Re: [PATCH] fs: fix possible inconsistent mount device

[Yu Kuai <yukuai1@huaweicloud.com>]

Hi, Christoph!

在 2022/08/13 15:15, Christoph Hellwig 写道:
> On Sat, Aug 13, 2022 at 03:09:58PM +0800, Yu Kuai wrote:
>> Thanks for your reply. Do you think it's better to remove the rename
>> support from dm? Or it's better to add such limit?
> 
> It will probably be hard to entirely remove it.  But documentation
> and a rate limited warning discouraging it seems like a good idea.
> .
> 

I just found that not just rename, mount concurrent with device
remove/create can trigger this problem as well:

t1:                       t2
// create dm-0 with name test1
// mount /dev/mapper/test1
mount_bdev
  blkdev_get_by_path
   lookup_bdev
                           // remove dm-0
                           // create dm-0 with different name test2
   blkdev_get_by_dev
   // succeed

Do you think it's ok to add such checking to prevent this problem?

Thanks,
Kuai