zbd: avoid write with rwmixwrite=0 option

zbd: avoid write with rwmixwrite=0 option

Since the commit fb0259fb276a ("zbd: Ensure first I/O is write for
random read/write to sequential zones"), fio issues write as the first
I/O when zonemode=zbd and rw=randrw options are specified. However, fio
issues the first write even when rwmixwrite=0 option is specified. Users
do not expect such write and it confuses the users. To avoid the
confusion, suppress the write by referring td->o.rwmix[DDIR_WRITE].

Fixes: fb0259fb276a ("zbd: Ensure first I/O is write for random read/write to sequential zones")
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20231220005846.1371456-2-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>