Fail if we can't satisfy the minimum block size

Commit 799441286648bdced4f42d3040f37fd2e35eaf1d introduced a bug
where if we cannot satisfy the minimum block size from a given
offset, then we will loop forever trying to do that. Fix that bug
checking early if it is indeed a possible thing to satisfy, if
not give up.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 file changed