From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752831AbcEJPs3 (ORCPT ); Tue, 10 May 2016 11:48:29 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:58434 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751147AbcEJPs2 (ORCPT ); Tue, 10 May 2016 11:48:28 -0400 Date: Tue, 10 May 2016 16:48:26 +0100 From: Al Viro To: Phillip Susi Cc: linux-kernel Subject: Re: mount --move and shared namespaces Message-ID: <20160510154826.GL2694@ZenIV.linux.org.uk> References: <5731132A.7040801@ubuntu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5731132A.7040801@ubuntu.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 09, 2016 at 06:46:02PM -0400, Phillip Susi wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA512 > > It seems that mount --move does not work on a shared namespace ( now > the default under systemd ), yet you can mount --bind and then umount > the original, which seems to amount to exactly the same thing. Why is > the direct move not allowed? You have something mounted on /foo and events from /foo propagated to /bar. You move the instance on /foo to /baz; what to do with one on /bar? Propagation from /baz might have nothing whatsoever in common with that on /foo, so "move to the corresponding recepients of events for /baz" is not an answer... Move *into* shared is allowed - the one you move ends up relocated and cloned, with clones attached to the places where events propagate to. Move *from* shared... No sane semantics. And no, mount --move is *not* mount --bind + umount - it really moves the vfsmount, so anything sitting in that subtree will find itself at the new location.