zbd: finish zones with remainder smaller than minimum write block size

zbd: finish zones with remainder smaller than minimum write block size

When zonemode is zbd and block size is not divisor of zone size, write
target zone selection does not work as expected. When the write is
random write and the device has max open zone limit, the random write is
repeated to the zones selected up to the max open zone limit. All writes
are repeated only to the zones. When the write is sequential write,
write is done only for the first zone. The cause of such unexpected zone
selection is current write target zone selection logic. It selects write
target zones within open zones. When block size is not divisor of zone
size, the selected open zone has only remainder of writable blocks
smaller than the block size. Fio resets such zone after zone selection
and continues writing to it. This zone reset is required not to exceed
the limit of max_open_zones option or max_active_zone limit of the zoned
device, but it does not simulate the workload.

To avoid the zone reset and unexpected write to same zone, fix write
target zone handling of zones with remainder smaller than write block
size. Do not reset but finish such zone not to exceed the max_open_zones
option and max_active_zone limit. Then choose the zone next to the
finished zone as write target. To implement this, add the helper
function zbd_finish_zone().

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Tested-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>