From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Vagin Subject: Re: [PATCH] [RFC] mnt: add ability to clone mntns starting with the current root Date: Wed, 8 Oct 2014 15:08:30 +0400 Message-ID: <20141008110829.GC24908@paralelels.com> References: <1412683977-29543-1-git-send-email-avagin@openvz.org> <87mw97wqvx.fsf@x220.int.ebiederm.org> Mime-Version: 1.0 Content-Type: text/plain; charset="koi8-r" Return-path: Content-Disposition: inline In-Reply-To: <87mw97wqvx.fsf-JOvCrm2gF+uungPnsOpG7nhyD016LWXt@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Eric W. Biederman" Cc: Andrey Vagin , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrey Vagin , Alexander Viro , Andrew Morton , Cyrill Gorcunov , Pavel Emelyanov , Serge Hallyn , Rob Landley List-Id: linux-api@vger.kernel.org On Tue, Oct 07, 2014 at 01:45:22PM -0700, Eric W. Biederman wrote: > Andrey Vagin writes: > > > From: Andrey Vagin > > > > Currently when we create a new container with a separate root, > > we need to clone the current mount namespace with all mounts and then > > clean up it by using pivot_root(). A big part of mountpoints are cloned > > only to be umounted. > > Is the motivation performance? Because if that is the motivation we > need numbers. The major motivation to create a clean mount namespace which contains only required mounts. Now you want to convince us that there is nothing wrong if we use userns, because all inherited mounts are locked. My point is that all useless mounts should be umounted. If the current root isn't on rootfs, pivot_root() allows us to umount all useless points. But pivot_root() doesn't work, if the current root is on rootfs. How can we umount useless points in this case? Maybe we want to say that rootfs should not be used if we are going to create containers... Thanks, Andrew