md: introduce struct md_submodule_head and APIs

Prepare to unify registration and unregistration of md personalities
and md-cluster, also prepare for add kconfig for md-bitmap.

Link: https://lore.kernel.org/linux-raid/[email protected]
Signed-off-by: Yu Kuai <[email protected]>

Author: YuKuai-huawei

drivers/md/md-cluster.h

@@ -10,6 +10,8 @@ struct mddev;
 struct md_rdev;
 
 struct md_cluster_operations {
+	struct md_submodule_head head;
+
 	int (*join)(struct mddev *mddev, int nodes);
 	int (*leave)(struct mddev *mddev);
 	int (*slot_number)(struct mddev *mddev);

drivers/md/md.c

@@ -79,6 +79,8 @@ static const char *action_name[NR_SYNC_ACTIONS] = {
 	[ACTION_IDLE]		= "idle",
 };
 
+static DEFINE_XARRAY(md_submodule);
+
 /* pers_list is a list of registered personalities protected by pers_lock. */
 static LIST_HEAD(pers_list);
 static DEFINE_SPINLOCK(pers_lock);
@@ -8522,6 +8524,18 @@ static const struct proc_ops mdstat_proc_ops = {
 	.proc_poll	= mdstat_poll,
 };
 
+int register_md_submodule(struct md_submodule_head *msh)
+{
+	return xa_insert(&md_submodule, msh->id, msh, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(register_md_submodule);
+
+void unregister_md_submodule(struct md_submodule_head *msh)
+{
+	xa_erase(&md_submodule, msh->id);
+}
+EXPORT_SYMBOL_GPL(unregister_md_submodule);
+
 int register_md_personality(struct md_personality *p)
 {
 	pr_debug("md: %s personality registered for level %d\n",

drivers/md/md.h

@@ -18,10 +18,37 @@
 #include <linux/timer.h>
 #include <linux/wait.h>
 #include <linux/workqueue.h>
+#include <linux/raid/md_u.h>
 #include <trace/events/block.h>
 
 #define MaxSector (~(sector_t)0)
 
+enum md_submodule_type {
+	MD_PERSONALITY = 0,
+	MD_CLUSTER,
+	MD_BITMAP, /* TODO */
+};
+
+enum md_submodule_id {
+	ID_LINEAR	= LEVEL_LINEAR,
+	ID_RAID0	= 0,
+	ID_RAID1	= 1,
+	ID_RAID4	= 4,
+	ID_RAID5	= 5,
+	ID_RAID6	= 6,
+	ID_RAID10	= 10,
+	ID_CLUSTER,
+	ID_BITMAP,	/* TODO */
+	ID_LLBITMAP,	/* TODO */
+};
+
+struct md_submodule_head {
+	enum md_submodule_type	type;
+	enum md_submodule_id	id;
+	const char		*name;
+	struct module		*owner;
+};
+
 /*
  * These flags should really be called "NO_RETRY" rather than
  * "FAILFAST" because they don't make any promise about time lapse,
@@ -698,6 +725,7 @@ static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
 
 struct md_personality
 {
+	struct md_submodule_head head;
 	char *name;
 	int level;
 	struct list_head list;
@@ -842,6 +870,9 @@ static inline void safe_put_page(struct page *p)
 	if (p) put_page(p);
 }
 
+int register_md_submodule(struct md_submodule_head *msh);
+void unregister_md_submodule(struct md_submodule_head *msh);
+
 extern int register_md_personality(struct md_personality *p);
 extern int unregister_md_personality(struct md_personality *p);
 extern struct md_thread *md_register_thread(