[PATCH 12/19] md: use __register_blkdev to allocate devices on demand

[Christoph Hellwig <hch@xxxxxx>]

Use the simpler mechanism attached to major_name to allocate a brd device
when a currently unregistered minor is accessed.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Song Liu <song@xxxxxxxxxx>
---
 drivers/md/md.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9562ef598ae1f4..be3625acf67d7e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5766,11 +5766,12 @@ static int md_alloc(dev_t dev, char *name)
 	return error;
 }
 
-static struct kobject *md_probe(dev_t dev, int *part, void *data)
+static void md_probe(dev_t dev)
 {
+	if (MAJOR(dev) == MD_MAJOR && MINOR(dev) >= 512)
+		return;
 	if (create_on_open)
 		md_alloc(dev, NULL);
-	return NULL;
 }
 
 static int add_named_array(const char *val, const struct kernel_param *kp)
@@ -6536,7 +6537,7 @@ static void autorun_devices(int part)
 			break;
 		}
 
-		md_probe(dev, NULL, NULL);
+		md_probe(dev);
 		mddev = mddev_find(dev);
 		if (!mddev || !mddev->gendisk) {
 			if (mddev)
@@ -9548,18 +9549,15 @@ static int __init md_init(void)
 	if (!md_misc_wq)
 		goto err_rdev_misc_wq;
 
-	if ((ret = register_blkdev(MD_MAJOR, "md")) < 0)
+	ret = __register_blkdev(MD_MAJOR, "md", md_probe);
+	if (ret < 0)
 		goto err_md;
 
-	if ((ret = register_blkdev(0, "mdp")) < 0)
+	ret = __register_blkdev(0, "mdp", md_probe);
+	if (ret < 0)
 		goto err_mdp;
 	mdp_major = ret;
 
-	blk_register_region(MKDEV(MD_MAJOR, 0), 512, THIS_MODULE,
-			    md_probe, NULL, NULL);
-	blk_register_region(MKDEV(mdp_major, 0), 1UL<<MINORBITS, THIS_MODULE,
-			    md_probe, NULL, NULL);
-
 	register_reboot_notifier(&md_notifier);
 	raid_table_header = register_sysctl_table(raid_root_table);
 
@@ -9826,9 +9824,6 @@ static __exit void md_exit(void)
 	struct list_head *tmp;
 	int delay = 1;
 
-	blk_unregister_region(MKDEV(MD_MAJOR,0), 512);
-	blk_unregister_region(MKDEV(mdp_major,0), 1U << MINORBITS);
-
 	unregister_blkdev(MD_MAJOR,"md");
 	unregister_blkdev(mdp_major, "mdp");
 	unregister_reboot_notifier(&md_notifier);
-- 
2.28.0