> -----Original Message-----
> From: KY Srinivasan
> Sent: Thursday, November 17, 2011 11:53 PM
> To: 'James Bottomley'
> Cc: [email protected]; [email protected];
> [email protected]; [email protected]; linux-
> [email protected]; [email protected]; [email protected]
> Subject: RE: [PATCH 1/1] Staging: hv: storvsc: Move the storage driver out of
> the
> staging area
>
>
>
> > -----Original Message-----
> > From: James Bottomley [mailto:[email protected]]
> > Sent: Thursday, November 17, 2011 1:27 PM
> > To: KY Srinivasan
> > Cc: [email protected]; [email protected];
> > [email protected]; [email protected]; linux-
> > [email protected]; [email protected]; [email protected]
> > Subject: Re: [PATCH 1/1] Staging: hv: storvsc: Move the storage driver out
> > of
> the
> > staging area
> >
> > On Tue, 2011-11-08 at 10:13 -0800, K. Y. Srinivasan wrote:
> > > The storage driver (storvsc_drv.c) handles all block storage devices
> > > assigned to Linux guests hosted on Hyper-V. This driver has been in the
> > > staging tree for a while and this patch moves it out of the staging area.
> > > As per Greg's recommendation, this patch makes no changes to the
> staging/hv
> > > directory. Once the driver moves out of staging, we will cleanup the
> > > staging/hv directory.
> > >
> > > This patch includes all the patches that I have sent against the
> > > staging/hv
> > > tree to address the comments I have gotten to date on this storage driver.
> >
> > First comment is that it would have been easier to see the individual
> > patches for comment before you committed them.
>
> I am not sure if the patches have been committed yet. All patches were sent
> to various mailing lists and you were copied as well. In the future, I will
> include
> the scsi mailing list in the set of lists I include for the staging patches.
Greg has checked in these patches now.
>
> >
> > The way you did mempool isn't entirely right: the problem is that to
> > prevent a memory to I/O deadlock we need to ensure forward progress on
> > the drain device. Just having 64 commands available to the host doesn't
> > necessarily achieve this because LUN1 could consume them all and starve
> > LUN0 which is the drain device leading to the deadlock, so the mempool
> > really needs to be per device using slave_alloc.
>
Presently, Linux on Hyper-V can only boot from IDE devices. While IDE devices
are
handled via this stor driver, the way we handle them is a little different
compared
to block devices configured as scsi devices:
For IDE devices; we have a HBA per LUN. Given that for a long time the drain
device will
be an IDE device, my current implementation does address the concern that you
had raised
with regards to deadlock avoidance.
>
> >
> > +static int storvsc_device_alloc(struct scsi_device *sdevice)
> > +{
> > + /*
> > + * This enables luns to be located sparsely. Otherwise, we may not
> > + * discovered them.
> > + */
> > + sdevice->sdev_bflags |= BLIST_SPARSELUN | BLIST_LARGELUN;
> > + return 0;
> > +}
> >
> > Looks bogus ... this should happen automatically for SCSI-3 devices ...
> > unless your hypervisor has some strange (and wrong) identification? I
> > really think you want to use SCSI-3 because it will do report LUN
> > scanning, which consumes far fewer resources.
>
Done.
>
> >
> > I still think you need to disable clustering and junk the bvec merge
> > function. Your object seems to be to accumulate in page size multiples
> > (and not aggregate over this) ... that's what clustering is designed to
> > do.
Done. James, I am going to send you (and the scsi mailing list) the patches
addressing
your comments. I will also send out a consolidated patch for getting the driver
out of
staging as well. I would like to thank you for your help in cleaning up this
driver.
Regards,
K. Y
_______________________________________________
devel mailing list
[email protected]
http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
