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 /*
  38  * We use lowest available bit in exceptional entry for locking, other two
  39  * bits to determine entry type. In total 3 special bits.
  40  */
  41 #define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
  42 #define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
  43 #define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
  44 #define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
  45 #define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
  46 #define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
  47 #define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
  48                 RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
  49                 RADIX_TREE_EXCEPTIONAL_ENTRY))
  50
  51 /* We choose 4096 entries - same as per-zone page wait tables */
  52 #define DAX_WAIT_TABLE_BITS 12
  53 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
  54
  55 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
  56
  57 static int __init init_dax_wait_table(void)
  58 {
  59         int i;
  60
  61         for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
  62                 init_waitqueue_head(wait_table + i);
  63         return 0;
  64 }
  65 fs_initcall(init_dax_wait_table);
  66
  67 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
  68 {
  69         struct request_queue *q = bdev->bd_queue;
  70         long rc = -EIO;
  71
  72         dax->addr = ERR_PTR(-EIO);
  73         if (blk_queue_enter(q, true) != 0)
  74                 return rc;
  75
  76         rc = bdev_direct_access(bdev, dax);
  77         if (rc < 0) {
  78                 dax->addr = ERR_PTR(rc);
  79                 blk_queue_exit(q);
  80                 return rc;
  81         }
  82         return rc;
  83 }
  84
  85 static void dax_unmap_atomic(struct block_device *bdev,
  86                 const struct blk_dax_ctl *dax)
  87 {
  88         if (IS_ERR(dax->addr))
  89                 return;
  90         blk_queue_exit(bdev->bd_queue);
  91 }
  92
  93 struct page *read_dax_sector(struct block_device *bdev, sector_t n)
  94 {
  95         struct page *page = alloc_pages(GFP_KERNEL, 0);
  96         struct blk_dax_ctl dax = {
  97                 .size = PAGE_SIZE,
  98                 .sector = n & ~((((int) PAGE_SIZE) / 512) - 1),
  99         };
 100         long rc;
 101
 102         if (!page)
 103                 return ERR_PTR(-ENOMEM);
 104
 105         rc = dax_map_atomic(bdev, &dax);
 106         if (rc < 0)
 107                 return ERR_PTR(rc);
 108         memcpy_from_pmem(page_address(page), dax.addr, PAGE_SIZE);
 109         dax_unmap_atomic(bdev, &dax);
 110         return page;
 111 }
 112
 113 static bool buffer_written(struct buffer_head *bh)
 114 {
 115         return buffer_mapped(bh) && !buffer_unwritten(bh);
 116 }
 117
 118 static sector_t to_sector(const struct buffer_head *bh,
 119                 const struct inode *inode)
 120 {
 121         sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
 122
 123         return sector;
 124 }
 125
 126 static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 127                       loff_t start, loff_t end, get_block_t get_block,
 128                       struct buffer_head *bh)
 129 {
 130         loff_t pos = start, max = start, bh_max = start;
 131         bool hole = false;
 132         struct block_device *bdev = NULL;
 133         int rw = iov_iter_rw(iter), rc;
 134         long map_len = 0;
 135         struct blk_dax_ctl dax = {
 136                 .addr = ERR_PTR(-EIO),
 137         };
 138         unsigned blkbits = inode->i_blkbits;
 139         sector_t file_blks = (i_size_read(inode) + (1 << blkbits) - 1)
 140                                                                 >> blkbits;
 141
 142         if (rw == READ)
 143                 end = min(end, i_size_read(inode));
 144
 145         while (pos < end) {
 146                 size_t len;
 147                 if (pos == max) {
 148                         long page = pos >> PAGE_SHIFT;
 149                         sector_t block = page << (PAGE_SHIFT - blkbits);
 150                         unsigned first = pos - (block << blkbits);
 151                         long size;
 152
 153                         if (pos == bh_max) {
 154                                 bh->b_size = PAGE_ALIGN(end - pos);
 155                                 bh->b_state = 0;
 156                                 rc = get_block(inode, block, bh, rw == WRITE);
 157                                 if (rc)
 158                                         break;
 159                                 bh_max = pos - first + bh->b_size;
 160                                 bdev = bh->b_bdev;
 161                                 /*
 162                                  * We allow uninitialized buffers for writes
 163                                  * beyond EOF as those cannot race with faults
 164                                  */
 165                                 WARN_ON_ONCE(
 166                                         (buffer_new(bh) && block < file_blks) ||
 167                                         (rw == WRITE && buffer_unwritten(bh)));
 168                         } else {
 169                                 unsigned done = bh->b_size -
 170                                                 (bh_max - (pos - first));
 171                                 bh->b_blocknr += done >> blkbits;
 172                                 bh->b_size -= done;
 173                         }
 174
 175                         hole = rw == READ && !buffer_written(bh);
 176                         if (hole) {
 177                                 size = bh->b_size - first;
 178                         } else {
 179                                 dax_unmap_atomic(bdev, &dax);
 180                                 dax.sector = to_sector(bh, inode);
 181                                 dax.size = bh->b_size;
 182                                 map_len = dax_map_atomic(bdev, &dax);
 183                                 if (map_len < 0) {
 184                                         rc = map_len;
 185                                         break;
 186                                 }
 187                                 dax.addr += first;
 188                                 size = map_len - first;
 189                         }
 190                         /*
 191                          * pos + size is one past the last offset for IO,
 192                          * so pos + size can overflow loff_t at extreme offsets.
 193                          * Cast to u64 to catch this and get the true minimum.
 194                          */
 195                         max = min_t(u64, pos + size, end);
 196                 }
 197
 198                 if (iov_iter_rw(iter) == WRITE) {
 199                         len = copy_from_iter_pmem(dax.addr, max - pos, iter);
 200                 } else if (!hole)
 201                         len = copy_to_iter((void __force *) dax.addr, max - pos,
 202                                         iter);
 203                 else
 204                         len = iov_iter_zero(max - pos, iter);
 205
 206                 if (!len) {
 207                         rc = -EFAULT;
 208                         break;
 209                 }
 210
 211                 pos += len;
 212                 if (!IS_ERR(dax.addr))
 213                         dax.addr += len;
 214         }
 215
 216         dax_unmap_atomic(bdev, &dax);
 217
 218         return (pos == start) ? rc : pos - start;
 219 }
 220
 221 /**
 222  * dax_do_io - Perform I/O to a DAX file
 223  * @iocb: The control block for this I/O
 224  * @inode: The file which the I/O is directed at
 225  * @iter: The addresses to do I/O from or to
 226  * @get_block: The filesystem method used to translate file offsets to blocks
 227  * @end_io: A filesystem callback for I/O completion
 228  * @flags: See below
 229  *
 230  * This function uses the same locking scheme as do_blockdev_direct_IO:
 231  * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
 232  * caller for writes.  For reads, we take and release the i_mutex ourselves.
 233  * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
 234  * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
 235  * is in progress.
 236  */
 237 ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
 238                   struct iov_iter *iter, get_block_t get_block,
 239                   dio_iodone_t end_io, int flags)
 240 {
 241         struct buffer_head bh;
 242         ssize_t retval = -EINVAL;
 243         loff_t pos = iocb->ki_pos;
 244         loff_t end = pos + iov_iter_count(iter);
 245
 246         memset(&bh, 0, sizeof(bh));
 247         bh.b_bdev = inode->i_sb->s_bdev;
 248
 249         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
 250                 inode_lock(inode);
 251
 252         /* Protects against truncate */
 253         if (!(flags & DIO_SKIP_DIO_COUNT))
 254                 inode_dio_begin(inode);
 255
 256         retval = dax_io(inode, iter, pos, end, get_block, &bh);
 257
 258         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
 259                 inode_unlock(inode);
 260
 261         if (end_io) {
 262                 int err;
 263
 264                 err = end_io(iocb, pos, retval, bh.b_private);
 265                 if (err)
 266                         retval = err;
 267         }
 268
 269         if (!(flags & DIO_SKIP_DIO_COUNT))
 270                 inode_dio_end(inode);
 271         return retval;
 272 }
 273 EXPORT_SYMBOL_GPL(dax_do_io);
 274
 275 /*
 276  * DAX radix tree locking
 277  */
 278 struct exceptional_entry_key {
 279         struct address_space *mapping;
 280         pgoff_t entry_start;
 281 };
 282
 283 struct wait_exceptional_entry_queue {
 284         wait_queue_t wait;
 285         struct exceptional_entry_key key;
 286 };
 287
 288 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 289                 pgoff_t index, void *entry, struct exceptional_entry_key *key)
 290 {
 291         unsigned long hash;
 292
 293         /*
 294          * If 'entry' is a PMD, align the 'index' that we use for the wait
 295          * queue to the start of that PMD.  This ensures that all offsets in
 296          * the range covered by the PMD map to the same bit lock.
 297          */
 298         if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
 299                 index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
 300
 301         key->mapping = mapping;
 302         key->entry_start = index;
 303
 304         hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
 305         return wait_table + hash;
 306 }
 307
 308 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 309                                        int sync, void *keyp)
 310 {
 311         struct exceptional_entry_key *key = keyp;
 312         struct wait_exceptional_entry_queue *ewait =
 313                 container_of(wait, struct wait_exceptional_entry_queue, wait);
 314
 315         if (key->mapping != ewait->key.mapping ||
 316             key->entry_start != ewait->key.entry_start)
 317                 return 0;
 318         return autoremove_wake_function(wait, mode, sync, NULL);
 319 }
 320
 321 /*
 322  * Check whether the given slot is locked. The function must be called with
 323  * mapping->tree_lock held
 324  */
 325 static inline int slot_locked(struct address_space *mapping, void **slot)
 326 {
 327         unsigned long entry = (unsigned long)
 328                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 329         return entry & RADIX_DAX_ENTRY_LOCK;
 330 }
 331
 332 /*
 333  * Mark the given slot is locked. The function must be called with
 334  * mapping->tree_lock held
 335  */
 336 static inline void *lock_slot(struct address_space *mapping, void **slot)
 337 {
 338         unsigned long entry = (unsigned long)
 339                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 340
 341         entry |= RADIX_DAX_ENTRY_LOCK;
 342         radix_tree_replace_slot(slot, (void *)entry);
 343         return (void *)entry;
 344 }
 345
 346 /*
 347  * Mark the given slot is unlocked. The function must be called with
 348  * mapping->tree_lock held
 349  */
 350 static inline void *unlock_slot(struct address_space *mapping, void **slot)
 351 {
 352         unsigned long entry = (unsigned long)
 353                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 354
 355         entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
 356         radix_tree_replace_slot(slot, (void *)entry);
 357         return (void *)entry;
 358 }
 359
 360 /*
 361  * Lookup entry in radix tree, wait for it to become unlocked if it is
 362  * exceptional entry and return it. The caller must call
 363  * put_unlocked_mapping_entry() when he decided not to lock the entry or
 364  * put_locked_mapping_entry() when he locked the entry and now wants to
 365  * unlock it.
 366  *
 367  * The function must be called with mapping->tree_lock held.
 368  */
 369 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 370                                         pgoff_t index, void ***slotp)
 371 {
 372         void *entry, **slot;
 373         struct wait_exceptional_entry_queue ewait;
 374         wait_queue_head_t *wq;
 375
 376         init_wait(&ewait.wait);
 377         ewait.wait.func = wake_exceptional_entry_func;
 378
 379         for (;;) {
 380                 entry = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 381                                           &slot);
 382                 if (!entry || !radix_tree_exceptional_entry(entry) ||
 383                     !slot_locked(mapping, slot)) {
 384                         if (slotp)
 385                                 *slotp = slot;
 386                         return entry;
 387                 }
 388
 389                 wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
 390                 prepare_to_wait_exclusive(wq, &ewait.wait,
 391                                           TASK_UNINTERRUPTIBLE);
 392                 spin_unlock_irq(&mapping->tree_lock);
 393                 schedule();
 394                 finish_wait(wq, &ewait.wait);
 395                 spin_lock_irq(&mapping->tree_lock);
 396         }
 397 }
 398
 399 /*
 400  * Find radix tree entry at given index. If it points to a page, return with
 401  * the page locked. If it points to the exceptional entry, return with the
 402  * radix tree entry locked. If the radix tree doesn't contain given index,
 403  * create empty exceptional entry for the index and return with it locked.
 404  *
 405  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
 406  * persistent memory the benefit is doubtful. We can add that later if we can
 407  * show it helps.
 408  */
 409 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
 410 {
 411         void *entry, **slot;
 412
 413 restart:
 414         spin_lock_irq(&mapping->tree_lock);
 415         entry = get_unlocked_mapping_entry(mapping, index, &slot);
 416         /* No entry for given index? Make sure radix tree is big enough. */
 417         if (!entry) {
 418                 int err;
 419
 420                 spin_unlock_irq(&mapping->tree_lock);
 421                 err = radix_tree_preload(
 422                                 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 423                 if (err)
 424                         return ERR_PTR(err);
 425                 entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
 426                                RADIX_DAX_ENTRY_LOCK);
 427                 spin_lock_irq(&mapping->tree_lock);
 428                 err = radix_tree_insert(&mapping->page_tree, index, entry);
 429                 radix_tree_preload_end();
 430                 if (err) {
 431                         spin_unlock_irq(&mapping->tree_lock);
 432                         /* Someone already created the entry? */
 433                         if (err == -EEXIST)
 434                                 goto restart;
 435                         return ERR_PTR(err);
 436                 }
 437                 /* Good, we have inserted empty locked entry into the tree. */
 438                 mapping->nrexceptional++;
 439                 spin_unlock_irq(&mapping->tree_lock);
 440                 return entry;
 441         }
 442         /* Normal page in radix tree? */
 443         if (!radix_tree_exceptional_entry(entry)) {
 444                 struct page *page = entry;
 445
 446                 get_page(page);
 447                 spin_unlock_irq(&mapping->tree_lock);
 448                 lock_page(page);
 449                 /* Page got truncated? Retry... */
 450                 if (unlikely(page->mapping != mapping)) {
 451                         unlock_page(page);
 452                         put_page(page);
 453                         goto restart;
 454                 }
 455                 return page;
 456         }
 457         entry = lock_slot(mapping, slot);
 458         spin_unlock_irq(&mapping->tree_lock);
 459         return entry;
 460 }
 461
 462 /*
 463  * We do not necessarily hold the mapping->tree_lock when we call this
 464  * function so it is possible that 'entry' is no longer a valid item in the
 465  * radix tree.  This is okay, though, because all we really need to do is to
 466  * find the correct waitqueue where tasks might be sleeping waiting for that
 467  * old 'entry' and wake them.
 468  */
 469 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 470                 pgoff_t index, void *entry, bool wake_all)
 471 {
 472         struct exceptional_entry_key key;
 473         wait_queue_head_t *wq;
 474
 475         wq = dax_entry_waitqueue(mapping, index, entry, &key);
 476
 477         /*
 478          * Checking for locked entry and prepare_to_wait_exclusive() happens
 479          * under mapping->tree_lock, ditto for entry handling in our callers.
 480          * So at this point all tasks that could have seen our entry locked
 481          * must be in the waitqueue and the following check will see them.
 482          */
 483         if (waitqueue_active(wq))
 484                 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
 485 }
 486
 487 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 488 {
 489         void *entry, **slot;
 490
 491         spin_lock_irq(&mapping->tree_lock);
 492         entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
 493         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
 494                          !slot_locked(mapping, slot))) {
 495                 spin_unlock_irq(&mapping->tree_lock);
 496                 return;
 497         }
 498         unlock_slot(mapping, slot);
 499         spin_unlock_irq(&mapping->tree_lock);
 500         dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 501 }
 502
 503 static void put_locked_mapping_entry(struct address_space *mapping,
 504                                      pgoff_t index, void *entry)
 505 {
 506         if (!radix_tree_exceptional_entry(entry)) {
 507                 unlock_page(entry);
 508                 put_page(entry);
 509         } else {
 510                 dax_unlock_mapping_entry(mapping, index);
 511         }
 512 }
 513
 514 /*
 515  * Called when we are done with radix tree entry we looked up via
 516  * get_unlocked_mapping_entry() and which we didn't lock in the end.
 517  */
 518 static void put_unlocked_mapping_entry(struct address_space *mapping,
 519                                        pgoff_t index, void *entry)
 520 {
 521         if (!radix_tree_exceptional_entry(entry))
 522                 return;
 523
 524         /* We have to wake up next waiter for the radix tree entry lock */
 525         dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 526 }
 527
 528 /*
 529  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
 530  * entry to get unlocked before deleting it.
 531  */
 532 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 533 {
 534         void *entry;
 535
 536         spin_lock_irq(&mapping->tree_lock);
 537         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 538         /*
 539          * This gets called from truncate / punch_hole path. As such, the caller
 540          * must hold locks protecting against concurrent modifications of the
 541          * radix tree (usually fs-private i_mmap_sem for writing). Since the
 542          * caller has seen exceptional entry for this index, we better find it
 543          * at that index as well...
 544          */
 545         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) {
 546                 spin_unlock_irq(&mapping->tree_lock);
 547                 return 0;
 548         }
 549         radix_tree_delete(&mapping->page_tree, index);
 550         mapping->nrexceptional--;
 551         spin_unlock_irq(&mapping->tree_lock);
 552         dax_wake_mapping_entry_waiter(mapping, index, entry, true);
 553
 554         return 1;
 555 }
 556
 557 /*
 558  * The user has performed a load from a hole in the file.  Allocating
 559  * a new page in the file would cause excessive storage usage for
 560  * workloads with sparse files.  We allocate a page cache page instead.
 561  * We'll kick it out of the page cache if it's ever written to,
 562  * otherwise it will simply fall out of the page cache under memory
 563  * pressure without ever having been dirtied.
 564  */
 565 static int dax_load_hole(struct address_space *mapping, void *entry,
 566                          struct vm_fault *vmf)
 567 {
 568         struct page *page;
 569
 570         /* Hole page already exists? Return it...  */
 571         if (!radix_tree_exceptional_entry(entry)) {
 572                 vmf->page = entry;
 573                 return VM_FAULT_LOCKED;
 574         }
 575
 576         /* This will replace locked radix tree entry with a hole page */
 577         page = find_or_create_page(mapping, vmf->pgoff,
 578                                    vmf->gfp_mask | __GFP_ZERO);
 579         if (!page) {
 580                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
 581                 return VM_FAULT_OOM;
 582         }
 583         vmf->page = page;
 584         return VM_FAULT_LOCKED;
 585 }
 586
 587 static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
 588                 struct page *to, unsigned long vaddr)
 589 {
 590         struct blk_dax_ctl dax = {
 591                 .sector = sector,
 592                 .size = size,
 593         };
 594         void *vto;
 595
 596         if (dax_map_atomic(bdev, &dax) < 0)
 597                 return PTR_ERR(dax.addr);
 598         vto = kmap_atomic(to);
 599         copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
 600         kunmap_atomic(vto);
 601         dax_unmap_atomic(bdev, &dax);
 602         return 0;
 603 }
 604
 605 #define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
 606
 607 static void *dax_insert_mapping_entry(struct address_space *mapping,
 608                                       struct vm_fault *vmf,
 609                                       void *entry, sector_t sector)
 610 {
 611         struct radix_tree_root *page_tree = &mapping->page_tree;
 612         int error = 0;
 613         bool hole_fill = false;
 614         void *new_entry;
 615         pgoff_t index = vmf->pgoff;
 616
 617         if (vmf->flags & FAULT_FLAG_WRITE)
 618                 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
 619
 620         /* Replacing hole page with block mapping? */
 621         if (!radix_tree_exceptional_entry(entry)) {
 622                 hole_fill = true;
 623                 /*
 624                  * Unmap the page now before we remove it from page cache below.
 625                  * The page is locked so it cannot be faulted in again.
 626                  */
 627                 unmap_mapping_range(mapping, vmf->pgoff << PAGE_SHIFT,
 628                                     PAGE_SIZE, 0);
 629                 error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
 630                 if (error)
 631                         return ERR_PTR(error);
 632         }
 633
 634         spin_lock_irq(&mapping->tree_lock);
 635         new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
 636                        RADIX_DAX_ENTRY_LOCK);
 637         if (hole_fill) {
 638                 __delete_from_page_cache(entry, NULL);
 639                 /* Drop pagecache reference */
 640                 put_page(entry);
 641                 error = radix_tree_insert(page_tree, index, new_entry);
 642                 if (error) {
 643                         new_entry = ERR_PTR(error);
 644                         goto unlock;
 645                 }
 646                 mapping->nrexceptional++;
 647         } else {
 648                 void **slot;
 649                 void *ret;
 650
 651                 ret = __radix_tree_lookup(page_tree, index, NULL, &slot);
 652                 WARN_ON_ONCE(ret != entry);
 653                 radix_tree_replace_slot(slot, new_entry);
 654         }
 655         if (vmf->flags & FAULT_FLAG_WRITE)
 656                 radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
 657  unlock:
 658         spin_unlock_irq(&mapping->tree_lock);
 659         if (hole_fill) {
 660                 radix_tree_preload_end();
 661                 /*
 662                  * We don't need hole page anymore, it has been replaced with
 663                  * locked radix tree entry now.
 664                  */
 665                 if (mapping->a_ops->freepage)
 666                         mapping->a_ops->freepage(entry);
 667                 unlock_page(entry);
 668                 put_page(entry);
 669         }
 670         return new_entry;
 671 }
 672
 673 static int dax_writeback_one(struct block_device *bdev,
 674                 struct address_space *mapping, pgoff_t index, void *entry)
 675 {
 676         struct radix_tree_root *page_tree = &mapping->page_tree;
 677         int type = RADIX_DAX_TYPE(entry);
 678         struct radix_tree_node *node;
 679         struct blk_dax_ctl dax;
 680         void **slot;
 681         int ret = 0;
 682
 683         spin_lock_irq(&mapping->tree_lock);
 684         /*
 685          * Regular page slots are stabilized by the page lock even
 686          * without the tree itself locked.  These unlocked entries
 687          * need verification under the tree lock.
 688          */
 689         if (!__radix_tree_lookup(page_tree, index, &node, &slot))
 690                 goto unlock;
 691         if (*slot != entry)
 692                 goto unlock;
 693
 694         /* another fsync thread may have already written back this entry */
 695         if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
 696                 goto unlock;
 697
 698         if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
 699                 ret = -EIO;
 700                 goto unlock;
 701         }
 702
 703         dax.sector = RADIX_DAX_SECTOR(entry);
 704         dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
 705         spin_unlock_irq(&mapping->tree_lock);
 706
 707         /*
 708          * We cannot hold tree_lock while calling dax_map_atomic() because it
 709          * eventually calls cond_resched().
 710          */
 711         ret = dax_map_atomic(bdev, &dax);
 712         if (ret < 0)
 713                 return ret;
 714
 715         if (WARN_ON_ONCE(ret < dax.size)) {
 716                 ret = -EIO;
 717                 goto unmap;
 718         }
 719
 720         wb_cache_pmem(dax.addr, dax.size);
 721
 722         spin_lock_irq(&mapping->tree_lock);
 723         radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_TOWRITE);
 724         spin_unlock_irq(&mapping->tree_lock);
 725  unmap:
 726         dax_unmap_atomic(bdev, &dax);
 727         return ret;
 728
 729  unlock:
 730         spin_unlock_irq(&mapping->tree_lock);
 731         return ret;
 732 }
 733
 734 /*
 735  * Flush the mapping to the persistent domain within the byte range of [start,
 736  * end]. This is required by data integrity operations to ensure file data is
 737  * on persistent storage prior to completion of the operation.
 738  */
 739 int dax_writeback_mapping_range(struct address_space *mapping,
 740                 struct block_device *bdev, struct writeback_control *wbc)
 741 {
 742         struct inode *inode = mapping->host;
 743         pgoff_t start_index, end_index, pmd_index;
 744         pgoff_t indices[PAGEVEC_SIZE];
 745         struct pagevec pvec;
 746         bool done = false;
 747         int i, ret = 0;
 748         void *entry;
 749
 750         if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
 751                 return -EIO;
 752
 753         if (!mapping->nrexceptional || wbc->sync_mode != WB_SYNC_ALL)
 754                 return 0;
 755
 756         start_index = wbc->range_start >> PAGE_SHIFT;
 757         end_index = wbc->range_end >> PAGE_SHIFT;
 758         pmd_index = DAX_PMD_INDEX(start_index);
 759
 760         rcu_read_lock();
 761         entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
 762         rcu_read_unlock();
 763
 764         /* see if the start of our range is covered by a PMD entry */
 765         if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
 766                 start_index = pmd_index;
 767
 768         tag_pages_for_writeback(mapping, start_index, end_index);
 769
 770         pagevec_init(&pvec, 0);
 771         while (!done) {
 772                 pvec.nr = find_get_entries_tag(mapping, start_index,
 773                                 PAGECACHE_TAG_TOWRITE, PAGEVEC_SIZE,
 774                                 pvec.pages, indices);
 775
 776                 if (pvec.nr == 0)
 777                         break;
 778
 779                 for (i = 0; i < pvec.nr; i++) {
 780                         if (indices[i] > end_index) {
 781                                 done = true;
 782                                 break;
 783                         }
 784
 785                         ret = dax_writeback_one(bdev, mapping, indices[i],
 786                                         pvec.pages[i]);
 787                         if (ret < 0)
 788                                 return ret;
 789                 }
 790         }
 791         return 0;
 792 }
 793 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 794
 795 static int dax_insert_mapping(struct address_space *mapping,
 796                 struct block_device *bdev, sector_t sector, size_t size,
 797                 void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
 798 {
 799         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 800         struct blk_dax_ctl dax = {
 801                 .sector = sector,
 802                 .size = size,
 803         };
 804         void *ret;
 805         void *entry = *entryp;
 806
 807         if (dax_map_atomic(bdev, &dax) < 0)
 808                 return PTR_ERR(dax.addr);
 809         dax_unmap_atomic(bdev, &dax);
 810
 811         ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
 812         if (IS_ERR(ret))
 813                 return PTR_ERR(ret);
 814         *entryp = ret;
 815
 816         return vm_insert_mixed(vma, vaddr, dax.pfn);
 817 }
 818
 819 /**
 820  * dax_fault - handle a page fault on a DAX file
 821  * @vma: The virtual memory area where the fault occurred
 822  * @vmf: The description of the fault
 823  * @get_block: The filesystem method used to translate file offsets to blocks
 824  *
 825  * When a page fault occurs, filesystems may call this helper in their
 826  * fault handler for DAX files. dax_fault() assumes the caller has done all
 827  * the necessary locking for the page fault to proceed successfully.
 828  */
 829 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 830                         get_block_t get_block)
 831 {
 832         struct file *file = vma->vm_file;
 833         struct address_space *mapping = file->f_mapping;
 834         struct inode *inode = mapping->host;
 835         void *entry;
 836         struct buffer_head bh;
 837         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 838         unsigned blkbits = inode->i_blkbits;
 839         sector_t block;
 840         pgoff_t size;
 841         int error;
 842         int major = 0;
 843
 844         /*
 845          * Check whether offset isn't beyond end of file now. Caller is supposed
 846          * to hold locks serializing us with truncate / punch hole so this is
 847          * a reliable test.
 848          */
 849         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 850         if (vmf->pgoff >= size)
 851                 return VM_FAULT_SIGBUS;
 852
 853         memset(&bh, 0, sizeof(bh));
 854         block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
 855         bh.b_bdev = inode->i_sb->s_bdev;
 856         bh.b_size = PAGE_SIZE;
 857
 858         entry = grab_mapping_entry(mapping, vmf->pgoff);
 859         if (IS_ERR(entry)) {
 860                 error = PTR_ERR(entry);
 861                 goto out;
 862         }
 863
 864         error = get_block(inode, block, &bh, 0);
 865         if (!error && (bh.b_size < PAGE_SIZE))
 866                 error = -EIO;           /* fs corruption? */
 867         if (error)
 868                 goto unlock_entry;
 869
 870         if (vmf->cow_page) {
 871                 struct page *new_page = vmf->cow_page;
 872                 if (buffer_written(&bh))
 873                         error = copy_user_dax(bh.b_bdev, to_sector(&bh, inode),
 874                                         bh.b_size, new_page, vaddr);
 875                 else
 876                         clear_user_highpage(new_page, vaddr);
 877                 if (error)
 878                         goto unlock_entry;
 879                 if (!radix_tree_exceptional_entry(entry)) {
 880                         vmf->page = entry;
 881                         return VM_FAULT_LOCKED;
 882                 }
 883                 vmf->entry = entry;
 884                 return VM_FAULT_DAX_LOCKED;
 885         }
 886
 887         if (!buffer_mapped(&bh)) {
 888                 if (vmf->flags & FAULT_FLAG_WRITE) {
 889                         error = get_block(inode, block, &bh, 1);
 890                         count_vm_event(PGMAJFAULT);
 891                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
 892                         major = VM_FAULT_MAJOR;
 893                         if (!error && (bh.b_size < PAGE_SIZE))
 894                                 error = -EIO;
 895                         if (error)
 896                                 goto unlock_entry;
 897                 } else {
 898                         return dax_load_hole(mapping, entry, vmf);
 899                 }
 900         }
 901
 902         /* Filesystem should not return unwritten buffers to us! */
 903         WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
 904         error = dax_insert_mapping(mapping, bh.b_bdev, to_sector(&bh, inode),
 905                         bh.b_size, &entry, vma, vmf);
 906  unlock_entry:
 907         put_locked_mapping_entry(mapping, vmf->pgoff, entry);
 908  out:
 909         if (error == -ENOMEM)
 910                 return VM_FAULT_OOM | major;
 911         /* -EBUSY is fine, somebody else faulted on the same PTE */
 912         if ((error < 0) && (error != -EBUSY))
 913                 return VM_FAULT_SIGBUS | major;
 914         return VM_FAULT_NOPAGE | major;
 915 }
 916 EXPORT_SYMBOL_GPL(dax_fault);
 917
 918 /**
 919  * dax_pfn_mkwrite - handle first write to DAX page
 920  * @vma: The virtual memory area where the fault occurred
 921  * @vmf: The description of the fault
 922  */
 923 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 924 {
 925         struct file *file = vma->vm_file;
 926         struct address_space *mapping = file->f_mapping;
 927         void *entry;
 928         pgoff_t index = vmf->pgoff;
 929
 930         spin_lock_irq(&mapping->tree_lock);
 931         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 932         if (!entry || !radix_tree_exceptional_entry(entry))
 933                 goto out;
 934         radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
 935         put_unlocked_mapping_entry(mapping, index, entry);
 936 out:
 937         spin_unlock_irq(&mapping->tree_lock);
 938         return VM_FAULT_NOPAGE;
 939 }
 940 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
 941
 942 static bool dax_range_is_aligned(struct block_device *bdev,
 943                                  unsigned int offset, unsigned int length)
 944 {
 945         unsigned short sector_size = bdev_logical_block_size(bdev);
 946
 947         if (!IS_ALIGNED(offset, sector_size))
 948                 return false;
 949         if (!IS_ALIGNED(length, sector_size))
 950                 return false;
 951
 952         return true;
 953 }
 954
 955 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
 956                 unsigned int offset, unsigned int length)
 957 {
 958         struct blk_dax_ctl dax = {
 959                 .sector         = sector,
 960                 .size           = PAGE_SIZE,
 961         };
 962
 963         if (dax_range_is_aligned(bdev, offset, length)) {
 964                 sector_t start_sector = dax.sector + (offset >> 9);
 965
 966                 return blkdev_issue_zeroout(bdev, start_sector,
 967                                 length >> 9, GFP_NOFS, true);
 968         } else {
 969                 if (dax_map_atomic(bdev, &dax) < 0)
 970                         return PTR_ERR(dax.addr);
 971                 clear_pmem(dax.addr + offset, length);
 972                 dax_unmap_atomic(bdev, &dax);
 973         }
 974         return 0;
 975 }
 976 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 977
 978 /**
 979  * dax_zero_page_range - zero a range within a page of a DAX file
 980  * @inode: The file being truncated
 981  * @from: The file offset that is being truncated to
 982  * @length: The number of bytes to zero
 983  * @get_block: The filesystem method used to translate file offsets to blocks
 984  *
 985  * This function can be called by a filesystem when it is zeroing part of a
 986  * page in a DAX file.  This is intended for hole-punch operations.  If
 987  * you are truncating a file, the helper function dax_truncate_page() may be
 988  * more convenient.
 989  */
 990 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
 991                                                         get_block_t get_block)
 992 {
 993         struct buffer_head bh;
 994         pgoff_t index = from >> PAGE_SHIFT;
 995         unsigned offset = from & (PAGE_SIZE-1);
 996         int err;
 997
 998         /* Block boundary? Nothing to do */
 999         if (!length)
1000                 return 0;
1001         if (WARN_ON_ONCE((offset + length) > PAGE_SIZE))
1002                 return -EINVAL;
1003
1004         memset(&bh, 0, sizeof(bh));
1005         bh.b_bdev = inode->i_sb->s_bdev;
1006         bh.b_size = PAGE_SIZE;
1007         err = get_block(inode, index, &bh, 0);
1008         if (err < 0 || !buffer_written(&bh))
1009                 return err;
1010
1011         return __dax_zero_page_range(bh.b_bdev, to_sector(&bh, inode),
1012                         offset, length);
1013 }
1014 EXPORT_SYMBOL_GPL(dax_zero_page_range);
1015
1016 /**
1017  * dax_truncate_page - handle a partial page being truncated in a DAX file
1018  * @inode: The file being truncated
1019  * @from: The file offset that is being truncated to
1020  * @get_block: The filesystem method used to translate file offsets to blocks
1021  *
1022  * Similar to block_truncate_page(), this function can be called by a
1023  * filesystem when it is truncating a DAX file to handle the partial page.
1024  */
1025 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
1026 {
1027         unsigned length = PAGE_ALIGN(from) - from;
1028         return dax_zero_page_range(inode, from, length, get_block);
1029 }
1030 EXPORT_SYMBOL_GPL(dax_truncate_page);
1031
1032 #ifdef CONFIG_FS_IOMAP
1033 static loff_t
1034 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
1035                 struct iomap *iomap)
1036 {
1037         struct iov_iter *iter = data;
1038         loff_t end = pos + length, done = 0;
1039         ssize_t ret = 0;
1040
1041         if (iov_iter_rw(iter) == READ) {
1042                 end = min(end, i_size_read(inode));
1043                 if (pos >= end)
1044                         return 0;
1045
1046                 if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
1047                         return iov_iter_zero(min(length, end - pos), iter);
1048         }
1049
1050         if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
1051                 return -EIO;
1052
1053         while (pos < end) {
1054                 unsigned offset = pos & (PAGE_SIZE - 1);
1055                 struct blk_dax_ctl dax = { 0 };
1056                 ssize_t map_len;
1057
1058                 dax.sector = iomap->blkno +
1059                         (((pos & PAGE_MASK) - iomap->offset) >> 9);
1060                 dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
1061                 map_len = dax_map_atomic(iomap->bdev, &dax);
1062                 if (map_len < 0) {
1063                         ret = map_len;
1064                         break;
1065                 }
1066
1067                 dax.addr += offset;
1068                 map_len -= offset;
1069                 if (map_len > end - pos)
1070                         map_len = end - pos;
1071
1072                 if (iov_iter_rw(iter) == WRITE)
1073                         map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
1074                 else
1075                         map_len = copy_to_iter(dax.addr, map_len, iter);
1076                 dax_unmap_atomic(iomap->bdev, &dax);
1077                 if (map_len <= 0) {
1078                         ret = map_len ? map_len : -EFAULT;
1079                         break;
1080                 }
1081
1082                 pos += map_len;
1083                 length -= map_len;
1084                 done += map_len;
1085         }
1086
1087         return done ? done : ret;
1088 }
1089
1090 /**
1091  * dax_iomap_rw - Perform I/O to a DAX file
1092  * @iocb:       The control block for this I/O
1093  * @iter:       The addresses to do I/O from or to
1094  * @ops:        iomap ops passed from the file system
1095  *
1096  * This function performs read and write operations to directly mapped
1097  * persistent memory.  The callers needs to take care of read/write exclusion
1098  * and evicting any page cache pages in the region under I/O.
1099  */
1100 ssize_t
1101 dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
1102                 struct iomap_ops *ops)
1103 {
1104         struct address_space *mapping = iocb->ki_filp->f_mapping;
1105         struct inode *inode = mapping->host;
1106         loff_t pos = iocb->ki_pos, ret = 0, done = 0;
1107         unsigned flags = 0;
1108
1109         if (iov_iter_rw(iter) == WRITE)
1110                 flags |= IOMAP_WRITE;
1111
1112         /*
1113          * Yes, even DAX files can have page cache attached to them:  A zeroed
1114          * page is inserted into the pagecache when we have to serve a write
1115          * fault on a hole.  It should never be dirtied and can simply be
1116          * dropped from the pagecache once we get real data for the page.
1117          *
1118          * XXX: This is racy against mmap, and there's nothing we can do about
1119          * it. We'll eventually need to shift this down even further so that
1120          * we can check if we allocated blocks over a hole first.
1121          */
1122         if (mapping->nrpages) {
1123                 ret = invalidate_inode_pages2_range(mapping,
1124                                 pos >> PAGE_SHIFT,
1125                                 (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT);
1126                 WARN_ON_ONCE(ret);
1127         }
1128
1129         while (iov_iter_count(iter)) {
1130                 ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
1131                                 iter, dax_iomap_actor);
1132                 if (ret <= 0)
1133                         break;
1134                 pos += ret;
1135                 done += ret;
1136         }
1137
1138         iocb->ki_pos += done;
1139         return done ? done : ret;
1140 }
1141 EXPORT_SYMBOL_GPL(dax_iomap_rw);
1142
1143 /**
1144  * dax_iomap_fault - handle a page fault on a DAX file
1145  * @vma: The virtual memory area where the fault occurred
1146  * @vmf: The description of the fault
1147  * @ops: iomap ops passed from the file system
1148  *
1149  * When a page fault occurs, filesystems may call this helper in their fault
1150  * or mkwrite handler for DAX files. Assumes the caller has done all the
1151  * necessary locking for the page fault to proceed successfully.
1152  */
1153 int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
1154                         struct iomap_ops *ops)
1155 {
1156         struct address_space *mapping = vma->vm_file->f_mapping;
1157         struct inode *inode = mapping->host;
1158         unsigned long vaddr = (unsigned long)vmf->virtual_address;
1159         loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
1160         sector_t sector;
1161         struct iomap iomap = { 0 };
1162         unsigned flags = 0;
1163         int error, major = 0;
1164         void *entry;
1165
1166         /*
1167          * Check whether offset isn't beyond end of file now. Caller is supposed
1168          * to hold locks serializing us with truncate / punch hole so this is
1169          * a reliable test.
1170          */
1171         if (pos >= i_size_read(inode))
1172                 return VM_FAULT_SIGBUS;
1173
1174         entry = grab_mapping_entry(mapping, vmf->pgoff);
1175         if (IS_ERR(entry)) {
1176                 error = PTR_ERR(entry);
1177                 goto out;
1178         }
1179
1180         if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
1181                 flags |= IOMAP_WRITE;
1182
1183         /*
1184          * Note that we don't bother to use iomap_apply here: DAX required
1185          * the file system block size to be equal the page size, which means
1186          * that we never have to deal with more than a single extent here.
1187          */
1188         error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
1189         if (error)
1190                 goto unlock_entry;
1191         if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
1192                 error = -EIO;           /* fs corruption? */
1193                 goto unlock_entry;
1194         }
1195
1196         sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
1197
1198         if (vmf->cow_page) {
1199                 switch (iomap.type) {
1200                 case IOMAP_HOLE:
1201                 case IOMAP_UNWRITTEN:
1202                         clear_user_highpage(vmf->cow_page, vaddr);
1203                         break;
1204                 case IOMAP_MAPPED:
1205                         error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
1206                                         vmf->cow_page, vaddr);
1207                         break;
1208                 default:
1209                         WARN_ON_ONCE(1);
1210                         error = -EIO;
1211                         break;
1212                 }
1213
1214                 if (error)
1215                         goto unlock_entry;
1216                 if (!radix_tree_exceptional_entry(entry)) {
1217                         vmf->page = entry;
1218                         return VM_FAULT_LOCKED;
1219                 }
1220                 vmf->entry = entry;
1221                 return VM_FAULT_DAX_LOCKED;
1222         }
1223
1224         switch (iomap.type) {
1225         case IOMAP_MAPPED:
1226                 if (iomap.flags & IOMAP_F_NEW) {
1227                         count_vm_event(PGMAJFAULT);
1228                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1229                         major = VM_FAULT_MAJOR;
1230                 }
1231                 error = dax_insert_mapping(mapping, iomap.bdev, sector,
1232                                 PAGE_SIZE, &entry, vma, vmf);
1233                 break;
1234         case IOMAP_UNWRITTEN:
1235         case IOMAP_HOLE:
1236                 if (!(vmf->flags & FAULT_FLAG_WRITE))
1237                         return dax_load_hole(mapping, entry, vmf);
1238                 /*FALLTHRU*/
1239         default:
1240                 WARN_ON_ONCE(1);
1241                 error = -EIO;
1242                 break;
1243         }
1244
1245  unlock_entry:
1246         put_locked_mapping_entry(mapping, vmf->pgoff, entry);
1247  out:
1248         if (error == -ENOMEM)
1249                 return VM_FAULT_OOM | major;
1250         /* -EBUSY is fine, somebody else faulted on the same PTE */
1251         if (error < 0 && error != -EBUSY)
1252                 return VM_FAULT_SIGBUS | major;
1253         return VM_FAULT_NOPAGE | major;
1254 }
1255 EXPORT_SYMBOL_GPL(dax_iomap_fault);
1256 #endif /* CONFIG_FS_IOMAP */