[PATCH master 18/24] Add _GetCgroupInstanceValue in hv_lxc

[Yuto KAWAMURA(kawamuray)]

_GetCgroupInstanceValue reads a cgroup parameter of an instance from the
cgroup fs and returns it.
This method added to provide the unified interface for reading cgroup
parameters and remove code which violates the DRY rule.

Signed-off-by: Yuto KAWAMURA(kawamuray) <kawamuray.dad...@gmail.com>
---
 lib/hypervisor/hv_lxc.py | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/lib/hypervisor/hv_lxc.py b/lib/hypervisor/hv_lxc.py
index 963659c..38dee2a 100644
--- a/lib/hypervisor/hv_lxc.py
+++ b/lib/hypervisor/hv_lxc.py
@@ -234,36 +234,52 @@ class LXCHypervisor(hv_base.BaseHypervisor):
     return cls._MountCgroupSubsystem(subsystem)
 
   @classmethod
+  def _GetCgroupInstanceValue(cls, instance_name, subsystem, param):
+    """Return the value of the specified cgroup parameter.
+
+    @type instance_name: string
+    @param instance_name: instance name
+    @type subsystem: string
+    @param subsystem: cgroup subsystem name
+    @type param: string
+    @param param: cgroup subsystem parameter name
+    @rtype string
+    @return value read from cgroup subsystem fs
+
+    """
+    subsys_dir = cls._GetOrPrepareCgroupSubsysMountPoint(subsystem)
+    param_file = utils.PathJoin(subsys_dir, "lxc", instance_name, param)
+    return utils.ReadFile(param_file).rstrip("\n")
+
+  @classmethod
   def _GetCgroupCpuList(cls, instance_name):
     """Return the list of CPU ids for an instance.
 
     """
-    cgroup = cls._GetOrPrepareCgroupSubsysMountPoint("cpuset")
     try:
-      cpus = utils.ReadFile(utils.PathJoin(cgroup, 'lxc',
-                                           instance_name,
-                                           "cpuset.cpus"))
+      cpumask = cls._GetCgroupInstanceValue(instance_name,
+                                            "cpuset", "cpuset.cpus")
     except EnvironmentError, err:
       raise errors.HypervisorError("Getting CPU list for instance"
                                    " %s failed: %s" % (instance_name, err))
 
-    return utils.ParseCpuMask(cpus)
+    return utils.ParseCpuMask(cpumask)
 
   @classmethod
   def _GetCgroupMemoryLimit(cls, instance_name):
     """Return the memory limit for an instance
 
     """
-    cgroup = cls._GetOrPrepareCgroupSubsysMountPoint("memory")
     try:
-      memory = int(utils.ReadFile(utils.PathJoin(cgroup, 'lxc',
-                                                 instance_name,
-                                                 "memory.limit_in_bytes")))
+      mem_limit = cls._GetCgroupInstanceValue(instance_name,
+                                              "memory",
+                                              "memory.limit_in_bytes")
+      mem_limit = int(mem_limit)
     except EnvironmentError:
       # memory resource controller may be disabled, ignore
-      memory = 0
+      mem_limit = 0
 
-    return memory
+    return mem_limit
 
   def ListInstances(self, hvparams=None):
     """Get the list of running instances.
-- 
1.8.5.5