utils: reintroduce moveToCgroup

commit ee62711136339c5daf38e38859227d85b06fc32a introduced the
regression.

It was mistakenly removed as part of a cleanup, but this code is
needed by another code path, where we move conmon for the exec session
to the same cgroup used by conmon for the process.

Closes: https://github.com/containers/podman/issues/12535

[NO NEW TESTS NEEDED] it fixes a regression in the CI

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/utils/utils_supported.go b/utils/utils_supported.go
index 0f0c9a9ba..1404e3194 100644
--- a/utils/utils_supported.go
+++ b/utils/utils_supported.go
@@ -44,6 +44,15 @@ func RunUnderSystemdScope(pid int, slice string, unitName string) error {
 	ch := make(chan string)
 	_, err = conn.StartTransientUnit(unitName, "replace", properties, ch)
 	if err != nil {
+		// On errors check if the cgroup already exists, if it does move the process there
+		if props, err := conn.GetUnitTypeProperties(unitName, "Scope"); err == nil {
+			if cgroup, ok := props["ControlGroup"].(string); ok && cgroup != "" {
+				if err := moveUnderCgroup(cgroup, "", []uint32{uint32(pid)}); err == nil {
+					return nil
+				}
+				// On errors return the original error message we got from StartTransientUnit.
+			}
+		}
 		return err
 	}