[CRIU] [PATCH] Fix restoring cgroup across hosts

[Hui Kang]

On Mon, Aug 10, 2015 at 12:42 PM, Tycho Andersen <
tycho.andersen at canonical.com> wrote:

> On Mon, Aug 10, 2015 at 12:30:47PM -0400, Hui Kang wrote:
> > On Mon, Aug 10, 2015 at 11:16 AM, Tycho Andersen <
> > tycho.andersen at canonical.com> wrote:
> >
> > > On Mon, Aug 10, 2015 at 03:00:42PM +0000, Hui Kang wrote:
> > > > The process to be restored may not have certain cgroup dir, e.g
> > > > cpu/[PID]/cpu.shares. Currently restoring  will fail in closing
> > > > the file. If this is the case, the fileno is -1 and we can ignore
> > > > this and let the restore proceed.
> > > >
> > > > Signed-off-by: Hui Kang <hkang.sunysb at gmail.com>
> > > > ---
> > > >  cgroup.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/cgroup.c b/cgroup.c
> > > > index a4e0146..f4e49b3 100644
> > > > --- a/cgroup.c
> > > > +++ b/cgroup.c
> > > > @@ -974,7 +974,7 @@ static int restore_cgroup_prop(const
> CgroupPropEntry
> > > * cg_prop_entry_p,
> > > >               return -1;
> > > >       }
> > > >
> > > > -     if (fclose(f) != 0) {
> > > > +     if ((fclose(f) != 0) && (fileno(f) >= 0)) {
> > >
> > > If we put these in the other order we can avoid the fclose all
> > > together, I think.
> > >
> > >
> > Thanks for your suggestions. However, the fileno only turns to -1 after
> > fclose(f). This is because file is closed.
> > Prior to that, fileno(f) returns 5, which looks normal for
> > cgroup/cpu/cpus.share.
>
> Ah, so doesn't this patch mask any error entirely then? As Pavel
> points out, if the file doesn't exist, shouldn't the fopenat() give
> you a bad fd?
>

When I move the criu images (only have cpusets.cpus set) to a different
host and restore suing cgroup-manage=full, cpu.shares exists in the
destination. fopenat and fprintf returns OK, only fclose failed due to
"invalid argument". So we need another check.


>
> Tycho
>
> >
> >
> > > Tycho
> > >
> > > >               pr_perror("Failed closing %s", path);
> > > >               return -1;
> > > >       }
> > > > --
> > > > 1.9.1
> > > >
> > > > _______________________________________________
> > > > CRIU mailing list
> > > > CRIU at openvz.org
> > > > https://lists.openvz.org/mailman/listinfo/criu
> > >
>
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