md: make 'name' arg to md_register_thread non-optional.

Having the 'name' arg optional and defaulting to the current
personality name is no necessary and leads to errors, as when
changing the level of an array we can end up using the
name of the old level instead of the new one.

So make it non-optional and always explicitly pass the name
of the level that the array will be.

Reported-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 973aa84..c601c4b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6751,7 +6751,7 @@
 	thread->tsk = kthread_run(md_thread, thread,
 				  "%s_%s",
 				  mdname(thread->mddev),
-				  name ?: mddev->pers->name);
+				  name);
 	if (IS_ERR(thread->tsk)) {
 		kfree(thread);
 		return NULL;
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 9339e67..61a1833 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -474,7 +474,8 @@
 	}
 
 	{
-		mddev->thread = md_register_thread(multipathd, mddev, NULL);
+		mddev->thread = md_register_thread(multipathd, mddev,
+						   "multipath");
 		if (!mddev->thread) {
 			printk(KERN_ERR "multipath: couldn't allocate thread"
 				" for %s\n", mdname(mddev));
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index a9c7981..39b2a8a 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2621,7 +2621,7 @@
 		goto abort;
 	}
 	err = -ENOMEM;
-	conf->thread = md_register_thread(raid1d, mddev, NULL);
+	conf->thread = md_register_thread(raid1d, mddev, "raid1");
 	if (!conf->thread) {
 		printk(KERN_ERR
 		       "md/raid1:%s: couldn't allocate thread\n",
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index ae73e29..edc1088 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3427,7 +3427,7 @@
 	spin_lock_init(&conf->resync_lock);
 	init_waitqueue_head(&conf->wait_barrier);
 
-	conf->thread = md_register_thread(raid10d, mddev, NULL);
+	conf->thread = md_register_thread(raid10d, mddev, "raid10");
 	if (!conf->thread)
 		goto out;
 
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 62b6b3a..a5135e5 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4840,6 +4840,7 @@
 	int raid_disk, memory, max_disks;
 	struct md_rdev *rdev;
 	struct disk_info *disk;
+	char pers_name[6];
 
 	if (mddev->new_level != 5
 	    && mddev->new_level != 4
@@ -4963,7 +4964,8 @@
 		printk(KERN_INFO "md/raid:%s: allocated %dkB\n",
 		       mdname(mddev), memory);
 
-	conf->thread = md_register_thread(raid5d, mddev, NULL);
+	sprintf(pers_name, "raid%d", mddev->new_level);
+	conf->thread = md_register_thread(raid5d, mddev, pers_name);
 	if (!conf->thread) {
 		printk(KERN_ERR
 		       "md/raid:%s: couldn't allocate thread.\n",