podman: add new option --cgroups=no-conmon

it allows to disable cgroups creation only for the conmon process.

A new cgroup is created for the container payload.

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

3 files changed, 22 insertions, 12 deletions

diff --git a/libpod/container.go b/libpod/container.go
index b3cb6334a..f29cebf20 100644
--- a/libpod/container.go
+++ b/libpod/container.go
@@ -373,8 +373,11 @@ type ContainerConfig struct {
 	// Time container was created
 	CreatedTime time.Time `json:"createdTime"`
 	// NoCgroups indicates that the container will not create CGroups. It is
-	// incompatible with CgroupParent.
+	// incompatible with CgroupParent.  Deprecated in favor of CgroupsMode.
 	NoCgroups bool `json:"noCgroups,omitempty"`
+	// CgroupsMode indicates how the container will create cgroups
+	// (disabled, no-conmon, enabled).  It supersedes NoCgroups.
+	CgroupsMode string `json:"cgroupsMode,omitempty"`
 	// Cgroup parent of the container
 	CgroupParent string `json:"cgroupParent"`
 	// LogPath log location
diff --git a/libpod/oci_conmon_linux.go b/libpod/oci_conmon_linux.go
index 5ab0e73c4..7c7ec8b2c 100644
--- a/libpod/oci_conmon_linux.go
+++ b/libpod/oci_conmon_linux.go
@@ -1297,11 +1297,17 @@ func startCommandGivenSelinux(cmd *exec.Cmd) error {
 // it then signals for conmon to start by sending nonse data down the start fd
 func (r *ConmonOCIRuntime) moveConmonToCgroupAndSignal(ctr *Container, cmd *exec.Cmd, startFd *os.File) error {
 	mustCreateCgroup := true
-	// If cgroup creation is disabled - just signal.
+
 	if ctr.config.NoCgroups {
 		mustCreateCgroup = false
 	}
 
+	// If cgroup creation is disabled - just signal.
+	switch ctr.config.CgroupsMode {
+	case "disabled", "no-conmon":
+		mustCreateCgroup = false
+	}
+
 	if mustCreateCgroup {
 		cgroupParent := ctr.CgroupParent()
 		if r.cgroupManager == define.SystemdCgroupsManager {
diff --git a/libpod/options.go b/libpod/options.go
index 8bc5a541d..593037382 100644
--- a/libpod/options.go
+++ b/libpod/options.go
@@ -1078,25 +1078,26 @@ func WithLogTag(tag string) CtrCreateOption {
 
 }
 
-// WithNoCgroups disables the creation of CGroups for the new container.
-func WithNoCgroups() CtrCreateOption {
+// WithCgroupsMode disables the creation of CGroups for the conmon process.
+func WithCgroupsMode(mode string) CtrCreateOption {
 	return func(ctr *Container) error {
 		if ctr.valid {
 			return define.ErrCtrFinalized
 		}
 
-		if ctr.config.CgroupParent != "" {
-			return errors.Wrapf(define.ErrInvalidArg, "NoCgroups conflicts with CgroupParent")
-		}
-
-		if ctr.config.PIDNsCtr != "" {
-			return errors.Wrapf(define.ErrInvalidArg, "NoCgroups requires a private PID namespace and cannot be used when PID namespace is shared with another container")
+		switch mode {
+		case "disabled":
+			ctr.config.NoCgroups = true
+			ctr.config.CgroupsMode = mode
+		case "enabled", "no-conmon":
+			ctr.config.CgroupsMode = mode
+		default:
+			return errors.Wrapf(define.ErrInvalidArg, "Invalid cgroup mode %q", mode)
 		}
 
-		ctr.config.NoCgroups = true
-
 		return nil
 	}
+
 }
 
 // WithCgroupParent sets the Cgroup Parent of the new container.