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

From: Serge E. Hallyn
Date: Fri May 18 2012 - 15:41:55 EST


Quoting Pavel Emelyanov (xemul@xxxxxxxxxxxxx):
> 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@xxxxxxxxxxxx>
>
> Acked-by: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>

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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