Hi Martin
Can you take your precious time to review this ?
Thanks in advice.
Jianchao
On 03/03/2018 09:54 AM, Jianchao Wang wrote:
> In scsi core, __scsi_queue_insert should just put request back on
> the queue and retry using the same command as before. However, for
> blk-mq, scsi_mq_requeue_cmd is employed here which will unprepare
> the request. To align with the semantics of __scsi_queue_insert,
> use blk_mq_requeue_request with kick_requeue_list == true and put
> the reference of scsi_device.
>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx>
> Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxx>
> ---
> Changelog:
> V3 -> V4:
> - modify the comment and make it more clearly
>
> V2 -> V3:
> - add comment to explain why we need a put_device in
> __scsi_queue_insert
> - add reviewed-by
>
> V1 -> V2:
> - add put_device on scsi_device->sdev_gendev
> drivers/scsi/scsi_lib.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index a86df9c..6ce33f6 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -191,7 +191,19 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
> */
> cmd->result = 0;
> if (q->mq_ops) {
> - scsi_mq_requeue_cmd(cmd);
> + /*
> + * Before a SCSI command is dispatched,
> + * get_device(&sdev->sdev_gendev) is called and the host,
> + * target and device busy counters are increased. Since
> + * requeuing a request causes these actions to be repeated and
> + * since scsi_device_unbusy() has already been called,
> + * put_device(&device->sdev_gendev) must still be called. Call
> + * put_device() after blk_mq_requeue_request() to avoid that
> + * removal of the SCSI device can start before requeueing has
> + * happened.
> + */
> + blk_mq_requeue_request(cmd->request, true);
> + put_device(&device->sdev_gendev);
> return;
> }
> spin_lock_irqsave(q->queue_lock, flags);
>
