On Thu, Jul 15, 2021 at 01:07:13PM +0300, Pavel Tikhomirov wrote: > Previously a sharing group (shared and master ids pair) can be only > inherited when mount is created via bindmount. This patch adds an > ability to add an existing private mount into an existing sharing group. > > With this functionality one can first create the desired mount tree from > only private mounts (without the need to care about undesired mount > propagation or mount creation order implied by sharing group > dependencies), and next then setup any desired mount sharing between > those mounts in tree as needed. > > This allows CRIU to restore any set of mount namespaces, mount trees and > sharing group trees for a container. > > We have many issues with restoring mounts in CRIU related to sharing > groups and propagation: > - reverse sharing groups vs mount tree order requires complex mounts > reordering which mostly implies also using some temporary mounts > (please see https://lkml.org/lkml/2021/3/23/569 for more info) > > - mount() syscall creates tons of mounts due to propagation > - mount re-parenting due to propagation > - "Mount Trap" due to propagation > - "Non Uniform" propagation, meaning that with different tricks with > mount order and temporary children-"lock" mounts one can create mount > trees which can't be restored without those tricks > (see https://www.linuxplumbersconf.org/event/7/contributions/640/) > > With this new functionality we can resolve all the problems with > propagation at once. > > Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Christian Brauner <christian.brauner@xxxxxxxxxx> > Cc: Mattias Nissler <mnissler@xxxxxxxxxxxx> > Cc: Aleksa Sarai <cyphar@xxxxxxxxxx> > Cc: Andrei Vagin <avagin@xxxxxxxxx> Looks good to me. Co-developed-by: Andrei Vagin <avagin@xxxxxxxxx> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx> > Cc: linux-fsdevel@xxxxxxxxxxxxxxx > Cc: linux-api@xxxxxxxxxxxxxxx > Cc: lkml <linux-kernel@xxxxxxxxxxxxxxx> > Signed-off-by: Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx> > Thanks, Andrei
