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

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>

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 0f636cc..4ccbcad 100644 (file)
--- 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 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: