Merge pull request #29622 from rootfs/rbd-ro

plugin/pkg/scheduler/algorithm/predicates/predicates.go

@@ -121,7 +121,10 @@ func isVolumeConflict(volume api.Volume, pod *api.Pod) bool {
 		if volume.RBD != nil && existingVolume.RBD != nil {
 			mon, pool, image := volume.RBD.CephMonitors, volume.RBD.RBDPool, volume.RBD.RBDImage
 			emon, epool, eimage := existingVolume.RBD.CephMonitors, existingVolume.RBD.RBDPool, existingVolume.RBD.RBDImage
-			if haveSame(mon, emon) && pool == epool && image == eimage {
+			// two RBDs images are the same if they share the same Ceph monitor, are in the same RADOS Pool, and have the same image name
+			// only one read-write mount is permitted for the same RBD image.
+			// same RBD image mounted by multiple Pods conflicts unless all Pods mount the image read-only
+			if haveSame(mon, emon) && pool == epool && image == eimage && !(volume.RBD.ReadOnly && existingVolume.RBD.ReadOnly) {
 				return true
 			}
 		}