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

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  [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if supported by the device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-10 12:50 +0100
    Re: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if  supported by the device Ben Hutchings <ben@decadent.org.uk> - 2017-03-10 16:00 +0100
      Re: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if  supported by the device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-10 16:30 +0100
        RE: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if  supported by the device KY Srinivasan <kys@microsoft.com> - 2017-03-10 16:40 +0100

#1597188 — [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if supported by the device

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.

Signed-off-by: Long Li <longli@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/storvsc_drv.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -135,6 +135,8 @@ struct hv_fc_wwn_packet {
 #define SRB_FLAGS_PORT_DRIVER_RESERVED		0x0F000000
 #define SRB_FLAGS_CLASS_DRIVER_RESERVED		0xF0000000
 
+#define SP_UNTAGGED			((unsigned char) ~0)
+#define SRB_SIMPLE_TAG_REQUEST		0x20
 
 /*
  * Platform neutral description of a scsi request -
@@ -1409,6 +1411,13 @@ static int storvsc_queuecommand(struct S
 	vm_srb->win8_extension.srb_flags |=
 		SRB_FLAGS_DISABLE_SYNCH_TRANSFER;
 
+	if (scmnd->device->tagged_supported) {
+		vm_srb->win8_extension.srb_flags |=
+		(SRB_FLAGS_QUEUE_ACTION_ENABLE | SRB_FLAGS_NO_QUEUE_FREEZE);
+		vm_srb->win8_extension.queue_tag = SP_UNTAGGED;
+		vm_srb->win8_extension.queue_action = SRB_SIMPLE_TAG_REQUEST;
+	}
+
 	/* Build the SRB */
 	switch (scmnd->sc_data_direction) {
 	case DMA_TO_DEVICE:

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#1597900 — Re: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if supported by the device

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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?

Ben.

-- 
Ben Hutchings
If you seem to know what you are doing, you'll be given more to do.

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#1597917 — 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?

thanks,

greg k-h

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#1597927 — RE: [PATCH 4.4 34/91] scsi: storvsc: use tagged SRB requests if supported by the device

> -----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

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