Re: [PATCH 1/2] scsi_transport_fc: FC pass through support via bsg interface - revised

FUJITA Tomonori
2008-10-27T04:12:39Z

On Sun, 26 Oct 2008 11:38:04 +0200
Boaz Harrosh <bharrosh@panasas.com> wrote:

> FUJITA Tomonori wrote:
> > CC'ed Jens,
> >
> > On Wed, 22 Oct 2008 19:27:35 -0700
> > Seokmann Ju <seokmann.ju@qlogic.com> wrote:
> >
> >> And it seems like that the panic is happening due to the fact that
> >> blk_delete_timer() is not called upon having completion of the service.
> >> In other words, the block layer calls blk_add_timer() prior to
> >> dispatch the service but, it doesn't call blk_delete_timer() when it
> >> returned.
> >
> > Yeah, we need to call blk_delete_timer somewhere.
> >
> >
> >> Just for heck of it, I've tried out by adding blk_delete_timer() in
> >> the ~/block/blk-exec.c:blk_end_sync_rq() and it seems fixes the problem.
> >
> > I think blk_end_sync_rq() is not the good place. From the perspective
> > of bsg, we need to handle both blk_execute_rq_nowait and
> > blk_execute_rq.
> >
> >
> >> Seems like that there are APIs in the block layer that are call the
> >> blk_delete_timer(), including,
> >> - blk_end_io()
> >> - __blk_end_request()
> >>
> >> Could you guide me what is right way to fix the problem?
> >
> > Exporting blk_delete_timer is one option, but it doesn't look very
> > nice (since the block layer doesn't export any details about its timer
> > infrastructure), I think. Modifying blk_end_io() to make it usable for
> > requests via something like bsg might be better.
> >
> > Anyway, we need to ask Jens.
> >
> > Jens, fc people have working on fc pass through support via bsg, which
> > hooks bsg's request queue on fc transport objects (We did the similar
> > thing for sas transport).
> >
> > We want the timeout feature for fc pass through and I think that it's
> > nice to use the block layer timeout feature for it. But the users of
> > bsg request queue don't need (or call) APIs such as
> > end_that_request_last to call blk_delete_timer internally. How should
> > these users call blk_delete_timer?
>
> TOMO Hi
> If a command is queued by bsg to a scsi device, which is posible. Then
> blk_end_request() is called by scsi-ml. So it does work.

It doesn't work for bsg's scsi transport pass through stuff such as
SMP (sas management protocol, we already support) and FC. Virtually,
they don't use scsi-ml.

> I think that all block-queue consumers should call one of
> blk_end_request(),

This is kinda what I suggested in the previous mail but as I wrote,
some of them don't now.

> there are lots to choose from. We don't need
> a new API. It will work with or without data, and it does what
> you want.