Make volumeCreate more consistent between all 3 implementations.

weed/storage/volume_create.go

@@ -8,7 +8,7 @@ import (
 	"github.com/chrislusf/seaweedfs/weed/glog"
 )
 
-func createVolumeFile(fileName string, preallocate int64, useMemoryMap uint32) (*os.File, error) {
+func createVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (*os.File, error) {
 	file, e := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
 	if preallocate > 0 {
 		glog.V(0).Infof("Preallocated disk space for %s is not supported", fileName)

weed/storage/volume_create_linux.go

@@ -9,8 +9,8 @@ import (
 	"github.com/chrislusf/seaweedfs/weed/glog"
 )
 
-func createVolumeFile(fileName string, preallocate int64, useMemoryMap uint32) (file *os.File, e error) {
-	file, e = os.OpenFile(fileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
+func createVolumeFile(fileName string, preallocate int64, memoryMapSizeMB uint32) (*os.File, error) {
+	file, e := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
 	if preallocate != 0 {
 		syscall.Fallocate(int(file.Fd()), 1, 0, preallocate)
 		glog.V(0).Infof("Preallocated %d bytes disk space for %s", preallocate, fileName)