[PATCH] scsi: add attribute to set lun queue depth on all luns on shost

[James Smart <jsmart2021@gmail.com>]

There has been a desire to set the lun queue depth on all luns on
an shost. Today that is done by an external script looping through
discovered sdevs and set an sdev attribute.

This patch addes a shost attribute that will cycle through all
sdevs and set the lun queue depth.

Signed-off-by: James Smart <jsmart2021@gmail.com>
---
 drivers/scsi/scsi_sysfs.c | 49 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 677b5c5403d2..debb79be66c0 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -368,6 +368,50 @@ store_shost_eh_deadline(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(eh_deadline, S_IRUGO | S_IWUSR, show_shost_eh_deadline, store_shost_eh_deadline);
 
+static int
+sdev_set_queue_depth(struct scsi_device *sdev, int depth)
+{
+	struct scsi_host_template *sht = sdev->host->hostt;
+	int retval;
+
+	retval = sht->change_queue_depth(sdev, depth);
+	if (retval < 0)
+		return retval;
+
+	sdev->max_queue_depth = sdev->queue_depth;
+
+	return 0;
+}
+
+static ssize_t
+store_host_lun_queue_depth(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct scsi_host_template *sht = shost->hostt;
+	struct scsi_device *sdev;
+	int depth, retval;
+
+	if (!sht->change_queue_depth)
+		return -EINVAL;
+
+	depth = simple_strtoul(buf, NULL, 0);
+	if (depth < 1 || depth > shost->can_queue)
+		return -EINVAL;
+
+	shost_for_each_device(sdev, shost) {
+		retval = sdev_set_queue_depth(sdev, depth);
+		if (retval != 0)
+			sdev_printk(KERN_INFO, sdev,
+				"failed to set queue depth to %d (err %d)",
+				depth, retval);
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR(lun_queue_depth, S_IWUSR, NULL, store_host_lun_queue_depth);
+
 shost_rd_attr(unique_id, "%u\n");
 shost_rd_attr(cmd_per_lun, "%hd\n");
 shost_rd_attr(can_queue, "%hd\n");
@@ -411,6 +455,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
 	&dev_attr_prot_guard_type.attr,
 	&dev_attr_host_reset.attr,
 	&dev_attr_eh_deadline.attr,
+	&dev_attr_lun_queue_depth.attr,
 	NULL
 };
 
@@ -992,12 +1037,10 @@ 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 = sdev_set_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