zbd: Avoid excessive zone resets

zbd: Avoid excessive zone resets

When zbd_reset_zone() is called for a zone repeatedly, reset zone command
is issued multiple times to a single zone even though its status is
empty. This is excessive and meaningless. Especially when zones are reset
at file set up with multiple jobs, zone reset is repeated for each job
and delays fio work load start.

To avoid the repeated zone resets, check the write pointer of the zone
before issuing zone reset command. If the write pointer is at the zone
start, do not reset the zone and just return.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>