btrfs: don't leak ret from do_chunk_alloc

BugLink: https://bugs.launchpad.net/bugs/1792392

commit 4559b0a7 upstream.

If we're trying to make a data reservation and we have to allocate a
data chunk we could leak ret == 1, as do_chunk_alloc() will return 1 if
it allocated a chunk.  Since the end of the function is the success path
just return 0.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/btrfs/extent-tree.c

@@ -4128,7 +4128,7 @@ int btrfs_alloc_data_chunk_ondemand(struct inode *inode, u64 bytes)
 				      data_sinfo->flags, bytes, 1);
 	spin_unlock(&data_sinfo->lock);
 
-	return ret;
+	return 0;
 }
 
 /*