ceph: mgr fix startup

Because the manager is running under the 'ceph' user the cephfs
subvolume plugin can not create directories anymore. It fails with a
permission denied because of the usage of the 'ceph' user, root is need
here, hence the special startup line to go over this.

Closes: https://github.com/ceph/ceph-csi/issues/486
Signed-off-by: Sébastien Han <seb@redhat.com>

pkg/operator/ceph/cluster/mgr/spec.go

@@ -25,6 +25,7 @@ import (
 	rookcephv1 "github.com/rook/rook/pkg/apis/ceph.rook.io/v1"
 	"github.com/rook/rook/pkg/daemon/ceph/client"
 	"github.com/rook/rook/pkg/operator/ceph/cluster/mon"
+	"github.com/rook/rook/pkg/operator/ceph/config"
 	"github.com/rook/rook/pkg/operator/ceph/config/keyring"
 	opspec "github.com/rook/rook/pkg/operator/ceph/spec"
 	cephver "github.com/rook/rook/pkg/operator/ceph/version"
@@ -240,6 +241,10 @@ func (c *Cluster) makeMgrDaemonContainer(mgrConfig *mgrConfig) v1.Container {
 		},
 		Args: append(
 			opspec.DaemonFlags(c.clusterInfo, mgrConfig.DaemonID),
+			// for ceph-mgr cephfs
+			// see https://github.com/ceph/ceph-csi/issues/486 for more details
+			config.NewFlag("client-mount-uid", "0"),
+			config.NewFlag("client-mount-gid", "0"),
 			"--foreground",
 		),
 		Image:        c.cephVersion.Image,