[RFC-PATCH 2/2] nvme: use the namespace id for block device names

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

We can now assume the ns_id provides a unique number within a subsystem
when creating a namespace kobject. Use that rather than pulling an
available bit from an ida, which becomes unnecessary once we use the
controller's reported identifier.

The user observable change is that the suffix of the nvme namespace
device handle name will always be consistent regardless of which
controller is scanned first or what the namespace attachment state is
for a given controller being scanned. The prefix will still be dependent
on the order the controllers were connected/probed.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 drivers/nvme/host/core.c      | 19 +++++--------------
 drivers/nvme/host/multipath.c |  4 ++--
 drivers/nvme/host/nvme.h      |  2 --
 3 files changed, 7 insertions(+), 18 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 7a558d5103a21..3f2f9b2be87c2 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -667,7 +667,6 @@ static void nvme_free_ns_head(struct kref *ref)
 		container_of(ref, struct nvme_ns_head, ref);
 
 	nvme_mpath_put_disk(head);
-	ida_free(&head->subsys->ns_ida, head->instance);
 	cleanup_srcu_struct(&head->srcu);
 	nvme_put_subsystem(head->subsys);
 	kfree(head->plids);
@@ -3113,7 +3112,6 @@ static void nvme_destroy_subsystem(struct kref *ref)
 	list_del(&subsys->entry);
 	mutex_unlock(&nvme_subsystems_lock);
 
-	ida_destroy(&subsys->ns_ida);
 	device_del(&subsys->dev);
 	put_device(&subsys->dev);
 }
@@ -3257,7 +3255,6 @@ static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 			put_device(&subsys->dev);
 			goto out_unlock;
 		}
-		ida_init(&subsys->ns_ida);
 		list_add_tail(&subsys->entry, &nvme_subsystems);
 	}
 
@@ -3868,7 +3865,7 @@ static int nvme_add_ns_cdev(struct nvme_ns *ns)
 
 	ns->cdev_device.parent = ns->ctrl->device;
 	ret = dev_set_name(&ns->cdev_device, "ng%dn%d",
-			   ns->ctrl->instance, ns->head->instance);
+			   ns->ctrl->instance, ns->head->ns_id);
 	if (ret)
 		return ret;
 
@@ -3890,14 +3887,10 @@ static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,
 	head = kzalloc(size, GFP_KERNEL);
 	if (!head)
 		goto out;
-	ret = ida_alloc_min(&ctrl->subsys->ns_ida, 1, GFP_KERNEL);
-	if (ret < 0)
-		goto out_free_head;
-	head->instance = ret;
 	INIT_LIST_HEAD(&head->list);
 	ret = init_srcu_struct(&head->srcu);
 	if (ret)
-		goto out_ida_remove;
+		goto out_free_head;
 	head->subsys = ctrl->subsys;
 	head->ns_id = info->nsid;
 	head->ids = info->ids;
@@ -3925,8 +3918,6 @@ static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,
 	return head;
 out_cleanup_srcu:
 	cleanup_srcu_struct(&head->srcu);
-out_ida_remove:
-	ida_free(&ctrl->subsys->ns_ida, head->instance);
 out_free_head:
 	kfree(head);
 out:
@@ -4162,14 +4153,14 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info)
 	 */
 	if (nvme_ns_head_multipath(ns->head)) {
 		sprintf(disk->disk_name, "nvme%dc%dn%d", ctrl->subsys->instance,
-			ctrl->instance, ns->head->instance);
+			ctrl->instance, ns->head->ns_id);
 		disk->flags |= GENHD_FL_HIDDEN;
 	} else if (multipath) {
 		sprintf(disk->disk_name, "nvme%dn%d", ctrl->subsys->instance,
-			ns->head->instance);
+			ns->head->ns_id);
 	} else {
 		sprintf(disk->disk_name, "nvme%dn%d", ctrl->instance,
-			ns->head->instance);
+			ns->head->ns_id);
 	}
 
 	if (nvme_update_ns_info(ns, info))
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 02a50181d1dd6..8715b04ff92a8 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -640,7 +640,7 @@ static int nvme_add_ns_head_cdev(struct nvme_ns_head *head)
 
 	head->cdev_device.parent = &head->subsys->dev;
 	ret = dev_set_name(&head->cdev_device, "ng%dn%d",
-			   head->subsys->instance, head->instance);
+			   head->subsys->instance, head->ns_id);
 	if (ret)
 		return ret;
 	ret = nvme_cdev_add(&head->cdev, &head->cdev_device,
@@ -767,7 +767,7 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
 	 */
 	set_bit(GD_SUPPRESS_PART_SCAN, &head->disk->state);
 	sprintf(head->disk->disk_name, "nvme%dn%d",
-			ctrl->subsys->instance, head->instance);
+			ctrl->subsys->instance, head->ns_id);
 	nvme_tryget_ns_head(head);
 	return 0;
 }
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index ed8ce356c363e..142a5684205a8 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -499,7 +499,6 @@ struct nvme_subsystem {
 	u8			cmic;
 	enum nvme_subsys_type	subtype;
 	u16			vendor_id;
-	struct ida		ns_ida;
 #ifdef CONFIG_NVME_MULTIPATH
 	enum nvme_iopolicy	iopolicy;
 #endif
@@ -540,7 +539,6 @@ struct nvme_ns_head {
 	struct nvme_effects_log *effects;
 	u64			nuse;
 	unsigned		ns_id;
-	int			instance;
 #ifdef CONFIG_BLK_DEV_ZONED
 	u64			zsze;
 #endif
-- 
2.47.3