distribute dd evenly across nodes

Signed-off-by: Lyndon-Li <lyonghui@vmware.com>

changelogs/unreleased/8611-Lyndon-Li

@@ -0,0 +1 @@
+Fix issue #8242, distribute dd evenly across nodes

pkg/exposer/generic_restore.go

@@ -400,6 +400,11 @@ func (e *genericRestoreExposer) createRestorePod(ctx context.Context, ownerObjec
 	}}
 	volumes = append(volumes, podInfo.volumes...)
 
+	if label == nil {
+		label = make(map[string]string)
+	}
+	label[podGroupLabel] = podGroupGenericRestore
+
 	volumeMode := corev1.PersistentVolumeFilesystem
 	if targetPVC.Spec.VolumeMode != nil {
 		volumeMode = *targetPVC.Spec.VolumeMode
@@ -462,6 +467,18 @@ func (e *genericRestoreExposer) createRestorePod(ctx context.Context, ownerObjec
 			Labels: label,
 		},
 		Spec: corev1.PodSpec{
+			TopologySpreadConstraints: []corev1.TopologySpreadConstraint{
+				{
+					MaxSkew:           1,
+					TopologyKey:       "kubernetes.io/hostname",
+					WhenUnsatisfiable: corev1.ScheduleAnyway,
+					LabelSelector: &metav1.LabelSelector{
+						MatchLabels: map[string]string{
+							podGroupLabel: podGroupGenericRestore,
+						},
+					},
+				},
+			},
 			NodeSelector: nodeSelector,
 			OS:           &podOS,
 			Containers: []corev1.Container{

pkg/exposer/types.go

@@ -21,10 +21,11 @@ import (
 )
 
 const (
-	AccessModeFileSystem = "by-file-system"
-	AccessModeBlock      = "by-block-device"
-	podGroupLabel        = "velero.io/exposer-pod-group"
-	podGroupSnapshot     = "snapshot-exposer"
+	AccessModeFileSystem   = "by-file-system"
+	AccessModeBlock        = "by-block-device"
+	podGroupLabel          = "velero.io/exposer-pod-group"
+	podGroupSnapshot       = "snapshot-exposer"
+	podGroupGenericRestore = "generic-restore-exposer"
 )
 
 // ExposeResult defines the result of expose.