cgroups/cgfsng: rework cgfsng_monitor_create()

src/lxc/cgroups/cgfsng.c

@@ -1303,14 +1303,22 @@ __cgfsng_ops static inline bool cgfsng_monitor_create(struct cgroup_ops *ops,
 	char *offset, *tmp;
 	int i, idx = 0;
 	size_t len;
-	struct lxc_conf *conf = handler->conf;
+	struct lxc_conf *conf;
 
-	if (!conf)
-		return false;
+	if (!ops)
+		return ret_set_errno(false, ENOENT);
 
 	if (!ops->hierarchies)
 		return true;
 
+	if (ops->monitor_cgroup)
+		return ret_set_errno(false, EEXIST);
+
+	if (!handler || !handler->conf)
+		return ret_set_errno(false, EINVAL);
+
+	conf = handler->conf;
+
 	if (conf->cgroup_meta.dir)
 		tmp = lxc_string_join("/",
 				      (const char *[]){conf->cgroup_meta.dir,
@@ -1320,7 +1328,7 @@ __cgfsng_ops static inline bool cgfsng_monitor_create(struct cgroup_ops *ops,
 	else
 		tmp = must_make_path(ops->monitor_pattern, handler->name, NULL);
 	if (!tmp)
-		return false;
+		return ret_set_errno(false, ENOMEM);
 
 	len = strlen(tmp) + 5; /* leave room for -NNN\0 */
 	monitor_cgroup = must_realloc(tmp, len);
@@ -1328,11 +1336,8 @@ __cgfsng_ops static inline bool cgfsng_monitor_create(struct cgroup_ops *ops,
 	*offset = 0;
 
 	do {
-		if (idx) {
-			int ret = snprintf(offset, 5, "-%d", idx);
-			if (ret < 0 || (size_t)ret >= 5)
-				return false;
-		}
+		if (idx)
+			sprintf(offset, "-%d", idx);
 
 		for (i = 0; ops->hierarchies[i]; i++) {
 			if (!monitor_create_path_for_hierarchy(ops->hierarchies[i],
@@ -1351,11 +1356,10 @@ __cgfsng_ops static inline bool cgfsng_monitor_create(struct cgroup_ops *ops,
 	} while (ops->hierarchies[i] && idx > 0 && idx < 1000);
 
 	if (idx == 1000)
-		return false;
+		return ret_set_errno(false, ERANGE);
 
-	INFO("The monitor process uses \"%s\" as cgroup", monitor_cgroup);
 	ops->monitor_cgroup = move_ptr(monitor_cgroup);
-	return true;
+	return log_info(true, "The monitor process uses \"%s\" as cgroup", monitor_cgroup);
 }
 
 /* Try to create the same cgroup in all hierarchies. Start with cgroup_pattern;

src/lxc/log.h

@@ -512,7 +512,7 @@ __unused static inline void LXC_##LEVEL(struct lxc_log_locinfo* locinfo,	\
 
 #define log_debug_errno(__ret__, __errno__, format, ...) \
 	({						 \
-		errno = __errno__;			\
+		errno = __errno__;		         \
 		SYSDEBUG(format, ##__VA_ARGS__);	 \
 		__ret__;				 \
 	})
@@ -523,6 +523,12 @@ __unused static inline void LXC_##LEVEL(struct lxc_log_locinfo* locinfo,	\
 		__ret__;		      \
 	})
 
+#define log_info(__ret__, format, ...)       \
+	({                                   \
+		INFO(format, ##__VA_ARGS__); \
+		__ret__;                     \
+	})
+
 extern int lxc_log_fd;
 
 extern int lxc_log_syslog(int facility);