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
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