[PATCH 09/18] brd: use __register_blkdev to allocate devices on demand

Christoph Hellwig
2020-10-29T15:31:16Z

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@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
drivers/block/brd.c | 39 +++++++++++----------------------------
1 file changed, 11 insertions(+), 28 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index cc49a921339f77..c43a6ab4b1f39f 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -426,14 +426,15 @@ static void brd_free(struct brd_device *brd)
kfree(brd);
}

-static struct brd_device *brd_init_one(int i, bool *new)
+static void brd_probe(dev_t dev)
{
struct brd_device *brd;
+ int i = MINOR(dev) / max_part;

- *new = false;
+ mutex_lock(&brd_devices_mutex);
list_for_each_entry(brd, &brd_devices, brd_list) {
if (brd->brd_number == i)
- goto out;
+ goto out_unlock;
}

brd = brd_alloc(i);
@@ -442,9 +443,9 @@ static struct brd_device *brd_init_one(int i, bool *new)
add_disk(brd->brd_disk);
list_add_tail(&brd->brd_list, &brd_devices);
}
- *new = true;
-out:
- return brd;
+
+out_unlock:
+ mutex_unlock(&brd_devices_mutex);
}

static void brd_del_one(struct brd_device *brd)
@@ -454,23 +455,6 @@ static void brd_del_one(struct brd_device *brd)
brd_free(brd);
}

-static struct kobject *brd_probe(dev_t dev, int *part, void *data)
-{
- struct brd_device *brd;
- struct kobject *kobj;
- bool new;
-
- mutex_lock(&brd_devices_mutex);
- brd = brd_init_one(MINOR(dev) / max_part, &new);
- kobj = brd ? get_disk_and_module(brd->brd_disk) : NULL;
- mutex_unlock(&brd_devices_mutex);
-
- if (new)
- *part = 0;
-
- return kobj;
-}
-
static inline void brd_check_and_reset_par(void)
{
if (unlikely(!max_part))
@@ -510,11 +494,12 @@ static int __init brd_init(void)
* dynamically.
*/

- if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
+ if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe))
return -EIO;

brd_check_and_reset_par();

+ mutex_lock(&brd_devices_mutex);
for (i = 0; i < rd_nr; i++) {
brd = brd_alloc(i);
if (!brd)
@@ -532,9 +517,7 @@ static int __init brd_init(void)
brd->brd_disk->queue = brd->brd_queue;
add_disk(brd->brd_disk);
}
-
- blk_register_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS,
- THIS_MODULE, brd_probe, NULL, NULL);
+ mutex_unlock(&brd_devices_mutex);

pr_info("brd: module loaded\n");
return 0;
@@ -544,6 +527,7 @@ static int __init brd_init(void)
list_del(&brd->brd_list);
brd_free(brd);
}
+ mutex_unlock(&brd_devices_mutex);
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");

pr_info("brd: module NOT loaded !!!\n");
@@ -557,7 +541,6 @@ static void __exit brd_exit(void)
list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
brd_del_one(brd);

- blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), 1UL << MINORBITS);
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");

pr_info("brd: module unloaded\n");
--
2.28.0