[CRIU] [PATCH 2/5] mnt: add --enable-external-sharing flag

[Tycho Andersen]

On Thu, Apr 09, 2015 at 07:49:14PM +0300, Pavel Emelyanov wrote:
> On 04/09/2015 07:32 PM, Tycho Andersen wrote:
> > With this flag, external shared bind mounts are attempted to be resolved
> > automatically.
> 
> Just a question -- what if we specify external mount map manually, would
> the sharing/slavery get resolved?

It isn't now, but it could be with a simple change. Right now the
behavior of --ext-mount-map KEY:VAL is (I hope) exactly as it was
before.

Tycho

> > v2: don't always assume when the sharing matches that the mount matches
> > 
> > Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> > ---
> >  crtools.c            |  6 ++++++
> >  include/cr_options.h |  1 +
> >  include/proc_parse.h |  1 +
> >  mount.c              | 20 +++++++++++++++++++-
> >  protobuf/mnt.proto   |  1 +
> >  5 files changed, 28 insertions(+), 1 deletion(-)
> > 
> > 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/include/proc_parse.h b/include/proc_parse.h
> > index a0fee1f..e5d59d2 100644
> > --- a/include/proc_parse.h
> > +++ b/include/proc_parse.h
> > @@ -130,6 +130,7 @@ struct mount_info {
> >  	struct ns_id	*nsid;
> >  
> >  	struct ext_mount *external;
> > +	bool		internal_sharing;
> >  
> >  	/* tree linkage */
> >  	struct mount_info *parent;
> > diff --git a/mount.c b/mount.c
> > index 154c389..fc334cf 100644
> > --- a/mount.c
> > +++ b/mount.c
> > @@ -734,6 +734,14 @@ static int resolve_external_mounts(struct mount_info *info)
> >  		if (!match)
> >  			continue;
> >  
> > +		if (m->flags & MS_SHARED) {
> > +			if (!opts.enable_external_sharing)
> > +				continue;
> > +
> > +			if (m->shared_id != match->shared_id)
> > +				m->internal_sharing = true;
> > +		}
> > +
> >  		size = strlen(match->mountpoint + 1) + strlen(m->root) + 1;
> >  		p = xmalloc(sizeof(char) * size);
> >  		if (!p)
> > @@ -1312,6 +1320,11 @@ static int dump_one_mountpoint(struct mount_info *pm, struct cr_img *img)
> >  		me.with_plugin = true;
> >  	}
> >  
> > +	if (pm->internal_sharing) {
> > +		me.has_internal_sharing = true;
> > +		me.internal_sharing = true;
> > +	}
> > +
> >  	if (pm->external) {
> >  		/*
> >  		 * For external mount points dump the mapping's
> > @@ -1653,6 +1666,7 @@ static int restore_ext_mount(struct mount_info *mi)
> >  static int do_bind_mount(struct mount_info *mi)
> >  {
> >  	bool shared = 0;
> > +	bool force_private_remount = false;
> >  
> >  	if (!mi->need_plugin) {
> >  		char *root, rpath[PATH_MAX];
> > @@ -1666,6 +1680,7 @@ static int do_bind_mount(struct mount_info *mi)
> >  			 * to proper location in the namespace we restore.
> >  			 */
> >  			root = mi->root;
> > +			force_private_remount = mi->internal_sharing;
> >  			goto do_bind;
> >  		}
> >  
> > @@ -1702,7 +1717,7 @@ do_bind:
> >  	 * shared - the mount is in the same shared group with mi->bind
> >  	 * mi->shared_id && !shared - create a new shared group
> >  	 */
> > -	if (restore_shared_options(mi, !shared && !mi->master_id,
> > +	if (restore_shared_options(mi, force_private_remount || (!shared && !mi->master_id),
> >  					mi->shared_id && !shared,
> >  					mi->master_id))
> >  		return -1;
> > @@ -2014,6 +2029,9 @@ static int collect_mnt_from_image(struct mount_info **pms, struct ns_id *nsid)
> >  		if (!pm->source)
> >  			goto err;
> >  
> > +		if (me->has_internal_sharing)
> > +			pm->internal_sharing = me->internal_sharing;
> > +
> >  		/* FIXME: abort unsupported early */
> >  		pm->fstype		= decode_fstype(me->fstype);
> >  
> > diff --git a/protobuf/mnt.proto b/protobuf/mnt.proto
> > index 343bd6d..3244411 100644
> > --- a/protobuf/mnt.proto
> > +++ b/protobuf/mnt.proto
> > @@ -35,4 +35,5 @@ message mnt_entry {
> >  
> >  	optional bool		with_plugin		= 12;
> >  	optional bool		ext_mount		= 13;
> > +	optional bool		internal_sharing	= 14;
> >  }
> > 
>