From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: [PATCH 1/2] autofs4: allow autofs to work outside the initial PID namespace Date: Sat, 24 Nov 2012 14:35:17 -0800 Message-ID: <87lidqfx3u.fsf@xmission.com> References: <87obipehbt.fsf@tucsk.pomaz.szeredi.hu> <1353642304.2309.25.camel@perseus.themaw.net> <1353672540.6699.18.camel@perseus.themaw.net> <874nkgwfw0.fsf@tucsk.pomaz.szeredi.hu> <1353723813.2348.48.camel@perseus.themaw.net> <1353724641.2348.56.camel@perseus.themaw.net> <878v9rmcgc.fsf@xmission.com> Mime-Version: 1.0 Return-path: In-Reply-To: (Miklos Szeredi's message of "Sat, 24 Nov 2012 22:12:58 +0100") Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Miklos Szeredi Cc: Ian Kent , autofs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, sukadev@linux.vnet.ibm.com, serge.hallyn@canonical.com Miklos Szeredi writes: > On Sat, Nov 24, 2012 at 1:07 PM, Eric W. Biederman > wrote: >> Ian Kent writes: >> >>> On Sat, 2012-11-24 at 10:23 +0800, Ian Kent wrote: >>>> On Fri, 2012-11-23 at 15:30 +0100, Miklos Szeredi wrote: > >>>> AFAICS autofs mounts mounted with MS_PRIVATE in the initial namespace do >>>> propagate to the clone when it's created so I'm assuming subsequent >>>> mounts would also. If these mounts are busy in some way they can't be >>>> umounted in the clone unless "/" is marked private before attempting the >>>> umount. Subsequent mounts after the clone do not have a mechanism to propogate with MS_PRIVATE. As creating a new mount namespaces is essentially an instance of mount --bind. Those semantics are a little unintuitive I have to admit. >>> This may sound stupid but if there something like, say, MS_NOPROPAGATE >>> then the problem I see would pretty much just go away. No more need to >>> umount existing mounts and container instances would be isolated. But, I >>> guess, I'm not considering the possibility of cloned of processes as >>> well .... if that makes sense, ;) >> >> Something is very weird is going on. MS_PRIVATE should be the >> MS_NOPROPOGATE you are looking for. There is also MS_UNBINDABLE. >> which is a stronger form of MS_PRIVATE and probably worth play with. >> > > MS_UNBINDABLE says: skip this mount when copying a mount tree, such > as when the mount namespace is cloned. > > If you set MS_UNBINDABLE on autofs mounts then they will simply not > appear in a cloned namespace. Which sounds like a good idea, no? Good point. If the desire is for a mount to be managed by autofs setting MS_UNBINDABLE seems required. Eric