Store cgroup manager on a per-container basis

When we create a container, we assign a cgroup parent based on
the current cgroup manager in use. This parent is only usable
with the cgroup manager the container is created with, so if the
default cgroup manager is later changed or overridden, the
container will not be able to start.

To solve this, store the cgroup manager that created the
container in container configuration, so we can guarantee a
container with a systemd cgroup parent will always be started
with systemd cgroups.

Unfortunately, this is very difficult to test in CI, due to the
fact that we hard-code cgroup manager on all invocations of
Podman in CI.

Fixes #7830

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 4 insertions, 3 deletions

diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 41cc80789..3a71c6601 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -1965,6 +1965,7 @@ func (c *Container) getOCICgroupPath() (string, error) {
 	if err != nil {
 		return "", err
 	}
+	cgroupManager := c.CgroupManager()
 	switch {
 	case (rootless.IsRootless() && !unified) || c.config.NoCgroups:
 		return "", nil
@@ -1977,14 +1978,14 @@ func (c *Container) getOCICgroupPath() (string, error) {
 			return "", err
 		}
 		return filepath.Join(selfCgroup, "container"), nil
-	case c.runtime.config.Engine.CgroupManager == config.SystemdCgroupsManager:
+	case cgroupManager == config.SystemdCgroupsManager:
 		// When the OCI runtime is set to use Systemd as a cgroup manager, it
 		// expects cgroups to be passed as follows:
 		// slice:prefix:name
 		systemdCgroups := fmt.Sprintf("%s:libpod:%s", path.Base(c.config.CgroupParent), c.ID())
 		logrus.Debugf("Setting CGroups for container %s to %s", c.ID(), systemdCgroups)
 		return systemdCgroups, nil
-	case c.runtime.config.Engine.CgroupManager == config.CgroupfsCgroupsManager:
+	case cgroupManager == config.CgroupfsCgroupsManager:
 		cgroupPath, err := c.CGroupPath()
 		if err != nil {
 			return "", err
@@ -1992,7 +1993,7 @@ func (c *Container) getOCICgroupPath() (string, error) {
 		logrus.Debugf("Setting CGroup path for container %s to %s", c.ID(), cgroupPath)
 		return cgroupPath, nil
 	default:
-		return "", errors.Wrapf(define.ErrInvalidArg, "invalid cgroup manager %s requested", c.runtime.config.Engine.CgroupManager)
+		return "", errors.Wrapf(define.ErrInvalidArg, "invalid cgroup manager %s requested", cgroupManager)
 	}
 }