[PATCH v9 15/29] scsi-multipath: support iopolicy

[John Garry <john.garry@linux.dev>]

Add support to set the multipath iopolicy.

The iopolicy member is per scsi_mpath_head structure.

A module param is added so that the default iopolicy may be set.

Signed-off-by: John Garry <john.garry@linux.dev>
---
 drivers/scsi/scsi_multipath.c | 52 +++++++++++++++++++++++++++++++++++
 include/scsi/scsi_multipath.h |  3 ++
 2 files changed, 55 insertions(+)

diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
index 092975e0aca1..baf4ca73f8c9 100644
--- a/drivers/scsi/scsi_multipath.c
+++ b/drivers/scsi/scsi_multipath.c
@@ -61,6 +61,23 @@ static const struct kernel_param_ops multipath_param_ops = {
 module_param_cb(multipath, &multipath_param_ops, &scsi_multipath, 0444);
 MODULE_PARM_DESC(multipath, "turn on native multipath support, options: on, off, always");
 
+static enum mpath_iopolicy_e iopolicy = MPATH_IOPOLICY_NUMA;
+
+static int scsi_mpath_set_iopolicy_param(const char *val, const struct kernel_param *kp)
+{
+	return mpath_set_iopolicy(val, &iopolicy);
+}
+
+static int scsi_mpath_get_iopolicy_param(char *buf, const struct kernel_param *kp)
+{
+	return mpath_get_iopolicy(buf, iopolicy);
+}
+
+module_param_call(multipath_iopolicy, scsi_mpath_set_iopolicy_param,
+		scsi_mpath_get_iopolicy_param, &iopolicy, 0644);
+MODULE_PARM_DESC(multipath_iopolicy,
+	"Default multipath I/O policy; 'numa' (default), 'round-robin' or 'queue-depth'");
+
 static int scsi_mpath_unique_lun_id(struct scsi_device *sdev)
 {
 	struct scsi_mpath_device *scsi_mpath_dev = sdev->scsi_mpath_dev;
@@ -101,8 +118,41 @@ static ssize_t scsi_mpath_device_vpd_id_show(struct device *dev,
 }
 static DEVICE_ATTR(vpd_id, S_IRUGO, scsi_mpath_device_vpd_id_show, NULL);
 
+static ssize_t scsi_mpath_device_iopolicy_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct scsi_mpath_head *scsi_mpath_head =
+		container_of(dev, struct scsi_mpath_head, dev);
+	struct mpath_head *mpath_head = &scsi_mpath_head->mpath_head;
+
+	if (!mpath_iopolicy_store(&scsi_mpath_head->iopolicy, buf))
+		return -EINVAL;
+
+	mpath_clear_paths(mpath_head);
+	mpath_schedule_requeue_work(mpath_head);
+	/*
+	 * Ensure requeue work completes, as this work could run later when
+	 * the mpath_head is gone.
+	 */
+	flush_work(&mpath_head->requeue_work);
+	return count;
+}
+
+static ssize_t scsi_mpath_device_iopolicy_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct scsi_mpath_head *scsi_mpath_head =
+		container_of(dev, struct scsi_mpath_head, dev);
+
+	return mpath_iopolicy_show(&scsi_mpath_head->iopolicy, buf);
+}
+
+static DEVICE_ATTR(iopolicy, S_IRUGO | S_IWUSR,
+		scsi_mpath_device_iopolicy_show, scsi_mpath_device_iopolicy_store);
+
 static struct attribute *scsi_mpath_device_attrs[] = {
 	&dev_attr_vpd_id.attr,
+	&dev_attr_iopolicy.attr,
 	NULL
 };
 
@@ -206,6 +256,8 @@ static struct scsi_mpath_head *scsi_mpath_alloc_head(char *vpd_id)
 	if (mpath_head_init(&scsi_mpath_head->mpath_head))
 		goto out_free;
 	scsi_mpath_head->mpath_head.mpdt = &smpdt;
+	scsi_mpath_head->iopolicy = iopolicy;
+	scsi_mpath_head->mpath_head.iopolicy = &scsi_mpath_head->iopolicy;
 
 	strscpy(scsi_mpath_head->vpd_id, vpd_id,
 		SCSI_MPATH_DEVICE_ID_LEN);
diff --git a/include/scsi/scsi_multipath.h b/include/scsi/scsi_multipath.h
index d224a15ce9c2..d6f290b84f7f 100644
--- a/include/scsi/scsi_multipath.h
+++ b/include/scsi/scsi_multipath.h
@@ -25,6 +25,7 @@ struct scsi_mpath_head {
 	struct list_head	entry;
 	struct ida		ida;
 	struct kref		ref;
+	enum mpath_iopolicy_e	iopolicy;
 	struct device		dev;
 	int			index;
 };
@@ -40,6 +41,8 @@ struct scsi_mpath_device {
 
 #define to_scsi_mpath_device(d) \
 	container_of(d, struct scsi_mpath_device, mpath_device)
+#define to_scsi_mpath_head(d) \
+	container_of(d, struct scsi_mpath_head, mpath_head)
 
 int scsi_mpath_dev_alloc(struct scsi_device *sdev);
 void scsi_mpath_dev_release(struct scsi_device *sdev);
-- 
2.43.0