btrfs: reset fs_root to NULL on error in open_ctree

commit 315bf8ef914f31d51d084af950703aa1e09a728c upstream.

While running my error injection script I hit a panic when we tried to
clean up the fs_root when freeing the fs_root.  This is because
fs_info->fs_root == PTR_ERR(-EIO), which isn't great.  Fix this by
setting fs_info->fs_root = NULL; if we fail to read the root.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b0ac21c..e17d6bc 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3203,6 +3203,7 @@ retry_root_backup:
        if (IS_ERR(fs_info->fs_root)) {
                err = PTR_ERR(fs_info->fs_root);
                btrfs_warn(fs_info, "failed to read fs tree: %d", err);
+               fs_info->fs_root = NULL;
                goto fail_qgroup;
        }