On Wed, Nov 09, 2022 at 10:08:14AM +0800, Yu Kuai wrote:
>> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
>> index 2917700b1e15c..7b0d6dc957549 100644
>> --- a/drivers/md/dm.c
>> +++ b/drivers/md/dm.c
>> @@ -751,9 +751,16 @@ static struct table_device *open_table_device(struct mapped_device *md,
>> goto out_free_td;
>> }
>> - r = bd_link_disk_holder(bdev, dm_disk(md));
>> - if (r)
>> - goto out_blkdev_put;
>> + /*
>> + * We can be called before the dm disk is added. In that case we can't
>> + * register the holder relation here. It will be done once add_disk was
>> + * called.
>> + */
>> + if (md->disk->slave_dir) {
> If device_add_disk() or del_gendisk() can concurrent with this, It seems
> to me that using 'slave_dir' is not safe.
>
> I'm not quite familiar with dm, can we guarantee that they can't
> concurrent?
I assumed dm would not get itself into territory were creating /
deleting the device could race with adding component devices, but
digging deeper I can't find anything. This could be done
by holding table_devices_lock around add_disk/del_gendisk, but
I'm not that familar with the dm code.
Mike, can you help out on this?
