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

[Tycho Andersen]

Hi Ole,

On Wed, Apr 22, 2015 at 8:19 AM, Oleg Nesterov <oleg at redhat.com> 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?

In this case you have to use --ext-mount-map KEY:VAL as in the good
old days before --ext-mount-map auto. I guess we could take out the
hint about --enable-external-masters (or leave it there and put
something bigger in).

Tycho

>
> Oleg.
>