From: Josef Bacik <josef@toxicpanda.com>
Date: Fri, 24 Jan 2020 09:32:54 -0500
Git-commit: 4c78e9f59632b5e635e51db9b68111288b38ff22
Patch-mainline: 5.7-rc1
References: bsc#1176019
Subject: [PATCH] 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>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/disk-io.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ce36a4b9c8a3..76b888728540 100644
--- 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;
 
-- 
2.26.2