RE: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if supported by the device

[KY Srinivasan]

> -----Original Message-----
> From: Greg Kroah-Hartman [mailto:gregkh@xxxxxxxxxxxxxxxxxxx]
> Sent: Friday, March 10, 2017 7:22 AM
> To: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; Long Li
> <longli@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Martin K.
> Petersen <martin.petersen@xxxxxxxxxx>
> Subject: Re: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if
> supported by the device
> 
> On Fri, Mar 10, 2017 at 02:56:59PM +0000, Ben Hutchings wrote:
> > On Fri, 2017-03-10 at 10:08 +0100, Greg Kroah-Hartman wrote:
> > > 4.4-stable review patch.  If anyone has any objections, please let me
> know.
> > >
> > > ------------------
> > >
> > > From: Long Li <longli@xxxxxxxxxxxxx>
> > >
> > > commit 3cd6d3d9b1abab8dcdf0800224ce26daac24eea2 upstream.
> > >
> > > Properly set SRB flags when hosting device supports tagged queuing.
> > > This patch improves the performance on Fiber Channel disks.
> > [...]
> >
> > This looks more like a feature/optimisation than a bug fix.  Is this
> > really within the stable rules?
> 
> Making things work properly (i.e. i/o does not suck anymore), is ok for
> stable stuff.  KY, that's the case here, right?

If I recall correctly, this was needed for Fibre Channel SANs where without
this fix the performance was so bad to be almost unusable.

K. Y

> 
> thanks,
> 
> greg k-h