Refactor for Sync method (#3426)

weed/storage/backend/disk_file_darwin.go

@@ -0,0 +1,43 @@
+//go:build darwin
+// +build darwin
+
+package backend
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+const (
+	// Using default File.Sync function, same as fcntl(fd, F_FULLFSYNC)
+	DM_SYNC = 1
+
+	// Using syscall.Fsync function, for MacOS this is not safe but is very fast.
+	DM_FSYNC = 2
+
+	// Using fcntl with F_BARRIERFSYNC parameter, for more details please refer:
+	// https://developer.apple.com/documentation/xcode/reducing-disk-writes
+	DM_BFSYNC = 3
+
+	F_BARRIERFSYNC = 85
+)
+
+var (
+	// By default using F_BARRIERFSYNC
+	DarwinSyncMode = DM_BFSYNC
+)
+
+func (df *DiskFile) Sync() error {
+	switch DarwinSyncMode {
+	case DM_SYNC:
+		return df.File.Sync()
+	case DM_BFSYNC:
+		fd := df.File.Fd()
+		_, err := unix.FcntlInt(fd, F_BARRIERFSYNC, 0)
+		return err
+	default:
+		fd := df.File.Fd()
+		return syscall.Fsync(int(fd))
+	}
+}