Re: [Patch] QLogic qla2x00 driver fixes

[Patrick Mansfield <patmans@us.ibm.com>]

On Fri, Feb 25, 2005 at 06:57:39AM -0500, Doug Ledford wrote:
> On Fri, 2005-02-25 at 03:38 -0500, Jeff Garzik wrote:
> > Arjan van de Ven wrote:
> > > On Thu, 2005-02-24 at 23:21 -0500, Doug Ledford wrote:
> > > 
> > >>Don't use cmd->request->nr_hw_segments as it may not be initialized
> > >>(SG_IO in particular bypasses anything that initializes this and just
> > >>uses scsi_do_req to insert a scsi_request directly on the head of the
> > >>queue) 
> > > 
> > > 
> > > should we fix that in the SG_IO layer ?
> > 
> > Possibly/probably.

Doug,

What kernel did you hit this with? 

And same question as Doug G: is it via sg (not the block SG_IO)? sg uses
scsi_do_req(), block SG_IO doesn't.

Jens sent changes last August or so that fixed SG_IO (not sg) to always
set nr_hw_segments, change should be in 2.6.10. It is not obvious that his
change fixed this, I can't find the changeset or log.

> I'm not concerned with it personally.  The only reason that the scsi
> layer copies the block layer request struct into the scsi
> command/request is so that upon completion it has enough information to
> mark blocks as either up to date or not while at the same time allowing
> the scsi layer to free the original block request at queue time, not at
> completion time.  It was never intended to be used by low level drivers.

In 2.6, we no don't copy the request into the command:

struct scsi_cmnd {
	...
	struct request *request
	...
}

-- Patrick Mansfield