On Thu, Mar 21, 2019 at 11:21:20AM +0800, zhengbin wrote:
> When I use dd test a SCSI device which use blk-mq in the following steps:
> 1.echo "blocked" >/sys/block/sda/device/state
> 2.dd if=/dev/sda of=/mnt/t.log bs=1M count=10
> 3.echo "running" >/sys/block/sda/device/state
> dd should finish this work after step 3, unfortunately, still hung.
>
> After step2, the key code process is like this:
> blk_mq_dispatch_rq_list-->scsi_queue_rq-->prep_to_mq
>
> prep_to_mq will return BLK_STS_RESOURCE, and scsi_queue_rq will transter
> it to BLK_STS_DEV_RESOURCE, which means that driver can guarantee that
> IO dispatch will be triggered in future when the resource is available.
> Need to follow the rule if we set the device state to running.
IMO, it is the correct direction for fixing the issue.
>
> Signed-off-by: zhengbin <zhengbin13@xxxxxxxxxx>
> ---
> drivers/scsi/scsi_sysfs.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 6a9040f..ce60408 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -770,7 +770,20 @@ store_state_field(struct device *dev, struct device_attribute *attr,
> return -EINVAL;
>
> mutex_lock(&sdev->state_mutex);
> + enum scsi_device_state oldstate = sdev->sdev_state;
> ret = scsi_device_set_state(sdev, state);
> + if (ret == 0) {
> + /* If device use blk-mq, the device state changes from
> + * SDEV_BLOCK to SDEV_RUNNING, we need to run hw queue
> + * to avoid io hung.
> + */
> + if ((state == SDEV_RUNNING) && (oldstate == SDEV_BLOCK)) {
> + struct request_queue *q = sdev->request_queue;
It is fine to run queue unconditionally in case of 'state ==
SDEV_RUNNING'.
> +
> + if (q->mq_ops)
The above check isn't needed.
> + blk_mq_run_hw_queues(q, true);
I suggest to move blk_mq_run_hw_queues() out of the mutex for
avoiding any potential trouble.
Thanks,
Ming
