[PATCH v8 27/27] scsi: sd: add mpath_queue_depth dev attribute

[John Garry <john.g.garry@oracle.com>]

From: John Garry <john.garry@linux.dev>

Add a queue_depth file so that the multipath dynamic queue depth can be
looked up from per-path gendisk (scsi_disk) directory.

Signed-off-by: John Garry <john.garry@linux.dev>
---
 drivers/scsi/sd.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index bf02f14705518..84f17285bfa56 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -4176,9 +4176,28 @@ static ssize_t sd_mpath_numa_nodes_show(struct device *dev,
 }
 static DEVICE_ATTR(mpath_numa_nodes, 0444, sd_mpath_numa_nodes_show, NULL);
 
+static ssize_t sd_mpath_queue_depth_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct gendisk *gd = dev_to_disk(dev);
+	struct scsi_disk *sdkp = gd->private_data;
+	struct scsi_device *sdev = sdkp->device;
+	struct scsi_mpath_device *scsi_mpath_dev = sdev->scsi_mpath_dev;
+	struct scsi_mpath_head *scsi_mpath_head =
+				scsi_mpath_dev->scsi_mpath_head;
+	struct Scsi_Host *shost = sdev->host;
+
+	if (!mpath_qd_iopolicy(&scsi_mpath_head->iopolicy))
+		return 0;
+
+	return sysfs_emit(buf, "%d\n", atomic_read(&shost->mpath_nr_active));
+}
+static DEVICE_ATTR(mpath_queue_depth, 0444, sd_mpath_queue_depth_show, NULL);
+
 static struct attribute *sd_mpath_dev_attrs[] = {
 	&dev_attr_mpath_dev.attr,
 	&dev_attr_mpath_numa_nodes.attr,
+	&dev_attr_mpath_queue_depth.attr,
 	NULL
 };
 
-- 
2.43.7