Add an attribute to show multipath NUMA node per-path (scsi_disk).

The following is an example of reading the file:

$ cat /sys/devices/platform/host8/session1/target8:0:0/8:0:0:0/block/sdc:0/numa_
mpath_numa_nodes
0-3
$ cat /sys/devices/platform/host9/session2/target9:0:0/9:0:0:0/block/sdc:1/numa_
mpath_numa_nodes
$

Signed-off-by: John Garry <[email protected]>
---
 drivers/scsi/sd.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index f5922a9fe6c1b..52d9bc34bd666 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -4213,8 +4213,28 @@ static ssize_t sd_mpath_dev_show(struct device *dev,
 }
 static DEVICE_ATTR(mpath_dev, 0444, sd_mpath_dev_show, NULL);
 
+static ssize_t sd_mpath_numa_nodes_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 mpath_device *mpath_device = &scsi_mpath_dev->mpath_device;
+       struct sd_mpath_disk *sd_mpath_disk = sdkp->sd_mpath_disk;
+       struct mpath_disk *mpath_disk = sd_mpath_disk->mpath_disk;
+       struct mpath_head *mpath_head = mpath_disk->mpath_head;
+       struct scsi_mpath_head *scsi_mpath_head = mpath_head->drvdata;
+       struct mpath_iopolicy *mpath_iopolicy = &scsi_mpath_head->iopolicy;
+
+       return mpath_numa_nodes_show(mpath_head, mpath_device,
+                       mpath_iopolicy, buf);
+}
+static DEVICE_ATTR(mpath_numa_nodes, 0444, sd_mpath_numa_nodes_show, NULL);
+
 static struct attribute *sd_mpath_dev_attrs[] = {
        &dev_attr_mpath_dev.attr,
+       &dev_attr_mpath_numa_nodes.attr,
        NULL
 };
 
-- 
2.43.5


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