btrfs: skip compression property for anything other than files and dirs

The compression property only has effect on regular files and directories
(so that it's propagated to files and subdirectories created inside a
directory). For any other inode type (symlink, fifo, device, socket),
it's pointless to set the compression property because it does nothing
and ends up unnecessarily wasting leaf space due to the pointless xattr
(75 or 76 bytes, depending on the compression value). Symlinks in
particular are very common (for example, I have almost 10k symlinks under
/etc, /usr and /var alone) and therefore it's worth to avoid wasting
leaf space with the compression xattr.

For example, the compression property can end up on a symlink or character
device implicitly, through inheritance from a parent directory

  $ mkdir /mnt/testdir
  $ btrfs property set /mnt/testdir compression lzo

  $ ln -s yadayada /mnt/testdir/lnk
  $ mknod /mnt/testdir/dev c 0 0

Or explicitly like this:

  $ ln -s yadayda /mnt/lnk
  $ setfattr -h -n btrfs.compression -v lzo /mnt/lnk

So skip the compression property on inodes that are neither a regular
file nor a directory.

CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 367bb87b66df..85691dc2232f 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -408,6 +408,9 @@ static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
 	if (ret)
 		return ret;
 
+	if (btrfs_ignore_prop(BTRFS_I(inode), name))
+		return 0;
+
 	trans = btrfs_start_transaction(root, 2);
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);