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
  35 /*
  36  * We use lowest available bit in exceptional entry for locking, other two
  37  * bits to determine entry type. In total 3 special bits.
  38  */
  39 #define RADIX_DAX_SHIFT (RADIX_TREE_EXCEPTIONAL_SHIFT + 3)
  40 #define RADIX_DAX_PTE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 1))
  41 #define RADIX_DAX_PMD (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
  42 #define RADIX_DAX_TYPE_MASK (RADIX_DAX_PTE | RADIX_DAX_PMD)
  43 #define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_TYPE_MASK)
  44 #define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
  45 #define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
  46                 RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE) | \
  47                 RADIX_TREE_EXCEPTIONAL_ENTRY))
  48
  49 /* We choose 4096 entries - same as per-zone page wait tables */
  50 #define DAX_WAIT_TABLE_BITS 12
  51 #define DAX_WAIT_TABLE_ENTRIES (1 << DAX_WAIT_TABLE_BITS)
  52
  53 wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
  54
  55 static int __init init_dax_wait_table(void)
  56 {
  57         int i;
  58
  59         for (i = 0; i < DAX_WAIT_TABLE_ENTRIES; i++)
  60                 init_waitqueue_head(wait_table + i);
  61         return 0;
  62 }
  63 fs_initcall(init_dax_wait_table);
  64
  65 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
  66                                               pgoff_t index)
  67 {
  68         unsigned long hash = hash_long((unsigned long)mapping ^ index,
  69                                        DAX_WAIT_TABLE_BITS);
  70         return wait_table + hash;
  71 }
  72
  73 static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
  74 {
  75         struct request_queue *q = bdev->bd_queue;
  76         long rc = -EIO;
  77
  78         dax->addr = (void __pmem *) ERR_PTR(-EIO);
  79         if (blk_queue_enter(q, true) != 0)
  80                 return rc;
  81
  82         rc = bdev_direct_access(bdev, dax);
  83         if (rc < 0) {
  84                 dax->addr = (void __pmem *) ERR_PTR(rc);
  85                 blk_queue_exit(q);
  86                 return rc;
  87         }
  88         return rc;
  89 }
  90
  91 static void dax_unmap_atomic(struct block_device *bdev,
  92                 const struct blk_dax_ctl *dax)
  93 {
  94         if (IS_ERR(dax->addr))
  95                 return;
  96         blk_queue_exit(bdev->bd_queue);
  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 static bool buffer_written(struct buffer_head *bh)
 120 {
 121         return buffer_mapped(bh) && !buffer_unwritten(bh);
 122 }
 123
 124 /*
 125  * When ext4 encounters a hole, it returns without modifying the buffer_head
 126  * which means that we can't trust b_size.  To cope with this, we set b_state
 127  * to 0 before calling get_block and, if any bit is set, we know we can trust
 128  * b_size.  Unfortunate, really, since ext4 knows precisely how long a hole is
 129  * and would save us time calling get_block repeatedly.
 130  */
 131 static bool buffer_size_valid(struct buffer_head *bh)
 132 {
 133         return bh->b_state != 0;
 134 }
 135
 136
 137 static sector_t to_sector(const struct buffer_head *bh,
 138                 const struct inode *inode)
 139 {
 140         sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
 141
 142         return sector;
 143 }
 144
 145 static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 146                       loff_t start, loff_t end, get_block_t get_block,
 147                       struct buffer_head *bh)
 148 {
 149         loff_t pos = start, max = start, bh_max = start;
 150         bool hole = false, need_wmb = false;
 151         struct block_device *bdev = NULL;
 152         int rw = iov_iter_rw(iter), rc;
 153         long map_len = 0;
 154         struct blk_dax_ctl dax = {
 155                 .addr = (void __pmem *) ERR_PTR(-EIO),
 156         };
 157         unsigned blkbits = inode->i_blkbits;
 158         sector_t file_blks = (i_size_read(inode) + (1 << blkbits) - 1)
 159                                                                 >> blkbits;
 160
 161         if (rw == READ)
 162                 end = min(end, i_size_read(inode));
 163
 164         while (pos < end) {
 165                 size_t len;
 166                 if (pos == max) {
 167                         long page = pos >> PAGE_SHIFT;
 168                         sector_t block = page << (PAGE_SHIFT - blkbits);
 169                         unsigned first = pos - (block << blkbits);
 170                         long size;
 171
 172                         if (pos == bh_max) {
 173                                 bh->b_size = PAGE_ALIGN(end - pos);
 174                                 bh->b_state = 0;
 175                                 rc = get_block(inode, block, bh, rw == WRITE);
 176                                 if (rc)
 177                                         break;
 178                                 if (!buffer_size_valid(bh))
 179                                         bh->b_size = 1 << blkbits;
 180                                 bh_max = pos - first + bh->b_size;
 181                                 bdev = bh->b_bdev;
 182                                 /*
 183                                  * We allow uninitialized buffers for writes
 184                                  * beyond EOF as those cannot race with faults
 185                                  */
 186                                 WARN_ON_ONCE(
 187                                         (buffer_new(bh) && block < file_blks) ||
 188                                         (rw == WRITE && buffer_unwritten(bh)));
 189                         } else {
 190                                 unsigned done = bh->b_size -
 191                                                 (bh_max - (pos - first));
 192                                 bh->b_blocknr += done >> blkbits;
 193                                 bh->b_size -= done;
 194                         }
 195
 196                         hole = rw == READ && !buffer_written(bh);
 197                         if (hole) {
 198                                 size = bh->b_size - first;
 199                         } else {
 200                                 dax_unmap_atomic(bdev, &dax);
 201                                 dax.sector = to_sector(bh, inode);
 202                                 dax.size = bh->b_size;
 203                                 map_len = dax_map_atomic(bdev, &dax);
 204                                 if (map_len < 0) {
 205                                         rc = map_len;
 206                                         break;
 207                                 }
 208                                 dax.addr += first;
 209                                 size = map_len - first;
 210                         }
 211                         /*
 212                          * pos + size is one past the last offset for IO,
 213                          * so pos + size can overflow loff_t at extreme offsets.
 214                          * Cast to u64 to catch this and get the true minimum.
 215                          */
 216                         max = min_t(u64, pos + size, end);
 217                 }
 218
 219                 if (iov_iter_rw(iter) == WRITE) {
 220                         len = copy_from_iter_pmem(dax.addr, max - pos, iter);
 221                         need_wmb = true;
 222                 } else if (!hole)
 223                         len = copy_to_iter((void __force *) dax.addr, max - pos,
 224                                         iter);
 225                 else
 226                         len = iov_iter_zero(max - pos, iter);
 227
 228                 if (!len) {
 229                         rc = -EFAULT;
 230                         break;
 231                 }
 232
 233                 pos += len;
 234                 if (!IS_ERR(dax.addr))
 235                         dax.addr += len;
 236         }
 237
 238         if (need_wmb)
 239                 wmb_pmem();
 240         dax_unmap_atomic(bdev, &dax);
 241
 242         return (pos == start) ? rc : pos - start;
 243 }
 244
 245 /**
 246  * dax_do_io - Perform I/O to a DAX file
 247  * @iocb: The control block for this I/O
 248  * @inode: The file which the I/O is directed at
 249  * @iter: The addresses to do I/O from or to
 250  * @get_block: The filesystem method used to translate file offsets to blocks
 251  * @end_io: A filesystem callback for I/O completion
 252  * @flags: See below
 253  *
 254  * This function uses the same locking scheme as do_blockdev_direct_IO:
 255  * If @flags has DIO_LOCKING set, we assume that the i_mutex is held by the
 256  * caller for writes.  For reads, we take and release the i_mutex ourselves.
 257  * If DIO_LOCKING is not set, the filesystem takes care of its own locking.
 258  * As with do_blockdev_direct_IO(), we increment i_dio_count while the I/O
 259  * is in progress.
 260  */
 261 ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
 262                   struct iov_iter *iter, get_block_t get_block,
 263                   dio_iodone_t end_io, int flags)
 264 {
 265         struct buffer_head bh;
 266         ssize_t retval = -EINVAL;
 267         loff_t pos = iocb->ki_pos;
 268         loff_t end = pos + iov_iter_count(iter);
 269
 270         memset(&bh, 0, sizeof(bh));
 271         bh.b_bdev = inode->i_sb->s_bdev;
 272
 273         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
 274                 inode_lock(inode);
 275
 276         /* Protects against truncate */
 277         if (!(flags & DIO_SKIP_DIO_COUNT))
 278                 inode_dio_begin(inode);
 279
 280         retval = dax_io(inode, iter, pos, end, get_block, &bh);
 281
 282         if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
 283                 inode_unlock(inode);
 284
 285         if (end_io) {
 286                 int err;
 287
 288                 err = end_io(iocb, pos, retval, bh.b_private);
 289                 if (err)
 290                         retval = err;
 291         }
 292
 293         if (!(flags & DIO_SKIP_DIO_COUNT))
 294                 inode_dio_end(inode);
 295         return retval;
 296 }
 297 EXPORT_SYMBOL_GPL(dax_do_io);
 298
 299 /*
 300  * DAX radix tree locking
 301  */
 302 struct exceptional_entry_key {
 303         struct address_space *mapping;
 304         unsigned long index;
 305 };
 306
 307 struct wait_exceptional_entry_queue {
 308         wait_queue_t wait;
 309         struct exceptional_entry_key key;
 310 };
 311
 312 static int wake_exceptional_entry_func(wait_queue_t *wait, unsigned int mode,
 313                                        int sync, void *keyp)
 314 {
 315         struct exceptional_entry_key *key = keyp;
 316         struct wait_exceptional_entry_queue *ewait =
 317                 container_of(wait, struct wait_exceptional_entry_queue, wait);
 318
 319         if (key->mapping != ewait->key.mapping ||
 320             key->index != ewait->key.index)
 321                 return 0;
 322         return autoremove_wake_function(wait, mode, sync, NULL);
 323 }
 324
 325 /*
 326  * Check whether the given slot is locked. The function must be called with
 327  * mapping->tree_lock held
 328  */
 329 static inline int slot_locked(struct address_space *mapping, void **slot)
 330 {
 331         unsigned long entry = (unsigned long)
 332                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 333         return entry & RADIX_DAX_ENTRY_LOCK;
 334 }
 335
 336 /*
 337  * Mark the given slot is locked. The function must be called with
 338  * mapping->tree_lock held
 339  */
 340 static inline void *lock_slot(struct address_space *mapping, void **slot)
 341 {
 342         unsigned long entry = (unsigned long)
 343                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 344
 345         entry |= RADIX_DAX_ENTRY_LOCK;
 346         radix_tree_replace_slot(slot, (void *)entry);
 347         return (void *)entry;
 348 }
 349
 350 /*
 351  * Mark the given slot is unlocked. The function must be called with
 352  * mapping->tree_lock held
 353  */
 354 static inline void *unlock_slot(struct address_space *mapping, void **slot)
 355 {
 356         unsigned long entry = (unsigned long)
 357                 radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 358
 359         entry &= ~(unsigned long)RADIX_DAX_ENTRY_LOCK;
 360         radix_tree_replace_slot(slot, (void *)entry);
 361         return (void *)entry;
 362 }
 363
 364 /*
 365  * Lookup entry in radix tree, wait for it to become unlocked if it is
 366  * exceptional entry and return it. The caller must call
 367  * put_unlocked_mapping_entry() when he decided not to lock the entry or
 368  * put_locked_mapping_entry() when he locked the entry and now wants to
 369  * unlock it.
 370  *
 371  * The function must be called with mapping->tree_lock held.
 372  */
 373 static void *get_unlocked_mapping_entry(struct address_space *mapping,
 374                                         pgoff_t index, void ***slotp)
 375 {
 376         void *ret, **slot;
 377         struct wait_exceptional_entry_queue ewait;
 378         wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
 379
 380         init_wait(&ewait.wait);
 381         ewait.wait.func = wake_exceptional_entry_func;
 382         ewait.key.mapping = mapping;
 383         ewait.key.index = index;
 384
 385         for (;;) {
 386                 ret = __radix_tree_lookup(&mapping->page_tree, index, NULL,
 387                                           &slot);
 388                 if (!ret || !radix_tree_exceptional_entry(ret) ||
 389                     !slot_locked(mapping, slot)) {
 390                         if (slotp)
 391                                 *slotp = slot;
 392                         return ret;
 393                 }
 394                 prepare_to_wait_exclusive(wq, &ewait.wait,
 395                                           TASK_UNINTERRUPTIBLE);
 396                 spin_unlock_irq(&mapping->tree_lock);
 397                 schedule();
 398                 finish_wait(wq, &ewait.wait);
 399                 spin_lock_irq(&mapping->tree_lock);
 400         }
 401 }
 402
 403 /*
 404  * Find radix tree entry at given index. If it points to a page, return with
 405  * the page locked. If it points to the exceptional entry, return with the
 406  * radix tree entry locked. If the radix tree doesn't contain given index,
 407  * create empty exceptional entry for the index and return with it locked.
 408  *
 409  * Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
 410  * persistent memory the benefit is doubtful. We can add that later if we can
 411  * show it helps.
 412  */
 413 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
 414 {
 415         void *ret, **slot;
 416
 417 restart:
 418         spin_lock_irq(&mapping->tree_lock);
 419         ret = get_unlocked_mapping_entry(mapping, index, &slot);
 420         /* No entry for given index? Make sure radix tree is big enough. */
 421         if (!ret) {
 422                 int err;
 423
 424                 spin_unlock_irq(&mapping->tree_lock);
 425                 err = radix_tree_preload(
 426                                 mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
 427                 if (err)
 428                         return ERR_PTR(err);
 429                 ret = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
 430                                RADIX_DAX_ENTRY_LOCK);
 431                 spin_lock_irq(&mapping->tree_lock);
 432                 err = radix_tree_insert(&mapping->page_tree, index, ret);
 433                 radix_tree_preload_end();
 434                 if (err) {
 435                         spin_unlock_irq(&mapping->tree_lock);
 436                         /* Someone already created the entry? */
 437                         if (err == -EEXIST)
 438                                 goto restart;
 439                         return ERR_PTR(err);
 440                 }
 441                 /* Good, we have inserted empty locked entry into the tree. */
 442                 mapping->nrexceptional++;
 443                 spin_unlock_irq(&mapping->tree_lock);
 444                 return ret;
 445         }
 446         /* Normal page in radix tree? */
 447         if (!radix_tree_exceptional_entry(ret)) {
 448                 struct page *page = ret;
 449
 450                 get_page(page);
 451                 spin_unlock_irq(&mapping->tree_lock);
 452                 lock_page(page);
 453                 /* Page got truncated? Retry... */
 454                 if (unlikely(page->mapping != mapping)) {
 455                         unlock_page(page);
 456                         put_page(page);
 457                         goto restart;
 458                 }
 459                 return page;
 460         }
 461         ret = lock_slot(mapping, slot);
 462         spin_unlock_irq(&mapping->tree_lock);
 463         return ret;
 464 }
 465
 466 void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 467                                    pgoff_t index, bool wake_all)
 468 {
 469         wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index);
 470
 471         /*
 472          * Checking for locked entry and prepare_to_wait_exclusive() happens
 473          * under mapping->tree_lock, ditto for entry handling in our callers.
 474          * So at this point all tasks that could have seen our entry locked
 475          * must be in the waitqueue and the following check will see them.
 476          */
 477         if (waitqueue_active(wq)) {
 478                 struct exceptional_entry_key key;
 479
 480                 key.mapping = mapping;
 481                 key.index = index;
 482                 __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
 483         }
 484 }
 485
 486 void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
 487 {
 488         void *ret, **slot;
 489
 490         spin_lock_irq(&mapping->tree_lock);
 491         ret = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
 492         if (WARN_ON_ONCE(!ret || !radix_tree_exceptional_entry(ret) ||
 493                          !slot_locked(mapping, slot))) {
 494                 spin_unlock_irq(&mapping->tree_lock);
 495                 return;
 496         }
 497         unlock_slot(mapping, slot);
 498         spin_unlock_irq(&mapping->tree_lock);
 499         dax_wake_mapping_entry_waiter(mapping, index, false);
 500 }
 501
 502 static void put_locked_mapping_entry(struct address_space *mapping,
 503                                      pgoff_t index, void *entry)
 504 {
 505         if (!radix_tree_exceptional_entry(entry)) {
 506                 unlock_page(entry);
 507                 put_page(entry);
 508         } else {
 509                 dax_unlock_mapping_entry(mapping, index);
 510         }
 511 }
 512
 513 /*
 514  * Called when we are done with radix tree entry we looked up via
 515  * get_unlocked_mapping_entry() and which we didn't lock in the end.
 516  */
 517 static void put_unlocked_mapping_entry(struct address_space *mapping,
 518                                        pgoff_t index, void *entry)
 519 {
 520         if (!radix_tree_exceptional_entry(entry))
 521                 return;
 522
 523         /* We have to wake up next waiter for the radix tree entry lock */
 524         dax_wake_mapping_entry_waiter(mapping, index, false);
 525 }
 526
 527 /*
 528  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
 529  * entry to get unlocked before deleting it.
 530  */
 531 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index)
 532 {
 533         void *entry;
 534
 535         spin_lock_irq(&mapping->tree_lock);
 536         entry = get_unlocked_mapping_entry(mapping, index, NULL);
 537         /*
 538          * This gets called from truncate / punch_hole path. As such, the caller
 539          * must hold locks protecting against concurrent modifications of the
 540          * radix tree (usually fs-private i_mmap_sem for writing). Since the
 541          * caller has seen exceptional entry for this index, we better find it
 542          * at that index as well...
 543          */
 544         if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry))) {
 545                 spin_unlock_irq(&mapping->tree_lock);
 546                 return 0;
 547         }
 548         radix_tree_delete(&mapping->page_tree, index);
 549         mapping->nrexceptional--;
 550         spin_unlock_irq(&mapping->tree_lock);
 551         dax_wake_mapping_entry_waiter(mapping, index, true);
 552
 553         return 1;
 554 }
 555
 556 /*
 557  * The user has performed a load from a hole in the file.  Allocating
 558  * a new page in the file would cause excessive storage usage for
 559  * workloads with sparse files.  We allocate a page cache page instead.
 560  * We'll kick it out of the page cache if it's ever written to,
 561  * otherwise it will simply fall out of the page cache under memory
 562  * pressure without ever having been dirtied.
 563  */
 564 static int dax_load_hole(struct address_space *mapping, void *entry,
 565                          struct vm_fault *vmf)
 566 {
 567         struct page *page;
 568
 569         /* Hole page already exists? Return it...  */
 570         if (!radix_tree_exceptional_entry(entry)) {
 571                 vmf->page = entry;
 572                 return VM_FAULT_LOCKED;
 573         }
 574
 575         /* This will replace locked radix tree entry with a hole page */
 576         page = find_or_create_page(mapping, vmf->pgoff,
 577                                    vmf->gfp_mask | __GFP_ZERO);
 578         if (!page) {
 579                 put_locked_mapping_entry(mapping, vmf->pgoff, entry);
 580                 return VM_FAULT_OOM;
 581         }
 582         vmf->page = page;
 583         return VM_FAULT_LOCKED;
 584 }
 585
 586 static int copy_user_bh(struct page *to, struct inode *inode,
 587                 struct buffer_head *bh, unsigned long vaddr)
 588 {
 589         struct blk_dax_ctl dax = {
 590                 .sector = to_sector(bh, inode),
 591                 .size = bh->b_size,
 592         };
 593         struct block_device *bdev = bh->b_bdev;
 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         wmb_pmem();
 792         return 0;
 793 }
 794 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 795
 796 static int dax_insert_mapping(struct address_space *mapping,
 797                         struct buffer_head *bh, void **entryp,
 798                         struct vm_area_struct *vma, struct vm_fault *vmf)
 799 {
 800         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 801         struct block_device *bdev = bh->b_bdev;
 802         struct blk_dax_ctl dax = {
 803                 .sector = to_sector(bh, mapping->host),
 804                 .size = bh->b_size,
 805         };
 806         void *ret;
 807         void *entry = *entryp;
 808
 809         if (dax_map_atomic(bdev, &dax) < 0)
 810                 return PTR_ERR(dax.addr);
 811         dax_unmap_atomic(bdev, &dax);
 812
 813         ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
 814         if (IS_ERR(ret))
 815                 return PTR_ERR(ret);
 816         *entryp = ret;
 817
 818         return vm_insert_mixed(vma, vaddr, dax.pfn);
 819 }
 820
 821 /**
 822  * __dax_fault - handle a page fault on a DAX file
 823  * @vma: The virtual memory area where the fault occurred
 824  * @vmf: The description of the fault
 825  * @get_block: The filesystem method used to translate file offsets to blocks
 826  *
 827  * When a page fault occurs, filesystems may call this helper in their
 828  * fault handler for DAX files. __dax_fault() assumes the caller has done all
 829  * the necessary locking for the page fault to proceed successfully.
 830  */
 831 int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 832                         get_block_t get_block)
 833 {
 834         struct file *file = vma->vm_file;
 835         struct address_space *mapping = file->f_mapping;
 836         struct inode *inode = mapping->host;
 837         void *entry;
 838         struct buffer_head bh;
 839         unsigned long vaddr = (unsigned long)vmf->virtual_address;
 840         unsigned blkbits = inode->i_blkbits;
 841         sector_t block;
 842         pgoff_t size;
 843         int error;
 844         int major = 0;
 845
 846         /*
 847          * Check whether offset isn't beyond end of file now. Caller is supposed
 848          * to hold locks serializing us with truncate / punch hole so this is
 849          * a reliable test.
 850          */
 851         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 852         if (vmf->pgoff >= size)
 853                 return VM_FAULT_SIGBUS;
 854
 855         memset(&bh, 0, sizeof(bh));
 856         block = (sector_t)vmf->pgoff << (PAGE_SHIFT - blkbits);
 857         bh.b_bdev = inode->i_sb->s_bdev;
 858         bh.b_size = PAGE_SIZE;
 859
 860         entry = grab_mapping_entry(mapping, vmf->pgoff);
 861         if (IS_ERR(entry)) {
 862                 error = PTR_ERR(entry);
 863                 goto out;
 864         }
 865
 866         error = get_block(inode, block, &bh, 0);
 867         if (!error && (bh.b_size < PAGE_SIZE))
 868                 error = -EIO;           /* fs corruption? */
 869         if (error)
 870                 goto unlock_entry;
 871
 872         if (vmf->cow_page) {
 873                 struct page *new_page = vmf->cow_page;
 874                 if (buffer_written(&bh))
 875                         error = copy_user_bh(new_page, inode, &bh, vaddr);
 876                 else
 877                         clear_user_highpage(new_page, vaddr);
 878                 if (error)
 879                         goto unlock_entry;
 880                 if (!radix_tree_exceptional_entry(entry)) {
 881                         vmf->page = entry;
 882                         return VM_FAULT_LOCKED;
 883                 }
 884                 vmf->entry = entry;
 885                 return VM_FAULT_DAX_LOCKED;
 886         }
 887
 888         if (!buffer_mapped(&bh)) {
 889                 if (vmf->flags & FAULT_FLAG_WRITE) {
 890                         error = get_block(inode, block, &bh, 1);
 891                         count_vm_event(PGMAJFAULT);
 892                         mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
 893                         major = VM_FAULT_MAJOR;
 894                         if (!error && (bh.b_size < PAGE_SIZE))
 895                                 error = -EIO;
 896                         if (error)
 897                                 goto unlock_entry;
 898                 } else {
 899                         return dax_load_hole(mapping, entry, vmf);
 900                 }
 901         }
 902
 903         /* Filesystem should not return unwritten buffers to us! */
 904         WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
 905         error = dax_insert_mapping(mapping, &bh, &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(__dax_fault);
 917
 918 /**
 919  * dax_fault - handle a page fault on a DAX file
 920  * @vma: The virtual memory area where the fault occurred
 921  * @vmf: The description of the fault
 922  * @get_block: The filesystem method used to translate file offsets to blocks
 923  *
 924  * When a page fault occurs, filesystems may call this helper in their
 925  * fault handler for DAX files.
 926  */
 927 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 928               get_block_t get_block)
 929 {
 930         int result;
 931         struct super_block *sb = file_inode(vma->vm_file)->i_sb;
 932
 933         if (vmf->flags & FAULT_FLAG_WRITE) {
 934                 sb_start_pagefault(sb);
 935                 file_update_time(vma->vm_file);
 936         }
 937         result = __dax_fault(vma, vmf, get_block);
 938         if (vmf->flags & FAULT_FLAG_WRITE)
 939                 sb_end_pagefault(sb);
 940
 941         return result;
 942 }
 943 EXPORT_SYMBOL_GPL(dax_fault);
 944
 945 #if defined(CONFIG_TRANSPARENT_HUGEPAGE)
 946 /*
 947  * The 'colour' (ie low bits) within a PMD of a page offset.  This comes up
 948  * more often than one might expect in the below function.
 949  */
 950 #define PG_PMD_COLOUR   ((PMD_SIZE >> PAGE_SHIFT) - 1)
 951
 952 static void __dax_dbg(struct buffer_head *bh, unsigned long address,
 953                 const char *reason, const char *fn)
 954 {
 955         if (bh) {
 956                 char bname[BDEVNAME_SIZE];
 957                 bdevname(bh->b_bdev, bname);
 958                 pr_debug("%s: %s addr: %lx dev %s state %lx start %lld "
 959                         "length %zd fallback: %s\n", fn, current->comm,
 960                         address, bname, bh->b_state, (u64)bh->b_blocknr,
 961                         bh->b_size, reason);
 962         } else {
 963                 pr_debug("%s: %s addr: %lx fallback: %s\n", fn,
 964                         current->comm, address, reason);
 965         }
 966 }
 967
 968 #define dax_pmd_dbg(bh, address, reason)        __dax_dbg(bh, address, reason, "dax_pmd")
 969
 970 int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 971                 pmd_t *pmd, unsigned int flags, get_block_t get_block)
 972 {
 973         struct file *file = vma->vm_file;
 974         struct address_space *mapping = file->f_mapping;
 975         struct inode *inode = mapping->host;
 976         struct buffer_head bh;
 977         unsigned blkbits = inode->i_blkbits;
 978         unsigned long pmd_addr = address & PMD_MASK;
 979         bool write = flags & FAULT_FLAG_WRITE;
 980         struct block_device *bdev;
 981         pgoff_t size, pgoff;
 982         sector_t block;
 983         int result = 0;
 984         bool alloc = false;
 985
 986         /* dax pmd mappings require pfn_t_devmap() */
 987         if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
 988                 return VM_FAULT_FALLBACK;
 989
 990         /* Fall back to PTEs if we're going to COW */
 991         if (write && !(vma->vm_flags & VM_SHARED)) {
 992                 split_huge_pmd(vma, pmd, address);
 993                 dax_pmd_dbg(NULL, address, "cow write");
 994                 return VM_FAULT_FALLBACK;
 995         }
 996         /* If the PMD would extend outside the VMA */
 997         if (pmd_addr < vma->vm_start) {
 998                 dax_pmd_dbg(NULL, address, "vma start unaligned");
 999                 return VM_FAULT_FALLBACK;
1000         }
1001         if ((pmd_addr + PMD_SIZE) > vma->vm_end) {
1002                 dax_pmd_dbg(NULL, address, "vma end unaligned");
1003                 return VM_FAULT_FALLBACK;
1004         }
1005
1006         pgoff = linear_page_index(vma, pmd_addr);
1007         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
1008         if (pgoff >= size)
1009                 return VM_FAULT_SIGBUS;
1010         /* If the PMD would cover blocks out of the file */
1011         if ((pgoff | PG_PMD_COLOUR) >= size) {
1012                 dax_pmd_dbg(NULL, address,
1013                                 "offset + huge page size > file size");
1014                 return VM_FAULT_FALLBACK;
1015         }
1016
1017         memset(&bh, 0, sizeof(bh));
1018         bh.b_bdev = inode->i_sb->s_bdev;
1019         block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
1020
1021         bh.b_size = PMD_SIZE;
1022
1023         if (get_block(inode, block, &bh, 0) != 0)
1024                 return VM_FAULT_SIGBUS;
1025
1026         if (!buffer_mapped(&bh) && write) {
1027                 if (get_block(inode, block, &bh, 1) != 0)
1028                         return VM_FAULT_SIGBUS;
1029                 alloc = true;
1030                 WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
1031         }
1032
1033         bdev = bh.b_bdev;
1034
1035         /*
1036          * If the filesystem isn't willing to tell us the length of a hole,
1037          * just fall back to PTEs.  Calling get_block 512 times in a loop
1038          * would be silly.
1039          */
1040         if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) {
1041                 dax_pmd_dbg(&bh, address, "allocated block too small");
1042                 return VM_FAULT_FALLBACK;
1043         }
1044
1045         /*
1046          * If we allocated new storage, make sure no process has any
1047          * zero pages covering this hole
1048          */
1049         if (alloc) {
1050                 loff_t lstart = pgoff << PAGE_SHIFT;
1051                 loff_t lend = lstart + PMD_SIZE - 1; /* inclusive */
1052
1053                 truncate_pagecache_range(inode, lstart, lend);
1054         }
1055
1056         if (!write && !buffer_mapped(&bh)) {
1057                 spinlock_t *ptl;
1058                 pmd_t entry;
1059                 struct page *zero_page = get_huge_zero_page();
1060
1061                 if (unlikely(!zero_page)) {
1062                         dax_pmd_dbg(&bh, address, "no zero page");
1063                         goto fallback;
1064                 }
1065
1066                 ptl = pmd_lock(vma->vm_mm, pmd);
1067                 if (!pmd_none(*pmd)) {
1068                         spin_unlock(ptl);
1069                         dax_pmd_dbg(&bh, address, "pmd already present");
1070                         goto fallback;
1071                 }
1072
1073                 dev_dbg(part_to_dev(bdev->bd_part),
1074                                 "%s: %s addr: %lx pfn: <zero> sect: %llx\n",
1075                                 __func__, current->comm, address,
1076                                 (unsigned long long) to_sector(&bh, inode));
1077
1078                 entry = mk_pmd(zero_page, vma->vm_page_prot);
1079                 entry = pmd_mkhuge(entry);
1080                 set_pmd_at(vma->vm_mm, pmd_addr, pmd, entry);
1081                 result = VM_FAULT_NOPAGE;
1082                 spin_unlock(ptl);
1083         } else {
1084                 struct blk_dax_ctl dax = {
1085                         .sector = to_sector(&bh, inode),
1086                         .size = PMD_SIZE,
1087                 };
1088                 long length = dax_map_atomic(bdev, &dax);
1089
1090                 if (length < 0) {
1091                         dax_pmd_dbg(&bh, address, "dax-error fallback");
1092                         goto fallback;
1093                 }
1094                 if (length < PMD_SIZE) {
1095                         dax_pmd_dbg(&bh, address, "dax-length too small");
1096                         dax_unmap_atomic(bdev, &dax);
1097                         goto fallback;
1098                 }
1099                 if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR) {
1100                         dax_pmd_dbg(&bh, address, "pfn unaligned");
1101                         dax_unmap_atomic(bdev, &dax);
1102                         goto fallback;
1103                 }
1104
1105                 if (!pfn_t_devmap(dax.pfn)) {
1106                         dax_unmap_atomic(bdev, &dax);
1107                         dax_pmd_dbg(&bh, address, "pfn not in memmap");
1108                         goto fallback;
1109                 }
1110                 dax_unmap_atomic(bdev, &dax);
1111
1112                 /*
1113                  * For PTE faults we insert a radix tree entry for reads, and
1114                  * leave it clean.  Then on the first write we dirty the radix
1115                  * tree entry via the dax_pfn_mkwrite() path.  This sequence
1116                  * allows the dax_pfn_mkwrite() call to be simpler and avoid a
1117                  * call into get_block() to translate the pgoff to a sector in
1118                  * order to be able to create a new radix tree entry.
1119                  *
1120                  * The PMD path doesn't have an equivalent to
1121                  * dax_pfn_mkwrite(), though, so for a read followed by a
1122                  * write we traverse all the way through __dax_pmd_fault()
1123                  * twice.  This means we can just skip inserting a radix tree
1124                  * entry completely on the initial read and just wait until
1125                  * the write to insert a dirty entry.
1126                  */
1127                 if (write) {
1128                         /*
1129                          * We should insert radix-tree entry and dirty it here.
1130                          * For now this is broken...
1131                          */
1132                 }
1133
1134                 dev_dbg(part_to_dev(bdev->bd_part),
1135                                 "%s: %s addr: %lx pfn: %lx sect: %llx\n",
1136                                 __func__, current->comm, address,
1137                                 pfn_t_to_pfn(dax.pfn),
1138                                 (unsigned long long) dax.sector);
1139                 result |= vmf_insert_pfn_pmd(vma, address, pmd,
1140                                 dax.pfn, write);
1141         }
1142
1143  out:
1144         return result;
1145
1146  fallback:
1147         count_vm_event(THP_FAULT_FALLBACK);
1148         result = VM_FAULT_FALLBACK;
1149         goto out;
1150 }
1151 EXPORT_SYMBOL_GPL(__dax_pmd_fault);
1152
1153 /**
1154  * dax_pmd_fault - handle a PMD fault on a DAX file
1155  * @vma: The virtual memory area where the fault occurred
1156  * @vmf: The description of the fault
1157  * @get_block: The filesystem method used to translate file offsets to blocks
1158  *
1159  * When a page fault occurs, filesystems may call this helper in their
1160  * pmd_fault handler for DAX files.
1161  */
1162 int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
1163                         pmd_t *pmd, unsigned int flags, get_block_t get_block)
1164 {
1165         int result;
1166         struct super_block *sb = file_inode(vma->vm_file)->i_sb;
1167
1168         if (flags & FAULT_FLAG_WRITE) {
1169                 sb_start_pagefault(sb);
1170                 file_update_time(vma->vm_file);
1171         }
1172         result = __dax_pmd_fault(vma, address, pmd, flags, get_block);
1173         if (flags & FAULT_FLAG_WRITE)
1174                 sb_end_pagefault(sb);
1175
1176         return result;
1177 }
1178 EXPORT_SYMBOL_GPL(dax_pmd_fault);
1179 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
1180
1181 /**
1182  * dax_pfn_mkwrite - handle first write to DAX page
1183  * @vma: The virtual memory area where the fault occurred
1184  * @vmf: The description of the fault
1185  */
1186 int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
1187 {
1188         struct file *file = vma->vm_file;
1189         struct address_space *mapping = file->f_mapping;
1190         void *entry;
1191         pgoff_t index = vmf->pgoff;
1192
1193         spin_lock_irq(&mapping->tree_lock);
1194         entry = get_unlocked_mapping_entry(mapping, index, NULL);
1195         if (!entry || !radix_tree_exceptional_entry(entry))
1196                 goto out;
1197         radix_tree_tag_set(&mapping->page_tree, index, PAGECACHE_TAG_DIRTY);
1198         put_unlocked_mapping_entry(mapping, index, entry);
1199 out:
1200         spin_unlock_irq(&mapping->tree_lock);
1201         return VM_FAULT_NOPAGE;
1202 }
1203 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
1204
1205 static bool dax_range_is_aligned(struct block_device *bdev,
1206                                  unsigned int offset, unsigned int length)
1207 {
1208         unsigned short sector_size = bdev_logical_block_size(bdev);
1209
1210         if (!IS_ALIGNED(offset, sector_size))
1211                 return false;
1212         if (!IS_ALIGNED(length, sector_size))
1213                 return false;
1214
1215         return true;
1216 }
1217
1218 int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
1219                 unsigned int offset, unsigned int length)
1220 {
1221         struct blk_dax_ctl dax = {
1222                 .sector         = sector,
1223                 .size           = PAGE_SIZE,
1224         };
1225
1226         if (dax_range_is_aligned(bdev, offset, length)) {
1227                 sector_t start_sector = dax.sector + (offset >> 9);
1228
1229                 return blkdev_issue_zeroout(bdev, start_sector,
1230                                 length >> 9, GFP_NOFS, true);
1231         } else {
1232                 if (dax_map_atomic(bdev, &dax) < 0)
1233                         return PTR_ERR(dax.addr);
1234                 clear_pmem(dax.addr + offset, length);
1235                 wmb_pmem();
1236                 dax_unmap_atomic(bdev, &dax);
1237         }
1238         return 0;
1239 }
1240 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
1241
1242 /**
1243  * dax_zero_page_range - zero a range within a page of a DAX file
1244  * @inode: The file being truncated
1245  * @from: The file offset that is being truncated to
1246  * @length: The number of bytes to zero
1247  * @get_block: The filesystem method used to translate file offsets to blocks
1248  *
1249  * This function can be called by a filesystem when it is zeroing part of a
1250  * page in a DAX file.  This is intended for hole-punch operations.  If
1251  * you are truncating a file, the helper function dax_truncate_page() may be
1252  * more convenient.
1253  */
1254 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
1255                                                         get_block_t get_block)
1256 {
1257         struct buffer_head bh;
1258         pgoff_t index = from >> PAGE_SHIFT;
1259         unsigned offset = from & (PAGE_SIZE-1);
1260         int err;
1261
1262         /* Block boundary? Nothing to do */
1263         if (!length)
1264                 return 0;
1265         BUG_ON((offset + length) > PAGE_SIZE);
1266
1267         memset(&bh, 0, sizeof(bh));
1268         bh.b_bdev = inode->i_sb->s_bdev;
1269         bh.b_size = PAGE_SIZE;
1270         err = get_block(inode, index, &bh, 0);
1271         if (err < 0 || !buffer_written(&bh))
1272                 return err;
1273
1274         return __dax_zero_page_range(bh.b_bdev, to_sector(&bh, inode),
1275                         offset, length);
1276 }
1277 EXPORT_SYMBOL_GPL(dax_zero_page_range);
1278
1279 /**
1280  * dax_truncate_page - handle a partial page being truncated in a DAX file
1281  * @inode: The file being truncated
1282  * @from: The file offset that is being truncated to
1283  * @get_block: The filesystem method used to translate file offsets to blocks
1284  *
1285  * Similar to block_truncate_page(), this function can be called by a
1286  * filesystem when it is truncating a DAX file to handle the partial page.
1287  */
1288 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
1289 {
1290         unsigned length = PAGE_ALIGN(from) - from;
1291         return dax_zero_page_range(inode, from, length, get_block);
1292 }
1293 EXPORT_SYMBOL_GPL(dax_truncate_page);