Merge pull request #109715 from yibozhuang/volumerestrictions-refactor

Remove parallel node processing in PreFilter stage in volumerestrictions scheduler plugin

pkg/scheduler/framework/listers.go

@@ -18,17 +18,25 @@ package framework
 
 // NodeInfoLister interface represents anything that can list/get NodeInfo objects from node name.
 type NodeInfoLister interface {
-	// Returns the list of NodeInfos.
+	// List returns the list of NodeInfos.
 	List() ([]*NodeInfo, error)
-	// Returns the list of NodeInfos of nodes with pods with affinity terms.
+	// HavePodsWithAffinityList returns the list of NodeInfos of nodes with pods with affinity terms.
 	HavePodsWithAffinityList() ([]*NodeInfo, error)
-	// Returns the list of NodeInfos of nodes with pods with required anti-affinity terms.
+	// HavePodsWithRequiredAntiAffinityList returns the list of NodeInfos of nodes with pods with required anti-affinity terms.
 	HavePodsWithRequiredAntiAffinityList() ([]*NodeInfo, error)
-	// Returns the NodeInfo of the given node name.
+	// Get returns the NodeInfo of the given node name.
 	Get(nodeName string) (*NodeInfo, error)
 }
 
+// StorageInfoLister interface represents anything that handles storage-related operations and resources.
+type StorageInfoLister interface {
+	// IsPVCUsedByPods returns true/false on whether the PVC is used by one or more scheduled pods,
+	// keyed in the format "namespace/name".
+	IsPVCUsedByPods(key string) bool
+}
+
 // SharedLister groups scheduler-specific listers.
 type SharedLister interface {
 	NodeInfos() NodeInfoLister
+	StorageInfos() StorageInfoLister
 }

pkg/scheduler/framework/plugins/volumerestrictions/volume_restrictions.go

@@ -18,7 +18,6 @@ package volumerestrictions
 
 import (
 	"context"
-	"sync/atomic"
 
 	v1 "k8s.io/api/core/v1"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
@@ -27,16 +26,14 @@ import (
 	corelisters "k8s.io/client-go/listers/core/v1"
 	v1helper "k8s.io/kubernetes/pkg/apis/core/v1/helper"
 	"k8s.io/kubernetes/pkg/scheduler/framework"
-	"k8s.io/kubernetes/pkg/scheduler/framework/parallelize"
 	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/feature"
 	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/names"
 )
 
 // VolumeRestrictions is a plugin that checks volume restrictions.
 type VolumeRestrictions struct {
-	parallelizer           parallelize.Parallelizer
 	pvcLister              corelisters.PersistentVolumeClaimLister
-	nodeInfoLister         framework.SharedLister
+	sharedLister           framework.SharedLister
 	enableReadWriteOncePod bool
 }
 
@@ -132,12 +129,6 @@ func (pl *VolumeRestrictions) PreFilter(ctx context.Context, cycleState *framewo
 // use a ReadWriteOncePod PVC, mark any other pods attempting to use this PVC as UnschedulableAndUnresolvable.
 // TODO(#103132): Mark pod as Unschedulable and add preemption logic.
 func (pl *VolumeRestrictions) isReadWriteOncePodAccessModeConflict(ctx context.Context, pod *v1.Pod) *framework.Status {
-	nodeInfos, err := pl.nodeInfoLister.NodeInfos().List()
-	if err != nil {
-		return framework.NewStatus(framework.Error, "error while getting node info")
-	}
-
-	var pvcKeys []string
 	for _, volume := range pod.Spec.Volumes {
 		if volume.PersistentVolumeClaim == nil {
 			continue
@@ -155,29 +146,11 @@ func (pl *VolumeRestrictions) isReadWriteOncePodAccessModeConflict(ctx context.C
 			continue
 		}
 
-		key := pod.Namespace + "/" + volume.PersistentVolumeClaim.ClaimName
+		key := framework.GetNamespacedName(pod.Namespace, volume.PersistentVolumeClaim.ClaimName)
-		pvcKeys = append(pvcKeys, key)
+		if pl.sharedLister.StorageInfos().IsPVCUsedByPods(key) {
-	}
-
-	subCtx, cancel := context.WithCancel(ctx)
-	var conflicts uint32
-
-	processNode := func(i int) {
-		nodeInfo := nodeInfos[i]
-		for _, key := range pvcKeys {
-			refCount := nodeInfo.PVCRefCounts[key]
-			if refCount > 0 {
-				atomic.AddUint32(&conflicts, 1)
-				cancel()
-			}
-		}
-	}
-	pl.parallelizer.Until(subCtx, len(nodeInfos), processNode)
-
-	// Enforce ReadWriteOncePod access mode. This is also enforced during volume mount in kubelet.
-	if conflicts > 0 {
 			return framework.NewStatus(framework.UnschedulableAndUnresolvable, ErrReasonReadWriteOncePodConflict)
 		}
+	}
 
 	return nil
 }
@@ -232,12 +205,11 @@ func (pl *VolumeRestrictions) EventsToRegister() []framework.ClusterEvent {
 func New(_ runtime.Object, handle framework.Handle, fts feature.Features) (framework.Plugin, error) {
 	informerFactory := handle.SharedInformerFactory()
 	pvcLister := informerFactory.Core().V1().PersistentVolumeClaims().Lister()
-	nodeInfoLister := handle.SnapshotSharedLister()
+	sharedLister := handle.SnapshotSharedLister()
 
 	return &VolumeRestrictions{
-		parallelizer:           handle.Parallelizer(),
 		pvcLister:              pvcLister,
-		nodeInfoLister:         nodeInfoLister,
+		sharedLister:           sharedLister,
 		enableReadWriteOncePod: fts.EnableReadWriteOncePod,
 	}, nil
 }

pkg/scheduler/framework/types.go

@@ -549,7 +549,7 @@ func (n *NodeInfo) Clone() *NodeInfo {
 		Allocatable:      n.Allocatable.Clone(),
 		UsedPorts:        make(HostPortInfo),
 		ImageStates:      n.ImageStates,
-		PVCRefCounts:     n.PVCRefCounts,
+		PVCRefCounts:     make(map[string]int),
 		Generation:       n.Generation,
 	}
 	if len(n.Pods) > 0 {
@@ -571,6 +571,9 @@ func (n *NodeInfo) Clone() *NodeInfo {
 	if len(n.PodsWithRequiredAntiAffinity) > 0 {
 		clone.PodsWithRequiredAntiAffinity = append([]*PodInfo(nil), n.PodsWithRequiredAntiAffinity...)
 	}
+	for key, value := range n.PVCRefCounts {
+		clone.PVCRefCounts[key] = value
+	}
 	return clone
 }
 
@@ -770,7 +773,7 @@ func (n *NodeInfo) updatePVCRefCounts(pod *v1.Pod, add bool) {
 			continue
 		}
 
-		key := pod.Namespace + "/" + v.PersistentVolumeClaim.ClaimName
+		key := GetNamespacedName(pod.Namespace, v.PersistentVolumeClaim.ClaimName)
 		if add {
 			n.PVCRefCounts[key] += 1
 		} else {
@@ -838,6 +841,11 @@ func GetPodKey(pod *v1.Pod) (string, error) {
 	return uid, nil
 }
 
+// GetNamespacedName returns the string format of a namespaced resource name.
+func GetNamespacedName(namespace, name string) string {
+	return fmt.Sprintf("%s/%s", namespace, name)
+}
+
 // DefaultBindAllHostIP defines the default ip address used to bind to all host.
 const DefaultBindAllHostIP = "0.0.0.0"
 

pkg/scheduler/internal/cache/cache.go

@@ -191,7 +191,7 @@ func (cache *cacheImpl) Dump() *Dump {
 // UpdateSnapshot takes a snapshot of cached NodeInfo map. This is called at
 // beginning of every scheduling cycle.
 // The snapshot only includes Nodes that are not deleted at the time this function is called.
-// nodeinfo.Node() is guaranteed to be not nil for all the nodes in the snapshot.
+// nodeInfo.Node() is guaranteed to be not nil for all the nodes in the snapshot.
 // This function tracks generation number of NodeInfo and updates only the
 // entries of an existing snapshot that have changed after the snapshot was taken.
 func (cache *cacheImpl) UpdateSnapshot(nodeSnapshot *Snapshot) error {
@@ -212,6 +212,9 @@ func (cache *cacheImpl) UpdateSnapshot(nodeSnapshot *Snapshot) error {
 	// status from having pods with required anti-affinity to NOT having pods with required
 	// anti-affinity or the other way around.
 	updateNodesHavePodsWithRequiredAntiAffinity := false
+	// usedPVCSet must be re-created whenever the head node generation is greater than
+	// last snapshot generation.
+	updateUsedPVCSet := false
 
 	// Start from the head of the NodeInfo doubly linked list and update snapshot
 	// of NodeInfos updated after the last snapshot.
@@ -237,6 +240,18 @@ func (cache *cacheImpl) UpdateSnapshot(nodeSnapshot *Snapshot) error {
 			if (len(existing.PodsWithRequiredAntiAffinity) > 0) != (len(clone.PodsWithRequiredAntiAffinity) > 0) {
 				updateNodesHavePodsWithRequiredAntiAffinity = true
 			}
+			if !updateUsedPVCSet {
+				if len(existing.PVCRefCounts) != len(clone.PVCRefCounts) {
+					updateUsedPVCSet = true
+				} else {
+					for pvcKey := range clone.PVCRefCounts {
+						if _, found := existing.PVCRefCounts[pvcKey]; !found {
+							updateUsedPVCSet = true
+							break
+						}
+					}
+				}
+			}
 			// We need to preserve the original pointer of the NodeInfo struct since it
 			// is used in the NodeInfoList, which we may not update.
 			*existing = *clone
@@ -255,7 +270,7 @@ func (cache *cacheImpl) UpdateSnapshot(nodeSnapshot *Snapshot) error {
 		updateAllLists = true
 	}
 
-	if updateAllLists || updateNodesHavePodsWithAffinity || updateNodesHavePodsWithRequiredAntiAffinity {
+	if updateAllLists || updateNodesHavePodsWithAffinity || updateNodesHavePodsWithRequiredAntiAffinity || updateUsedPVCSet {
 		cache.updateNodeInfoSnapshotList(nodeSnapshot, updateAllLists)
 	}
 
@@ -278,6 +293,7 @@ func (cache *cacheImpl) UpdateSnapshot(nodeSnapshot *Snapshot) error {
 func (cache *cacheImpl) updateNodeInfoSnapshotList(snapshot *Snapshot, updateAll bool) {
 	snapshot.havePodsWithAffinityNodeInfoList = make([]*framework.NodeInfo, 0, cache.nodeTree.numNodes)
 	snapshot.havePodsWithRequiredAntiAffinityNodeInfoList = make([]*framework.NodeInfo, 0, cache.nodeTree.numNodes)
+	snapshot.usedPVCSet = sets.NewString()
 	if updateAll {
 		// Take a snapshot of the nodes order in the tree
 		snapshot.nodeInfoList = make([]*framework.NodeInfo, 0, cache.nodeTree.numNodes)
@@ -294,6 +310,9 @@ func (cache *cacheImpl) updateNodeInfoSnapshotList(snapshot *Snapshot, updateAll
 				if len(nodeInfo.PodsWithRequiredAntiAffinity) > 0 {
 					snapshot.havePodsWithRequiredAntiAffinityNodeInfoList = append(snapshot.havePodsWithRequiredAntiAffinityNodeInfoList, nodeInfo)
 				}
+				for key := range nodeInfo.PVCRefCounts {
+					snapshot.usedPVCSet.Insert(key)
+				}
 			} else {
 				klog.ErrorS(nil, "Node exists in nodeTree but not in NodeInfoMap, this should not happen", "node", klog.KRef("", nodeName))
 			}
@@ -306,6 +325,9 @@ func (cache *cacheImpl) updateNodeInfoSnapshotList(snapshot *Snapshot, updateAll
 			if len(nodeInfo.PodsWithRequiredAntiAffinity) > 0 {
 				snapshot.havePodsWithRequiredAntiAffinityNodeInfoList = append(snapshot.havePodsWithRequiredAntiAffinityNodeInfoList, nodeInfo)
 			}
+			for key := range nodeInfo.PVCRefCounts {
+				snapshot.usedPVCSet.Insert(key)
+			}
 		}
 	}
 }
@@ -366,7 +388,7 @@ func (cache *cacheImpl) FinishBinding(pod *v1.Pod) error {
 	return cache.finishBinding(pod, time.Now())
 }
 
-// finishBinding exists to make tests determinitistic by injecting now as an argument
+// finishBinding exists to make tests deterministic by injecting now as an argument
 func (cache *cacheImpl) finishBinding(pod *v1.Pod, now time.Time) error {
 	key, err := framework.GetPodKey(pod)
 	if err != nil {

pkg/scheduler/internal/cache/cache_test.go

@@ -24,10 +24,14 @@ import (
 	"testing"
 	"time"
 
+	st "k8s.io/kubernetes/pkg/scheduler/testing"
+
+	"github.com/google/go-cmp/cmp"
 	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/kubernetes/pkg/scheduler/framework"
 	schedutil "k8s.io/kubernetes/pkg/scheduler/util"
 )
@@ -1169,7 +1173,7 @@ func TestNodeOperators(t *testing.T) {
 
 func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 	// Create a few nodes to be used in tests.
-	nodes := []*v1.Node{}
+	var nodes []*v1.Node
 	for i := 0; i < 10; i++ {
 		node := &v1.Node{
 			ObjectMeta: metav1.ObjectMeta{
@@ -1185,7 +1189,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 		nodes = append(nodes, node)
 	}
 	// Create a few nodes as updated versions of the above nodes
-	updatedNodes := []*v1.Node{}
+	var updatedNodes []*v1.Node
 	for _, n := range nodes {
 		updatedNode := n.DeepCopy()
 		updatedNode.Status.Allocatable = v1.ResourceList{
@@ -1196,7 +1200,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 	}
 
 	// Create a few pods for tests.
-	pods := []*v1.Pod{}
+	var pods []*v1.Pod
 	for i := 0; i < 20; i++ {
 		pod := &v1.Pod{
 			ObjectMeta: metav1.ObjectMeta{
@@ -1212,7 +1216,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 	}
 
 	// Create a few pods as updated versions of the above pods.
-	updatedPods := []*v1.Pod{}
+	var updatedPods []*v1.Pod
 	for _, p := range pods {
 		updatedPod := p.DeepCopy()
 		priority := int32(1000)
@@ -1221,24 +1225,21 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 	}
 
 	// Add a couple of pods with affinity, on the first and seconds nodes.
-	podsWithAffinity := []*v1.Pod{}
+	var podsWithAffinity []*v1.Pod
 	for i := 0; i < 2; i++ {
-		pod := &v1.Pod{
+		pod := st.MakePod().Name(fmt.Sprintf("p-affinity-%v", i)).Namespace("test-ns").UID(fmt.Sprintf("puid-affinity-%v", i)).
-			ObjectMeta: metav1.ObjectMeta{
+			PodAffinityExists("foo", "", st.PodAffinityWithRequiredReq).Node(fmt.Sprintf("test-node%v", i)).Obj()
-				Name:      fmt.Sprintf("test-pod%v", i),
-				Namespace: "test-ns",
-				UID:       types.UID(fmt.Sprintf("test-puid%v", i)),
-			},
-			Spec: v1.PodSpec{
-				NodeName: fmt.Sprintf("test-node%v", i),
-				Affinity: &v1.Affinity{
-					PodAffinity: &v1.PodAffinity{},
-				},
-			},
-		}
 		podsWithAffinity = append(podsWithAffinity, pod)
 	}
 
+	// Add a few of pods with PVC
+	var podsWithPVC []*v1.Pod
+	for i := 0; i < 8; i++ {
+		pod := st.MakePod().Name(fmt.Sprintf("p-pvc-%v", i)).Namespace("test-ns").UID(fmt.Sprintf("puid-pvc-%v", i)).
+			PVC(fmt.Sprintf("test-pvc%v", i%4)).Node(fmt.Sprintf("test-node%v", i%2)).Obj()
+		podsWithPVC = append(podsWithPVC, pod)
+	}
+
 	var cache *cacheImpl
 	var snapshot *Snapshot
 	type operation = func(t *testing.T)
@@ -1274,6 +1275,13 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 			}
 		}
 	}
+	addPodWithPVC := func(i int) operation {
+		return func(t *testing.T) {
+			if err := cache.AddPod(podsWithPVC[i]); err != nil {
+				t.Error(err)
+			}
+		}
+	}
 	removePod := func(i int) operation {
 		return func(t *testing.T) {
 			if err := cache.RemovePod(pods[i]); err != nil {
@@ -1288,6 +1296,13 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 			}
 		}
 	}
+	removePodWithPVC := func(i int) operation {
+		return func(t *testing.T) {
+			if err := cache.RemovePod(podsWithPVC[i]); err != nil {
+				t.Error(err)
+			}
+		}
+	}
 	updatePod := func(i int) operation {
 		return func(t *testing.T) {
 			if err := cache.UpdatePod(pods[i], updatedPods[i]); err != nil {
@@ -1309,16 +1324,19 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 		operations                   []operation
 		expected                     []*v1.Node
 		expectedHavePodsWithAffinity int
+		expectedUsedPVCSet           sets.String
 	}{
 		{
 			name:               "Empty cache",
 			operations:         []operation{},
 			expected:           []*v1.Node{},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name:               "Single node",
 			operations:         []operation{addNode(1)},
 			expected:           []*v1.Node{nodes[1]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add node, remove it, add it again",
@@ -1326,6 +1344,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(1), updateSnapshot(), removeNode(1), addNode(1),
 			},
 			expected:           []*v1.Node{nodes[1]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add node and remove it in the same cycle, add it again",
@@ -1333,6 +1352,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(1), updateSnapshot(), addNode(2), removeNode(1),
 			},
 			expected:           []*v1.Node{nodes[2]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add a few nodes, and snapshot in the middle",
@@ -1341,6 +1361,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				updateSnapshot(), addNode(3),
 			},
 			expected:           []*v1.Node{nodes[3], nodes[2], nodes[1], nodes[0]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add a few nodes, and snapshot in the end",
@@ -1348,6 +1369,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(0), addNode(2), addNode(5), addNode(6),
 			},
 			expected:           []*v1.Node{nodes[6], nodes[5], nodes[2], nodes[0]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Update some nodes",
@@ -1355,6 +1377,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(0), addNode(1), addNode(5), updateSnapshot(), updateNode(1),
 			},
 			expected:           []*v1.Node{nodes[1], nodes[5], nodes[0]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add a few nodes, and remove all of them",
@@ -1363,6 +1386,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				removeNode(0), removeNode(2), removeNode(5), removeNode(6),
 			},
 			expected:           []*v1.Node{},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add a few nodes, and remove some of them",
@@ -1371,6 +1395,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				removeNode(0), removeNode(6),
 			},
 			expected:           []*v1.Node{nodes[5], nodes[2]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add a few nodes, remove all of them, and add more",
@@ -1380,6 +1405,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(7), addNode(9),
 			},
 			expected:           []*v1.Node{nodes[9], nodes[7]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Update nodes in particular order",
@@ -1388,6 +1414,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(1),
 			},
 			expected:           []*v1.Node{nodes[1], nodes[8], nodes[2]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add some nodes and some pods",
@@ -1396,6 +1423,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addPod(8), addPod(2),
 			},
 			expected:           []*v1.Node{nodes[2], nodes[8], nodes[0]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Updating a pod moves its node to the head",
@@ -1403,6 +1431,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(0), addPod(0), addNode(2), addNode(4), updatePod(0),
 			},
 			expected:           []*v1.Node{nodes[0], nodes[4], nodes[2]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add pod before its node",
@@ -1410,6 +1439,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				addNode(0), addPod(1), updatePod(1), addNode(1),
 			},
 			expected:           []*v1.Node{nodes[1], nodes[0]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Remove node before its pods",
@@ -1419,6 +1449,7 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				updatePod(1), updatePod(11), removePod(1), removePod(11),
 			},
 			expected:           []*v1.Node{nodes[0]},
+			expectedUsedPVCSet: sets.NewString(),
 		},
 		{
 			name: "Add Pods with affinity",
@@ -1427,6 +1458,15 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 			},
 			expected:                     []*v1.Node{nodes[1], nodes[0]},
 			expectedHavePodsWithAffinity: 1,
+			expectedUsedPVCSet:           sets.NewString(),
+		},
+		{
+			name: "Add Pods with PVC",
+			operations: []operation{
+				addNode(0), addPodWithPVC(0), updateSnapshot(), addNode(1),
+			},
+			expected:           []*v1.Node{nodes[1], nodes[0]},
+			expectedUsedPVCSet: sets.NewString("test-ns/test-pvc0"),
 		},
 		{
 			name: "Add multiple nodes with pods with affinity",
@@ -1435,6 +1475,15 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 			},
 			expected:                     []*v1.Node{nodes[1], nodes[0]},
 			expectedHavePodsWithAffinity: 2,
+			expectedUsedPVCSet:           sets.NewString(),
+		},
+		{
+			name: "Add multiple nodes with pods with PVC",
+			operations: []operation{
+				addNode(0), addPodWithPVC(0), updateSnapshot(), addNode(1), addPodWithPVC(1), updateSnapshot(),
+			},
+			expected:           []*v1.Node{nodes[1], nodes[0]},
+			expectedUsedPVCSet: sets.NewString("test-ns/test-pvc0", "test-ns/test-pvc1"),
 		},
 		{
 			name: "Add then Remove pods with affinity",
@@ -1443,6 +1492,43 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 			},
 			expected:                     []*v1.Node{nodes[0], nodes[1]},
 			expectedHavePodsWithAffinity: 0,
+			expectedUsedPVCSet:           sets.NewString(),
+		},
+		{
+			name: "Add then Remove pod with PVC",
+			operations: []operation{
+				addNode(0), addPodWithPVC(0), updateSnapshot(), removePodWithPVC(0), addPodWithPVC(2), updateSnapshot(),
+			},
+			expected:           []*v1.Node{nodes[0]},
+			expectedUsedPVCSet: sets.NewString("test-ns/test-pvc2"),
+		},
+		{
+			name: "Add then Remove pod with PVC and add same pod again",
+			operations: []operation{
+				addNode(0), addPodWithPVC(0), updateSnapshot(), removePodWithPVC(0), addPodWithPVC(0), updateSnapshot(),
+			},
+			expected:           []*v1.Node{nodes[0]},
+			expectedUsedPVCSet: sets.NewString("test-ns/test-pvc0"),
+		},
+		{
+			name: "Add and Remove multiple pods with PVC with same ref count length different content",
+			operations: []operation{
+				addNode(0), addNode(1), addPodWithPVC(0), addPodWithPVC(1), updateSnapshot(),
+				removePodWithPVC(0), removePodWithPVC(1), addPodWithPVC(2), addPodWithPVC(3), updateSnapshot(),
+			},
+			expected:           []*v1.Node{nodes[1], nodes[0]},
+			expectedUsedPVCSet: sets.NewString("test-ns/test-pvc2", "test-ns/test-pvc3"),
+		},
+		{
+			name: "Add and Remove multiple pods with PVC",
+			operations: []operation{
+				addNode(0), addNode(1), addPodWithPVC(0), addPodWithPVC(1), addPodWithPVC(2), updateSnapshot(),
+				removePodWithPVC(0), removePodWithPVC(1), updateSnapshot(), addPodWithPVC(0), updateSnapshot(),
+				addPodWithPVC(3), addPodWithPVC(4), addPodWithPVC(5), updateSnapshot(),
+				removePodWithPVC(0), removePodWithPVC(3), removePodWithPVC(4), updateSnapshot(),
+			},
+			expected:           []*v1.Node{nodes[0], nodes[1]},
+			expectedUsedPVCSet: sets.NewString("test-ns/test-pvc1", "test-ns/test-pvc2"),
 		},
 	}
 
@@ -1476,6 +1562,11 @@ func TestSchedulerCache_UpdateSnapshot(t *testing.T) {
 				t.Errorf("unexpected number of HavePodsWithAffinity nodes. Expected: %v, got: %v", test.expectedHavePodsWithAffinity, len(snapshot.havePodsWithAffinityNodeInfoList))
 			}
 
+			// Compare content of the used PVC set
+			if diff := cmp.Diff(test.expectedUsedPVCSet, snapshot.usedPVCSet); diff != "" {
+				t.Errorf("Unexpected usedPVCSet (-want +got):\n%s", diff)
+			}
+
 			// Always update the snapshot at the end of operations and compare it.
 			if err := cache.UpdateSnapshot(snapshot); err != nil {
 				t.Error(err)
@@ -1509,6 +1600,7 @@ func compareCacheWithNodeInfoSnapshot(t *testing.T, cache *cacheImpl, snapshot *
 
 	expectedNodeInfoList := make([]*framework.NodeInfo, 0, cache.nodeTree.numNodes)
 	expectedHavePodsWithAffinityNodeInfoList := make([]*framework.NodeInfo, 0, cache.nodeTree.numNodes)
+	expectedUsedPVCSet := sets.NewString()
 	nodesList, err := cache.nodeTree.list()
 	if err != nil {
 		t.Fatal(err)
@@ -1519,6 +1611,9 @@ func compareCacheWithNodeInfoSnapshot(t *testing.T, cache *cacheImpl, snapshot *
 			if len(n.PodsWithAffinity) > 0 {
 				expectedHavePodsWithAffinityNodeInfoList = append(expectedHavePodsWithAffinityNodeInfoList, n)
 			}
+			for key := range n.PVCRefCounts {
+				expectedUsedPVCSet.Insert(key)
+			}
 		} else {
 			return fmt.Errorf("node %q exist in nodeTree but not in NodeInfoMap, this should not happen", nodeName)
 		}
@@ -1538,12 +1633,18 @@ func compareCacheWithNodeInfoSnapshot(t *testing.T, cache *cacheImpl, snapshot *
 		}
 	}
 
+	for key := range expectedUsedPVCSet {
+		if !snapshot.usedPVCSet.Has(key) {
+			return fmt.Errorf("expected PVC %s to exist in UsedPVCSet but it is not found", key)
+		}
+	}
+
 	return nil
 }
 
 func TestSchedulerCache_updateNodeInfoSnapshotList(t *testing.T) {
 	// Create a few nodes to be used in tests.
-	nodes := []*v1.Node{}
+	var nodes []*v1.Node
 	i := 0
 	// List of number of nodes per zone, zone 0 -> 2, zone 1 -> 6
 	for zone, nb := range []int{2, 6} {

pkg/scheduler/internal/cache/snapshot.go

@@ -36,6 +36,9 @@ type Snapshot struct {
 	// havePodsWithRequiredAntiAffinityNodeInfoList is the list of nodes with at least one pod declaring
 	// required anti-affinity terms.
 	havePodsWithRequiredAntiAffinityNodeInfoList []*framework.NodeInfo
+	// usedPVCSet contains a set of PVC names that have one or more scheduled pods using them,
+	// keyed in the format "namespace/name".
+	usedPVCSet sets.String
 	generation int64
 }
 
@@ -45,6 +48,7 @@ var _ framework.SharedLister = &Snapshot{}
 func NewEmptySnapshot() *Snapshot {
 	return &Snapshot{
 		nodeInfoMap: make(map[string]*framework.NodeInfo),
+		usedPVCSet:  sets.NewString(),
 	}
 }
 
@@ -69,6 +73,7 @@ func NewSnapshot(pods []*v1.Pod, nodes []*v1.Node) *Snapshot {
 	s.nodeInfoList = nodeInfoList
 	s.havePodsWithAffinityNodeInfoList = havePodsWithAffinityNodeInfoList
 	s.havePodsWithRequiredAntiAffinityNodeInfoList = havePodsWithRequiredAntiAffinityNodeInfoList
+	s.usedPVCSet = createUsedPVCSet(pods)
 
 	return s
 }
@@ -98,6 +103,25 @@ func createNodeInfoMap(pods []*v1.Pod, nodes []*v1.Node) map[string]*framework.N
 	return nodeNameToInfo
 }
 
+func createUsedPVCSet(pods []*v1.Pod) sets.String {
+	usedPVCSet := sets.NewString()
+	for _, pod := range pods {
+		if pod.Spec.NodeName == "" {
+			continue
+		}
+
+		for _, v := range pod.Spec.Volumes {
+			if v.PersistentVolumeClaim == nil {
+				continue
+			}
+
+			key := framework.GetNamespacedName(pod.Namespace, v.PersistentVolumeClaim.ClaimName)
+			usedPVCSet.Insert(key)
+		}
+	}
+	return usedPVCSet
+}
+
 // getNodeImageStates returns the given node's image states based on the given imageExistence map.
 func getNodeImageStates(node *v1.Node, imageExistenceMap map[string]sets.String) map[string]*framework.ImageStateSummary {
 	imageStates := make(map[string]*framework.ImageStateSummary)
@@ -135,6 +159,11 @@ func (s *Snapshot) NodeInfos() framework.NodeInfoLister {
 	return s
 }
 
+// StorageInfos returns a StorageInfoLister.
+func (s *Snapshot) StorageInfos() framework.StorageInfoLister {
+	return s
+}
+
 // NumNodes returns the number of nodes in the snapshot.
 func (s *Snapshot) NumNodes() int {
 	return len(s.nodeInfoList)
@@ -163,3 +192,7 @@ func (s *Snapshot) Get(nodeName string) (*framework.NodeInfo, error) {
 	}
 	return nil, fmt.Errorf("nodeinfo not found for node name %q", nodeName)
 }
+
+func (s *Snapshot) IsPVCUsedByPods(key string) bool {
+	return s.usedPVCSet.Has(key)
+}

pkg/scheduler/internal/cache/snapshot_test.go

@@ -21,10 +21,12 @@ import (
 	"reflect"
 	"testing"
 
-	"k8s.io/api/core/v1"
+	"github.com/google/go-cmp/cmp"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/kubernetes/pkg/scheduler/framework"
+	st "k8s.io/kubernetes/pkg/scheduler/testing"
 )
 
 const mb int64 = 1024 * 1024
@@ -180,3 +182,50 @@ func TestCreateImageExistenceMap(t *testing.T) {
 		})
 	}
 }
+
+func TestCreateUsedPVCSet(t *testing.T) {
+	tests := []struct {
+		name     string
+		pods     []*v1.Pod
+		expected sets.String
+	}{
+		{
+			name:     "empty pods list",
+			pods:     []*v1.Pod{},
+			expected: sets.NewString(),
+		},
+		{
+			name: "pods not scheduled",
+			pods: []*v1.Pod{
+				st.MakePod().Name("foo").Namespace("foo").Obj(),
+				st.MakePod().Name("bar").Namespace("bar").Obj(),
+			},
+			expected: sets.NewString(),
+		},
+		{
+			name: "scheduled pods that do not use any PVC",
+			pods: []*v1.Pod{
+				st.MakePod().Name("foo").Namespace("foo").Node("node-1").Obj(),
+				st.MakePod().Name("bar").Namespace("bar").Node("node-2").Obj(),
+			},
+			expected: sets.NewString(),
+		},
+		{
+			name: "scheduled pods that use PVC",
+			pods: []*v1.Pod{
+				st.MakePod().Name("foo").Namespace("foo").Node("node-1").PVC("pvc1").Obj(),
+				st.MakePod().Name("bar").Namespace("bar").Node("node-2").PVC("pvc2").Obj(),
+			},
+			expected: sets.NewString("foo/pvc1", "bar/pvc2"),
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			usedPVCs := createUsedPVCSet(test.pods)
+			if diff := cmp.Diff(test.expected, usedPVCs); diff != "" {
+				t.Errorf("Unexpected usedPVCs (-want +got):\n%s", diff)
+			}
+		})
+	}
+}