Merge pull request #2684 from brauner/2018-10-10/cgfsng_improve_logging

cgfsng: improve deletion and logging

src/lxc/cgroups/cgfsng.c

@@ -1152,6 +1152,7 @@ __cgfsng_ops static void cgfsng_monitor_destroy(struct cgroup_ops *ops,
 
 	for (int i = 0; ops->hierarchies[i]; i++) {
 		int ret;
+		char *chop;
 		struct hierarchy *h = ops->hierarchies[i];
 
 		if (!h->monitor_full_path)
@@ -1169,16 +1170,27 @@ __cgfsng_ops static void cgfsng_monitor_destroy(struct cgroup_ops *ops,
 						    PIVOT_CGROUP,
 						    "cgroup.procs", NULL);
 
+		chop = strrchr(pivot_path, '/');
+		if (chop)
+			*chop = '\0';
+
 		ret = mkdir_p(pivot_path, 0755);
-		if (ret < 0 && errno != EEXIST)
+		if (ret < 0 && errno != EEXIST) {
+			SYSWARN("Failed to create cgroup \"%s\"\n", pivot_path);
 			goto next;
+		}
+
+		if (chop)
+			*chop = '/';
 
 		/* Move ourselves into the pivot cgroup to delete our own
 		 * cgroup.
 		 */
 		ret = lxc_write_to_file(pivot_path, pidstr, len, false, 0666);
-		if (ret != 0)
+		if (ret != 0) {
+			SYSWARN("Failed to move monitor %s to \"%s\"\n", pidstr, pivot_path);
 			goto next;
+		}
 
 		ret = recursive_destroy(h->monitor_full_path);
 		if (ret < 0)