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Date: Sun, 6 Jul 2014 16:39:27 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-scsi@...r.kernel.org,
Venkatesh Srinivas <venkateshs@...gle.com>
Subject: [PATCH 2/2] virtio-scsi: Implement change_queue_depth for virtscsi targets
From: Venkatesh Srinivas <venkateshs@...gle.com>
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@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
drivers/scsi/virtio_scsi.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index f67a872de14b..8fd0b21ce13a 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -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,
--
1.8.3.1
--
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