[PATCH 3/4] btrfs: disable the device add feature for temp-fsid

[Anand Jain <anand.jain@oracle.com>]

The device addition operation will transform the cloned temp-fsid mounted
device into a multi-device filesystem. Therefore, it is marked as
unsupported.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/ioctl.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 848b7e6f6421..7d8d217cf5fd 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2635,6 +2635,12 @@ static long btrfs_ioctl_add_dev(struct btrfs_fs_info *fs_info, void __user *arg)
 		return -EINVAL;
 	}
 
+	if (fs_info->fs_devices->temp_fsid) {
+		btrfs_err(fs_info,
+			  "device add not supported on cloned temp-fsid mount");
+		return -EINVAL;
+	}
+
 	if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_ADD)) {
 		if (!btrfs_exclop_start_try_lock(fs_info, BTRFS_EXCLOP_DEV_ADD))
 			return BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
-- 
2.38.1