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

Jens Axboe
2006-12-19T11:25:06Z

On Tue, Dec 19 2006, Arjan van de Ven wrote:
> On Tue, 2006-12-19 at 10:35 +0200, 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.
>
> Hi,
>
> some things should really be added to the head of the queue, like
> maintenance requests and error handling requests. Are you sure this is
> the right change? At least I'd expect 2 apis, one for a head and one for
> a "normal" queueing...

It does sounds broken - head insertion should only be used for careful
internal commands, not be the default way user issued commands. Looking
at the current users, the patch makes sense to me.

--
Jens Axboe