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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: Venkatesh Srinivas <venkateshs@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Venkatesh Srinivas 2014-07-06 16:39:27 +02:00 committed by Christoph Hellwig
parent 938ece711c
commit 761f1193f2
1 changed files with 33 additions and 0 deletions
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33
drivers/scsi/virtio_scsi.c
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@ -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,