diff options
| -rw-r--r-- | fs/btrfs/file.c | 78 |
1 files changed, 63 insertions, 15 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index d5d5060..cdb7146 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1849,6 +1849,20 @@ int btrfs_release_file(struct inode *inode, struct file *filp) return 0; } +static int start_ordered_ops(struct inode *inode, loff_t start, loff_t end) +{ + int ret; + + atomic_inc(&BTRFS_I(inode)->sync_writers); + ret = filemap_fdatawrite_range(inode->i_mapping, start, end); + if (!ret && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, + &BTRFS_I(inode)->runtime_flags)) + ret = filemap_fdatawrite_range(inode->i_mapping, start, end); + atomic_dec(&BTRFS_I(inode)->sync_writers); + + return ret; +} + /* * fsync call for both files and directories. This logs the inode into * the tree log instead of forcing full commits whenever possible. @@ -1878,30 +1892,64 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) * multi-task, and make the performance up. See * btrfs_wait_ordered_range for an explanation of the ASYNC check. */ - atomic_inc(&BTRFS_I(inode)->sync_writers); - ret = filemap_fdatawrite_range(inode->i_mapping, start, end); - if (!ret && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, - &BTRFS_I(inode)->runtime_flags)) - ret = filemap_fdatawrite_range(inode->i_mapping, start, end); - atomic_dec(&BTRFS_I(inode)->sync_writers); + ret = start_ordered_ops(inode, start, end); if (ret) return ret; mutex_lock(&inode->i_mutex); - - /* - * We flush the dirty pages again to avoid some dirty pages in the - * range being left. - */ atomic_inc(&root->log_batch); full_sync = test_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(inode)->runtime_flags); + /* + * We might have have had more pages made dirty after calling + * start_ordered_ops and before acquiring the inode's i_mutex. + */ if (full_sync) { + /* + * For a full sync, we need to make sure any ordered operations + * start and finish before we start logging the inode, so that + * all extents are persisted and the respective file extent + * items are in the fs/subvol btree. + */ ret = btrfs_wait_ordered_range(inode, start, end - start + 1); - if (ret) { - mutex_unlock(&inode->i_mutex); - goto out; - } + } else { + /* + * Start any new ordered operations before starting to log the + * inode. We will wait for them to finish in btrfs_sync_log(). + * + * Right before acquiring the inode's mutex, we might have new + * writes dirtying pages, which won't immediately start the + * respective ordered operations - that is done through the + * fill_delalloc callbacks invoked from the writepage and + * writepages address space operations. So make sure we start + * all ordered operations before starting to log our inode. Not + * doing this means that while logging the inode, writeback + * could start and invoke writepage/writepages, which would call + * the fill_delalloc callbacks (cow_file_range, + * submit_compressed_extents). These callbacks add first an + * extent map to the modified list of extents and then create + * the respective ordered operation, which means in + * tree-log.c:btrfs_log_inode() we might capture all existing + * ordered operations (with btrfs_get_logged_extents()) before + * the fill_delalloc callback adds its ordered operation, and by + * the time we visit the modified list of extent maps (with + * btrfs_log_changed_extents()), we see and process the extent + * map they created. We then use the extent map to construct a + * file extent item for logging without waiting for the + * respective ordered operation to finish - this file extent + * item points to a disk location that might not have yet been + * written to, containing random data - so after a crash a log + * replay will make our inode have file extent items that point + * to disk locations containing invalid data, as we returned + * success to userspace without waiting for the respective + * ordered operation to finish, because it wasn't captured by + * btrfs_get_logged_extents(). + */ + ret = start_ordered_ops(inode, start, end); + } + if (ret) { + mutex_unlock(&inode->i_mutex); + goto out; } atomic_inc(&root->log_batch); |
