btrfs: reset fs_root to NULL on error in open_ctree

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>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d7fec89974cb3835a5ce612dfad97c053d320b3f..197352f23534806c67ab19e2f73112cd6626c674 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3200,6 +3200,7 @@ int __cold open_ctree(struct super_block *sb,
        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;
        }