btrfs: qgroup: return ENOTCONN instead of EINVAL when quotas are not enabled

commit 8a36e40 upstream.

[PROBLEM]
qgroup create/remove code is currently returning EINVAL when the user
tries to create a qgroup on a subvolume without quota enabled. EINVAL is
already being used for too many error scenarios so that is hard to
depict what is the problem.

[FIX]
Currently scrub and balance code return -ENOTCONN when the user tries to
cancel/pause and no scrub or balance is currently running for the
desired subvolume. Do the same here by returning -ENOTCONN  when a user
tries to create/delete/assing/list a qgroup on a subvolume without quota
enabled.

Reviewed-by: Qu Wenruo <[email protected]>
Signed-off-by: Marcos Paulo de Souza <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>
Signed-off-by: Harshvardhan Jha <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: marcosps

fs/btrfs/qgroup.c

@@ -1411,7 +1411,7 @@ int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
 	if (!fs_info->quota_root) {
-		ret = -EINVAL;
+		ret = -ENOTCONN;
 		goto out;
 	}
 	member = find_qgroup_rb(fs_info, src);
@@ -1470,7 +1470,7 @@ static int __del_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
 		return -ENOMEM;
 
 	if (!fs_info->quota_root) {
-		ret = -EINVAL;
+		ret = -ENOTCONN;
 		goto out;
 	}
 
@@ -1536,7 +1536,7 @@ int btrfs_create_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid)
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
 	if (!fs_info->quota_root) {
-		ret = -EINVAL;
+		ret = -ENOTCONN;
 		goto out;
 	}
 	quota_root = fs_info->quota_root;
@@ -1570,7 +1570,7 @@ int btrfs_remove_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid)
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
 	if (!fs_info->quota_root) {
-		ret = -EINVAL;
+		ret = -ENOTCONN;
 		goto out;
 	}
 
@@ -1621,7 +1621,7 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid,
 
 	mutex_lock(&fs_info->qgroup_ioctl_lock);
 	if (!fs_info->quota_root) {
-		ret = -EINVAL;
+		ret = -ENOTCONN;
 		goto out;
 	}