vircgroup: introduce virCgroupGetInode function

For new feature Fibre Channel VMID we will need to get inode of the
VM root cgroup as it is used in the new kernel API together with VMID.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>

src/libvirt_private.syms

@@ -1922,6 +1922,7 @@ virCgroupGetCpuShares;
 virCgroupGetDevicePermsString;
 virCgroupGetDomainTotalCpuStats;
 virCgroupGetFreezerState;
+virCgroupGetInode;
 virCgroupGetMemoryHardLimit;
 virCgroupGetMemorySoftLimit;
 virCgroupGetMemoryStat;

src/util/vircgroup.c

@@ -3973,3 +3973,34 @@ virCgroupGetCpuPeriodQuota(virCgroup *cgroup, unsigned long long *period,
 
     return 0;
 }
+
+
+/**
+ * virCgroupGetInode:
+ *
+ * @cgroup: the cgroup to get inode for
+ *
+ * Get the @cgroup inode and return its value to the caller.
+ *
+ * Returns inode on success, -1 on error with error message reported.
+ */
+int
+virCgroupGetInode(virCgroup *cgroup)
+{
+    struct stat st;
+    int controller = virCgroupGetAnyController(cgroup);
+    g_autofree char *path = NULL;
+
+    if (controller < 0)
+        return -1;
+
+    if (virCgroupPathOfController(cgroup, controller, "", &path) < 0)
+        return -1;
+
+    if (stat(path, &st) < 0) {
+        virReportSystemError(errno, _("failed to get stat for '%s'"), path);
+        return -1;
+    }
+
+    return st.st_ino;
+}

src/util/vircgroup.h

@@ -283,3 +283,5 @@ int virCgroupSetOwner(virCgroup *cgroup,
 int virCgroupHasEmptyTasks(virCgroup *cgroup, int controller);
 
 bool virCgroupControllerAvailable(int controller);
+
+int virCgroupGetInode(virCgroup *cgroup);