[#1175] metabase: Update locker list during Inhume

`Inhume` operation can potentially mark lockers as garbage. There is a
need to update locker list in locked bucket.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/local_object_storage/metabase/inhume.go

@@ -148,6 +148,13 @@ func (db *DB) Inhume(prm *InhumePrm) (res *InhumeRes, err error) {
 				if targetIsTomb {
 					continue
 				}
+			} else {
+				// garbage object can probably lock some objects, so they should become
+				// unlocked after its decay
+				err = freePotentialLocks(tx, *prm.target[i].ContainerID(), *prm.target[i].ObjectID())
+				if err != nil {
+					return fmt.Errorf("free potential locks: %w", err)
+				}
 			}
 
 			// consider checking if target is already in graveyard?

pkg/local_object_storage/metabase/lock.go

@@ -103,3 +103,56 @@ func objectLocked(tx *bbolt.Tx, idCnr cid.ID, idObj oid.ID) bool {
 
 	return false
 }
+
+// releases all records about the objects locked by the locker.
+//
+// Operation is very resource-intensive, which is caused by the admissibility
+// of multiple locks. Also, if we knew what objects are locked, it would be
+// possible to speed up the execution.
+func freePotentialLocks(tx *bbolt.Tx, idCnr cid.ID, locker oid.ID) error {
+	bucketLocked := tx.Bucket(bucketNameLocked)
+	if bucketLocked != nil {
+		bucketLockedContainer := bucketLocked.Bucket([]byte(idCnr.String()))
+		if bucketLockedContainer != nil {
+			keyLocker := objectKey(&locker)
+			return bucketLockedContainer.ForEach(func(k, v []byte) error {
+				keyLockers, err := decodeList(v)
+				if err != nil {
+					return fmt.Errorf("decode list of lockers in locked bucket: %w", err)
+				}
+
+				for i := range keyLockers {
+					if bytes.Equal(keyLockers[i], keyLocker) {
+						if len(keyLockers) == 1 {
+							// locker was all alone
+							err = bucketLockedContainer.Delete(k)
+							if err != nil {
+								return fmt.Errorf("delete locked object record from locked bucket: %w", err)
+							}
+						} else {
+							// exclude locker
+							keyLockers = append(keyLockers[:i], keyLockers[i+1:]...)
+
+							v, err = encodeList(append(keyLockers[:i], keyLockers[i+1:]...))
+							if err != nil {
+								return fmt.Errorf("encode updated list of lockers: %w", err)
+							}
+
+							// update the record
+							err = bucketLockedContainer.Put(k, v)
+							if err != nil {
+								return fmt.Errorf("update list of lockers: %w", err)
+							}
+						}
+
+						return nil
+					}
+				}
+
+				return nil
+			})
+		}
+	}
+
+	return nil
+}