Clang static analysis reports this problem
ioctl.c:3333:8: warning: 3rd function call argument is an
  uninitialized value
    ret = exclop_start_or_cancel_reloc(fs_info,
cancel is only set in one branch of an if-check and is always used.  So
initialize to false.
Fixes: 1a15eb724aae ("btrfs: use btrfs_get_dev_args_from_path in dev removal ioctls")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: David Sterba <dsterba@suse.com>
        struct block_device *bdev = NULL;
        fmode_t mode;
        int ret;
-       bool cancel;
+       bool cancel = false;
 
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;