mounts: Mark ns' roots in the list of mount points (v2)

When we'll restore nested mount namespaces, all but root ones (sub-namespaces)
will be restored as sub-mounts in the root mount namespace. So mi->mountpoint
will be not '/' even if a mount is root for its mntns.

v2: s/is_root/is_ns_root/
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/proc_parse.h

@@ -119,6 +119,7 @@ struct mount_info {
 	bool		mounted;
 	bool		need_plugin;
 	int		is_file;
+	bool		is_ns_root;
 	struct mount_info *next;
 
 	/* tree linkage */

mount.c

@@ -1405,6 +1405,7 @@ static struct mount_info *read_mnt_ns_img(int ns_pid)
 		pm->shared_id		= me->shared_id;
 		pm->master_id		= me->master_id;
 		pm->need_plugin		= me->with_plugin;
+		pm->is_ns_root		= is_root(me->mountpoint);
 
 		/* FIXME: abort unsupported early */
 		pm->fstype		= decode_fstype(me->fstype);