start: avoid unnecessary syscalls

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/start.c b/src/lxc/start.c
index 66a801eaf21387e8ef473e9f0d5a03e26c606164..951548dc0e4541f6985f83f08e7c6a8ea9383726 100644 (file)
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -1050,6 +1050,8 @@ static int do_start(void *data)
        uid_t new_uid;
        gid_t new_gid;
        struct lxc_list *iterator;
+       uid_t nsuid = 0;
+       gid_t nsgid = 0;
        int devnull_fd = -1;
        struct lxc_handler *handler = data;
 
@@ -1117,12 +1119,11 @@ static int do_start(void *data)
         * privilege over our namespace.
         */
        if (!lxc_list_empty(&handler->conf->id_map)) {
-               uid_t nsuid = (handler->conf->root_nsuid_map != NULL)
-                                 ? 0
-                                 : handler->conf->init_uid;
-               gid_t nsgid = (handler->conf->root_nsgid_map != NULL)
-                                 ? 0
-                                 : handler->conf->init_gid;
+               if (!handler->conf->root_nsuid_map)
+                       nsuid = handler->conf->init_uid;
+
+               if (!handler->conf->root_nsgid_map)
+                       nsgid = handler->conf->init_gid;
 
                ret = lxc_switch_uid_gid(nsuid, nsgid);
                if (ret < 0)
@@ -1370,6 +1371,13 @@ static int do_start(void *data)
                        goto out_warn_father;
        }
 
+       /* Avoid unnecessary syscalls. */
+       if (new_uid == nsuid)
+               new_uid = LXC_INVALID_UID;
+
+       if (new_gid == nsgid)
+               new_gid = LXC_INVALID_GID;
+
        ret = lxc_switch_uid_gid(new_uid, new_gid);
        if (ret < 0)
                goto out_warn_father;