linux-kernel - [PATCH 4/6] storvsc: use tagged SRB requests if supported by the device

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Message-Id: <1481769963-2069-4-git-send-email-kys@exchange.microsoft.com>
Date:   Wed, 14 Dec 2016 18:46:01 -0800
From:   kys@...hange.microsoft.com
To:     linux-kernel@...r.kernel.org, devel@...uxdriverproject.org,
        ohering@...e.com, linux-scsi@...r.kernel.org, apw@...onical.com,
        vkuznets@...hat.com, jasowang@...hat.com,
        martin.petersen@...cle.com, hare@...e.de,
        James.Bottomley@...senPartnership.com
Cc:     Long Li <longli@...rosoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>, <stable@...r.kernel.org>
Subject: [PATCH 4/6] storvsc: use tagged SRB requests if supported by the device

From: Long Li <longli@...rosoft.com>

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@...rosoft.com>
Reviewed-by: K. Y. Srinivasan <kys@...rosoft.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
Cc: <stable@...r.kernel.org>
---
 drivers/scsi/storvsc_drv.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 63f6b1a..3209387 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -136,6 +136,8 @@ 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 -
@@ -1549,6 +1551,13 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
 	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:
-- 
1.7.4.1