linux-kernel - Re: [PATCH] fs: fix possible inconsistent mount device

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Message-ID: <79effa0e-7ffe-4275-cf36-01fd3d0615b9@huaweicloud.com>
Date:   Fri, 2 Sep 2022 14:09:58 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Yu Kuai <yukuai1@...weicloud.com>
Cc:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] fs: fix possible inconsistent mount device

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