mm/huge_memory.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  Copyright (C) 2009  Red Hat, Inc.
   4  */
   5
   6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   7
   8 #include <linux/mm.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/coredump.h>
  11 #include <linux/sched/numa_balancing.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/khugepaged.h>
  22 #include <linux/freezer.h>
  23 #include <linux/pfn_t.h>
  24 #include <linux/mman.h>
  25 #include <linux/memremap.h>
  26 #include <linux/pagemap.h>
  27 #include <linux/debugfs.h>
  28 #include <linux/migrate.h>
  29 #include <linux/hashtable.h>
  30 #include <linux/userfaultfd_k.h>
  31 #include <linux/page_idle.h>
  32 #include <linux/shmem_fs.h>
  33 #include <linux/oom.h>
  34 #include <linux/numa.h>
  35 #include <linux/page_owner.h>
  36
  37 #include <asm/tlb.h>
  38 #include <asm/pgalloc.h>
  39 #include "internal.h"
  40
  41 /*
  42  * By default, transparent hugepage support is disabled in order to avoid
  43  * risking an increased memory footprint for applications that are not
  44  * guaranteed to benefit from it. When transparent hugepage support is
  45  * enabled, it is for all mappings, and khugepaged scans all mappings.
  46  * Defrag is invoked by khugepaged hugepage allocations and by page faults
  47  * for all hugepage allocations.
  48  */
  49 unsigned long transparent_hugepage_flags __read_mostly =
  50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
  51         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
  52 #endif
  53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
  54         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
  55 #endif
  56         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
  57         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
  58         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
  59
  60 static struct shrinker deferred_split_shrinker;
  61
  62 static atomic_t huge_zero_refcount;
  63 struct page *huge_zero_page __read_mostly;
  64
  65 bool transparent_hugepage_enabled(struct vm_area_struct *vma)
  66 {
  67         /* The addr is used to check if the vma size fits */
  68         unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
  69
  70         if (!transhuge_vma_suitable(vma, addr))
  71                 return false;
  72         if (vma_is_anonymous(vma))
  73                 return __transparent_hugepage_enabled(vma);
  74         if (vma_is_shmem(vma))
  75                 return shmem_huge_enabled(vma);
  76
  77         return false;
  78 }
  79
  80 static struct page *get_huge_zero_page(void)
  81 {
  82         struct page *zero_page;
  83 retry:
  84         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
  85                 return READ_ONCE(huge_zero_page);
  86
  87         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
  88                         HPAGE_PMD_ORDER);
  89         if (!zero_page) {
  90                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
  91                 return NULL;
  92         }
  93         count_vm_event(THP_ZERO_PAGE_ALLOC);
  94         preempt_disable();
  95         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
  96                 preempt_enable();
  97                 __free_pages(zero_page, compound_order(zero_page));
  98                 goto retry;
  99         }
 100
 101         /* We take additional reference here. It will be put back by shrinker */
 102         atomic_set(&huge_zero_refcount, 2);
 103         preempt_enable();
 104         return READ_ONCE(huge_zero_page);
 105 }
 106
 107 static void put_huge_zero_page(void)
 108 {
 109         /*
 110          * Counter should never go to zero here. Only shrinker can put
 111          * last reference.
 112          */
 113         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 114 }
 115
 116 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
 117 {
 118         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 119                 return READ_ONCE(huge_zero_page);
 120
 121         if (!get_huge_zero_page())
 122                 return NULL;
 123
 124         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 125                 put_huge_zero_page();
 126
 127         return READ_ONCE(huge_zero_page);
 128 }
 129
 130 void mm_put_huge_zero_page(struct mm_struct *mm)
 131 {
 132         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
 133                 put_huge_zero_page();
 134 }
 135
 136 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
 137                                         struct shrink_control *sc)
 138 {
 139         /* we can free zero page only if last reference remains */
 140         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 141 }
 142
 143 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 144                                        struct shrink_control *sc)
 145 {
 146         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 147                 struct page *zero_page = xchg(&huge_zero_page, NULL);
 148                 BUG_ON(zero_page == NULL);
 149                 __free_pages(zero_page, compound_order(zero_page));
 150                 return HPAGE_PMD_NR;
 151         }
 152
 153         return 0;
 154 }
 155
 156 static struct shrinker huge_zero_page_shrinker = {
 157         .count_objects = shrink_huge_zero_page_count,
 158         .scan_objects = shrink_huge_zero_page_scan,
 159         .seeks = DEFAULT_SEEKS,
 160 };
 161
 162 #ifdef CONFIG_SYSFS
 163 static ssize_t enabled_show(struct kobject *kobj,
 164                             struct kobj_attribute *attr, char *buf)
 165 {
 166         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
 167                 return sprintf(buf, "[always] madvise never\n");
 168         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
 169                 return sprintf(buf, "always [madvise] never\n");
 170         else
 171                 return sprintf(buf, "always madvise [never]\n");
 172 }
 173
 174 static ssize_t enabled_store(struct kobject *kobj,
 175                              struct kobj_attribute *attr,
 176                              const char *buf, size_t count)
 177 {
 178         ssize_t ret = count;
 179
 180         if (sysfs_streq(buf, "always")) {
 181                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 182                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 183         } else if (sysfs_streq(buf, "madvise")) {
 184                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 185                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 186         } else if (sysfs_streq(buf, "never")) {
 187                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
 188                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
 189         } else
 190                 ret = -EINVAL;
 191
 192         if (ret > 0) {
 193                 int err = start_stop_khugepaged();
 194                 if (err)
 195                         ret = err;
 196         }
 197         return ret;
 198 }
 199 static struct kobj_attribute enabled_attr =
 200         __ATTR(enabled, 0644, enabled_show, enabled_store);
 201
 202 ssize_t single_hugepage_flag_show(struct kobject *kobj,
 203                                 struct kobj_attribute *attr, char *buf,
 204                                 enum transparent_hugepage_flag flag)
 205 {
 206         return sprintf(buf, "%d\n",
 207                        !!test_bit(flag, &transparent_hugepage_flags));
 208 }
 209
 210 ssize_t single_hugepage_flag_store(struct kobject *kobj,
 211                                  struct kobj_attribute *attr,
 212                                  const char *buf, size_t count,
 213                                  enum transparent_hugepage_flag flag)
 214 {
 215         unsigned long value;
 216         int ret;
 217
 218         ret = kstrtoul(buf, 10, &value);
 219         if (ret < 0)
 220                 return ret;
 221         if (value > 1)
 222                 return -EINVAL;
 223
 224         if (value)
 225                 set_bit(flag, &transparent_hugepage_flags);
 226         else
 227                 clear_bit(flag, &transparent_hugepage_flags);
 228
 229         return count;
 230 }
 231
 232 static ssize_t defrag_show(struct kobject *kobj,
 233                            struct kobj_attribute *attr, char *buf)
 234 {
 235         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 236                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
 237         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 238                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
 239         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 240                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
 241         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 242                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
 243         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
 244 }
 245
 246 static ssize_t defrag_store(struct kobject *kobj,
 247                             struct kobj_attribute *attr,
 248                             const char *buf, size_t count)
 249 {
 250         if (sysfs_streq(buf, "always")) {
 251                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 253                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 254                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 255         } else if (sysfs_streq(buf, "defer+madvise")) {
 256                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 257                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 259                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 260         } else if (sysfs_streq(buf, "defer")) {
 261                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 262                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 263                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 264                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 265         } else if (sysfs_streq(buf, "madvise")) {
 266                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 268                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 269                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 270         } else if (sysfs_streq(buf, "never")) {
 271                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
 272                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
 273                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
 274                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
 275         } else
 276                 return -EINVAL;
 277
 278         return count;
 279 }
 280 static struct kobj_attribute defrag_attr =
 281         __ATTR(defrag, 0644, defrag_show, defrag_store);
 282
 283 static ssize_t use_zero_page_show(struct kobject *kobj,
 284                 struct kobj_attribute *attr, char *buf)
 285 {
 286         return single_hugepage_flag_show(kobj, attr, buf,
 287                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 288 }
 289 static ssize_t use_zero_page_store(struct kobject *kobj,
 290                 struct kobj_attribute *attr, const char *buf, size_t count)
 291 {
 292         return single_hugepage_flag_store(kobj, attr, buf, count,
 293                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 294 }
 295 static struct kobj_attribute use_zero_page_attr =
 296         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
 297
 298 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 299                 struct kobj_attribute *attr, char *buf)
 300 {
 301         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
 302 }
 303 static struct kobj_attribute hpage_pmd_size_attr =
 304         __ATTR_RO(hpage_pmd_size);
 305
 306 #ifdef CONFIG_DEBUG_VM
 307 static ssize_t debug_cow_show(struct kobject *kobj,
 308                                 struct kobj_attribute *attr, char *buf)
 309 {
 310         return single_hugepage_flag_show(kobj, attr, buf,
 311                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 312 }
 313 static ssize_t debug_cow_store(struct kobject *kobj,
 314                                struct kobj_attribute *attr,
 315                                const char *buf, size_t count)
 316 {
 317         return single_hugepage_flag_store(kobj, attr, buf, count,
 318                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
 319 }
 320 static struct kobj_attribute debug_cow_attr =
 321         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
 322 #endif /* CONFIG_DEBUG_VM */
 323
 324 static struct attribute *hugepage_attr[] = {
 325         &enabled_attr.attr,
 326         &defrag_attr.attr,
 327         &use_zero_page_attr.attr,
 328         &hpage_pmd_size_attr.attr,
 329 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
 330         &shmem_enabled_attr.attr,
 331 #endif
 332 #ifdef CONFIG_DEBUG_VM
 333         &debug_cow_attr.attr,
 334 #endif
 335         NULL,
 336 };
 337
 338 static const struct attribute_group hugepage_attr_group = {
 339         .attrs = hugepage_attr,
 340 };
 341
 342 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
 343 {
 344         int err;
 345
 346         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
 347         if (unlikely(!*hugepage_kobj)) {
 348                 pr_err("failed to create transparent hugepage kobject\n");
 349                 return -ENOMEM;
 350         }
 351
 352         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
 353         if (err) {
 354                 pr_err("failed to register transparent hugepage group\n");
 355                 goto delete_obj;
 356         }
 357
 358         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
 359         if (err) {
 360                 pr_err("failed to register transparent hugepage group\n");
 361                 goto remove_hp_group;
 362         }
 363
 364         return 0;
 365
 366 remove_hp_group:
 367         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
 368 delete_obj:
 369         kobject_put(*hugepage_kobj);
 370         return err;
 371 }
 372
 373 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 374 {
 375         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
 376         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
 377         kobject_put(hugepage_kobj);
 378 }
 379 #else
 380 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
 381 {
 382         return 0;
 383 }
 384
 385 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 386 {
 387 }
 388 #endif /* CONFIG_SYSFS */
 389
 390 static int __init hugepage_init(void)
 391 {
 392         int err;
 393         struct kobject *hugepage_kobj;
 394
 395         if (!has_transparent_hugepage()) {
 396                 transparent_hugepage_flags = 0;
 397                 return -EINVAL;
 398         }
 399
 400         /*
 401          * hugepages can't be allocated by the buddy allocator
 402          */
 403         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
 404         /*
 405          * we use page->mapping and page->index in second tail page
 406          * as list_head: assuming THP order >= 2
 407          */
 408         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
 409
 410         err = hugepage_init_sysfs(&hugepage_kobj);
 411         if (err)
 412                 goto err_sysfs;
 413
 414         err = khugepaged_init();
 415         if (err)
 416                 goto err_slab;
 417
 418         err = register_shrinker(&huge_zero_page_shrinker);
 419         if (err)
 420                 goto err_hzp_shrinker;
 421         err = register_shrinker(&deferred_split_shrinker);
 422         if (err)
 423                 goto err_split_shrinker;
 424
 425         /*
 426          * By default disable transparent hugepages on smaller systems,
 427          * where the extra memory used could hurt more than TLB overhead
 428          * is likely to save.  The admin can still enable it through /sys.
 429          */
 430         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
 431                 transparent_hugepage_flags = 0;
 432                 return 0;
 433         }
 434
 435         err = start_stop_khugepaged();
 436         if (err)
 437                 goto err_khugepaged;
 438
 439         return 0;
 440 err_khugepaged:
 441         unregister_shrinker(&deferred_split_shrinker);
 442 err_split_shrinker:
 443         unregister_shrinker(&huge_zero_page_shrinker);
 444 err_hzp_shrinker:
 445         khugepaged_destroy();
 446 err_slab:
 447         hugepage_exit_sysfs(hugepage_kobj);
 448 err_sysfs:
 449         return err;
 450 }
 451 subsys_initcall(hugepage_init);
 452
 453 static int __init setup_transparent_hugepage(char *str)
 454 {
 455         int ret = 0;
 456         if (!str)
 457                 goto out;
 458         if (!strcmp(str, "always")) {
 459                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
 460                         &transparent_hugepage_flags);
 461                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 462                           &transparent_hugepage_flags);
 463                 ret = 1;
 464         } else if (!strcmp(str, "madvise")) {
 465                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 466                           &transparent_hugepage_flags);
 467                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 468                         &transparent_hugepage_flags);
 469                 ret = 1;
 470         } else if (!strcmp(str, "never")) {
 471                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
 472                           &transparent_hugepage_flags);
 473                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
 474                           &transparent_hugepage_flags);
 475                 ret = 1;
 476         }
 477 out:
 478         if (!ret)
 479                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
 480         return ret;
 481 }
 482 __setup("transparent_hugepage=", setup_transparent_hugepage);
 483
 484 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
 485 {
 486         if (likely(vma->vm_flags & VM_WRITE))
 487                 pmd = pmd_mkwrite(pmd);
 488         return pmd;
 489 }
 490
 491 #ifdef CONFIG_MEMCG
 492 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 493 {
 494         struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
 495         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 496
 497         if (memcg)
 498                 return &memcg->deferred_split_queue;
 499         else
 500                 return &pgdat->deferred_split_queue;
 501 }
 502 #else
 503 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
 504 {
 505         struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
 506
 507         return &pgdat->deferred_split_queue;
 508 }
 509 #endif
 510
 511 void prep_transhuge_page(struct page *page)
 512 {
 513         /*
 514          * we use page->mapping and page->indexlru in second tail page
 515          * as list_head: assuming THP order >= 2
 516          */
 517
 518         INIT_LIST_HEAD(page_deferred_list(page));
 519         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 520 }
 521
 522 bool is_transparent_hugepage(struct page *page)
 523 {
 524         if (!PageCompound(page))
 525                 return 0;
 526
 527         page = compound_head(page);
 528         return is_huge_zero_page(page) ||
 529                page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
 530 }
 531 EXPORT_SYMBOL_GPL(is_transparent_hugepage);
 532
 533 static unsigned long __thp_get_unmapped_area(struct file *filp,
 534                 unsigned long addr, unsigned long len,
 535                 loff_t off, unsigned long flags, unsigned long size)
 536 {
 537         loff_t off_end = off + len;
 538         loff_t off_align = round_up(off, size);
 539         unsigned long len_pad, ret;
 540
 541         if (off_end <= off_align || (off_end - off_align) < size)
 542                 return 0;
 543
 544         len_pad = len + size;
 545         if (len_pad < len || (off + len_pad) < off)
 546                 return 0;
 547
 548         ret = current->mm->get_unmapped_area(filp, addr, len_pad,
 549                                               off >> PAGE_SHIFT, flags);
 550
 551         /*
 552          * The failure might be due to length padding. The caller will retry
 553          * without the padding.
 554          */
 555         if (IS_ERR_VALUE(ret))
 556                 return 0;
 557
 558         /*
 559          * Do not try to align to THP boundary if allocation at the address
 560          * hint succeeds.
 561          */
 562         if (ret == addr)
 563                 return addr;
 564
 565         ret += (off - ret) & (size - 1);
 566         return ret;
 567 }
 568
 569 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
 570                 unsigned long len, unsigned long pgoff, unsigned long flags)
 571 {
 572         unsigned long ret;
 573         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
 574
 575         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
 576                 goto out;
 577
 578         ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
 579         if (ret)
 580                 return ret;
 581 out:
 582         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
 583 }
 584 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
 585
 586 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
 587                         struct page *page, gfp_t gfp)
 588 {
 589         struct vm_area_struct *vma = vmf->vma;
 590         struct mem_cgroup *memcg;
 591         pgtable_t pgtable;
 592         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 593         vm_fault_t ret = 0;
 594
 595         VM_BUG_ON_PAGE(!PageCompound(page), page);
 596
 597         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
 598                 put_page(page);
 599                 count_vm_event(THP_FAULT_FALLBACK);
 600                 return VM_FAULT_FALLBACK;
 601         }
 602
 603         pgtable = pte_alloc_one(vma->vm_mm);
 604         if (unlikely(!pgtable)) {
 605                 ret = VM_FAULT_OOM;
 606                 goto release;
 607         }
 608
 609         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 610         /*
 611          * The memory barrier inside __SetPageUptodate makes sure that
 612          * clear_huge_page writes become visible before the set_pmd_at()
 613          * write.
 614          */
 615         __SetPageUptodate(page);
 616
 617         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 618         if (unlikely(!pmd_none(*vmf->pmd))) {
 619                 goto unlock_release;
 620         } else {
 621                 pmd_t entry;
 622
 623                 ret = check_stable_address_space(vma->vm_mm);
 624                 if (ret)
 625                         goto unlock_release;
 626
 627                 /* Deliver the page fault to userland */
 628                 if (userfaultfd_missing(vma)) {
 629                         vm_fault_t ret2;
 630
 631                         spin_unlock(vmf->ptl);
 632                         mem_cgroup_cancel_charge(page, memcg, true);
 633                         put_page(page);
 634                         pte_free(vma->vm_mm, pgtable);
 635                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 636                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 637                         return ret2;
 638                 }
 639
 640                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 641                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 642                 page_add_new_anon_rmap(page, vma, haddr, true);
 643                 mem_cgroup_commit_charge(page, memcg, false, true);
 644                 lru_cache_add_active_or_unevictable(page, vma);
 645                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 646                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 647                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 648                 mm_inc_nr_ptes(vma->vm_mm);
 649                 spin_unlock(vmf->ptl);
 650                 count_vm_event(THP_FAULT_ALLOC);
 651                 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
 652         }
 653
 654         return 0;
 655 unlock_release:
 656         spin_unlock(vmf->ptl);
 657 release:
 658         if (pgtable)
 659                 pte_free(vma->vm_mm, pgtable);
 660         mem_cgroup_cancel_charge(page, memcg, true);
 661         put_page(page);
 662         return ret;
 663
 664 }
 665
 666 /*
 667  * always: directly stall for all thp allocations
 668  * defer: wake kswapd and fail if not immediately available
 669  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 670  *                fail if not immediately available
 671  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 672  *          available
 673  * never: never stall for any thp allocation
 674  */
 675 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 676 {
 677         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 678
 679         /* Always do synchronous compaction */
 680         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 681                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 682
 683         /* Kick kcompactd and fail quickly */
 684         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 685                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 686
 687         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 688         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 689                 return GFP_TRANSHUGE_LIGHT |
 690                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 691                                         __GFP_KSWAPD_RECLAIM);
 692
 693         /* Only do synchronous compaction if madvised */
 694         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 695                 return GFP_TRANSHUGE_LIGHT |
 696                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 697
 698         return GFP_TRANSHUGE_LIGHT;
 699 }
 700
 701 /* Caller must hold page table lock. */
 702 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 703                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 704                 struct page *zero_page)
 705 {
 706         pmd_t entry;
 707         if (!pmd_none(*pmd))
 708                 return false;
 709         entry = mk_pmd(zero_page, vma->vm_page_prot);
 710         entry = pmd_mkhuge(entry);
 711         if (pgtable)
 712                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 713         set_pmd_at(mm, haddr, pmd, entry);
 714         mm_inc_nr_ptes(mm);
 715         return true;
 716 }
 717
 718 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 719 {
 720         struct vm_area_struct *vma = vmf->vma;
 721         gfp_t gfp;
 722         struct page *page;
 723         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 724
 725         if (!transhuge_vma_suitable(vma, haddr))
 726                 return VM_FAULT_FALLBACK;
 727         if (unlikely(anon_vma_prepare(vma)))
 728                 return VM_FAULT_OOM;
 729         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 730                 return VM_FAULT_OOM;
 731         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 732                         !mm_forbids_zeropage(vma->vm_mm) &&
 733                         transparent_hugepage_use_zero_page()) {
 734                 pgtable_t pgtable;
 735                 struct page *zero_page;
 736                 bool set;
 737                 vm_fault_t ret;
 738                 pgtable = pte_alloc_one(vma->vm_mm);
 739                 if (unlikely(!pgtable))
 740                         return VM_FAULT_OOM;
 741                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 742                 if (unlikely(!zero_page)) {
 743                         pte_free(vma->vm_mm, pgtable);
 744                         count_vm_event(THP_FAULT_FALLBACK);
 745                         return VM_FAULT_FALLBACK;
 746                 }
 747                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 748                 ret = 0;
 749                 set = false;
 750                 if (pmd_none(*vmf->pmd)) {
 751                         ret = check_stable_address_space(vma->vm_mm);
 752                         if (ret) {
 753                                 spin_unlock(vmf->ptl);
 754                         } else if (userfaultfd_missing(vma)) {
 755                                 spin_unlock(vmf->ptl);
 756                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 757                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 758                         } else {
 759                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 760                                                    haddr, vmf->pmd, zero_page);
 761                                 spin_unlock(vmf->ptl);
 762                                 set = true;
 763                         }
 764                 } else
 765                         spin_unlock(vmf->ptl);
 766                 if (!set)
 767                         pte_free(vma->vm_mm, pgtable);
 768                 return ret;
 769         }
 770         gfp = alloc_hugepage_direct_gfpmask(vma);
 771         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 772         if (unlikely(!page)) {
 773                 count_vm_event(THP_FAULT_FALLBACK);
 774                 return VM_FAULT_FALLBACK;
 775         }
 776         prep_transhuge_page(page);
 777         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 778 }
 779
 780 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 781                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 782                 pgtable_t pgtable)
 783 {
 784         struct mm_struct *mm = vma->vm_mm;
 785         pmd_t entry;
 786         spinlock_t *ptl;
 787
 788         ptl = pmd_lock(mm, pmd);
 789         if (!pmd_none(*pmd)) {
 790                 if (write) {
 791                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
 792                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
 793                                 goto out_unlock;
 794                         }
 795                         entry = pmd_mkyoung(*pmd);
 796                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 797                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 798                                 update_mmu_cache_pmd(vma, addr, pmd);
 799                 }
 800
 801                 goto out_unlock;
 802         }
 803
 804         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 805         if (pfn_t_devmap(pfn))
 806                 entry = pmd_mkdevmap(entry);
 807         if (write) {
 808                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 809                 entry = maybe_pmd_mkwrite(entry, vma);
 810         }
 811
 812         if (pgtable) {
 813                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 814                 mm_inc_nr_ptes(mm);
 815                 pgtable = NULL;
 816         }
 817
 818         set_pmd_at(mm, addr, pmd, entry);
 819         update_mmu_cache_pmd(vma, addr, pmd);
 820
 821 out_unlock:
 822         spin_unlock(ptl);
 823         if (pgtable)
 824                 pte_free(mm, pgtable);
 825 }
 826
 827 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
 828 {
 829         unsigned long addr = vmf->address & PMD_MASK;
 830         struct vm_area_struct *vma = vmf->vma;
 831         pgprot_t pgprot = vma->vm_page_prot;
 832         pgtable_t pgtable = NULL;
 833
 834         /*
 835          * If we had pmd_special, we could avoid all these restrictions,
 836          * but we need to be consistent with PTEs and architectures that
 837          * can't support a 'special' bit.
 838          */
 839         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 840                         !pfn_t_devmap(pfn));
 841         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 842                                                 (VM_PFNMAP|VM_MIXEDMAP));
 843         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 844
 845         if (addr < vma->vm_start || addr >= vma->vm_end)
 846                 return VM_FAULT_SIGBUS;
 847
 848         if (arch_needs_pgtable_deposit()) {
 849                 pgtable = pte_alloc_one(vma->vm_mm);
 850                 if (!pgtable)
 851                         return VM_FAULT_OOM;
 852         }
 853
 854         track_pfn_insert(vma, &pgprot, pfn);
 855
 856         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
 857         return VM_FAULT_NOPAGE;
 858 }
 859 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 860
 861 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 862 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 863 {
 864         if (likely(vma->vm_flags & VM_WRITE))
 865                 pud = pud_mkwrite(pud);
 866         return pud;
 867 }
 868
 869 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 870                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 871 {
 872         struct mm_struct *mm = vma->vm_mm;
 873         pud_t entry;
 874         spinlock_t *ptl;
 875
 876         ptl = pud_lock(mm, pud);
 877         if (!pud_none(*pud)) {
 878                 if (write) {
 879                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
 880                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
 881                                 goto out_unlock;
 882                         }
 883                         entry = pud_mkyoung(*pud);
 884                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 885                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 886                                 update_mmu_cache_pud(vma, addr, pud);
 887                 }
 888                 goto out_unlock;
 889         }
 890
 891         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 892         if (pfn_t_devmap(pfn))
 893                 entry = pud_mkdevmap(entry);
 894         if (write) {
 895                 entry = pud_mkyoung(pud_mkdirty(entry));
 896                 entry = maybe_pud_mkwrite(entry, vma);
 897         }
 898         set_pud_at(mm, addr, pud, entry);
 899         update_mmu_cache_pud(vma, addr, pud);
 900
 901 out_unlock:
 902         spin_unlock(ptl);
 903 }
 904
 905 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
 906 {
 907         unsigned long addr = vmf->address & PUD_MASK;
 908         struct vm_area_struct *vma = vmf->vma;
 909         pgprot_t pgprot = vma->vm_page_prot;
 910
 911         /*
 912          * If we had pud_special, we could avoid all these restrictions,
 913          * but we need to be consistent with PTEs and architectures that
 914          * can't support a 'special' bit.
 915          */
 916         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 917                         !pfn_t_devmap(pfn));
 918         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 919                                                 (VM_PFNMAP|VM_MIXEDMAP));
 920         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 921
 922         if (addr < vma->vm_start || addr >= vma->vm_end)
 923                 return VM_FAULT_SIGBUS;
 924
 925         track_pfn_insert(vma, &pgprot, pfn);
 926
 927         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
 928         return VM_FAULT_NOPAGE;
 929 }
 930 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 931 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 932
 933 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 934                 pmd_t *pmd, int flags)
 935 {
 936         pmd_t _pmd;
 937
 938         _pmd = pmd_mkyoung(*pmd);
 939         if (flags & FOLL_WRITE)
 940                 _pmd = pmd_mkdirty(_pmd);
 941         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 942                                 pmd, _pmd, flags & FOLL_WRITE))
 943                 update_mmu_cache_pmd(vma, addr, pmd);
 944 }
 945
 946 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 947                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 948 {
 949         unsigned long pfn = pmd_pfn(*pmd);
 950         struct mm_struct *mm = vma->vm_mm;
 951         struct page *page;
 952
 953         assert_spin_locked(pmd_lockptr(mm, pmd));
 954
 955         /*
 956          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 957          * not be in this function with `flags & FOLL_COW` set.
 958          */
 959         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 960
 961         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 962                 return NULL;
 963
 964         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 965                 /* pass */;
 966         else
 967                 return NULL;
 968
 969         if (flags & FOLL_TOUCH)
 970                 touch_pmd(vma, addr, pmd, flags);
 971
 972         /*
 973          * device mapped pages can only be returned if the
 974          * caller will manage the page reference count.
 975          */
 976         if (!(flags & FOLL_GET))
 977                 return ERR_PTR(-EEXIST);
 978
 979         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
 980         *pgmap = get_dev_pagemap(pfn, *pgmap);
 981         if (!*pgmap)
 982                 return ERR_PTR(-EFAULT);
 983         page = pfn_to_page(pfn);
 984         get_page(page);
 985
 986         return page;
 987 }
 988
 989 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 990                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
 991                   struct vm_area_struct *vma)
 992 {
 993         spinlock_t *dst_ptl, *src_ptl;
 994         struct page *src_page;
 995         pmd_t pmd;
 996         pgtable_t pgtable = NULL;
 997         int ret = -ENOMEM;
 998
 999         /* Skip if can be re-fill on fault */
1000         if (!vma_is_anonymous(vma))
1001                 return 0;
1002
1003         pgtable = pte_alloc_one(dst_mm);
1004         if (unlikely(!pgtable))
1005                 goto out;
1006
1007         dst_ptl = pmd_lock(dst_mm, dst_pmd);
1008         src_ptl = pmd_lockptr(src_mm, src_pmd);
1009         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1010
1011         ret = -EAGAIN;
1012         pmd = *src_pmd;
1013
1014 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1015         if (unlikely(is_swap_pmd(pmd))) {
1016                 swp_entry_t entry = pmd_to_swp_entry(pmd);
1017
1018                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1019                 if (is_write_migration_entry(entry)) {
1020                         make_migration_entry_read(&entry);
1021                         pmd = swp_entry_to_pmd(entry);
1022                         if (pmd_swp_soft_dirty(*src_pmd))
1023                                 pmd = pmd_swp_mksoft_dirty(pmd);
1024                         set_pmd_at(src_mm, addr, src_pmd, pmd);
1025                 }
1026                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1027                 mm_inc_nr_ptes(dst_mm);
1028                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1029                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1030                 ret = 0;
1031                 goto out_unlock;
1032         }
1033 #endif
1034
1035         if (unlikely(!pmd_trans_huge(pmd))) {
1036                 pte_free(dst_mm, pgtable);
1037                 goto out_unlock;
1038         }
1039         /*
1040          * When page table lock is held, the huge zero pmd should not be
1041          * under splitting since we don't split the page itself, only pmd to
1042          * a page table.
1043          */
1044         if (is_huge_zero_pmd(pmd)) {
1045                 struct page *zero_page;
1046                 /*
1047                  * get_huge_zero_page() will never allocate a new page here,
1048                  * since we already have a zero page to copy. It just takes a
1049                  * reference.
1050                  */
1051                 zero_page = mm_get_huge_zero_page(dst_mm);
1052                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1053                                 zero_page);
1054                 ret = 0;
1055                 goto out_unlock;
1056         }
1057
1058         src_page = pmd_page(pmd);
1059         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1060         get_page(src_page);
1061         page_dup_rmap(src_page, true);
1062         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1063         mm_inc_nr_ptes(dst_mm);
1064         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1065
1066         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1067         pmd = pmd_mkold(pmd_wrprotect(pmd));
1068         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1069
1070         ret = 0;
1071 out_unlock:
1072         spin_unlock(src_ptl);
1073         spin_unlock(dst_ptl);
1074 out:
1075         return ret;
1076 }
1077
1078 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1079 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1080                 pud_t *pud, int flags)
1081 {
1082         pud_t _pud;
1083
1084         _pud = pud_mkyoung(*pud);
1085         if (flags & FOLL_WRITE)
1086                 _pud = pud_mkdirty(_pud);
1087         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1088                                 pud, _pud, flags & FOLL_WRITE))
1089                 update_mmu_cache_pud(vma, addr, pud);
1090 }
1091
1092 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1093                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1094 {
1095         unsigned long pfn = pud_pfn(*pud);
1096         struct mm_struct *mm = vma->vm_mm;
1097         struct page *page;
1098
1099         assert_spin_locked(pud_lockptr(mm, pud));
1100
1101         if (flags & FOLL_WRITE && !pud_write(*pud))
1102                 return NULL;
1103
1104         if (pud_present(*pud) && pud_devmap(*pud))
1105                 /* pass */;
1106         else
1107                 return NULL;
1108
1109         if (flags & FOLL_TOUCH)
1110                 touch_pud(vma, addr, pud, flags);
1111
1112         /*
1113          * device mapped pages can only be returned if the
1114          * caller will manage the page reference count.
1115          */
1116         if (!(flags & FOLL_GET))
1117                 return ERR_PTR(-EEXIST);
1118
1119         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1120         *pgmap = get_dev_pagemap(pfn, *pgmap);
1121         if (!*pgmap)
1122                 return ERR_PTR(-EFAULT);
1123         page = pfn_to_page(pfn);
1124         get_page(page);
1125
1126         return page;
1127 }
1128
1129 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1130                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1131                   struct vm_area_struct *vma)
1132 {
1133         spinlock_t *dst_ptl, *src_ptl;
1134         pud_t pud;
1135         int ret;
1136
1137         dst_ptl = pud_lock(dst_mm, dst_pud);
1138         src_ptl = pud_lockptr(src_mm, src_pud);
1139         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1140
1141         ret = -EAGAIN;
1142         pud = *src_pud;
1143         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1144                 goto out_unlock;
1145
1146         /*
1147          * When page table lock is held, the huge zero pud should not be
1148          * under splitting since we don't split the page itself, only pud to
1149          * a page table.
1150          */
1151         if (is_huge_zero_pud(pud)) {
1152                 /* No huge zero pud yet */
1153         }
1154
1155         pudp_set_wrprotect(src_mm, addr, src_pud);
1156         pud = pud_mkold(pud_wrprotect(pud));
1157         set_pud_at(dst_mm, addr, dst_pud, pud);
1158
1159         ret = 0;
1160 out_unlock:
1161         spin_unlock(src_ptl);
1162         spin_unlock(dst_ptl);
1163         return ret;
1164 }
1165
1166 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1167 {
1168         pud_t entry;
1169         unsigned long haddr;
1170         bool write = vmf->flags & FAULT_FLAG_WRITE;
1171
1172         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1173         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1174                 goto unlock;
1175
1176         entry = pud_mkyoung(orig_pud);
1177         if (write)
1178                 entry = pud_mkdirty(entry);
1179         haddr = vmf->address & HPAGE_PUD_MASK;
1180         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1181                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1182
1183 unlock:
1184         spin_unlock(vmf->ptl);
1185 }
1186 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1187
1188 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1189 {
1190         pmd_t entry;
1191         unsigned long haddr;
1192         bool write = vmf->flags & FAULT_FLAG_WRITE;
1193
1194         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1195         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1196                 goto unlock;
1197
1198         entry = pmd_mkyoung(orig_pmd);
1199         if (write)
1200                 entry = pmd_mkdirty(entry);
1201         haddr = vmf->address & HPAGE_PMD_MASK;
1202         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1203                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1204
1205 unlock:
1206         spin_unlock(vmf->ptl);
1207 }
1208
1209 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1210                         pmd_t orig_pmd, struct page *page)
1211 {
1212         struct vm_area_struct *vma = vmf->vma;
1213         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1214         struct mem_cgroup *memcg;
1215         pgtable_t pgtable;
1216         pmd_t _pmd;
1217         int i;
1218         vm_fault_t ret = 0;
1219         struct page **pages;
1220         struct mmu_notifier_range range;
1221
1222         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1223                               GFP_KERNEL);
1224         if (unlikely(!pages)) {
1225                 ret |= VM_FAULT_OOM;
1226                 goto out;
1227         }
1228
1229         for (i = 0; i < HPAGE_PMD_NR; i++) {
1230                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1231                                                vmf->address, page_to_nid(page));
1232                 if (unlikely(!pages[i] ||
1233                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1234                                      GFP_KERNEL, &memcg, false))) {
1235                         if (pages[i])
1236                                 put_page(pages[i]);
1237                         while (--i >= 0) {
1238                                 memcg = (void *)page_private(pages[i]);
1239                                 set_page_private(pages[i], 0);
1240                                 mem_cgroup_cancel_charge(pages[i], memcg,
1241                                                 false);
1242                                 put_page(pages[i]);
1243                         }
1244                         kfree(pages);
1245                         ret |= VM_FAULT_OOM;
1246                         goto out;
1247                 }
1248                 set_page_private(pages[i], (unsigned long)memcg);
1249         }
1250
1251         for (i = 0; i < HPAGE_PMD_NR; i++) {
1252                 copy_user_highpage(pages[i], page + i,
1253                                    haddr + PAGE_SIZE * i, vma);
1254                 __SetPageUptodate(pages[i]);
1255                 cond_resched();
1256         }
1257
1258         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1259                                 haddr, haddr + HPAGE_PMD_SIZE);
1260         mmu_notifier_invalidate_range_start(&range);
1261
1262         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1263         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1264                 goto out_free_pages;
1265         VM_BUG_ON_PAGE(!PageHead(page), page);
1266
1267         /*
1268          * Leave pmd empty until pte is filled note we must notify here as
1269          * concurrent CPU thread might write to new page before the call to
1270          * mmu_notifier_invalidate_range_end() happens which can lead to a
1271          * device seeing memory write in different order than CPU.
1272          *
1273          * See Documentation/vm/mmu_notifier.rst
1274          */
1275         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1276
1277         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1278         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1279
1280         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1281                 pte_t entry;
1282                 entry = mk_pte(pages[i], vma->vm_page_prot);
1283                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1284                 memcg = (void *)page_private(pages[i]);
1285                 set_page_private(pages[i], 0);
1286                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1287                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1288                 lru_cache_add_active_or_unevictable(pages[i], vma);
1289                 vmf->pte = pte_offset_map(&_pmd, haddr);
1290                 VM_BUG_ON(!pte_none(*vmf->pte));
1291                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1292                 pte_unmap(vmf->pte);
1293         }
1294         kfree(pages);
1295
1296         smp_wmb(); /* make pte visible before pmd */
1297         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1298         page_remove_rmap(page, true);
1299         spin_unlock(vmf->ptl);
1300
1301         /*
1302          * No need to double call mmu_notifier->invalidate_range() callback as
1303          * the above pmdp_huge_clear_flush_notify() did already call it.
1304          */
1305         mmu_notifier_invalidate_range_only_end(&range);
1306
1307         ret |= VM_FAULT_WRITE;
1308         put_page(page);
1309
1310 out:
1311         return ret;
1312
1313 out_free_pages:
1314         spin_unlock(vmf->ptl);
1315         mmu_notifier_invalidate_range_end(&range);
1316         for (i = 0; i < HPAGE_PMD_NR; i++) {
1317                 memcg = (void *)page_private(pages[i]);
1318                 set_page_private(pages[i], 0);
1319                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1320                 put_page(pages[i]);
1321         }
1322         kfree(pages);
1323         goto out;
1324 }
1325
1326 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1327 {
1328         struct vm_area_struct *vma = vmf->vma;
1329         struct page *page = NULL, *new_page;
1330         struct mem_cgroup *memcg;
1331         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1332         struct mmu_notifier_range range;
1333         gfp_t huge_gfp;                 /* for allocation and charge */
1334         vm_fault_t ret = 0;
1335
1336         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1337         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1338         if (is_huge_zero_pmd(orig_pmd))
1339                 goto alloc;
1340         spin_lock(vmf->ptl);
1341         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1342                 goto out_unlock;
1343
1344         page = pmd_page(orig_pmd);
1345         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1346         /*
1347          * We can only reuse the page if nobody else maps the huge page or it's
1348          * part.
1349          */
1350         if (!trylock_page(page)) {
1351                 get_page(page);
1352                 spin_unlock(vmf->ptl);
1353                 lock_page(page);
1354                 spin_lock(vmf->ptl);
1355                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1356                         unlock_page(page);
1357                         put_page(page);
1358                         goto out_unlock;
1359                 }
1360                 put_page(page);
1361         }
1362         if (reuse_swap_page(page, NULL)) {
1363                 pmd_t entry;
1364                 entry = pmd_mkyoung(orig_pmd);
1365                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1366                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1367                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1368                 ret |= VM_FAULT_WRITE;
1369                 unlock_page(page);
1370                 goto out_unlock;
1371         }
1372         unlock_page(page);
1373         get_page(page);
1374         spin_unlock(vmf->ptl);
1375 alloc:
1376         if (__transparent_hugepage_enabled(vma) &&
1377             !transparent_hugepage_debug_cow()) {
1378                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1379                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1380         } else
1381                 new_page = NULL;
1382
1383         if (likely(new_page)) {
1384                 prep_transhuge_page(new_page);
1385         } else {
1386                 if (!page) {
1387                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1388                         ret |= VM_FAULT_FALLBACK;
1389                 } else {
1390                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1391                         if (ret & VM_FAULT_OOM) {
1392                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1393                                 ret |= VM_FAULT_FALLBACK;
1394                         }
1395                         put_page(page);
1396                 }
1397                 count_vm_event(THP_FAULT_FALLBACK);
1398                 goto out;
1399         }
1400
1401         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1402                                         huge_gfp, &memcg, true))) {
1403                 put_page(new_page);
1404                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1405                 if (page)
1406                         put_page(page);
1407                 ret |= VM_FAULT_FALLBACK;
1408                 count_vm_event(THP_FAULT_FALLBACK);
1409                 goto out;
1410         }
1411
1412         count_vm_event(THP_FAULT_ALLOC);
1413         count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1414
1415         if (!page)
1416                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1417         else
1418                 copy_user_huge_page(new_page, page, vmf->address,
1419                                     vma, HPAGE_PMD_NR);
1420         __SetPageUptodate(new_page);
1421
1422         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1423                                 haddr, haddr + HPAGE_PMD_SIZE);
1424         mmu_notifier_invalidate_range_start(&range);
1425
1426         spin_lock(vmf->ptl);
1427         if (page)
1428                 put_page(page);
1429         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1430                 spin_unlock(vmf->ptl);
1431                 mem_cgroup_cancel_charge(new_page, memcg, true);
1432                 put_page(new_page);
1433                 goto out_mn;
1434         } else {
1435                 pmd_t entry;
1436                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1437                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1438                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1439                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1440                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1441                 lru_cache_add_active_or_unevictable(new_page, vma);
1442                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1443                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1444                 if (!page) {
1445                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1446                 } else {
1447                         VM_BUG_ON_PAGE(!PageHead(page), page);
1448                         page_remove_rmap(page, true);
1449                         put_page(page);
1450                 }
1451                 ret |= VM_FAULT_WRITE;
1452         }
1453         spin_unlock(vmf->ptl);
1454 out_mn:
1455         /*
1456          * No need to double call mmu_notifier->invalidate_range() callback as
1457          * the above pmdp_huge_clear_flush_notify() did already call it.
1458          */
1459         mmu_notifier_invalidate_range_only_end(&range);
1460 out:
1461         return ret;
1462 out_unlock:
1463         spin_unlock(vmf->ptl);
1464         return ret;
1465 }
1466
1467 /*
1468  * FOLL_FORCE can write to even unwritable pmd's, but only
1469  * after we've gone through a COW cycle and they are dirty.
1470  */
1471 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1472 {
1473         return pmd_write(pmd) ||
1474                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1475 }
1476
1477 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1478                                    unsigned long addr,
1479                                    pmd_t *pmd,
1480                                    unsigned int flags)
1481 {
1482         struct mm_struct *mm = vma->vm_mm;
1483         struct page *page = NULL;
1484
1485         assert_spin_locked(pmd_lockptr(mm, pmd));
1486
1487         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1488                 goto out;
1489
1490         /* Avoid dumping huge zero page */
1491         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1492                 return ERR_PTR(-EFAULT);
1493
1494         /* Full NUMA hinting faults to serialise migration in fault paths */
1495         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1496                 goto out;
1497
1498         page = pmd_page(*pmd);
1499         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1500         if (flags & FOLL_TOUCH)
1501                 touch_pmd(vma, addr, pmd, flags);
1502         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1503                 /*
1504                  * We don't mlock() pte-mapped THPs. This way we can avoid
1505                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1506                  *
1507                  * For anon THP:
1508                  *
1509                  * In most cases the pmd is the only mapping of the page as we
1510                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1511                  * writable private mappings in populate_vma_page_range().
1512                  *
1513                  * The only scenario when we have the page shared here is if we
1514                  * mlocking read-only mapping shared over fork(). We skip
1515                  * mlocking such pages.
1516                  *
1517                  * For file THP:
1518                  *
1519                  * We can expect PageDoubleMap() to be stable under page lock:
1520                  * for file pages we set it in page_add_file_rmap(), which
1521                  * requires page to be locked.
1522                  */
1523
1524                 if (PageAnon(page) && compound_mapcount(page) != 1)
1525                         goto skip_mlock;
1526                 if (PageDoubleMap(page) || !page->mapping)
1527                         goto skip_mlock;
1528                 if (!trylock_page(page))
1529                         goto skip_mlock;
1530                 lru_add_drain();
1531                 if (page->mapping && !PageDoubleMap(page))
1532                         mlock_vma_page(page);
1533                 unlock_page(page);
1534         }
1535 skip_mlock:
1536         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1537         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1538         if (flags & FOLL_GET)
1539                 get_page(page);
1540
1541 out:
1542         return page;
1543 }
1544
1545 /* NUMA hinting page fault entry point for trans huge pmds */
1546 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1547 {
1548         struct vm_area_struct *vma = vmf->vma;
1549         struct anon_vma *anon_vma = NULL;
1550         struct page *page;
1551         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1552         int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1553         int target_nid, last_cpupid = -1;
1554         bool page_locked;
1555         bool migrated = false;
1556         bool was_writable;
1557         int flags = 0;
1558
1559         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1560         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1561                 goto out_unlock;
1562
1563         /*
1564          * If there are potential migrations, wait for completion and retry
1565          * without disrupting NUMA hinting information. Do not relock and
1566          * check_same as the page may no longer be mapped.
1567          */
1568         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1569                 page = pmd_page(*vmf->pmd);
1570                 if (!get_page_unless_zero(page))
1571                         goto out_unlock;
1572                 spin_unlock(vmf->ptl);
1573                 put_and_wait_on_page_locked(page);
1574                 goto out;
1575         }
1576
1577         page = pmd_page(pmd);
1578         BUG_ON(is_huge_zero_page(page));
1579         page_nid = page_to_nid(page);
1580         last_cpupid = page_cpupid_last(page);
1581         count_vm_numa_event(NUMA_HINT_FAULTS);
1582         if (page_nid == this_nid) {
1583                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1584                 flags |= TNF_FAULT_LOCAL;
1585         }
1586
1587         /* See similar comment in do_numa_page for explanation */
1588         if (!pmd_savedwrite(pmd))
1589                 flags |= TNF_NO_GROUP;
1590
1591         /*
1592          * Acquire the page lock to serialise THP migrations but avoid dropping
1593          * page_table_lock if at all possible
1594          */
1595         page_locked = trylock_page(page);
1596         target_nid = mpol_misplaced(page, vma, haddr);
1597         if (target_nid == NUMA_NO_NODE) {
1598                 /* If the page was locked, there are no parallel migrations */
1599                 if (page_locked)
1600                         goto clear_pmdnuma;
1601         }
1602
1603         /* Migration could have started since the pmd_trans_migrating check */
1604         if (!page_locked) {
1605                 page_nid = NUMA_NO_NODE;
1606                 if (!get_page_unless_zero(page))
1607                         goto out_unlock;
1608                 spin_unlock(vmf->ptl);
1609                 put_and_wait_on_page_locked(page);
1610                 goto out;
1611         }
1612
1613         /*
1614          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1615          * to serialises splits
1616          */
1617         get_page(page);
1618         spin_unlock(vmf->ptl);
1619         anon_vma = page_lock_anon_vma_read(page);
1620
1621         /* Confirm the PMD did not change while page_table_lock was released */
1622         spin_lock(vmf->ptl);
1623         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1624                 unlock_page(page);
1625                 put_page(page);
1626                 page_nid = NUMA_NO_NODE;
1627                 goto out_unlock;
1628         }
1629
1630         /* Bail if we fail to protect against THP splits for any reason */
1631         if (unlikely(!anon_vma)) {
1632                 put_page(page);
1633                 page_nid = NUMA_NO_NODE;
1634                 goto clear_pmdnuma;
1635         }
1636
1637         /*
1638          * Since we took the NUMA fault, we must have observed the !accessible
1639          * bit. Make sure all other CPUs agree with that, to avoid them
1640          * modifying the page we're about to migrate.
1641          *
1642          * Must be done under PTL such that we'll observe the relevant
1643          * inc_tlb_flush_pending().
1644          *
1645          * We are not sure a pending tlb flush here is for a huge page
1646          * mapping or not. Hence use the tlb range variant
1647          */
1648         if (mm_tlb_flush_pending(vma->vm_mm)) {
1649                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1650                 /*
1651                  * change_huge_pmd() released the pmd lock before
1652                  * invalidating the secondary MMUs sharing the primary
1653                  * MMU pagetables (with ->invalidate_range()). The
1654                  * mmu_notifier_invalidate_range_end() (which
1655                  * internally calls ->invalidate_range()) in
1656                  * change_pmd_range() will run after us, so we can't
1657                  * rely on it here and we need an explicit invalidate.
1658                  */
1659                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1660                                               haddr + HPAGE_PMD_SIZE);
1661         }
1662
1663         /*
1664          * Migrate the THP to the requested node, returns with page unlocked
1665          * and access rights restored.
1666          */
1667         spin_unlock(vmf->ptl);
1668
1669         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1670                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1671         if (migrated) {
1672                 flags |= TNF_MIGRATED;
1673                 page_nid = target_nid;
1674         } else
1675                 flags |= TNF_MIGRATE_FAIL;
1676
1677         goto out;
1678 clear_pmdnuma:
1679         BUG_ON(!PageLocked(page));
1680         was_writable = pmd_savedwrite(pmd);
1681         pmd = pmd_modify(pmd, vma->vm_page_prot);
1682         pmd = pmd_mkyoung(pmd);
1683         if (was_writable)
1684                 pmd = pmd_mkwrite(pmd);
1685         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1686         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1687         unlock_page(page);
1688 out_unlock:
1689         spin_unlock(vmf->ptl);
1690
1691 out:
1692         if (anon_vma)
1693                 page_unlock_anon_vma_read(anon_vma);
1694
1695         if (page_nid != NUMA_NO_NODE)
1696                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1697                                 flags);
1698
1699         return 0;
1700 }
1701
1702 /*
1703  * Return true if we do MADV_FREE successfully on entire pmd page.
1704  * Otherwise, return false.
1705  */
1706 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1707                 pmd_t *pmd, unsigned long addr, unsigned long next)
1708 {
1709         spinlock_t *ptl;
1710         pmd_t orig_pmd;
1711         struct page *page;
1712         struct mm_struct *mm = tlb->mm;
1713         bool ret = false;
1714
1715         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1716
1717         ptl = pmd_trans_huge_lock(pmd, vma);
1718         if (!ptl)
1719                 goto out_unlocked;
1720
1721         orig_pmd = *pmd;
1722         if (is_huge_zero_pmd(orig_pmd))
1723                 goto out;
1724
1725         if (unlikely(!pmd_present(orig_pmd))) {
1726                 VM_BUG_ON(thp_migration_supported() &&
1727                                   !is_pmd_migration_entry(orig_pmd));
1728                 goto out;
1729         }
1730
1731         page = pmd_page(orig_pmd);
1732         /*
1733          * If other processes are mapping this page, we couldn't discard
1734          * the page unless they all do MADV_FREE so let's skip the page.
1735          */
1736         if (page_mapcount(page) != 1)
1737                 goto out;
1738
1739         if (!trylock_page(page))
1740                 goto out;
1741
1742         /*
1743          * If user want to discard part-pages of THP, split it so MADV_FREE
1744          * will deactivate only them.
1745          */
1746         if (next - addr != HPAGE_PMD_SIZE) {
1747                 get_page(page);
1748                 spin_unlock(ptl);
1749                 split_huge_page(page);
1750                 unlock_page(page);
1751                 put_page(page);
1752                 goto out_unlocked;
1753         }
1754
1755         if (PageDirty(page))
1756                 ClearPageDirty(page);
1757         unlock_page(page);
1758
1759         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1760                 pmdp_invalidate(vma, addr, pmd);
1761                 orig_pmd = pmd_mkold(orig_pmd);
1762                 orig_pmd = pmd_mkclean(orig_pmd);
1763
1764                 set_pmd_at(mm, addr, pmd, orig_pmd);
1765                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1766         }
1767
1768         mark_page_lazyfree(page);
1769         ret = true;
1770 out:
1771         spin_unlock(ptl);
1772 out_unlocked:
1773         return ret;
1774 }
1775
1776 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1777 {
1778         pgtable_t pgtable;
1779
1780         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1781         pte_free(mm, pgtable);
1782         mm_dec_nr_ptes(mm);
1783 }
1784
1785 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1786                  pmd_t *pmd, unsigned long addr)
1787 {
1788         pmd_t orig_pmd;
1789         spinlock_t *ptl;
1790
1791         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1792
1793         ptl = __pmd_trans_huge_lock(pmd, vma);
1794         if (!ptl)
1795                 return 0;
1796         /*
1797          * For architectures like ppc64 we look at deposited pgtable
1798          * when calling pmdp_huge_get_and_clear. So do the
1799          * pgtable_trans_huge_withdraw after finishing pmdp related
1800          * operations.
1801          */
1802         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1803                         tlb->fullmm);
1804         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1805         if (vma_is_dax(vma)) {
1806                 if (arch_needs_pgtable_deposit())
1807                         zap_deposited_table(tlb->mm, pmd);
1808                 spin_unlock(ptl);
1809                 if (is_huge_zero_pmd(orig_pmd))
1810                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1811         } else if (is_huge_zero_pmd(orig_pmd)) {
1812                 zap_deposited_table(tlb->mm, pmd);
1813                 spin_unlock(ptl);
1814                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1815         } else {
1816                 struct page *page = NULL;
1817                 int flush_needed = 1;
1818
1819                 if (pmd_present(orig_pmd)) {
1820                         page = pmd_page(orig_pmd);
1821                         page_remove_rmap(page, true);
1822                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1823                         VM_BUG_ON_PAGE(!PageHead(page), page);
1824                 } else if (thp_migration_supported()) {
1825                         swp_entry_t entry;
1826
1827                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1828                         entry = pmd_to_swp_entry(orig_pmd);
1829                         page = pfn_to_page(swp_offset(entry));
1830                         flush_needed = 0;
1831                 } else
1832                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1833
1834                 if (PageAnon(page)) {
1835                         zap_deposited_table(tlb->mm, pmd);
1836                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1837                 } else {
1838                         if (arch_needs_pgtable_deposit())
1839                                 zap_deposited_table(tlb->mm, pmd);
1840                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1841                 }
1842
1843                 spin_unlock(ptl);
1844                 if (flush_needed)
1845                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1846         }
1847         return 1;
1848 }
1849
1850 #ifndef pmd_move_must_withdraw
1851 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1852                                          spinlock_t *old_pmd_ptl,
1853                                          struct vm_area_struct *vma)
1854 {
1855         /*
1856          * With split pmd lock we also need to move preallocated
1857          * PTE page table if new_pmd is on different PMD page table.
1858          *
1859          * We also don't deposit and withdraw tables for file pages.
1860          */
1861         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1862 }
1863 #endif
1864
1865 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1866 {
1867 #ifdef CONFIG_MEM_SOFT_DIRTY
1868         if (unlikely(is_pmd_migration_entry(pmd)))
1869                 pmd = pmd_swp_mksoft_dirty(pmd);
1870         else if (pmd_present(pmd))
1871                 pmd = pmd_mksoft_dirty(pmd);
1872 #endif
1873         return pmd;
1874 }
1875
1876 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1877                   unsigned long new_addr, unsigned long old_end,
1878                   pmd_t *old_pmd, pmd_t *new_pmd)
1879 {
1880         spinlock_t *old_ptl, *new_ptl;
1881         pmd_t pmd;
1882         struct mm_struct *mm = vma->vm_mm;
1883         bool force_flush = false;
1884
1885         if ((old_addr & ~HPAGE_PMD_MASK) ||
1886             (new_addr & ~HPAGE_PMD_MASK) ||
1887             old_end - old_addr < HPAGE_PMD_SIZE)
1888                 return false;
1889
1890         /*
1891          * The destination pmd shouldn't be established, free_pgtables()
1892          * should have release it.
1893          */
1894         if (WARN_ON(!pmd_none(*new_pmd))) {
1895                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1896                 return false;
1897         }
1898
1899         /*
1900          * We don't have to worry about the ordering of src and dst
1901          * ptlocks because exclusive mmap_sem prevents deadlock.
1902          */
1903         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1904         if (old_ptl) {
1905                 new_ptl = pmd_lockptr(mm, new_pmd);
1906                 if (new_ptl != old_ptl)
1907                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1908                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1909                 if (pmd_present(pmd))
1910                         force_flush = true;
1911                 VM_BUG_ON(!pmd_none(*new_pmd));
1912
1913                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1914                         pgtable_t pgtable;
1915                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1916                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1917                 }
1918                 pmd = move_soft_dirty_pmd(pmd);
1919                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1920                 if (force_flush)
1921                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1922                 if (new_ptl != old_ptl)
1923                         spin_unlock(new_ptl);
1924                 spin_unlock(old_ptl);
1925                 return true;
1926         }
1927         return false;
1928 }
1929
1930 /*
1931  * Returns
1932  *  - 0 if PMD could not be locked
1933  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1934  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1935  */
1936 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1937                 unsigned long addr, pgprot_t newprot, int prot_numa)
1938 {
1939         struct mm_struct *mm = vma->vm_mm;
1940         spinlock_t *ptl;
1941         pmd_t entry;
1942         bool preserve_write;
1943         int ret;
1944
1945         ptl = __pmd_trans_huge_lock(pmd, vma);
1946         if (!ptl)
1947                 return 0;
1948
1949         preserve_write = prot_numa && pmd_write(*pmd);
1950         ret = 1;
1951
1952 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1953         if (is_swap_pmd(*pmd)) {
1954                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1955
1956                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1957                 if (is_write_migration_entry(entry)) {
1958                         pmd_t newpmd;
1959                         /*
1960                          * A protection check is difficult so
1961                          * just be safe and disable write
1962                          */
1963                         make_migration_entry_read(&entry);
1964                         newpmd = swp_entry_to_pmd(entry);
1965                         if (pmd_swp_soft_dirty(*pmd))
1966                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1967                         set_pmd_at(mm, addr, pmd, newpmd);
1968                 }
1969                 goto unlock;
1970         }
1971 #endif
1972
1973         /*
1974          * Avoid trapping faults against the zero page. The read-only
1975          * data is likely to be read-cached on the local CPU and
1976          * local/remote hits to the zero page are not interesting.
1977          */
1978         if (prot_numa && is_huge_zero_pmd(*pmd))
1979                 goto unlock;
1980
1981         if (prot_numa && pmd_protnone(*pmd))
1982                 goto unlock;
1983
1984         /*
1985          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1986          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1987          * which is also under down_read(mmap_sem):
1988          *
1989          *      CPU0:                           CPU1:
1990          *                              change_huge_pmd(prot_numa=1)
1991          *                               pmdp_huge_get_and_clear_notify()
1992          * madvise_dontneed()
1993          *  zap_pmd_range()
1994          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1995          *   // skip the pmd
1996          *                               set_pmd_at();
1997          *                               // pmd is re-established
1998          *
1999          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
2000          * which may break userspace.
2001          *
2002          * pmdp_invalidate() is required to make sure we don't miss
2003          * dirty/young flags set by hardware.
2004          */
2005         entry = pmdp_invalidate(vma, addr, pmd);
2006
2007         entry = pmd_modify(entry, newprot);
2008         if (preserve_write)
2009                 entry = pmd_mk_savedwrite(entry);
2010         ret = HPAGE_PMD_NR;
2011         set_pmd_at(mm, addr, pmd, entry);
2012         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
2013 unlock:
2014         spin_unlock(ptl);
2015         return ret;
2016 }
2017
2018 /*
2019  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
2020  *
2021  * Note that if it returns page table lock pointer, this routine returns without
2022  * unlocking page table lock. So callers must unlock it.
2023  */
2024 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
2025 {
2026         spinlock_t *ptl;
2027         ptl = pmd_lock(vma->vm_mm, pmd);
2028         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2029                         pmd_devmap(*pmd)))
2030                 return ptl;
2031         spin_unlock(ptl);
2032         return NULL;
2033 }
2034
2035 /*
2036  * Returns true if a given pud maps a thp, false otherwise.
2037  *
2038  * Note that if it returns true, this routine returns without unlocking page
2039  * table lock. So callers must unlock it.
2040  */
2041 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2042 {
2043         spinlock_t *ptl;
2044
2045         ptl = pud_lock(vma->vm_mm, pud);
2046         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2047                 return ptl;
2048         spin_unlock(ptl);
2049         return NULL;
2050 }
2051
2052 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2053 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2054                  pud_t *pud, unsigned long addr)
2055 {
2056         spinlock_t *ptl;
2057
2058         ptl = __pud_trans_huge_lock(pud, vma);
2059         if (!ptl)
2060                 return 0;
2061         /*
2062          * For architectures like ppc64 we look at deposited pgtable
2063          * when calling pudp_huge_get_and_clear. So do the
2064          * pgtable_trans_huge_withdraw after finishing pudp related
2065          * operations.
2066          */
2067         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2068         tlb_remove_pud_tlb_entry(tlb, pud, addr);
2069         if (vma_is_dax(vma)) {
2070                 spin_unlock(ptl);
2071                 /* No zero page support yet */
2072         } else {
2073                 /* No support for anonymous PUD pages yet */
2074                 BUG();
2075         }
2076         return 1;
2077 }
2078
2079 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2080                 unsigned long haddr)
2081 {
2082         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2083         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2084         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2085         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2086
2087         count_vm_event(THP_SPLIT_PUD);
2088
2089         pudp_huge_clear_flush_notify(vma, haddr, pud);
2090 }
2091
2092 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2093                 unsigned long address)
2094 {
2095         spinlock_t *ptl;
2096         struct mmu_notifier_range range;
2097
2098         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2099                                 address & HPAGE_PUD_MASK,
2100                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2101         mmu_notifier_invalidate_range_start(&range);
2102         ptl = pud_lock(vma->vm_mm, pud);
2103         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2104                 goto out;
2105         __split_huge_pud_locked(vma, pud, range.start);
2106
2107 out:
2108         spin_unlock(ptl);
2109         /*
2110          * No need to double call mmu_notifier->invalidate_range() callback as
2111          * the above pudp_huge_clear_flush_notify() did already call it.
2112          */
2113         mmu_notifier_invalidate_range_only_end(&range);
2114 }
2115 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2116
2117 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2118                 unsigned long haddr, pmd_t *pmd)
2119 {
2120         struct mm_struct *mm = vma->vm_mm;
2121         pgtable_t pgtable;
2122         pmd_t _pmd;
2123         int i;
2124
2125         /*
2126          * Leave pmd empty until pte is filled note that it is fine to delay
2127          * notification until mmu_notifier_invalidate_range_end() as we are
2128          * replacing a zero pmd write protected page with a zero pte write
2129          * protected page.
2130          *
2131          * See Documentation/vm/mmu_notifier.rst
2132          */
2133         pmdp_huge_clear_flush(vma, haddr, pmd);
2134
2135         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2136         pmd_populate(mm, &_pmd, pgtable);
2137
2138         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2139                 pte_t *pte, entry;
2140                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2141                 entry = pte_mkspecial(entry);
2142                 pte = pte_offset_map(&_pmd, haddr);
2143                 VM_BUG_ON(!pte_none(*pte));
2144                 set_pte_at(mm, haddr, pte, entry);
2145                 pte_unmap(pte);
2146         }
2147         smp_wmb(); /* make pte visible before pmd */
2148         pmd_populate(mm, pmd, pgtable);
2149 }
2150
2151 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2152                 unsigned long haddr, bool freeze)
2153 {
2154         struct mm_struct *mm = vma->vm_mm;
2155         struct page *page;
2156         pgtable_t pgtable;
2157         pmd_t old_pmd, _pmd;
2158         bool young, write, soft_dirty, pmd_migration = false;
2159         unsigned long addr;
2160         int i;
2161
2162         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2163         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2164         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2165         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2166                                 && !pmd_devmap(*pmd));
2167
2168         count_vm_event(THP_SPLIT_PMD);
2169
2170         if (!vma_is_anonymous(vma)) {
2171                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2172                 /*
2173                  * We are going to unmap this huge page. So
2174                  * just go ahead and zap it
2175                  */
2176                 if (arch_needs_pgtable_deposit())
2177                         zap_deposited_table(mm, pmd);
2178                 if (vma_is_dax(vma))
2179                         return;
2180                 page = pmd_page(_pmd);
2181                 if (!PageDirty(page) && pmd_dirty(_pmd))
2182                         set_page_dirty(page);
2183                 if (!PageReferenced(page) && pmd_young(_pmd))
2184                         SetPageReferenced(page);
2185                 page_remove_rmap(page, true);
2186                 put_page(page);
2187                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2188                 return;
2189         } else if (is_huge_zero_pmd(*pmd)) {
2190                 /*
2191                  * FIXME: Do we want to invalidate secondary mmu by calling
2192                  * mmu_notifier_invalidate_range() see comments below inside
2193                  * __split_huge_pmd() ?
2194                  *
2195                  * We are going from a zero huge page write protected to zero
2196                  * small page also write protected so it does not seems useful
2197                  * to invalidate secondary mmu at this time.
2198                  */
2199                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2200         }
2201
2202         /*
2203          * Up to this point the pmd is present and huge and userland has the
2204          * whole access to the hugepage during the split (which happens in
2205          * place). If we overwrite the pmd with the not-huge version pointing
2206          * to the pte here (which of course we could if all CPUs were bug
2207          * free), userland could trigger a small page size TLB miss on the
2208          * small sized TLB while the hugepage TLB entry is still established in
2209          * the huge TLB. Some CPU doesn't like that.
2210          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2211          * 383 on page 93. Intel should be safe but is also warns that it's
2212          * only safe if the permission and cache attributes of the two entries
2213          * loaded in the two TLB is identical (which should be the case here).
2214          * But it is generally safer to never allow small and huge TLB entries
2215          * for the same virtual address to be loaded simultaneously. So instead
2216          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2217          * current pmd notpresent (atomically because here the pmd_trans_huge
2218          * must remain set at all times on the pmd until the split is complete
2219          * for this pmd), then we flush the SMP TLB and finally we write the
2220          * non-huge version of the pmd entry with pmd_populate.
2221          */
2222         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2223
2224         pmd_migration = is_pmd_migration_entry(old_pmd);
2225         if (unlikely(pmd_migration)) {
2226                 swp_entry_t entry;
2227
2228                 entry = pmd_to_swp_entry(old_pmd);
2229                 page = pfn_to_page(swp_offset(entry));
2230                 write = is_write_migration_entry(entry);
2231                 young = false;
2232                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2233         } else {
2234                 page = pmd_page(old_pmd);
2235                 if (pmd_dirty(old_pmd))
2236                         SetPageDirty(page);
2237                 write = pmd_write(old_pmd);
2238                 young = pmd_young(old_pmd);
2239                 soft_dirty = pmd_soft_dirty(old_pmd);
2240         }
2241         VM_BUG_ON_PAGE(!page_count(page), page);
2242         page_ref_add(page, HPAGE_PMD_NR - 1);
2243
2244         /*
2245          * Withdraw the table only after we mark the pmd entry invalid.
2246          * This's critical for some architectures (Power).
2247          */
2248         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2249         pmd_populate(mm, &_pmd, pgtable);
2250
2251         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2252                 pte_t entry, *pte;
2253                 /*
2254                  * Note that NUMA hinting access restrictions are not
2255                  * transferred to avoid any possibility of altering
2256                  * permissions across VMAs.
2257                  */
2258                 if (freeze || pmd_migration) {
2259                         swp_entry_t swp_entry;
2260                         swp_entry = make_migration_entry(page + i, write);
2261                         entry = swp_entry_to_pte(swp_entry);
2262                         if (soft_dirty)
2263                                 entry = pte_swp_mksoft_dirty(entry);
2264                 } else {
2265                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2266                         entry = maybe_mkwrite(entry, vma);
2267                         if (!write)
2268                                 entry = pte_wrprotect(entry);
2269                         if (!young)
2270                                 entry = pte_mkold(entry);
2271                         if (soft_dirty)
2272                                 entry = pte_mksoft_dirty(entry);
2273                 }
2274                 pte = pte_offset_map(&_pmd, addr);
2275                 BUG_ON(!pte_none(*pte));
2276                 set_pte_at(mm, addr, pte, entry);
2277                 atomic_inc(&page[i]._mapcount);
2278                 pte_unmap(pte);
2279         }
2280
2281         /*
2282          * Set PG_double_map before dropping compound_mapcount to avoid
2283          * false-negative page_mapped().
2284          */
2285         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2286                 for (i = 0; i < HPAGE_PMD_NR; i++)
2287                         atomic_inc(&page[i]._mapcount);
2288         }
2289
2290         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2291                 /* Last compound_mapcount is gone. */
2292                 __dec_node_page_state(page, NR_ANON_THPS);
2293                 if (TestClearPageDoubleMap(page)) {
2294                         /* No need in mapcount reference anymore */
2295                         for (i = 0; i < HPAGE_PMD_NR; i++)
2296                                 atomic_dec(&page[i]._mapcount);
2297                 }
2298         }
2299
2300         smp_wmb(); /* make pte visible before pmd */
2301         pmd_populate(mm, pmd, pgtable);
2302
2303         if (freeze) {
2304                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2305                         page_remove_rmap(page + i, false);
2306                         put_page(page + i);
2307                 }
2308         }
2309 }
2310
2311 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2312                 unsigned long address, bool freeze, struct page *page)
2313 {
2314         spinlock_t *ptl;
2315         struct mmu_notifier_range range;
2316
2317         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2318                                 address & HPAGE_PMD_MASK,
2319                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2320         mmu_notifier_invalidate_range_start(&range);
2321         ptl = pmd_lock(vma->vm_mm, pmd);
2322
2323         /*
2324          * If caller asks to setup a migration entries, we need a page to check
2325          * pmd against. Otherwise we can end up replacing wrong page.
2326          */
2327         VM_BUG_ON(freeze && !page);
2328         if (page && page != pmd_page(*pmd))
2329                 goto out;
2330
2331         if (pmd_trans_huge(*pmd)) {
2332                 page = pmd_page(*pmd);
2333                 if (PageMlocked(page))
2334                         clear_page_mlock(page);
2335         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2336                 goto out;
2337         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2338 out:
2339         spin_unlock(ptl);
2340         /*
2341          * No need to double call mmu_notifier->invalidate_range() callback.
2342          * They are 3 cases to consider inside __split_huge_pmd_locked():
2343          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2344          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2345          *    fault will trigger a flush_notify before pointing to a new page
2346          *    (it is fine if the secondary mmu keeps pointing to the old zero
2347          *    page in the meantime)
2348          *  3) Split a huge pmd into pte pointing to the same page. No need
2349          *     to invalidate secondary tlb entry they are all still valid.
2350          *     any further changes to individual pte will notify. So no need
2351          *     to call mmu_notifier->invalidate_range()
2352          */
2353         mmu_notifier_invalidate_range_only_end(&range);
2354 }
2355
2356 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2357                 bool freeze, struct page *page)
2358 {
2359         pgd_t *pgd;
2360         p4d_t *p4d;
2361         pud_t *pud;
2362         pmd_t *pmd;
2363
2364         pgd = pgd_offset(vma->vm_mm, address);
2365         if (!pgd_present(*pgd))
2366                 return;
2367
2368         p4d = p4d_offset(pgd, address);
2369         if (!p4d_present(*p4d))
2370                 return;
2371
2372         pud = pud_offset(p4d, address);
2373         if (!pud_present(*pud))
2374                 return;
2375
2376         pmd = pmd_offset(pud, address);
2377
2378         __split_huge_pmd(vma, pmd, address, freeze, page);
2379 }
2380
2381 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2382                              unsigned long start,
2383                              unsigned long end,
2384                              long adjust_next)
2385 {
2386         /*
2387          * If the new start address isn't hpage aligned and it could
2388          * previously contain an hugepage: check if we need to split
2389          * an huge pmd.
2390          */
2391         if (start & ~HPAGE_PMD_MASK &&
2392             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2393             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2394                 split_huge_pmd_address(vma, start, false, NULL);
2395
2396         /*
2397          * If the new end address isn't hpage aligned and it could
2398          * previously contain an hugepage: check if we need to split
2399          * an huge pmd.
2400          */
2401         if (end & ~HPAGE_PMD_MASK &&
2402             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2403             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2404                 split_huge_pmd_address(vma, end, false, NULL);
2405
2406         /*
2407          * If we're also updating the vma->vm_next->vm_start, if the new
2408          * vm_next->vm_start isn't page aligned and it could previously
2409          * contain an hugepage: check if we need to split an huge pmd.
2410          */
2411         if (adjust_next > 0) {
2412                 struct vm_area_struct *next = vma->vm_next;
2413                 unsigned long nstart = next->vm_start;
2414                 nstart += adjust_next << PAGE_SHIFT;
2415                 if (nstart & ~HPAGE_PMD_MASK &&
2416                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2417                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2418                         split_huge_pmd_address(next, nstart, false, NULL);
2419         }
2420 }
2421
2422 static void unmap_page(struct page *page)
2423 {
2424         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2425                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2426         bool unmap_success;
2427
2428         VM_BUG_ON_PAGE(!PageHead(page), page);
2429
2430         if (PageAnon(page))
2431                 ttu_flags |= TTU_SPLIT_FREEZE;
2432
2433         unmap_success = try_to_unmap(page, ttu_flags);
2434         VM_BUG_ON_PAGE(!unmap_success, page);
2435 }
2436
2437 static void remap_page(struct page *page)
2438 {
2439         int i;
2440         if (PageTransHuge(page)) {
2441                 remove_migration_ptes(page, page, true);
2442         } else {
2443                 for (i = 0; i < HPAGE_PMD_NR; i++)
2444                         remove_migration_ptes(page + i, page + i, true);
2445         }
2446 }
2447
2448 static void __split_huge_page_tail(struct page *head, int tail,
2449                 struct lruvec *lruvec, struct list_head *list)
2450 {
2451         struct page *page_tail = head + tail;
2452
2453         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2454
2455         /*
2456          * Clone page flags before unfreezing refcount.
2457          *
2458          * After successful get_page_unless_zero() might follow flags change,
2459          * for exmaple lock_page() which set PG_waiters.
2460          */
2461         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2462         page_tail->flags |= (head->flags &
2463                         ((1L << PG_referenced) |
2464                          (1L << PG_swapbacked) |
2465                          (1L << PG_swapcache) |
2466                          (1L << PG_mlocked) |
2467                          (1L << PG_uptodate) |
2468                          (1L << PG_active) |
2469                          (1L << PG_workingset) |
2470                          (1L << PG_locked) |
2471                          (1L << PG_unevictable) |
2472                          (1L << PG_dirty)));
2473
2474         /* ->mapping in first tail page is compound_mapcount */
2475         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2476                         page_tail);
2477         page_tail->mapping = head->mapping;
2478         page_tail->index = head->index + tail;
2479
2480         /* Page flags must be visible before we make the page non-compound. */
2481         smp_wmb();
2482
2483         /*
2484          * Clear PageTail before unfreezing page refcount.
2485          *
2486          * After successful get_page_unless_zero() might follow put_page()
2487          * which needs correct compound_head().
2488          */
2489         clear_compound_head(page_tail);
2490
2491         /* Finally unfreeze refcount. Additional reference from page cache. */
2492         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2493                                           PageSwapCache(head)));
2494
2495         if (page_is_young(head))
2496                 set_page_young(page_tail);
2497         if (page_is_idle(head))
2498                 set_page_idle(page_tail);
2499
2500         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2501
2502         /*
2503          * always add to the tail because some iterators expect new
2504          * pages to show after the currently processed elements - e.g.
2505          * migrate_pages
2506          */
2507         lru_add_page_tail(head, page_tail, lruvec, list);
2508 }
2509
2510 static void __split_huge_page(struct page *page, struct list_head *list,
2511                 pgoff_t end, unsigned long flags)
2512 {
2513         struct page *head = compound_head(page);
2514         pg_data_t *pgdat = page_pgdat(head);
2515         struct lruvec *lruvec;
2516         struct address_space *swap_cache = NULL;
2517         unsigned long offset = 0;
2518         int i;
2519
2520         lruvec = mem_cgroup_page_lruvec(head, pgdat);
2521
2522         /* complete memcg works before add pages to LRU */
2523         mem_cgroup_split_huge_fixup(head);
2524
2525         if (PageAnon(head) && PageSwapCache(head)) {
2526                 swp_entry_t entry = { .val = page_private(head) };
2527
2528                 offset = swp_offset(entry);
2529                 swap_cache = swap_address_space(entry);
2530                 xa_lock(&swap_cache->i_pages);
2531         }
2532
2533         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2534                 __split_huge_page_tail(head, i, lruvec, list);
2535                 /* Some pages can be beyond i_size: drop them from page cache */
2536                 if (head[i].index >= end) {
2537                         ClearPageDirty(head + i);
2538                         __delete_from_page_cache(head + i, NULL);
2539                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2540                                 shmem_uncharge(head->mapping->host, 1);
2541                         put_page(head + i);
2542                 } else if (!PageAnon(page)) {
2543                         __xa_store(&head->mapping->i_pages, head[i].index,
2544                                         head + i, 0);
2545                 } else if (swap_cache) {
2546                         __xa_store(&swap_cache->i_pages, offset + i,
2547                                         head + i, 0);
2548                 }
2549         }
2550
2551         ClearPageCompound(head);
2552
2553         split_page_owner(head, HPAGE_PMD_ORDER);
2554
2555         /* See comment in __split_huge_page_tail() */
2556         if (PageAnon(head)) {
2557                 /* Additional pin to swap cache */
2558                 if (PageSwapCache(head)) {
2559                         page_ref_add(head, 2);
2560                         xa_unlock(&swap_cache->i_pages);
2561                 } else {
2562                         page_ref_inc(head);
2563                 }
2564         } else {
2565                 /* Additional pin to page cache */
2566                 page_ref_add(head, 2);
2567                 xa_unlock(&head->mapping->i_pages);
2568         }
2569
2570         spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2571
2572         remap_page(head);
2573
2574         for (i = 0; i < HPAGE_PMD_NR; i++) {
2575                 struct page *subpage = head + i;
2576                 if (subpage == page)
2577                         continue;
2578                 unlock_page(subpage);
2579
2580                 /*
2581                  * Subpages may be freed if there wasn't any mapping
2582                  * like if add_to_swap() is running on a lru page that
2583                  * had its mapping zapped. And freeing these pages
2584                  * requires taking the lru_lock so we do the put_page
2585                  * of the tail pages after the split is complete.
2586                  */
2587                 put_page(subpage);
2588         }
2589 }
2590
2591 int total_mapcount(struct page *page)
2592 {
2593         int i, compound, ret;
2594
2595         VM_BUG_ON_PAGE(PageTail(page), page);
2596
2597         if (likely(!PageCompound(page)))
2598                 return atomic_read(&page->_mapcount) + 1;
2599
2600         compound = compound_mapcount(page);
2601         if (PageHuge(page))
2602                 return compound;
2603         ret = compound;
2604         for (i = 0; i < HPAGE_PMD_NR; i++)
2605                 ret += atomic_read(&page[i]._mapcount) + 1;
2606         /* File pages has compound_mapcount included in _mapcount */
2607         if (!PageAnon(page))
2608                 return ret - compound * HPAGE_PMD_NR;
2609         if (PageDoubleMap(page))
2610                 ret -= HPAGE_PMD_NR;
2611         return ret;
2612 }
2613
2614 /*
2615  * This calculates accurately how many mappings a transparent hugepage
2616  * has (unlike page_mapcount() which isn't fully accurate). This full
2617  * accuracy is primarily needed to know if copy-on-write faults can
2618  * reuse the page and change the mapping to read-write instead of
2619  * copying them. At the same time this returns the total_mapcount too.
2620  *
2621  * The function returns the highest mapcount any one of the subpages
2622  * has. If the return value is one, even if different processes are
2623  * mapping different subpages of the transparent hugepage, they can
2624  * all reuse it, because each process is reusing a different subpage.
2625  *
2626  * The total_mapcount is instead counting all virtual mappings of the
2627  * subpages. If the total_mapcount is equal to "one", it tells the
2628  * caller all mappings belong to the same "mm" and in turn the
2629  * anon_vma of the transparent hugepage can become the vma->anon_vma
2630  * local one as no other process may be mapping any of the subpages.
2631  *
2632  * It would be more accurate to replace page_mapcount() with
2633  * page_trans_huge_mapcount(), however we only use
2634  * page_trans_huge_mapcount() in the copy-on-write faults where we
2635  * need full accuracy to avoid breaking page pinning, because
2636  * page_trans_huge_mapcount() is slower than page_mapcount().
2637  */
2638 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2639 {
2640         int i, ret, _total_mapcount, mapcount;
2641
2642         /* hugetlbfs shouldn't call it */
2643         VM_BUG_ON_PAGE(PageHuge(page), page);
2644
2645         if (likely(!PageTransCompound(page))) {
2646                 mapcount = atomic_read(&page->_mapcount) + 1;
2647                 if (total_mapcount)
2648                         *total_mapcount = mapcount;
2649                 return mapcount;
2650         }
2651
2652         page = compound_head(page);
2653
2654         _total_mapcount = ret = 0;
2655         for (i = 0; i < HPAGE_PMD_NR; i++) {
2656                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2657                 ret = max(ret, mapcount);
2658                 _total_mapcount += mapcount;
2659         }
2660         if (PageDoubleMap(page)) {
2661                 ret -= 1;
2662                 _total_mapcount -= HPAGE_PMD_NR;
2663         }
2664         mapcount = compound_mapcount(page);
2665         ret += mapcount;
2666         _total_mapcount += mapcount;
2667         if (total_mapcount)
2668                 *total_mapcount = _total_mapcount;
2669         return ret;
2670 }
2671
2672 /* Racy check whether the huge page can be split */
2673 bool can_split_huge_page(struct page *page, int *pextra_pins)
2674 {
2675         int extra_pins;
2676
2677         /* Additional pins from page cache */
2678         if (PageAnon(page))
2679                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2680         else
2681                 extra_pins = HPAGE_PMD_NR;
2682         if (pextra_pins)
2683                 *pextra_pins = extra_pins;
2684         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2685 }
2686
2687 /*
2688  * This function splits huge page into normal pages. @page can point to any
2689  * subpage of huge page to split. Split doesn't change the position of @page.
2690  *
2691  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2692  * The huge page must be locked.
2693  *
2694  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2695  *
2696  * Both head page and tail pages will inherit mapping, flags, and so on from
2697  * the hugepage.
2698  *
2699  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2700  * they are not mapped.
2701  *
2702  * Returns 0 if the hugepage is split successfully.
2703  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2704  * us.
2705  */
2706 int split_huge_page_to_list(struct page *page, struct list_head *list)
2707 {
2708         struct page *head = compound_head(page);
2709         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2710         struct deferred_split *ds_queue = get_deferred_split_queue(head);
2711         struct anon_vma *anon_vma = NULL;
2712         struct address_space *mapping = NULL;
2713         int count, mapcount, extra_pins, ret;
2714         bool mlocked;
2715         unsigned long flags;
2716         pgoff_t end;
2717
2718         VM_BUG_ON_PAGE(is_huge_zero_page(head), head);
2719         VM_BUG_ON_PAGE(!PageLocked(head), head);
2720         VM_BUG_ON_PAGE(!PageCompound(head), head);
2721
2722         if (PageWriteback(head))
2723                 return -EBUSY;
2724
2725         if (PageAnon(head)) {
2726                 /*
2727                  * The caller does not necessarily hold an mmap_sem that would
2728                  * prevent the anon_vma disappearing so we first we take a
2729                  * reference to it and then lock the anon_vma for write. This
2730                  * is similar to page_lock_anon_vma_read except the write lock
2731                  * is taken to serialise against parallel split or collapse
2732                  * operations.
2733                  */
2734                 anon_vma = page_get_anon_vma(head);
2735                 if (!anon_vma) {
2736                         ret = -EBUSY;
2737                         goto out;
2738                 }
2739                 end = -1;
2740                 mapping = NULL;
2741                 anon_vma_lock_write(anon_vma);
2742         } else {
2743                 mapping = head->mapping;
2744
2745                 /* Truncated ? */
2746                 if (!mapping) {
2747                         ret = -EBUSY;
2748                         goto out;
2749                 }
2750
2751                 anon_vma = NULL;
2752                 i_mmap_lock_read(mapping);
2753
2754                 /*
2755                  *__split_huge_page() may need to trim off pages beyond EOF:
2756                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2757                  * which cannot be nested inside the page tree lock. So note
2758                  * end now: i_size itself may be changed at any moment, but
2759                  * head page lock is good enough to serialize the trimming.
2760                  */
2761                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2762         }
2763
2764         /*
2765          * Racy check if we can split the page, before unmap_page() will
2766          * split PMDs
2767          */
2768         if (!can_split_huge_page(head, &extra_pins)) {
2769                 ret = -EBUSY;
2770                 goto out_unlock;
2771         }
2772
2773         mlocked = PageMlocked(head);
2774         unmap_page(head);
2775         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2776
2777         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2778         if (mlocked)
2779                 lru_add_drain();
2780
2781         /* prevent PageLRU to go away from under us, and freeze lru stats */
2782         spin_lock_irqsave(&pgdata->lru_lock, flags);
2783
2784         if (mapping) {
2785                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2786
2787                 /*
2788                  * Check if the head page is present in page cache.
2789                  * We assume all tail are present too, if head is there.
2790                  */
2791                 xa_lock(&mapping->i_pages);
2792                 if (xas_load(&xas) != head)
2793                         goto fail;
2794         }
2795
2796         /* Prevent deferred_split_scan() touching ->_refcount */
2797         spin_lock(&ds_queue->split_queue_lock);
2798         count = page_count(head);
2799         mapcount = total_mapcount(head);
2800         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2801                 if (!list_empty(page_deferred_list(head))) {
2802                         ds_queue->split_queue_len--;
2803                         list_del(page_deferred_list(head));
2804                 }
2805                 spin_unlock(&ds_queue->split_queue_lock);
2806                 if (mapping) {
2807                         if (PageSwapBacked(head))
2808                                 __dec_node_page_state(head, NR_SHMEM_THPS);
2809                         else
2810                                 __dec_node_page_state(head, NR_FILE_THPS);
2811                 }
2812
2813                 __split_huge_page(page, list, end, flags);
2814                 if (PageSwapCache(head)) {
2815                         swp_entry_t entry = { .val = page_private(head) };
2816
2817                         ret = split_swap_cluster(entry);
2818                 } else
2819                         ret = 0;
2820         } else {
2821                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2822                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2823                                         mapcount, count);
2824                         if (PageTail(page))
2825                                 dump_page(head, NULL);
2826                         dump_page(page, "total_mapcount(head) > 0");
2827                         BUG();
2828                 }
2829                 spin_unlock(&ds_queue->split_queue_lock);
2830 fail:           if (mapping)
2831                         xa_unlock(&mapping->i_pages);
2832                 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2833                 remap_page(head);
2834                 ret = -EBUSY;
2835         }
2836
2837 out_unlock:
2838         if (anon_vma) {
2839                 anon_vma_unlock_write(anon_vma);
2840                 put_anon_vma(anon_vma);
2841         }
2842         if (mapping)
2843                 i_mmap_unlock_read(mapping);
2844 out:
2845         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2846         return ret;
2847 }
2848
2849 void free_transhuge_page(struct page *page)
2850 {
2851         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2852         unsigned long flags;
2853
2854         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2855         if (!list_empty(page_deferred_list(page))) {
2856                 ds_queue->split_queue_len--;
2857                 list_del(page_deferred_list(page));
2858         }
2859         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2860         free_compound_page(page);
2861 }
2862
2863 void deferred_split_huge_page(struct page *page)
2864 {
2865         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2866 #ifdef CONFIG_MEMCG
2867         struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
2868 #endif
2869         unsigned long flags;
2870
2871         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2872
2873         /*
2874          * The try_to_unmap() in page reclaim path might reach here too,
2875          * this may cause a race condition to corrupt deferred split queue.
2876          * And, if page reclaim is already handling the same page, it is
2877          * unnecessary to handle it again in shrinker.
2878          *
2879          * Check PageSwapCache to determine if the page is being
2880          * handled by page reclaim since THP swap would add the page into
2881          * swap cache before calling try_to_unmap().
2882          */
2883         if (PageSwapCache(page))
2884                 return;
2885
2886         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2887         if (list_empty(page_deferred_list(page))) {
2888                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2889                 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2890                 ds_queue->split_queue_len++;
2891 #ifdef CONFIG_MEMCG
2892                 if (memcg)
2893                         memcg_set_shrinker_bit(memcg, page_to_nid(page),
2894                                                deferred_split_shrinker.id);
2895 #endif
2896         }
2897         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2898 }
2899
2900 static unsigned long deferred_split_count(struct shrinker *shrink,
2901                 struct shrink_control *sc)
2902 {
2903         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2904         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2905
2906 #ifdef CONFIG_MEMCG
2907         if (sc->memcg)
2908                 ds_queue = &sc->memcg->deferred_split_queue;
2909 #endif
2910         return READ_ONCE(ds_queue->split_queue_len);
2911 }
2912
2913 static unsigned long deferred_split_scan(struct shrinker *shrink,
2914                 struct shrink_control *sc)
2915 {
2916         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2917         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2918         unsigned long flags;
2919         LIST_HEAD(list), *pos, *next;
2920         struct page *page;
2921         int split = 0;
2922
2923 #ifdef CONFIG_MEMCG
2924         if (sc->memcg)
2925                 ds_queue = &sc->memcg->deferred_split_queue;
2926 #endif
2927
2928         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2929         /* Take pin on all head pages to avoid freeing them under us */
2930         list_for_each_safe(pos, next, &ds_queue->split_queue) {
2931                 page = list_entry((void *)pos, struct page, mapping);
2932                 page = compound_head(page);
2933                 if (get_page_unless_zero(page)) {
2934                         list_move(page_deferred_list(page), &list);
2935                 } else {
2936                         /* We lost race with put_compound_page() */
2937                         list_del_init(page_deferred_list(page));
2938                         ds_queue->split_queue_len--;
2939                 }
2940                 if (!--sc->nr_to_scan)
2941                         break;
2942         }
2943         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2944
2945         list_for_each_safe(pos, next, &list) {
2946                 page = list_entry((void *)pos, struct page, mapping);
2947                 if (!trylock_page(page))
2948                         goto next;
2949                 /* split_huge_page() removes page from list on success */
2950                 if (!split_huge_page(page))
2951                         split++;
2952                 unlock_page(page);
2953 next:
2954                 put_page(page);
2955         }
2956
2957         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2958         list_splice_tail(&list, &ds_queue->split_queue);
2959         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2960
2961         /*
2962          * Stop shrinker if we didn't split any page, but the queue is empty.
2963          * This can happen if pages were freed under us.
2964          */
2965         if (!split && list_empty(&ds_queue->split_queue))
2966                 return SHRINK_STOP;
2967         return split;
2968 }
2969
2970 static struct shrinker deferred_split_shrinker = {
2971         .count_objects = deferred_split_count,
2972         .scan_objects = deferred_split_scan,
2973         .seeks = DEFAULT_SEEKS,
2974         .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
2975                  SHRINKER_NONSLAB,
2976 };
2977
2978 #ifdef CONFIG_DEBUG_FS
2979 static int split_huge_pages_set(void *data, u64 val)
2980 {
2981         struct zone *zone;
2982         struct page *page;
2983         unsigned long pfn, max_zone_pfn;
2984         unsigned long total = 0, split = 0;
2985
2986         if (val != 1)
2987                 return -EINVAL;
2988
2989         for_each_populated_zone(zone) {
2990                 max_zone_pfn = zone_end_pfn(zone);
2991                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2992                         if (!pfn_valid(pfn))
2993                                 continue;
2994
2995                         page = pfn_to_page(pfn);
2996                         if (!get_page_unless_zero(page))
2997                                 continue;
2998
2999                         if (zone != page_zone(page))
3000                                 goto next;
3001
3002                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
3003                                 goto next;
3004
3005                         total++;
3006                         lock_page(page);
3007                         if (!split_huge_page(page))
3008                                 split++;
3009                         unlock_page(page);
3010 next:
3011                         put_page(page);
3012                 }
3013         }
3014
3015         pr_info("%lu of %lu THP split\n", split, total);
3016
3017         return 0;
3018 }
3019 DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3020                 "%llu\n");
3021
3022 static int __init split_huge_pages_debugfs(void)
3023 {
3024         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3025                             &split_huge_pages_fops);
3026         return 0;
3027 }
3028 late_initcall(split_huge_pages_debugfs);
3029 #endif
3030
3031 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3032 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3033                 struct page *page)
3034 {
3035         struct vm_area_struct *vma = pvmw->vma;
3036         struct mm_struct *mm = vma->vm_mm;
3037         unsigned long address = pvmw->address;
3038         pmd_t pmdval;
3039         swp_entry_t entry;
3040         pmd_t pmdswp;
3041
3042         if (!(pvmw->pmd && !pvmw->pte))
3043                 return;
3044
3045         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3046         pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
3047         if (pmd_dirty(pmdval))
3048                 set_page_dirty(page);
3049         entry = make_migration_entry(page, pmd_write(pmdval));
3050         pmdswp = swp_entry_to_pmd(entry);
3051         if (pmd_soft_dirty(pmdval))
3052                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3053         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3054         page_remove_rmap(page, true);
3055         put_page(page);
3056 }
3057
3058 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3059 {
3060         struct vm_area_struct *vma = pvmw->vma;
3061         struct mm_struct *mm = vma->vm_mm;
3062         unsigned long address = pvmw->address;
3063         unsigned long mmun_start = address & HPAGE_PMD_MASK;
3064         pmd_t pmde;
3065         swp_entry_t entry;
3066
3067         if (!(pvmw->pmd && !pvmw->pte))
3068                 return;
3069
3070         entry = pmd_to_swp_entry(*pvmw->pmd);
3071         get_page(new);
3072         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
3073         if (pmd_swp_soft_dirty(*pvmw->pmd))
3074                 pmde = pmd_mksoft_dirty(pmde);
3075         if (is_write_migration_entry(entry))
3076                 pmde = maybe_pmd_mkwrite(pmde, vma);
3077
3078         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
3079         if (PageAnon(new))
3080                 page_add_anon_rmap(new, vma, mmun_start, true);
3081         else
3082                 page_add_file_rmap(new, true);
3083         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3084         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3085                 mlock_vma_page(new);
3086         update_mmu_cache_pmd(vma, address, pvmw->pmd);
3087 }
3088 #endif