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 #ifdef CONFIG_SHMEM
 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                 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
 601                 return VM_FAULT_FALLBACK;
 602         }
 603
 604         pgtable = pte_alloc_one(vma->vm_mm);
 605         if (unlikely(!pgtable)) {
 606                 ret = VM_FAULT_OOM;
 607                 goto release;
 608         }
 609
 610         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
 611         /*
 612          * The memory barrier inside __SetPageUptodate makes sure that
 613          * clear_huge_page writes become visible before the set_pmd_at()
 614          * write.
 615          */
 616         __SetPageUptodate(page);
 617
 618         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 619         if (unlikely(!pmd_none(*vmf->pmd))) {
 620                 goto unlock_release;
 621         } else {
 622                 pmd_t entry;
 623
 624                 ret = check_stable_address_space(vma->vm_mm);
 625                 if (ret)
 626                         goto unlock_release;
 627
 628                 /* Deliver the page fault to userland */
 629                 if (userfaultfd_missing(vma)) {
 630                         vm_fault_t ret2;
 631
 632                         spin_unlock(vmf->ptl);
 633                         mem_cgroup_cancel_charge(page, memcg, true);
 634                         put_page(page);
 635                         pte_free(vma->vm_mm, pgtable);
 636                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
 637                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
 638                         return ret2;
 639                 }
 640
 641                 entry = mk_huge_pmd(page, vma->vm_page_prot);
 642                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 643                 page_add_new_anon_rmap(page, vma, haddr, true);
 644                 mem_cgroup_commit_charge(page, memcg, false, true);
 645                 lru_cache_add_active_or_unevictable(page, vma);
 646                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 647                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
 648                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
 649                 mm_inc_nr_ptes(vma->vm_mm);
 650                 spin_unlock(vmf->ptl);
 651                 count_vm_event(THP_FAULT_ALLOC);
 652                 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
 653         }
 654
 655         return 0;
 656 unlock_release:
 657         spin_unlock(vmf->ptl);
 658 release:
 659         if (pgtable)
 660                 pte_free(vma->vm_mm, pgtable);
 661         mem_cgroup_cancel_charge(page, memcg, true);
 662         put_page(page);
 663         return ret;
 664
 665 }
 666
 667 /*
 668  * always: directly stall for all thp allocations
 669  * defer: wake kswapd and fail if not immediately available
 670  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
 671  *                fail if not immediately available
 672  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
 673  *          available
 674  * never: never stall for any thp allocation
 675  */
 676 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
 677 {
 678         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
 679
 680         /* Always do synchronous compaction */
 681         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
 682                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
 683
 684         /* Kick kcompactd and fail quickly */
 685         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
 686                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
 687
 688         /* Synchronous compaction if madvised, otherwise kick kcompactd */
 689         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
 690                 return GFP_TRANSHUGE_LIGHT |
 691                         (vma_madvised ? __GFP_DIRECT_RECLAIM :
 692                                         __GFP_KSWAPD_RECLAIM);
 693
 694         /* Only do synchronous compaction if madvised */
 695         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
 696                 return GFP_TRANSHUGE_LIGHT |
 697                        (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
 698
 699         return GFP_TRANSHUGE_LIGHT;
 700 }
 701
 702 /* Caller must hold page table lock. */
 703 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 704                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
 705                 struct page *zero_page)
 706 {
 707         pmd_t entry;
 708         if (!pmd_none(*pmd))
 709                 return false;
 710         entry = mk_pmd(zero_page, vma->vm_page_prot);
 711         entry = pmd_mkhuge(entry);
 712         if (pgtable)
 713                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 714         set_pmd_at(mm, haddr, pmd, entry);
 715         mm_inc_nr_ptes(mm);
 716         return true;
 717 }
 718
 719 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 720 {
 721         struct vm_area_struct *vma = vmf->vma;
 722         gfp_t gfp;
 723         struct page *page;
 724         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 725
 726         if (!transhuge_vma_suitable(vma, haddr))
 727                 return VM_FAULT_FALLBACK;
 728         if (unlikely(anon_vma_prepare(vma)))
 729                 return VM_FAULT_OOM;
 730         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
 731                 return VM_FAULT_OOM;
 732         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 733                         !mm_forbids_zeropage(vma->vm_mm) &&
 734                         transparent_hugepage_use_zero_page()) {
 735                 pgtable_t pgtable;
 736                 struct page *zero_page;
 737                 bool set;
 738                 vm_fault_t ret;
 739                 pgtable = pte_alloc_one(vma->vm_mm);
 740                 if (unlikely(!pgtable))
 741                         return VM_FAULT_OOM;
 742                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
 743                 if (unlikely(!zero_page)) {
 744                         pte_free(vma->vm_mm, pgtable);
 745                         count_vm_event(THP_FAULT_FALLBACK);
 746                         return VM_FAULT_FALLBACK;
 747                 }
 748                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
 749                 ret = 0;
 750                 set = false;
 751                 if (pmd_none(*vmf->pmd)) {
 752                         ret = check_stable_address_space(vma->vm_mm);
 753                         if (ret) {
 754                                 spin_unlock(vmf->ptl);
 755                         } else if (userfaultfd_missing(vma)) {
 756                                 spin_unlock(vmf->ptl);
 757                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
 758                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
 759                         } else {
 760                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
 761                                                    haddr, vmf->pmd, zero_page);
 762                                 spin_unlock(vmf->ptl);
 763                                 set = true;
 764                         }
 765                 } else
 766                         spin_unlock(vmf->ptl);
 767                 if (!set)
 768                         pte_free(vma->vm_mm, pgtable);
 769                 return ret;
 770         }
 771         gfp = alloc_hugepage_direct_gfpmask(vma);
 772         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
 773         if (unlikely(!page)) {
 774                 count_vm_event(THP_FAULT_FALLBACK);
 775                 return VM_FAULT_FALLBACK;
 776         }
 777         prep_transhuge_page(page);
 778         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
 779 }
 780
 781 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
 782                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
 783                 pgtable_t pgtable)
 784 {
 785         struct mm_struct *mm = vma->vm_mm;
 786         pmd_t entry;
 787         spinlock_t *ptl;
 788
 789         ptl = pmd_lock(mm, pmd);
 790         if (!pmd_none(*pmd)) {
 791                 if (write) {
 792                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
 793                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
 794                                 goto out_unlock;
 795                         }
 796                         entry = pmd_mkyoung(*pmd);
 797                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 798                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 799                                 update_mmu_cache_pmd(vma, addr, pmd);
 800                 }
 801
 802                 goto out_unlock;
 803         }
 804
 805         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
 806         if (pfn_t_devmap(pfn))
 807                 entry = pmd_mkdevmap(entry);
 808         if (write) {
 809                 entry = pmd_mkyoung(pmd_mkdirty(entry));
 810                 entry = maybe_pmd_mkwrite(entry, vma);
 811         }
 812
 813         if (pgtable) {
 814                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
 815                 mm_inc_nr_ptes(mm);
 816                 pgtable = NULL;
 817         }
 818
 819         set_pmd_at(mm, addr, pmd, entry);
 820         update_mmu_cache_pmd(vma, addr, pmd);
 821
 822 out_unlock:
 823         spin_unlock(ptl);
 824         if (pgtable)
 825                 pte_free(mm, pgtable);
 826 }
 827
 828 /**
 829  * vmf_insert_pfn_pmd_prot - insert a pmd size pfn
 830  * @vmf: Structure describing the fault
 831  * @pfn: pfn to insert
 832  * @pgprot: page protection to use
 833  * @write: whether it's a write fault
 834  *
 835  * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and
 836  * also consult the vmf_insert_mixed_prot() documentation when
 837  * @pgprot != @vmf->vma->vm_page_prot.
 838  *
 839  * Return: vm_fault_t value.
 840  */
 841 vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn,
 842                                    pgprot_t pgprot, bool write)
 843 {
 844         unsigned long addr = vmf->address & PMD_MASK;
 845         struct vm_area_struct *vma = vmf->vma;
 846         pgtable_t pgtable = NULL;
 847
 848         /*
 849          * If we had pmd_special, we could avoid all these restrictions,
 850          * but we need to be consistent with PTEs and architectures that
 851          * can't support a 'special' bit.
 852          */
 853         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 854                         !pfn_t_devmap(pfn));
 855         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 856                                                 (VM_PFNMAP|VM_MIXEDMAP));
 857         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 858
 859         if (addr < vma->vm_start || addr >= vma->vm_end)
 860                 return VM_FAULT_SIGBUS;
 861
 862         if (arch_needs_pgtable_deposit()) {
 863                 pgtable = pte_alloc_one(vma->vm_mm);
 864                 if (!pgtable)
 865                         return VM_FAULT_OOM;
 866         }
 867
 868         track_pfn_insert(vma, &pgprot, pfn);
 869
 870         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
 871         return VM_FAULT_NOPAGE;
 872 }
 873 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot);
 874
 875 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 876 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 877 {
 878         if (likely(vma->vm_flags & VM_WRITE))
 879                 pud = pud_mkwrite(pud);
 880         return pud;
 881 }
 882
 883 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
 884                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 885 {
 886         struct mm_struct *mm = vma->vm_mm;
 887         pud_t entry;
 888         spinlock_t *ptl;
 889
 890         ptl = pud_lock(mm, pud);
 891         if (!pud_none(*pud)) {
 892                 if (write) {
 893                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
 894                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
 895                                 goto out_unlock;
 896                         }
 897                         entry = pud_mkyoung(*pud);
 898                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 899                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 900                                 update_mmu_cache_pud(vma, addr, pud);
 901                 }
 902                 goto out_unlock;
 903         }
 904
 905         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
 906         if (pfn_t_devmap(pfn))
 907                 entry = pud_mkdevmap(entry);
 908         if (write) {
 909                 entry = pud_mkyoung(pud_mkdirty(entry));
 910                 entry = maybe_pud_mkwrite(entry, vma);
 911         }
 912         set_pud_at(mm, addr, pud, entry);
 913         update_mmu_cache_pud(vma, addr, pud);
 914
 915 out_unlock:
 916         spin_unlock(ptl);
 917 }
 918
 919 /**
 920  * vmf_insert_pfn_pud_prot - insert a pud size pfn
 921  * @vmf: Structure describing the fault
 922  * @pfn: pfn to insert
 923  * @pgprot: page protection to use
 924  * @write: whether it's a write fault
 925  *
 926  * Insert a pud size pfn. See vmf_insert_pfn() for additional info and
 927  * also consult the vmf_insert_mixed_prot() documentation when
 928  * @pgprot != @vmf->vma->vm_page_prot.
 929  *
 930  * Return: vm_fault_t value.
 931  */
 932 vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn,
 933                                    pgprot_t pgprot, bool write)
 934 {
 935         unsigned long addr = vmf->address & PUD_MASK;
 936         struct vm_area_struct *vma = vmf->vma;
 937
 938         /*
 939          * If we had pud_special, we could avoid all these restrictions,
 940          * but we need to be consistent with PTEs and architectures that
 941          * can't support a 'special' bit.
 942          */
 943         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
 944                         !pfn_t_devmap(pfn));
 945         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
 946                                                 (VM_PFNMAP|VM_MIXEDMAP));
 947         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 948
 949         if (addr < vma->vm_start || addr >= vma->vm_end)
 950                 return VM_FAULT_SIGBUS;
 951
 952         track_pfn_insert(vma, &pgprot, pfn);
 953
 954         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
 955         return VM_FAULT_NOPAGE;
 956 }
 957 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
 958 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 959
 960 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
 961                 pmd_t *pmd, int flags)
 962 {
 963         pmd_t _pmd;
 964
 965         _pmd = pmd_mkyoung(*pmd);
 966         if (flags & FOLL_WRITE)
 967                 _pmd = pmd_mkdirty(_pmd);
 968         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
 969                                 pmd, _pmd, flags & FOLL_WRITE))
 970                 update_mmu_cache_pmd(vma, addr, pmd);
 971 }
 972
 973 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 974                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
 975 {
 976         unsigned long pfn = pmd_pfn(*pmd);
 977         struct mm_struct *mm = vma->vm_mm;
 978         struct page *page;
 979
 980         assert_spin_locked(pmd_lockptr(mm, pmd));
 981
 982         /*
 983          * When we COW a devmap PMD entry, we split it into PTEs, so we should
 984          * not be in this function with `flags & FOLL_COW` set.
 985          */
 986         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
 987
 988         /* FOLL_GET and FOLL_PIN are mutually exclusive. */
 989         if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
 990                          (FOLL_PIN | FOLL_GET)))
 991                 return NULL;
 992
 993         if (flags & FOLL_WRITE && !pmd_write(*pmd))
 994                 return NULL;
 995
 996         if (pmd_present(*pmd) && pmd_devmap(*pmd))
 997                 /* pass */;
 998         else
 999                 return NULL;
1000
1001         if (flags & FOLL_TOUCH)
1002                 touch_pmd(vma, addr, pmd, flags);
1003
1004         /*
1005          * device mapped pages can only be returned if the
1006          * caller will manage the page reference count.
1007          */
1008         if (!(flags & (FOLL_GET | FOLL_PIN)))
1009                 return ERR_PTR(-EEXIST);
1010
1011         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1012         *pgmap = get_dev_pagemap(pfn, *pgmap);
1013         if (!*pgmap)
1014                 return ERR_PTR(-EFAULT);
1015         page = pfn_to_page(pfn);
1016         if (!try_grab_page(page, flags))
1017                 page = ERR_PTR(-ENOMEM);
1018
1019         return page;
1020 }
1021
1022 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1023                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1024                   struct vm_area_struct *vma)
1025 {
1026         spinlock_t *dst_ptl, *src_ptl;
1027         struct page *src_page;
1028         pmd_t pmd;
1029         pgtable_t pgtable = NULL;
1030         int ret = -ENOMEM;
1031
1032         /* Skip if can be re-fill on fault */
1033         if (!vma_is_anonymous(vma))
1034                 return 0;
1035
1036         pgtable = pte_alloc_one(dst_mm);
1037         if (unlikely(!pgtable))
1038                 goto out;
1039
1040         dst_ptl = pmd_lock(dst_mm, dst_pmd);
1041         src_ptl = pmd_lockptr(src_mm, src_pmd);
1042         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1043
1044         ret = -EAGAIN;
1045         pmd = *src_pmd;
1046
1047         /*
1048          * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA
1049          * does not have the VM_UFFD_WP, which means that the uffd
1050          * fork event is not enabled.
1051          */
1052         if (!(vma->vm_flags & VM_UFFD_WP))
1053                 pmd = pmd_clear_uffd_wp(pmd);
1054
1055 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1056         if (unlikely(is_swap_pmd(pmd))) {
1057                 swp_entry_t entry = pmd_to_swp_entry(pmd);
1058
1059                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1060                 if (is_write_migration_entry(entry)) {
1061                         make_migration_entry_read(&entry);
1062                         pmd = swp_entry_to_pmd(entry);
1063                         if (pmd_swp_soft_dirty(*src_pmd))
1064                                 pmd = pmd_swp_mksoft_dirty(pmd);
1065                         set_pmd_at(src_mm, addr, src_pmd, pmd);
1066                 }
1067                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1068                 mm_inc_nr_ptes(dst_mm);
1069                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1070                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1071                 ret = 0;
1072                 goto out_unlock;
1073         }
1074 #endif
1075
1076         if (unlikely(!pmd_trans_huge(pmd))) {
1077                 pte_free(dst_mm, pgtable);
1078                 goto out_unlock;
1079         }
1080         /*
1081          * When page table lock is held, the huge zero pmd should not be
1082          * under splitting since we don't split the page itself, only pmd to
1083          * a page table.
1084          */
1085         if (is_huge_zero_pmd(pmd)) {
1086                 struct page *zero_page;
1087                 /*
1088                  * get_huge_zero_page() will never allocate a new page here,
1089                  * since we already have a zero page to copy. It just takes a
1090                  * reference.
1091                  */
1092                 zero_page = mm_get_huge_zero_page(dst_mm);
1093                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1094                                 zero_page);
1095                 ret = 0;
1096                 goto out_unlock;
1097         }
1098
1099         src_page = pmd_page(pmd);
1100         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1101         get_page(src_page);
1102         page_dup_rmap(src_page, true);
1103         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1104         mm_inc_nr_ptes(dst_mm);
1105         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1106
1107         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1108         pmd = pmd_mkold(pmd_wrprotect(pmd));
1109         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1110
1111         ret = 0;
1112 out_unlock:
1113         spin_unlock(src_ptl);
1114         spin_unlock(dst_ptl);
1115 out:
1116         return ret;
1117 }
1118
1119 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1120 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1121                 pud_t *pud, int flags)
1122 {
1123         pud_t _pud;
1124
1125         _pud = pud_mkyoung(*pud);
1126         if (flags & FOLL_WRITE)
1127                 _pud = pud_mkdirty(_pud);
1128         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1129                                 pud, _pud, flags & FOLL_WRITE))
1130                 update_mmu_cache_pud(vma, addr, pud);
1131 }
1132
1133 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1134                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1135 {
1136         unsigned long pfn = pud_pfn(*pud);
1137         struct mm_struct *mm = vma->vm_mm;
1138         struct page *page;
1139
1140         assert_spin_locked(pud_lockptr(mm, pud));
1141
1142         if (flags & FOLL_WRITE && !pud_write(*pud))
1143                 return NULL;
1144
1145         /* FOLL_GET and FOLL_PIN are mutually exclusive. */
1146         if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
1147                          (FOLL_PIN | FOLL_GET)))
1148                 return NULL;
1149
1150         if (pud_present(*pud) && pud_devmap(*pud))
1151                 /* pass */;
1152         else
1153                 return NULL;
1154
1155         if (flags & FOLL_TOUCH)
1156                 touch_pud(vma, addr, pud, flags);
1157
1158         /*
1159          * device mapped pages can only be returned if the
1160          * caller will manage the page reference count.
1161          *
1162          * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
1163          */
1164         if (!(flags & (FOLL_GET | FOLL_PIN)))
1165                 return ERR_PTR(-EEXIST);
1166
1167         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1168         *pgmap = get_dev_pagemap(pfn, *pgmap);
1169         if (!*pgmap)
1170                 return ERR_PTR(-EFAULT);
1171         page = pfn_to_page(pfn);
1172         if (!try_grab_page(page, flags))
1173                 page = ERR_PTR(-ENOMEM);
1174
1175         return page;
1176 }
1177
1178 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1179                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1180                   struct vm_area_struct *vma)
1181 {
1182         spinlock_t *dst_ptl, *src_ptl;
1183         pud_t pud;
1184         int ret;
1185
1186         dst_ptl = pud_lock(dst_mm, dst_pud);
1187         src_ptl = pud_lockptr(src_mm, src_pud);
1188         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1189
1190         ret = -EAGAIN;
1191         pud = *src_pud;
1192         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1193                 goto out_unlock;
1194
1195         /*
1196          * When page table lock is held, the huge zero pud should not be
1197          * under splitting since we don't split the page itself, only pud to
1198          * a page table.
1199          */
1200         if (is_huge_zero_pud(pud)) {
1201                 /* No huge zero pud yet */
1202         }
1203
1204         pudp_set_wrprotect(src_mm, addr, src_pud);
1205         pud = pud_mkold(pud_wrprotect(pud));
1206         set_pud_at(dst_mm, addr, dst_pud, pud);
1207
1208         ret = 0;
1209 out_unlock:
1210         spin_unlock(src_ptl);
1211         spin_unlock(dst_ptl);
1212         return ret;
1213 }
1214
1215 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1216 {
1217         pud_t entry;
1218         unsigned long haddr;
1219         bool write = vmf->flags & FAULT_FLAG_WRITE;
1220
1221         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1222         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1223                 goto unlock;
1224
1225         entry = pud_mkyoung(orig_pud);
1226         if (write)
1227                 entry = pud_mkdirty(entry);
1228         haddr = vmf->address & HPAGE_PUD_MASK;
1229         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1230                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1231
1232 unlock:
1233         spin_unlock(vmf->ptl);
1234 }
1235 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1236
1237 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1238 {
1239         pmd_t entry;
1240         unsigned long haddr;
1241         bool write = vmf->flags & FAULT_FLAG_WRITE;
1242
1243         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1244         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1245                 goto unlock;
1246
1247         entry = pmd_mkyoung(orig_pmd);
1248         if (write)
1249                 entry = pmd_mkdirty(entry);
1250         haddr = vmf->address & HPAGE_PMD_MASK;
1251         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1252                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1253
1254 unlock:
1255         spin_unlock(vmf->ptl);
1256 }
1257
1258 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1259                         pmd_t orig_pmd, struct page *page)
1260 {
1261         struct vm_area_struct *vma = vmf->vma;
1262         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1263         struct mem_cgroup *memcg;
1264         pgtable_t pgtable;
1265         pmd_t _pmd;
1266         int i;
1267         vm_fault_t ret = 0;
1268         struct page **pages;
1269         struct mmu_notifier_range range;
1270
1271         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1272                               GFP_KERNEL);
1273         if (unlikely(!pages)) {
1274                 ret |= VM_FAULT_OOM;
1275                 goto out;
1276         }
1277
1278         for (i = 0; i < HPAGE_PMD_NR; i++) {
1279                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1280                                                vmf->address, page_to_nid(page));
1281                 if (unlikely(!pages[i] ||
1282                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1283                                      GFP_KERNEL, &memcg, false))) {
1284                         if (pages[i])
1285                                 put_page(pages[i]);
1286                         while (--i >= 0) {
1287                                 memcg = (void *)page_private(pages[i]);
1288                                 set_page_private(pages[i], 0);
1289                                 mem_cgroup_cancel_charge(pages[i], memcg,
1290                                                 false);
1291                                 put_page(pages[i]);
1292                         }
1293                         kfree(pages);
1294                         ret |= VM_FAULT_OOM;
1295                         goto out;
1296                 }
1297                 set_page_private(pages[i], (unsigned long)memcg);
1298         }
1299
1300         for (i = 0; i < HPAGE_PMD_NR; i++) {
1301                 copy_user_highpage(pages[i], page + i,
1302                                    haddr + PAGE_SIZE * i, vma);
1303                 __SetPageUptodate(pages[i]);
1304                 cond_resched();
1305         }
1306
1307         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1308                                 haddr, haddr + HPAGE_PMD_SIZE);
1309         mmu_notifier_invalidate_range_start(&range);
1310
1311         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1312         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1313                 goto out_free_pages;
1314         VM_BUG_ON_PAGE(!PageHead(page), page);
1315
1316         /*
1317          * Leave pmd empty until pte is filled note we must notify here as
1318          * concurrent CPU thread might write to new page before the call to
1319          * mmu_notifier_invalidate_range_end() happens which can lead to a
1320          * device seeing memory write in different order than CPU.
1321          *
1322          * See Documentation/vm/mmu_notifier.rst
1323          */
1324         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1325
1326         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1327         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1328
1329         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1330                 pte_t entry;
1331                 entry = mk_pte(pages[i], vma->vm_page_prot);
1332                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1333                 memcg = (void *)page_private(pages[i]);
1334                 set_page_private(pages[i], 0);
1335                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1336                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1337                 lru_cache_add_active_or_unevictable(pages[i], vma);
1338                 vmf->pte = pte_offset_map(&_pmd, haddr);
1339                 VM_BUG_ON(!pte_none(*vmf->pte));
1340                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1341                 pte_unmap(vmf->pte);
1342         }
1343         kfree(pages);
1344
1345         smp_wmb(); /* make pte visible before pmd */
1346         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1347         page_remove_rmap(page, true);
1348         spin_unlock(vmf->ptl);
1349
1350         /*
1351          * No need to double call mmu_notifier->invalidate_range() callback as
1352          * the above pmdp_huge_clear_flush_notify() did already call it.
1353          */
1354         mmu_notifier_invalidate_range_only_end(&range);
1355
1356         ret |= VM_FAULT_WRITE;
1357         put_page(page);
1358
1359 out:
1360         return ret;
1361
1362 out_free_pages:
1363         spin_unlock(vmf->ptl);
1364         mmu_notifier_invalidate_range_end(&range);
1365         for (i = 0; i < HPAGE_PMD_NR; i++) {
1366                 memcg = (void *)page_private(pages[i]);
1367                 set_page_private(pages[i], 0);
1368                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1369                 put_page(pages[i]);
1370         }
1371         kfree(pages);
1372         goto out;
1373 }
1374
1375 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1376 {
1377         struct vm_area_struct *vma = vmf->vma;
1378         struct page *page = NULL, *new_page;
1379         struct mem_cgroup *memcg;
1380         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1381         struct mmu_notifier_range range;
1382         gfp_t huge_gfp;                 /* for allocation and charge */
1383         vm_fault_t ret = 0;
1384
1385         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1386         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1387         if (is_huge_zero_pmd(orig_pmd))
1388                 goto alloc;
1389         spin_lock(vmf->ptl);
1390         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1391                 goto out_unlock;
1392
1393         page = pmd_page(orig_pmd);
1394         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1395         /*
1396          * We can only reuse the page if nobody else maps the huge page or it's
1397          * part.
1398          */
1399         if (!trylock_page(page)) {
1400                 get_page(page);
1401                 spin_unlock(vmf->ptl);
1402                 lock_page(page);
1403                 spin_lock(vmf->ptl);
1404                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1405                         unlock_page(page);
1406                         put_page(page);
1407                         goto out_unlock;
1408                 }
1409                 put_page(page);
1410         }
1411         if (reuse_swap_page(page, NULL)) {
1412                 pmd_t entry;
1413                 entry = pmd_mkyoung(orig_pmd);
1414                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1415                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1416                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1417                 ret |= VM_FAULT_WRITE;
1418                 unlock_page(page);
1419                 goto out_unlock;
1420         }
1421         unlock_page(page);
1422         get_page(page);
1423         spin_unlock(vmf->ptl);
1424 alloc:
1425         if (__transparent_hugepage_enabled(vma) &&
1426             !transparent_hugepage_debug_cow()) {
1427                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1428                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1429         } else
1430                 new_page = NULL;
1431
1432         if (likely(new_page)) {
1433                 prep_transhuge_page(new_page);
1434         } else {
1435                 if (!page) {
1436                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1437                         ret |= VM_FAULT_FALLBACK;
1438                 } else {
1439                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1440                         if (ret & VM_FAULT_OOM) {
1441                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1442                                 ret |= VM_FAULT_FALLBACK;
1443                         }
1444                         put_page(page);
1445                 }
1446                 count_vm_event(THP_FAULT_FALLBACK);
1447                 goto out;
1448         }
1449
1450         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1451                                         huge_gfp, &memcg, true))) {
1452                 put_page(new_page);
1453                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1454                 if (page)
1455                         put_page(page);
1456                 ret |= VM_FAULT_FALLBACK;
1457                 count_vm_event(THP_FAULT_FALLBACK);
1458                 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
1459                 goto out;
1460         }
1461
1462         count_vm_event(THP_FAULT_ALLOC);
1463         count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1464
1465         if (!page)
1466                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1467         else
1468                 copy_user_huge_page(new_page, page, vmf->address,
1469                                     vma, HPAGE_PMD_NR);
1470         __SetPageUptodate(new_page);
1471
1472         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1473                                 haddr, haddr + HPAGE_PMD_SIZE);
1474         mmu_notifier_invalidate_range_start(&range);
1475
1476         spin_lock(vmf->ptl);
1477         if (page)
1478                 put_page(page);
1479         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1480                 spin_unlock(vmf->ptl);
1481                 mem_cgroup_cancel_charge(new_page, memcg, true);
1482                 put_page(new_page);
1483                 goto out_mn;
1484         } else {
1485                 pmd_t entry;
1486                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1487                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1488                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1489                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1490                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1491                 lru_cache_add_active_or_unevictable(new_page, vma);
1492                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1493                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1494                 if (!page) {
1495                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1496                 } else {
1497                         VM_BUG_ON_PAGE(!PageHead(page), page);
1498                         page_remove_rmap(page, true);
1499                         put_page(page);
1500                 }
1501                 ret |= VM_FAULT_WRITE;
1502         }
1503         spin_unlock(vmf->ptl);
1504 out_mn:
1505         /*
1506          * No need to double call mmu_notifier->invalidate_range() callback as
1507          * the above pmdp_huge_clear_flush_notify() did already call it.
1508          */
1509         mmu_notifier_invalidate_range_only_end(&range);
1510 out:
1511         return ret;
1512 out_unlock:
1513         spin_unlock(vmf->ptl);
1514         return ret;
1515 }
1516
1517 /*
1518  * FOLL_FORCE can write to even unwritable pmd's, but only
1519  * after we've gone through a COW cycle and they are dirty.
1520  */
1521 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1522 {
1523         return pmd_write(pmd) ||
1524                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1525 }
1526
1527 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1528                                    unsigned long addr,
1529                                    pmd_t *pmd,
1530                                    unsigned int flags)
1531 {
1532         struct mm_struct *mm = vma->vm_mm;
1533         struct page *page = NULL;
1534
1535         assert_spin_locked(pmd_lockptr(mm, pmd));
1536
1537         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1538                 goto out;
1539
1540         /* Avoid dumping huge zero page */
1541         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1542                 return ERR_PTR(-EFAULT);
1543
1544         /* Full NUMA hinting faults to serialise migration in fault paths */
1545         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1546                 goto out;
1547
1548         page = pmd_page(*pmd);
1549         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1550
1551         if (!try_grab_page(page, flags))
1552                 return ERR_PTR(-ENOMEM);
1553
1554         if (flags & FOLL_TOUCH)
1555                 touch_pmd(vma, addr, pmd, flags);
1556
1557         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1558                 /*
1559                  * We don't mlock() pte-mapped THPs. This way we can avoid
1560                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1561                  *
1562                  * For anon THP:
1563                  *
1564                  * In most cases the pmd is the only mapping of the page as we
1565                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1566                  * writable private mappings in populate_vma_page_range().
1567                  *
1568                  * The only scenario when we have the page shared here is if we
1569                  * mlocking read-only mapping shared over fork(). We skip
1570                  * mlocking such pages.
1571                  *
1572                  * For file THP:
1573                  *
1574                  * We can expect PageDoubleMap() to be stable under page lock:
1575                  * for file pages we set it in page_add_file_rmap(), which
1576                  * requires page to be locked.
1577                  */
1578
1579                 if (PageAnon(page) && compound_mapcount(page) != 1)
1580                         goto skip_mlock;
1581                 if (PageDoubleMap(page) || !page->mapping)
1582                         goto skip_mlock;
1583                 if (!trylock_page(page))
1584                         goto skip_mlock;
1585                 lru_add_drain();
1586                 if (page->mapping && !PageDoubleMap(page))
1587                         mlock_vma_page(page);
1588                 unlock_page(page);
1589         }
1590 skip_mlock:
1591         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1592         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1593
1594 out:
1595         return page;
1596 }
1597
1598 /* NUMA hinting page fault entry point for trans huge pmds */
1599 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1600 {
1601         struct vm_area_struct *vma = vmf->vma;
1602         struct anon_vma *anon_vma = NULL;
1603         struct page *page;
1604         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1605         int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1606         int target_nid, last_cpupid = -1;
1607         bool page_locked;
1608         bool migrated = false;
1609         bool was_writable;
1610         int flags = 0;
1611
1612         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1613         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1614                 goto out_unlock;
1615
1616         /*
1617          * If there are potential migrations, wait for completion and retry
1618          * without disrupting NUMA hinting information. Do not relock and
1619          * check_same as the page may no longer be mapped.
1620          */
1621         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1622                 page = pmd_page(*vmf->pmd);
1623                 if (!get_page_unless_zero(page))
1624                         goto out_unlock;
1625                 spin_unlock(vmf->ptl);
1626                 put_and_wait_on_page_locked(page);
1627                 goto out;
1628         }
1629
1630         page = pmd_page(pmd);
1631         BUG_ON(is_huge_zero_page(page));
1632         page_nid = page_to_nid(page);
1633         last_cpupid = page_cpupid_last(page);
1634         count_vm_numa_event(NUMA_HINT_FAULTS);
1635         if (page_nid == this_nid) {
1636                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1637                 flags |= TNF_FAULT_LOCAL;
1638         }
1639
1640         /* See similar comment in do_numa_page for explanation */
1641         if (!pmd_savedwrite(pmd))
1642                 flags |= TNF_NO_GROUP;
1643
1644         /*
1645          * Acquire the page lock to serialise THP migrations but avoid dropping
1646          * page_table_lock if at all possible
1647          */
1648         page_locked = trylock_page(page);
1649         target_nid = mpol_misplaced(page, vma, haddr);
1650         if (target_nid == NUMA_NO_NODE) {
1651                 /* If the page was locked, there are no parallel migrations */
1652                 if (page_locked)
1653                         goto clear_pmdnuma;
1654         }
1655
1656         /* Migration could have started since the pmd_trans_migrating check */
1657         if (!page_locked) {
1658                 page_nid = NUMA_NO_NODE;
1659                 if (!get_page_unless_zero(page))
1660                         goto out_unlock;
1661                 spin_unlock(vmf->ptl);
1662                 put_and_wait_on_page_locked(page);
1663                 goto out;
1664         }
1665
1666         /*
1667          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1668          * to serialises splits
1669          */
1670         get_page(page);
1671         spin_unlock(vmf->ptl);
1672         anon_vma = page_lock_anon_vma_read(page);
1673
1674         /* Confirm the PMD did not change while page_table_lock was released */
1675         spin_lock(vmf->ptl);
1676         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1677                 unlock_page(page);
1678                 put_page(page);
1679                 page_nid = NUMA_NO_NODE;
1680                 goto out_unlock;
1681         }
1682
1683         /* Bail if we fail to protect against THP splits for any reason */
1684         if (unlikely(!anon_vma)) {
1685                 put_page(page);
1686                 page_nid = NUMA_NO_NODE;
1687                 goto clear_pmdnuma;
1688         }
1689
1690         /*
1691          * Since we took the NUMA fault, we must have observed the !accessible
1692          * bit. Make sure all other CPUs agree with that, to avoid them
1693          * modifying the page we're about to migrate.
1694          *
1695          * Must be done under PTL such that we'll observe the relevant
1696          * inc_tlb_flush_pending().
1697          *
1698          * We are not sure a pending tlb flush here is for a huge page
1699          * mapping or not. Hence use the tlb range variant
1700          */
1701         if (mm_tlb_flush_pending(vma->vm_mm)) {
1702                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1703                 /*
1704                  * change_huge_pmd() released the pmd lock before
1705                  * invalidating the secondary MMUs sharing the primary
1706                  * MMU pagetables (with ->invalidate_range()). The
1707                  * mmu_notifier_invalidate_range_end() (which
1708                  * internally calls ->invalidate_range()) in
1709                  * change_pmd_range() will run after us, so we can't
1710                  * rely on it here and we need an explicit invalidate.
1711                  */
1712                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1713                                               haddr + HPAGE_PMD_SIZE);
1714         }
1715
1716         /*
1717          * Migrate the THP to the requested node, returns with page unlocked
1718          * and access rights restored.
1719          */
1720         spin_unlock(vmf->ptl);
1721
1722         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1723                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1724         if (migrated) {
1725                 flags |= TNF_MIGRATED;
1726                 page_nid = target_nid;
1727         } else
1728                 flags |= TNF_MIGRATE_FAIL;
1729
1730         goto out;
1731 clear_pmdnuma:
1732         BUG_ON(!PageLocked(page));
1733         was_writable = pmd_savedwrite(pmd);
1734         pmd = pmd_modify(pmd, vma->vm_page_prot);
1735         pmd = pmd_mkyoung(pmd);
1736         if (was_writable)
1737                 pmd = pmd_mkwrite(pmd);
1738         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1739         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1740         unlock_page(page);
1741 out_unlock:
1742         spin_unlock(vmf->ptl);
1743
1744 out:
1745         if (anon_vma)
1746                 page_unlock_anon_vma_read(anon_vma);
1747
1748         if (page_nid != NUMA_NO_NODE)
1749                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1750                                 flags);
1751
1752         return 0;
1753 }
1754
1755 /*
1756  * Return true if we do MADV_FREE successfully on entire pmd page.
1757  * Otherwise, return false.
1758  */
1759 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1760                 pmd_t *pmd, unsigned long addr, unsigned long next)
1761 {
1762         spinlock_t *ptl;
1763         pmd_t orig_pmd;
1764         struct page *page;
1765         struct mm_struct *mm = tlb->mm;
1766         bool ret = false;
1767
1768         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1769
1770         ptl = pmd_trans_huge_lock(pmd, vma);
1771         if (!ptl)
1772                 goto out_unlocked;
1773
1774         orig_pmd = *pmd;
1775         if (is_huge_zero_pmd(orig_pmd))
1776                 goto out;
1777
1778         if (unlikely(!pmd_present(orig_pmd))) {
1779                 VM_BUG_ON(thp_migration_supported() &&
1780                                   !is_pmd_migration_entry(orig_pmd));
1781                 goto out;
1782         }
1783
1784         page = pmd_page(orig_pmd);
1785         /*
1786          * If other processes are mapping this page, we couldn't discard
1787          * the page unless they all do MADV_FREE so let's skip the page.
1788          */
1789         if (page_mapcount(page) != 1)
1790                 goto out;
1791
1792         if (!trylock_page(page))
1793                 goto out;
1794
1795         /*
1796          * If user want to discard part-pages of THP, split it so MADV_FREE
1797          * will deactivate only them.
1798          */
1799         if (next - addr != HPAGE_PMD_SIZE) {
1800                 get_page(page);
1801                 spin_unlock(ptl);
1802                 split_huge_page(page);
1803                 unlock_page(page);
1804                 put_page(page);
1805                 goto out_unlocked;
1806         }
1807
1808         if (PageDirty(page))
1809                 ClearPageDirty(page);
1810         unlock_page(page);
1811
1812         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1813                 pmdp_invalidate(vma, addr, pmd);
1814                 orig_pmd = pmd_mkold(orig_pmd);
1815                 orig_pmd = pmd_mkclean(orig_pmd);
1816
1817                 set_pmd_at(mm, addr, pmd, orig_pmd);
1818                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1819         }
1820
1821         mark_page_lazyfree(page);
1822         ret = true;
1823 out:
1824         spin_unlock(ptl);
1825 out_unlocked:
1826         return ret;
1827 }
1828
1829 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1830 {
1831         pgtable_t pgtable;
1832
1833         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1834         pte_free(mm, pgtable);
1835         mm_dec_nr_ptes(mm);
1836 }
1837
1838 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1839                  pmd_t *pmd, unsigned long addr)
1840 {
1841         pmd_t orig_pmd;
1842         spinlock_t *ptl;
1843
1844         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1845
1846         ptl = __pmd_trans_huge_lock(pmd, vma);
1847         if (!ptl)
1848                 return 0;
1849         /*
1850          * For architectures like ppc64 we look at deposited pgtable
1851          * when calling pmdp_huge_get_and_clear. So do the
1852          * pgtable_trans_huge_withdraw after finishing pmdp related
1853          * operations.
1854          */
1855         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1856                         tlb->fullmm);
1857         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1858         if (vma_is_special_huge(vma)) {
1859                 if (arch_needs_pgtable_deposit())
1860                         zap_deposited_table(tlb->mm, pmd);
1861                 spin_unlock(ptl);
1862                 if (is_huge_zero_pmd(orig_pmd))
1863                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1864         } else if (is_huge_zero_pmd(orig_pmd)) {
1865                 zap_deposited_table(tlb->mm, pmd);
1866                 spin_unlock(ptl);
1867                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1868         } else {
1869                 struct page *page = NULL;
1870                 int flush_needed = 1;
1871
1872                 if (pmd_present(orig_pmd)) {
1873                         page = pmd_page(orig_pmd);
1874                         page_remove_rmap(page, true);
1875                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1876                         VM_BUG_ON_PAGE(!PageHead(page), page);
1877                 } else if (thp_migration_supported()) {
1878                         swp_entry_t entry;
1879
1880                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1881                         entry = pmd_to_swp_entry(orig_pmd);
1882                         page = pfn_to_page(swp_offset(entry));
1883                         flush_needed = 0;
1884                 } else
1885                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1886
1887                 if (PageAnon(page)) {
1888                         zap_deposited_table(tlb->mm, pmd);
1889                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1890                 } else {
1891                         if (arch_needs_pgtable_deposit())
1892                                 zap_deposited_table(tlb->mm, pmd);
1893                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1894                 }
1895
1896                 spin_unlock(ptl);
1897                 if (flush_needed)
1898                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1899         }
1900         return 1;
1901 }
1902
1903 #ifndef pmd_move_must_withdraw
1904 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1905                                          spinlock_t *old_pmd_ptl,
1906                                          struct vm_area_struct *vma)
1907 {
1908         /*
1909          * With split pmd lock we also need to move preallocated
1910          * PTE page table if new_pmd is on different PMD page table.
1911          *
1912          * We also don't deposit and withdraw tables for file pages.
1913          */
1914         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1915 }
1916 #endif
1917
1918 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1919 {
1920 #ifdef CONFIG_MEM_SOFT_DIRTY
1921         if (unlikely(is_pmd_migration_entry(pmd)))
1922                 pmd = pmd_swp_mksoft_dirty(pmd);
1923         else if (pmd_present(pmd))
1924                 pmd = pmd_mksoft_dirty(pmd);
1925 #endif
1926         return pmd;
1927 }
1928
1929 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1930                   unsigned long new_addr, unsigned long old_end,
1931                   pmd_t *old_pmd, pmd_t *new_pmd)
1932 {
1933         spinlock_t *old_ptl, *new_ptl;
1934         pmd_t pmd;
1935         struct mm_struct *mm = vma->vm_mm;
1936         bool force_flush = false;
1937
1938         if ((old_addr & ~HPAGE_PMD_MASK) ||
1939             (new_addr & ~HPAGE_PMD_MASK) ||
1940             old_end - old_addr < HPAGE_PMD_SIZE)
1941                 return false;
1942
1943         /*
1944          * The destination pmd shouldn't be established, free_pgtables()
1945          * should have release it.
1946          */
1947         if (WARN_ON(!pmd_none(*new_pmd))) {
1948                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1949                 return false;
1950         }
1951
1952         /*
1953          * We don't have to worry about the ordering of src and dst
1954          * ptlocks because exclusive mmap_sem prevents deadlock.
1955          */
1956         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1957         if (old_ptl) {
1958                 new_ptl = pmd_lockptr(mm, new_pmd);
1959                 if (new_ptl != old_ptl)
1960                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1961                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1962                 if (pmd_present(pmd))
1963                         force_flush = true;
1964                 VM_BUG_ON(!pmd_none(*new_pmd));
1965
1966                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1967                         pgtable_t pgtable;
1968                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1969                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1970                 }
1971                 pmd = move_soft_dirty_pmd(pmd);
1972                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1973                 if (force_flush)
1974                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1975                 if (new_ptl != old_ptl)
1976                         spin_unlock(new_ptl);
1977                 spin_unlock(old_ptl);
1978                 return true;
1979         }
1980         return false;
1981 }
1982
1983 /*
1984  * Returns
1985  *  - 0 if PMD could not be locked
1986  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1987  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1988  */
1989 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1990                 unsigned long addr, pgprot_t newprot, unsigned long cp_flags)
1991 {
1992         struct mm_struct *mm = vma->vm_mm;
1993         spinlock_t *ptl;
1994         pmd_t entry;
1995         bool preserve_write;
1996         int ret;
1997         bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
1998         bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
1999         bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
2000
2001         ptl = __pmd_trans_huge_lock(pmd, vma);
2002         if (!ptl)
2003                 return 0;
2004
2005         preserve_write = prot_numa && pmd_write(*pmd);
2006         ret = 1;
2007
2008 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2009         if (is_swap_pmd(*pmd)) {
2010                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
2011
2012                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
2013                 if (is_write_migration_entry(entry)) {
2014                         pmd_t newpmd;
2015                         /*
2016                          * A protection check is difficult so
2017                          * just be safe and disable write
2018                          */
2019                         make_migration_entry_read(&entry);
2020                         newpmd = swp_entry_to_pmd(entry);
2021                         if (pmd_swp_soft_dirty(*pmd))
2022                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
2023                         set_pmd_at(mm, addr, pmd, newpmd);
2024                 }
2025                 goto unlock;
2026         }
2027 #endif
2028
2029         /*
2030          * Avoid trapping faults against the zero page. The read-only
2031          * data is likely to be read-cached on the local CPU and
2032          * local/remote hits to the zero page are not interesting.
2033          */
2034         if (prot_numa && is_huge_zero_pmd(*pmd))
2035                 goto unlock;
2036
2037         if (prot_numa && pmd_protnone(*pmd))
2038                 goto unlock;
2039
2040         /*
2041          * In case prot_numa, we are under down_read(mmap_sem). It's critical
2042          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
2043          * which is also under down_read(mmap_sem):
2044          *
2045          *      CPU0:                           CPU1:
2046          *                              change_huge_pmd(prot_numa=1)
2047          *                               pmdp_huge_get_and_clear_notify()
2048          * madvise_dontneed()
2049          *  zap_pmd_range()
2050          *   pmd_trans_huge(*pmd) == 0 (without ptl)
2051          *   // skip the pmd
2052          *                               set_pmd_at();
2053          *                               // pmd is re-established
2054          *
2055          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
2056          * which may break userspace.
2057          *
2058          * pmdp_invalidate() is required to make sure we don't miss
2059          * dirty/young flags set by hardware.
2060          */
2061         entry = pmdp_invalidate(vma, addr, pmd);
2062
2063         entry = pmd_modify(entry, newprot);
2064         if (preserve_write)
2065                 entry = pmd_mk_savedwrite(entry);
2066         if (uffd_wp) {
2067                 entry = pmd_wrprotect(entry);
2068                 entry = pmd_mkuffd_wp(entry);
2069         } else if (uffd_wp_resolve) {
2070                 /*
2071                  * Leave the write bit to be handled by PF interrupt
2072                  * handler, then things like COW could be properly
2073                  * handled.
2074                  */
2075                 entry = pmd_clear_uffd_wp(entry);
2076         }
2077         ret = HPAGE_PMD_NR;
2078         set_pmd_at(mm, addr, pmd, entry);
2079         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
2080 unlock:
2081         spin_unlock(ptl);
2082         return ret;
2083 }
2084
2085 /*
2086  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
2087  *
2088  * Note that if it returns page table lock pointer, this routine returns without
2089  * unlocking page table lock. So callers must unlock it.
2090  */
2091 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
2092 {
2093         spinlock_t *ptl;
2094         ptl = pmd_lock(vma->vm_mm, pmd);
2095         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2096                         pmd_devmap(*pmd)))
2097                 return ptl;
2098         spin_unlock(ptl);
2099         return NULL;
2100 }
2101
2102 /*
2103  * Returns true if a given pud maps a thp, false otherwise.
2104  *
2105  * Note that if it returns true, this routine returns without unlocking page
2106  * table lock. So callers must unlock it.
2107  */
2108 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2109 {
2110         spinlock_t *ptl;
2111
2112         ptl = pud_lock(vma->vm_mm, pud);
2113         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2114                 return ptl;
2115         spin_unlock(ptl);
2116         return NULL;
2117 }
2118
2119 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2120 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2121                  pud_t *pud, unsigned long addr)
2122 {
2123         spinlock_t *ptl;
2124
2125         ptl = __pud_trans_huge_lock(pud, vma);
2126         if (!ptl)
2127                 return 0;
2128         /*
2129          * For architectures like ppc64 we look at deposited pgtable
2130          * when calling pudp_huge_get_and_clear. So do the
2131          * pgtable_trans_huge_withdraw after finishing pudp related
2132          * operations.
2133          */
2134         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2135         tlb_remove_pud_tlb_entry(tlb, pud, addr);
2136         if (vma_is_special_huge(vma)) {
2137                 spin_unlock(ptl);
2138                 /* No zero page support yet */
2139         } else {
2140                 /* No support for anonymous PUD pages yet */
2141                 BUG();
2142         }
2143         return 1;
2144 }
2145
2146 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2147                 unsigned long haddr)
2148 {
2149         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2150         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2151         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2152         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2153
2154         count_vm_event(THP_SPLIT_PUD);
2155
2156         pudp_huge_clear_flush_notify(vma, haddr, pud);
2157 }
2158
2159 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2160                 unsigned long address)
2161 {
2162         spinlock_t *ptl;
2163         struct mmu_notifier_range range;
2164
2165         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2166                                 address & HPAGE_PUD_MASK,
2167                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2168         mmu_notifier_invalidate_range_start(&range);
2169         ptl = pud_lock(vma->vm_mm, pud);
2170         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2171                 goto out;
2172         __split_huge_pud_locked(vma, pud, range.start);
2173
2174 out:
2175         spin_unlock(ptl);
2176         /*
2177          * No need to double call mmu_notifier->invalidate_range() callback as
2178          * the above pudp_huge_clear_flush_notify() did already call it.
2179          */
2180         mmu_notifier_invalidate_range_only_end(&range);
2181 }
2182 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2183
2184 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2185                 unsigned long haddr, pmd_t *pmd)
2186 {
2187         struct mm_struct *mm = vma->vm_mm;
2188         pgtable_t pgtable;
2189         pmd_t _pmd;
2190         int i;
2191
2192         /*
2193          * Leave pmd empty until pte is filled note that it is fine to delay
2194          * notification until mmu_notifier_invalidate_range_end() as we are
2195          * replacing a zero pmd write protected page with a zero pte write
2196          * protected page.
2197          *
2198          * See Documentation/vm/mmu_notifier.rst
2199          */
2200         pmdp_huge_clear_flush(vma, haddr, pmd);
2201
2202         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2203         pmd_populate(mm, &_pmd, pgtable);
2204
2205         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2206                 pte_t *pte, entry;
2207                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2208                 entry = pte_mkspecial(entry);
2209                 pte = pte_offset_map(&_pmd, haddr);
2210                 VM_BUG_ON(!pte_none(*pte));
2211                 set_pte_at(mm, haddr, pte, entry);
2212                 pte_unmap(pte);
2213         }
2214         smp_wmb(); /* make pte visible before pmd */
2215         pmd_populate(mm, pmd, pgtable);
2216 }
2217
2218 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2219                 unsigned long haddr, bool freeze)
2220 {
2221         struct mm_struct *mm = vma->vm_mm;
2222         struct page *page;
2223         pgtable_t pgtable;
2224         pmd_t old_pmd, _pmd;
2225         bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
2226         unsigned long addr;
2227         int i;
2228
2229         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2230         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2231         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2232         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2233                                 && !pmd_devmap(*pmd));
2234
2235         count_vm_event(THP_SPLIT_PMD);
2236
2237         if (!vma_is_anonymous(vma)) {
2238                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2239                 /*
2240                  * We are going to unmap this huge page. So
2241                  * just go ahead and zap it
2242                  */
2243                 if (arch_needs_pgtable_deposit())
2244                         zap_deposited_table(mm, pmd);
2245                 if (vma_is_special_huge(vma))
2246                         return;
2247                 page = pmd_page(_pmd);
2248                 if (!PageDirty(page) && pmd_dirty(_pmd))
2249                         set_page_dirty(page);
2250                 if (!PageReferenced(page) && pmd_young(_pmd))
2251                         SetPageReferenced(page);
2252                 page_remove_rmap(page, true);
2253                 put_page(page);
2254                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2255                 return;
2256         } else if (is_huge_zero_pmd(*pmd)) {
2257                 /*
2258                  * FIXME: Do we want to invalidate secondary mmu by calling
2259                  * mmu_notifier_invalidate_range() see comments below inside
2260                  * __split_huge_pmd() ?
2261                  *
2262                  * We are going from a zero huge page write protected to zero
2263                  * small page also write protected so it does not seems useful
2264                  * to invalidate secondary mmu at this time.
2265                  */
2266                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2267         }
2268
2269         /*
2270          * Up to this point the pmd is present and huge and userland has the
2271          * whole access to the hugepage during the split (which happens in
2272          * place). If we overwrite the pmd with the not-huge version pointing
2273          * to the pte here (which of course we could if all CPUs were bug
2274          * free), userland could trigger a small page size TLB miss on the
2275          * small sized TLB while the hugepage TLB entry is still established in
2276          * the huge TLB. Some CPU doesn't like that.
2277          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2278          * 383 on page 93. Intel should be safe but is also warns that it's
2279          * only safe if the permission and cache attributes of the two entries
2280          * loaded in the two TLB is identical (which should be the case here).
2281          * But it is generally safer to never allow small and huge TLB entries
2282          * for the same virtual address to be loaded simultaneously. So instead
2283          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2284          * current pmd notpresent (atomically because here the pmd_trans_huge
2285          * must remain set at all times on the pmd until the split is complete
2286          * for this pmd), then we flush the SMP TLB and finally we write the
2287          * non-huge version of the pmd entry with pmd_populate.
2288          */
2289         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2290
2291         pmd_migration = is_pmd_migration_entry(old_pmd);
2292         if (unlikely(pmd_migration)) {
2293                 swp_entry_t entry;
2294
2295                 entry = pmd_to_swp_entry(old_pmd);
2296                 page = pfn_to_page(swp_offset(entry));
2297                 write = is_write_migration_entry(entry);
2298                 young = false;
2299                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2300                 uffd_wp = pmd_swp_uffd_wp(old_pmd);
2301         } else {
2302                 page = pmd_page(old_pmd);
2303                 if (pmd_dirty(old_pmd))
2304                         SetPageDirty(page);
2305                 write = pmd_write(old_pmd);
2306                 young = pmd_young(old_pmd);
2307                 soft_dirty = pmd_soft_dirty(old_pmd);
2308                 uffd_wp = pmd_uffd_wp(old_pmd);
2309         }
2310         VM_BUG_ON_PAGE(!page_count(page), page);
2311         page_ref_add(page, HPAGE_PMD_NR - 1);
2312
2313         /*
2314          * Withdraw the table only after we mark the pmd entry invalid.
2315          * This's critical for some architectures (Power).
2316          */
2317         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2318         pmd_populate(mm, &_pmd, pgtable);
2319
2320         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2321                 pte_t entry, *pte;
2322                 /*
2323                  * Note that NUMA hinting access restrictions are not
2324                  * transferred to avoid any possibility of altering
2325                  * permissions across VMAs.
2326                  */
2327                 if (freeze || pmd_migration) {
2328                         swp_entry_t swp_entry;
2329                         swp_entry = make_migration_entry(page + i, write);
2330                         entry = swp_entry_to_pte(swp_entry);
2331                         if (soft_dirty)
2332                                 entry = pte_swp_mksoft_dirty(entry);
2333                         if (uffd_wp)
2334                                 entry = pte_swp_mkuffd_wp(entry);
2335                 } else {
2336                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2337                         entry = maybe_mkwrite(entry, vma);
2338                         if (!write)
2339                                 entry = pte_wrprotect(entry);
2340                         if (!young)
2341                                 entry = pte_mkold(entry);
2342                         if (soft_dirty)
2343                                 entry = pte_mksoft_dirty(entry);
2344                         if (uffd_wp)
2345                                 entry = pte_mkuffd_wp(entry);
2346                 }
2347                 pte = pte_offset_map(&_pmd, addr);
2348                 BUG_ON(!pte_none(*pte));
2349                 set_pte_at(mm, addr, pte, entry);
2350                 atomic_inc(&page[i]._mapcount);
2351                 pte_unmap(pte);
2352         }
2353
2354         /*
2355          * Set PG_double_map before dropping compound_mapcount to avoid
2356          * false-negative page_mapped().
2357          */
2358         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2359                 for (i = 0; i < HPAGE_PMD_NR; i++)
2360                         atomic_inc(&page[i]._mapcount);
2361         }
2362
2363         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2364                 /* Last compound_mapcount is gone. */
2365                 __dec_node_page_state(page, NR_ANON_THPS);
2366                 if (TestClearPageDoubleMap(page)) {
2367                         /* No need in mapcount reference anymore */
2368                         for (i = 0; i < HPAGE_PMD_NR; i++)
2369                                 atomic_dec(&page[i]._mapcount);
2370                 }
2371         }
2372
2373         smp_wmb(); /* make pte visible before pmd */
2374         pmd_populate(mm, pmd, pgtable);
2375
2376         if (freeze) {
2377                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2378                         page_remove_rmap(page + i, false);
2379                         put_page(page + i);
2380                 }
2381         }
2382 }
2383
2384 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2385                 unsigned long address, bool freeze, struct page *page)
2386 {
2387         spinlock_t *ptl;
2388         struct mmu_notifier_range range;
2389
2390         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2391                                 address & HPAGE_PMD_MASK,
2392                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2393         mmu_notifier_invalidate_range_start(&range);
2394         ptl = pmd_lock(vma->vm_mm, pmd);
2395
2396         /*
2397          * If caller asks to setup a migration entries, we need a page to check
2398          * pmd against. Otherwise we can end up replacing wrong page.
2399          */
2400         VM_BUG_ON(freeze && !page);
2401         if (page && page != pmd_page(*pmd))
2402                 goto out;
2403
2404         if (pmd_trans_huge(*pmd)) {
2405                 page = pmd_page(*pmd);
2406                 if (PageMlocked(page))
2407                         clear_page_mlock(page);
2408         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2409                 goto out;
2410         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2411 out:
2412         spin_unlock(ptl);
2413         /*
2414          * No need to double call mmu_notifier->invalidate_range() callback.
2415          * They are 3 cases to consider inside __split_huge_pmd_locked():
2416          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2417          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2418          *    fault will trigger a flush_notify before pointing to a new page
2419          *    (it is fine if the secondary mmu keeps pointing to the old zero
2420          *    page in the meantime)
2421          *  3) Split a huge pmd into pte pointing to the same page. No need
2422          *     to invalidate secondary tlb entry they are all still valid.
2423          *     any further changes to individual pte will notify. So no need
2424          *     to call mmu_notifier->invalidate_range()
2425          */
2426         mmu_notifier_invalidate_range_only_end(&range);
2427 }
2428
2429 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2430                 bool freeze, struct page *page)
2431 {
2432         pgd_t *pgd;
2433         p4d_t *p4d;
2434         pud_t *pud;
2435         pmd_t *pmd;
2436
2437         pgd = pgd_offset(vma->vm_mm, address);
2438         if (!pgd_present(*pgd))
2439                 return;
2440
2441         p4d = p4d_offset(pgd, address);
2442         if (!p4d_present(*p4d))
2443                 return;
2444
2445         pud = pud_offset(p4d, address);
2446         if (!pud_present(*pud))
2447                 return;
2448
2449         pmd = pmd_offset(pud, address);
2450
2451         __split_huge_pmd(vma, pmd, address, freeze, page);
2452 }
2453
2454 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2455                              unsigned long start,
2456                              unsigned long end,
2457                              long adjust_next)
2458 {
2459         /*
2460          * If the new start address isn't hpage aligned and it could
2461          * previously contain an hugepage: check if we need to split
2462          * an huge pmd.
2463          */
2464         if (start & ~HPAGE_PMD_MASK &&
2465             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2466             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2467                 split_huge_pmd_address(vma, start, false, NULL);
2468
2469         /*
2470          * If the new end address isn't hpage aligned and it could
2471          * previously contain an hugepage: check if we need to split
2472          * an huge pmd.
2473          */
2474         if (end & ~HPAGE_PMD_MASK &&
2475             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2476             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2477                 split_huge_pmd_address(vma, end, false, NULL);
2478
2479         /*
2480          * If we're also updating the vma->vm_next->vm_start, if the new
2481          * vm_next->vm_start isn't page aligned and it could previously
2482          * contain an hugepage: check if we need to split an huge pmd.
2483          */
2484         if (adjust_next > 0) {
2485                 struct vm_area_struct *next = vma->vm_next;
2486                 unsigned long nstart = next->vm_start;
2487                 nstart += adjust_next << PAGE_SHIFT;
2488                 if (nstart & ~HPAGE_PMD_MASK &&
2489                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2490                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2491                         split_huge_pmd_address(next, nstart, false, NULL);
2492         }
2493 }
2494
2495 static void unmap_page(struct page *page)
2496 {
2497         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2498                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2499         bool unmap_success;
2500
2501         VM_BUG_ON_PAGE(!PageHead(page), page);
2502
2503         if (PageAnon(page))
2504                 ttu_flags |= TTU_SPLIT_FREEZE;
2505
2506         unmap_success = try_to_unmap(page, ttu_flags);
2507         VM_BUG_ON_PAGE(!unmap_success, page);
2508 }
2509
2510 static void remap_page(struct page *page)
2511 {
2512         int i;
2513         if (PageTransHuge(page)) {
2514                 remove_migration_ptes(page, page, true);
2515         } else {
2516                 for (i = 0; i < HPAGE_PMD_NR; i++)
2517                         remove_migration_ptes(page + i, page + i, true);
2518         }
2519 }
2520
2521 static void __split_huge_page_tail(struct page *head, int tail,
2522                 struct lruvec *lruvec, struct list_head *list)
2523 {
2524         struct page *page_tail = head + tail;
2525
2526         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2527
2528         /*
2529          * Clone page flags before unfreezing refcount.
2530          *
2531          * After successful get_page_unless_zero() might follow flags change,
2532          * for exmaple lock_page() which set PG_waiters.
2533          */
2534         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2535         page_tail->flags |= (head->flags &
2536                         ((1L << PG_referenced) |
2537                          (1L << PG_swapbacked) |
2538                          (1L << PG_swapcache) |
2539                          (1L << PG_mlocked) |
2540                          (1L << PG_uptodate) |
2541                          (1L << PG_active) |
2542                          (1L << PG_workingset) |
2543                          (1L << PG_locked) |
2544                          (1L << PG_unevictable) |
2545                          (1L << PG_dirty)));
2546
2547         /* ->mapping in first tail page is compound_mapcount */
2548         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2549                         page_tail);
2550         page_tail->mapping = head->mapping;
2551         page_tail->index = head->index + tail;
2552
2553         /* Page flags must be visible before we make the page non-compound. */
2554         smp_wmb();
2555
2556         /*
2557          * Clear PageTail before unfreezing page refcount.
2558          *
2559          * After successful get_page_unless_zero() might follow put_page()
2560          * which needs correct compound_head().
2561          */
2562         clear_compound_head(page_tail);
2563
2564         /* Finally unfreeze refcount. Additional reference from page cache. */
2565         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2566                                           PageSwapCache(head)));
2567
2568         if (page_is_young(head))
2569                 set_page_young(page_tail);
2570         if (page_is_idle(head))
2571                 set_page_idle(page_tail);
2572
2573         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2574
2575         /*
2576          * always add to the tail because some iterators expect new
2577          * pages to show after the currently processed elements - e.g.
2578          * migrate_pages
2579          */
2580         lru_add_page_tail(head, page_tail, lruvec, list);
2581 }
2582
2583 static void __split_huge_page(struct page *page, struct list_head *list,
2584                 pgoff_t end, unsigned long flags)
2585 {
2586         struct page *head = compound_head(page);
2587         pg_data_t *pgdat = page_pgdat(head);
2588         struct lruvec *lruvec;
2589         struct address_space *swap_cache = NULL;
2590         unsigned long offset = 0;
2591         int i;
2592
2593         lruvec = mem_cgroup_page_lruvec(head, pgdat);
2594
2595         /* complete memcg works before add pages to LRU */
2596         mem_cgroup_split_huge_fixup(head);
2597
2598         if (PageAnon(head) && PageSwapCache(head)) {
2599                 swp_entry_t entry = { .val = page_private(head) };
2600
2601                 offset = swp_offset(entry);
2602                 swap_cache = swap_address_space(entry);
2603                 xa_lock(&swap_cache->i_pages);
2604         }
2605
2606         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2607                 __split_huge_page_tail(head, i, lruvec, list);
2608                 /* Some pages can be beyond i_size: drop them from page cache */
2609                 if (head[i].index >= end) {
2610                         ClearPageDirty(head + i);
2611                         __delete_from_page_cache(head + i, NULL);
2612                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2613                                 shmem_uncharge(head->mapping->host, 1);
2614                         put_page(head + i);
2615                 } else if (!PageAnon(page)) {
2616                         __xa_store(&head->mapping->i_pages, head[i].index,
2617                                         head + i, 0);
2618                 } else if (swap_cache) {
2619                         __xa_store(&swap_cache->i_pages, offset + i,
2620                                         head + i, 0);
2621                 }
2622         }
2623
2624         ClearPageCompound(head);
2625
2626         split_page_owner(head, HPAGE_PMD_ORDER);
2627
2628         /* See comment in __split_huge_page_tail() */
2629         if (PageAnon(head)) {
2630                 /* Additional pin to swap cache */
2631                 if (PageSwapCache(head)) {
2632                         page_ref_add(head, 2);
2633                         xa_unlock(&swap_cache->i_pages);
2634                 } else {
2635                         page_ref_inc(head);
2636                 }
2637         } else {
2638                 /* Additional pin to page cache */
2639                 page_ref_add(head, 2);
2640                 xa_unlock(&head->mapping->i_pages);
2641         }
2642
2643         spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2644
2645         remap_page(head);
2646
2647         for (i = 0; i < HPAGE_PMD_NR; i++) {
2648                 struct page *subpage = head + i;
2649                 if (subpage == page)
2650                         continue;
2651                 unlock_page(subpage);
2652
2653                 /*
2654                  * Subpages may be freed if there wasn't any mapping
2655                  * like if add_to_swap() is running on a lru page that
2656                  * had its mapping zapped. And freeing these pages
2657                  * requires taking the lru_lock so we do the put_page
2658                  * of the tail pages after the split is complete.
2659                  */
2660                 put_page(subpage);
2661         }
2662 }
2663
2664 int total_mapcount(struct page *page)
2665 {
2666         int i, compound, ret;
2667
2668         VM_BUG_ON_PAGE(PageTail(page), page);
2669
2670         if (likely(!PageCompound(page)))
2671                 return atomic_read(&page->_mapcount) + 1;
2672
2673         compound = compound_mapcount(page);
2674         if (PageHuge(page))
2675                 return compound;
2676         ret = compound;
2677         for (i = 0; i < HPAGE_PMD_NR; i++)
2678                 ret += atomic_read(&page[i]._mapcount) + 1;
2679         /* File pages has compound_mapcount included in _mapcount */
2680         if (!PageAnon(page))
2681                 return ret - compound * HPAGE_PMD_NR;
2682         if (PageDoubleMap(page))
2683                 ret -= HPAGE_PMD_NR;
2684         return ret;
2685 }
2686
2687 /*
2688  * This calculates accurately how many mappings a transparent hugepage
2689  * has (unlike page_mapcount() which isn't fully accurate). This full
2690  * accuracy is primarily needed to know if copy-on-write faults can
2691  * reuse the page and change the mapping to read-write instead of
2692  * copying them. At the same time this returns the total_mapcount too.
2693  *
2694  * The function returns the highest mapcount any one of the subpages
2695  * has. If the return value is one, even if different processes are
2696  * mapping different subpages of the transparent hugepage, they can
2697  * all reuse it, because each process is reusing a different subpage.
2698  *
2699  * The total_mapcount is instead counting all virtual mappings of the
2700  * subpages. If the total_mapcount is equal to "one", it tells the
2701  * caller all mappings belong to the same "mm" and in turn the
2702  * anon_vma of the transparent hugepage can become the vma->anon_vma
2703  * local one as no other process may be mapping any of the subpages.
2704  *
2705  * It would be more accurate to replace page_mapcount() with
2706  * page_trans_huge_mapcount(), however we only use
2707  * page_trans_huge_mapcount() in the copy-on-write faults where we
2708  * need full accuracy to avoid breaking page pinning, because
2709  * page_trans_huge_mapcount() is slower than page_mapcount().
2710  */
2711 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2712 {
2713         int i, ret, _total_mapcount, mapcount;
2714
2715         /* hugetlbfs shouldn't call it */
2716         VM_BUG_ON_PAGE(PageHuge(page), page);
2717
2718         if (likely(!PageTransCompound(page))) {
2719                 mapcount = atomic_read(&page->_mapcount) + 1;
2720                 if (total_mapcount)
2721                         *total_mapcount = mapcount;
2722                 return mapcount;
2723         }
2724
2725         page = compound_head(page);
2726
2727         _total_mapcount = ret = 0;
2728         for (i = 0; i < HPAGE_PMD_NR; i++) {
2729                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2730                 ret = max(ret, mapcount);
2731                 _total_mapcount += mapcount;
2732         }
2733         if (PageDoubleMap(page)) {
2734                 ret -= 1;
2735                 _total_mapcount -= HPAGE_PMD_NR;
2736         }
2737         mapcount = compound_mapcount(page);
2738         ret += mapcount;
2739         _total_mapcount += mapcount;
2740         if (total_mapcount)
2741                 *total_mapcount = _total_mapcount;
2742         return ret;
2743 }
2744
2745 /* Racy check whether the huge page can be split */
2746 bool can_split_huge_page(struct page *page, int *pextra_pins)
2747 {
2748         int extra_pins;
2749
2750         /* Additional pins from page cache */
2751         if (PageAnon(page))
2752                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2753         else
2754                 extra_pins = HPAGE_PMD_NR;
2755         if (pextra_pins)
2756                 *pextra_pins = extra_pins;
2757         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2758 }
2759
2760 /*
2761  * This function splits huge page into normal pages. @page can point to any
2762  * subpage of huge page to split. Split doesn't change the position of @page.
2763  *
2764  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2765  * The huge page must be locked.
2766  *
2767  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2768  *
2769  * Both head page and tail pages will inherit mapping, flags, and so on from
2770  * the hugepage.
2771  *
2772  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2773  * they are not mapped.
2774  *
2775  * Returns 0 if the hugepage is split successfully.
2776  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2777  * us.
2778  */
2779 int split_huge_page_to_list(struct page *page, struct list_head *list)
2780 {
2781         struct page *head = compound_head(page);
2782         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2783         struct deferred_split *ds_queue = get_deferred_split_queue(head);
2784         struct anon_vma *anon_vma = NULL;
2785         struct address_space *mapping = NULL;
2786         int count, mapcount, extra_pins, ret;
2787         bool mlocked;
2788         unsigned long flags;
2789         pgoff_t end;
2790
2791         VM_BUG_ON_PAGE(is_huge_zero_page(head), head);
2792         VM_BUG_ON_PAGE(!PageLocked(head), head);
2793         VM_BUG_ON_PAGE(!PageCompound(head), head);
2794
2795         if (PageWriteback(head))
2796                 return -EBUSY;
2797
2798         if (PageAnon(head)) {
2799                 /*
2800                  * The caller does not necessarily hold an mmap_sem that would
2801                  * prevent the anon_vma disappearing so we first we take a
2802                  * reference to it and then lock the anon_vma for write. This
2803                  * is similar to page_lock_anon_vma_read except the write lock
2804                  * is taken to serialise against parallel split or collapse
2805                  * operations.
2806                  */
2807                 anon_vma = page_get_anon_vma(head);
2808                 if (!anon_vma) {
2809                         ret = -EBUSY;
2810                         goto out;
2811                 }
2812                 end = -1;
2813                 mapping = NULL;
2814                 anon_vma_lock_write(anon_vma);
2815         } else {
2816                 mapping = head->mapping;
2817
2818                 /* Truncated ? */
2819                 if (!mapping) {
2820                         ret = -EBUSY;
2821                         goto out;
2822                 }
2823
2824                 anon_vma = NULL;
2825                 i_mmap_lock_read(mapping);
2826
2827                 /*
2828                  *__split_huge_page() may need to trim off pages beyond EOF:
2829                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2830                  * which cannot be nested inside the page tree lock. So note
2831                  * end now: i_size itself may be changed at any moment, but
2832                  * head page lock is good enough to serialize the trimming.
2833                  */
2834                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2835         }
2836
2837         /*
2838          * Racy check if we can split the page, before unmap_page() will
2839          * split PMDs
2840          */
2841         if (!can_split_huge_page(head, &extra_pins)) {
2842                 ret = -EBUSY;
2843                 goto out_unlock;
2844         }
2845
2846         mlocked = PageMlocked(head);
2847         unmap_page(head);
2848         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2849
2850         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2851         if (mlocked)
2852                 lru_add_drain();
2853
2854         /* prevent PageLRU to go away from under us, and freeze lru stats */
2855         spin_lock_irqsave(&pgdata->lru_lock, flags);
2856
2857         if (mapping) {
2858                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2859
2860                 /*
2861                  * Check if the head page is present in page cache.
2862                  * We assume all tail are present too, if head is there.
2863                  */
2864                 xa_lock(&mapping->i_pages);
2865                 if (xas_load(&xas) != head)
2866                         goto fail;
2867         }
2868
2869         /* Prevent deferred_split_scan() touching ->_refcount */
2870         spin_lock(&ds_queue->split_queue_lock);
2871         count = page_count(head);
2872         mapcount = total_mapcount(head);
2873         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2874                 if (!list_empty(page_deferred_list(head))) {
2875                         ds_queue->split_queue_len--;
2876                         list_del(page_deferred_list(head));
2877                 }
2878                 spin_unlock(&ds_queue->split_queue_lock);
2879                 if (mapping) {
2880                         if (PageSwapBacked(head))
2881                                 __dec_node_page_state(head, NR_SHMEM_THPS);
2882                         else
2883                                 __dec_node_page_state(head, NR_FILE_THPS);
2884                 }
2885
2886                 __split_huge_page(page, list, end, flags);
2887                 if (PageSwapCache(head)) {
2888                         swp_entry_t entry = { .val = page_private(head) };
2889
2890                         ret = split_swap_cluster(entry);
2891                 } else
2892                         ret = 0;
2893         } else {
2894                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2895                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2896                                         mapcount, count);
2897                         if (PageTail(page))
2898                                 dump_page(head, NULL);
2899                         dump_page(page, "total_mapcount(head) > 0");
2900                         BUG();
2901                 }
2902                 spin_unlock(&ds_queue->split_queue_lock);
2903 fail:           if (mapping)
2904                         xa_unlock(&mapping->i_pages);
2905                 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2906                 remap_page(head);
2907                 ret = -EBUSY;
2908         }
2909
2910 out_unlock:
2911         if (anon_vma) {
2912                 anon_vma_unlock_write(anon_vma);
2913                 put_anon_vma(anon_vma);
2914         }
2915         if (mapping)
2916                 i_mmap_unlock_read(mapping);
2917 out:
2918         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2919         return ret;
2920 }
2921
2922 void free_transhuge_page(struct page *page)
2923 {
2924         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2925         unsigned long flags;
2926
2927         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2928         if (!list_empty(page_deferred_list(page))) {
2929                 ds_queue->split_queue_len--;
2930                 list_del(page_deferred_list(page));
2931         }
2932         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2933         free_compound_page(page);
2934 }
2935
2936 void deferred_split_huge_page(struct page *page)
2937 {
2938         struct deferred_split *ds_queue = get_deferred_split_queue(page);
2939 #ifdef CONFIG_MEMCG
2940         struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
2941 #endif
2942         unsigned long flags;
2943
2944         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2945
2946         /*
2947          * The try_to_unmap() in page reclaim path might reach here too,
2948          * this may cause a race condition to corrupt deferred split queue.
2949          * And, if page reclaim is already handling the same page, it is
2950          * unnecessary to handle it again in shrinker.
2951          *
2952          * Check PageSwapCache to determine if the page is being
2953          * handled by page reclaim since THP swap would add the page into
2954          * swap cache before calling try_to_unmap().
2955          */
2956         if (PageSwapCache(page))
2957                 return;
2958
2959         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2960         if (list_empty(page_deferred_list(page))) {
2961                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2962                 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2963                 ds_queue->split_queue_len++;
2964 #ifdef CONFIG_MEMCG
2965                 if (memcg)
2966                         memcg_set_shrinker_bit(memcg, page_to_nid(page),
2967                                                deferred_split_shrinker.id);
2968 #endif
2969         }
2970         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2971 }
2972
2973 static unsigned long deferred_split_count(struct shrinker *shrink,
2974                 struct shrink_control *sc)
2975 {
2976         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2977         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2978
2979 #ifdef CONFIG_MEMCG
2980         if (sc->memcg)
2981                 ds_queue = &sc->memcg->deferred_split_queue;
2982 #endif
2983         return READ_ONCE(ds_queue->split_queue_len);
2984 }
2985
2986 static unsigned long deferred_split_scan(struct shrinker *shrink,
2987                 struct shrink_control *sc)
2988 {
2989         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2990         struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2991         unsigned long flags;
2992         LIST_HEAD(list), *pos, *next;
2993         struct page *page;
2994         int split = 0;
2995
2996 #ifdef CONFIG_MEMCG
2997         if (sc->memcg)
2998                 ds_queue = &sc->memcg->deferred_split_queue;
2999 #endif
3000
3001         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3002         /* Take pin on all head pages to avoid freeing them under us */
3003         list_for_each_safe(pos, next, &ds_queue->split_queue) {
3004                 page = list_entry((void *)pos, struct page, mapping);
3005                 page = compound_head(page);
3006                 if (get_page_unless_zero(page)) {
3007                         list_move(page_deferred_list(page), &list);
3008                 } else {
3009                         /* We lost race with put_compound_page() */
3010                         list_del_init(page_deferred_list(page));
3011                         ds_queue->split_queue_len--;
3012                 }
3013                 if (!--sc->nr_to_scan)
3014                         break;
3015         }
3016         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3017
3018         list_for_each_safe(pos, next, &list) {
3019                 page = list_entry((void *)pos, struct page, mapping);
3020                 if (!trylock_page(page))
3021                         goto next;
3022                 /* split_huge_page() removes page from list on success */
3023                 if (!split_huge_page(page))
3024                         split++;
3025                 unlock_page(page);
3026 next:
3027                 put_page(page);
3028         }
3029
3030         spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3031         list_splice_tail(&list, &ds_queue->split_queue);
3032         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3033
3034         /*
3035          * Stop shrinker if we didn't split any page, but the queue is empty.
3036          * This can happen if pages were freed under us.
3037          */
3038         if (!split && list_empty(&ds_queue->split_queue))
3039                 return SHRINK_STOP;
3040         return split;
3041 }
3042
3043 static struct shrinker deferred_split_shrinker = {
3044         .count_objects = deferred_split_count,
3045         .scan_objects = deferred_split_scan,
3046         .seeks = DEFAULT_SEEKS,
3047         .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
3048                  SHRINKER_NONSLAB,
3049 };
3050
3051 #ifdef CONFIG_DEBUG_FS
3052 static int split_huge_pages_set(void *data, u64 val)
3053 {
3054         struct zone *zone;
3055         struct page *page;
3056         unsigned long pfn, max_zone_pfn;
3057         unsigned long total = 0, split = 0;
3058
3059         if (val != 1)
3060                 return -EINVAL;
3061
3062         for_each_populated_zone(zone) {
3063                 max_zone_pfn = zone_end_pfn(zone);
3064                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3065                         if (!pfn_valid(pfn))
3066                                 continue;
3067
3068                         page = pfn_to_page(pfn);
3069                         if (!get_page_unless_zero(page))
3070                                 continue;
3071
3072                         if (zone != page_zone(page))
3073                                 goto next;
3074
3075                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
3076                                 goto next;
3077
3078                         total++;
3079                         lock_page(page);
3080                         if (!split_huge_page(page))
3081                                 split++;
3082                         unlock_page(page);
3083 next:
3084                         put_page(page);
3085                 }
3086         }
3087
3088         pr_info("%lu of %lu THP split\n", split, total);
3089
3090         return 0;
3091 }
3092 DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3093                 "%llu\n");
3094
3095 static int __init split_huge_pages_debugfs(void)
3096 {
3097         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3098                             &split_huge_pages_fops);
3099         return 0;
3100 }
3101 late_initcall(split_huge_pages_debugfs);
3102 #endif
3103
3104 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3105 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3106                 struct page *page)
3107 {
3108         struct vm_area_struct *vma = pvmw->vma;
3109         struct mm_struct *mm = vma->vm_mm;
3110         unsigned long address = pvmw->address;
3111         pmd_t pmdval;
3112         swp_entry_t entry;
3113         pmd_t pmdswp;
3114
3115         if (!(pvmw->pmd && !pvmw->pte))
3116                 return;
3117
3118         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3119         pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
3120         if (pmd_dirty(pmdval))
3121                 set_page_dirty(page);
3122         entry = make_migration_entry(page, pmd_write(pmdval));
3123         pmdswp = swp_entry_to_pmd(entry);
3124         if (pmd_soft_dirty(pmdval))
3125                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3126         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3127         page_remove_rmap(page, true);
3128         put_page(page);
3129 }
3130
3131 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3132 {
3133         struct vm_area_struct *vma = pvmw->vma;
3134         struct mm_struct *mm = vma->vm_mm;
3135         unsigned long address = pvmw->address;
3136         unsigned long mmun_start = address & HPAGE_PMD_MASK;
3137         pmd_t pmde;
3138         swp_entry_t entry;
3139
3140         if (!(pvmw->pmd && !pvmw->pte))
3141                 return;
3142
3143         entry = pmd_to_swp_entry(*pvmw->pmd);
3144         get_page(new);
3145         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
3146         if (pmd_swp_soft_dirty(*pvmw->pmd))
3147                 pmde = pmd_mksoft_dirty(pmde);
3148         if (is_write_migration_entry(entry))
3149                 pmde = maybe_pmd_mkwrite(pmde, vma);
3150
3151         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
3152         if (PageAnon(new))
3153                 page_add_anon_rmap(new, vma, mmun_start, true);
3154         else
3155                 page_add_file_rmap(new, true);
3156         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3157         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3158                 mlock_vma_page(new);
3159         update_mmu_cache_pmd(vma, address, pvmw->pmd);
3160 }
3161 #endif