+int dev_to_fsid(const char *dev, u8 *fsid)
+{
+ struct btrfs_super_block *disk_super;
+ char buf[BTRFS_SUPER_INFO_SIZE];
+ int ret;
+ int fd;
+
+ fd = open(dev, O_RDONLY);
+ if (fd < 0) {
+ ret = -errno;
+ return ret;
+ }
+
+ disk_super = (struct btrfs_super_block *)buf;
+ ret = btrfs_read_dev_super(fd, disk_super,
+ BTRFS_SUPER_INFO_OFFSET, SBREAD_DEFAULT);
+ if (ret)
+ goto out;
+
+ memcpy(fsid, disk_super->fsid, BTRFS_FSID_SIZE);
+ ret = 0;
+
+out:
+ close(fd);
+ return ret;
+}
+