[PATCH v2 04/18] scsi-multipath: support iopolicy

[John Garry]

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.g.garry at oracle.com>
---
 drivers/scsi/scsi_multipath.c | 54 +++++++++++++++++++++++++++++++++++
 include/scsi/scsi_multipath.h |  1 +
 2 files changed, 55 insertions(+)

diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
index 31ab1d477c686..c6ae02644fdf4 100644
--- a/drivers/scsi/scsi_multipath.c
+++ b/drivers/scsi/scsi_multipath.c
@@ -60,6 +60,23 @@ 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 int 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;
@@ -95,8 +112,36 @@ 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, count))
+		return -EINVAL;
+
+	mpath_clear_paths(mpath_head);
+	mpath_schedule_requeue_work(mpath_head);
+	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
 };
 
@@ -185,7 +230,15 @@ static int scsi_multipath_sdev_init(struct scsi_device *sdev)
 	return 0;
 }
 
+static enum mpath_iopolicy_e scsi_mpath_get_iopolicy(struct mpath_head *mpath_head)
+{
+	struct scsi_mpath_head *scsi_mpath_head = mpath_head->drvdata;
+
+	return mpath_read_iopolicy(&scsi_mpath_head->iopolicy);
+}
+
 struct mpath_head_template smpdt = {
+	.get_iopolicy = scsi_mpath_get_iopolicy,
 };
 
 static struct scsi_mpath_head *scsi_mpath_alloc_head(void)
@@ -204,6 +257,7 @@ static struct scsi_mpath_head *scsi_mpath_alloc_head(void)
 		goto out_free;
 	scsi_mpath_head->mpath_head->mpdt = &smpdt;
 	scsi_mpath_head->mpath_head->drvdata = scsi_mpath_head;
+	scsi_mpath_head->iopolicy.iopolicy = iopolicy;
 
 	scsi_mpath_head->index = ida_alloc(&scsi_multipath_dev_ida, GFP_KERNEL);
 	if (scsi_mpath_head->index < 0)
diff --git a/include/scsi/scsi_multipath.h b/include/scsi/scsi_multipath.h
index 9e92d949392d4..de6339989d2a2 100644
--- a/include/scsi/scsi_multipath.h
+++ b/include/scsi/scsi_multipath.h
@@ -24,6 +24,7 @@ struct scsi_mpath_head {
 	struct list_head	entry;
 	struct ida		ida;
 	struct kref		ref;
+	struct mpath_iopolicy	iopolicy;
 	struct mpath_head	*mpath_head;
 	struct device		dev;
 	int			index;
-- 
2.43.5