md: switch md-cluster to use md_submodle_head

To make code cleaner, and prepare to add kconfig for bitmap.

Also remove the unsed global variables pers_lock, md_cluster_ops and
md_cluster_mod, and exported symbols register_md_cluster_operations(),
unregister_md_cluster_operations() and md_cluster_ops.

Link: https://lore.kernel.org/linux-raid/20250215092225.2427977-8-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Su Yue <glass.su@suse.com>

drivers/md/md-cluster.c

@@ -1612,7 +1612,14 @@ static int gather_bitmaps(struct md_rdev *rdev)
 	return err;
 }
 
-static const struct md_cluster_operations cluster_ops = {
+static struct md_cluster_operations cluster_ops = {
+	.head = {
+		.type	= MD_CLUSTER,
+		.id	= ID_CLUSTER,
+		.name	= "cluster",
+		.owner	= THIS_MODULE,
+	},
+
 	.join   = join,
 	.leave  = leave,
 	.slot_number = slot_number,
@@ -1642,13 +1649,12 @@ static int __init cluster_init(void)
 {
 	pr_warn("md-cluster: support raid1 and raid10 (limited support)\n");
 	pr_info("Registering Cluster MD functions\n");
-	register_md_cluster_operations(&cluster_ops, THIS_MODULE);
-	return 0;
+	return register_md_submodule(&cluster_ops.head);
 }
 
 static void cluster_exit(void)
 {
-	unregister_md_cluster_operations();
+	unregister_md_submodule(&cluster_ops.head);
 }
 
 module_init(cluster_init);

drivers/md/md-cluster.h

@@ -37,9 +37,6 @@ struct md_cluster_operations {
 	void (*update_size)(struct mddev *mddev, sector_t old_dev_sectors);
 };
 
-extern int register_md_cluster_operations(const struct md_cluster_operations *ops,
-		struct module *module);
-extern int unregister_md_cluster_operations(void);
 extern int md_setup_cluster(struct mddev *mddev, int nodes);
 extern void md_cluster_stop(struct mddev *mddev);
 extern void md_reload_sb(struct mddev *mddev, int raid_disk);

drivers/md/md.c

@@ -81,13 +81,8 @@ static const char *action_name[NR_SYNC_ACTIONS] = {
 
 static DEFINE_XARRAY(md_submodule);
 
-static DEFINE_SPINLOCK(pers_lock);
-
 static const struct kobj_type md_ktype;
 
-static const struct md_cluster_operations *md_cluster_ops;
-static struct module *md_cluster_mod;
-
 static DECLARE_WAIT_QUEUE_HEAD(resync_wait);
 static struct workqueue_struct *md_wq;
 
@@ -7452,11 +7447,12 @@ static int update_raid_disks(struct mddev *mddev, int raid_disks)
 
 static int get_cluster_ops(struct mddev *mddev)
 {
-	spin_lock(&pers_lock);
-	mddev->cluster_ops = md_cluster_ops;
-	if (mddev->cluster_ops && !try_module_get(md_cluster_mod))
+	xa_lock(&md_submodule);
+	mddev->cluster_ops = xa_load(&md_submodule, ID_CLUSTER);
+	if (mddev->cluster_ops &&
+	    !try_module_get(mddev->cluster_ops->head.owner))
 		mddev->cluster_ops = NULL;
-	spin_unlock(&pers_lock);
+	xa_unlock(&md_submodule);
 
 	return mddev->cluster_ops == NULL ? -ENOENT : 0;
 }
@@ -7467,7 +7463,7 @@ static void put_cluster_ops(struct mddev *mddev)
 		return;
 
 	mddev->cluster_ops->leave(mddev);
-	module_put(md_cluster_mod);
+	module_put(mddev->cluster_ops->head.owner);
 	mddev->cluster_ops = NULL;
 }
 
@@ -8559,31 +8555,6 @@ void unregister_md_submodule(struct md_submodule_head *msh)
 }
 EXPORT_SYMBOL_GPL(unregister_md_submodule);
 
-int register_md_cluster_operations(const struct md_cluster_operations *ops,
-				   struct module *module)
-{
-	int ret = 0;
-	spin_lock(&pers_lock);
-	if (md_cluster_ops != NULL)
-		ret = -EALREADY;
-	else {
-		md_cluster_ops = ops;
-		md_cluster_mod = module;
-	}
-	spin_unlock(&pers_lock);
-	return ret;
-}
-EXPORT_SYMBOL(register_md_cluster_operations);
-
-int unregister_md_cluster_operations(void)
-{
-	spin_lock(&pers_lock);
-	md_cluster_ops = NULL;
-	spin_unlock(&pers_lock);
-	return 0;
-}
-EXPORT_SYMBOL(unregister_md_cluster_operations);
-
 int md_setup_cluster(struct mddev *mddev, int nodes)
 {
 	int ret = get_cluster_ops(mddev);

drivers/md/md.h

@@ -603,7 +603,7 @@ struct mddev {
 	mempool_t *serial_info_pool;
 	void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);
 	struct md_cluster_info		*cluster_info;
-	const struct md_cluster_operations *cluster_ops;
+	struct md_cluster_operations *cluster_ops;
 	unsigned int			good_device_nr;	/* good device num within cluster raid */
 	unsigned int			noio_flag; /* for memalloc scope API */