                         /* Thp mapped by 'pmd' is stable, so we can
1652                          * handle it as it is. */
1653                         return 1;
1654                 }
1655         }
1656         spin_unlock(*ptl);
1657         return 0;
1658 }
1659
1660 /*
1661  * This function returns whether a given @page is mapped onto the @address
1662  * in the virtual space of @mm.
1663  *
1664  * When it's true, this function returns *pmd with holding the page table lock
1665  * and passing it back to the caller via @ptl.
1666  * If it's false, returns NULL without holding the page table lock.
1667  */
1668 pmd_t *page_check_address_pmd(struct page *page,
1669                               struct mm_struct *mm,
1670                               unsigned long address,
1671                               enum page_check_address_pmd_flag flag,
1672                               spinlock_t **ptl)
1673 {
1674         pgd_t *pgd;
1675         pud_t *pud;
1676         pmd_t *pmd;
1677
1678         if (address & ~HPAGE_PMD_MASK)
1679                 return NULL;
1680
1681         pgd = pgd_offset(mm, address);
1682         if (!pgd_present(*pgd))
1683                 return NULL;
1684         pud = pud_offset(pgd, address);
1685         if (!pud_present(*pud))
1686                 return NULL;
1687         pmd = pmd_offset(pud, address);
1688
1689         *ptl = pmd_lock(mm, pmd);
1690         if (!pmd_present(*pmd))
1691                 goto unlock;
1692         if (pmd_page(*pmd) != page)
1693                 goto unlock;
1694         /*
1695          * split_vma() may create temporary aliased mappings. There is
1696          * no risk as long as all huge pmd are found and have their
1697          * splitting bit set before __split_huge_page_refcount
1698          * runs. Finding the same huge pmd more than once during the
1699          * same rmap walk is not a problem.
1700          */
1701         if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1702             pmd_trans_splitting(*pmd))
1703                 goto unlock;
1704         if (pmd_trans_huge(*pmd)) {
1705                 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1706                           !pmd_trans_splitting(*pmd));
1707                 return pmd;
1708         }
1709 unlock:
1710         spin_unlock(*ptl);
1711         return NULL;
1712 }
1713
1714 static int __split_huge_page_splitting(struct page *page,
1715                                        struct vm_area_struct *vma,
1716                                        unsigned long address)
1717 {
1718         struct mm_struct *mm = vma->vm_mm;
1719         spinlock_t *ptl;
1720         pmd_t *pmd;
1721         int ret = 0;
1722         /* For mmu_notifiers */
1723         const unsigned long mmun_start = address;
1724         const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1725
1726         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1727         pmd = page_check_address_pmd(page, mm, address,
1728                         PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl);
1729         if (pmd) {
1730                 /*
1731                  * We can't temporarily set the pmd to null in order
1732                  * to split it, the pmd must remain marked huge at all
1733                  * times or the VM won't take the pmd_trans_huge paths
1734                  * and it won't wait on the anon_vma->root->rwsem to
1735                  * serialize against split_huge_page*.
1736                  */
1737                 pmdp_splitting_flush(vma, address, pmd);
1738
1739                 ret = 1;
1740                 spin_unlock(ptl);
1741         }
1742         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1743
1744         return ret;
1745 }
1746
1747 static void __split_huge_page_refcount(struct page *page,
1748                                        struct list_head *list)
1749 {
1750         int i;
1751         struct zone *zone = page_zone(page);
1752         struct lruvec *lruvec;
1753         int tail_count = 0;
1754
1755         /* prevent PageLRU to go away from under us, and freeze lru stats */
1756         spin_lock_irq(&zone->lru_lock);
1757         lruvec = mem_cgroup_page_lruvec(page, zone);
1758
1759         compound_lock(page);
1760         /* complete memcg works before add pages to LRU */
1761         mem_cgroup_split_huge_fixup(page);
1762
1763         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1764                 struct page *page_tail = page + i;
1765
1766                 /* tail_page->_mapcount cannot change */
1767                 BUG_ON(page_mapcount(page_tail) < 0);
1768                 tail_count += page_mapcount(page_tail);
1769                 /* check for overflow */
1770                 BUG_ON(tail_count < 0);
1771                 BUG_ON(atomic_read(&page_tail->_count) != 0);
1772                 /*
1773                  * tail_page->_count is zero and not changing from
1774                  * under us. But get_page_unless_zero() may be running
1775                  * from under us on the tail_page. If we used
1776                  * atomic_set() below instead of atomic_add(), we
1777                  * would then run atomic_set() concurrently with
1778                  * get_page_unless_zero(), and atomic_set() is
1779                  * implemented in C not using locked ops. spin_unlock
1780                  * on x86 sometime uses locked ops because of PPro
1781                  * errata 66, 92, so unless somebody can guarantee
1782                  * atomic_set() here would be safe on all archs (and
1783                  * not only on x86), it's safer to use atomic_add().
1784                  */
1785                 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1786                            &page_tail->_count);
1787
1788                 /* after clearing PageTail the gup refcount can be released */
1789                 smp_mb__after_atomic();
1790
1791                 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1792                 page_tail->flags |= (page->flags &
1793                                      ((1L << PG_referenced) |
1794                                       (1L << PG_swapbacked) |
1795                                       (1L << PG_mlocked) |
1796                                       (1L << PG_uptodate) |
1797                                       (1L << PG_active) |
1798                                       (1L << PG_unevictable)));
1799                 page_tail->flags |= (1L << PG_dirty);
1800
1801                 clear_compound_head(page_tail);
1802
1803                 if (page_is_young(page))
1804                         set_page_young(page_tail);
1805                 if (page_is_idle(page))
1806                         set_page_idle(page_tail);
1807
1808                 /*
1809                  * __split_huge_page_splitting() already set the
1810                  * splitting bit in all pmd that could map this
1811                  * hugepage, that will ensure no CPU can alter the
1812                  * mapcount on the head page. The mapcount is only
1813                  * accounted in the head page and it has to be
1814                  * transferred to all tail pages in the below code. So
1815                  * for this code to be safe, the split the mapcount
1816                  * can't change. But that doesn't mean userland can't
1817                  * keep changing and reading the page contents while
1818                  * we transfer the mapcount, so the pmd splitting
1819                  * status is achieved setting a reserved bit in the
1820                  * pmd, not by clearing the present bit.
1821                 */
1822                 page_tail->_mapcount = page->_mapcount;
1823
1824                 BUG_ON(page_tail->mapping);
1825                 page_tail->mapping = page->mapping;
1826
1827                 page_tail->index = page->index + i;
1828                 page_cpupid_xchg_last(page_tail, page_cpupid_last(page));
1829
1830                 BUG_ON(!PageAnon(page_tail));
1831                 BUG_ON(!PageUptodate(page_tail));
1832                 BUG_ON(!PageDirty(page_tail));
1833                 BUG_ON(!PageSwapBacked(page_tail));
1834
1835                 lru_add_page_tail(page, page_tail, lruvec, list);
1836         }
1837         atomic_sub(tail_count, &page->_count);
1838         BUG_ON(atomic_read(&page->_count) <= 0);
1839
1840         __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1841
1842         ClearPageCompound(page);
1843         compound_unlock(page);
1844         spin_unlock_irq(&zone->lru_lock);
1845
1846         for (i = 1; i < HPAGE_PMD_NR; i++) {
1847                 struct page *page_tail = page + i;
1848                 BUG_ON(page_count(page_tail) <= 0);
1849                 /*
1850                  * Tail pages may be freed if there wasn't any mapping
1851                  * like if add_to_swap() is running on a lru page that
1852                  * had its mapping zapped. And freeing these pages
1853                  * requires taking the lru_lock so we do the put_page
1854                  * of the tail pages after the split is complete.
1855                  */
1856                 put_page(page_tail);
1857         }
1858
1859         /*
1860          * Only the head page (now become a regular page) is required
1861          * to be pinned by the caller.
1862          */
1863         BUG_ON(page_count(page) <= 0);
1864 }
1865
1866 static int __split_huge_page_map(struct page *page,
1867                                  struct vm_area_struct *vma,
1868                                  unsigned long address)
1869 {
1870         struct mm_struct *mm = vma->vm_mm;
1871         spinlock_t *ptl;
1872         pmd_t *pmd, _pmd;
1873         int ret = 0, i;
1874         pgtable_t pgtable;
1875         unsigned long haddr;
1876
1877         pmd = page_check_address_pmd(page, mm, address,
1878                         PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl);
1879         if (pmd) {
1880                 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1881                 pmd_populate(mm, &_pmd, pgtable);
1882                 if (pmd_write(*pmd))
1883                         BUG_ON(page_mapcount(page) != 1);
1884
1885                 haddr = address;
1886                 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1887                         pte_t *pte, entry;
1888                         BUG_ON(PageCompound(page+i));
1889                         /*
1890                          * Note that NUMA hinting access restrictions are not
1891                          * transferred to avoid any possibility of altering
1892                          * permissions across VMAs.
1893                          */
1894                         entry = mk_pte(page + i, vma->vm_page_prot);
1895                         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1896                         if (!pmd_write(*pmd))
1897                                 entry = pte_wrprotect(entry);
1898                         if (!pmd_young(*pmd))
1899                                 entry = pte_mkold(entry);
1900                         pte = pte_offset_map(&_pmd, haddr);
1901                         BUG_ON(!pte_none(*pte));
1902                         set_pte_at(mm, haddr, pte, entry);
1903                         pte_unmap(pte);
1904                 }
1905
1906                 smp_wmb(); /* make pte visible before pmd */
1907                 /*
1908                  * Up to this point the pmd is present and huge and
1909                  * userland has the whole access to the hugepage
1910                  * during the split (which happens in place). If we
1911                  * overwrite the pmd with the not-huge version
1912                  * pointing to the pte here (which of course we could
1913                  * if all CPUs were bug free), userland could trigger
1914                  * a small page size TLB miss on the small sized TLB
1915                  * while the hugepage TLB entry is still established
1916                  * in the huge TLB. Some CPU doesn't like that. See
1917                  * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1918                  * Erratum 383 on page 93. Intel should be safe but is
1919                  * also warns that it's only safe if the permission
1920                  * and cache attributes of the two entries loaded in
1921                  * the two TLB is identical (which should be the case
1922                  * here). But it is generally safer to never allow
1923                  * small and huge TLB entries for the same virtual
1924                  * address to be loaded simultaneously. So instead of
1925                  * doing "pmd_populate(); flush_pmd_tlb_range();" we first
1926                  * mark the current pmd notpresent (atomically because
1927                  * here the pmd_trans_huge and pmd_trans_splitting
1928                  * must remain set at all times on the pmd until the
1929                  * split is complete for this pmd), then we flush the
1930                  * SMP TLB and finally we write the non-huge version
1931                  * of the pmd entry with pmd_populate.
1932                  */
1933                 pmdp_invalidate(vma, address, pmd);
1934                 pmd_populate(mm, pmd, pgtable);
1935                 ret = 1;
1936                 spin_unlock(ptl);
1937         }
1938
1939         return ret;
1940 }
1941
1942 /* must be called with anon_vma->root->rwsem held */
1943 static void __split_huge_page(struct page *page,
1944                               struct anon_vma *anon_vma,
1945                               struct list_head *list)
1946 {
1947         int mapcount, mapcount2;
1948         pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1949         struct anon_vma_chain *avc;
1950
1951         BUG_ON(!PageHead(page));
1952         BUG_ON(PageTail(page));
1953
1954         mapcount = 0;
1955         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1956                 struct vm_area_struct *vma = avc->vma;
1957                 unsigned long addr = vma_address(page, vma);
1958                 BUG_ON(is_vma_temporary_stack(vma));
1959                 mapcount += __split_huge_page_splitting(page, vma, addr);
1960         }
1961         /*
1962          * It is critical that new vmas are added to the tail of the
1963          * anon_vma list. This guarantes that if copy_huge_pmd() runs
1964          * and establishes a child pmd before
1965          * __split_huge_page_splitting() freezes the parent pmd (so if
1966          * we fail to prevent copy_huge_pmd() from running until the
1967          * whole __split_huge_page() is complete), we will still see
1968          * the newly established pmd of the child later during the
1969          * walk, to be able to set it as pmd_trans_splitting too.
1970          */
1971         if (mapcount != page_mapcount(page)) {
1972                 pr_err("mapcount %d page_mapcount %d\n",
1973                         mapcount, page_mapcount(page));
1974                 BUG();
1975         }
1976
1977         __split_huge_page_refcount(page, list);
1978
1979         mapcount2 = 0;
1980         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1981                 struct vm_area_struct *vma = avc->vma;
1982                 unsigned long addr = vma_address(page, vma);
1983                 BUG_ON(is_vma_temporary_stack(vma));
1984                 mapcount2 += __split_huge_page_map(page, vma, addr);
1985         }
1986         if (mapcount != mapcount2) {
1987                 pr_err("mapcount %d mapcount2 %d page_mapcount %d\n",
1988                         mapcount, mapcount2, page_mapcount(page));
1989                 BUG();
1990         }
1991 }
1992
1993 /*
1994  * Split a hugepage into normal pages. This doesn't change the position of head
1995  * page. If @list is null, tail pages will be added to LRU list, otherwise, to
1996  * @list. Both head page and tail pages will inherit mapping, flags, and so on
1997  * from the hugepage.
1998  * Return 0 if the hugepage is split successfully otherwise return 1.
1999  */
2000 int split_huge_page_to_list(struct page *page, struct list_head *list)
2001 {
2002         struct anon_vma *anon_vma;
2003         int ret = 1;
2004
2005         BUG_ON(is_huge_zero_page(page));
2006         BUG_ON(!PageAnon(page));
2007
2008         /*
2009          * The caller does not necessarily hold an mmap_sem that would prevent
2010          * the anon_vma disappearing so we first we take a reference to it
2011          * and then lock the anon_vma for write. This is similar to
2012          * page_lock_anon_vma_read except the write lock is taken to serialise
2013          * against parallel split or collapse operations.
2014          */
2015         anon_vma = page_get_anon_vma(page);
2016         if (!anon_vma)
2017                 goto out;
2018         anon_vma_lock_write(anon_vma);
2019
2020         ret = 0;
2021         if (!PageCompound(page))
2022                 goto out_unlock;
2023
2024         BUG_ON(!PageSwapBacked(page));
2025         __split_huge_page(page, anon_vma, list);
2026         count_vm_event(THP_SPLIT);
2027
2028         BUG_ON(PageCompound(page));
2029 out_unlock:
2030         anon_vma_unlock_write(anon_vma);
2031         put_anon_vma(anon_vma);
2032 out:
2033         return ret;
2034 }
2035
2036 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
2037
2038 int hugepage_madvise(struct vm_area_struct *vma,
2039                      unsigned long *vm_flags, int advice)
2040 {
2041         switch (advice) {
2042         case MADV_HUGEPAGE:
2043 #ifdef CONFIG_S390
2044                 /*
2045                  * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
2046                  * can't handle this properly after s390_enable_sie, so we simply
2047                  * ignore the madvise to prevent qemu from causing a SIGSEGV.
2048                  */
2049                 if (mm_has_pgste(vma->vm_mm))
2050                         return 0;
2051 #endif
2052                 /*
2053                  * Be somewhat over-protective like KSM for now!
2054                  */
2055                 if (*vm_flags & VM_NO_THP)
2056                         return -EINVAL;
2057                 *vm_flags &= ~VM_NOHUGEPAGE;
2058                 *vm_flags |= VM_HUGEPAGE;
2059                 /*
2060                  * If the vma become good for khugepaged to scan,
2061                  * register it here without waiting a page fault that
2062                  * may not happen any time soon.
2063                  */
2064                 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
2065                         return -ENOMEM;
2066                 break;
2067         case MADV_NOHUGEPAGE:
2068                 /*
2069                  * Be somewhat over-protective like KSM for now!
2070                  */
2071                 if (*vm_flags & VM_NO_THP)
2072                         return -EINVAL;
2073                 *vm_flags &= ~VM_HUGEPAGE;
2074                 *vm_flags |= VM_NOHUGEPAGE;
2075                 /*
2076                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
2077                  * this vma even if we leave the mm registered in khugepaged if
2078                  * it got registered before VM_NOHUGEPAGE was set.
2079                  */
2080                 break;
2081         }
2082
2083         return 0;
2084 }
2085
2086 static int __init khugepaged_slab_init(void)
2087 {
2088         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
2089                                           sizeof(struct mm_slot),
2090                                           __alignof__(struct mm_slot), 0, NULL);
2091         if (!mm_slot_cache)
2092                 return -ENOMEM;
2093
2094         return 0;
2095 }
2096
2097 static void __init khugepaged_slab_exit(void)
2098 {
2099         kmem_cache_destroy(mm_slot_cache);
2100 }
2101
2102 static inline struct mm_slot *alloc_mm_slot(void)
2103 {
2104         if (!mm_slot_cache)     /* initialization failed */
2105                 return NULL;
2106         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
2107 }
2108
2109 static inline void free_mm_slot(struct mm_slot *mm_slot)
2110 {
2111         kmem_cache_free(mm_slot_cache, mm_slot);
2112 }
2113
2114 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
2115 {
2116         struct mm_slot *mm_slot;
2117
2118         hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
2119                 if (mm == mm_slot->mm)
2120                         return mm_slot;
2121
2122         return NULL;
2123 }
2124
2125 static void insert_to_mm_slots_hash(struct mm_struct *mm,
2126                                     struct mm_slot *mm_slot)
2127 {
2128         mm_slot->mm = mm;
2129         hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
2130 }
2131
2132 static inline int khugepaged_test_exit(struct mm_struct *mm)
2133 {
2134         return atomic_read(&mm->mm_users) == 0;
2135 }
2136
2137 int __khugepaged_enter(struct mm_struct *mm)
2138 {
2139         struct mm_slot *mm_slot;
2140         int wakeup;
2141
2142         mm_slot = alloc_mm_slot();
2143         if (!mm_slot)
2144                 return -ENOMEM;
2145
2146         /* __khugepaged_exit() must not run from under us */
2147         VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
2148         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
2149                 free_mm_slot(mm_slot);
2150                 return 0;
2151         }
2152
2153         spin_lock(&khugepaged_mm_lock);
2154         insert_to_mm_slots_hash(mm, mm_slot);
2155         /*
2156          * Insert just behind the scanning cursor, to let the area settle
2157          * down a little.
2158          */
2159         wakeup = list_empty(&khugepaged_scan.mm_head);
2160         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
2161         spin_unlock(&khugepaged_mm_lock);
2162
2163         atomic_inc(&mm->mm_count);
2164         if (wakeup)
2165                 wake_up_interruptible(&khugepaged_wait);
2166
2167         return 0;
2168 }
2169
2170 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
2171                                unsigned long vm_flags)
2172 {
2173         unsigned long hstart, hend;
2174         if (!vma->anon_vma)
2175                 /*
2176                  * Not yet faulted in so we will register later in the
2177                  * page fault if needed.
2178                  */
2179                 return 0;
2180         if (vma->vm_ops || (vm_flags & VM_NO_THP))
2181                 /* khugepaged not yet working on file or special mappings */
2182                 return 0;
2183         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2184         hend = vma->vm_end & HPAGE_PMD_MASK;
2185         if (hstart < hend)
2186                 return khugepaged_enter(vma, vm_flags);
2187         return 0;
2188 }
2189
2190 void __khugepaged_exit(struct mm_struct *mm)
2191 {
2192         struct mm_slot *mm_slot;
2193         int free = 0;
2194
2195         spin_lock(&khugepaged_mm_lock);
2196         mm_slot = get_mm_slot(mm);
2197         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2198                 hash_del(&mm_slot->hash);
2199                 list_del(&mm_slot->mm_node);
2200                 free = 1;
2201         }
2202         spin_unlock(&khugepaged_mm_lock);
2203
2204         if (free) {
2205                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2206                 free_mm_slot(mm_slot);
2207                 mmdrop(mm);
2208         } else if (mm_slot) {
2209                 /*
2210                  * This is required to serialize against
2211                  * khugepaged_test_exit() (which is guaranteed to run
2212                  * under mmap sem read mode). Stop here (after we
2213                  * return all pagetables will be destroyed) until
2214                  * khugepaged has finished working on the pagetables
2215                  * under the mmap_sem.
2216                  */
2217                 down_write(&mm->mmap_sem);
2218                 up_write(&mm->mmap_sem);
2219         }
2220 }
2221
2222 static void release_pte_page(struct page *page)
2223 {
2224         /* 0 stands for page_is_file_cache(page) == false */
2225         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2226         unlock_page(page);
2227         putback_lru_page(page);
2228 }
2229
2230 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2231 {
2232         while (--_pte >= pte) {
2233                 pte_t pteval = *_pte;
2234                 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2235                         release_pte_page(pte_page(pteval));
2236         }
2237 }
2238
2239 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2240                                         unsigned long address,
2241                                         pte_t *pte)
2242 {
2243         struct page *page;
2244         pte_t *_pte;
2245         int none_or_zero = 0;
2246         bool referenced = false, writable = false;
2247         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2248              _pte++, address += PAGE_SIZE) {
2249                 pte_t pteval = *_pte;
2250                 if (pte_none(pteval) || (pte_present(pteval) &&
2251                                 is_zero_pfn(pte_pfn(pteval)))) {
2252                         if (!userfaultfd_armed(vma) &&
2253                             ++none_or_zero <= khugepaged_max_ptes_none)
2254                                 continue;
2255                         else
2256                                 goto out;
2257                 }
2258                 if (!pte_present(pteval))
2259                         goto out;
2260                 page = vm_normal_page(vma, address, pteval);
2261                 if (unlikely(!page))
2262                         goto out;
2263
2264                 VM_BUG_ON_PAGE(PageCompound(page), page);
2265                 VM_BUG_ON_PAGE(!PageAnon(page), page);
2266                 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2267
2268                 /*
2269                  * We can do it before isolate_lru_page because the
2270                  * page can't be freed from under us. NOTE: PG_lock
2271                  * is needed to serialize against split_huge_page
2272                  * when invoked from the VM.
2273                  */
2274                 if (!trylock_page(page))
2275                         goto out;
2276
2277                 /*
2278                  * cannot use mapcount: can't collapse if there's a gup pin.
2279                  * The page must only be referenced by the scanned process
2280                  * and page swap cache.
2281                  */
2282                 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2283                         unlock_page(page);
2284                         goto out;
2285                 }
2286                 if (pte_write(pteval)) {
2287                         writable = true;
2288                 } else {
2289                         if (PageSwapCache(page) && !reuse_swap_page(page)) {
2290                                 unlock_page(page);
2291                                 goto out;
2292                         }
2293                         /*
2294                          * Page is not in the swap cache. It can be collapsed
2295                          * into a THP.
2296                          */
2297                 }
2298
2299                 /*
2300                  * Isolate the page to avoid collapsing an hugepage
2301                  * currently in use by the VM.
2302                  */
2303                 if (isolate_lru_page(page)) {
2304                         unlock_page(page);
2305                         goto out;
2306                 }
2307                 /* 0 stands for page_is_file_cache(page) == false */
2308                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2309                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2310                 VM_BUG_ON_PAGE(PageLRU(page), page);
2311
2312                 /* If there is no mapped pte young don't collapse the page */
2313                 if (pte_young(pteval) ||
2314                     page_is_young(page) || PageReferenced(page) ||
2315                     mmu_notifier_test_young(vma->vm_mm, address))
2316                         referenced = true;
2317         }
2318         if (likely(referenced && writable))
2319                 return 1;
2320 out:
2321         release_pte_pages(pte, _pte);
2322         return 0;
2323 }
2324
2325 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2326                                       struct vm_area_struct *vma,
2327                                       unsigned long address,
2328                                       spinlock_t *ptl)
2329 {
2330         pte_t *_pte;
2331         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2332                 pte_t pteval = *_pte;
2333                 struct page *src_page;
2334
2335                 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2336                         clear_user_highpage(page, address);
2337                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2338                         if (is_zero_pfn(pte_pfn(pteval))) {
2339                                 /*
2340                                  * ptl mostly unnecessary.
2341                                  */
2342                                 spin_lock(ptl);
2343                                 /*
2344                                  * paravirt calls inside pte_clear here are
2345                                  * superfluous.
2346                                  */
2347                                 pte_clear(vma->vm_mm, address, _pte);
2348                                 spin_unlock(ptl);
2349                         }
2350                 } else {
2351                         src_page = pte_page(pteval);
2352                         copy_user_highpage(page, src_page, address, vma);
2353                         VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2354                         release_pte_page(src_page);
2355                         /*
2356                          * ptl mostly unnecessary, but preempt has to
2357                          * be disabled to update the per-cpu stats
2358                          * inside page_remove_rmap().
2359                          */
2360                         spin_lock(ptl);
2361                         /*
2362                          * paravirt calls inside pte_clear here are
2363                          * superfluous.
2364                          */
2365                         pte_clear(vma->vm_mm, address, _pte);
2366                         page_remove_rmap(src_page);
2367                         spin_unlock(ptl);
2368                         free_page_and_swap_cache(src_page);
2369                 }
2370
2371                 address += PAGE_SIZE;
2372                 page++;
2373         }
2374 }
2375
2376 static void khugepaged_alloc_sleep(void)
2377 {
2378         DEFINE_WAIT(wait);
2379
2380         add_wait_queue(&khugepaged_wait, &wait);
2381         freezable_schedule_timeout_interruptible(
2382                 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2383         remove_wait_queue(&khugepaged_wait, &wait);
2384 }
2385
2386 static int khugepaged_node_load[MAX_NUMNODES];
2387
2388 static bool khugepaged_scan_abort(int nid)
2389 {
2390         int i;
2391
2392         /*
2393          * If zone_reclaim_mode is disabled, then no extra effort is made to
2394          * allocate memory locally.
2395          */
2396         if (!zone_reclaim_mode)
2397                 return false;
2398
2399         /* If there is a count for this node already, it must be acceptable */
2400         if (khugepaged_node_load[nid])
2401                 return false;
2402
2403         for (i = 0; i < MAX_NUMNODES; i++) {
2404                 if (!khugepaged_node_load[i])
2405                         continue;
2406                 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2407                         return true;
2408         }
2409         return false;
2410 }
2411
2412 #ifdef CONFIG_NUMA
2413 static int khugepaged_find_target_node(void)
2414 {
2415         static int last_khugepaged_target_node = NUMA_NO_NODE;
2416         int nid, target_node = 0, max_value = 0;
2417
2418         /* find first node with max normal pages hit */
2419         for (nid = 0; nid < MAX_NUMNODES; nid++)
2420                 if (khugepaged_node_load[nid] > max_value) {
2421                         max_value = khugepaged_node_load[nid];
2422                         target_node = nid;
2423                 }
2424
2425         /* do some balance if several nodes have the same hit record */
2426         if (target_node <= last_khugepaged_target_node)
2427                 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2428                                 nid++)
2429                         if (max_value == khugepaged_node_load[nid]) {
2430                                 target_node = nid;
2431                                 break;
2432                         }
2433
2434         last_khugepaged_target_node = target_node;
2435         return target_node;
2436 }
2437
2438 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2439 {
2440         if (IS_ERR(*hpage)) {
2441                 if (!*wait)
2442                         return false;
2443
2444                 *wait = false;
2445                 *hpage = NULL;
2446                 khugepaged_alloc_sleep();
2447         } else if (*hpage) {
2448                 put_page(*hpage);
2449                 *hpage = NULL;
2450         }
2451
2452         return true;
2453 }
2454
2455 static struct page *
2456 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2457                        unsigned long address, int node)
2458 {
2459         VM_BUG_ON_PAGE(*hpage, *hpage);
2460
2461         /*
2462          * Before allocating the hugepage, release the mmap_sem read lock.
2463          * The allocation can take potentially a long time if it involves
2464          * sync compaction, and we do not need to hold the mmap_sem during
2465          * that. We will recheck the vma after taking it again in write mode.
2466          */
2467         up_read(&mm->mmap_sem);
2468
2469         *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2470         if (unlikely(!*hpage)) {
2471                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2472                 *hpage = ERR_PTR(-ENOMEM);
2473                 return NULL;
2474         }
2475
2476         count_vm_event(THP_COLLAPSE_ALLOC);
2477         return *hpage;
2478 }
2479 #else
2480 static int khugepaged_find_target_node(void)
2481 {
2482         return 0;
2483 }
2484
2485 static inline struct page *alloc_hugepage(int defrag)
2486 {
2487         return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
2488                            HPAGE_PMD_ORDER);
2489 }
2490
2491 static struct page *khugepaged_alloc_hugepage(bool *wait)
2492 {
2493         struct page *hpage;
2494
2495         do {
2496                 hpage = alloc_hugepage(khugepaged_defrag());
2497                 if (!hpage) {
2498                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2499                         if (!*wait)
2500                                 return NULL;
2501
2502                         *wait = false;
2503                         khugepaged_alloc_sleep();
2504                 } else
2505                         count_vm_event(THP_COLLAPSE_ALLOC);
2506         } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2507
2508         return hpage;
2509 }
2510
2511 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2512 {
2513         if (!*hpage)
2514                 *hpage = khugepaged_alloc_hugepage(wait);
2515
2516         if (unlikely(!*hpage))
2517                 return false;
2518
2519         return true;
2520 }
2521
2522 static struct page *
2523 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2524                        unsigned long address, int node)
2525 {
2526         up_read(&mm->mmap_sem);
2527         VM_BUG_ON(!*hpage);
2528
2529         return  *hpage;
2530 }
2531 #endif
2532
2533 static bool hugepage_vma_check(struct vm_area_struct *vma)
2534 {
2535         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2536             (vma->vm_flags & VM_NOHUGEPAGE))
2537                 return false;
2538
2539         if (!vma->anon_vma || vma->vm_ops)
2540                 return false;
2541         if (is_vma_temporary_stack(vma))
2542                 return false;
2543         return !(vma->vm_flags & VM_NO_THP);
2544 }
2545
2546 static void collapse_huge_page(struct mm_struct *mm,
2547                                    unsigned long address,
2548                                    struct page **hpage,
2549                                    struct vm_area_struct *vma,
2550                                    int node)
2551 {
2552         pmd_t *pmd, _pmd;
2553         pte_t *pte;
2554         pgtable_t pgtable;
2555         struct page *new_page;
2556         spinlock_t *pmd_ptl, *pte_ptl;
2557         int isolated;
2558         unsigned long hstart, hend;
2559         struct mem_cgroup *memcg;
2560         unsigned long mmun_start;       /* For mmu_notifiers */
2561         unsigned long mmun_end;         /* For mmu_notifiers */
2562         gfp_t gfp;
2563
2564         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2565
2566         /* Only allocate from the target node */
2567         gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2568                 __GFP_THISNODE;
2569
2570         /* release the mmap_sem read lock. */
2571         new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2572         if (!new_page)
2573                 return;
2574
2575         if (unlikely(mem_cgroup_try_charge(new_page, mm,
2576                                            gfp, &memcg)))
2577                 return;
2578
2579         /*
2580          * Prevent all access to pagetables with the exception of
2581          * gup_fast later hanlded by the ptep_clear_flush and the VM
2582          * handled by the anon_vma lock + PG_lock.
2583          */
2584         down_write(&mm->mmap_sem);
2585         if (unlikely(khugepaged_test_exit(mm)))
2586                 goto out;
2587
2588         vma = find_vma(mm, address);
2589         if (!vma)
2590                 goto out;
2591         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2592         hend = vma->vm_end & HPAGE_PMD_MASK;
2593         if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2594                 goto out;
2595         if (!hugepage_vma_check(vma))
2596                 goto out;
2597         pmd = mm_find_pmd(mm, address);
2598         if (!pmd)
2599                 goto out;
2600
2601         anon_vma_lock_write(vma->anon_vma);
2602
2603         pte = pte_offset_map(pmd, address);
2604         pte_ptl = pte_lockptr(mm, pmd);
2605
2606         mmun_start = address;
2607         mmun_end   = address + HPAGE_PMD_SIZE;
2608         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2609         pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2610         /*
2611          * After this gup_fast can't run anymore. This also removes
2612          * any huge TLB entry from the CPU so we won't allow
2613          * huge and small TLB entries for the same virtual address
2614          * to avoid the risk of CPU bugs in that area.
2615          */
2616         _pmd = pmdp_collapse_flush(vma, address, pmd);
2617         spin_unlock(pmd_ptl);
2618         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2619
2620         spin_lock(pte_ptl);
2621         isolated = __collapse_huge_page_isolate(vma, address, pte);
2622         spin_unlock(pte_ptl);
2623
2624         if (unlikely(!isolated)) {
2625                 pte_unmap(pte);
2626                 spin_lock(pmd_ptl);
2627                 BUG_ON(!pmd_none(*pmd));
2628                 /*
2629                  * We can only use set_pmd_at when establishing
2630                  * hugepmds and never for establishing regular pmds that
2631                  * points to regular pagetables. Use pmd_populate for that
2632                  */
2633                 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2634                 spin_unlock(pmd_ptl);
2635                 anon_vma_unlock_write(vma->anon_vma);
2636                 goto out;
2637         }
2638
2639         /*
2640          * All pages are isolated and locked so anon_vma rmap
2641          * can't run anymore.
2642          */
2643         anon_vma_unlock_write(vma->anon_vma);
2644
2645         __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2646         pte_unmap(pte);
2647         __SetPageUptodate(new_page);
2648         pgtable = pmd_pgtable(_pmd);
2649
2650         _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2651         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2652
2653         /*
2654          * spin_lock() below is not the equivalent of smp_wmb(), so
2655          * this is needed to avoid the copy_huge_page writes to become
2656          * visible after the set_pmd_at() write.
2657          */
2658         smp_wmb();
2659
2660         spin_lock(pmd_ptl);
2661         BUG_ON(!pmd_none(*pmd));
2662         page_add_new_anon_rmap(new_page, vma, address);
2663         mem_cgroup_commit_charge(new_page, memcg, false);
2664         lru_cache_add_active_or_unevictable(new_page, vma);
2665         pgtable_trans_huge_deposit(mm, pmd, pgtable);
2666         set_pmd_at(mm, address, pmd, _pmd);
2667         update_mmu_cache_pmd(vma, address, pmd);
2668         spin_unlock(pmd_ptl);
2669
2670         *hpage = NULL;
2671
2672         khugepaged_pages_collapsed++;
2673 out_up_write:
2674         up_write(&mm->mmap_sem);
2675         return;
2676
2677 out:
2678         mem_cgroup_cancel_charge(new_page, memcg);
2679         goto out_up_write;
2680 }
2681
2682 static int khugepaged_scan_pmd(struct mm_struct *mm,
2683                                struct vm_area_struct *vma,
2684                                unsigned long address,
2685                                struct page **hpage)
2686 {
2687         pmd_t *pmd;
2688         pte_t *pte, *_pte;
2689         int ret = 0, none_or_zero = 0;
2690         struct page *page;
2691         unsigned long _address;
2692         spinlock_t *ptl;
2693         int node = NUMA_NO_NODE;
2694         bool writable = false, referenced = false;
2695
2696         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2697
2698         pmd = mm_find_pmd(mm, address);
2699         if (!pmd)
2700                 goto out;
2701
2702         memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2703         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2704         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2705              _pte++, _address += PAGE_SIZE) {
2706                 pte_t pteval = *_pte;
2707                 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2708                         if (!userfaultfd_armed(vma) &&
2709                             ++none_or_zero <= khugepaged_max_ptes_none)
2710                                 continue;
2711                         else
2712                                 goto out_unmap;
2713                 }
2714                 if (!pte_present(pteval))
2715                         goto out_unmap;
2716                 if (pte_write(pteval))
2717                         writable = true;
2718
2719                 page = vm_normal_page(vma, _address, pteval);
2720                 if (unlikely(!page))
2721                         goto out_unmap;
2722                 /*
2723                  * Record which node the original page is from and save this
2724                  * information to khugepaged_node_load[].
2725                  * Khupaged will allocate hugepage from the node has the max
2726                  * hit record.
2727                  */
2728                 node = page_to_nid(page);
2729                 if (khugepaged_scan_abort(node))
2730                         goto out_unmap;
2731                 khugepaged_node_load[node]++;
2732                 VM_BUG_ON_PAGE(PageCompound(page), page);
2733                 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2734                         goto out_unmap;
2735                 /*
2736                  * cannot use mapcount: can't collapse if there's a gup pin.
2737                  * The page must only be referenced by the scanned process
2738                  * and page swap cache.
2739                  */
2740                 if (page_count(page) != 1 + !!PageSwapCache(page))
2741                         goto out_unmap;
2742                 if (pte_young(pteval) ||
2743                     page_is_young(page) || PageReferenced(page) ||
2744                     mmu_notifier_test_young(vma->vm_mm, address))
2745                         referenced = true;
2746         }
2747         if (referenced && writable)
2748                 ret = 1;
2749 out_unmap:
2750         pte_unmap_unlock(pte, ptl);
2751         if (ret) {
2752                 node = khugepaged_find_target_node();
2753                 /* collapse_huge_page will return with the mmap_sem released */
2754                 collapse_huge_page(mm, address, hpage, vma, node);
2755         }
2756 out:
2757         return ret;
2758 }
2759
2760 static void collect_mm_slot(struct mm_slot *mm_slot)
2761 {
2762         struct mm_struct *mm = mm_slot->mm;
2763
2764         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2765
2766         if (khugepaged_test_exit(mm)) {
2767                 /* free mm_slot */
2768                 hash_del(&mm_slot->hash);
2769                 list_del(&mm_slot->mm_node);
2770
2771                 /*
2772                  * Not strictly needed because the mm exited already.
2773                  *
2774                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2775                  */
2776
2777                 /* khugepaged_mm_lock actually not necessary for the below */
2778                 free_mm_slot(mm_slot);
2779                 mmdrop(mm);
2780         }
2781 }
2782
2783 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2784                                             struct page **hpage)
2785         __releases(&khugepaged_mm_lock)
2786         __acquires(&khugepaged_mm_lock)
2787 {
2788         struct mm_slot *mm_slot;
2789         struct mm_struct *mm;
2790         struct vm_area_struct *vma;
2791         int progress = 0;
2792
2793         VM_BUG_ON(!pages);
2794         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2795
2796         if (khugepaged_scan.mm_slot)
2797                 mm_slot = khugepaged_scan.mm_slot;
2798         else {
2799                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2800                                      struct mm_slot, mm_node);
2801                 khugepaged_scan.address = 0;
2802                 khugepaged_scan.mm_slot = mm_slot;
2803         }
2804         spin_unlock(&khugepaged_mm_lock);
2805
2806         mm = mm_slot->mm;
2807         down_read(&mm->mmap_sem);
2808         if (unlikely(khugepaged_test_exit(mm)))
2809                 vma = NULL;
2810         else
2811                 vma = find_vma(mm, khugepaged_scan.address);
2812
2813         progress++;
2814         for (; vma; vma = vma->vm_next) {
2815                 unsigned long hstart, hend;
2816
2817                 cond_resched();
2818                 if (unlikely(khugepaged_test_exit(mm))) {
2819                         progress++;
2820                         break;
2821                 }
2822                 if (!hugepage_vma_check(vma)) {
2823 skip:
2824                         progress++;
2825                         continue;
2826                 }
2827                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2828                 hend = vma->vm_end & HPAGE_PMD_MASK;
2829                 if (hstart >= hend)
2830                         goto skip;
2831                 if (khugepaged_scan.address > hend)
2832                         goto skip;
2833                 if (khugepaged_scan.address < hstart)
2834                         khugepaged_scan.address = hstart;
2835                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2836
2837                 while (khugepaged_scan.address < hend) {
2838                         int ret;
2839                         cond_resched();
2840                         if (unlikely(khugepaged_test_exit(mm)))
2841                                 goto breakouterloop;
2842
2843                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2844                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2845                                   hend);
2846                         ret = khugepaged_scan_pmd(mm, vma,
2847                                                   khugepaged_scan.address,
2848                                                   hpage);
2849                         /* move to next address */
2850                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2851                         progress += HPAGE_PMD_NR;
2852                         if (ret)
2853                                 /* we released mmap_sem so break loop */
2854                                 goto breakouterloop_mmap_sem;
2855                         if (progress >= pages)
2856                                 goto breakouterloop;
2857                 }
2858         }
2859 breakouterloop:
2860         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2861 breakouterloop_mmap_sem:
2862
2863         spin_lock(&khugepaged_mm_lock);
2864         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2865         /*
2866          * Release the current mm_slot if this mm is about to die, or
2867          * if we scanned all vmas of this mm.
2868          */
2869         if (khugepaged_test_exit(mm) || !vma) {
2870                 /*
2871                  * Make sure that if mm_users is reaching zero while
2872                  * khugepaged runs here, khugepaged_exit will find
2873                  * mm_slot not pointing to the exiting mm.
2874                  */
2875                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2876                         khugepaged_scan.mm_slot = list_entry(
2877                                 mm_slot->mm_node.next,
2878                                 struct mm_slot, mm_node);
2879                         khugepaged_scan.address = 0;
2880                 } else {
2881                         khugepaged_scan.mm_slot = NULL;
2882                         khugepaged_full_scans++;
2883                 }
2884
2885                 collect_mm_slot(mm_slot);
2886         }
2887
2888         return progress;
2889 }
2890
2891 static int khugepaged_has_work(void)
2892 {
2893         return !list_empty(&khugepaged_scan.mm_head) &&
2894                 khugepaged_enabled();
2895 }
2896
2897 static int khugepaged_wait_event(void)
2898 {
2899         return !list_empty(&khugepaged_scan.mm_head) ||
2900                 kthread_should_stop();
2901 }
2902
2903 static void khugepaged_do_scan(void)
2904 {
2905         struct page *hpage = NULL;
2906         unsigned int progress = 0, pass_through_head = 0;
2907         unsigned int pages = khugepaged_pages_to_scan;
2908         bool wait = true;
2909
2910         barrier(); /* write khugepaged_pages_to_scan to local stack */
2911
2912         while (progress < pages) {
2913                 if (!khugepaged_prealloc_page(&hpage, &wait))
2914                         break;
2915
2916                 cond_resched();
2917
2918                 if (unlikely(kthread_should_stop() || try_to_freeze()))
2919                         break;
2920
2921                 spin_lock(&khugepaged_mm_lock);
2922                 if (!khugepaged_scan.mm_slot)
2923                         pass_through_head++;
2924                 if (khugepaged_has_work() &&
2925                     pass_through_head < 2)
2926                         progress += khugepaged_scan_mm_slot(pages - progress,
2927                                                             &hpage);
2928                 else
2929                         progress = pages;
2930                 spin_unlock(&khugepaged_mm_lock);
2931         }
2932
2933         if (!IS_ERR_OR_NULL(hpage))
2934                 put_page(hpage);
2935 }
2936
2937 static void khugepaged_wait_work(void)
2938 {
2939         if (khugepaged_has_work()) {
2940                 if (!khugepaged_scan_sleep_millisecs)
2941                         return;
2942
2943                 wait_event_freezable_timeout(khugepaged_wait,
2944                                              kthread_should_stop(),
2945                         msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2946                 return;
2947         }
2948
2949         if (khugepaged_enabled())
2950                 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2951 }
2952
2953 static int khugepaged(void *none)
2954 {
2955         struct mm_slot *mm_slot;
2956
2957         set_freezable();
2958         set_user_nice(current, MAX_NICE);
2959
2960         while (!kthread_should_stop()) {
2961                 khugepaged_do_scan();
2962                 khugepaged_wait_work();
2963         }
2964
2965         spin_lock(&khugepaged_mm_lock);
2966         mm_slot = khugepaged_scan.mm_slot;
2967         khugepaged_scan.mm_slot = NULL;
2968         if (mm_slot)
2969                 collect_mm_slot(mm_slot);
2970         spin_unlock(&khugepaged_mm_lock);
2971         return 0;
2972 }
2973
2974 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2975                 unsigned long haddr, pmd_t *pmd)
2976 {
2977         struct mm_struct *mm = vma->vm_mm;
2978         pgtable_t pgtable;
2979         pmd_t _pmd;
2980         int i;
2981
2982         pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2983         /* leave pmd empty until pte is filled */
2984
2985         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2986         pmd_populate(mm, &_pmd, pgtable);
2987
2988         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2989                 pte_t *pte, entry;
2990                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2991                 entry = pte_mkspecial(entry);
2992                 pte = pte_offset_map(&_pmd, haddr);
2993                 VM_BUG_ON(!pte_none(*pte));
2994                 set_pte_at(mm, haddr, pte, entry);
2995                 pte_unmap(pte);
2996         }
2997         smp_wmb(); /* make pte visible before pmd */
2998         pmd_populate(mm, pmd, pgtable);
2999         put_huge_zero_page();
3000 }
3001
3002 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
3003                 pmd_t *pmd)
3004 {
3005         spinlock_t *ptl;
3006         struct page *page = NULL;
3007         struct mm_struct *mm = vma->vm_mm;
3008         unsigned long haddr = address & HPAGE_PMD_MASK;
3009         unsigned long mmun_start;       /* For mmu_notifiers */
3010         unsigned long mmun_end;         /* For mmu_notifiers */
3011
3012         BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
3013
3014         mmun_start = haddr;
3015         mmun_end   = haddr + HPAGE_PMD_SIZE;
3016 again:
3017         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
3018         ptl = pmd_lock(mm, pmd);
3019         if (unlikely(!pmd_trans_huge(*pmd)))
3020                 goto unlock;
3021         if (vma_is_dax(vma)) {
3022                 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
3023                 if (is_huge_zero_pmd(_pmd))
3024                         put_huge_zero_page();
3025         } else if (is_huge_zero_pmd(*pmd)) {
3026                 __split_huge_zero_page_pmd(vma, haddr, pmd);
3027         } else {
3028                 page = pmd_page(*pmd);
3029                 VM_BUG_ON_PAGE(!page_count(page), page);
3030                 get_page(page);
3031         }
3032  unlock:
3033         spin_unlock(ptl);
3034         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
3035
3036         if (!page)
3037                 return;
3038
3039         split_huge_page(page);
3040         put_page(page);
3041
3042         /*
3043          * We don't always have down_write of mmap_sem here: a racing
3044          * do_huge_pmd_wp_page() might have copied-on-write to another
3045          * huge page before our split_huge_page() got the anon_vma lock.
3046          */
3047         if (unlikely(pmd_trans_huge(*pmd)))
3048                 goto again;
3049 }
3050
3051 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
3052                 pmd_t *pmd)
3053 {
3054         struct vm_area_struct *vma;
3055
3056         vma = find_vma(mm, address);
3057         BUG_ON(vma == NULL);
3058         split_huge_page_pmd(vma, address, pmd);
3059 }
3060
3061 static void split_huge_page_address(struct mm_struct *mm,
3062                                     unsigned long address)
3063 {
3064         pgd_t *pgd;
3065         pud_t *pud;
3066         pmd_t *pmd;
3067
3068         VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
3069
3070         pgd = pgd_offset(mm, address);
3071         if (!pgd_present(*pgd))
3072                 return;
3073
3074         pud = pud_offset(pgd, address);
3075         if (!pud_present(*pud))
3076                 return;
3077
3078         pmd = pmd_offset(pud, address);
3079         if (!pmd_present(*pmd))
3080                 return;
3081         /*
3082          * Caller holds the mmap_sem write mode, so a huge pmd cannot
3083          * materialize from under us.
3084          */
3085         split_huge_page_pmd_mm(mm, address, pmd);
3086 }
3087
3088 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3089                              unsigned long start,
3090                              unsigned long end,
3091                              long adjust_next)
3092 {
3093         /*
3094          * If the new start address isn't hpage aligned and it could
3095          * previously contain an hugepage: check if we need to split
3096          * an huge pmd.
3097          */
3098         if (start & ~HPAGE_PMD_MASK &&
3099             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3100             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3101                 split_huge_page_address(vma->vm_mm, start);
3102
3103         /*
3104          * If the new end address isn't hpage aligned and it could
3105          * previously contain an hugepage: check if we need to split
3106          * an huge pmd.
3107          */
3108         if (end & ~HPAGE_PMD_MASK &&
3109             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3110             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3111                 split_huge_page_address(vma->vm_mm, end);
3112
3113         /*
3114          * If we're also updating the vma->vm_next->vm_start, if the new
3115          * vm_next->vm_start isn't page aligned and it could previously
3116          * contain an hugepage: check if we need to split an huge pmd.
3117          */
3118         if (adjust_next > 0) {
3119                 struct vm_area_struct *next = vma->vm_next;
3120                 unsigned long nstart = next->vm_start;
3121                 nstart += adjust_next << PAGE_SHIFT;
3122                 if (nstart & ~HPAGE_PMD_MASK &&
3123                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3124                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3125                         split_huge_page_address(next->vm_mm, nstart);
3126         }
3127 }