[#825] policer: Do not drop required linking objects

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/core/object/address.go

@@ -1,6 +1,8 @@
 package object
 
 import (
+	"fmt"
+
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
 )
@@ -8,6 +10,11 @@ import (
 // AddressWithType groups object address with its FrostFS
 // object type.
 type AddressWithType struct {
-	Address oid.Address
+	Address         oid.Address
-	Type    objectSDK.Type
+	Type            objectSDK.Type
+	IsLinkingObject bool
+}
+
+func (v AddressWithType) String() string {
+	return fmt.Sprintf("address: %s, type: %s, is linking: %t", v.Address, v.Type, v.IsLinkingObject)
 }

pkg/local_object_storage/metabase/list.go

@@ -102,6 +102,7 @@ func (db *DB) ListWithCursor(ctx context.Context, prm ListPrm) (res ListRes, err
 func (db *DB) listWithCursor(tx *bbolt.Tx, result []objectcore.AddressWithType, count int, cursor *Cursor) ([]objectcore.AddressWithType, *Cursor, error) {
 	threshold := cursor == nil // threshold is a flag to ignore cursor
 	var bucketName []byte
+	var err error
 
 	c := tx.Cursor()
 	name, _ := c.First()
@@ -140,8 +141,11 @@ loop:
 		bkt := tx.Bucket(name)
 		if bkt != nil {
 			copy(rawAddr, cidRaw)
-			result, offset, cursor = selectNFromBucket(bkt, objType, graveyardBkt, garbageBkt, rawAddr, containerID,
+			result, offset, cursor, err = selectNFromBucket(bkt, objType, graveyardBkt, garbageBkt, rawAddr, containerID,
 				result, count, cursor, threshold)
+			if err != nil {
+				return nil, nil, err
+			}
 		}
 		bucketName = name
 		if len(result) >= count {
@@ -183,23 +187,23 @@ func selectNFromBucket(bkt *bbolt.Bucket, // main bucket
 	limit int, // stop listing at `limit` items in result
 	cursor *Cursor, // start from cursor object
 	threshold bool, // ignore cursor and start immediately
-) ([]objectcore.AddressWithType, []byte, *Cursor) {
+) ([]objectcore.AddressWithType, []byte, *Cursor, error) {
 	if cursor == nil {
 		cursor = new(Cursor)
 	}
 
 	count := len(to)
 	c := bkt.Cursor()
-	k, _ := c.First()
+	k, v := c.First()
 
 	offset := cursor.inBucketOffset
 
 	if !threshold {
 		c.Seek(offset)
-		k, _ = c.Next() // we are looking for objects _after_ the cursor
+		k, v = c.Next() // we are looking for objects _after_ the cursor
 	}
 
-	for ; k != nil; k, _ = c.Next() {
+	for ; k != nil; k, v = c.Next() {
 		if count >= limit {
 			break
 		}
@@ -214,14 +218,23 @@ func selectNFromBucket(bkt *bbolt.Bucket, // main bucket
 			continue
 		}
 
+		var isLinkingObj bool
+		if objType == objectSDK.TypeRegular {
+			var o objectSDK.Object
+			if err := o.Unmarshal(v); err != nil {
+				return nil, nil, nil, err
+			}
+			isLinkingObj = isLinkObject(&o)
+		}
+
 		var a oid.Address
 		a.SetContainer(cnt)
 		a.SetObject(obj)
-		to = append(to, objectcore.AddressWithType{Address: a, Type: objType})
+		to = append(to, objectcore.AddressWithType{Address: a, Type: objType, IsLinkingObject: isLinkingObj})
 		count++
 	}
 
-	return to, offset, cursor
+	return to, offset, cursor, nil
 }
 
 func parseContainerIDWithPrefix(containerID *cid.ID, name []byte) ([]byte, byte) {

pkg/services/policer/check.go

@@ -93,10 +93,10 @@ func (p *Policer) processNodes(ctx context.Context, requirements *placementRequi
 	// Number of copies that are stored on maintenance nodes.
 	var uncheckedCopies int
 
-	if typ == objectSDK.TypeLock || typ == objectSDK.TypeTombstone {
+	if typ == objectSDK.TypeLock || typ == objectSDK.TypeTombstone || addrWithType.IsLinkingObject {
-		// all nodes of a container must store the `LOCK` and `TOMBSTONE` objects
+		// all nodes of a container must store the `LOCK`, `TOMBSTONE` and linking objects
 		// for correct object removal protection:
-		//   - `LOCK` and `TOMBSTONE` objects are broadcast on their PUT requests;
+		//   - `LOCK`, `TOMBSTONE` and linking objects are broadcast on their PUT requests;
 		//   - `LOCK` object removal is a prohibited action in the GC.
 		shortage = uint32(len(nodes))
 	}