factor in existing ec volume count when estimating max volume count

related to https://github.com/seaweedfs/seaweedfs/issues/5191

weed/storage/disk_location_ec.go

@@ -218,9 +218,13 @@ func (l *DiskLocation) unmountEcVolumeByCollection(collectionName string) map[ne
 	return deltaVols
 }
 
-func (l *DiskLocation) EcVolumesLen() int {
+func (l *DiskLocation) EcShardCount() int {
 	l.ecVolumesLock.RLock()
 	defer l.ecVolumesLock.RUnlock()
 
-	return len(l.ecVolumes)
+	shardCount := 0
+	for _, ecVolume := range l.ecVolumes {
+		shardCount += len(ecVolume.Shards)
+	}
+	return shardCount
 }

weed/storage/store.go

@@ -149,7 +149,7 @@ func (s *Store) FindFreeLocation(diskType DiskType) (ret *DiskLocation) {
 		}
 		currentFreeCount := location.MaxVolumeCount - int32(location.VolumesLen())
 		currentFreeCount *= erasure_coding.DataShardsCount
-		currentFreeCount -= int32(location.EcVolumesLen())
+		currentFreeCount -= int32(location.EcShardCount())
 		currentFreeCount /= erasure_coding.DataShardsCount
 		if currentFreeCount > max {
 			max = currentFreeCount