linux-kernel - Re: [PATCH] vfs: Add setns support for the mount namespace

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Date:	Fri, 18 May 2012 19:44:17 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	Daniel Lezcano <dlezcano@...ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Miklos Szeredi <mszeredi@...e.cz>
Subject: Re: [PATCH] vfs: Add setns support for the mount namespace

Quoting Pavel Emelyanov (xemul@...allels.com):
> On 05/12/2012 12:54 AM, Eric W. Biederman wrote:
> > 
> > setns support for the mount namespace is a little tricky as an arbitrary
> > decision must be made about what to set fs->root and fs->pwd to, as
> > there is no expectation of a relationship between the two mount
> > namespaces.  Therefore I arbitrarily find the root mount point, and
> > follow every mount on top of it to find the top of the mount stack.
> > Then I set fs->root and fs->pwd to that location.  The topmost root of
> > the mount stack seems like a reasonable place to be.
> > 
> > Bind mount support for the mount namespace inodes has the possibility of
> > creating circular dependencies between mount namespaces.  Circular
> > dependencies can result in loops that prevent mount namespaces from
> > every being freed.  I avoid creating those circular dependencies by
> > adding a sequence number to the mount namespace and require all bind
> > mounts be of a younger mount namespace into an older mount namespace.
> > 
> > Add a helper function proc_ns_inode so it is possible to detect when we
> > are attempting to bind mound a namespace inode.
> > 
> > Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> 
> Acked-by: Pavel Emelyanov <xemul@...allels.com>

These patches haven't made it into linux-next or Linus' tree.  (More
worrisome, is that the several online linux-kernel mail archives I've
checked seem to have most of this thread, but not Eric's original
patch.)  What path were they expected to go in by?

thanks,
-serge
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