[CRIU] Restore Failure

[Saied Kazemi]

Hi Pavel,

Thanks for looking into this.  I was out on Friday but Ying confirmed that
the patch works.

Cheers!

--Saied



On Fri, Aug 8, 2014 at 4:51 AM, Pavel Emelyanov <xemul at parallels.com> wrote:

> On 07/19/2014 09:16 AM, Saied Kazemi wrote:
> > Hi Pavel,
> >
> > I have run into a problem when restoring a process that was running in a
> Docker container when Docker home is bind mounted from a different device.
> >
> > As you know, it is possible to successfully dump and restore Docker
> container processes.  But when /var/lib/docker is bind mounted from a
> different device (e.g., mount /dev/sd3a /mnt/sd3a; mkdir /mnt/sda3/docker;
> mount --bind /mnt/sda3/docker /var/lib/docker), dump succeeds but restore
> fails.
> >
> > For easier testing and debugging, I have reproduced the problem with a
> couple of small shell scripts that I have attached here. These are the same
> shell scripts that I used during external bind mount troubleshooting.  I
> just changed them a bit to illustrate the problem I am currently running
> into.  If you run ./z1.sh without the bindmount argument, everything works
> fine.  But if you specify bindmount, it bind mounts its root from a
> different device (a tmpfs in this case), dump succeeds but restore fails.
>  I hope it's not an error on my part.
> >
> > I have been using the latest greatest criu binary from the head.  Please
> let me know once you've had a chance to try this.
>
> It looks like criu constantly postpones external bind mounts. I'm trying
> to resolve
> when we manage to break this (when I did ext-mount-map they for some
> reason didn't).
> Meanwhile, this patch fixes it back:
>
> diff --git a/mount.c b/mount.c
> index e0e88ea..60e14d1 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -1380,9 +1380,9 @@ static bool can_mount_now(struct mount_info *mi)
>         /*
>          * Other mounts can be mounted only if they have
>          * the master mount (see propagate_mount) or if we
> -        * expect a plugin to help us.
> +        * expect a plugin/ext-mount-map to help us.
>          */
> -       if (mi->bind || mi->need_plugin)
> +       if (mi->bind || mi->need_plugin || mi->external)
>                 return true;
>
>         return false;
> @@ -1415,7 +1415,7 @@ static int do_mount_one(struct mount_info *mi)
>
>         if (!mi->parent)
>                 ret = do_mount_root(mi);
> -       else if (!mi->bind && !mi->need_plugin)
> +       else if (!mi->bind && !mi->need_plugin && !mi->external)
>                 ret = do_new_mount(mi);
>         else
>                 ret = do_bind_mount(mi);
>
> Can you confirm that it fixes your problem?
>
> Thanks,
> Pavel
>
>
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