add interface virCgroupGetMemSwapUsage

virCgroupGetMemSwapUsage is used to get container's swap usage,
with this interface,we can get swap usage in fuse filesystem.
Signed-off-by: NGao feng <gaofeng@cn.fujitsu.com>

src/libvirt_private.syms

@@ -98,6 +98,7 @@ virCgroupGetCpuacctUsage;
 virCgroupGetCpusetCpus;
 virCgroupGetCpusetMems;
 virCgroupGetFreezerState;
+virCgroupGetMemSwapUsage;
 virCgroupGetMemSwapHardLimit;
 virCgroupGetMemoryHardLimit;
 virCgroupGetMemorySoftLimit;

src/util/cgroup.c

@@ -1370,6 +1370,26 @@ int virCgroupGetMemSwapHardLimit(virCgroupPtr group, unsigned long long *kb)
     return ret;
 }
 
+/**
+ * virCgroupGetMemSwapUsage:
+ *
+ * @group: The cgroup to get mem+swap usage for
+ * @kb: The mem+swap amount in kilobytes
+ *
+ * Returns: 0 on success
+ */
+int virCgroupGetMemSwapUsage(virCgroupPtr group, unsigned long long *kb)
+{
+    long long unsigned int usage_in_bytes;
+    int ret;
+    ret = virCgroupGetValueU64(group,
+                               VIR_CGROUP_CONTROLLER_MEMORY,
+                               "memory.memsw.usage_in_bytes", &usage_in_bytes);
+    if (ret == 0)
+        *kb = usage_in_bytes >> 10;
+    return ret;
+}
+
 /**
  * virCgroupSetCpusetMems:
  *

src/util/cgroup.h

@@ -92,6 +92,7 @@ int virCgroupSetMemorySoftLimit(virCgroupPtr group, unsigned long long kb);
 int virCgroupGetMemorySoftLimit(virCgroupPtr group, unsigned long long *kb);
 int virCgroupSetMemSwapHardLimit(virCgroupPtr group, unsigned long long kb);
 int virCgroupGetMemSwapHardLimit(virCgroupPtr group, unsigned long long *kb);
+int virCgroupGetMemSwapUsage(virCgroupPtr group, unsigned long long *kb);
 
 enum {
     VIR_CGROUP_DEVICE_READ  = 1,