Merge: nvme: remove multipath module parameter

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/374

nvme: remove multipath module parameter

JIRA: https://issues.redhat.com/browse/RHEL-78133

Upstream Status: RHEL-only

Since device-mapper multipath will no longer be operating on NVMe
devices, there is no longer a need for the "multipath" parameter.

Note that, when compiled with CONFIG_NVME_MULTIPATH off multi-path
capable controllers and namespaces will continue to present multiple
device entries - one for each controller/namespace discovered.  This
could be confusing, as device-mapper multipath relies upon code in
nvme/host/multipath.c, and running device-mapper multipath with a
kernel compiled with CONFIG_NVME_MULTIPATH disabled is not supported.

Closes: https://lore.kernel.org/linux-nvme/20241121220321.40616-1-bgurney@redhat.com/

Tested-by: John Meneghini <jmeneghi@redhat.com>
Reviewed-by: John Meneghini <jmeneghi@redhat.com>

Signed-off-by: Bryan Gurney <bgurney@redhat.com>

Approved-by: John Meneghini <jmeneghi@redhat.com>
Approved-by: Ewan D. Milne <emilne@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Jan Stancek <jstancek@redhat.com>

Author: jstancek

drivers/nvme/host/core.c

@@ -3767,14 +3767,6 @@ 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");
-		}
 	}
 
 	list_add_tail_rcu(&ns->siblings, &head->list);
@@ -3873,12 +3865,14 @@ 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) {
+	} else {
+#ifdef CONFIG_NVME_MULTIPATH
 		sprintf(disk->disk_name, "nvme%dn%d", ctrl->subsys->instance,
 			ns->head->instance);
-	} else {
+#else
 		sprintf(disk->disk_name, "nvme%dn%d", ctrl->instance,
 			ns->head->instance);
+#endif
 	}
 
 	if (nvme_update_ns_info(ns, info))

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",
@@ -626,9 +621,11 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
 	 * We also do this for private namespaces as the namespace sharing flag
 	 * could change after a rescan.
 	 */
+#ifdef CONFIG_NVME_MULTIPATH
 	if (!(ctrl->subsys->cmic & NVME_CTRL_CMIC_MULTI_CTRL) ||
-	    !nvme_is_unique_nsid(ctrl, head) || !multipath)
+	    !nvme_is_unique_nsid(ctrl, head))
 		return 0;
+#endif
 
 	blk_set_stacking_limits(&lim);
 	lim.dma_alignment = 3;
@@ -1033,10 +1030,11 @@ int nvme_mpath_init_identify(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 	size_t ana_log_size;
 	int error = 0;
 
+#ifdef CONFIG_NVME_MULTIPATH
 	/* check if multipath is enabled and we have the capability */
-	if (!multipath || !ctrl->subsys ||
-	    !(ctrl->subsys->cmic & NVME_CTRL_CMIC_ANA))
+	if (!ctrl->subsys || !(ctrl->subsys->cmic & NVME_CTRL_CMIC_ANA))
 		return 0;
+#endif
 
 	/* initialize this in the identify path to cover controller resets */
 	atomic_set(&ctrl->nr_active, 0);

drivers/nvme/host/nvme.h

@@ -971,7 +971,6 @@ static inline void nvme_trace_bio_complete(struct request *req)
 		trace_block_bio_complete(ns->head->disk->queue, req->bio);
 }
 
-extern bool multipath;
 extern struct device_attribute dev_attr_ana_grpid;
 extern struct device_attribute dev_attr_ana_state;
 extern struct device_attribute subsys_attr_iopolicy;
@@ -981,7 +980,6 @@ 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;