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

[Christoph Hellwig]

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 <h...@lst.de>
Acked-by: Song Liu <s...@kernel.org>
---
 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