[CRIU] Sync TODO-s for mount.c work

[Oleg Nesterov]

Just in case,

	# cat /proc/`pidof mysqld`/mountinfo
	36 34 253:1 / / rw,relatime shared:7 master:1 - xfs /dev/mapper/rhel_ibm--x3650m4--02--vm--02-root rw,seclabel,attr2,inode64,noquota
	39 36 0:5 / /dev rw,nosuid shared:10 master:2 - devtmpfs devtmpfs rw,seclabel,size=16374292k,nr_inodes=4093573,mode=755
	40 39 0:17 / /dev/shm rw,nosuid,nodev shared:11 master:3 - tmpfs tmpfs rw,seclabel
	41 39 0:11 / /dev/pts rw,nosuid,noexec,relatime shared:12 master:4 - devpts devpts rw,seclabel,gid=5,mode=620,ptmxmode=000
	42 36 0:3 / /proc rw,nosuid,nodev,noexec,relatime shared:13 master:5 - proc proc rw
	43 36 0:16 / /sys rw,nosuid,nodev,noexec,relatime shared:14 master:6 - sysfs sysfs rw,seclabel
	44 43 0:19 / /sys/fs/cgroup rw,nosuid,nodev,noexec shared:15 master:8 - tmpfs tmpfs rw,seclabel,mode=755
	45 44 0:20 / /sys/fs/cgroup/systemd rw,nosuid,nodev,noexec,relatime shared:16 master:9 - cgroup cgroup rw,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd
	46 36 0:18 / /run rw,nosuid,nodev shared:17 master:22 - tmpfs tmpfs rw,seclabel,mode=755
	47 36 253:1 /tmp/systemd-private-FgmebS/tmp /tmp rw,relatime shared:18 master:1 - xfs /dev/mapper/rhel_ibm--x3650m4--02--vm--02-root rw,seclabel,attr2,inode64,noquota
	48 36 253:1 /var/tmp/systemd-private-AKz2QT/tmp /var/tmp rw,relatime shared:19 master:1 - xfs /dev/mapper/rhel_ibm--x3650m4--02--vm--02-root rw,seclabel,attr2,inode64,noquota

although I think you don't need this.

On 04/22, Oleg Nesterov wrote:
> Hi Tycho,
>
> On 04/21, Tycho Andersen wrote:
> >
> > On Tue, Apr 21, 2015 at 05:17:33PM +0200, Oleg Nesterov wrote:
> > >
> > > yes, otherwise (to me) "--ext-mount-map auto" simply doesn't work. See
> > > the initial report:
> > >
> > > 	http://lists.openvz.org/pipermail/criu/2015-April/019859.html
> >
> > What about something like the attached? Of course, this will break my
> > test and make things in general much harder to test, but I think it is
> > ok.
>
> Well. I can't really comment it. At least right now. probably never...
>
> But,
>
> > To avoid this, we simply don't allow --ext-mount-map auto on non-pivot_rooted
> > tasks,
>
> OK. Lets forget about "--ext-mount-map auto" for the moment. Let me repeat
> the quiestion I have already asked.
>
> If I start mysqld under systemd it runs with unshared mnt ns and
>
> 	# grep systemd-private /proc/`pidof mysqld`/mountinfo
>
> shows:
>
> 	47 36 253:1 /tmp/systemd-private-FgmebS/tmp /tmp rw,relatime shared:18 master:1 - xfs /dev/mapper/rhel_ibm--x3650m4--02--vm--02-root rw,seclabel,attr2,inode64,noquota
> 	48 36 253:1 /var/tmp/systemd-private-AKz2QT/tmp /var/tmp rw,relatime shared:19 master:1 - xfs /dev/mapper/rhel_ibm--x3650m4--02--vm--02-root rw,seclabel,attr2,inode64,noquota
>
> Now,
>
> 	# criu dump -D D/ -j -t `pidof mysqld`
> 	Error (mount.c:912): Mount 48 ./var/tmp (master_id: 1 shared_id: 19) has unreachable sharing. Try --enable-external-masters.
> 	Error (cr-dump.c:1943): Dumping FAILED.
>
> OK, lets try "--enable-external-masters" as the error message suggests ;)
>
> 	# criu dump -D D/ -j -t `pidof mysqld` --enable-external-masters
> 	must specify --ext-mount-map auto with --enable-external-{sharing|masters}
>
> So. criu asks for "--ext-mount-map auto" but it will fail with this change?
>
> How can I dump mysqld then?
>
> Oleg.