The double loop is just checking if the page for the vertical stripe
is allocated.

We can easily convert it to single loop and get rid of @stripe variable.
Signed-off-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>