fs/dax.c

   1 /*
   2  * fs/dax.c - Direct Access filesystem code
   3  * Copyright (c) 2013-2014 Intel Corporation
   4  * Author: Matthew Wilcox <[email protected]>
   5  * Author: Ross Zwisler <[email protected]>
   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(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(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                 err = radix_tree_preload(
 337                                 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 338                 if (err) {
 339                         if (pmd_downgrade)
 340                                 put_locked_mapping_entry(mapping, index, entry);
 341                         return ERR_PTR(err);
 342                 }
 343
 344                 /*
 345                  * Besides huge zero pages the only other thing that gets
 346                  * downgraded are empty entries which don't need to be
 347                  * unmapped.
 348                  */
 349                 if (pmd_downgrade && dax_is_zero_entry(entry))
 350                         unmap_mapping_range(mapping,
 351                                 (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 352
 353                 spin_lock_irq(&mapping->tree_lock);
 354
 355                 if (pmd_downgrade) {
 356                         radix_tree_delete(&mapping->page_tree, index);
 357                         mapping->nrexceptional--;
 358                         dax_wake_mapping_entry_waiter(mapping, index, entry,
 359                                         true);
 360                 }
 361
 362                 entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
 363
 364                 err = __radix_tree_insert(&mapping->page_tree, index,
 365                                 dax_radix_order(entry), entry);
 366                 radix_tree_preload_end();
 367                 if (err) {
 368                         spin_unlock_irq(&mapping->tree_lock);
 369                         /*
 370                          * Someone already created the entry?  This is a
 371                          * normal failure when inserting PMDs in a range
 372                          * that already contains PTEs.  In that case we want
 373                          * to return -EEXIST immediately.
 374                          */
 375                         if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
 376                                 goto restart;
 377                         /*
 378                          * Our insertion of a DAX PMD entry failed, most
 379                          * likely because it collided with a PTE sized entry
 380                          * at a different index in the PMD range.  We haven't
 381                          * inserted anything into the radix tree and have no
 382                          * waiters to wake.
 383                          */
 384                         return ERR_PTR(err);
 385                 }
 386                 /* Good, we have inserted empty locked entry into the tree. */
 387                 mapping->nrexceptional++;
 388                 spin_unlock_irq(&mapping->tree_lock);
 389                 return entry;
 390         }
 391         /* Normal page in radix tree? */
 392         if (!radix_tree_exceptional_entry(entry)) {
 393                 struct page *page = entry;
 394
 395                 get_page(page);
 396                 spin_unlock_irq(&mapping->tree_lock);
 397                 lock_page(page);
 398                 /* Page got truncated? Retry... */
 399                 if (unlikely(page->mapping != mapping)) {
 400                         unlock_page(page);
 401                         put_page(page);
 402                         goto restart;
 403                 }
 404                 return page;
 405         }
 406         entry = lock_slot(mapping, slot);
 407  out_unlock:
 408         spin_unlock_irq(&mapping->tree_lock);
 409         return entry;
 410 }
 411
 412 /*
 413  * We do not necessarily hold the mapping->tree_lock when we call this
 414  * function so it is possible that 'entry' is no longer a valid item in the
 415  * radix tree.  This is okay because all we really need to do is to find the
 416  * correct waitqueue where tasks might be waiting for that old 'entry' and
 417  * wake them.
 418  */
 419 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 420                 pgoff_t index, void *entry, bool wake_all)
 421 {
 422         struct exceptional_entry_key key;
 423         wait_queue_head_t *wq;
 424
 425         wq = dax_entry_waitqueue(mapping, index, entry, &key);
 426
 427         /*
 428          * Checking for locked entry and prepare_to_wait_exclusive() happens
 429          * under mapping->tree_lock, ditto for entry handling in our callers.
 430          * So at this point all tasks that could have seen our entry locked
 431          * must be in the waitqueue and the following check will see them.
 432          */
 433         if (waitqueue_active(wq))
 434                 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
 435 }
 436
 437 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 438 {
 439         void *entry, **slot;
 440
 441         spin_lock_irq(&mapping->tree_lock);
 442         entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
 443         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 444                          !slot_locked(mapping, slot))) {
 445                 spin_unlock_irq(&mapping->tree_lock);
 446                 return;
 447         }
 448         unlock_slot(mapping, slot);
 449         spin_unlock_irq(&mapping->tree_lock);
 450         dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 451 }
 452
 453 /*
 454  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
 455  * entry to get unlocked before deleting it.
 456  */
 457 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 458 {
 459         void *entry;
 460
 461         spin_lock_irq(&mapping->tree_lock);
 462         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 463         /*
 464          * This gets called from truncate / punch_hole path. As such, the caller
 465          * must hold locks protecting against concurrent modifications of the
 466          * radix tree (usually fs-private i_mmap_sem for writing). Since the
 467          * caller has seen exceptional entry for this index, we better find it
 468          * at that index as well...
 469          */
 470         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) {
 471                 spin_unlock_irq(&mapping->tree_lock);
 472                 return 0;
 473         }
 474         radix_tree_delete(&mapping->page_tree, index);
 475         mapping->nrexceptional--;
 476         spin_unlock_irq(&mapping->tree_lock);
 477         dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 478
 479         return 1;
 480 }
 481
 482 /*
 483  * The user has performed a load from a hole in the file.  Allocating
 484  * a new page in the file would cause excessive storage usage for
 485  * workloads with sparse files.  We allocate a page cache page instead.
 486  * We'll kick it out of the page cache if it's ever written to,
 487  * otherwise it will simply fall out of the page cache under memory
 488  * pressure without ever having been dirtied.
 489  */
 490 static int dax_load_hole(struct address_space *mapping, void *entry,
 491                          struct vm_fault *vmf)
 492 {
 493         struct page *page;
 494
 495         /* Hole page already exists? Return it...  */
 496         if (!radix_tree_exceptional_entry(entry)) {
 497                 vmf->page = entry;
 498                 return VM_FAULT_LOCKED;
 499         }
 500
 501         /* This will replace locked radix tree entry with a hole page */
 502         page = find_or_create_page(mapping, vmf->pgoff,
 503                                    vmf->gfp_mask | __GFP_ZERO);
 504         if (!page) {
 505                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
 506                 return VM_FAULT_OOM;
 507         }
 508         vmf->page = page;
 509         return VM_FAULT_LOCKED;
 510 }
 511
 512 static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
 513                 struct page *to, unsigned long vaddr)
 514 {
 515         struct blk_dax_ctl dax = {
 516                 .sector = sector,
 517                 .size = size,
 518         };
 519         void *vto;
 520
 521         if (dax_map_atomic(bdev, &dax) < 0)
 522                 return PTR_ERR(dax.addr);
 523         vto = kmap_atomic(to);
 524         copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
 525         kunmap_atomic(vto);
 526         dax_unmap_atomic(bdev, &dax);
 527         return 0;
 528 }
 529
 530 /*
 531  * By this point grab_mapping_entry() has ensured that we have a locked entry
 532  * of the appropriate size so we don't have to worry about downgrading PMDs to
 533  * PTEs.  If we happen to be trying to insert a PTE and there is a PMD
 534  * already in the tree, we will skip the insertion and just dirty the PMD as
 535  * appropriate.
 536  */
 537 static void *dax_insert_mapping_entry(struct address_space *mapping,
 538                                       struct vm_fault *vmf,
 539                                       void *entry, sector_t sector,
 540                                       unsigned long flags)
 541 {
 542         struct radix_tree_root *page_tree = &mapping->page_tree;
 543         int error = 0;
 544         bool hole_fill = false;
 545         void *new_entry;
 546         pgoff_t index = vmf->pgoff;
 547
 548         if (vmf->flags & FAULT_FLAG_WRITE)
 549                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 550
 551         /* Replacing hole page with block mapping? */
 552         if (!radix_tree_exceptional_entry(entry)) {
 553                 hole_fill = true;
 554                 /*
 555                  * Unmap the page now before we remove it from page cache below.
 556                  * The page is locked so it cannot be faulted in again.
 557                  */
 558                 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
 559                                     PAGE_SIZE, 0);
 560                 error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 561                 if (error)
 562                         return ERR_PTR(error);
 563         } else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
 564                 /* replacing huge zero page with PMD block mapping */
 565                 unmap_mapping_range(mapping,
 566                         (vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
 567         }
 568
 569         spin_lock_irq(&mapping->tree_lock);
 570         new_entry = dax_radix_locked_entry(sector, flags);
 571
 572         if (hole_fill) {
 573                 __delete_from_page_cache(entry, NULL);
 574                 /* Drop pagecache reference */
 575                 put_page(entry);
 576                 error = __radix_tree_insert(page_tree, index,
 577                                 dax_radix_order(new_entry), new_entry);
 578                 if (error) {
 579                         new_entry = ERR_PTR(error);
 580                         goto unlock;
 581                 }
 582                 mapping->nrexceptional++;
 583         } else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
 584                 /*
 585                  * Only swap our new entry into the radix tree if the current
 586                  * entry is a zero page or an empty entry.  If a normal PTE or
 587                  * PMD entry is already in the tree, we leave it alone.  This
 588                  * means that if we are trying to insert a PTE and the
 589                  * existing entry is a PMD, we will just leave the PMD in the
 590                  * tree and dirty it if necessary.
 591                  */
 592                 void **slot;
 593                 void *ret;
 594
 595                 ret = __radix_tree_lookup(page_tree, index, NULL, &slot);
 596                 WARN_ON_ONCE(ret != entry);
 597                 radix_tree_replace_slot(slot, new_entry);
 598         }
 599         if (vmf->flags & FAULT_FLAG_WRITE)
 600                 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
 601  unlock:
 602         spin_unlock_irq(&mapping->tree_lock);
 603         if (hole_fill) {
 604                 radix_tree_preload_end();
 605                 /*
 606                  * We don't need hole page anymore, it has been replaced with
 607                  * locked radix tree entry now.
 608                  */
 609                 if (mapping->a_ops->freepage)
 610                         mapping->a_ops->freepage(entry);
 611                 unlock_page(entry);
 612                 put_page(entry);
 613         }
 614         return new_entry;
 615 }
 616
 617 static int dax_writeback_one(struct block_device *bdev,
 618                 struct address_space *mapping, pgoff_t index, void *entry)
 619 {
 620         struct radix_tree_root *page_tree = &mapping->page_tree;
 621         struct radix_tree_node *node;
 622         struct blk_dax_ctl dax;
 623         void **slot;
 624         int ret = 0;
 625
 626         spin_lock_irq(&mapping->tree_lock);
 627         /*
 628          * Regular page slots are stabilized by the page lock even
 629          * without the tree itself locked.  These unlocked entries
 630          * need verification under the tree lock.
 631          */
 632         if (!__radix_tree_lookup(page_tree, index, &node, &slot))
 633                 goto unlock;
 634         if (*slot != entry)
 635                 goto unlock;
 636
 637         /* another fsync thread may have already written back this entry */
 638         if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 639                 goto unlock;
 640
 641         if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
 642                                 dax_is_zero_entry(entry))) {
 643                 ret = -EIO;
 644                 goto unlock;
 645         }
 646
 647         /*
 648          * Even if dax_writeback_mapping_range() was given a wbc->range_start
 649          * in the middle of a PMD, the 'index' we are given will be aligned to
 650          * the start index of the PMD, as will the sector we pull from
 651          * 'entry'.  This allows us to flush for PMD_SIZE and not have to
 652          * worry about partial PMD writebacks.
 653          */
 654         dax.sector = dax_radix_sector(entry);
 655         dax.size = PAGE_SIZE << dax_radix_order(entry);
 656         spin_unlock_irq(&mapping->tree_lock);
 657
 658         /*
 659          * We cannot hold tree_lock while calling dax_map_atomic() because it
 660          * eventually calls cond_resched().
 661          */
 662         ret = dax_map_atomic(bdev, &dax);
 663         if (ret < 0)
 664                 return ret;
 665
 666         if (WARN_ON_ONCE(ret < dax.size)) {
 667                 ret = -EIO;
 668                 goto unmap;
 669         }
 670
 671         wb_cache_pmem(dax.addr, dax.size);
 672
 673         spin_lock_irq(&mapping->tree_lock);
 674         radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
 675         spin_unlock_irq(&mapping->tree_lock);
 676  unmap:
 677         dax_unmap_atomic(bdev, &dax);
 678         return ret;
 679
 680  unlock:
 681         spin_unlock_irq(&mapping->tree_lock);
 682         return ret;
 683 }
 684
 685 /*
 686  * Flush the mapping to the persistent domain within the byte range of [start,
 687  * end]. This is required by data integrity operations to ensure file data is
 688  * on persistent storage prior to completion of the operation.
 689  */
 690 int dax_writeback_mapping_range(struct address_space *mapping,
 691                 struct block_device *bdev, struct writeback_control *wbc)
 692 {
 693         struct inode *inode = mapping->host;
 694         pgoff_t start_index, end_index;
 695         pgoff_t indices[PAGEVEC_SIZE];
 696         struct pagevec pvec;
 697         bool done = false;
 698         int i, ret = 0;
 699
 700         if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 701                 return -EIO;
 702
 703         if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 704                 return 0;
 705
 706         start_index = wbc->range_start >> PAGE_SHIFT;
 707         end_index = wbc->range_end >> PAGE_SHIFT;
 708
 709         tag_pages_for_writeback(mapping, start_index, end_index);
 710
 711         pagevec_init(&pvec, 0);
 712         while (!done) {
 713                 pvec.nr = find_get_entries_tag(mapping, start_index,
 714                                 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
 715                                 pvec.pages, indices);
 716
 717                 if (pvec.nr == 0)
 718                         break;
 719
 720                 for (i = 0; i < pvec.nr; i++) {
 721                         if (indices[i] > end_index) {
 722                                 done = true;
 723                                 break;
 724                         }
 725
 726                         ret = dax_writeback_one(bdev, mapping, indices[i],
 727                                         pvec.pages[i]);
 728                         if (ret < 0)
 729                                 return ret;
 730                 }
 731         }
 732         return 0;
 733 }
 734 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 735
 736 static int dax_insert_mapping(struct address_space *mapping,
 737                 struct block_device *bdev, sector_t sector, size_t size,
 738                 void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
 739 {
 740         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 741         struct blk_dax_ctl dax = {
 742                 .sector = sector,
 743                 .size = size,
 744         };
 745         void *ret;
 746         void *entry = *entryp;
 747
 748         if (dax_map_atomic(bdev, &dax) < 0)
 749                 return PTR_ERR(dax.addr);
 750         dax_unmap_atomic(bdev, &dax);
 751
 752         ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
 753         if (IS_ERR(ret))
 754                 return PTR_ERR(ret);
 755         *entryp = ret;
 756
 757         return vm_insert_mixed(vma, vaddr, dax.pfn);
 758 }
 759
 760 /**
 761  * dax_pfn_mkwrite - handle first write to DAX page
 762  * @vma: The virtual memory area where the fault occurred
 763  * @vmf: The description of the fault
 764  */
 765 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 766 {
 767         struct file *file = vma->vm_file;
 768         struct address_space *mapping = file->f_mapping;
 769         void *entry;
 770         pgoff_t index = vmf->pgoff;
 771
 772         spin_lock_irq(&mapping->tree_lock);
 773         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 774         if (!entry || !radix_tree_exceptional_entry(entry))
 775                 goto out;
 776         radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
 777         put_unlocked_mapping_entry(mapping, index, entry);
 778 out:
 779         spin_unlock_irq(&mapping->tree_lock);
 780         return VM_FAULT_NOPAGE;
 781 }
 782 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
 783
 784 static bool dax_range_is_aligned(struct block_device *bdev,
 785                                  unsigned int offset, unsigned int length)
 786 {
 787         unsigned short sector_size = bdev_logical_block_size(bdev);
 788
 789         if (!IS_ALIGNED(offset, sector_size))
 790                 return false;
 791         if (!IS_ALIGNED(length, sector_size))
 792                 return false;
 793
 794         return true;
 795 }
 796
 797 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
 798                 unsigned int offset, unsigned int length)
 799 {
 800         struct blk_dax_ctl dax = {
 801                 .sector         = sector,
 802                 .size           = PAGE_SIZE,
 803         };
 804
 805         if (dax_range_is_aligned(bdev, offset, length)) {
 806                 sector_t start_sector = dax.sector + (offset >> 9);
 807
 808                 return blkdev_issue_zeroout(bdev, start_sector,
 809                                 length >> 9, GFP_NOFS, true);
 810         } else {
 811                 if (dax_map_atomic(bdev, &dax) < 0)
 812                         return PTR_ERR(dax.addr);
 813                 clear_pmem(dax.addr + offset, length);
 814                 dax_unmap_atomic(bdev, &dax);
 815         }
 816         return 0;
 817 }
 818 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 819
 820 #ifdef CONFIG_FS_IOMAP
 821 static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
 822 {
 823         return iomap->blkno + (((pos & PAGE_MASK) - iomap->offset) >> 9);
 824 }
 825
 826 static loff_t
 827 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 828                 struct iomap *iomap)
 829 {
 830         struct iov_iter *iter = data;
 831         loff_t end = pos + length, done = 0;
 832         ssize_t ret = 0;
 833
 834         if (iov_iter_rw(iter) == READ) {
 835                 end = min(end, i_size_read(inode));
 836                 if (pos >= end)
 837                         return 0;
 838
 839                 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
 840                         return iov_iter_zero(min(length, end - pos), iter);
 841         }
 842
 843         if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
 844                 return -EIO;
 845
 846         while (pos < end) {
 847                 unsigned offset = pos & (PAGE_SIZE - 1);
 848                 struct blk_dax_ctl dax = { 0 };
 849                 ssize_t map_len;
 850
 851                 dax.sector = dax_iomap_sector(iomap, pos);
 852                 dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
 853                 map_len = dax_map_atomic(iomap->bdev, &dax);
 854                 if (map_len < 0) {
 855                         ret = map_len;
 856                         break;
 857                 }
 858
 859                 dax.addr += offset;
 860                 map_len -= offset;
 861                 if (map_len > end - pos)
 862                         map_len = end - pos;
 863
 864                 if (iov_iter_rw(iter) == WRITE)
 865                         map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
 866                 else
 867                         map_len = copy_to_iter(dax.addr, map_len, iter);
 868                 dax_unmap_atomic(iomap->bdev, &dax);
 869                 if (map_len <= 0) {
 870                         ret = map_len ? map_len : -EFAULT;
 871                         break;
 872                 }
 873
 874                 pos += map_len;
 875                 length -= map_len;
 876                 done += map_len;
 877         }
 878
 879         return done ? done : ret;
 880 }
 881
 882 /**
 883  * dax_iomap_rw - Perform I/O to a DAX file
 884  * @iocb:       The control block for this I/O
 885  * @iter:       The addresses to do I/O from or to
 886  * @ops:        iomap ops passed from the file system
 887  *
 888  * This function performs read and write operations to directly mapped
 889  * persistent memory.  The callers needs to take care of read/write exclusion
 890  * and evicting any page cache pages in the region under I/O.
 891  */
 892 ssize_t
 893 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 894                 struct iomap_ops *ops)
 895 {
 896         struct address_space *mapping = iocb->ki_filp->f_mapping;
 897         struct inode *inode = mapping->host;
 898         loff_t pos = iocb->ki_pos, ret = 0, done = 0;
 899         unsigned flags = 0;
 900
 901         if (iov_iter_rw(iter) == WRITE)
 902                 flags |= IOMAP_WRITE;
 903
 904         /*
 905          * Yes, even DAX files can have page cache attached to them:  A zeroed
 906          * page is inserted into the pagecache when we have to serve a write
 907          * fault on a hole.  It should never be dirtied and can simply be
 908          * dropped from the pagecache once we get real data for the page.
 909          *
 910          * XXX: This is racy against mmap, and there's nothing we can do about
 911          * it. We'll eventually need to shift this down even further so that
 912          * we can check if we allocated blocks over a hole first.
 913          */
 914         if (mapping->nrpages) {
 915                 ret = invalidate_inode_pages2_range(mapping,
 916                                 pos >> PAGE_SHIFT,
 917                                 (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT);
 918                 WARN_ON_ONCE(ret);
 919         }
 920
 921         while (iov_iter_count(iter)) {
 922                 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
 923                                 iter, dax_iomap_actor);
 924                 if (ret <= 0)
 925                         break;
 926                 pos += ret;
 927                 done += ret;
 928         }
 929
 930         iocb->ki_pos += done;
 931         return done ? done : ret;
 932 }
 933 EXPORT_SYMBOL_GPL(dax_iomap_rw);
 934
 935 /**
 936  * dax_iomap_fault - handle a page fault on a DAX file
 937  * @vma: The virtual memory area where the fault occurred
 938  * @vmf: The description of the fault
 939  * @ops: iomap ops passed from the file system
 940  *
 941  * When a page fault occurs, filesystems may call this helper in their fault
 942  * or mkwrite handler for DAX files. Assumes the caller has done all the
 943  * necessary locking for the page fault to proceed successfully.
 944  */
 945 int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 946                         struct iomap_ops *ops)
 947 {
 948         struct address_space *mapping = vma->vm_file->f_mapping;
 949         struct inode *inode = mapping->host;
 950         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 951         loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
 952         sector_t sector;
 953         struct iomap iomap = { 0 };
 954         unsigned flags = IOMAP_FAULT;
 955         int error, major = 0;
 956         int locked_status = 0;
 957         void *entry;
 958
 959         /*
 960          * Check whether offset isn't beyond end of file now. Caller is supposed
 961          * to hold locks serializing us with truncate / punch hole so this is
 962          * a reliable test.
 963          */
 964         if (pos >= i_size_read(inode))
 965                 return VM_FAULT_SIGBUS;
 966
 967         entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 968         if (IS_ERR(entry)) {
 969                 error = PTR_ERR(entry);
 970                 goto out;
 971         }
 972
 973         if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
 974                 flags |= IOMAP_WRITE;
 975
 976         /*
 977          * Note that we don't bother to use iomap_apply here: DAX required
 978          * the file system block size to be equal the page size, which means
 979          * that we never have to deal with more than a single extent here.
 980          */
 981         error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
 982         if (error)
 983                 goto unlock_entry;
 984         if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
 985                 error = -EIO;           /* fs corruption? */
 986                 goto finish_iomap;
 987         }
 988
 989         sector = dax_iomap_sector(&iomap, pos);
 990
 991         if (vmf->cow_page) {
 992                 switch (iomap.type) {
 993                 case IOMAP_HOLE:
 994                 case IOMAP_UNWRITTEN:
 995                         clear_user_highpage(vmf->cow_page, vaddr);
 996                         break;
 997                 case IOMAP_MAPPED:
 998                         error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
 999                                         vmf->cow_page, vaddr);
1000                         break;
1001                 default:
1002                         WARN_ON_ONCE(1);
1003                         error = -EIO;
1004                         break;
1005                 }
1006
1007                 if (error)
1008                         goto finish_iomap;
1009                 if (!radix_tree_exceptional_entry(entry)) {
1010                         vmf->page = entry;
1011                         locked_status = VM_FAULT_LOCKED;
1012                 } else {
1013                         vmf->entry = entry;
1014                         locked_status = VM_FAULT_DAX_LOCKED;
1015                 }
1016                 goto finish_iomap;
1017         }
1018
1019         switch (iomap.type) {
1020         case IOMAP_MAPPED:
1021                 if (iomap.flags & IOMAP_F_NEW) {
1022                         count_vm_event(PGMAJFAULT);
1023                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1024                         major = VM_FAULT_MAJOR;
1025                 }
1026                 error = dax_insert_mapping(mapping, iomap.bdev, sector,
1027                                 PAGE_SIZE, &entry, vma, vmf);
1028                 break;
1029         case IOMAP_UNWRITTEN:
1030         case IOMAP_HOLE:
1031                 if (!(vmf->flags & FAULT_FLAG_WRITE)) {
1032                         locked_status = dax_load_hole(mapping, entry, vmf);
1033                         break;
1034                 }
1035                 /*FALLTHRU*/
1036         default:
1037                 WARN_ON_ONCE(1);
1038                 error = -EIO;
1039                 break;
1040         }
1041
1042  finish_iomap:
1043         if (ops->iomap_end) {
1044                 if (error) {
1045                         /* keep previous error */
1046                         ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
1047                                         &iomap);
1048                 } else {
1049                         error = ops->iomap_end(inode, pos, PAGE_SIZE,
1050                                         PAGE_SIZE, flags, &iomap);
1051                 }
1052         }
1053  unlock_entry:
1054         if (!locked_status || error)
1055                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
1056  out:
1057         if (error == -ENOMEM)
1058                 return VM_FAULT_OOM | major;
1059         /* -EBUSY is fine, somebody else faulted on the same PTE */
1060         if (error < 0 && error != -EBUSY)
1061                 return VM_FAULT_SIGBUS | major;
1062         if (locked_status) {
1063                 WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
1064                 return locked_status;
1065         }
1066         return VM_FAULT_NOPAGE | major;
1067 }
1068 EXPORT_SYMBOL_GPL(dax_iomap_fault);
1069
1070 #ifdef CONFIG_FS_DAX_PMD
1071 /*
1072  * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
1073  * more often than one might expect in the below functions.
1074  */
1075 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
1076
1077 static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
1078                 struct vm_fault *vmf, unsigned long address,
1079                 struct iomap *iomap, loff_t pos, bool write, void **entryp)
1080 {
1081         struct address_space *mapping = vma->vm_file->f_mapping;
1082         struct block_device *bdev = iomap->bdev;
1083         struct blk_dax_ctl dax = {
1084                 .sector = dax_iomap_sector(iomap, pos),
1085                 .size = PMD_SIZE,
1086         };
1087         long length = dax_map_atomic(bdev, &dax);
1088         void *ret;
1089
1090         if (length < 0) /* dax_map_atomic() failed */
1091                 return VM_FAULT_FALLBACK;
1092         if (length < PMD_SIZE)
1093                 goto unmap_fallback;
1094         if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
1095                 goto unmap_fallback;
1096         if (!pfn_t_devmap(dax.pfn))
1097                 goto unmap_fallback;
1098
1099         dax_unmap_atomic(bdev, &dax);
1100
1101         ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
1102                         RADIX_DAX_PMD);
1103         if (IS_ERR(ret))
1104                 return VM_FAULT_FALLBACK;
1105         *entryp = ret;
1106
1107         return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
1108
1109  unmap_fallback:
1110         dax_unmap_atomic(bdev, &dax);
1111         return VM_FAULT_FALLBACK;
1112 }
1113
1114 static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
1115                 struct vm_fault *vmf, unsigned long address,
1116                 struct iomap *iomap, void **entryp)
1117 {
1118         struct address_space *mapping = vma->vm_file->f_mapping;
1119         unsigned long pmd_addr = address & PMD_MASK;
1120         struct page *zero_page;
1121         spinlock_t *ptl;
1122         pmd_t pmd_entry;
1123         void *ret;
1124
1125         zero_page = mm_get_huge_zero_page(vma->vm_mm);
1126
1127         if (unlikely(!zero_page))
1128                 return VM_FAULT_FALLBACK;
1129
1130         ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
1131                         RADIX_DAX_PMD | RADIX_DAX_HZP);
1132         if (IS_ERR(ret))
1133                 return VM_FAULT_FALLBACK;
1134         *entryp = ret;
1135
1136         ptl = pmd_lock(vma->vm_mm, pmd);
1137         if (!pmd_none(*pmd)) {
1138                 spin_unlock(ptl);
1139                 return VM_FAULT_FALLBACK;
1140         }
1141
1142         pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
1143         pmd_entry = pmd_mkhuge(pmd_entry);
1144         set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
1145         spin_unlock(ptl);
1146         return VM_FAULT_NOPAGE;
1147 }
1148
1149 int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1150                 pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
1151 {
1152         struct address_space *mapping = vma->vm_file->f_mapping;
1153         unsigned long pmd_addr = address & PMD_MASK;
1154         bool write = flags & FAULT_FLAG_WRITE;
1155         unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
1156         struct inode *inode = mapping->host;
1157         int result = VM_FAULT_FALLBACK;
1158         struct iomap iomap = { 0 };
1159         pgoff_t max_pgoff, pgoff;
1160         struct vm_fault vmf;
1161         void *entry;
1162         loff_t pos;
1163         int error;
1164
1165         /* Fall back to PTEs if we're going to COW */
1166         if (write && !(vma->vm_flags & VM_SHARED))
1167                 goto fallback;
1168
1169         /* If the PMD would extend outside the VMA */
1170         if (pmd_addr < vma->vm_start)
1171                 goto fallback;
1172         if ((pmd_addr + PMD_SIZE) > vma->vm_end)
1173                 goto fallback;
1174
1175         /*
1176          * Check whether offset isn't beyond end of file now. Caller is
1177          * supposed to hold locks serializing us with truncate / punch hole so
1178          * this is a reliable test.
1179          */
1180         pgoff = linear_page_index(vma, pmd_addr);
1181         max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
1182
1183         if (pgoff > max_pgoff)
1184                 return VM_FAULT_SIGBUS;
1185
1186         /* If the PMD would extend beyond the file size */
1187         if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
1188                 goto fallback;
1189
1190         /*
1191          * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
1192          * PMD or a HZP entry.  If it can't (because a 4k page is already in
1193          * the tree, for instance), it will return -EEXIST and we just fall
1194          * back to 4k entries.
1195          */
1196         entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
1197         if (IS_ERR(entry))
1198                 goto fallback;
1199
1200         /*
1201          * Note that we don't use iomap_apply here.  We aren't doing I/O, only
1202          * setting up a mapping, so really we're using iomap_begin() as a way
1203          * to look up our filesystem block.
1204          */
1205         pos = (loff_t)pgoff << PAGE_SHIFT;
1206         error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
1207         if (error)
1208                 goto unlock_entry;
1209         if (iomap.offset + iomap.length < pos + PMD_SIZE)
1210                 goto finish_iomap;
1211
1212         vmf.pgoff = pgoff;
1213         vmf.flags = flags;
1214         vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
1215
1216         switch (iomap.type) {
1217         case IOMAP_MAPPED:
1218                 result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
1219                                 &iomap, pos, write, &entry);
1220                 break;
1221         case IOMAP_UNWRITTEN:
1222         case IOMAP_HOLE:
1223                 if (WARN_ON_ONCE(write))
1224                         goto finish_iomap;
1225                 result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
1226                                 &entry);
1227                 break;
1228         default:
1229                 WARN_ON_ONCE(1);
1230                 break;
1231         }
1232
1233  finish_iomap:
1234         if (ops->iomap_end) {
1235                 if (result == VM_FAULT_FALLBACK) {
1236                         ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
1237                                         &iomap);
1238                 } else {
1239                         error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
1240                                         iomap_flags, &iomap);
1241                         if (error)
1242                                 result = VM_FAULT_FALLBACK;
1243                 }
1244         }
1245  unlock_entry:
1246         put_locked_mapping_entry(mapping, pgoff, entry);
1247  fallback:
1248         if (result == VM_FAULT_FALLBACK) {
1249                 split_huge_pmd(vma, pmd, address);
1250                 count_vm_event(THP_FAULT_FALLBACK);
1251         }
1252         return result;
1253 }
1254 EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
1255 #endif /* CONFIG_FS_DAX_PMD */
1256 #endif /* CONFIG_FS_IOMAP */