scsi: storvsc: use tagged SRB requests if supported by the device

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 63f6b1a..3209387 100644 (file)
--- 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: