Re: [PATCH] scsi_execute_async() should add to the tail of the queue

Steven Hayter
2006-12-20T21:54:33Z

Dan Aloni wrote:
> Hello,
>
> scsi_execute_async() has replaced scsi_do_req() a few versions ago,
> but it also incurred a change of behavior. I noticed that over-queuing
> a SCSI device using that function causes I/Os to be starved from
> low-level queuing for no justified reason.
>
> I think it makes much more sense to perserve the original behaviour
> of scsi_do_req() and add the request to the tail of the queue.

As far as I'm aware the way in which scsi_do_req() was to insert at the
head of the queue, leading to projects like SCST to come up with
scsi_do_req_fifo() as queuing multiple commands using scsi_do_req() with
constant head insertion might lead to out of order execution.

Just thought I'd throw some light on the history and what others have
done in the past.

Steve