[CRIU] [PATCH 3/6] mnt: add --enable-external-sharing flag

[Tycho Andersen]

On Wed, Apr 08, 2015 at 04:14:27PM +0300, Andrew Vagin wrote:
> On Tue, Apr 07, 2015 at 11:37:18PM +0000, Tycho Andersen wrote:
> > With this flag, external shared bind mounts are attempted to be resolved
> > automatically.
> > 
> > Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> > ---
> >  crtools.c            | 6 ++++++
> >  include/cr_options.h | 1 +
> >  mount.c              | 3 +++
> >  3 files changed, 10 insertions(+)
> > 
> > diff --git a/crtools.c b/crtools.c
> > index a6ee2d7..fe77f39 100644
> > --- a/crtools.c
> > +++ b/crtools.c
> > @@ -204,6 +204,7 @@ int main(int argc, char *argv[], char *envp[])
> >  		{ "inherit-fd",		required_argument,	0, 1062	},
> >  		{ "feature",		required_argument,	0, 1063	},
> >  		{ "skip-mnt",		required_argument,	0, 1064},
> > +		{ "enable-external-sharing", no_argument, 	0, 1065 },
> >  		{ },
> >  	};
> >  
> > @@ -421,6 +422,9 @@ int main(int argc, char *argv[], char *envp[])
> >  			if (!add_skip_mount(optarg))
> >  				return 1;
> >  			break;
> > +		case 1065:
> > +			opts.enable_external_sharing = true;
> > +			break;
> >  		case 'M':
> >  			{
> >  				char *aux;
> > @@ -649,6 +653,8 @@ usage:
> >  "                        add external mount mapping\n"
> >  "  -M|--ext-mount-map auto\n"
> >  "                        attempt to autodetect external mount mapings\n"
> > +"  --enable-external-sharing\n"
> > +"                        allow autoresolving mounts with external sharing\n"
> >  "  --manage-cgroups      dump or restore cgroups the process is in\n"
> >  "  --cgroup-root [controller:]/newroot\n"
> >  "                        change the root cgroup the controller will be\n"
> > diff --git a/include/cr_options.h b/include/cr_options.h
> > index f1cfc84..29be2c8 100644
> > --- a/include/cr_options.h
> > +++ b/include/cr_options.h
> > @@ -63,6 +63,7 @@ struct cr_options {
> >  	char			*new_global_cg_root;
> >  	struct list_head	new_cgroup_roots;
> >  	bool			autodetect_ext_mounts;
> > +	bool			enable_external_sharing;
> >  	bool			aufs;		/* auto-deteced, not via cli */
> >  };
> >  
> > diff --git a/mount.c b/mount.c
> > index 49a07dd..8835a81 100644
> > --- a/mount.c
> > +++ b/mount.c
> > @@ -688,6 +688,9 @@ static int resolve_external_mounts(struct mount_info *info)
> >  			if (mounts_equal(pm, m, true))
> >  				match = true;
> >  
> > +			if (opts.enable_external_sharing && pm->shared_id == m->shared_id)
> > +				match = true;
> 
> Are you sure that we need this check?
> 
> I think here is an opposite problem, when we found equal mounts and their
> shared are different. In this case we need to determin where this shared
> group is external or not.

Here we're only looking in the criu ns's mounts (i.e. pm is only
external mounts), so every match here should be external. As for
whether we need this check, I thought we did but re-reading
mounts_equal, maybe we don't. Are people allowed to re-mount shared
mounts with different options without having it propagate? That's the
only case I can think of where we would need this.

Tycho

> > +
> >  			if (!match)
> >  				continue;
> >  
> > -- 
> > 2.1.4
> > 
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