sysctl: decouple reading sysctl.conf(5) from setting the sysctls

Currently reapply_sysctl=1 will cause sysctl.conf(5) and sysctl.d(5) to
be loaded and all the sysctls configured set after sysctls that TuneD
decides to set.

There are some issues with this approach I'll address in a follow-up
commit. This one (hopefully) doesn't change the behavior.

Signed-off-by: Lubomir Rintel <[email protected]>

tuned/plugins/plugin_sysctl.py

@@ -65,6 +65,7 @@ def _instance_cleanup(self, instance):
 		self._storage.unset(storage_key)
 
 	def _instance_apply_static(self, instance):
+		system_sysctl = _read_system_sysctl()
 		for option, value in list(instance._sysctl.items()):
 			original_value = _read_sysctl(option)
 			if original_value is None:
@@ -84,7 +85,12 @@ def _instance_apply_static(self, instance):
 
 		if self._global_cfg.get_bool(consts.CFG_REAPPLY_SYSCTL, consts.CFG_DEF_REAPPLY_SYSCTL):
 			log.info("reapplying system sysctl")
-			_apply_system_sysctl(instance._sysctl)
+			for option, value in list(system_sysctl.items()):
+				if option in instance._sysctl and instance._sysctl[option] != value:
+					log.info("Overriding sysctl parameter '%s' from '%s' to '%s'"
+							% (option, instance._sysctl[option], value))
+				_write_sysctl(option, value, ignore_missing = True)
+
 
 	def _instance_verify_static(self, instance, ignore_missing, devices):
 		ret = True
@@ -103,7 +109,8 @@ def _instance_unapply_static(self, instance, full_rollback = False):
 			_write_sysctl(option, value)
 
 
-def _apply_system_sysctl(instance_sysctl):
+def _read_system_sysctl():
+	sysctls = {}
 	files = {}
 	for d in SYSCTL_CONFIG_DIRS:
 		try:
@@ -119,23 +126,28 @@ def _apply_system_sysctl(instance_sysctl):
 	for fname in sorted(files.keys()):
 		d = files[fname]
 		path = "%s/%s" % (d, fname)
-		_apply_sysctl_config_file(path, instance_sysctl)
-	_apply_sysctl_config_file("/etc/sysctl.conf", instance_sysctl)
+		sysctls.update(_read_sysctl_config_file(path))
+	sysctls.update(_read_sysctl_config_file("/etc/sysctl.conf"))
+	return sysctls
 
-def _apply_sysctl_config_file(path, instance_sysctl):
-	log.debug("Applying sysctl settings from file %s" % path)
+def _read_sysctl_config_file(path):
+	log.debug("Reading sysctl settings from file %s" % path)
+	sysctls = {}
 	try:
 		with open(path, "r") as f:
 			for lineno, line in enumerate(f, 1):
-				_apply_sysctl_config_line(path, lineno, line, instance_sysctl)
-		log.debug("Finished applying sysctl settings from file %s"
+				sysctl_line = _read_sysctl_config_line(path, lineno, line)
+				if sysctl_line is not None:
+					sysctls[sysctl_line[0]] = sysctl_line[1]
+		log.debug("Finished reading sysctl settings from file %s"
 				% path)
 	except (OSError, IOError) as e:
 		if e.errno != errno.ENOENT:
 			log.error("Error reading sysctl settings from file %s: %s"
 					% (path, str(e)))
+	return sysctls
 
-def _apply_sysctl_config_line(path, lineno, line, instance_sysctl):
+def _read_sysctl_config_line(path, lineno, line):
 	line = line.strip()
 	if len(line) == 0 or line[0] == "#" or line[0] == ";":
 		return
@@ -150,12 +162,7 @@ def _apply_sysctl_config_line(path, lineno, line, instance_sysctl):
 		log.error("Syntax error in file %s, line %d"
 				% (path, lineno))
 		return
-	value = value.strip()
-	if option in instance_sysctl and instance_sysctl[option] != value:
-		log.info("Overriding sysctl parameter '%s' from '%s' to '%s'"
-				% (option, instance_sysctl[option], value))
-
-	_write_sysctl(option, value, ignore_missing = True)
+	return (option, value.strip())
 
 def _get_sysctl_path(option):
 	return "/proc/sys/%s" % option.replace(".", "/")