[PATCH 18/21] Btrfs: fix empty symlink after creating symlink and fsync parent dir

David Sterba
2016-06-03T15:43:27Z

From: Filipe Manana <fdmanana@suse.com>

commit 3f9749f6e9edcf8ec569fb542efc3be35e06e84a upstream.

If we create a symlink, fsync its parent directory, crash/power fail and
mount the filesystem, we end up with an empty symlink, which not only is
useless it's also not allowed in linux (the man page symlink(2) is well
explicit about that). So we just need to make sure to fully log an inode
if it's a symlink, to ensure its inline extent gets logged, ensuring the
same behaviour as ext3, ext4, xfs, reiserfs, f2fs, nilfs2, etc.

Example reproducer:

$ mkfs.btrfs -f /dev/sdb
$ mount /dev/sdb /mnt
$ mkdir /mnt/testdir
$ sync
$ ln -s /mnt/foo /mnt/testdir/bar
$ xfs_io -c fsync /mnt/testdir
<power fail>
$ mount /dev/sdb /mnt
$ readlink /mnt/testdir/bar
<empty string>

A test case for fstests follows soon.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
fs/btrfs/tree-log.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 23df70e7f884..a2cd42107945 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -5157,7 +5157,7 @@ static int log_new_dir_dentries(struct btrfs_trans_handle *trans,
}

ctx->log_new_dentries = false;
- if (type == BTRFS_FT_DIR)
+ if (type == BTRFS_FT_DIR || type == BTRFS_FT_SYMLINK)
log_mode = LOG_INODE_ALL;
btrfs_release_path(path);
ret = btrfs_log_inode(trans, root, di_inode,
--
2.7.1