fs/btrfs/ordered-data.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/gfp.h>
  20 #include <linux/slab.h>
  21 #include <linux/blkdev.h>
  22 #include <linux/writeback.h>
  23 #include <linux/pagevec.h>
  24 #include "ctree.h"
  25 #include "transaction.h"
  26 #include "btrfs_inode.h"
  27 #include "extent_io.h"
  28
  29 static u64 entry_end(struct btrfs_ordered_extent *entry)
  30 {
  31         if (entry->file_offset + entry->len < entry->file_offset)
  32                 return (u64)-1;
  33         return entry->file_offset + entry->len;
  34 }
  35
  36 /* returns NULL if the insertion worked, or it returns the node it did find
  37  * in the tree
  38  */
  39 static struct rb_node *tree_insert(struct rb_root *root, u64 file_offset,
  40                                    struct rb_node *node)
  41 {
  42         struct rb_node **p = &root->rb_node;
  43         struct rb_node *parent = NULL;
  44         struct btrfs_ordered_extent *entry;
  45
  46         while (*p) {
  47                 parent = *p;
  48                 entry = rb_entry(parent, struct btrfs_ordered_extent, rb_node);
  49
  50                 if (file_offset < entry->file_offset)
  51                         p = &(*p)->rb_left;
  52                 else if (file_offset >= entry_end(entry))
  53                         p = &(*p)->rb_right;
  54                 else
  55                         return parent;
  56         }
  57
  58         rb_link_node(node, parent, p);
  59         rb_insert_color(node, root);
  60         return NULL;
  61 }
  62
  63 /*
  64  * look for a given offset in the tree, and if it can't be found return the
  65  * first lesser offset
  66  */
  67 static struct rb_node *__tree_search(struct rb_root *root, u64 file_offset,
  68                                      struct rb_node **prev_ret)
  69 {
  70         struct rb_node *n = root->rb_node;
  71         struct rb_node *prev = NULL;
  72         struct rb_node *test;
  73         struct btrfs_ordered_extent *entry;
  74         struct btrfs_ordered_extent *prev_entry = NULL;
  75
  76         while (n) {
  77                 entry = rb_entry(n, struct btrfs_ordered_extent, rb_node);
  78                 prev = n;
  79                 prev_entry = entry;
  80
  81                 if (file_offset < entry->file_offset)
  82                         n = n->rb_left;
  83                 else if (file_offset >= entry_end(entry))
  84                         n = n->rb_right;
  85                 else
  86                         return n;
  87         }
  88         if (!prev_ret)
  89                 return NULL;
  90
  91         while (prev && file_offset >= entry_end(prev_entry)) {
  92                 test = rb_next(prev);
  93                 if (!test)
  94                         break;
  95                 prev_entry = rb_entry(test, struct btrfs_ordered_extent,
  96                                       rb_node);
  97                 if (file_offset < entry_end(prev_entry))
  98                         break;
  99
 100                 prev = test;
 101         }
 102         if (prev)
 103                 prev_entry = rb_entry(prev, struct btrfs_ordered_extent,
 104                                       rb_node);
 105         while (prev && file_offset < entry_end(prev_entry)) {
 106                 test = rb_prev(prev);
 107                 if (!test)
 108                         break;
 109                 prev_entry = rb_entry(test, struct btrfs_ordered_extent,
 110                                       rb_node);
 111                 prev = test;
 112         }
 113         *prev_ret = prev;
 114         return NULL;
 115 }
 116
 117 /*
 118  * helper to check if a given offset is inside a given entry
 119  */
 120 static int offset_in_entry(struct btrfs_ordered_extent *entry, u64 file_offset)
 121 {
 122         if (file_offset < entry->file_offset ||
 123             entry->file_offset + entry->len <= file_offset)
 124                 return 0;
 125         return 1;
 126 }
 127
 128 /*
 129  * look find the first ordered struct that has this offset, otherwise
 130  * the first one less than this offset
 131  */
 132 static inline struct rb_node *tree_search(struct btrfs_ordered_inode_tree *tree,
 133                                           u64 file_offset)
 134 {
 135         struct rb_root *root = &tree->tree;
 136         struct rb_node *prev;
 137         struct rb_node *ret;
 138         struct btrfs_ordered_extent *entry;
 139
 140         if (tree->last) {
 141                 entry = rb_entry(tree->last, struct btrfs_ordered_extent,
 142                                  rb_node);
 143                 if (offset_in_entry(entry, file_offset))
 144                         return tree->last;
 145         }
 146         ret = __tree_search(root, file_offset, &prev);
 147         if (!ret)
 148                 ret = prev;
 149         if (ret)
 150                 tree->last = ret;
 151         return ret;
 152 }
 153
 154 /* allocate and add a new ordered_extent into the per-inode tree.
 155  * file_offset is the logical offset in the file
 156  *
 157  * start is the disk block number of an extent already reserved in the
 158  * extent allocation tree
 159  *
 160  * len is the length of the extent
 161  *
 162  * This also sets the EXTENT_ORDERED bit on the range in the inode.
 163  *
 164  * The tree is given a single reference on the ordered extent that was
 165  * inserted.
 166  */
 167 int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 168                              u64 start, u64 len, u64 disk_len, int type)
 169 {
 170         struct btrfs_ordered_inode_tree *tree;
 171         struct rb_node *node;
 172         struct btrfs_ordered_extent *entry;
 173
 174         tree = &BTRFS_I(inode)->ordered_tree;
 175         entry = kzalloc(sizeof(*entry), GFP_NOFS);
 176         if (!entry)
 177                 return -ENOMEM;
 178
 179         mutex_lock(&tree->mutex);
 180         entry->file_offset = file_offset;
 181         entry->start = start;
 182         entry->len = len;
 183         entry->disk_len = disk_len;
 184         entry->inode = inode;
 185         if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
 186                 set_bit(type, &entry->flags);
 187
 188         /* one ref for the tree */
 189         atomic_set(&entry->refs, 1);
 190         init_waitqueue_head(&entry->wait);
 191         INIT_LIST_HEAD(&entry->list);
 192         INIT_LIST_HEAD(&entry->root_extent_list);
 193
 194         node = tree_insert(&tree->tree, file_offset,
 195                            &entry->rb_node);
 196         BUG_ON(node);
 197
 198         set_extent_ordered(&BTRFS_I(inode)->io_tree, file_offset,
 199                            entry_end(entry) - 1, GFP_NOFS);
 200
 201         spin_lock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
 202         list_add_tail(&entry->root_extent_list,
 203                       &BTRFS_I(inode)->root->fs_info->ordered_extents);
 204         spin_unlock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
 205
 206         mutex_unlock(&tree->mutex);
 207         BUG_ON(node);
 208         return 0;
 209 }
 210
 211 /*
 212  * Add a struct btrfs_ordered_sum into the list of checksums to be inserted
 213  * when an ordered extent is finished.  If the list covers more than one
 214  * ordered extent, it is split across multiples.
 215  */
 216 int btrfs_add_ordered_sum(struct inode *inode,
 217                           struct btrfs_ordered_extent *entry,
 218                           struct btrfs_ordered_sum *sum)
 219 {
 220         struct btrfs_ordered_inode_tree *tree;
 221
 222         tree = &BTRFS_I(inode)->ordered_tree;
 223         mutex_lock(&tree->mutex);
 224         list_add_tail(&sum->list, &entry->list);
 225         mutex_unlock(&tree->mutex);
 226         return 0;
 227 }
 228
 229 /*
 230  * this is used to account for finished IO across a given range
 231  * of the file.  The IO should not span ordered extents.  If
 232  * a given ordered_extent is completely done, 1 is returned, otherwise
 233  * 0.
 234  *
 235  * test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
 236  * to make sure this function only returns 1 once for a given ordered extent.
 237  */
 238 int btrfs_dec_test_ordered_pending(struct inode *inode,
 239                                    u64 file_offset, u64 io_size)
 240 {
 241         struct btrfs_ordered_inode_tree *tree;
 242         struct rb_node *node;
 243         struct btrfs_ordered_extent *entry;
 244         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 245         int ret;
 246
 247         tree = &BTRFS_I(inode)->ordered_tree;
 248         mutex_lock(&tree->mutex);
 249         clear_extent_ordered(io_tree, file_offset, file_offset + io_size - 1,
 250                              GFP_NOFS);
 251         node = tree_search(tree, file_offset);
 252         if (!node) {
 253                 ret = 1;
 254                 goto out;
 255         }
 256
 257         entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 258         if (!offset_in_entry(entry, file_offset)) {
 259                 ret = 1;
 260                 goto out;
 261         }
 262
 263         ret = test_range_bit(io_tree, entry->file_offset,
 264                              entry->file_offset + entry->len - 1,
 265                              EXTENT_ORDERED, 0);
 266         if (ret == 0)
 267                 ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
 268 out:
 269         mutex_unlock(&tree->mutex);
 270         return ret == 0;
 271 }
 272
 273 /*
 274  * used to drop a reference on an ordered extent.  This will free
 275  * the extent if the last reference is dropped
 276  */
 277 int btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
 278 {
 279         struct list_head *cur;
 280         struct btrfs_ordered_sum *sum;
 281
 282         if (atomic_dec_and_test(&entry->refs)) {
 283                 while (!list_empty(&entry->list)) {
 284                         cur = entry->list.next;
 285                         sum = list_entry(cur, struct btrfs_ordered_sum, list);
 286                         list_del(&sum->list);
 287                         kfree(sum);
 288                 }
 289                 kfree(entry);
 290         }
 291         return 0;
 292 }
 293
 294 /*
 295  * remove an ordered extent from the tree.  No references are dropped
 296  * but, anyone waiting on this extent is woken up.
 297  */
 298 int btrfs_remove_ordered_extent(struct inode *inode,
 299                                 struct btrfs_ordered_extent *entry)
 300 {
 301         struct btrfs_ordered_inode_tree *tree;
 302         struct rb_node *node;
 303
 304         tree = &BTRFS_I(inode)->ordered_tree;
 305         mutex_lock(&tree->mutex);
 306         node = &entry->rb_node;
 307         rb_erase(node, &tree->tree);
 308         tree->last = NULL;
 309         set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags);
 310
 311         spin_lock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
 312         list_del_init(&entry->root_extent_list);
 313         spin_unlock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
 314
 315         mutex_unlock(&tree->mutex);
 316         wake_up(&entry->wait);
 317         return 0;
 318 }
 319
 320 /*
 321  * wait for all the ordered extents in a root.  This is done when balancing
 322  * space between drives.
 323  */
 324 int btrfs_wait_ordered_extents(struct btrfs_root *root, int nocow_only)
 325 {
 326         struct list_head splice;
 327         struct list_head *cur;
 328         struct btrfs_ordered_extent *ordered;
 329         struct inode *inode;
 330
 331         INIT_LIST_HEAD(&splice);
 332
 333         spin_lock(&root->fs_info->ordered_extent_lock);
 334         list_splice_init(&root->fs_info->ordered_extents, &splice);
 335         while (!list_empty(&splice)) {
 336                 cur = splice.next;
 337                 ordered = list_entry(cur, struct btrfs_ordered_extent,
 338                                      root_extent_list);
 339                 if (nocow_only &&
 340                     !test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags) &&
 341                     !test_bit(BTRFS_ORDERED_PREALLOC, &ordered->flags)) {
 342                         list_move(&ordered->root_extent_list,
 343                                   &root->fs_info->ordered_extents);
 344                         cond_resched_lock(&root->fs_info->ordered_extent_lock);
 345                         continue;
 346                 }
 347
 348                 list_del_init(&ordered->root_extent_list);
 349                 atomic_inc(&ordered->refs);
 350
 351                 /*
 352                  * the inode may be getting freed (in sys_unlink path).
 353                  */
 354                 inode = igrab(ordered->inode);
 355
 356                 spin_unlock(&root->fs_info->ordered_extent_lock);
 357
 358                 if (inode) {
 359                         btrfs_start_ordered_extent(inode, ordered, 1);
 360                         btrfs_put_ordered_extent(ordered);
 361                         iput(inode);
 362                 } else {
 363                         btrfs_put_ordered_extent(ordered);
 364                 }
 365
 366                 spin_lock(&root->fs_info->ordered_extent_lock);
 367         }
 368         spin_unlock(&root->fs_info->ordered_extent_lock);
 369         return 0;
 370 }
 371
 372 /*
 373  * Used to start IO or wait for a given ordered extent to finish.
 374  *
 375  * If wait is one, this effectively waits on page writeback for all the pages
 376  * in the extent, and it waits on the io completion code to insert
 377  * metadata into the btree corresponding to the extent
 378  */
 379 void btrfs_start_ordered_extent(struct inode *inode,
 380                                        struct btrfs_ordered_extent *entry,
 381                                        int wait)
 382 {
 383         u64 start = entry->file_offset;
 384         u64 end = start + entry->len - 1;
 385
 386         /*
 387          * pages in the range can be dirty, clean or writeback.  We
 388          * start IO on any dirty ones so the wait doesn't stall waiting
 389          * for pdflush to find them
 390          */
 391         btrfs_fdatawrite_range(inode->i_mapping, start, end, WB_SYNC_ALL);
 392         if (wait) {
 393                 wait_event(entry->wait, test_bit(BTRFS_ORDERED_COMPLETE,
 394                                                  &entry->flags));
 395         }
 396 }
 397
 398 /*
 399  * Used to wait on ordered extents across a large range of bytes.
 400  */
 401 int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
 402 {
 403         u64 end;
 404         u64 orig_end;
 405         u64 wait_end;
 406         struct btrfs_ordered_extent *ordered;
 407
 408         if (start + len < start) {
 409                 orig_end = INT_LIMIT(loff_t);
 410         } else {
 411                 orig_end = start + len - 1;
 412                 if (orig_end > INT_LIMIT(loff_t))
 413                         orig_end = INT_LIMIT(loff_t);
 414         }
 415         wait_end = orig_end;
 416 again:
 417         /* start IO across the range first to instantiate any delalloc
 418          * extents
 419          */
 420         btrfs_fdatawrite_range(inode->i_mapping, start, orig_end, WB_SYNC_NONE);
 421
 422         /* The compression code will leave pages locked but return from
 423          * writepage without setting the page writeback.  Starting again
 424          * with WB_SYNC_ALL will end up waiting for the IO to actually start.
 425          */
 426         btrfs_fdatawrite_range(inode->i_mapping, start, orig_end, WB_SYNC_ALL);
 427
 428         btrfs_wait_on_page_writeback_range(inode->i_mapping,
 429                                            start >> PAGE_CACHE_SHIFT,
 430                                            orig_end >> PAGE_CACHE_SHIFT);
 431
 432         end = orig_end;
 433         while (1) {
 434                 ordered = btrfs_lookup_first_ordered_extent(inode, end);
 435                 if (!ordered)
 436                         break;
 437                 if (ordered->file_offset > orig_end) {
 438                         btrfs_put_ordered_extent(ordered);
 439                         break;
 440                 }
 441                 if (ordered->file_offset + ordered->len < start) {
 442                         btrfs_put_ordered_extent(ordered);
 443                         break;
 444                 }
 445                 btrfs_start_ordered_extent(inode, ordered, 1);
 446                 end = ordered->file_offset;
 447                 btrfs_put_ordered_extent(ordered);
 448                 if (end == 0 || end == start)
 449                         break;
 450                 end--;
 451         }
 452         if (test_range_bit(&BTRFS_I(inode)->io_tree, start, orig_end,
 453                            EXTENT_ORDERED | EXTENT_DELALLOC, 0)) {
 454                 schedule_timeout(1);
 455                 goto again;
 456         }
 457         return 0;
 458 }
 459
 460 /*
 461  * find an ordered extent corresponding to file_offset.  return NULL if
 462  * nothing is found, otherwise take a reference on the extent and return it
 463  */
 464 struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct inode *inode,
 465                                                          u64 file_offset)
 466 {
 467         struct btrfs_ordered_inode_tree *tree;
 468         struct rb_node *node;
 469         struct btrfs_ordered_extent *entry = NULL;
 470
 471         tree = &BTRFS_I(inode)->ordered_tree;
 472         mutex_lock(&tree->mutex);
 473         node = tree_search(tree, file_offset);
 474         if (!node)
 475                 goto out;
 476
 477         entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 478         if (!offset_in_entry(entry, file_offset))
 479                 entry = NULL;
 480         if (entry)
 481                 atomic_inc(&entry->refs);
 482 out:
 483         mutex_unlock(&tree->mutex);
 484         return entry;
 485 }
 486
 487 /*
 488  * lookup and return any extent before 'file_offset'.  NULL is returned
 489  * if none is found
 490  */
 491 struct btrfs_ordered_extent *
 492 btrfs_lookup_first_ordered_extent(struct inode *inode, u64 file_offset)
 493 {
 494         struct btrfs_ordered_inode_tree *tree;
 495         struct rb_node *node;
 496         struct btrfs_ordered_extent *entry = NULL;
 497
 498         tree = &BTRFS_I(inode)->ordered_tree;
 499         mutex_lock(&tree->mutex);
 500         node = tree_search(tree, file_offset);
 501         if (!node)
 502                 goto out;
 503
 504         entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 505         atomic_inc(&entry->refs);
 506 out:
 507         mutex_unlock(&tree->mutex);
 508         return entry;
 509 }
 510
 511 /*
 512  * After an extent is done, call this to conditionally update the on disk
 513  * i_size.  i_size is updated to cover any fully written part of the file.
 514  */
 515 int btrfs_ordered_update_i_size(struct inode *inode,
 516                                 struct btrfs_ordered_extent *ordered)
 517 {
 518         struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
 519         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 520         u64 disk_i_size;
 521         u64 new_i_size;
 522         u64 i_size_test;
 523         struct rb_node *node;
 524         struct btrfs_ordered_extent *test;
 525
 526         mutex_lock(&tree->mutex);
 527         disk_i_size = BTRFS_I(inode)->disk_i_size;
 528
 529         /*
 530          * if the disk i_size is already at the inode->i_size, or
 531          * this ordered extent is inside the disk i_size, we're done
 532          */
 533         if (disk_i_size >= inode->i_size ||
 534             ordered->file_offset + ordered->len <= disk_i_size) {
 535                 goto out;
 536         }
 537
 538         /*
 539          * we can't update the disk_isize if there are delalloc bytes
 540          * between disk_i_size and  this ordered extent
 541          */
 542         if (test_range_bit(io_tree, disk_i_size,
 543                            ordered->file_offset + ordered->len - 1,
 544                            EXTENT_DELALLOC, 0)) {
 545                 goto out;
 546         }
 547         /*
 548          * walk backward from this ordered extent to disk_i_size.
 549          * if we find an ordered extent then we can't update disk i_size
 550          * yet
 551          */
 552         node = &ordered->rb_node;
 553         while (1) {
 554                 node = rb_prev(node);
 555                 if (!node)
 556                         break;
 557                 test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 558                 if (test->file_offset + test->len <= disk_i_size)
 559                         break;
 560                 if (test->file_offset >= inode->i_size)
 561                         break;
 562                 if (test->file_offset >= disk_i_size)
 563                         goto out;
 564         }
 565         new_i_size = min_t(u64, entry_end(ordered), i_size_read(inode));
 566
 567         /*
 568          * at this point, we know we can safely update i_size to at least
 569          * the offset from this ordered extent.  But, we need to
 570          * walk forward and see if ios from higher up in the file have
 571          * finished.
 572          */
 573         node = rb_next(&ordered->rb_node);
 574         i_size_test = 0;
 575         if (node) {
 576                 /*
 577                  * do we have an area where IO might have finished
 578                  * between our ordered extent and the next one.
 579                  */
 580                 test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 581                 if (test->file_offset > entry_end(ordered))
 582                         i_size_test = test->file_offset;
 583         } else {
 584                 i_size_test = i_size_read(inode);
 585         }
 586
 587         /*
 588          * i_size_test is the end of a region after this ordered
 589          * extent where there are no ordered extents.  As long as there
 590          * are no delalloc bytes in this area, it is safe to update
 591          * disk_i_size to the end of the region.
 592          */
 593         if (i_size_test > entry_end(ordered) &&
 594             !test_range_bit(io_tree, entry_end(ordered), i_size_test - 1,
 595                            EXTENT_DELALLOC, 0)) {
 596                 new_i_size = min_t(u64, i_size_test, i_size_read(inode));
 597         }
 598         BTRFS_I(inode)->disk_i_size = new_i_size;
 599 out:
 600         mutex_unlock(&tree->mutex);
 601         return 0;
 602 }
 603
 604 /*
 605  * search the ordered extents for one corresponding to 'offset' and
 606  * try to find a checksum.  This is used because we allow pages to
 607  * be reclaimed before their checksum is actually put into the btree
 608  */
 609 int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u64 disk_bytenr,
 610                            u32 *sum)
 611 {
 612         struct btrfs_ordered_sum *ordered_sum;
 613         struct btrfs_sector_sum *sector_sums;
 614         struct btrfs_ordered_extent *ordered;
 615         struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
 616         struct list_head *cur;
 617         unsigned long num_sectors;
 618         unsigned long i;
 619         u32 sectorsize = BTRFS_I(inode)->root->sectorsize;
 620         int ret = 1;
 621
 622         ordered = btrfs_lookup_ordered_extent(inode, offset);
 623         if (!ordered)
 624                 return 1;
 625
 626         mutex_lock(&tree->mutex);
 627         list_for_each_prev(cur, &ordered->list) {
 628                 ordered_sum = list_entry(cur, struct btrfs_ordered_sum, list);
 629                 if (disk_bytenr >= ordered_sum->bytenr) {
 630                         num_sectors = ordered_sum->len / sectorsize;
 631                         sector_sums = ordered_sum->sums;
 632                         for (i = 0; i < num_sectors; i++) {
 633                                 if (sector_sums[i].bytenr == disk_bytenr) {
 634                                         *sum = sector_sums[i].sum;
 635                                         ret = 0;
 636                                         goto out;
 637                                 }
 638                         }
 639                 }
 640         }
 641 out:
 642         mutex_unlock(&tree->mutex);
 643         btrfs_put_ordered_extent(ordered);
 644         return ret;
 645 }
 646
 647
 648 /**
 649  * taken from mm/filemap.c because it isn't exported
 650  *
 651  * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
 652  * @mapping:    address space structure to write
 653  * @start:      offset in bytes where the range starts
 654  * @end:        offset in bytes where the range ends (inclusive)
 655  * @sync_mode:  enable synchronous operation
 656  *
 657  * Start writeback against all of a mapping's dirty pages that lie
 658  * within the byte offsets <start, end> inclusive.
 659  *
 660  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 661  * opposed to a regular memory cleansing writeback.  The difference between
 662  * these two operations is that if a dirty page/buffer is encountered, it must
 663  * be waited upon, and not just skipped over.
 664  */
 665 int btrfs_fdatawrite_range(struct address_space *mapping, loff_t start,
 666                            loff_t end, int sync_mode)
 667 {
 668         struct writeback_control wbc = {
 669                 .sync_mode = sync_mode,
 670                 .nr_to_write = mapping->nrpages * 2,
 671                 .range_start = start,
 672                 .range_end = end,
 673                 .for_writepages = 1,
 674         };
 675         return btrfs_writepages(mapping, &wbc);
 676 }
 677
 678 /**
 679  * taken from mm/filemap.c because it isn't exported
 680  *
 681  * wait_on_page_writeback_range - wait for writeback to complete
 682  * @mapping:    target address_space
 683  * @start:      beginning page index
 684  * @end:        ending page index
 685  *
 686  * Wait for writeback to complete against pages indexed by start->end
 687  * inclusive
 688  */
 689 int btrfs_wait_on_page_writeback_range(struct address_space *mapping,
 690                                        pgoff_t start, pgoff_t end)
 691 {
 692         struct pagevec pvec;
 693         int nr_pages;
 694         int ret = 0;
 695         pgoff_t index;
 696
 697         if (end < start)
 698                 return 0;
 699
 700         pagevec_init(&pvec, 0);
 701         index = start;
 702         while ((index <= end) &&
 703                         (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 704                         PAGECACHE_TAG_WRITEBACK,
 705                         min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
 706                 unsigned i;
 707
 708                 for (i = 0; i < nr_pages; i++) {
 709                         struct page *page = pvec.pages[i];
 710
 711                         /* until radix tree lookup accepts end_index */
 712                         if (page->index > end)
 713                                 continue;
 714
 715                         wait_on_page_writeback(page);
 716                         if (PageError(page))
 717                                 ret = -EIO;
 718                 }
 719                 pagevec_release(&pvec);
 720                 cond_resched();
 721         }
 722
 723         /* Check for outstanding write errors */
 724         if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
 725                 ret = -ENOSPC;
 726         if (test_and_clear_bit(AS_EIO, &mapping->flags))
 727                 ret = -EIO;
 728
 729         return ret;
 730 }