io_u: ensure we generate the full length of block sizes

Since we round down, we can miss the last entry. This ensures that
if we do:

bsrange=4k-16k

we actually get an even split of 4,8,12,16k ios.

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

io_u.c

@@ -541,10 +541,8 @@ static unsigned int get_next_buflen(struct thread_data *td, struct io_u *io_u,
 		r = __rand(&td->bsrange_state[ddir]);
 
 		if (!td->o.bssplit_nr[ddir]) {
-			buflen = 1 + (unsigned int) ((double) maxbs *
+			buflen = minbs + (unsigned int) ((double) maxbs *
 					(r / (frand_max + 1.0)));
-			if (buflen < minbs)
-				buflen = minbs;
 		} else {
 			long long perc = 0;
 			unsigned int i;