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From: ebiederm@xmission.com (Eric W. Biederman)
To: Andy Lutomirski <luto@amacapital.net>
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Date: Fri, 10 Aug 2018 10:17:37 -0500
In-Reply-To: <0F2FA70F-8C7E-4D7D-B685-244A76BDB459@amacapital.net> (Andy
        Lutomirski's message of "Fri, 10 Aug 2018 07:36:17 -0700")
Message-ID: <8736vmp7xq.fsf@xmission.com>
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Subject: Re: BUG: Mount ignores mount options
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

Andy Lutomirski <luto@amacapital.net> writes:

>> On Aug 10, 2018, at 7:05 AM, Eric W. Biederman <ebiederm@xmission.com> wrote:
>> 
>> 
>> There is a serious problem with mount options today that fsopen does not
>> address.  The problem is that mount options are ignored for block based
>> filesystems, and any other type of filesystem that follows the same
>> pattern.
>> 
>
>> /dev/loop0 /root/loop0-noacl-noquota-nouser_xattr ext4 rw,relatime,nouser_xattr,noacl 0 0
>> /dev/loop0 /root/loop0-acl-quota-user_xattr ext4 rw,relatime,nouser_xattr,noacl 0 0
>
> To make sure I understand correctly: the problem is that the second
> mount ignored the options because the device was already mounted,
> right?

Yes.

> For the new API, I think the only remotely sane approach is to refuse
> to mount or init or whatever you call it an already mounted bdev. If
> user code genuinely needs to bind-mount an existing mount that is
> known only by its bdev, we can add a specific API just for that.

Eric