diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h index 91c994b569f3b8..6ed495ca7a311d 100644 --- a/fs/btrfs/btrfs_inode.h +++ b/fs/btrfs/btrfs_inode.h @@ -89,6 +89,16 @@ enum { BTRFS_INODE_FREE_SPACE_INODE, /* Set when there are no capabilities in XATTs for the inode. */ BTRFS_INODE_NO_CAP_XATTR, + /* + * Set if an error happened when doing a COW write before submitting a + * bio or during writeback. Used for both buffered writes and direct IO + * writes. This is to signal a fast fsync that it has to wait for + * ordered extents to complete and therefore not log extent maps that + * point to unwritten extents (when an ordered extent completes and it + * has the BTRFS_ORDERED_IOERR flag set, it drops extent maps in its + * range). + */ + BTRFS_INODE_COW_WRITE_ERROR, }; /* in memory btrfs inode */ diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 0c7c1b42028e3d..00670596bf065a 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1885,6 +1885,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) */ if (full_sync || btrfs_is_zoned(fs_info)) { ret = btrfs_wait_ordered_range(inode, start, len); + clear_bit(BTRFS_INODE_COW_WRITE_ERROR, &BTRFS_I(inode)->runtime_flags); } else { /* * Get our ordered extents as soon as possible to avoid doing @@ -1894,6 +1895,21 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync) btrfs_get_ordered_extents_for_logging(BTRFS_I(inode), &ctx.ordered_extents); ret = filemap_fdatawait_range(inode->i_mapping, start, end); + if (ret) + goto out_release_extents; + + /* + * Check and clear the BTRFS_INODE_COW_WRITE_ERROR now after + * starting and waiting for writeback, because for buffered IO + * it may have been set during the end IO callback + * (end_bbio_data_write() -> btrfs_finish_ordered_extent()) in + * case an error happened and we need to wait for ordered + * extents to complete so that any extent maps that point to + * unwritten locations are dropped and we don't log them. + */ + if (test_and_clear_bit(BTRFS_INODE_COW_WRITE_ERROR, + &BTRFS_I(inode)->runtime_flags)) + ret = btrfs_wait_ordered_range(inode, start, len); } if (ret) diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c index c5bdd674f55c53..35a413ce935d9e 100644 --- a/fs/btrfs/ordered-data.c +++ b/fs/btrfs/ordered-data.c @@ -388,6 +388,37 @@ bool btrfs_finish_ordered_extent(struct btrfs_ordered_extent *ordered, ret = can_finish_ordered_extent(ordered, page, file_offset, len, uptodate); spin_unlock_irqrestore(&inode->ordered_tree_lock, flags); + /* + * If this is a COW write it means we created new extent maps for the + * range and they point to unwritten locations if we got an error either + * before submitting a bio or during IO. + * + * We have marked the ordered extent with BTRFS_ORDERED_IOERR, and we + * are queuing its completion below. During completion, at + * btrfs_finish_one_ordered(), we will drop the extent maps for the + * unwritten extents. + * + * However because completion runs in a work queue we can end up having + * a fast fsync running before that. In the case of direct IO, once we + * unlock the inode the fsync might start, and we queue the completion + * before unlocking the inode. In the case of buffered IO when writeback + * finishes (end_bbio_data_write()) we queue the completion, so if the + * writeback was triggered by a fast fsync, the fsync might start + * logging before ordered extent completion runs in the work queue. + * + * The fast fsync will log file extent items based on the extent maps it + * finds, so if by the time it collects extent maps the ordered extent + * completion didn't happen yet, it will log file extent items that + * point to unwritten extents, resulting in a corruption if a crash + * happens and the log tree is replayed. Note that a fast fsync does not + * wait for completion of ordered extents in order to reduce latency. + * + * Set a flag in the inode so that the next fast fsync will wait for + * ordered extents to complete before starting to log. + */ + if (!uptodate && !test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags)) + set_bit(BTRFS_INODE_COW_WRITE_ERROR, &inode->runtime_flags); + if (ret) btrfs_queue_ordered_fn(ordered); return ret;