linux-kernel - Re: [PATCH 2.6.24-rc3] Fix /proc/net breakage

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Message-Id: <20071207022342.806ee4ee.akpm@linux-foundation.org>
Date:	Fri, 7 Dec 2007 02:23:42 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	Pavel Emelyanov <xemul@...nvz.org>,
	"Denis V. Lunev" <den@...nvz.org>
Subject: Re: [PATCH 2.6.24-rc3] Fix /proc/net breakage

On Fri, 07 Dec 2007 04:51:37 +0000 David Woodhouse <dwmw2@...radead.org> wrote:

> On Mon, 2007-11-26 at 15:17 -0700, Eric W. Biederman wrote:
> > Well I clearly goofed when I added the initial network namespace support
> > for /proc/net.  Currently things work but there are odd details visible
> > to user space, even when we have a single network namespace.
> > 
> > Since we do not cache proc_dir_entry dentries at the moment we can
> > just modify ->lookup to return a different directory inode depending
> > on the network namespace of the process looking at /proc/net, replacing
> > the current technique of using a magic and fragile follow_link method.
> > 
> > To accomplish that this patch:
> > - introduces a shadow_proc method to allow different dentries to
> >   be returned from proc_lookup.
> > - Removes the old /proc/net follow_link magic
> > - Fixes a weakness in our not caching of proc generic dentries.
> > 
> > As shadow_proc uses a task struct to decided which dentry to return we
> > can go back later and fix the proc generic caching without modifying any code that
> > uses the shadow_proc method.
> > 
> > Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> > ---
> >  fs/proc/generic.c       |   12 ++++++-
> >  fs/proc/proc_net.c      |   86 +++--------------------------------------------
> >  include/linux/proc_fs.h |    3 ++
> >  3 files changed, 19 insertions(+), 82 deletions(-)
> 
> (commit 2b1e300a9dfc3196ccddf6f1d74b91b7af55e416)
> 
> This seems to have broken the use of /proc/bus/usb as a mountpoint. It
> always appears empty now, whatever's supposed to be mounted there.
> 

Yes.  Denis and Eric are tossing around competing patches but afaik nobody
is happy with any of them.  Guys, could we get this sorted soonish please?
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