linux-kernel - Re: [RFC][PATCH 4/3] vfs: Allow rmdir to remove mounts in all but the current mount namespace

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Date:	Tue, 8 Oct 2013 09:06:29 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rob Landley <rob@...dley.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC][PATCH 4/3] vfs: Allow rmdir to remove mounts in all but the
 current mount namespace

On Tue, Oct 8, 2013 at 9:06 AM, Miklos Szeredi <miklos@...redi.hu> wrote:
> On Mon, Oct 07, 2013 at 03:25:17PM -0700, Eric W. Biederman wrote:
>> Andy Lutomirski <luto@...capital.net> writes:
>>
>> > On Mon, Oct 7, 2013 at 7:55 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>> >> "Serge E. Hallyn" <serge@...lyn.com> writes:
>> >>
>> >>> Quoting Eric W. Biederman (ebiederm@...ssion.com):
>> >>>>
>> >>>> Programs have been known to test for empty directories by attempting
>> >>>> to remove them.  To keep from violating the principle of least
>> >>>> surprise don't let directories the caller can see with someting
>> >>>> mounted on them be deleted.
>> >>>
>> >>> Do you think we should do the same thing for over-mounted file at
>> >>> vfs_unlink()?
>> >>
>> >> We easily could.
>
> And for vfs_rename()?
>
> I think the risks of changing behavior outweigh the benefits.  How many times
> did you have to remove or rename a mounted file or directory?  It's very rarely
> needed.

I do this every time I reinstall a system while running that system.
Admittedly, mount --move works, but that's a really unpleasant
interface.

When rename2 gets added, there could be a flag RENAME_MOVE_MOUNT to opt in.

--Andy

>
> Thanks,
> Miklos



-- 
Andy Lutomirski
AMA Capital Management, LLC
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