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/swapops.h>
  20 #include <linux/dax.h>
  21 #include <linux/kthread.h>
  22 #include <linux/khugepaged.h>
  23 #include <linux/freezer.h>
  24 #include <linux/pfn_t.h>
  25 #include <linux/mman.h>
  26 #include <linux/memremap.h>
  27 #include <linux/pagemap.h>
  28 #include <linux/debugfs.h>
  29 #include <linux/migrate.h>
  30 #include <linux/hashtable.h>
  31 #include <linux/userfaultfd_k.h>
  32 #include <linux/page_idle.h>
  33
  34 #include <asm/tlb.h>
  35 #include <asm/pgalloc.h>
  36 #include "internal.h"
  37
  38 enum scan_result {
  39         SCAN_FAIL,
  40         SCAN_SUCCEED,
  41         SCAN_PMD_NULL,
  42         SCAN_EXCEED_NONE_PTE,
  43         SCAN_PTE_NON_PRESENT,
  44         SCAN_PAGE_RO,
  45         SCAN_NO_REFERENCED_PAGE,
  46         SCAN_PAGE_NULL,
  47         SCAN_SCAN_ABORT,
  48         SCAN_PAGE_COUNT,
  49         SCAN_PAGE_LRU,
  50         SCAN_PAGE_LOCK,
  51         SCAN_PAGE_ANON,
  52         SCAN_PAGE_COMPOUND,
  53         SCAN_ANY_PROCESS,
  54         SCAN_VMA_NULL,
  55         SCAN_VMA_CHECK,
  56         SCAN_ADDRESS_RANGE,
  57         SCAN_SWAP_CACHE_PAGE,
  58         SCAN_DEL_PAGE_LRU,
  59         SCAN_ALLOC_HUGE_PAGE_FAIL,
  60         SCAN_CGROUP_CHARGE_FAIL
  61 };
  62
  63 #define CREATE_TRACE_POINTS
  64 #include <trace/events/huge_memory.h>
  65
  66 /*
  67  * By default transparent hugepage support is disabled in order that avoid
  68  * to risk increase the memory footprint of applications without a guaranteed
  69  * benefit. When transparent hugepage support is enabled, is for all mappings,
  70  * and khugepaged scans all mappings.
  71  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  72  * for all hugepage allocations.
  73  */
  74 unsigned long transparent_hugepage_flags __read_mostly =
  75 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  76         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  77 #endif
  78 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  79         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  80 #endif
  81         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  82         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  83         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  84
  85 /* default scan 8*512 pte (or vmas) every 30 second */
  86 static unsigned int khugepaged_pages_to_scan __read_mostly;
  87 static unsigned int khugepaged_pages_collapsed;
  88 static unsigned int khugepaged_full_scans;
  89 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
  90 /* during fragmentation poll the hugepage allocator once every minute */
  91 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
  92 static unsigned long khugepaged_sleep_expire;
  93 static struct task_struct *khugepaged_thread __read_mostly;
  94 static DEFINE_MUTEX(khugepaged_mutex);
  95 static DEFINE_SPINLOCK(khugepaged_mm_lock);
  96 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  97 /*
  98  * default collapse hugepages if there is at least one pte mapped like
  99  * it would have happened if the vma was large enough during page
 100  * fault.
 101  */
 102 static unsigned int khugepaged_max_ptes_none __read_mostly;
 103
 104 static int khugepaged(void *none);
 105 static int khugepaged_slab_init(void);
 106 static void khugepaged_slab_exit(void);
 107
 108 #define MM_SLOTS_HASH_BITS 10
 109 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
 110
 111 static struct kmem_cache *mm_slot_cache __read_mostly;
 112
 113 /**
 114  * struct mm_slot - hash lookup from mm to mm_slot
 115  * @hash: hash collision list
 116  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
 117  * @mm: the mm that this information is valid for
 118  */
 119 struct mm_slot {
 120         struct hlist_node hash;
 121         struct list_head mm_node;
 122         struct mm_struct *mm;
 123 };
 124
 125 /**
 126  * struct khugepaged_scan - cursor for scanning
 127  * @mm_head: the head of the mm list to scan
 128  * @mm_slot: the current mm_slot we are scanning
 129  * @address: the next address inside that to be scanned
 130  *
 131  * There is only the one khugepaged_scan instance of this cursor structure.
 132  */
 133 struct khugepaged_scan {
 134         struct list_head mm_head;
 135         struct mm_slot *mm_slot;
 136         unsigned long address;
 137 };
 138 static struct khugepaged_scan khugepaged_scan = {
 139         .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
 140 };
 141
 142 static struct shrinker deferred_split_shrinker;
 143
 144 static void set_recommended_min_free_kbytes(void)
 145 {
 146         struct zone *zone;
 147         int nr_zones = 0;
 148         unsigned long recommended_min;
 149
 150         for_each_populated_zone(zone)
 151                 nr_zones++;
 152
 153         /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
 154         recommended_min = pageblock_nr_pages * nr_zones * 2;
 155
 156         /*
 157          * Make sure that on average at least two pageblocks are almost free
 158          * of another type, one for a migratetype to fall back to and a
 159          * second to avoid subsequent fallbacks of other types There are 3
 160          * MIGRATE_TYPES we care about.
 161          */
 162         recommended_min += pageblock_nr_pages * nr_zones *
 163                            MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
 164
 165         /* don't ever allow to reserve more than 5% of the lowmem */
 166         recommended_min = min(recommended_min,
 167                               (unsigned long) nr_free_buffer_pages() / 20);
 168         recommended_min <<= (PAGE_SHIFT-10);
 169
 170         if (recommended_min > min_free_kbytes) {
 171                 if (user_min_free_kbytes >= 0)
 172                         pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
 173                                 min_free_kbytes, recommended_min);
 174
 175                 min_free_kbytes = recommended_min;
 176         }
 177         setup_per_zone_wmarks();
 178 }
 179
 180 static int start_stop_khugepaged(void)
 181 {
 182         int err = 0;
 183         if (khugepaged_enabled()) {
 184                 if (!khugepaged_thread)
 185                         khugepaged_thread = kthread_run(khugepaged, NULL,
 186                                                         "khugepaged");
 187                 if (IS_ERR(khugepaged_thread)) {
 188                         pr_err("khugepaged: kthread_run(khugepaged) failed\n");
 189                         err = PTR_ERR(khugepaged_thread);
 190                         khugepaged_thread = NULL;
 191                         goto fail;
 192                 }
 193
 194                 if (!list_empty(&khugepaged_scan.mm_head))
 195                         wake_up_interruptible(&khugepaged_wait);
 196
 197                 set_recommended_min_free_kbytes();
 198         } else if (khugepaged_thread) {
 199                 kthread_stop(khugepaged_thread);
 200                 khugepaged_thread = NULL;
 201         }
 202 fail:
 203         return err;
 204 }
 205
 206 static atomic_t huge_zero_refcount;
 207 struct page *huge_zero_page __read_mostly;
 208
 209 struct page *get_huge_zero_page(void)
 210 {
 211         struct page *zero_page;
 212 retry:
 213         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 214                 return READ_ONCE(huge_zero_page);
 215
 216         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 217                         HPAGE_PMD_ORDER);
 218         if (!zero_page) {
 219                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 220                 return NULL;
 221         }
 222         count_vm_event(THP_ZERO_PAGE_ALLOC);
 223         preempt_disable();
 224         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 225                 preempt_enable();
 226                 __free_pages(zero_page, compound_order(zero_page));
 227                 goto retry;
 228         }
 229
 230         /* We take additional reference here. It will be put back by shrinker */
 231         atomic_set(&huge_zero_refcount, 2);
 232         preempt_enable();
 233         return READ_ONCE(huge_zero_page);
 234 }
 235
 236 void put_huge_zero_page(void)
 237 {
 238         /*
 239          * Counter should never go to zero here. Only shrinker can put
 240          * last reference.
 241          */
 242         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 243 }
 244
 245 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 246                                         struct shrink_control *sc)
 247 {
 248         /* we can free zero page only if last reference remains */
 249         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 250 }
 251
 252 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 253                                        struct shrink_control *sc)
 254 {
 255         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 256                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 257                 BUG_ON(zero_page == NULL);
 258                 __free_pages(zero_page, compound_order(zero_page));
 259                 return HPAGE_PMD_NR;
 260         }
 261
 262         return 0;
 263 }
 264
 265 static struct shrinker huge_zero_page_shrinker = {
 266         .count_objects = shrink_huge_zero_page_count,
 267         .scan_objects = shrink_huge_zero_page_scan,
 268         .seeks = DEFAULT_SEEKS,
 269 };
 270
 271 #ifdef CONFIG_SYSFS
 272
 273 static ssize_t triple_flag_store(struct kobject *kobj,
 274                                  struct kobj_attribute *attr,
 275                                  const char *buf, size_t count,
 276                                  enum transparent_hugepage_flag enabled,
 277                                  enum transparent_hugepage_flag deferred,
 278                                  enum transparent_hugepage_flag req_madv)
 279 {
 280         if (!memcmp("defer", buf,
 281                     min(sizeof("defer")-1, count))) {
 282                 if (enabled == deferred)
 283                         return -EINVAL;
 284                 clear_bit(enabled, &transparent_hugepage_flags);
 285                 clear_bit(req_madv, &transparent_hugepage_flags);
 286                 set_bit(deferred, &transparent_hugepage_flags);
 287         } else if (!memcmp("always", buf,
 288                     min(sizeof("always")-1, count))) {
 289                 clear_bit(deferred, &transparent_hugepage_flags);
 290                 clear_bit(req_madv, &transparent_hugepage_flags);
 291                 set_bit(enabled, &transparent_hugepage_flags);
 292         } else if (!memcmp("madvise", buf,
 293                            min(sizeof("madvise")-1, count))) {
 294                 clear_bit(enabled, &transparent_hugepage_flags);
 295                 clear_bit(deferred, &transparent_hugepage_flags);
 296                 set_bit(req_madv, &transparent_hugepage_flags);
 297         } else if (!memcmp("never", buf,
 298                            min(sizeof("never")-1, count))) {
 299                 clear_bit(enabled, &transparent_hugepage_flags);
 300                 clear_bit(req_madv, &transparent_hugepage_flags);
 301                 clear_bit(deferred, &transparent_hugepage_flags);
 302         } else
 303                 return -EINVAL;
 304
 305         return count;
 306 }
 307
 308 static ssize_t enabled_show(struct kobject *kobj,
 309                             struct kobj_attribute *attr, char *buf)
 310 {
 311         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 312                 return sprintf(buf, "[always] madvise never\n");
 313         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 314                 return sprintf(buf, "always [madvise] never\n");
 315         else
 316                 return sprintf(buf, "always madvise [never]\n");
 317 }
 318
 319 static ssize_t enabled_store(struct kobject *kobj,
 320                              struct kobj_attribute *attr,
 321                              const char *buf, size_t count)
 322 {
 323         ssize_t ret;
 324
 325         ret = triple_flag_store(kobj, attr, buf, count,
 326                                 TRANSPARENT_HUGEPAGE_FLAG,
 327                                 TRANSPARENT_HUGEPAGE_FLAG,
 328                                 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
 329
 330         if (ret > 0) {
 331                 int err;
 332
 333                 mutex_lock(&khugepaged_mutex);
 334                 err = start_stop_khugepaged();
 335                 mutex_unlock(&khugepaged_mutex);
 336
 337                 if (err)
 338                         ret = err;
 339         }
 340
 341         return ret;
 342 }
 343 static struct kobj_attribute enabled_attr =
 344         __ATTR(enabled, 0644, enabled_show, enabled_store);
 345
 346 static ssize_t single_flag_show(struct kobject *kobj,
 347                                 struct kobj_attribute *attr, char *buf,
 348                                 enum transparent_hugepage_flag flag)
 349 {
 350         return sprintf(buf, "%d\n",
 351                        !!test_bit(flag, &transparent_hugepage_flags));
 352 }
 353
 354 static ssize_t single_flag_store(struct kobject *kobj,
 355                                  struct kobj_attribute *attr,
 356                                  const char *buf, size_t count,
 357                                  enum transparent_hugepage_flag flag)
 358 {
 359         unsigned long value;
 360         int ret;
 361
 362         ret = kstrtoul(buf, 10, &value);
 363         if (ret < 0)
 364                 return ret;
 365         if (value > 1)
 366                 return -EINVAL;
 367
 368         if (value)
 369                 set_bit(flag, &transparent_hugepage_flags);
 370         else
 371                 clear_bit(flag, &transparent_hugepage_flags);
 372
 373         return count;
 374 }
 375
 376 /*
 377  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 378  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 379  * memory just to allocate one more hugepage.
 380  */
 381 static ssize_t defrag_show(struct kobject *kobj,
 382                            struct kobj_attribute *attr, char *buf)
 383 {
 384         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 385                 return sprintf(buf, "[always] defer madvise never\n");
 386         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 387                 return sprintf(buf, "always [defer] madvise never\n");
 388         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 389                 return sprintf(buf, "always defer [madvise] never\n");
 390         else
 391                 return sprintf(buf, "always defer madvise [never]\n");
 392
 393 }
 394 static ssize_t defrag_store(struct kobject *kobj,
 395                             struct kobj_attribute *attr,
 396                             const char *buf, size_t count)
 397 {
 398         return triple_flag_store(kobj, attr, buf, count,
 399                                  TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
 400                                  TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
 401                                  TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
 402 }
 403 static struct kobj_attribute defrag_attr =
 404         __ATTR(defrag, 0644, defrag_show, defrag_store);
 405
 406 static ssize_t use_zero_page_show(struct kobject *kobj,
 407                 struct kobj_attribute *attr, char *buf)
 408 {
 409         return single_flag_show(kobj, attr, buf,
 410                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 411 }
 412 static ssize_t use_zero_page_store(struct kobject *kobj,
 413                 struct kobj_attribute *attr, const char *buf, size_t count)
 414 {
 415         return single_flag_store(kobj, attr, buf, count,
 416                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 417 }
 418 static struct kobj_attribute use_zero_page_attr =
 419         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 420 #ifdef CONFIG_DEBUG_VM
 421 static ssize_t debug_cow_show(struct kobject *kobj,
 422                                 struct kobj_attribute *attr, char *buf)
 423 {
 424         return single_flag_show(kobj, attr, buf,
 425                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 426 }
 427 static ssize_t debug_cow_store(struct kobject *kobj,
 428                                struct kobj_attribute *attr,
 429                                const char *buf, size_t count)
 430 {
 431         return single_flag_store(kobj, attr, buf, count,
 432                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 433 }
 434 static struct kobj_attribute debug_cow_attr =
 435         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 436 #endif /* CONFIG_DEBUG_VM */
 437
 438 static struct attribute *hugepage_attr[] = {
 439         &enabled_attr.attr,
 440         &defrag_attr.attr,
 441         &use_zero_page_attr.attr,
 442 #ifdef CONFIG_DEBUG_VM
 443         &debug_cow_attr.attr,
 444 #endif
 445         NULL,
 446 };
 447
 448 static struct attribute_group hugepage_attr_group = {
 449         .attrs = hugepage_attr,
 450 };
 451
 452 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
 453                                          struct kobj_attribute *attr,
 454                                          char *buf)
 455 {
 456         return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
 457 }
 458
 459 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
 460                                           struct kobj_attribute *attr,
 461                                           const char *buf, size_t count)
 462 {
 463         unsigned long msecs;
 464         int err;
 465
 466         err = kstrtoul(buf, 10, &msecs);
 467         if (err || msecs > UINT_MAX)
 468                 return -EINVAL;
 469
 470         khugepaged_scan_sleep_millisecs = msecs;
 471         khugepaged_sleep_expire = 0;
 472         wake_up_interruptible(&khugepaged_wait);
 473
 474         return count;
 475 }
 476 static struct kobj_attribute scan_sleep_millisecs_attr =
 477         __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
 478                scan_sleep_millisecs_store);
 479
 480 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
 481                                           struct kobj_attribute *attr,
 482                                           char *buf)
 483 {
 484         return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
 485 }
 486
 487 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
 488                                            struct kobj_attribute *attr,
 489                                            const char *buf, size_t count)
 490 {
 491         unsigned long msecs;
 492         int err;
 493
 494         err = kstrtoul(buf, 10, &msecs);
 495         if (err || msecs > UINT_MAX)
 496                 return -EINVAL;
 497
 498         khugepaged_alloc_sleep_millisecs = msecs;
 499         khugepaged_sleep_expire = 0;
 500         wake_up_interruptible(&khugepaged_wait);
 501
 502         return count;
 503 }
 504 static struct kobj_attribute alloc_sleep_millisecs_attr =
 505         __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
 506                alloc_sleep_millisecs_store);
 507
 508 static ssize_t pages_to_scan_show(struct kobject *kobj,
 509                                   struct kobj_attribute *attr,
 510                                   char *buf)
 511 {
 512         return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
 513 }
 514 static ssize_t pages_to_scan_store(struct kobject *kobj,
 515                                    struct kobj_attribute *attr,
 516                                    const char *buf, size_t count)
 517 {
 518         int err;
 519         unsigned long pages;
 520
 521         err = kstrtoul(buf, 10, &pages);
 522         if (err || !pages || pages > UINT_MAX)
 523                 return -EINVAL;
 524
 525         khugepaged_pages_to_scan = pages;
 526
 527         return count;
 528 }
 529 static struct kobj_attribute pages_to_scan_attr =
 530         __ATTR(pages_to_scan, 0644, pages_to_scan_show,
 531                pages_to_scan_store);
 532
 533 static ssize_t pages_collapsed_show(struct kobject *kobj,
 534                                     struct kobj_attribute *attr,
 535                                     char *buf)
 536 {
 537         return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
 538 }
 539 static struct kobj_attribute pages_collapsed_attr =
 540         __ATTR_RO(pages_collapsed);
 541
 542 static ssize_t full_scans_show(struct kobject *kobj,
 543                                struct kobj_attribute *attr,
 544                                char *buf)
 545 {
 546         return sprintf(buf, "%u\n", khugepaged_full_scans);
 547 }
 548 static struct kobj_attribute full_scans_attr =
 549         __ATTR_RO(full_scans);
 550
 551 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
 552                                       struct kobj_attribute *attr, char *buf)
 553 {
 554         return single_flag_show(kobj, attr, buf,
 555                                 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 556 }
 557 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
 558                                        struct kobj_attribute *attr,
 559                                        const char *buf, size_t count)
 560 {
 561         return single_flag_store(kobj, attr, buf, count,
 562                                  TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
 563 }
 564 static struct kobj_attribute khugepaged_defrag_attr =
 565         __ATTR(defrag, 0644, khugepaged_defrag_show,
 566                khugepaged_defrag_store);
 567
 568 /*
 569  * max_ptes_none controls if khugepaged should collapse hugepages over
 570  * any unmapped ptes in turn potentially increasing the memory
 571  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 572  * reduce the available free memory in the system as it
 573  * runs. Increasing max_ptes_none will instead potentially reduce the
 574  * free memory in the system during the khugepaged scan.
 575  */
 576 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
 577                                              struct kobj_attribute *attr,
 578                                              char *buf)
 579 {
 580         return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
 581 }
 582 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
 583                                               struct kobj_attribute *attr,
 584                                               const char *buf, size_t count)
 585 {
 586         int err;
 587         unsigned long max_ptes_none;
 588
 589         err = kstrtoul(buf, 10, &max_ptes_none);
 590         if (err || max_ptes_none > HPAGE_PMD_NR-1)
 591                 return -EINVAL;
 592
 593         khugepaged_max_ptes_none = max_ptes_none;
 594
 595         return count;
 596 }
 597 static struct kobj_attribute khugepaged_max_ptes_none_attr =
 598         __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
 599                khugepaged_max_ptes_none_store);
 600
 601 static struct attribute *khugepaged_attr[] = {
 602         &khugepaged_defrag_attr.attr,
 603         &khugepaged_max_ptes_none_attr.attr,
 604         &pages_to_scan_attr.attr,
 605         &pages_collapsed_attr.attr,
 606         &full_scans_attr.attr,
 607         &scan_sleep_millisecs_attr.attr,
 608         &alloc_sleep_millisecs_attr.attr,
 609         NULL,
 610 };
 611
 612 static struct attribute_group khugepaged_attr_group = {
 613         .attrs = khugepaged_attr,
 614         .name = "khugepaged",
 615 };
 616
 617 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 618 {
 619         int err;
 620
 621         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 622         if (unlikely(!*hugepage_kobj)) {
 623                 pr_err("failed to create transparent hugepage kobject\n");
 624                 return -ENOMEM;
 625         }
 626
 627         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 628         if (err) {
 629                 pr_err("failed to register transparent hugepage group\n");
 630                 goto delete_obj;
 631         }
 632
 633         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 634         if (err) {
 635                 pr_err("failed to register transparent hugepage group\n");
 636                 goto remove_hp_group;
 637         }
 638
 639         return 0;
 640
 641 remove_hp_group:
 642         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 643 delete_obj:
 644         kobject_put(*hugepage_kobj);
 645         return err;
 646 }
 647
 648 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 649 {
 650         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 651         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 652         kobject_put(hugepage_kobj);
 653 }
 654 #else
 655 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 656 {
 657         return 0;
 658 }
 659
 660 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 661 {
 662 }
 663 #endif /* CONFIG_SYSFS */
 664
 665 static int __init hugepage_init(void)
 666 {
 667         int err;
 668         struct kobject *hugepage_kobj;
 669
 670         if (!has_transparent_hugepage()) {
 671                 transparent_hugepage_flags = 0;
 672                 return -EINVAL;
 673         }
 674
 675         khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
 676         khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
 677         /*
 678          * hugepages can't be allocated by the buddy allocator
 679          */
 680         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 681         /*
 682          * we use page->mapping and page->index in second tail page
 683          * as list_head: assuming THP order >= 2
 684          */
 685         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 686
 687         err = hugepage_init_sysfs(&hugepage_kobj);
 688         if (err)
 689                 goto err_sysfs;
 690
 691         err = khugepaged_slab_init();
 692         if (err)
 693                 goto err_slab;
 694
 695         err = register_shrinker(&huge_zero_page_shrinker);
 696         if (err)
 697                 goto err_hzp_shrinker;
 698         err = register_shrinker(&deferred_split_shrinker);
 699         if (err)
 700                 goto err_split_shrinker;
 701
 702         /*
 703          * By default disable transparent hugepages on smaller systems,
 704          * where the extra memory used could hurt more than TLB overhead
 705          * is likely to save.  The admin can still enable it through /sys.
 706          */
 707         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
 708                 transparent_hugepage_flags = 0;
 709                 return 0;
 710         }
 711
 712         err = start_stop_khugepaged();
 713         if (err)
 714                 goto err_khugepaged;
 715
 716         return 0;
 717 err_khugepaged:
 718         unregister_shrinker(&deferred_split_shrinker);
 719 err_split_shrinker:
 720         unregister_shrinker(&huge_zero_page_shrinker);
 721 err_hzp_shrinker:
 722         khugepaged_slab_exit();
 723 err_slab:
 724         hugepage_exit_sysfs(hugepage_kobj);
 725 err_sysfs:
 726         return err;
 727 }
 728 subsys_initcall(hugepage_init);
 729
 730 static int __init setup_transparent_hugepage(char *str)
 731 {
 732         int ret = 0;
 733         if (!str)
 734                 goto out;
 735         if (!strcmp(str, "always")) {
 736                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 737                         &transparent_hugepage_flags);
 738                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 739                           &transparent_hugepage_flags);
 740                 ret = 1;
 741         } else if (!strcmp(str, "madvise")) {
 742                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 743                           &transparent_hugepage_flags);
 744                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 745                         &transparent_hugepage_flags);
 746                 ret = 1;
 747         } else if (!strcmp(str, "never")) {
 748                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 749                           &transparent_hugepage_flags);
 750                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 751                           &transparent_hugepage_flags);
 752                 ret = 1;
 753         }
 754 out:
 755         if (!ret)
 756                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 757         return ret;
 758 }
 759 __setup("transparent_hugepage=", setup_transparent_hugepage);
 760
 761 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 762 {
 763         if (likely(vma->vm_flags & VM_WRITE))
 764                 pmd = pmd_mkwrite(pmd);
 765         return pmd;
 766 }
 767
 768 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
 769 {
 770         return pmd_mkhuge(mk_pmd(page, prot));
 771 }
 772
 773 static inline struct list_head *page_deferred_list(struct page *page)
 774 {
 775         /*
 776          * ->lru in the tail pages is occupied by compound_head.
 777          * Let's use ->mapping + ->index in the second tail page as list_head.
 778          */
 779         return (struct list_head *)&page[2].mapping;
 780 }
 781
 782 void prep_transhuge_page(struct page *page)
 783 {
 784         /*
 785          * we use page->mapping and page->indexlru in second tail page
 786          * as list_head: assuming THP order >= 2
 787          */
 788
 789         INIT_LIST_HEAD(page_deferred_list(page));
 790         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 791 }
 792
 793 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 794                                         struct vm_area_struct *vma,
 795                                         unsigned long address, pmd_t *pmd,
 796                                         struct page *page, gfp_t gfp,
 797                                         unsigned int flags)
 798 {
 799         struct mem_cgroup *memcg;
 800         pgtable_t pgtable;
 801         spinlock_t *ptl;
 802         unsigned long haddr = address & HPAGE_PMD_MASK;
 803
 804         VM_BUG_ON_PAGE(!PageCompound(page), page);
 805
 806         if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) {
 807                 put_page(page);
 808                 count_vm_event(THP_FAULT_FALLBACK);
 809                 return VM_FAULT_FALLBACK;
 810         }
 811
 812         pgtable = pte_alloc_one(mm, haddr);
 813         if (unlikely(!pgtable)) {
 814                 mem_cgroup_cancel_charge(page, memcg, true);
 815                 put_page(page);
 816                 return VM_FAULT_OOM;
 817         }
 818
 819         clear_huge_page(page, haddr, HPAGE_PMD_NR);
 820         /*
 821          * The memory barrier inside __SetPageUptodate makes sure that
 822          * clear_huge_page writes become visible before the set_pmd_at()
 823          * write.
 824          */
 825         __SetPageUptodate(page);
 826
 827         ptl = pmd_lock(mm, pmd);
 828         if (unlikely(!pmd_none(*pmd))) {
 829                 spin_unlock(ptl);
 830                 mem_cgroup_cancel_charge(page, memcg, true);
 831                 put_page(page);
 832                 pte_free(mm, pgtable);
 833         } else {
 834                 pmd_t entry;
 835
 836                 /* Deliver the page fault to userland */
 837                 if (userfaultfd_missing(vma)) {
 838                         int ret;
 839
 840                         spin_unlock(ptl);
 841                         mem_cgroup_cancel_charge(page, memcg, true);
 842                         put_page(page);
 843                         pte_free(mm, pgtable);
 844                         ret = handle_userfault(vma, address, flags,
 845                                                VM_UFFD_MISSING);
 846                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 847                         return ret;
 848                 }
 849
 850                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 851                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 852                 page_add_new_anon_rmap(page, vma, haddr, true);
 853                 mem_cgroup_commit_charge(page, memcg, false, true);
 854                 lru_cache_add_active_or_unevictable(page, vma);
 855                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 856                 set_pmd_at(mm, haddr, pmd, entry);
 857                 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 858                 atomic_long_inc(&mm->nr_ptes);
 859                 spin_unlock(ptl);
 860                 count_vm_event(THP_FAULT_ALLOC);
 861         }
 862
 863         return 0;
 864 }
 865
 866 /*
 867  * If THP is set to always then directly reclaim/compact as necessary
 868  * If set to defer then do no reclaim and defer to khugepaged
 869  * If set to madvise and the VMA is flagged then directly reclaim/compact
 870  */
 871 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 872 {
 873         gfp_t reclaim_flags = 0;
 874
 875         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags) &&
 876             (vma->vm_flags & VM_HUGEPAGE))
 877                 reclaim_flags = __GFP_DIRECT_RECLAIM;
 878         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 879                 reclaim_flags = __GFP_KSWAPD_RECLAIM;
 880         else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 881                 reclaim_flags = __GFP_DIRECT_RECLAIM;
 882
 883         return GFP_TRANSHUGE | reclaim_flags;
 884 }
 885
 886 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
 887 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
 888 {
 889         return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0);
 890 }
 891
 892 /* Caller must hold page table lock. */
 893 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 894                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 895                 struct page *zero_page)
 896 {
 897         pmd_t entry;
 898         if (!pmd_none(*pmd))
 899                 return false;
 900         entry = mk_pmd(zero_page, vma->vm_page_prot);
 901         entry = pmd_mkhuge(entry);
 902         if (pgtable)
 903                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 904         set_pmd_at(mm, haddr, pmd, entry);
 905         atomic_long_inc(&mm->nr_ptes);
 906         return true;
 907 }
 908
 909 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 910                                unsigned long address, pmd_t *pmd,
 911                                unsigned int flags)
 912 {
 913         gfp_t gfp;
 914         struct page *page;
 915         unsigned long haddr = address & HPAGE_PMD_MASK;
 916
 917         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
 918                 return VM_FAULT_FALLBACK;
 919         if (unlikely(anon_vma_prepare(vma)))
 920                 return VM_FAULT_OOM;
 921         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 922                 return VM_FAULT_OOM;
 923         if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
 924                         transparent_hugepage_use_zero_page()) {
 925                 spinlock_t *ptl;
 926                 pgtable_t pgtable;
 927                 struct page *zero_page;
 928                 bool set;
 929                 int ret;
 930                 pgtable = pte_alloc_one(mm, haddr);
 931                 if (unlikely(!pgtable))
 932                         return VM_FAULT_OOM;
 933                 zero_page = get_huge_zero_page();
 934                 if (unlikely(!zero_page)) {
 935                         pte_free(mm, pgtable);
 936                         count_vm_event(THP_FAULT_FALLBACK);
 937                         return VM_FAULT_FALLBACK;
 938                 }
 939                 ptl = pmd_lock(mm, pmd);
 940                 ret = 0;
 941                 set = false;
 942                 if (pmd_none(*pmd)) {
 943                         if (userfaultfd_missing(vma)) {
 944                                 spin_unlock(ptl);
 945                                 ret = handle_userfault(vma, address, flags,
 946                                                        VM_UFFD_MISSING);
 947                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 948                         } else {
 949                                 set_huge_zero_page(pgtable, mm, vma,
 950                                                    haddr, pmd,
 951                                                    zero_page);
 952                                 spin_unlock(ptl);
 953                                 set = true;
 954                         }
 955                 } else
 956                         spin_unlock(ptl);
 957                 if (!set) {
 958                         pte_free(mm, pgtable);
 959                         put_huge_zero_page();
 960                 }
 961                 return ret;
 962         }
 963         gfp = alloc_hugepage_direct_gfpmask(vma);
 964         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 965         if (unlikely(!page)) {
 966                 count_vm_event(THP_FAULT_FALLBACK);
 967                 return VM_FAULT_FALLBACK;
 968         }
 969         prep_transhuge_page(page);
 970         return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
 971                                             flags);
 972 }
 973
 974 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 975                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
 976 {
 977         struct mm_struct *mm = vma->vm_mm;
 978         pmd_t entry;
 979         spinlock_t *ptl;
 980
 981         ptl = pmd_lock(mm, pmd);
 982         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 983         if (pfn_t_devmap(pfn))
 984                 entry = pmd_mkdevmap(entry);
 985         if (write) {
 986                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 987                 entry = maybe_pmd_mkwrite(entry, vma);
 988         }
 989         set_pmd_at(mm, addr, pmd, entry);
 990         update_mmu_cache_pmd(vma, addr, pmd);
 991         spin_unlock(ptl);
 992 }
 993
 994 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 995                         pmd_t *pmd, pfn_t pfn, bool write)
 996 {
 997         pgprot_t pgprot = vma->vm_page_prot;
 998         /*
 999          * If we had pmd_special, we could avoid all these restrictions,
1000          * but we need to be consistent with PTEs and architectures that
1001          * can't support a 'special' bit.
1002          */
1003         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1004         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1005                                                 (VM_PFNMAP|VM_MIXEDMAP));
1006         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1007         BUG_ON(!pfn_t_devmap(pfn));
1008
1009         if (addr < vma->vm_start || addr >= vma->vm_end)
1010                 return VM_FAULT_SIGBUS;
1011         if (track_pfn_insert(vma, &pgprot, pfn))
1012                 return VM_FAULT_SIGBUS;
1013         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
1014         return VM_FAULT_NOPAGE;
1015 }
1016
1017 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1018                 pmd_t *pmd)
1019 {
1020         pmd_t _pmd;
1021
1022         /*
1023          * We should set the dirty bit only for FOLL_WRITE but for now
1024          * the dirty bit in the pmd is meaningless.  And if the dirty
1025          * bit will become meaningful and we'll only set it with
1026          * FOLL_WRITE, an atomic set_bit will be required on the pmd to
1027          * set the young bit, instead of the current set_pmd_at.
1028          */
1029         _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1030         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1031                                 pmd, _pmd,  1))
1032                 update_mmu_cache_pmd(vma, addr, pmd);
1033 }
1034
1035 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1036                 pmd_t *pmd, int flags)
1037 {
1038         unsigned long pfn = pmd_pfn(*pmd);
1039         struct mm_struct *mm = vma->vm_mm;
1040         struct dev_pagemap *pgmap;
1041         struct page *page;
1042
1043         assert_spin_locked(pmd_lockptr(mm, pmd));
1044
1045         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1046                 return NULL;
1047
1048         if (pmd_present(*pmd) && pmd_devmap(*pmd))
1049                 /* pass */;
1050         else
1051                 return NULL;
1052
1053         if (flags & FOLL_TOUCH)
1054                 touch_pmd(vma, addr, pmd);
1055
1056         /*
1057          * device mapped pages can only be returned if the
1058          * caller will manage the page reference count.
1059          */
1060         if (!(flags & FOLL_GET))
1061                 return ERR_PTR(-EEXIST);
1062
1063         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1064         pgmap = get_dev_pagemap(pfn, NULL);
1065         if (!pgmap)
1066                 return ERR_PTR(-EFAULT);
1067         page = pfn_to_page(pfn);
1068         get_page(page);
1069         put_dev_pagemap(pgmap);
1070
1071         return page;
1072 }
1073
1074 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1075                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1076                   struct vm_area_struct *vma)
1077 {
1078         spinlock_t *dst_ptl, *src_ptl;
1079         struct page *src_page;
1080         pmd_t pmd;
1081         pgtable_t pgtable = NULL;
1082         int ret;
1083
1084         if (!vma_is_dax(vma)) {
1085                 ret = -ENOMEM;
1086                 pgtable = pte_alloc_one(dst_mm, addr);
1087                 if (unlikely(!pgtable))
1088                         goto out;
1089         }
1090
1091         dst_ptl = pmd_lock(dst_mm, dst_pmd);
1092         src_ptl = pmd_lockptr(src_mm, src_pmd);
1093         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1094
1095         ret = -EAGAIN;
1096         pmd = *src_pmd;
1097         if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
1098                 pte_free(dst_mm, pgtable);
1099                 goto out_unlock;
1100         }
1101         /*
1102          * When page table lock is held, the huge zero pmd should not be
1103          * under splitting since we don't split the page itself, only pmd to
1104          * a page table.
1105          */
1106         if (is_huge_zero_pmd(pmd)) {
1107                 struct page *zero_page;
1108                 /*
1109                  * get_huge_zero_page() will never allocate a new page here,
1110                  * since we already have a zero page to copy. It just takes a
1111                  * reference.
1112                  */
1113                 zero_page = get_huge_zero_page();
1114                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1115                                 zero_page);
1116                 ret = 0;
1117                 goto out_unlock;
1118         }
1119
1120         if (!vma_is_dax(vma)) {
1121                 /* thp accounting separate from pmd_devmap accounting */
1122                 src_page = pmd_page(pmd);
1123                 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1124                 get_page(src_page);
1125                 page_dup_rmap(src_page, true);
1126                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1127                 atomic_long_inc(&dst_mm->nr_ptes);
1128                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1129         }
1130
1131         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1132         pmd = pmd_mkold(pmd_wrprotect(pmd));
1133         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1134
1135         ret = 0;
1136 out_unlock:
1137         spin_unlock(src_ptl);
1138         spin_unlock(dst_ptl);
1139 out:
1140         return ret;
1141 }
1142
1143 void huge_pmd_set_accessed(struct mm_struct *mm,
1144                            struct vm_area_struct *vma,
1145                            unsigned long address,
1146                            pmd_t *pmd, pmd_t orig_pmd,
1147                            int dirty)
1148 {
1149         spinlock_t *ptl;
1150         pmd_t entry;
1151         unsigned long haddr;
1152
1153         ptl = pmd_lock(mm, pmd);
1154         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1155                 goto unlock;
1156
1157         entry = pmd_mkyoung(orig_pmd);
1158         haddr = address & HPAGE_PMD_MASK;
1159         if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1160                 update_mmu_cache_pmd(vma, address, pmd);
1161
1162 unlock:
1163         spin_unlock(ptl);
1164 }
1165
1166 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1167                                         struct vm_area_struct *vma,
1168                                         unsigned long address,
1169                                         pmd_t *pmd, pmd_t orig_pmd,
1170                                         struct page *page,
1171                                         unsigned long haddr)
1172 {
1173         struct mem_cgroup *memcg;
1174         spinlock_t *ptl;
1175         pgtable_t pgtable;
1176         pmd_t _pmd;
1177         int ret = 0, i;
1178         struct page **pages;
1179         unsigned long mmun_start;       /* For mmu_notifiers */
1180         unsigned long mmun_end;         /* For mmu_notifiers */
1181
1182         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1183                         GFP_KERNEL);
1184         if (unlikely(!pages)) {
1185                 ret |= VM_FAULT_OOM;
1186                 goto out;
1187         }
1188
1189         for (i = 0; i < HPAGE_PMD_NR; i++) {
1190                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1191                                                __GFP_OTHER_NODE,
1192                                                vma, address, page_to_nid(page));
1193                 if (unlikely(!pages[i] ||
1194                              mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1195                                                    &memcg, false))) {
1196                         if (pages[i])
1197                                 put_page(pages[i]);
1198                         while (--i >= 0) {
1199                                 memcg = (void *)page_private(pages[i]);
1200                                 set_page_private(pages[i], 0);
1201                                 mem_cgroup_cancel_charge(pages[i], memcg,
1202                                                 false);
1203                                 put_page(pages[i]);
1204                         }
1205                         kfree(pages);
1206                         ret |= VM_FAULT_OOM;
1207                         goto out;
1208                 }
1209                 set_page_private(pages[i], (unsigned long)memcg);
1210         }
1211
1212         for (i = 0; i < HPAGE_PMD_NR; i++) {
1213                 copy_user_highpage(pages[i], page + i,
1214                                    haddr + PAGE_SIZE * i, vma);
1215                 __SetPageUptodate(pages[i]);
1216                 cond_resched();
1217         }
1218
1219         mmun_start = haddr;
1220         mmun_end   = haddr + HPAGE_PMD_SIZE;
1221         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1222
1223         ptl = pmd_lock(mm, pmd);
1224         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1225                 goto out_free_pages;
1226         VM_BUG_ON_PAGE(!PageHead(page), page);
1227
1228         pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1229         /* leave pmd empty until pte is filled */
1230
1231         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1232         pmd_populate(mm, &_pmd, pgtable);
1233
1234         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1235                 pte_t *pte, entry;
1236                 entry = mk_pte(pages[i], vma->vm_page_prot);
1237                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1238                 memcg = (void *)page_private(pages[i]);
1239                 set_page_private(pages[i], 0);
1240                 page_add_new_anon_rmap(pages[i], vma, haddr, false);
1241                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1242                 lru_cache_add_active_or_unevictable(pages[i], vma);
1243                 pte = pte_offset_map(&_pmd, haddr);
1244                 VM_BUG_ON(!pte_none(*pte));
1245                 set_pte_at(mm, haddr, pte, entry);
1246                 pte_unmap(pte);
1247         }
1248         kfree(pages);
1249
1250         smp_wmb(); /* make pte visible before pmd */
1251         pmd_populate(mm, pmd, pgtable);
1252         page_remove_rmap(page, true);
1253         spin_unlock(ptl);
1254
1255         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1256
1257         ret |= VM_FAULT_WRITE;
1258         put_page(page);
1259
1260 out:
1261         return ret;
1262
1263 out_free_pages:
1264         spin_unlock(ptl);
1265         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1266         for (i = 0; i < HPAGE_PMD_NR; i++) {
1267                 memcg = (void *)page_private(pages[i]);
1268                 set_page_private(pages[i], 0);
1269                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1270                 put_page(pages[i]);
1271         }
1272         kfree(pages);
1273         goto out;
1274 }
1275
1276 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1277                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1278 {
1279         spinlock_t *ptl;
1280         int ret = 0;
1281         struct page *page = NULL, *new_page;
1282         struct mem_cgroup *memcg;
1283         unsigned long haddr;
1284         unsigned long mmun_start;       /* For mmu_notifiers */
1285         unsigned long mmun_end;         /* For mmu_notifiers */
1286         gfp_t huge_gfp;                 /* for allocation and charge */
1287
1288         ptl = pmd_lockptr(mm, pmd);
1289         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1290         haddr = address & HPAGE_PMD_MASK;
1291         if (is_huge_zero_pmd(orig_pmd))
1292                 goto alloc;
1293         spin_lock(ptl);
1294         if (unlikely(!pmd_same(*pmd, orig_pmd)))
1295                 goto out_unlock;
1296
1297         page = pmd_page(orig_pmd);
1298         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1299         /*
1300          * We can only reuse the page if nobody else maps the huge page or it's
1301          * part.
1302          */
1303         if (page_trans_huge_mapcount(page, NULL) == 1) {
1304                 pmd_t entry;
1305                 entry = pmd_mkyoung(orig_pmd);
1306                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1307                 if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1308                         update_mmu_cache_pmd(vma, address, pmd);
1309                 ret |= VM_FAULT_WRITE;
1310                 goto out_unlock;
1311         }
1312         get_page(page);
1313         spin_unlock(ptl);
1314 alloc:
1315         if (transparent_hugepage_enabled(vma) &&
1316             !transparent_hugepage_debug_cow()) {
1317                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1318                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1319         } else
1320                 new_page = NULL;
1321
1322         if (likely(new_page)) {
1323                 prep_transhuge_page(new_page);
1324         } else {
1325                 if (!page) {
1326                         split_huge_pmd(vma, pmd, address);
1327                         ret |= VM_FAULT_FALLBACK;
1328                 } else {
1329                         ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1330                                         pmd, orig_pmd, page, haddr);
1331                         if (ret & VM_FAULT_OOM) {
1332                                 split_huge_pmd(vma, pmd, address);
1333                                 ret |= VM_FAULT_FALLBACK;
1334                         }
1335                         put_page(page);
1336                 }
1337                 count_vm_event(THP_FAULT_FALLBACK);
1338                 goto out;
1339         }
1340
1341         if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg,
1342                                            true))) {
1343                 put_page(new_page);
1344                 if (page) {
1345                         split_huge_pmd(vma, pmd, address);
1346                         put_page(page);
1347                 } else
1348                         split_huge_pmd(vma, pmd, address);
1349                 ret |= VM_FAULT_FALLBACK;
1350                 count_vm_event(THP_FAULT_FALLBACK);
1351                 goto out;
1352         }
1353
1354         count_vm_event(THP_FAULT_ALLOC);
1355
1356         if (!page)
1357                 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1358         else
1359                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1360         __SetPageUptodate(new_page);
1361
1362         mmun_start = haddr;
1363         mmun_end   = haddr + HPAGE_PMD_SIZE;
1364         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1365
1366         spin_lock(ptl);
1367         if (page)
1368                 put_page(page);
1369         if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1370                 spin_unlock(ptl);
1371                 mem_cgroup_cancel_charge(new_page, memcg, true);
1372                 put_page(new_page);
1373                 goto out_mn;
1374         } else {
1375                 pmd_t entry;
1376                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1377                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1378                 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1379                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1380                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1381                 lru_cache_add_active_or_unevictable(new_page, vma);
1382                 set_pmd_at(mm, haddr, pmd, entry);
1383                 update_mmu_cache_pmd(vma, address, pmd);
1384                 if (!page) {
1385                         add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1386                         put_huge_zero_page();
1387                 } else {
1388                         VM_BUG_ON_PAGE(!PageHead(page), page);
1389                         page_remove_rmap(page, true);
1390                         put_page(page);
1391                 }
1392                 ret |= VM_FAULT_WRITE;
1393         }
1394         spin_unlock(ptl);
1395 out_mn:
1396         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1397 out:
1398         return ret;
1399 out_unlock:
1400         spin_unlock(ptl);
1401         return ret;
1402 }
1403
1404 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1405                                    unsigned long addr,
1406                                    pmd_t *pmd,
1407                                    unsigned int flags)
1408 {
1409         struct mm_struct *mm = vma->vm_mm;
1410         struct page *page = NULL;
1411
1412         assert_spin_locked(pmd_lockptr(mm, pmd));
1413
1414         if (flags & FOLL_WRITE && !pmd_write(*pmd))
1415                 goto out;
1416
1417         /* Avoid dumping huge zero page */
1418         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1419                 return ERR_PTR(-EFAULT);
1420
1421         /* Full NUMA hinting faults to serialise migration in fault paths */
1422         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1423                 goto out;
1424
1425         page = pmd_page(*pmd);
1426         VM_BUG_ON_PAGE(!PageHead(page), page);
1427         if (flags & FOLL_TOUCH)
1428                 touch_pmd(vma, addr, pmd);
1429         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1430                 /*
1431                  * We don't mlock() pte-mapped THPs. This way we can avoid
1432                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1433                  *
1434                  * In most cases the pmd is the only mapping of the page as we
1435                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1436                  * writable private mappings in populate_vma_page_range().
1437                  *
1438                  * The only scenario when we have the page shared here is if we
1439                  * mlocking read-only mapping shared over fork(). We skip
1440                  * mlocking such pages.
1441                  */
1442                 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) &&
1443                                 page->mapping && trylock_page(page)) {
1444                         lru_add_drain();
1445                         if (page->mapping)
1446                                 mlock_vma_page(page);
1447                         unlock_page(page);
1448                 }
1449         }
1450         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1451         VM_BUG_ON_PAGE(!PageCompound(page), page);
1452         if (flags & FOLL_GET)
1453                 get_page(page);
1454
1455 out:
1456         return page;
1457 }
1458
1459 /* NUMA hinting page fault entry point for trans huge pmds */
1460 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1461                                 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1462 {
1463         spinlock_t *ptl;
1464         struct anon_vma *anon_vma = NULL;
1465         struct page *page;
1466         unsigned long haddr = addr & HPAGE_PMD_MASK;
1467         int page_nid = -1, this_nid = numa_node_id();
1468         int target_nid, last_cpupid = -1;
1469         bool page_locked;
1470         bool migrated = false;
1471         bool was_writable;
1472         int flags = 0;
1473
1474         /* A PROT_NONE fault should not end up here */
1475         BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1476
1477         ptl = pmd_lock(mm, pmdp);
1478         if (unlikely(!pmd_same(pmd, *pmdp)))
1479                 goto out_unlock;
1480
1481         /*
1482          * If there are potential migrations, wait for completion and retry
1483          * without disrupting NUMA hinting information. Do not relock and
1484          * check_same as the page may no longer be mapped.
1485          */
1486         if (unlikely(pmd_trans_migrating(*pmdp))) {
1487                 page = pmd_page(*pmdp);
1488                 spin_unlock(ptl);
1489                 wait_on_page_locked(page);
1490                 goto out;
1491         }
1492
1493         page = pmd_page(pmd);
1494         BUG_ON(is_huge_zero_page(page));
1495         page_nid = page_to_nid(page);
1496         last_cpupid = page_cpupid_last(page);
1497         count_vm_numa_event(NUMA_HINT_FAULTS);
1498         if (page_nid == this_nid) {
1499                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1500                 flags |= TNF_FAULT_LOCAL;
1501         }
1502
1503         /* See similar comment in do_numa_page for explanation */
1504         if (!(vma->vm_flags & VM_WRITE))
1505                 flags |= TNF_NO_GROUP;
1506
1507         /*
1508          * Acquire the page lock to serialise THP migrations but avoid dropping
1509          * page_table_lock if at all possible
1510          */
1511         page_locked = trylock_page(page);
1512         target_nid = mpol_misplaced(page, vma, haddr);
1513         if (target_nid == -1) {
1514                 /* If the page was locked, there are no parallel migrations */
1515                 if (page_locked)
1516                         goto clear_pmdnuma;
1517         }
1518
1519         /* Migration could have started since the pmd_trans_migrating check */
1520         if (!page_locked) {
1521                 spin_unlock(ptl);
1522                 wait_on_page_locked(page);
1523                 page_nid = -1;
1524                 goto out;
1525         }
1526
1527         /*
1528          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1529          * to serialises splits
1530          */
1531         get_page(page);
1532         spin_unlock(ptl);
1533         anon_vma = page_lock_anon_vma_read(page);
1534
1535         /* Confirm the PMD did not change while page_table_lock was released */
1536         spin_lock(ptl);
1537         if (unlikely(!pmd_same(pmd, *pmdp))) {
1538                 unlock_page(page);
1539                 put_page(page);
1540                 page_nid = -1;
1541                 goto out_unlock;
1542         }
1543
1544         /* Bail if we fail to protect against THP splits for any reason */
1545         if (unlikely(!anon_vma)) {
1546                 put_page(page);
1547                 page_nid = -1;
1548                 goto clear_pmdnuma;
1549         }
1550
1551         /*
1552          * Migrate the THP to the requested node, returns with page unlocked
1553          * and access rights restored.
1554          */
1555         spin_unlock(ptl);
1556         migrated = migrate_misplaced_transhuge_page(mm, vma,
1557                                 pmdp, pmd, addr, page, target_nid);
1558         if (migrated) {
1559                 flags |= TNF_MIGRATED;
1560                 page_nid = target_nid;
1561         } else
1562                 flags |= TNF_MIGRATE_FAIL;
1563
1564         goto out;
1565 clear_pmdnuma:
1566         BUG_ON(!PageLocked(page));
1567         was_writable = pmd_write(pmd);
1568         pmd = pmd_modify(pmd, vma->vm_page_prot);
1569         pmd = pmd_mkyoung(pmd);
1570         if (was_writable)
1571                 pmd = pmd_mkwrite(pmd);
1572         set_pmd_at(mm, haddr, pmdp, pmd);
1573         update_mmu_cache_pmd(vma, addr, pmdp);
1574         unlock_page(page);
1575 out_unlock:
1576         spin_unlock(ptl);
1577
1578 out:
1579         if (anon_vma)
1580                 page_unlock_anon_vma_read(anon_vma);
1581
1582         if (page_nid != -1)
1583                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1584
1585         return 0;
1586 }
1587
1588 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1589                 pmd_t *pmd, unsigned long addr, unsigned long next)
1590
1591 {
1592         spinlock_t *ptl;
1593         pmd_t orig_pmd;
1594         struct page *page;
1595         struct mm_struct *mm = tlb->mm;
1596         int ret = 0;
1597
1598         ptl = pmd_trans_huge_lock(pmd, vma);
1599         if (!ptl)
1600                 goto out_unlocked;
1601
1602         orig_pmd = *pmd;
1603         if (is_huge_zero_pmd(orig_pmd)) {
1604                 ret = 1;
1605                 goto out;
1606         }
1607
1608         page = pmd_page(orig_pmd);
1609         /*
1610          * If other processes are mapping this page, we couldn't discard
1611          * the page unless they all do MADV_FREE so let's skip the page.
1612          */
1613         if (page_mapcount(page) != 1)
1614                 goto out;
1615
1616         if (!trylock_page(page))
1617                 goto out;
1618
1619         /*
1620          * If user want to discard part-pages of THP, split it so MADV_FREE
1621          * will deactivate only them.
1622          */
1623         if (next - addr != HPAGE_PMD_SIZE) {
1624                 get_page(page);
1625                 spin_unlock(ptl);
1626                 if (split_huge_page(page)) {
1627                         put_page(page);
1628                         unlock_page(page);
1629                         goto out_unlocked;
1630                 }
1631                 put_page(page);
1632                 unlock_page(page);
1633                 ret = 1;
1634                 goto out_unlocked;
1635         }
1636
1637         if (PageDirty(page))
1638                 ClearPageDirty(page);
1639         unlock_page(page);
1640
1641         if (PageActive(page))
1642                 deactivate_page(page);
1643
1644         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1645                 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1646                         tlb->fullmm);
1647                 orig_pmd = pmd_mkold(orig_pmd);
1648                 orig_pmd = pmd_mkclean(orig_pmd);
1649
1650                 set_pmd_at(mm, addr, pmd, orig_pmd);
1651                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1652         }
1653         ret = 1;
1654 out:
1655         spin_unlock(ptl);
1656 out_unlocked:
1657         return ret;
1658 }
1659
1660 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1661                  pmd_t *pmd, unsigned long addr)
1662 {
1663         pmd_t orig_pmd;
1664         spinlock_t *ptl;
1665
1666         ptl = __pmd_trans_huge_lock(pmd, vma);
1667         if (!ptl)
1668                 return 0;
1669         /*
1670          * For architectures like ppc64 we look at deposited pgtable
1671          * when calling pmdp_huge_get_and_clear. So do the
1672          * pgtable_trans_huge_withdraw after finishing pmdp related
1673          * operations.
1674          */
1675         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1676                         tlb->fullmm);
1677         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1678         if (vma_is_dax(vma)) {
1679                 spin_unlock(ptl);
1680                 if (is_huge_zero_pmd(orig_pmd))
1681                         tlb_remove_page(tlb, pmd_page(orig_pmd));
1682         } else if (is_huge_zero_pmd(orig_pmd)) {
1683                 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1684                 atomic_long_dec(&tlb->mm->nr_ptes);
1685                 spin_unlock(ptl);
1686                 tlb_remove_page(tlb, pmd_page(orig_pmd));
1687         } else {
1688                 struct page *page = pmd_page(orig_pmd);
1689                 page_remove_rmap(page, true);
1690                 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1691                 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1692                 VM_BUG_ON_PAGE(!PageHead(page), page);
1693                 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1694                 atomic_long_dec(&tlb->mm->nr_ptes);
1695                 spin_unlock(ptl);
1696                 tlb_remove_page(tlb, page);
1697         }
1698         return 1;
1699 }
1700
1701 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1702                   unsigned long new_addr, unsigned long old_end,
1703                   pmd_t *old_pmd, pmd_t *new_pmd)
1704 {
1705         spinlock_t *old_ptl, *new_ptl;
1706         pmd_t pmd;
1707         struct mm_struct *mm = vma->vm_mm;
1708
1709         if ((old_addr & ~HPAGE_PMD_MASK) ||
1710             (new_addr & ~HPAGE_PMD_MASK) ||
1711             old_end - old_addr < HPAGE_PMD_SIZE)
1712                 return false;
1713
1714         /*
1715          * The destination pmd shouldn't be established, free_pgtables()
1716          * should have release it.
1717          */
1718         if (WARN_ON(!pmd_none(*new_pmd))) {
1719                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1720                 return false;
1721         }
1722
1723         /*
1724          * We don't have to worry about the ordering of src and dst
1725          * ptlocks because exclusive mmap_sem prevents deadlock.
1726          */
1727         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1728         if (old_ptl) {
1729                 new_ptl = pmd_lockptr(mm, new_pmd);
1730                 if (new_ptl != old_ptl)
1731                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1732                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1733                 VM_BUG_ON(!pmd_none(*new_pmd));
1734
1735                 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1736                                 vma_is_anonymous(vma)) {
1737                         pgtable_t pgtable;
1738                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1739                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1740                 }
1741                 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1742                 if (new_ptl != old_ptl)
1743                         spin_unlock(new_ptl);
1744                 spin_unlock(old_ptl);
1745                 return true;
1746         }
1747         return false;
1748 }
1749
1750 /*
1751  * Returns
1752  *  - 0 if PMD could not be locked
1753  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1754  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1755  */
1756 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1757                 unsigned long addr, pgprot_t newprot, int prot_numa)
1758 {
1759         struct mm_struct *mm = vma->vm_mm;
1760         spinlock_t *ptl;
1761         int ret = 0;
1762
1763         ptl = __pmd_trans_huge_lock(pmd, vma);
1764         if (ptl) {
1765                 pmd_t entry;
1766                 bool preserve_write = prot_numa && pmd_write(*pmd);
1767                 ret = 1;
1768
1769                 /*
1770                  * Avoid trapping faults against the zero page. The read-only
1771                  * data is likely to be read-cached on the local CPU and
1772                  * local/remote hits to the zero page are not interesting.
1773                  */
1774                 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1775                         spin_unlock(ptl);
1776                         return ret;
1777                 }
1778
1779                 if (!prot_numa || !pmd_protnone(*pmd)) {
1780                         entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1781                         entry = pmd_modify(entry, newprot);
1782                         if (preserve_write)
1783                                 entry = pmd_mkwrite(entry);
1784                         ret = HPAGE_PMD_NR;
1785                         set_pmd_at(mm, addr, pmd, entry);
1786                         BUG_ON(!preserve_write && pmd_write(entry));
1787                 }
1788                 spin_unlock(ptl);
1789         }
1790
1791         return ret;
1792 }
1793
1794 /*
1795  * Returns true if a given pmd maps a thp, false otherwise.
1796  *
1797  * Note that if it returns true, this routine returns without unlocking page
1798  * table lock. So callers must unlock it.
1799  */
1800 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1801 {
1802         spinlock_t *ptl;
1803         ptl = pmd_lock(vma->vm_mm, pmd);
1804         if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1805                 return ptl;
1806         spin_unlock(ptl);
1807         return NULL;
1808 }
1809
1810 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1811
1812 int hugepage_madvise(struct vm_area_struct *vma,
1813                      unsigned long *vm_flags, int advice)
1814 {
1815         switch (advice) {
1816         case MADV_HUGEPAGE:
1817 #ifdef CONFIG_S390
1818                 /*
1819                  * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1820                  * can't handle this properly after s390_enable_sie, so we simply
1821                  * ignore the madvise to prevent qemu from causing a SIGSEGV.
1822                  */
1823                 if (mm_has_pgste(vma->vm_mm))
1824                         return 0;
1825 #endif
1826                 /*
1827                  * Be somewhat over-protective like KSM for now!
1828                  */
1829                 if (*vm_flags & VM_NO_THP)
1830                         return -EINVAL;
1831                 *vm_flags &= ~VM_NOHUGEPAGE;
1832                 *vm_flags |= VM_HUGEPAGE;
1833                 /*
1834                  * If the vma become good for khugepaged to scan,
1835                  * register it here without waiting a page fault that
1836                  * may not happen any time soon.
1837                  */
1838                 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1839                         return -ENOMEM;
1840                 break;
1841         case MADV_NOHUGEPAGE:
1842                 /*
1843                  * Be somewhat over-protective like KSM for now!
1844                  */
1845                 if (*vm_flags & VM_NO_THP)
1846                         return -EINVAL;
1847                 *vm_flags &= ~VM_HUGEPAGE;
1848                 *vm_flags |= VM_NOHUGEPAGE;
1849                 /*
1850                  * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1851                  * this vma even if we leave the mm registered in khugepaged if
1852                  * it got registered before VM_NOHUGEPAGE was set.
1853                  */
1854                 break;
1855         }
1856
1857         return 0;
1858 }
1859
1860 static int __init khugepaged_slab_init(void)
1861 {
1862         mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1863                                           sizeof(struct mm_slot),
1864                                           __alignof__(struct mm_slot), 0, NULL);
1865         if (!mm_slot_cache)
1866                 return -ENOMEM;
1867
1868         return 0;
1869 }
1870
1871 static void __init khugepaged_slab_exit(void)
1872 {
1873         kmem_cache_destroy(mm_slot_cache);
1874 }
1875
1876 static inline struct mm_slot *alloc_mm_slot(void)
1877 {
1878         if (!mm_slot_cache)     /* initialization failed */
1879                 return NULL;
1880         return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1881 }
1882
1883 static inline void free_mm_slot(struct mm_slot *mm_slot)
1884 {
1885         kmem_cache_free(mm_slot_cache, mm_slot);
1886 }
1887
1888 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1889 {
1890         struct mm_slot *mm_slot;
1891
1892         hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1893                 if (mm == mm_slot->mm)
1894                         return mm_slot;
1895
1896         return NULL;
1897 }
1898
1899 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1900                                     struct mm_slot *mm_slot)
1901 {
1902         mm_slot->mm = mm;
1903         hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1904 }
1905
1906 static inline int khugepaged_test_exit(struct mm_struct *mm)
1907 {
1908         return atomic_read(&mm->mm_users) == 0;
1909 }
1910
1911 int __khugepaged_enter(struct mm_struct *mm)
1912 {
1913         struct mm_slot *mm_slot;
1914         int wakeup;
1915
1916         mm_slot = alloc_mm_slot();
1917         if (!mm_slot)
1918                 return -ENOMEM;
1919
1920         /* __khugepaged_exit() must not run from under us */
1921         VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1922         if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1923                 free_mm_slot(mm_slot);
1924                 return 0;
1925         }
1926
1927         spin_lock(&khugepaged_mm_lock);
1928         insert_to_mm_slots_hash(mm, mm_slot);
1929         /*
1930          * Insert just behind the scanning cursor, to let the area settle
1931          * down a little.
1932          */
1933         wakeup = list_empty(&khugepaged_scan.mm_head);
1934         list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1935         spin_unlock(&khugepaged_mm_lock);
1936
1937         atomic_inc(&mm->mm_count);
1938         if (wakeup)
1939                 wake_up_interruptible(&khugepaged_wait);
1940
1941         return 0;
1942 }
1943
1944 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1945                                unsigned long vm_flags)
1946 {
1947         unsigned long hstart, hend;
1948         if (!vma->anon_vma)
1949                 /*
1950                  * Not yet faulted in so we will register later in the
1951                  * page fault if needed.
1952                  */
1953                 return 0;
1954         if (vma->vm_ops || (vm_flags & VM_NO_THP))
1955                 /* khugepaged not yet working on file or special mappings */
1956                 return 0;
1957         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1958         hend = vma->vm_end & HPAGE_PMD_MASK;
1959         if (hstart < hend)
1960                 return khugepaged_enter(vma, vm_flags);
1961         return 0;
1962 }
1963
1964 void __khugepaged_exit(struct mm_struct *mm)
1965 {
1966         struct mm_slot *mm_slot;
1967         int free = 0;
1968
1969         spin_lock(&khugepaged_mm_lock);
1970         mm_slot = get_mm_slot(mm);
1971         if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1972                 hash_del(&mm_slot->hash);
1973                 list_del(&mm_slot->mm_node);
1974                 free = 1;
1975         }
1976         spin_unlock(&khugepaged_mm_lock);
1977
1978         if (free) {
1979                 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1980                 free_mm_slot(mm_slot);
1981                 mmdrop(mm);
1982         } else if (mm_slot) {
1983                 /*
1984                  * This is required to serialize against
1985                  * khugepaged_test_exit() (which is guaranteed to run
1986                  * under mmap sem read mode). Stop here (after we
1987                  * return all pagetables will be destroyed) until
1988                  * khugepaged has finished working on the pagetables
1989                  * under the mmap_sem.
1990                  */
1991                 down_write(&mm->mmap_sem);
1992                 up_write(&mm->mmap_sem);
1993         }
1994 }
1995
1996 static void release_pte_page(struct page *page)
1997 {
1998         /* 0 stands for page_is_file_cache(page) == false */
1999         dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2000         unlock_page(page);
2001         putback_lru_page(page);
2002 }
2003
2004 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2005 {
2006         while (--_pte >= pte) {
2007                 pte_t pteval = *_pte;
2008                 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
2009                         release_pte_page(pte_page(pteval));
2010         }
2011 }
2012
2013 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2014                                         unsigned long address,
2015                                         pte_t *pte)
2016 {
2017         struct page *page = NULL;
2018         pte_t *_pte;
2019         int none_or_zero = 0, result = 0;
2020         bool referenced = false, writable = false;
2021
2022         for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2023              _pte++, address += PAGE_SIZE) {
2024                 pte_t pteval = *_pte;
2025                 if (pte_none(pteval) || (pte_present(pteval) &&
2026                                 is_zero_pfn(pte_pfn(pteval)))) {
2027                         if (!userfaultfd_armed(vma) &&
2028                             ++none_or_zero <= khugepaged_max_ptes_none) {
2029                                 continue;
2030                         } else {
2031                                 result = SCAN_EXCEED_NONE_PTE;
2032                                 goto out;
2033                         }
2034                 }
2035                 if (!pte_present(pteval)) {
2036                         result = SCAN_PTE_NON_PRESENT;
2037                         goto out;
2038                 }
2039                 page = vm_normal_page(vma, address, pteval);
2040                 if (unlikely(!page)) {
2041                         result = SCAN_PAGE_NULL;
2042                         goto out;
2043                 }
2044
2045                 VM_BUG_ON_PAGE(PageCompound(page), page);
2046                 VM_BUG_ON_PAGE(!PageAnon(page), page);
2047                 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2048
2049                 /*
2050                  * We can do it before isolate_lru_page because the
2051                  * page can't be freed from under us. NOTE: PG_lock
2052                  * is needed to serialize against split_huge_page
2053                  * when invoked from the VM.
2054                  */
2055                 if (!trylock_page(page)) {
2056                         result = SCAN_PAGE_LOCK;
2057                         goto out;
2058                 }
2059
2060                 /*
2061                  * cannot use mapcount: can't collapse if there's a gup pin.
2062                  * The page must only be referenced by the scanned process
2063                  * and page swap cache.
2064                  */
2065                 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2066                         unlock_page(page);
2067                         result = SCAN_PAGE_COUNT;
2068                         goto out;
2069                 }
2070                 if (pte_write(pteval)) {
2071                         writable = true;
2072                 } else {
2073                         if (PageSwapCache(page) &&
2074                             !reuse_swap_page(page, NULL)) {
2075                                 unlock_page(page);
2076                                 result = SCAN_SWAP_CACHE_PAGE;
2077                                 goto out;
2078                         }
2079                         /*
2080                          * Page is not in the swap cache. It can be collapsed
2081                          * into a THP.
2082                          */
2083                 }
2084
2085                 /*
2086                  * Isolate the page to avoid collapsing an hugepage
2087                  * currently in use by the VM.
2088                  */
2089                 if (isolate_lru_page(page)) {
2090                         unlock_page(page);
2091                         result = SCAN_DEL_PAGE_LRU;
2092                         goto out;
2093                 }
2094                 /* 0 stands for page_is_file_cache(page) == false */
2095                 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2096                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2097                 VM_BUG_ON_PAGE(PageLRU(page), page);
2098
2099                 /* If there is no mapped pte young don't collapse the page */
2100                 if (pte_young(pteval) ||
2101                     page_is_young(page) || PageReferenced(page) ||
2102                     mmu_notifier_test_young(vma->vm_mm, address))
2103                         referenced = true;
2104         }
2105         if (likely(writable)) {
2106                 if (likely(referenced)) {
2107                         result = SCAN_SUCCEED;
2108                         trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2109                                                             referenced, writable, result);
2110                         return 1;
2111                 }
2112         } else {
2113                 result = SCAN_PAGE_RO;
2114         }
2115
2116 out:
2117         release_pte_pages(pte, _pte);
2118         trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2119                                             referenced, writable, result);
2120         return 0;
2121 }
2122
2123 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2124                                       struct vm_area_struct *vma,
2125                                       unsigned long address,
2126                                       spinlock_t *ptl)
2127 {
2128         pte_t *_pte;
2129         for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2130                 pte_t pteval = *_pte;
2131                 struct page *src_page;
2132
2133                 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2134                         clear_user_highpage(page, address);
2135                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2136                         if (is_zero_pfn(pte_pfn(pteval))) {
2137                                 /*
2138                                  * ptl mostly unnecessary.
2139                                  */
2140                                 spin_lock(ptl);
2141                                 /*
2142                                  * paravirt calls inside pte_clear here are
2143                                  * superfluous.
2144                                  */
2145                                 pte_clear(vma->vm_mm, address, _pte);
2146                                 spin_unlock(ptl);
2147                         }
2148                 } else {
2149                         src_page = pte_page(pteval);
2150                         copy_user_highpage(page, src_page, address, vma);
2151                         VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2152                         release_pte_page(src_page);
2153                         /*
2154                          * ptl mostly unnecessary, but preempt has to
2155                          * be disabled to update the per-cpu stats
2156                          * inside page_remove_rmap().
2157                          */
2158                         spin_lock(ptl);
2159                         /*
2160                          * paravirt calls inside pte_clear here are
2161                          * superfluous.
2162                          */
2163                         pte_clear(vma->vm_mm, address, _pte);
2164                         page_remove_rmap(src_page, false);
2165                         spin_unlock(ptl);
2166                         free_page_and_swap_cache(src_page);
2167                 }
2168
2169                 address += PAGE_SIZE;
2170                 page++;
2171         }
2172 }
2173
2174 static void khugepaged_alloc_sleep(void)
2175 {
2176         DEFINE_WAIT(wait);
2177
2178         add_wait_queue(&khugepaged_wait, &wait);
2179         freezable_schedule_timeout_interruptible(
2180                 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2181         remove_wait_queue(&khugepaged_wait, &wait);
2182 }
2183
2184 static int khugepaged_node_load[MAX_NUMNODES];
2185
2186 static bool khugepaged_scan_abort(int nid)
2187 {
2188         int i;
2189
2190         /*
2191          * If zone_reclaim_mode is disabled, then no extra effort is made to
2192          * allocate memory locally.
2193          */
2194         if (!zone_reclaim_mode)
2195                 return false;
2196
2197         /* If there is a count for this node already, it must be acceptable */
2198         if (khugepaged_node_load[nid])
2199                 return false;
2200
2201         for (i = 0; i < MAX_NUMNODES; i++) {
2202                 if (!khugepaged_node_load[i])
2203                         continue;
2204                 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2205                         return true;
2206         }
2207         return false;
2208 }
2209
2210 #ifdef CONFIG_NUMA
2211 static int khugepaged_find_target_node(void)
2212 {
2213         static int last_khugepaged_target_node = NUMA_NO_NODE;
2214         int nid, target_node = 0, max_value = 0;
2215
2216         /* find first node with max normal pages hit */
2217         for (nid = 0; nid < MAX_NUMNODES; nid++)
2218                 if (khugepaged_node_load[nid] > max_value) {
2219                         max_value = khugepaged_node_load[nid];
2220                         target_node = nid;
2221                 }
2222
2223         /* do some balance if several nodes have the same hit record */
2224         if (target_node <= last_khugepaged_target_node)
2225                 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2226                                 nid++)
2227                         if (max_value == khugepaged_node_load[nid]) {
2228                                 target_node = nid;
2229                                 break;
2230                         }
2231
2232         last_khugepaged_target_node = target_node;
2233         return target_node;
2234 }
2235
2236 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2237 {
2238         if (IS_ERR(*hpage)) {
2239                 if (!*wait)
2240                         return false;
2241
2242                 *wait = false;
2243                 *hpage = NULL;
2244                 khugepaged_alloc_sleep();
2245         } else if (*hpage) {
2246                 put_page(*hpage);
2247                 *hpage = NULL;
2248         }
2249
2250         return true;
2251 }
2252
2253 static struct page *
2254 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2255                        unsigned long address, int node)
2256 {
2257         VM_BUG_ON_PAGE(*hpage, *hpage);
2258
2259         /*
2260          * Before allocating the hugepage, release the mmap_sem read lock.
2261          * The allocation can take potentially a long time if it involves
2262          * sync compaction, and we do not need to hold the mmap_sem during
2263          * that. We will recheck the vma after taking it again in write mode.
2264          */
2265         up_read(&mm->mmap_sem);
2266
2267         *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2268         if (unlikely(!*hpage)) {
2269                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2270                 *hpage = ERR_PTR(-ENOMEM);
2271                 return NULL;
2272         }
2273
2274         prep_transhuge_page(*hpage);
2275         count_vm_event(THP_COLLAPSE_ALLOC);
2276         return *hpage;
2277 }
2278 #else
2279 static int khugepaged_find_target_node(void)
2280 {
2281         return 0;
2282 }
2283
2284 static inline struct page *alloc_khugepaged_hugepage(void)
2285 {
2286         struct page *page;
2287
2288         page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
2289                            HPAGE_PMD_ORDER);
2290         if (page)
2291                 prep_transhuge_page(page);
2292         return page;
2293 }
2294
2295 static struct page *khugepaged_alloc_hugepage(bool *wait)
2296 {
2297         struct page *hpage;
2298
2299         do {
2300                 hpage = alloc_khugepaged_hugepage();
2301                 if (!hpage) {
2302                         count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2303                         if (!*wait)
2304                                 return NULL;
2305
2306                         *wait = false;
2307                         khugepaged_alloc_sleep();
2308                 } else
2309                         count_vm_event(THP_COLLAPSE_ALLOC);
2310         } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2311
2312         return hpage;
2313 }
2314
2315 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2316 {
2317         if (!*hpage)
2318                 *hpage = khugepaged_alloc_hugepage(wait);
2319
2320         if (unlikely(!*hpage))
2321                 return false;
2322
2323         return true;
2324 }
2325
2326 static struct page *
2327 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2328                        unsigned long address, int node)
2329 {
2330         up_read(&mm->mmap_sem);
2331         VM_BUG_ON(!*hpage);
2332
2333         return  *hpage;
2334 }
2335 #endif
2336
2337 static bool hugepage_vma_check(struct vm_area_struct *vma)
2338 {
2339         if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2340             (vma->vm_flags & VM_NOHUGEPAGE))
2341                 return false;
2342         if (!vma->anon_vma || vma->vm_ops)
2343                 return false;
2344         if (is_vma_temporary_stack(vma))
2345                 return false;
2346         return !(vma->vm_flags & VM_NO_THP);
2347 }
2348
2349 static void collapse_huge_page(struct mm_struct *mm,
2350                                    unsigned long address,
2351                                    struct page **hpage,
2352                                    struct vm_area_struct *vma,
2353                                    int node)
2354 {
2355         pmd_t *pmd, _pmd;
2356         pte_t *pte;
2357         pgtable_t pgtable;
2358         struct page *new_page;
2359         spinlock_t *pmd_ptl, *pte_ptl;
2360         int isolated = 0, result = 0;
2361         unsigned long hstart, hend;
2362         struct mem_cgroup *memcg;
2363         unsigned long mmun_start;       /* For mmu_notifiers */
2364         unsigned long mmun_end;         /* For mmu_notifiers */
2365         gfp_t gfp;
2366
2367         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2368
2369         /* Only allocate from the target node */
2370         gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
2371
2372         /* release the mmap_sem read lock. */
2373         new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2374         if (!new_page) {
2375                 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2376                 goto out_nolock;
2377         }
2378
2379         if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2380                 result = SCAN_CGROUP_CHARGE_FAIL;
2381                 goto out_nolock;
2382         }
2383
2384         /*
2385          * Prevent all access to pagetables with the exception of
2386          * gup_fast later hanlded by the ptep_clear_flush and the VM
2387          * handled by the anon_vma lock + PG_lock.
2388          */
2389         down_write(&mm->mmap_sem);
2390         if (unlikely(khugepaged_test_exit(mm))) {
2391                 result = SCAN_ANY_PROCESS;
2392                 goto out;
2393         }
2394
2395         vma = find_vma(mm, address);
2396         if (!vma) {
2397                 result = SCAN_VMA_NULL;
2398                 goto out;
2399         }
2400         hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2401         hend = vma->vm_end & HPAGE_PMD_MASK;
2402         if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
2403                 result = SCAN_ADDRESS_RANGE;
2404                 goto out;
2405         }
2406         if (!hugepage_vma_check(vma)) {
2407                 result = SCAN_VMA_CHECK;
2408                 goto out;
2409         }
2410         pmd = mm_find_pmd(mm, address);
2411         if (!pmd) {
2412                 result = SCAN_PMD_NULL;
2413                 goto out;
2414         }
2415
2416         anon_vma_lock_write(vma->anon_vma);
2417
2418         pte = pte_offset_map(pmd, address);
2419         pte_ptl = pte_lockptr(mm, pmd);
2420
2421         mmun_start = address;
2422         mmun_end   = address + HPAGE_PMD_SIZE;
2423         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2424         pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2425         /*
2426          * After this gup_fast can't run anymore. This also removes
2427          * any huge TLB entry from the CPU so we won't allow
2428          * huge and small TLB entries for the same virtual address
2429          * to avoid the risk of CPU bugs in that area.
2430          */
2431         _pmd = pmdp_collapse_flush(vma, address, pmd);
2432         spin_unlock(pmd_ptl);
2433         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2434
2435         spin_lock(pte_ptl);
2436         isolated = __collapse_huge_page_isolate(vma, address, pte);
2437         spin_unlock(pte_ptl);
2438
2439         if (unlikely(!isolated)) {
2440                 pte_unmap(pte);
2441                 spin_lock(pmd_ptl);
2442                 BUG_ON(!pmd_none(*pmd));
2443                 /*
2444                  * We can only use set_pmd_at when establishing
2445                  * hugepmds and never for establishing regular pmds that
2446                  * points to regular pagetables. Use pmd_populate for that
2447                  */
2448                 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2449                 spin_unlock(pmd_ptl);
2450                 anon_vma_unlock_write(vma->anon_vma);
2451                 result = SCAN_FAIL;
2452                 goto out;
2453         }
2454
2455         /*
2456          * All pages are isolated and locked so anon_vma rmap
2457          * can't run anymore.
2458          */
2459         anon_vma_unlock_write(vma->anon_vma);
2460
2461         __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2462         pte_unmap(pte);
2463         __SetPageUptodate(new_page);
2464         pgtable = pmd_pgtable(_pmd);
2465
2466         _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2467         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2468
2469         /*
2470          * spin_lock() below is not the equivalent of smp_wmb(), so
2471          * this is needed to avoid the copy_huge_page writes to become
2472          * visible after the set_pmd_at() write.
2473          */
2474         smp_wmb();
2475
2476         spin_lock(pmd_ptl);
2477         BUG_ON(!pmd_none(*pmd));
2478         page_add_new_anon_rmap(new_page, vma, address, true);
2479         mem_cgroup_commit_charge(new_page, memcg, false, true);
2480         lru_cache_add_active_or_unevictable(new_page, vma);
2481         pgtable_trans_huge_deposit(mm, pmd, pgtable);
2482         set_pmd_at(mm, address, pmd, _pmd);
2483         update_mmu_cache_pmd(vma, address, pmd);
2484         spin_unlock(pmd_ptl);
2485
2486         *hpage = NULL;
2487
2488         khugepaged_pages_collapsed++;
2489         result = SCAN_SUCCEED;
2490 out_up_write:
2491         up_write(&mm->mmap_sem);
2492         trace_mm_collapse_huge_page(mm, isolated, result);
2493         return;
2494
2495 out_nolock:
2496         trace_mm_collapse_huge_page(mm, isolated, result);
2497         return;
2498 out:
2499         mem_cgroup_cancel_charge(new_page, memcg, true);
2500         goto out_up_write;
2501 }
2502
2503 static int khugepaged_scan_pmd(struct mm_struct *mm,
2504                                struct vm_area_struct *vma,
2505                                unsigned long address,
2506                                struct page **hpage)
2507 {
2508         pmd_t *pmd;
2509         pte_t *pte, *_pte;
2510         int ret = 0, none_or_zero = 0, result = 0;
2511         struct page *page = NULL;
2512         unsigned long _address;
2513         spinlock_t *ptl;
2514         int node = NUMA_NO_NODE;
2515         bool writable = false, referenced = false;
2516
2517         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2518
2519         pmd = mm_find_pmd(mm, address);
2520         if (!pmd) {
2521                 result = SCAN_PMD_NULL;
2522                 goto out;
2523         }
2524
2525         memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2526         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2527         for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2528              _pte++, _address += PAGE_SIZE) {
2529                 pte_t pteval = *_pte;
2530                 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2531                         if (!userfaultfd_armed(vma) &&
2532                             ++none_or_zero <= khugepaged_max_ptes_none) {
2533                                 continue;
2534                         } else {
2535                                 result = SCAN_EXCEED_NONE_PTE;
2536                                 goto out_unmap;
2537                         }
2538                 }
2539                 if (!pte_present(pteval)) {
2540                         result = SCAN_PTE_NON_PRESENT;
2541                         goto out_unmap;
2542                 }
2543                 if (pte_write(pteval))
2544                         writable = true;
2545
2546                 page = vm_normal_page(vma, _address, pteval);
2547                 if (unlikely(!page)) {
2548                         result = SCAN_PAGE_NULL;
2549                         goto out_unmap;
2550                 }
2551
2552                 /* TODO: teach khugepaged to collapse THP mapped with pte */
2553                 if (PageCompound(page)) {
2554                         result = SCAN_PAGE_COMPOUND;
2555                         goto out_unmap;
2556                 }
2557
2558                 /*
2559                  * Record which node the original page is from and save this
2560                  * information to khugepaged_node_load[].
2561                  * Khupaged will allocate hugepage from the node has the max
2562                  * hit record.
2563                  */
2564                 node = page_to_nid(page);
2565                 if (khugepaged_scan_abort(node)) {
2566                         result = SCAN_SCAN_ABORT;
2567                         goto out_unmap;
2568                 }
2569                 khugepaged_node_load[node]++;
2570                 if (!PageLRU(page)) {
2571                         result = SCAN_PAGE_LRU;
2572                         goto out_unmap;
2573                 }
2574                 if (PageLocked(page)) {
2575                         result = SCAN_PAGE_LOCK;
2576                         goto out_unmap;
2577                 }
2578                 if (!PageAnon(page)) {
2579                         result = SCAN_PAGE_ANON;
2580                         goto out_unmap;
2581                 }
2582
2583                 /*
2584                  * cannot use mapcount: can't collapse if there's a gup pin.
2585                  * The page must only be referenced by the scanned process
2586                  * and page swap cache.
2587                  */
2588                 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2589                         result = SCAN_PAGE_COUNT;
2590                         goto out_unmap;
2591                 }
2592                 if (pte_young(pteval) ||
2593                     page_is_young(page) || PageReferenced(page) ||
2594                     mmu_notifier_test_young(vma->vm_mm, address))
2595                         referenced = true;
2596         }
2597         if (writable) {
2598                 if (referenced) {
2599                         result = SCAN_SUCCEED;
2600                         ret = 1;
2601                 } else {
2602                         result = SCAN_NO_REFERENCED_PAGE;
2603                 }
2604         } else {
2605                 result = SCAN_PAGE_RO;
2606         }
2607 out_unmap:
2608         pte_unmap_unlock(pte, ptl);
2609         if (ret) {
2610                 node = khugepaged_find_target_node();
2611                 /* collapse_huge_page will return with the mmap_sem released */
2612                 collapse_huge_page(mm, address, hpage, vma, node);
2613         }
2614 out:
2615         trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
2616                                      none_or_zero, result);
2617         return ret;
2618 }
2619
2620 static void collect_mm_slot(struct mm_slot *mm_slot)
2621 {
2622         struct mm_struct *mm = mm_slot->mm;
2623
2624         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2625
2626         if (khugepaged_test_exit(mm)) {
2627                 /* free mm_slot */
2628                 hash_del(&mm_slot->hash);
2629                 list_del(&mm_slot->mm_node);
2630
2631                 /*
2632                  * Not strictly needed because the mm exited already.
2633                  *
2634                  * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2635                  */
2636
2637                 /* khugepaged_mm_lock actually not necessary for the below */
2638                 free_mm_slot(mm_slot);
2639                 mmdrop(mm);
2640         }
2641 }
2642
2643 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2644                                             struct page **hpage)
2645         __releases(&khugepaged_mm_lock)
2646         __acquires(&khugepaged_mm_lock)
2647 {
2648         struct mm_slot *mm_slot;
2649         struct mm_struct *mm;
2650         struct vm_area_struct *vma;
2651         int progress = 0;
2652
2653         VM_BUG_ON(!pages);
2654         VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2655
2656         if (khugepaged_scan.mm_slot)
2657                 mm_slot = khugepaged_scan.mm_slot;
2658         else {
2659                 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2660                                      struct mm_slot, mm_node);
2661                 khugepaged_scan.address = 0;
2662                 khugepaged_scan.mm_slot = mm_slot;
2663         }
2664         spin_unlock(&khugepaged_mm_lock);
2665
2666         mm = mm_slot->mm;
2667         down_read(&mm->mmap_sem);
2668         if (unlikely(khugepaged_test_exit(mm)))
2669                 vma = NULL;
2670         else
2671                 vma = find_vma(mm, khugepaged_scan.address);
2672
2673         progress++;
2674         for (; vma; vma = vma->vm_next) {
2675                 unsigned long hstart, hend;
2676
2677                 cond_resched();
2678                 if (unlikely(khugepaged_test_exit(mm))) {
2679                         progress++;
2680                         break;
2681                 }
2682                 if (!hugepage_vma_check(vma)) {
2683 skip:
2684                         progress++;
2685                         continue;
2686                 }
2687                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2688                 hend = vma->vm_end & HPAGE_PMD_MASK;
2689                 if (hstart >= hend)
2690                         goto skip;
2691                 if (khugepaged_scan.address > hend)
2692                         goto skip;
2693                 if (khugepaged_scan.address < hstart)
2694                         khugepaged_scan.address = hstart;
2695                 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2696
2697                 while (khugepaged_scan.address < hend) {
2698                         int ret;
2699                         cond_resched();
2700                         if (unlikely(khugepaged_test_exit(mm)))
2701                                 goto breakouterloop;
2702
2703                         VM_BUG_ON(khugepaged_scan.address < hstart ||
2704                                   khugepaged_scan.address + HPAGE_PMD_SIZE >
2705                                   hend);
2706                         ret = khugepaged_scan_pmd(mm, vma,
2707                                                   khugepaged_scan.address,
2708                                                   hpage);
2709                         /* move to next address */
2710                         khugepaged_scan.address += HPAGE_PMD_SIZE;
2711                         progress += HPAGE_PMD_NR;
2712                         if (ret)
2713                                 /* we released mmap_sem so break loop */
2714                                 goto breakouterloop_mmap_sem;
2715                         if (progress >= pages)
2716                                 goto breakouterloop;
2717                 }
2718         }
2719 breakouterloop:
2720         up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2721 breakouterloop_mmap_sem:
2722
2723         spin_lock(&khugepaged_mm_lock);
2724         VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2725         /*
2726          * Release the current mm_slot if this mm is about to die, or
2727          * if we scanned all vmas of this mm.
2728          */
2729         if (khugepaged_test_exit(mm) || !vma) {
2730                 /*
2731                  * Make sure that if mm_users is reaching zero while
2732                  * khugepaged runs here, khugepaged_exit will find
2733                  * mm_slot not pointing to the exiting mm.
2734                  */
2735                 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2736                         khugepaged_scan.mm_slot = list_entry(
2737                                 mm_slot->mm_node.next,
2738                                 struct mm_slot, mm_node);
2739                         khugepaged_scan.address = 0;
2740                 } else {
2741                         khugepaged_scan.mm_slot = NULL;
2742                         khugepaged_full_scans++;
2743                 }
2744
2745                 collect_mm_slot(mm_slot);
2746         }
2747
2748         return progress;
2749 }
2750
2751 static int khugepaged_has_work(void)
2752 {
2753         return !list_empty(&khugepaged_scan.mm_head) &&
2754                 khugepaged_enabled();
2755 }
2756
2757 static int khugepaged_wait_event(void)
2758 {
2759         return !list_empty(&khugepaged_scan.mm_head) ||
2760                 kthread_should_stop();
2761 }
2762
2763 static void khugepaged_do_scan(void)
2764 {
2765         struct page *hpage = NULL;
2766         unsigned int progress = 0, pass_through_head = 0;
2767         unsigned int pages = khugepaged_pages_to_scan;
2768         bool wait = true;
2769
2770         barrier(); /* write khugepaged_pages_to_scan to local stack */
2771
2772         while (progress < pages) {
2773                 if (!khugepaged_prealloc_page(&hpage, &wait))
2774                         break;
2775
2776                 cond_resched();
2777
2778                 if (unlikely(kthread_should_stop() || try_to_freeze()))
2779                         break;
2780
2781                 spin_lock(&khugepaged_mm_lock);
2782                 if (!khugepaged_scan.mm_slot)
2783                         pass_through_head++;
2784                 if (khugepaged_has_work() &&
2785                     pass_through_head < 2)
2786                         progress += khugepaged_scan_mm_slot(pages - progress,
2787                                                             &hpage);
2788                 else
2789                         progress = pages;
2790                 spin_unlock(&khugepaged_mm_lock);
2791         }
2792
2793         if (!IS_ERR_OR_NULL(hpage))
2794                 put_page(hpage);
2795 }
2796
2797 static bool khugepaged_should_wakeup(void)
2798 {
2799         return kthread_should_stop() ||
2800                time_after_eq(jiffies, khugepaged_sleep_expire);
2801 }
2802
2803 static void khugepaged_wait_work(void)
2804 {
2805         if (khugepaged_has_work()) {
2806                 const unsigned long scan_sleep_jiffies =
2807                         msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
2808
2809                 if (!scan_sleep_jiffies)
2810                         return;
2811
2812                 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
2813                 wait_event_freezable_timeout(khugepaged_wait,
2814                                              khugepaged_should_wakeup(),
2815                                              scan_sleep_jiffies);
2816                 return;
2817         }
2818
2819         if (khugepaged_enabled())
2820                 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2821 }
2822
2823 static int khugepaged(void *none)
2824 {
2825         struct mm_slot *mm_slot;
2826
2827         set_freezable();
2828         set_user_nice(current, MAX_NICE);
2829
2830         while (!kthread_should_stop()) {
2831                 khugepaged_do_scan();
2832                 khugepaged_wait_work();
2833         }
2834
2835         spin_lock(&khugepaged_mm_lock);
2836         mm_slot = khugepaged_scan.mm_slot;
2837         khugepaged_scan.mm_slot = NULL;
2838         if (mm_slot)
2839                 collect_mm_slot(mm_slot);
2840         spin_unlock(&khugepaged_mm_lock);
2841         return 0;
2842 }
2843
2844 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2845                 unsigned long haddr, pmd_t *pmd)
2846 {
2847         struct mm_struct *mm = vma->vm_mm;
2848         pgtable_t pgtable;
2849         pmd_t _pmd;
2850         int i;
2851
2852         /* leave pmd empty until pte is filled */
2853         pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2854
2855         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2856         pmd_populate(mm, &_pmd, pgtable);
2857
2858         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2859                 pte_t *pte, entry;
2860                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2861                 entry = pte_mkspecial(entry);
2862                 pte = pte_offset_map(&_pmd, haddr);
2863                 VM_BUG_ON(!pte_none(*pte));
2864                 set_pte_at(mm, haddr, pte, entry);
2865                 pte_unmap(pte);
2866         }
2867         smp_wmb(); /* make pte visible before pmd */
2868         pmd_populate(mm, pmd, pgtable);
2869         put_huge_zero_page();
2870 }
2871
2872 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2873                 unsigned long haddr, bool freeze)
2874 {
2875         struct mm_struct *mm = vma->vm_mm;
2876         struct page *page;
2877         pgtable_t pgtable;
2878         pmd_t _pmd;
2879         bool young, write, dirty;
2880         unsigned long addr;
2881         int i;
2882
2883         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2884         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2885         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2886         VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
2887
2888         count_vm_event(THP_SPLIT_PMD);
2889
2890         if (vma_is_dax(vma)) {
2891                 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2892                 if (is_huge_zero_pmd(_pmd))
2893                         put_huge_zero_page();
2894                 return;
2895         } else if (is_huge_zero_pmd(*pmd)) {
2896                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2897         }
2898
2899         page = pmd_page(*pmd);
2900         VM_BUG_ON_PAGE(!page_count(page), page);
2901         page_ref_add(page, HPAGE_PMD_NR - 1);
2902         write = pmd_write(*pmd);
2903         young = pmd_young(*pmd);
2904         dirty = pmd_dirty(*pmd);
2905
2906         pmdp_huge_split_prepare(vma, haddr, pmd);
2907         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2908         pmd_populate(mm, &_pmd, pgtable);
2909
2910         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2911                 pte_t entry, *pte;
2912                 /*
2913                  * Note that NUMA hinting access restrictions are not
2914                  * transferred to avoid any possibility of altering
2915                  * permissions across VMAs.
2916                  */
2917                 if (freeze) {
2918                         swp_entry_t swp_entry;
2919                         swp_entry = make_migration_entry(page + i, write);
2920                         entry = swp_entry_to_pte(swp_entry);
2921                 } else {
2922                         entry = mk_pte(page + i, vma->vm_page_prot);
2923                         entry = maybe_mkwrite(entry, vma);
2924                         if (!write)
2925                                 entry = pte_wrprotect(entry);
2926                         if (!young)
2927                                 entry = pte_mkold(entry);
2928                 }
2929                 if (dirty)
2930                         SetPageDirty(page + i);
2931                 pte = pte_offset_map(&_pmd, addr);
2932                 BUG_ON(!pte_none(*pte));
2933                 set_pte_at(mm, addr, pte, entry);
2934                 atomic_inc(&page[i]._mapcount);
2935                 pte_unmap(pte);
2936         }
2937
2938         /*
2939          * Set PG_double_map before dropping compound_mapcount to avoid
2940          * false-negative page_mapped().
2941          */
2942         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2943                 for (i = 0; i < HPAGE_PMD_NR; i++)
2944                         atomic_inc(&page[i]._mapcount);
2945         }
2946
2947         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2948                 /* Last compound_mapcount is gone. */
2949                 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
2950                 if (TestClearPageDoubleMap(page)) {
2951                         /* No need in mapcount reference anymore */
2952                         for (i = 0; i < HPAGE_PMD_NR; i++)
2953                                 atomic_dec(&page[i]._mapcount);
2954                 }
2955         }
2956
2957         smp_wmb(); /* make pte visible before pmd */
2958         /*
2959          * Up to this point the pmd is present and huge and userland has the
2960          * whole access to the hugepage during the split (which happens in
2961          * place). If we overwrite the pmd with the not-huge version pointing
2962          * to the pte here (which of course we could if all CPUs were bug
2963          * free), userland could trigger a small page size TLB miss on the
2964          * small sized TLB while the hugepage TLB entry is still established in
2965          * the huge TLB. Some CPU doesn't like that.
2966          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2967          * 383 on page 93. Intel should be safe but is also warns that it's
2968          * only safe if the permission and cache attributes of the two entries
2969          * loaded in the two TLB is identical (which should be the case here).
2970          * But it is generally safer to never allow small and huge TLB entries
2971          * for the same virtual address to be loaded simultaneously. So instead
2972          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2973          * current pmd notpresent (atomically because here the pmd_trans_huge
2974          * and pmd_trans_splitting must remain set at all times on the pmd
2975          * until the split is complete for this pmd), then we flush the SMP TLB
2976          * and finally we write the non-huge version of the pmd entry with
2977          * pmd_populate.
2978          */
2979         pmdp_invalidate(vma, haddr, pmd);
2980         pmd_populate(mm, pmd, pgtable);
2981
2982         if (freeze) {
2983                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2984                         page_remove_rmap(page + i, false);
2985                         put_page(page + i);
2986                 }
2987         }
2988 }
2989
2990 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2991                 unsigned long address, bool freeze)
2992 {
2993         spinlock_t *ptl;
2994         struct mm_struct *mm = vma->vm_mm;
2995         unsigned long haddr = address & HPAGE_PMD_MASK;
2996
2997         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2998         ptl = pmd_lock(mm, pmd);
2999         if (pmd_trans_huge(*pmd)) {
3000                 struct page *page = pmd_page(*pmd);
3001                 if (PageMlocked(page))
3002                         clear_page_mlock(page);
3003         } else if (!pmd_devmap(*pmd))
3004                 goto out;
3005         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
3006 out:
3007         spin_unlock(ptl);
3008         mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
3009 }
3010
3011 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
3012                 bool freeze, struct page *page)
3013 {
3014         pgd_t *pgd;
3015         pud_t *pud;
3016         pmd_t *pmd;
3017
3018         pgd = pgd_offset(vma->vm_mm, address);
3019         if (!pgd_present(*pgd))
3020                 return;
3021
3022         pud = pud_offset(pgd, address);
3023         if (!pud_present(*pud))
3024                 return;
3025
3026         pmd = pmd_offset(pud, address);
3027         if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)))
3028                 return;
3029
3030         /*
3031          * If caller asks to setup a migration entries, we need a page to check
3032          * pmd against. Otherwise we can end up replacing wrong page.
3033          */
3034         VM_BUG_ON(freeze && !page);
3035         if (page && page != pmd_page(*pmd))
3036                 return;
3037
3038         /*
3039          * Caller holds the mmap_sem write mode or the anon_vma lock,
3040          * so a huge pmd cannot materialize from under us (khugepaged
3041          * holds both the mmap_sem write mode and the anon_vma lock
3042          * write mode).
3043          */
3044         __split_huge_pmd(vma, pmd, address, freeze);
3045 }
3046
3047 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3048                              unsigned long start,
3049                              unsigned long end,
3050                              long adjust_next)
3051 {
3052         /*
3053          * If the new start address isn't hpage aligned and it could
3054          * previously contain an hugepage: check if we need to split
3055          * an huge pmd.
3056          */
3057         if (start & ~HPAGE_PMD_MASK &&
3058             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3059             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3060                 split_huge_pmd_address(vma, start, false, NULL);
3061
3062         /*
3063          * If the new end address isn't hpage aligned and it could
3064          * previously contain an hugepage: check if we need to split
3065          * an huge pmd.
3066          */
3067         if (end & ~HPAGE_PMD_MASK &&
3068             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3069             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3070                 split_huge_pmd_address(vma, end, false, NULL);
3071
3072         /*
3073          * If we're also updating the vma->vm_next->vm_start, if the new
3074          * vm_next->vm_start isn't page aligned and it could previously
3075          * contain an hugepage: check if we need to split an huge pmd.
3076          */
3077         if (adjust_next > 0) {
3078                 struct vm_area_struct *next = vma->vm_next;
3079                 unsigned long nstart = next->vm_start;
3080                 nstart += adjust_next << PAGE_SHIFT;
3081                 if (nstart & ~HPAGE_PMD_MASK &&
3082                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3083                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3084                         split_huge_pmd_address(next, nstart, false, NULL);
3085         }
3086 }
3087
3088 static void freeze_page(struct page *page)
3089 {
3090         enum ttu_flags ttu_flags = TTU_MIGRATION | TTU_IGNORE_MLOCK |
3091                 TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED;
3092         int i, ret;
3093
3094         VM_BUG_ON_PAGE(!PageHead(page), page);
3095
3096         /* We only need TTU_SPLIT_HUGE_PMD once */
3097         ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
3098         for (i = 1; !ret && i < HPAGE_PMD_NR; i++) {
3099                 /* Cut short if the page is unmapped */
3100                 if (page_count(page) == 1)
3101                         return;
3102
3103                 ret = try_to_unmap(page + i, ttu_flags);
3104         }
3105         VM_BUG_ON(ret);
3106 }
3107
3108 static void unfreeze_page(struct page *page)
3109 {
3110         int i;
3111
3112         for (i = 0; i < HPAGE_PMD_NR; i++)
3113                 remove_migration_ptes(page + i, page + i, true);
3114 }
3115
3116 static void __split_huge_page_tail(struct page *head, int tail,
3117                 struct lruvec *lruvec, struct list_head *list)
3118 {
3119         struct page *page_tail = head + tail;
3120
3121         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
3122         VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
3123
3124         /*
3125          * tail_page->_refcount is zero and not changing from under us. But
3126          * get_page_unless_zero() may be running from under us on the
3127          * tail_page. If we used atomic_set() below instead of atomic_inc(), we
3128          * would then run atomic_set() concurrently with
3129          * get_page_unless_zero(), and atomic_set() is implemented in C not
3130          * using locked ops. spin_unlock on x86 sometime uses locked ops
3131          * because of PPro errata 66, 92, so unless somebody can guarantee
3132          * atomic_set() here would be safe on all archs (and not only on x86),
3133          * it's safer to use atomic_inc().
3134          */
3135         page_ref_inc(page_tail);
3136
3137         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3138         page_tail->flags |= (head->flags &
3139                         ((1L << PG_referenced) |
3140                          (1L << PG_swapbacked) |
3141                          (1L << PG_mlocked) |
3142                          (1L << PG_uptodate) |
3143                          (1L << PG_active) |
3144                          (1L << PG_locked) |
3145                          (1L << PG_unevictable) |
3146                          (1L << PG_dirty)));
3147
3148         /*
3149          * After clearing PageTail the gup refcount can be released.
3150          * Page flags also must be visible before we make the page non-compound.
3151          */
3152         smp_wmb();
3153
3154         clear_compound_head(page_tail);
3155
3156         if (page_is_young(head))
3157                 set_page_young(page_tail);
3158         if (page_is_idle(head))
3159                 set_page_idle(page_tail);
3160
3161         /* ->mapping in first tail page is compound_mapcount */
3162         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3163                         page_tail);
3164         page_tail->mapping = head->mapping;
3165
3166         page_tail->index = head->index + tail;
3167         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3168         lru_add_page_tail(head, page_tail, lruvec, list);
3169 }
3170
3171 static void __split_huge_page(struct page *page, struct list_head *list)
3172 {
3173         struct page *head = compound_head(page);
3174         struct zone *zone = page_zone(head);
3175         struct lruvec *lruvec;
3176         int i;
3177
3178         /* prevent PageLRU to go away from under us, and freeze lru stats */
3179         spin_lock_irq(&zone->lru_lock);
3180         lruvec = mem_cgroup_page_lruvec(head, zone);
3181
3182         /* complete memcg works before add pages to LRU */
3183         mem_cgroup_split_huge_fixup(head);
3184
3185         for (i = HPAGE_PMD_NR - 1; i >= 1; i--)
3186                 __split_huge_page_tail(head, i, lruvec, list);
3187
3188         ClearPageCompound(head);
3189         spin_unlock_irq(&zone->lru_lock);
3190
3191         unfreeze_page(head);
3192
3193         for (i = 0; i < HPAGE_PMD_NR; i++) {
3194                 struct page *subpage = head + i;
3195                 if (subpage == page)
3196                         continue;
3197                 unlock_page(subpage);
3198
3199                 /*
3200                  * Subpages may be freed if there wasn't any mapping
3201                  * like if add_to_swap() is running on a lru page that
3202                  * had its mapping zapped. And freeing these pages
3203                  * requires taking the lru_lock so we do the put_page
3204                  * of the tail pages after the split is complete.
3205                  */
3206                 put_page(subpage);
3207         }
3208 }
3209
3210 int total_mapcount(struct page *page)
3211 {
3212         int i, ret;
3213
3214         VM_BUG_ON_PAGE(PageTail(page), page);
3215
3216         if (likely(!PageCompound(page)))
3217                 return atomic_read(&page->_mapcount) + 1;
3218
3219         ret = compound_mapcount(page);
3220         if (PageHuge(page))
3221                 return ret;
3222         for (i = 0; i < HPAGE_PMD_NR; i++)
3223                 ret += atomic_read(&page[i]._mapcount) + 1;
3224         if (PageDoubleMap(page))
3225                 ret -= HPAGE_PMD_NR;
3226         return ret;
3227 }
3228
3229 /*
3230  * This calculates accurately how many mappings a transparent hugepage
3231  * has (unlike page_mapcount() which isn't fully accurate). This full
3232  * accuracy is primarily needed to know if copy-on-write faults can
3233  * reuse the page and change the mapping to read-write instead of
3234  * copying them. At the same time this returns the total_mapcount too.
3235  *
3236  * The function returns the highest mapcount any one of the subpages
3237  * has. If the return value is one, even if different processes are
3238  * mapping different subpages of the transparent hugepage, they can
3239  * all reuse it, because each process is reusing a different subpage.
3240  *
3241  * The total_mapcount is instead counting all virtual mappings of the
3242  * subpages. If the total_mapcount is equal to "one", it tells the
3243  * caller all mappings belong to the same "mm" and in turn the
3244  * anon_vma of the transparent hugepage can become the vma->anon_vma
3245  * local one as no other process may be mapping any of the subpages.
3246  *
3247  * It would be more accurate to replace page_mapcount() with
3248  * page_trans_huge_mapcount(), however we only use
3249  * page_trans_huge_mapcount() in the copy-on-write faults where we
3250  * need full accuracy to avoid breaking page pinning, because
3251  * page_trans_huge_mapcount() is slower than page_mapcount().
3252  */
3253 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
3254 {
3255         int i, ret, _total_mapcount, mapcount;
3256
3257         /* hugetlbfs shouldn't call it */
3258         VM_BUG_ON_PAGE(PageHuge(page), page);
3259
3260         if (likely(!PageTransCompound(page))) {
3261                 mapcount = atomic_read(&page->_mapcount) + 1;
3262                 if (total_mapcount)
3263                         *total_mapcount = mapcount;
3264                 return mapcount;
3265         }
3266
3267         page = compound_head(page);
3268
3269         _total_mapcount = ret = 0;
3270         for (i = 0; i < HPAGE_PMD_NR; i++) {
3271                 mapcount = atomic_read(&page[i]._mapcount) + 1;
3272                 ret = max(ret, mapcount);
3273                 _total_mapcount += mapcount;
3274         }
3275         if (PageDoubleMap(page)) {
3276                 ret -= 1;
3277                 _total_mapcount -= HPAGE_PMD_NR;
3278         }
3279         mapcount = compound_mapcount(page);
3280         ret += mapcount;
3281         _total_mapcount += mapcount;
3282         if (total_mapcount)
3283                 *total_mapcount = _total_mapcount;
3284         return ret;
3285 }
3286
3287 /*
3288  * This function splits huge page into normal pages. @page can point to any
3289  * subpage of huge page to split. Split doesn't change the position of @page.
3290  *
3291  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3292  * The huge page must be locked.
3293  *
3294  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3295  *
3296  * Both head page and tail pages will inherit mapping, flags, and so on from
3297  * the hugepage.
3298  *
3299  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3300  * they are not mapped.
3301  *
3302  * Returns 0 if the hugepage is split successfully.
3303  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3304  * us.
3305  */
3306 int split_huge_page_to_list(struct page *page, struct list_head *list)
3307 {
3308         struct page *head = compound_head(page);
3309         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
3310         struct anon_vma *anon_vma;
3311         int count, mapcount, ret;
3312         bool mlocked;
3313         unsigned long flags;
3314
3315         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3316         VM_BUG_ON_PAGE(!PageAnon(page), page);
3317         VM_BUG_ON_PAGE(!PageLocked(page), page);
3318         VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3319         VM_BUG_ON_PAGE(!PageCompound(page), page);
3320
3321         /*
3322          * The caller does not necessarily hold an mmap_sem that would prevent
3323          * the anon_vma disappearing so we first we take a reference to it
3324          * and then lock the anon_vma for write. This is similar to
3325          * page_lock_anon_vma_read except the write lock is taken to serialise
3326          * against parallel split or collapse operations.
3327          */
3328         anon_vma = page_get_anon_vma(head);
3329         if (!anon_vma) {
3330                 ret = -EBUSY;
3331                 goto out;
3332         }
3333         anon_vma_lock_write(anon_vma);
3334
3335         /*
3336          * Racy check if we can split the page, before freeze_page() will
3337          * split PMDs
3338          */
3339         if (total_mapcount(head) != page_count(head) - 1) {
3340                 ret = -EBUSY;
3341                 goto out_unlock;
3342         }
3343
3344         mlocked = PageMlocked(page);
3345         freeze_page(head);
3346         VM_BUG_ON_PAGE(compound_mapcount(head), head);
3347
3348         /* Make sure the page is not on per-CPU pagevec as it takes pin */
3349         if (mlocked)
3350                 lru_add_drain();
3351
3352         /* Prevent deferred_split_scan() touching ->_refcount */
3353         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3354         count = page_count(head);
3355         mapcount = total_mapcount(head);
3356         if (!mapcount && count == 1) {
3357                 if (!list_empty(page_deferred_list(head))) {
3358                         pgdata->split_queue_len--;
3359                         list_del(page_deferred_list(head));
3360                 }
3361                 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3362                 __split_huge_page(page, list);
3363                 ret = 0;
3364         } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
3365                 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3366                 pr_alert("total_mapcount: %u, page_count(): %u\n",
3367                                 mapcount, count);
3368                 if (PageTail(page))
3369                         dump_page(head, NULL);
3370                 dump_page(page, "total_mapcount(head) > 0");
3371                 BUG();
3372         } else {
3373                 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3374                 unfreeze_page(head);
3375                 ret = -EBUSY;
3376         }
3377
3378 out_unlock:
3379         anon_vma_unlock_write(anon_vma);
3380         put_anon_vma(anon_vma);
3381 out:
3382         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3383         return ret;
3384 }
3385
3386 void free_transhuge_page(struct page *page)
3387 {
3388         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3389         unsigned long flags;
3390
3391         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3392         if (!list_empty(page_deferred_list(page))) {
3393                 pgdata->split_queue_len--;
3394                 list_del(page_deferred_list(page));
3395         }
3396         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3397         free_compound_page(page);
3398 }
3399
3400 void deferred_split_huge_page(struct page *page)
3401 {
3402         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
3403         unsigned long flags;
3404
3405         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3406
3407         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3408         if (list_empty(page_deferred_list(page))) {
3409                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
3410                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
3411                 pgdata->split_queue_len++;
3412         }
3413         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3414 }
3415
3416 static unsigned long deferred_split_count(struct shrinker *shrink,
3417                 struct shrink_control *sc)
3418 {
3419         struct pglist_data *pgdata = NODE_DATA(sc->nid);
3420         return ACCESS_ONCE(pgdata->split_queue_len);
3421 }
3422
3423 static unsigned long deferred_split_scan(struct shrinker *shrink,
3424                 struct shrink_control *sc)
3425 {
3426         struct pglist_data *pgdata = NODE_DATA(sc->nid);
3427         unsigned long flags;
3428         LIST_HEAD(list), *pos, *next;
3429         struct page *page;
3430         int split = 0;
3431
3432         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3433         /* Take pin on all head pages to avoid freeing them under us */
3434         list_for_each_safe(pos, next, &pgdata->split_queue) {
3435                 page = list_entry((void *)pos, struct page, mapping);
3436                 page = compound_head(page);
3437                 if (get_page_unless_zero(page)) {
3438                         list_move(page_deferred_list(page), &list);
3439                 } else {
3440                         /* We lost race with put_compound_page() */
3441                         list_del_init(page_deferred_list(page));
3442                         pgdata->split_queue_len--;
3443                 }
3444                 if (!--sc->nr_to_scan)
3445                         break;
3446         }
3447         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3448
3449         list_for_each_safe(pos, next, &list) {
3450                 page = list_entry((void *)pos, struct page, mapping);
3451                 lock_page(page);
3452                 /* split_huge_page() removes page from list on success */
3453                 if (!split_huge_page(page))
3454                         split++;
3455                 unlock_page(page);
3456                 put_page(page);
3457         }
3458
3459         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
3460         list_splice_tail(&list, &pgdata->split_queue);
3461         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
3462
3463         /*
3464          * Stop shrinker if we didn't split any page, but the queue is empty.
3465          * This can happen if pages were freed under us.
3466          */
3467         if (!split && list_empty(&pgdata->split_queue))
3468                 return SHRINK_STOP;
3469         return split;
3470 }
3471
3472 static struct shrinker deferred_split_shrinker = {
3473         .count_objects = deferred_split_count,
3474         .scan_objects = deferred_split_scan,
3475         .seeks = DEFAULT_SEEKS,
3476         .flags = SHRINKER_NUMA_AWARE,
3477 };
3478
3479 #ifdef CONFIG_DEBUG_FS
3480 static int split_huge_pages_set(void *data, u64 val)
3481 {
3482         struct zone *zone;
3483         struct page *page;
3484         unsigned long pfn, max_zone_pfn;
3485         unsigned long total = 0, split = 0;
3486
3487         if (val != 1)
3488                 return -EINVAL;
3489
3490         for_each_populated_zone(zone) {
3491                 max_zone_pfn = zone_end_pfn(zone);
3492                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3493                         if (!pfn_valid(pfn))
3494                                 continue;
3495
3496                         page = pfn_to_page(pfn);
3497                         if (!get_page_unless_zero(page))
3498                                 continue;
3499
3500                         if (zone != page_zone(page))
3501                                 goto next;
3502
3503                         if (!PageHead(page) || !PageAnon(page) ||
3504                                         PageHuge(page))
3505                                 goto next;
3506
3507                         total++;
3508                         lock_page(page);
3509                         if (!split_huge_page(page))
3510                                 split++;
3511                         unlock_page(page);
3512 next:
3513                         put_page(page);
3514                 }
3515         }
3516
3517         pr_info("%lu of %lu THP split\n", split, total);
3518
3519         return 0;
3520 }
3521 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3522                 "%llu\n");
3523
3524 static int __init split_huge_pages_debugfs(void)
3525 {
3526         void *ret;
3527
3528         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3529                         &split_huge_pages_fops);
3530         if (!ret)
3531                 pr_warn("Failed to create split_huge_pages in debugfs");
3532         return 0;
3533 }
3534 late_initcall(split_huge_pages_debugfs);
3535 #endif