[RFC PATCH 2/2] nvme-multipath: remove multipath module param

[Nilay Shroff]

Remove the multipath module parameter from nvme-core and make native
NVMe multipath support explicit. Since we now always create a multipath
head disk node, even for single-port NVMe disks, when CONFIG_NVME_
MULTIPATH is enabled, this module parameter is no longer needed to
toggle the behavior.

Users who prefer non-native multipath must disable CONFIG_NVME_MULTIPATH
at compile time.

Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
---
 drivers/nvme/host/core.c      | 18 +++++++-----------
 drivers/nvme/host/multipath.c | 17 ++---------------
 drivers/nvme/host/nvme.h      |  1 -
 3 files changed, 9 insertions(+), 27 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index e798809a8325..50c170425141 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3823,14 +3823,13 @@ static int nvme_init_ns_head(struct nvme_ns *ns, struct nvme_ns_info *info)
 					info->nsid);
 			goto out_put_ns_head;
 		}
-
-		if (!multipath) {
-			dev_warn(ctrl->device,
-				"Found shared namespace %d, but multipathing not supported.\n",
-				info->nsid);
-			dev_warn_once(ctrl->device,
-				"Support for shared namespaces without CONFIG_NVME_MULTIPATH is deprecated and will be removed in Linux 6.0.\n");
-		}
+#ifndef CONFIG_NVME_MULTIPATH
+		dev_warn(ctrl->device,
+			"Found shared namespace %d, but multipathing not supported.\n",
+			info->nsid);
+		dev_warn_once(ctrl->device,
+			"Support for shared namespaces without CONFIG_NVME_MULTIPATH is deprecated and will be removed in Linux 6.0.\n");
+#endif
 	}
 
 	list_add_tail_rcu(&ns->siblings, &head->list);
@@ -3929,9 +3928,6 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info)
 		sprintf(disk->disk_name, "nvme%dc%dn%d", ctrl->subsys->instance,
 			ctrl->instance, ns->head->instance);
 		disk->flags |= GENHD_FL_HIDDEN;
-	} else if (multipath) {
-		sprintf(disk->disk_name, "nvme%dn%d", ctrl->subsys->instance,
-			ns->head->instance);
 	} else {
 		sprintf(disk->disk_name, "nvme%dn%d", ctrl->instance,
 			ns->head->instance);
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 0f54889bd483..84211f64d178 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -9,11 +9,6 @@
 #include <trace/events/block.h>
 #include "nvme.h"
 
-bool multipath = true;
-module_param(multipath, bool, 0444);
-MODULE_PARM_DESC(multipath,
-	"turn on native support for multiple controllers per subsystem");
-
 static const char *nvme_iopolicy_names[] = {
 	[NVME_IOPOLICY_NUMA]	= "numa",
 	[NVME_IOPOLICY_RR]	= "round-robin",
@@ -671,14 +666,6 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
 	INIT_DELAYED_WORK(&head->remove_work, nvme_remove_head_work);
 	head->delayed_shutdown_sec = 0;
 
-	/*
-	 * A head disk node is always created for all types of NVMe disks
-	 * (single-ported and multi-ported), unless the multipath module
-	 * parameter is explicitly set to false.
-	 */
-	if (!multipath)
-		return 0;
-
 	blk_set_stacking_limits(&lim);
 	lim.dma_alignment = 3;
 	lim.features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT | BLK_FEAT_POLL;
@@ -1262,8 +1249,8 @@ int nvme_mpath_init_identify(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 	size_t ana_log_size;
 	int error = 0;
 
-	/* check if multipath is enabled and we have the capability */
-	if (!multipath || !ctrl->subsys ||
+	/* check if controller has ANA capability */
+	if (!ctrl->subsys ||
 	    !(ctrl->subsys->cmic & NVME_CTRL_CMIC_ANA))
 		return 0;
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 4375357b8cd7..fba686b91976 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -997,7 +997,6 @@ static inline bool nvme_disk_is_ns_head(struct gendisk *disk)
 	return disk->fops == &nvme_ns_head_ops;
 }
 #else
-#define multipath false
 static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
 {
 	return false;
-- 
2.47.1