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From: David Howells <dhowells@redhat.com>
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To: Andy Lutomirski <luto@amacapital.net>
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Subject: Re: BUG: Mount ignores mount options
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Date: Fri, 10 Aug 2018 16:13:11 +0100
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Andy Lutomirski <luto@amacapital.net> wrote:

> > /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?
> 
> 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.

I'm adding some flags to fsopen() to allow userspace to say whether it wants
no sharing, same parameters-only sharing or anything-goes sharing (as now).

I'm also adding a flag whereby userspace can forbid anyone else from sharing a
new superblock it has just set up.

David