fs/dax.c

   1 /*
   2  * fs/dax.c - Direct Access filesystem code
   3  * Copyright (c) 2013-2014 Intel Corporation
   4  * Author: Matthew Wilcox <matthew.r.wilcox@intel.com>
   5  * Author: Ross Zwisler <ross.zwisler@linux.intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms and conditions of the GNU General Public License,
   9  * version 2, as published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14  * more details.
  15  */
  16
  17 #include <linux/atomic.h>
  18 #include <linux/blkdev.h>
  19 #include <linux/buffer_head.h>
  20 #include <linux/dax.h>
  21 #include <linux/fs.h>
  22 #include <linux/genhd.h>
  23 #include <linux/highmem.h>
  24 #include <linux/memcontrol.h>
  25 #include <linux/mm.h>
  26 #include <linux/mutex.h>
  27 #include <linux/pagevec.h>
  28 #include <linux/pmem.h>
  29 #include <linux/sched.h>
  30 #include <linux/uio.h>
  31 #include <linux/vmstat.h>
  32 #include <linux/pfn_t.h>
  33 #include <linux/sizes.h>
  34 #include <linux/iomap.h>
  35 #include "internal.h"
  36
  37 /* We choose 4096 entries - same as per-zone page wait tables */
  38 #define DAX_WAIT_TABLE_BITS 12
  39 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
  40
  41 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
  42
  43 static int __init init_dax_wait_table(void)
  44 {
  45         int i;
  46
  47         for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
  48                 init_waitqueue_head(wait_table + i);
  49         return 0;
  50 }
  51 fs_initcall(init_dax_wait_table);
  52
  53 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
  54 {
  55         struct request_queue *q = bdev->bd_queue;
  56         long rc = -EIO;
  57
  58         dax->addr = ERR_PTR(-EIO);
  59         if (blk_queue_enter(q, true) != 0)
  60                 return rc;
  61
  62         rc = bdev_direct_access(bdev, dax);
  63         if (rc < 0) {
  64                 dax->addr = ERR_PTR(rc);
  65                 blk_queue_exit(q);
  66                 return rc;
  67         }
  68         return rc;
  69 }
  70
  71 static void dax_unmap_atomic(struct block_device *bdev,
  72                 const struct blk_dax_ctl *dax)
  73 {
  74         if (IS_ERR(dax->addr))
  75                 return;
  76         blk_queue_exit(bdev->bd_queue);
  77 }
  78
  79 static int dax_is_pmd_entry(void *entry)
  80 {
  81         return (unsigned long)entry & RADIX_DAX_PMD;
  82 }
  83
  84 static int dax_is_pte_entry(void *entry)
  85 {
  86         return !((unsigned long)entry & RADIX_DAX_PMD);
  87 }
  88
  89 static int dax_is_zero_entry(void *entry)
  90 {
  91         return (unsigned long)entry & RADIX_DAX_HZP;
  92 }
  93
  94 static int dax_is_empty_entry(void *entry)
  95 {
  96         return (unsigned long)entry & RADIX_DAX_EMPTY;
  97 }
  98
  99 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
 100 {
 101         struct page *page = alloc_pages(GFP_KERNEL, 0);
 102         struct blk_dax_ctl dax = {
 103                 .size = PAGE_SIZE,
 104                 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
 105         };
 106         long rc;
 107
 108         if (!page)
 109                 return ERR_PTR(-ENOMEM);
 110
 111         rc = dax_map_atomic(bdev, &dax);
 112         if (rc < 0)
 113                 return ERR_PTR(rc);
 114         memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
 115         dax_unmap_atomic(bdev, &dax);
 116         return page;
 117 }
 118
 119 /*
 120  * DAX radix tree locking
 121  */
 122 struct exceptional_entry_key {
 123         struct address_space *mapping;
 124         pgoff_t entry_start;
 125 };
 126
 127 struct wait_exceptional_entry_queue {
 128         wait_queue_t wait;
 129         struct exceptional_entry_key key;
 130 };
 131
 132 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 133                 pgoff_t index, void *entry, struct exceptional_entry_key *key)
 134 {
 135         unsigned long hash;
 136
 137         /*
 138          * If 'entry' is a PMD, align the 'index' that we use for the wait
 139          * queue to the start of that PMD.  This ensures that all offsets in
 140          * the range covered by the PMD map to the same bit lock.
 141          */
 142         if (dax_is_pmd_entry(entry))
 143                 index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 144
 145         key->mapping = mapping;
 146         key->entry_start = index;
 147
 148         hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
 149         return wait_table + hash;
 150 }
 151
 152 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 153                                        int sync, void *keyp)
 154 {
 155         struct exceptional_entry_key *key = keyp;
 156         struct wait_exceptional_entry_queue *ewait =
 157                 container_of(wait, struct wait_exceptional_entry_queue, wait);
 158
 159         if (key->mapping != ewait->key.mapping ||
 160             key->entry_start != ewait->key.entry_start)
 161                 return 0;
 162         return autoremove_wake_function(wait, mode, sync, NULL);
 163 }
 164
 165 /*
 166  * Check whether the given slot is locked. The function must be called with
 167  * mapping->tree_lock held
 168  */
 169 static inline int slot_locked(struct address_space *mapping, void **slot)
 170 {
 171         unsigned long entry = (unsigned long)
 172                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 173         return entry & RADIX_DAX_ENTRY_LOCK;
 174 }
 175
 176 /*
 177  * Mark the given slot is locked. The function must be called with
 178  * mapping->tree_lock held
 179  */
 180 static inline void *lock_slot(struct address_space *mapping, void **slot)
 181 {
 182         unsigned long entry = (unsigned long)
 183                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 184
 185         entry |= RADIX_DAX_ENTRY_LOCK;
 186         radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
 187         return (void *)entry;
 188 }
 189
 190 /*
 191  * Mark the given slot is unlocked. The function must be called with
 192  * mapping->tree_lock held
 193  */
 194 static inline void *unlock_slot(struct address_space *mapping, void **slot)
 195 {
 196         unsigned long entry = (unsigned long)
 197                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 198
 199         entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
 200         radix_tree_replace_slot(&mapping->page_tree, slot, (void *)entry);
 201         return (void *)entry;
 202 }
 203
 204 /*
 205  * Lookup entry in radix tree, wait for it to become unlocked if it is
 206  * exceptional entry and return it. The caller must call
 207  * put_unlocked_mapping_entry() when he decided not to lock the entry or
 208  * put_locked_mapping_entry() when he locked the entry and now wants to
 209  * unlock it.
 210  *
 211  * The function must be called with mapping->tree_lock held.
 212  */
 213 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 214                                         pgoff_t index, void ***slotp)
 215 {
 216         void *entry, **slot;
 217         struct wait_exceptional_entry_queue ewait;
 218         wait_queue_head_t *wq;
 219
 220         init_wait(&ewait.wait);
 221         ewait.wait.func = wake_exceptional_entry_func;
 222
 223         for (;;) {
 224                 entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 225                                           &slot);
 226                 if (!entry || !radix_tree_exceptional_entry(entry) ||
 227                     !slot_locked(mapping, slot)) {
 228                         if (slotp)
 229                                 *slotp = slot;
 230                         return entry;
 231                 }
 232
 233                 wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 234                 prepare_to_wait_exclusive(wq, &ewait.wait,
 235                                           TASK_UNINTERRUPTIBLE);
 236                 spin_unlock_irq(&mapping->tree_lock);
 237                 schedule();
 238                 finish_wait(wq, &ewait.wait);
 239                 spin_lock_irq(&mapping->tree_lock);
 240         }
 241 }
 242
 243 static void put_locked_mapping_entry(struct address_space *mapping,
 244                                      pgoff_t index, void *entry)
 245 {
 246         if (!radix_tree_exceptional_entry(entry)) {
 247                 unlock_page(entry);
 248                 put_page(entry);
 249         } else {
 250                 dax_unlock_mapping_entry(mapping, index);
 251         }
 252 }
 253
 254 /*
 255  * Called when we are done with radix tree entry we looked up via
 256  * get_unlocked_mapping_entry() and which we didn't lock in the end.
 257  */
 258 static void put_unlocked_mapping_entry(struct address_space *mapping,
 259                                        pgoff_t index, void *entry)
 260 {
 261         if (!radix_tree_exceptional_entry(entry))
 262                 return;
 263
 264         /* We have to wake up next waiter for the radix tree entry lock */
 265         dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 266 }
 267
 268 /*
 269  * Find radix tree entry at given index. If it points to a page, return with
 270  * the page locked. If it points to the exceptional entry, return with the
 271  * radix tree entry locked. If the radix tree doesn't contain given index,
 272  * create empty exceptional entry for the index and return with it locked.
 273  *
 274  * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
 275  * either return that locked entry or will return an error.  This error will
 276  * happen if there are any 4k entries (either zero pages or DAX entries)
 277  * within the 2MiB range that we are requesting.
 278  *
 279  * We always favor 4k entries over 2MiB entries. There isn't a flow where we
 280  * evict 4k entries in order to 'upgrade' them to a 2MiB entry.  A 2MiB
 281  * insertion will fail if it finds any 4k entries already in the tree, and a
 282  * 4k insertion will cause an existing 2MiB entry to be unmapped and
 283  * downgraded to 4k entries.  This happens for both 2MiB huge zero pages as
 284  * well as 2MiB empty entries.
 285  *
 286  * The exception to this downgrade path is for 2MiB DAX PMD entries that have
 287  * real storage backing them.  We will leave these real 2MiB DAX entries in
 288  * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
 289  *
 290  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
 291  * persistent memory the benefit is doubtful. We can add that later if we can
 292  * show it helps.
 293  */
 294 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
 295                 unsigned long size_flag)
 296 {
 297         bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
 298         void *entry, **slot;
 299
 300 restart:
 301         spin_lock_irq(&mapping->tree_lock);
 302         entry = get_unlocked_mapping_entry(mapping, index, &slot);
 303
 304         if (entry) {
 305                 if (size_flag & RADIX_DAX_PMD) {
 306                         if (!radix_tree_exceptional_entry(entry) ||
 307                             dax_is_pte_entry(entry)) {
 308                                 put_unlocked_mapping_entry(mapping, index,
 309                                                 entry);
 310                                 entry = ERR_PTR(-EEXIST);
 311                                 goto out_unlock;
 312                         }
 313                 } else { /* trying to grab a PTE entry */
 314                         if (radix_tree_exceptional_entry(entry) &&
 315                             dax_is_pmd_entry(entry) &&
 316                             (dax_is_zero_entry(entry) ||
 317                              dax_is_empty_entry(entry))) {
 318                                 pmd_downgrade = true;
 319                         }
 320                 }
 321         }
 322
 323         /* No entry for given index? Make sure radix tree is big enough. */
 324         if (!entry || pmd_downgrade) {
 325                 int err;
 326
 327                 if (pmd_downgrade) {
 328                         /*
 329                          * Make sure 'entry' remains valid while we drop
 330                          * mapping->tree_lock.
 331                          */
 332                         entry = lock_slot(mapping, slot);
 333                 }
 334
 335                 spin_unlock_irq(&mapping->tree_lock);
 336                 /*
 337                  * Besides huge zero pages the only other thing that gets
 338                  * downgraded are empty entries which don't need to be
 339                  * unmapped.
 340                  */
 341                 if (pmd_downgrade && dax_is_zero_entry(entry))
 342                         unmap_mapping_range(mapping,
 343                                 (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 344
 345                 err = radix_tree_preload(
 346                                 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 347                 if (err) {
 348                         if (pmd_downgrade)
 349                                 put_locked_mapping_entry(mapping, index, entry);
 350                         return ERR_PTR(err);
 351                 }
 352                 spin_lock_irq(&mapping->tree_lock);
 353
 354                 if (pmd_downgrade) {
 355                         radix_tree_delete(&mapping->page_tree, index);
 356                         mapping->nrexceptional--;
 357                         dax_wake_mapping_entry_waiter(mapping, index, entry,
 358                                         true);
 359                 }
 360
 361                 entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
 362
 363                 err = __radix_tree_insert(&mapping->page_tree, index,
 364                                 dax_radix_order(entry), entry);
 365                 radix_tree_preload_end();
 366                 if (err) {
 367                         spin_unlock_irq(&mapping->tree_lock);
 368                         /*
 369                          * Someone already created the entry?  This is a
 370                          * normal failure when inserting PMDs in a range
 371                          * that already contains PTEs.  In that case we want
 372                          * to return -EEXIST immediately.
 373                          */
 374                         if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 375                                 goto restart;
 376                         /*
 377                          * Our insertion of a DAX PMD entry failed, most
 378                          * likely because it collided with a PTE sized entry
 379                          * at a different index in the PMD range.  We haven't
 380                          * inserted anything into the radix tree and have no
 381                          * waiters to wake.
 382                          */
 383                         return ERR_PTR(err);
 384                 }
 385                 /* Good, we have inserted empty locked entry into the tree. */
 386                 mapping->nrexceptional++;
 387                 spin_unlock_irq(&mapping->tree_lock);
 388                 return entry;
 389         }
 390         /* Normal page in radix tree? */
 391         if (!radix_tree_exceptional_entry(entry)) {
 392                 struct page *page = entry;
 393
 394                 get_page(page);
 395                 spin_unlock_irq(&mapping->tree_lock);
 396                 lock_page(page);
 397                 /* Page got truncated? Retry... */
 398                 if (unlikely(page->mapping != mapping)) {
 399                         unlock_page(page);
 400                         put_page(page);
 401                         goto restart;
 402                 }
 403                 return page;
 404         }
 405         entry = lock_slot(mapping, slot);
 406  out_unlock:
 407         spin_unlock_irq(&mapping->tree_lock);
 408         return entry;
 409 }
 410
 411 /*
 412  * We do not necessarily hold the mapping->tree_lock when we call this
 413  * function so it is possible that 'entry' is no longer a valid item in the
 414  * radix tree.  This is okay because all we really need to do is to find the
 415  * correct waitqueue where tasks might be waiting for that old 'entry' and
 416  * wake them.
 417  */
 418 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 419                 pgoff_t index, void *entry, bool wake_all)
 420 {
 421         struct exceptional_entry_key key;
 422         wait_queue_head_t *wq;
 423
 424         wq = dax_entry_waitqueue(mapping, index, entry, &key);
 425
 426         /*
 427          * Checking for locked entry and prepare_to_wait_exclusive() happens
 428          * under mapping->tree_lock, ditto for entry handling in our callers.
 429          * So at this point all tasks that could have seen our entry locked
 430          * must be in the waitqueue and the following check will see them.
 431          */
 432         if (waitqueue_active(wq))
 433                 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
 434 }
 435
 436 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 437 {
 438         void *entry, **slot;
 439
 440         spin_lock_irq(&mapping->tree_lock);
 441         entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
 442         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 443                          !slot_locked(mapping, slot))) {
 444                 spin_unlock_irq(&mapping->tree_lock);
 445                 return;
 446         }
 447         unlock_slot(mapping, slot);
 448         spin_unlock_irq(&mapping->tree_lock);
 449         dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 450 }
 451
 452 /*
 453  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
 454  * entry to get unlocked before deleting it.
 455  */
 456 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 457 {
 458         void *entry;
 459
 460         spin_lock_irq(&mapping->tree_lock);
 461         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 462         /*
 463          * This gets called from truncate / punch_hole path. As such, the caller
 464          * must hold locks protecting against concurrent modifications of the
 465          * radix tree (usually fs-private i_mmap_sem for writing). Since the
 466          * caller has seen exceptional entry for this index, we better find it
 467          * at that index as well...
 468          */
 469         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) {
 470                 spin_unlock_irq(&mapping->tree_lock);
 471                 return 0;
 472         }
 473         radix_tree_delete(&mapping->page_tree, index);
 474         mapping->nrexceptional--;
 475         spin_unlock_irq(&mapping->tree_lock);
 476         dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 477
 478         return 1;
 479 }
 480
 481 /*
 482  * The user has performed a load from a hole in the file.  Allocating
 483  * a new page in the file would cause excessive storage usage for
 484  * workloads with sparse files.  We allocate a page cache page instead.
 485  * We'll kick it out of the page cache if it's ever written to,
 486  * otherwise it will simply fall out of the page cache under memory
 487  * pressure without ever having been dirtied.
 488  */
 489 static int dax_load_hole(struct address_space *mapping, void *entry,
 490                          struct vm_fault *vmf)
 491 {
 492         struct page *page;
 493
 494         /* Hole page already exists? Return it...  */
 495         if (!radix_tree_exceptional_entry(entry)) {
 496                 vmf->page = entry;
 497                 return VM_FAULT_LOCKED;
 498         }
 499
 500         /* This will replace locked radix tree entry with a hole page */
 501         page = find_or_create_page(mapping, vmf->pgoff,
 502                                    vmf->gfp_mask | __GFP_ZERO);
 503         if (!page) {
 504                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
 505                 return VM_FAULT_OOM;
 506         }
 507         vmf->page = page;
 508         return VM_FAULT_LOCKED;
 509 }
 510
 511 static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
 512                 struct page *to, unsigned long vaddr)
 513 {
 514         struct blk_dax_ctl dax = {
 515                 .sector = sector,
 516                 .size = size,
 517         };
 518         void *vto;
 519
 520         if (dax_map_atomic(bdev, &dax) < 0)
 521                 return PTR_ERR(dax.addr);
 522         vto = kmap_atomic(to);
 523         copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
 524         kunmap_atomic(vto);
 525         dax_unmap_atomic(bdev, &dax);
 526         return 0;
 527 }
 528
 529 /*
 530  * By this point grab_mapping_entry() has ensured that we have a locked entry
 531  * of the appropriate size so we don't have to worry about downgrading PMDs to
 532  * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
 533  * already in the tree, we will skip the insertion and just dirty the PMD as
 534  * appropriate.
 535  */
 536 static void *dax_insert_mapping_entry(struct address_space *mapping,
 537                                       struct vm_fault *vmf,
 538                                       void *entry, sector_t sector,
 539                                       unsigned long flags)
 540 {
 541         struct radix_tree_root *page_tree = &mapping->page_tree;
 542         int error = 0;
 543         bool hole_fill = false;
 544         void *new_entry;
 545         pgoff_t index = vmf->pgoff;
 546
 547         if (vmf->flags & FAULT_FLAG_WRITE)
 548                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 549
 550         /* Replacing hole page with block mapping? */
 551         if (!radix_tree_exceptional_entry(entry)) {
 552                 hole_fill = true;
 553                 /*
 554                  * Unmap the page now before we remove it from page cache below.
 555                  * The page is locked so it cannot be faulted in again.
 556                  */
 557                 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
 558                                     PAGE_SIZE, 0);
 559                 error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 560                 if (error)
 561                         return ERR_PTR(error);
 562         } else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
 563                 /* replacing huge zero page with PMD block mapping */
 564                 unmap_mapping_range(mapping,
 565                         (vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 566         }
 567
 568         spin_lock_irq(&mapping->tree_lock);
 569         new_entry = dax_radix_locked_entry(sector, flags);
 570
 571         if (hole_fill) {
 572                 __delete_from_page_cache(entry, NULL);
 573                 /* Drop pagecache reference */
 574                 put_page(entry);
 575                 error = __radix_tree_insert(page_tree, index,
 576                                 dax_radix_order(new_entry), new_entry);
 577                 if (error) {
 578                         new_entry = ERR_PTR(error);
 579                         goto unlock;
 580                 }
 581                 mapping->nrexceptional++;
 582         } else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
 583                 /*
 584                  * Only swap our new entry into the radix tree if the current
 585                  * entry is a zero page or an empty entry.  If a normal PTE or
 586                  * PMD entry is already in the tree, we leave it alone.  This
 587                  * means that if we are trying to insert a PTE and the
 588                  * existing entry is a PMD, we will just leave the PMD in the
 589                  * tree and dirty it if necessary.
 590                  */
 591                 struct radix_tree_node *node;
 592                 void **slot;
 593                 void *ret;
 594
 595                 ret = __radix_tree_lookup(page_tree, index, &node, &slot);
 596                 WARN_ON_ONCE(ret != entry);
 597                 __radix_tree_replace(page_tree, node, slot,
 598                                      new_entry, NULL, NULL);
 599         }
 600         if (vmf->flags & FAULT_FLAG_WRITE)
 601                 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
 602  unlock:
 603         spin_unlock_irq(&mapping->tree_lock);
 604         if (hole_fill) {
 605                 radix_tree_preload_end();
 606                 /*
 607                  * We don't need hole page anymore, it has been replaced with
 608                  * locked radix tree entry now.
 609                  */
 610                 if (mapping->a_ops->freepage)
 611                         mapping->a_ops->freepage(entry);
 612                 unlock_page(entry);
 613                 put_page(entry);
 614         }
 615         return new_entry;
 616 }
 617
 618 static int dax_writeback_one(struct block_device *bdev,
 619                 struct address_space *mapping, pgoff_t index, void *entry)
 620 {
 621         struct radix_tree_root *page_tree = &mapping->page_tree;
 622         struct radix_tree_node *node;
 623         struct blk_dax_ctl dax;
 624         void **slot;
 625         int ret = 0;
 626
 627         spin_lock_irq(&mapping->tree_lock);
 628         /*
 629          * Regular page slots are stabilized by the page lock even
 630          * without the tree itself locked.  These unlocked entries
 631          * need verification under the tree lock.
 632          */
 633         if (!__radix_tree_lookup(page_tree, index, &node, &slot))
 634                 goto unlock;
 635         if (*slot != entry)
 636                 goto unlock;
 637
 638         /* another fsync thread may have already written back this entry */
 639         if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 640                 goto unlock;
 641
 642         if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
 643                                 dax_is_zero_entry(entry))) {
 644                 ret = -EIO;
 645                 goto unlock;
 646         }
 647
 648         /*
 649          * Even if dax_writeback_mapping_range() was given a wbc->range_start
 650          * in the middle of a PMD, the 'index' we are given will be aligned to
 651          * the start index of the PMD, as will the sector we pull from
 652          * 'entry'.  This allows us to flush for PMD_SIZE and not have to
 653          * worry about partial PMD writebacks.
 654          */
 655         dax.sector = dax_radix_sector(entry);
 656         dax.size = PAGE_SIZE << dax_radix_order(entry);
 657         spin_unlock_irq(&mapping->tree_lock);
 658
 659         /*
 660          * We cannot hold tree_lock while calling dax_map_atomic() because it
 661          * eventually calls cond_resched().
 662          */
 663         ret = dax_map_atomic(bdev, &dax);
 664         if (ret < 0)
 665                 return ret;
 666
 667         if (WARN_ON_ONCE(ret < dax.size)) {
 668                 ret = -EIO;
 669                 goto unmap;
 670         }
 671
 672         wb_cache_pmem(dax.addr, dax.size);
 673
 674         spin_lock_irq(&mapping->tree_lock);
 675         radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
 676         spin_unlock_irq(&mapping->tree_lock);
 677  unmap:
 678         dax_unmap_atomic(bdev, &dax);
 679         return ret;
 680
 681  unlock:
 682         spin_unlock_irq(&mapping->tree_lock);
 683         return ret;
 684 }
 685
 686 /*
 687  * Flush the mapping to the persistent domain within the byte range of [start,
 688  * end]. This is required by data integrity operations to ensure file data is
 689  * on persistent storage prior to completion of the operation.
 690  */
 691 int dax_writeback_mapping_range(struct address_space *mapping,
 692                 struct block_device *bdev, struct writeback_control *wbc)
 693 {
 694         struct inode *inode = mapping->host;
 695         pgoff_t start_index, end_index;
 696         pgoff_t indices[PAGEVEC_SIZE];
 697         struct pagevec pvec;
 698         bool done = false;
 699         int i, ret = 0;
 700
 701         if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 702                 return -EIO;
 703
 704         if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 705                 return 0;
 706
 707         start_index = wbc->range_start >> PAGE_SHIFT;
 708         end_index = wbc->range_end >> PAGE_SHIFT;
 709
 710         tag_pages_for_writeback(mapping, start_index, end_index);
 711
 712         pagevec_init(&pvec, 0);
 713         while (!done) {
 714                 pvec.nr = find_get_entries_tag(mapping, start_index,
 715                                 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
 716                                 pvec.pages, indices);
 717
 718                 if (pvec.nr == 0)
 719                         break;
 720
 721                 for (i = 0; i < pvec.nr; i++) {
 722                         if (indices[i] > end_index) {
 723                                 done = true;
 724                                 break;
 725                         }
 726
 727                         ret = dax_writeback_one(bdev, mapping, indices[i],
 728                                         pvec.pages[i]);
 729                         if (ret < 0)
 730                                 return ret;
 731                 }
 732         }
 733         return 0;
 734 }
 735 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 736
 737 static int dax_insert_mapping(struct address_space *mapping,
 738                 struct block_device *bdev, sector_t sector, size_t size,
 739                 void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
 740 {
 741         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 742         struct blk_dax_ctl dax = {
 743                 .sector = sector,
 744                 .size = size,
 745         };
 746         void *ret;
 747         void *entry = *entryp;
 748
 749         if (dax_map_atomic(bdev, &dax) < 0)
 750                 return PTR_ERR(dax.addr);
 751         dax_unmap_atomic(bdev, &dax);
 752
 753         ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 754         if (IS_ERR(ret))
 755                 return PTR_ERR(ret);
 756         *entryp = ret;
 757
 758         return vm_insert_mixed(vma, vaddr, dax.pfn);
 759 }
 760
 761 /**
 762  * dax_pfn_mkwrite - handle first write to DAX page
 763  * @vma: The virtual memory area where the fault occurred
 764  * @vmf: The description of the fault
 765  */
 766 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 767 {
 768         struct file *file = vma->vm_file;
 769         struct address_space *mapping = file->f_mapping;
 770         void *entry;
 771         pgoff_t index = vmf->pgoff;
 772
 773         spin_lock_irq(&mapping->tree_lock);
 774         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 775         if (!entry || !radix_tree_exceptional_entry(entry))
 776                 goto out;
 777         radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
 778         put_unlocked_mapping_entry(mapping, index, entry);
 779 out:
 780         spin_unlock_irq(&mapping->tree_lock);
 781         return VM_FAULT_NOPAGE;
 782 }
 783 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
 784
 785 static bool dax_range_is_aligned(struct block_device *bdev,
 786                                  unsigned int offset, unsigned int length)
 787 {
 788         unsigned short sector_size = bdev_logical_block_size(bdev);
 789
 790         if (!IS_ALIGNED(offset, sector_size))
 791                 return false;
 792         if (!IS_ALIGNED(length, sector_size))
 793                 return false;
 794
 795         return true;
 796 }
 797
 798 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
 799                 unsigned int offset, unsigned int length)
 800 {
 801         struct blk_dax_ctl dax = {
 802                 .sector         = sector,
 803                 .size           = PAGE_SIZE,
 804         };
 805
 806         if (dax_range_is_aligned(bdev, offset, length)) {
 807                 sector_t start_sector = dax.sector + (offset >> 9);
 808
 809                 return blkdev_issue_zeroout(bdev, start_sector,
 810                                 length >> 9, GFP_NOFS, true);
 811         } else {
 812                 if (dax_map_atomic(bdev, &dax) < 0)
 813                         return PTR_ERR(dax.addr);
 814                 clear_pmem(dax.addr + offset, length);
 815                 dax_unmap_atomic(bdev, &dax);
 816         }
 817         return 0;
 818 }
 819 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 820
 821 #ifdef CONFIG_FS_IOMAP
 822 static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
 823 {
 824         return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
 825 }
 826
 827 static loff_t
 828 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 829                 struct iomap *iomap)
 830 {
 831         struct iov_iter *iter = data;
 832         loff_t end = pos + length, done = 0;
 833         ssize_t ret = 0;
 834
 835         if (iov_iter_rw(iter) == READ) {
 836                 end = min(end, i_size_read(inode));
 837                 if (pos >= end)
 838                         return 0;
 839
 840                 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
 841                         return iov_iter_zero(min(length, end - pos), iter);
 842         }
 843
 844         if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
 845                 return -EIO;
 846
 847         while (pos < end) {
 848                 unsigned offset = pos & (PAGE_SIZE - 1);
 849                 struct blk_dax_ctl dax = { 0 };
 850                 ssize_t map_len;
 851
 852                 dax.sector = dax_iomap_sector(iomap, pos);
 853                 dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 854                 map_len = dax_map_atomic(iomap->bdev, &dax);
 855                 if (map_len < 0) {
 856                         ret = map_len;
 857                         break;
 858                 }
 859
 860                 dax.addr += offset;
 861                 map_len -= offset;
 862                 if (map_len > end - pos)
 863                         map_len = end - pos;
 864
 865                 if (iov_iter_rw(iter) == WRITE)
 866                         map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
 867                 else
 868                         map_len = copy_to_iter(dax.addr, map_len, iter);
 869                 dax_unmap_atomic(iomap->bdev, &dax);
 870                 if (map_len <= 0) {
 871                         ret = map_len ? map_len : -EFAULT;
 872                         break;
 873                 }
 874
 875                 pos += map_len;
 876                 length -= map_len;
 877                 done += map_len;
 878         }
 879
 880         return done ? done : ret;
 881 }
 882
 883 /**
 884  * dax_iomap_rw - Perform I/O to a DAX file
 885  * @iocb:       The control block for this I/O
 886  * @iter:       The addresses to do I/O from or to
 887  * @ops:        iomap ops passed from the file system
 888  *
 889  * This function performs read and write operations to directly mapped
 890  * persistent memory.  The callers needs to take care of read/write exclusion
 891  * and evicting any page cache pages in the region under I/O.
 892  */
 893 ssize_t
 894 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 895                 struct iomap_ops *ops)
 896 {
 897         struct address_space *mapping = iocb->ki_filp->f_mapping;
 898         struct inode *inode = mapping->host;
 899         loff_t pos = iocb->ki_pos, ret = 0, done = 0;
 900         unsigned flags = 0;
 901
 902         if (iov_iter_rw(iter) == WRITE)
 903                 flags |= IOMAP_WRITE;
 904
 905         /*
 906          * Yes, even DAX files can have page cache attached to them:  A zeroed
 907          * page is inserted into the pagecache when we have to serve a write
 908          * fault on a hole.  It should never be dirtied and can simply be
 909          * dropped from the pagecache once we get real data for the page.
 910          *
 911          * XXX: This is racy against mmap, and there's nothing we can do about
 912          * it. We'll eventually need to shift this down even further so that
 913          * we can check if we allocated blocks over a hole first.
 914          */
 915         if (mapping->nrpages) {
 916                 ret = invalidate_inode_pages2_range(mapping,
 917                                 pos >> PAGE_SHIFT,
 918                                 (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT);
 919                 WARN_ON_ONCE(ret);
 920         }
 921
 922         while (iov_iter_count(iter)) {
 923                 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
 924                                 iter, dax_iomap_actor);
 925                 if (ret <= 0)
 926                         break;
 927                 pos += ret;
 928                 done += ret;
 929         }
 930
 931         iocb->ki_pos += done;
 932         return done ? done : ret;
 933 }
 934 EXPORT_SYMBOL_GPL(dax_iomap_rw);
 935
 936 /**
 937  * dax_iomap_fault - handle a page fault on a DAX file
 938  * @vma: The virtual memory area where the fault occurred
 939  * @vmf: The description of the fault
 940  * @ops: iomap ops passed from the file system
 941  *
 942  * When a page fault occurs, filesystems may call this helper in their fault
 943  * or mkwrite handler for DAX files. Assumes the caller has done all the
 944  * necessary locking for the page fault to proceed successfully.
 945  */
 946 int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 947                         struct iomap_ops *ops)
 948 {
 949         struct address_space *mapping = vma->vm_file->f_mapping;
 950         struct inode *inode = mapping->host;
 951         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 952         loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
 953         sector_t sector;
 954         struct iomap iomap = { 0 };
 955         unsigned flags = IOMAP_FAULT;
 956         int error, major = 0;
 957         int locked_status = 0;
 958         void *entry;
 959
 960         /*
 961          * Check whether offset isn't beyond end of file now. Caller is supposed
 962          * to hold locks serializing us with truncate / punch hole so this is
 963          * a reliable test.
 964          */
 965         if (pos >= i_size_read(inode))
 966                 return VM_FAULT_SIGBUS;
 967
 968         entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 969         if (IS_ERR(entry)) {
 970                 error = PTR_ERR(entry);
 971                 goto out;
 972         }
 973
 974         if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
 975                 flags |= IOMAP_WRITE;
 976
 977         /*
 978          * Note that we don't bother to use iomap_apply here: DAX required
 979          * the file system block size to be equal the page size, which means
 980          * that we never have to deal with more than a single extent here.
 981          */
 982         error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
 983         if (error)
 984                 goto unlock_entry;
 985         if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 986                 error = -EIO;           /* fs corruption? */
 987                 goto finish_iomap;
 988         }
 989
 990         sector = dax_iomap_sector(&iomap, pos);
 991
 992         if (vmf->cow_page) {
 993                 switch (iomap.type) {
 994                 case IOMAP_HOLE:
 995                 case IOMAP_UNWRITTEN:
 996                         clear_user_highpage(vmf->cow_page, vaddr);
 997                         break;
 998                 case IOMAP_MAPPED:
 999                         error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
1000                                         vmf->cow_page, vaddr);
1001                         break;
1002                 default:
1003                         WARN_ON_ONCE(1);
1004                         error = -EIO;
1005                         break;
1006                 }
1007
1008                 if (error)
1009                         goto finish_iomap;
1010                 if (!radix_tree_exceptional_entry(entry)) {
1011                         vmf->page = entry;
1012                         locked_status = VM_FAULT_LOCKED;
1013                 } else {
1014                         vmf->entry = entry;
1015                         locked_status = VM_FAULT_DAX_LOCKED;
1016                 }
1017                 goto finish_iomap;
1018         }
1019
1020         switch (iomap.type) {
1021         case IOMAP_MAPPED:
1022                 if (iomap.flags & IOMAP_F_NEW) {
1023                         count_vm_event(PGMAJFAULT);
1024                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1025                         major = VM_FAULT_MAJOR;
1026                 }
1027                 error = dax_insert_mapping(mapping, iomap.bdev, sector,
1028                                 PAGE_SIZE, &entry, vma, vmf);
1029                 break;
1030         case IOMAP_UNWRITTEN:
1031         case IOMAP_HOLE:
1032                 if (!(vmf->flags & FAULT_FLAG_WRITE)) {
1033                         locked_status = dax_load_hole(mapping, entry, vmf);
1034                         break;
1035                 }
1036                 /*FALLTHRU*/
1037         default:
1038                 WARN_ON_ONCE(1);
1039                 error = -EIO;
1040                 break;
1041         }
1042
1043  finish_iomap:
1044         if (ops->iomap_end) {
1045                 if (error) {
1046                         /* keep previous error */
1047                         ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
1048                                         &iomap);
1049                 } else {
1050                         error = ops->iomap_end(inode, pos, PAGE_SIZE,
1051                                         PAGE_SIZE, flags, &iomap);
1052                 }
1053         }
1054  unlock_entry:
1055         if (!locked_status || error)
1056                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
1057  out:
1058         if (error == -ENOMEM)
1059                 return VM_FAULT_OOM | major;
1060         /* -EBUSY is fine, somebody else faulted on the same PTE */
1061         if (error < 0 && error != -EBUSY)
1062                 return VM_FAULT_SIGBUS | major;
1063         if (locked_status) {
1064                 WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
1065                 return locked_status;
1066         }
1067         return VM_FAULT_NOPAGE | major;
1068 }
1069 EXPORT_SYMBOL_GPL(dax_iomap_fault);
1070
1071 #ifdef CONFIG_FS_DAX_PMD
1072 /*
1073  * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
1074  * more often than one might expect in the below functions.
1075  */
1076 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
1077
1078 static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
1079                 struct vm_fault *vmf, unsigned long address,
1080                 struct iomap *iomap, loff_t pos, bool write, void **entryp)
1081 {
1082         struct address_space *mapping = vma->vm_file->f_mapping;
1083         struct block_device *bdev = iomap->bdev;
1084         struct blk_dax_ctl dax = {
1085                 .sector = dax_iomap_sector(iomap, pos),
1086                 .size = PMD_SIZE,
1087         };
1088         long length = dax_map_atomic(bdev, &dax);
1089         void *ret;
1090
1091         if (length < 0) /* dax_map_atomic() failed */
1092                 return VM_FAULT_FALLBACK;
1093         if (length < PMD_SIZE)
1094                 goto unmap_fallback;
1095         if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
1096                 goto unmap_fallback;
1097         if (!pfn_t_devmap(dax.pfn))
1098                 goto unmap_fallback;
1099
1100         dax_unmap_atomic(bdev, &dax);
1101
1102         ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
1103                         RADIX_DAX_PMD);
1104         if (IS_ERR(ret))
1105                 return VM_FAULT_FALLBACK;
1106         *entryp = ret;
1107
1108         return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
1109
1110  unmap_fallback:
1111         dax_unmap_atomic(bdev, &dax);
1112         return VM_FAULT_FALLBACK;
1113 }
1114
1115 static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
1116                 struct vm_fault *vmf, unsigned long address,
1117                 struct iomap *iomap, void **entryp)
1118 {
1119         struct address_space *mapping = vma->vm_file->f_mapping;
1120         unsigned long pmd_addr = address & PMD_MASK;
1121         struct page *zero_page;
1122         spinlock_t *ptl;
1123         pmd_t pmd_entry;
1124         void *ret;
1125
1126         zero_page = mm_get_huge_zero_page(vma->vm_mm);
1127
1128         if (unlikely(!zero_page))
1129                 return VM_FAULT_FALLBACK;
1130
1131         ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
1132                         RADIX_DAX_PMD | RADIX_DAX_HZP);
1133         if (IS_ERR(ret))
1134                 return VM_FAULT_FALLBACK;
1135         *entryp = ret;
1136
1137         ptl = pmd_lock(vma->vm_mm, pmd);
1138         if (!pmd_none(*pmd)) {
1139                 spin_unlock(ptl);
1140                 return VM_FAULT_FALLBACK;
1141         }
1142
1143         pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
1144         pmd_entry = pmd_mkhuge(pmd_entry);
1145         set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
1146         spin_unlock(ptl);
1147         return VM_FAULT_NOPAGE;
1148 }
1149
1150 int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1151                 pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
1152 {
1153         struct address_space *mapping = vma->vm_file->f_mapping;
1154         unsigned long pmd_addr = address & PMD_MASK;
1155         bool write = flags & FAULT_FLAG_WRITE;
1156         unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1157         struct inode *inode = mapping->host;
1158         int result = VM_FAULT_FALLBACK;
1159         struct iomap iomap = { 0 };
1160         pgoff_t max_pgoff, pgoff;
1161         struct vm_fault vmf;
1162         void *entry;
1163         loff_t pos;
1164         int error;
1165
1166         /* Fall back to PTEs if we're going to COW */
1167         if (write && !(vma->vm_flags & VM_SHARED))
1168                 goto fallback;
1169
1170         /* If the PMD would extend outside the VMA */
1171         if (pmd_addr < vma->vm_start)
1172                 goto fallback;
1173         if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1174                 goto fallback;
1175
1176         /*
1177          * Check whether offset isn't beyond end of file now. Caller is
1178          * supposed to hold locks serializing us with truncate / punch hole so
1179          * this is a reliable test.
1180          */
1181         pgoff = linear_page_index(vma, pmd_addr);
1182         max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
1183
1184         if (pgoff > max_pgoff)
1185                 return VM_FAULT_SIGBUS;
1186
1187         /* If the PMD would extend beyond the file size */
1188         if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
1189                 goto fallback;
1190
1191         /*
1192          * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
1193          * PMD or a HZP entry.  If it can't (because a 4k page is already in
1194          * the tree, for instance), it will return -EEXIST and we just fall
1195          * back to 4k entries.
1196          */
1197         entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
1198         if (IS_ERR(entry))
1199                 goto fallback;
1200
1201         /*
1202          * Note that we don't use iomap_apply here.  We aren't doing I/O, only
1203          * setting up a mapping, so really we're using iomap_begin() as a way
1204          * to look up our filesystem block.
1205          */
1206         pos = (loff_t)pgoff << PAGE_SHIFT;
1207         error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
1208         if (error)
1209                 goto unlock_entry;
1210         if (iomap.offset + iomap.length < pos + PMD_SIZE)
1211                 goto finish_iomap;
1212
1213         vmf.pgoff = pgoff;
1214         vmf.flags = flags;
1215         vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
1216
1217         switch (iomap.type) {
1218         case IOMAP_MAPPED:
1219                 result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
1220                                 &iomap, pos, write, &entry);
1221                 break;
1222         case IOMAP_UNWRITTEN:
1223         case IOMAP_HOLE:
1224                 if (WARN_ON_ONCE(write))
1225                         goto finish_iomap;
1226                 result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
1227                                 &entry);
1228                 break;
1229         default:
1230                 WARN_ON_ONCE(1);
1231                 break;
1232         }
1233
1234  finish_iomap:
1235         if (ops->iomap_end) {
1236                 if (result == VM_FAULT_FALLBACK) {
1237                         ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
1238                                         &iomap);
1239                 } else {
1240                         error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
1241                                         iomap_flags, &iomap);
1242                         if (error)
1243                                 result = VM_FAULT_FALLBACK;
1244                 }
1245         }
1246  unlock_entry:
1247         put_locked_mapping_entry(mapping, pgoff, entry);
1248  fallback:
1249         if (result == VM_FAULT_FALLBACK) {
1250                 split_huge_pmd(vma, pmd, address);
1251                 count_vm_event(THP_FAULT_FALLBACK);
1252         }
1253         return result;
1254 }
1255 EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
1256 #endif /* CONFIG_FS_DAX_PMD */
1257 #endif /* CONFIG_FS_IOMAP */