From: KY Srinivasan <kys@microsoft.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ben Hutchings <ben@decadent.org.uk>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Long Li <longli@microsoft.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>
Subject: RE: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if
 supported by the device
Thread-Topic: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if
 supported by the device
Thread-Index: AQHSmX50B7mdoDI2O0KSg0QwBrhf/aGOKiWAgAAG24CAAAFoIA==
Date: Fri, 10 Mar 2017 15:29:49 +0000
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References: <20170310083900.730556986@linuxfoundation.org>
 <20170310083902.482819326@linuxfoundation.org>
 <1489157819.2593.9.camel@decadent.org.uk> <20170310152131.GA20522@kroah.com>
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> -----Original Message-----
> From: Greg Kroah-Hartman [mailto:gregkh@linuxfoundation.org]
> Sent: Friday, March 10, 2017 7:22 AM
> To: Ben Hutchings <ben@decadent.org.uk>
> Cc: linux-kernel@vger.kernel.org; stable@vger.kernel.org; Long Li
> <longli@microsoft.com>; KY Srinivasan <kys@microsoft.com>; Martin K.
> Petersen <martin.petersen@oracle.com>
> 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@microsoft.com>
> > >
> > > 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