Don't return an error on failure to create blkio controller

This patch enables cgroup controllers as much as possible by skipping
the creation of blkio controller when running with old kernels that
doesn't support multi-level directory for blkio controller.

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/src/util/cgroup.c b/src/util/cgroup.c
index 9a41a62dc35082d2cd834b6f2c2e58b27592877e..afe873118a3a79ef2259f214afc07e75bf2382cb 100644 (file)
--- a/src/util/cgroup.c
+++ b/src/util/cgroup.c
@@ -527,9 +527,20 @@ static int virCgroupMakeGroup(virCgroupPtr parent, virCgroupPtr group,
         if (access(path, F_OK) != 0) {
             if (!create ||
                 mkdir(path, 0755) < 0) {
-                rc = -errno;
-                VIR_FREE(path);
-                break;
+                /* With a kernel that doesn't support multi-level directory
+                 * for blkio controller, libvirt will fail and disable all
+                 * other controllers even though they are available. So
+                 * treat blkio as unmounted if mkdir fails. */
+                if (i == VIR_CGROUP_CONTROLLER_BLKIO) {
+                    rc = 0;
+                    VIR_FREE(group->controllers[i].mountPoint);
+                    VIR_FREE(path);
+                    continue;
+                } else {
+                    rc = -errno;
+                    VIR_FREE(path);
+                    break;
+                }
             }
             if (group->controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint != NULL &&
                 (i == VIR_CGROUP_CONTROLLER_CPUSET ||