btrfs: hold a ref on the root in open_ctree

We lookup the fs_root and put it in our fs_info directly, we should hold
a ref on this root for the lifetime of the fs_info.

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 ce36a4b..76b8887 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1537,6 +1537,7 @@ void btrfs_free_fs_info(struct btrfs_fs_info *fs_info)
        kfree(fs_info->free_space_root);
        kfree(fs_info->super_copy);
        kfree(fs_info->super_for_commit);
+       btrfs_put_fs_root(fs_info->fs_root);
        kvfree(fs_info);
 }
 
@@ -3206,6 +3207,13 @@ int __cold open_ctree(struct super_block *sb,
                goto fail_qgroup;
        }
 
+       if (!btrfs_grab_fs_root(fs_info->fs_root)) {
+               fs_info->fs_root = NULL;
+               err = -ENOENT;
+               btrfs_warn(fs_info, "failed to grab a ref on the fs tree");
+               goto fail_qgroup;
+       }
+
        if (sb_rdonly(sb))
                return 0;