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Commit 761f1193 authored by Venkatesh Srinivas's avatar Venkatesh Srinivas Committed by Christoph Hellwig
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virtio-scsi: Implement change_queue_depth for virtscsi targets 



change_queue_depth allows changing per-target queue depth via sysfs.

It also allows the SCSI midlayer to ramp down the number of concurrent
inflight requests in response to a SCSI BUSY status response and allows
the midlayer to ramp the count back up to the device maximum when the
BUSY condition has resolved.

Signed-off-by: default avatarVenkatesh Srinivas <venkateshs@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 938ece71

drivers/scsi/virtio_scsi.c

+33 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <scsi/scsi_host.h>

#include <scsi/scsi_device.h>

#include <scsi/scsi_cmnd.h>

#include <scsi/scsi_tcq.h>

#include <linux/seqlock.h>



#define VIRTIO_SCSI_MEMPOOL_SZ 64
@@ -654,6 +655,36 @@ static int virtscsi_device_reset(struct scsi_cmnd *sc) 
	return virtscsi_tmf(vscsi, cmd);

}



/**

 * virtscsi_change_queue_depth() - Change a virtscsi target's queue depth

 * @sdev:	Virtscsi target whose queue depth to change

 * @qdepth:	New queue depth

 * @reason:	Reason for the queue depth change.

 */

static int virtscsi_change_queue_depth(struct scsi_device *sdev,

				       int qdepth,

				       int reason)

{

	struct Scsi_Host *shost = sdev->host;

	int max_depth = shost->cmd_per_lun;



	switch (reason) {

	case SCSI_QDEPTH_QFULL: /* Drop qdepth in response to BUSY state */

		scsi_track_queue_full(sdev, qdepth);

		break;

	case SCSI_QDEPTH_RAMP_UP: /* Raise qdepth after BUSY state resolved */

	case SCSI_QDEPTH_DEFAULT: /* Manual change via sysfs */

		scsi_adjust_queue_depth(sdev,

					scsi_get_tag_type(sdev),

					min(max_depth, qdepth));

		break;

	default:

		return -EOPNOTSUPP;

	}



	return sdev->queue_depth;

}



static int virtscsi_abort(struct scsi_cmnd *sc)

{

	struct virtio_scsi *vscsi = shost_priv(sc->device->host);
@@ -709,6 +740,7 @@ static struct scsi_host_template virtscsi_host_template_single = { 
	.this_id = -1,

	.cmd_size = sizeof(struct virtio_scsi_cmd),

	.queuecommand = virtscsi_queuecommand_single,

	.change_queue_depth = virtscsi_change_queue_depth,

	.eh_abort_handler = virtscsi_abort,

	.eh_device_reset_handler = virtscsi_device_reset,
@@ -726,6 +758,7 @@ static struct scsi_host_template virtscsi_host_template_multi = { 
	.this_id = -1,

	.cmd_size = sizeof(struct virtio_scsi_cmd),

	.queuecommand = virtscsi_queuecommand_multi,

	.change_queue_depth = virtscsi_change_queue_depth,

	.eh_abort_handler = virtscsi_abort,

	.eh_device_reset_handler = virtscsi_device_reset,