[PATCH v3 1/3] scsi: refactor sdev lun queue depth setting via sysfs

[James Smart <jsmart2021@gmail.com>]

In preparation for allowing other attributes and routines to change
the current and max lun queue depth on an sdev, refactor the sysfs
sdev attribute change routine. The refactoring creates a new scsi-internal
routine, scsi_change_max_queue_depth(), which changes a devices current
and max queue value.

The new routine is placed next to the routine, scsi_change_queue_depth(),
which is used by most lldds to implement a queue depth change.

Signed-off-by: James Smart <jsmart2021@gmail.com>

---
v3:
  revert -ENOTSUPP status on shost template check back to -EINVAL
---
 drivers/scsi/scsi.c       | 22 ++++++++++++++++++++++
 drivers/scsi/scsi_priv.h  |  1 +
 drivers/scsi/scsi_sysfs.c |  7 ++-----
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 930e4803d888..195c0b11260a 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -249,6 +249,28 @@ int scsi_change_queue_depth(struct scsi_device *sdev, int depth)
 }
 EXPORT_SYMBOL(scsi_change_queue_depth);
 
+/*
+ * scsi_change_max_queue_depth - change the max queue depth for a device.
+ * @sdev: SCSI Device in question
+ * @depth: number of commands allowed to be queued to the driver
+ *
+ * Calls the device's transport to validate and change the queue depth,
+ * then stores the new maximum on the device.
+ */
+int
+scsi_change_max_queue_depth(struct scsi_device *sdev, int depth)
+{
+	int retval;
+
+	retval = sdev->host->hostt->change_queue_depth(sdev, depth);
+	if (retval < 0)
+		return retval;
+
+	sdev->max_queue_depth = sdev->queue_depth;
+
+	return 0;
+}
+
 /**
  * scsi_track_queue_full - track QUEUE_FULL events to adjust queue depth
  * @sdev: SCSI Device in question
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 3bff9f7aa684..5c288cf3ae64 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -41,6 +41,7 @@ static inline void scsi_log_send(struct scsi_cmnd *cmd)
 static inline void scsi_log_completion(struct scsi_cmnd *cmd, int disposition)
 	{ };
 #endif
+int scsi_change_max_queue_depth(struct scsi_device *sdev, int depth);
 
 /* scsi_devinfo.c */
 
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 677b5c5403d2..d4e9ad9a6f18 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -982,9 +982,8 @@ sdev_store_queue_depth(struct device *dev, struct device_attribute *attr,
 {
 	int depth, retval;
 	struct scsi_device *sdev = to_scsi_device(dev);
-	struct scsi_host_template *sht = sdev->host->hostt;
 
-	if (!sht->change_queue_depth)
+	if (!sdev->host->hostt->change_queue_depth)
 		return -EINVAL;
 
 	depth = simple_strtoul(buf, NULL, 0);
@@ -992,12 +991,10 @@ sdev_store_queue_depth(struct device *dev, struct device_attribute *attr,
 	if (depth < 1 || depth > sdev->host->can_queue)
 		return -EINVAL;
 
-	retval = sht->change_queue_depth(sdev, depth);
+	retval = scsi_change_max_queue_depth(sdev, depth);
 	if (retval < 0)
 		return retval;
 
-	sdev->max_queue_depth = sdev->queue_depth;
-
 	return count;
 }
 sdev_show_function(queue_depth, "%d\n");
-- 
2.13.7