[dm-devel] [PATCH 3/4] scsi_dh_rdac: Adding the match function for rdac device handler
Mike Snitzer
snitzer at redhat.com
Wed Nov 2 15:46:12 UTC 2011
On Wed, Nov 02 2011 at 11:23am -0400,
Moger, Babu <Babu.Moger at netapp.com> wrote:
> > -----Original Message-----
> > From: Hannes Reinecke [mailto:hare at suse.de]
> > Sent: Wednesday, November 02, 2011 2:21 AM
> > To: dm-devel at redhat.com
> > Subject: Re: [dm-devel] [PATCH 3/4] scsi_dh_rdac: Adding the match
> > function for rdac device handler
> >
> > On 11/01/2011 06:19 PM, Moger, Babu wrote:
> > > This patch introduces the match function for rdac device handler.
> > Without this,
> > > sometimes handler attach fails during the device_add. The match
> > function was
> > > introduced by this patch
> > > http://www.spinics.net/lists/linux-scsi/msg54284.html
> > >
> > > Signed-off-by: Babu Moger<babu.moger at netapp.com>
> > > ---
> > >
> > > --- linux/drivers/scsi/device_handler/scsi_dh_rdac.c.orig 2011-10-31
> > 11:25:44.000000000 -0500
> > > +++ linux/drivers/scsi/device_handler/scsi_dh_rdac.c 2011-10-31
> > 11:31:34.000000000 -0500
> > > @@ -819,6 +819,21 @@ static const struct scsi_dh_devlist rdac
> > > {NULL, NULL},
> > > };
> > >
> > > +static bool rdac_match(struct scsi_device *sdev)
> > > +{
> > > + int i;
> > > +
> > > + for (i = 0; rdac_dev_list[i].vendor; i++) {
> > > + if (!strncmp(sdev->vendor, rdac_dev_list[i].vendor,
> > > + strlen(rdac_dev_list[i].vendor))&&
> > > + !strncmp(sdev->model, rdac_dev_list[i].model,
> > > + strlen(rdac_dev_list[i].model))) {
> > > + return true;
> > > + }
> > > + }
> > > + return false;
> > > +}
> > > +
> > > static int rdac_bus_attach(struct scsi_device *sdev);
> > > static void rdac_bus_detach(struct scsi_device *sdev);
> > >
> > > @@ -831,6 +846,7 @@ static struct scsi_device_handler rdac_d
> > > .attach = rdac_bus_attach,
> > > .detach = rdac_bus_detach,
> > > .activate = rdac_activate,
> > > + .match = rdac_match,
> > > };
> > >
> > > static int rdac_bus_attach(struct scsi_device *sdev)
> > >
> > As stated in the other mail, I guess we would need to have a check
> > if the LUN is in ALUA mode.
> > And, btw, the _original_ intention was to allow vendor-specific
> > device_handler to do some better probing, eg querying some
> > vendor-specific VPD pages.
> > Especially for RDAC it would make far more sense to query the
> > existence and format of one of the RDAC-specific VPD pages (eg 0xC2,
> > 0xC4, or 0xC8) and use that for matching.
> > Then you could do away with the vendor/model array altogether here
> > and we wouldn't need to update the rdac handler every time a new
> > array comes out or has been rebranded by some OEM.
>
> OK. I will add the check for TPGS. I will send the patches tomorrow.
> For sending the VPD pages(0xC2, 0xC4 and 0xC8), I think we need be little careful here.
> This includes sending these commands to every possible device in the system. That is what we want to avoid.
> I will investigate more on that. That will be my next set of patches independent of this.
Much appreciated. I agree with Hannes, ideally we wouldn't need the
rdac dev_list.
What about the issue where the appropriate scsi_dh isn't attached during
scan (resulting in boot failures, trespasses, etc)?
Hannes, I know you had plans for how to address the early scsi_dh
attachment (and this match() work is a great step forward). I just
wanted to touch base with you on what your current vision is on how to
achieve proper early scsi_dh attachment (and what the remaining TODO
is).
Thanks,
Mike
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