Changed the InMemory bool to a uint32 so that it can be used to alter how much space to reserve

weed/storage/needle/volume_memory_map_max_size.go

@@ -0,0 +1,14 @@
+package needle
+
+import "strconv"
+
+func ReadMemoryMapMaxSizeMB(MemoryMapMaxSizeMBString string) (uint32, error) {
+	if MemoryMapMaxSizeMBString == "" {
+		return 0, nil
+	}
+	var MemoryMapMaxSize64 uint64
+	var err error
+	MemoryMapMaxSize64, err = strconv.ParseUint(MemoryMapMaxSizeMBString, 10, 32)
+	MemoryMapMaxSize := uint32(MemoryMapMaxSize64)
+	return MemoryMapMaxSize, err
+}

weed/storage/needle/volume_memory_map_max_size_test.go

@@ -0,0 +1,10 @@
+package needle
+
+import "testing"
+
+func TestMemoryMapMaxSizeReadWrite(t *testing.T) {
+	memoryMapSize, _ := ReadMemoryMapMaxSizeMB("5000")
+	if memoryMapSize != 5000 {
+		t.Errorf("empty memoryMapSize:%v", memoryMapSize)
+	}
+}