Properly check for fdatasync()

CMakeLists.txt

@@ -93,6 +93,12 @@ check_cxx_source_compiles ("#include <sys/types.h>
   " XATTR_ADD_OPT)
 set (CMAKE_REQUIRED_QUIET ${CMAKE_REQUIRED_QUIET_SAVE})
 
+# Check if we have fdatasync.
+include (CheckCXXSourceCompiles)
+check_cxx_source_compiles ("#include <unistd.h>
+  int main() { fdatasync(0); return 1; }
+  " FDATASYNC)
+
 # Check if we have some standard functions.
 include (CheckFuncs)
 check_function_exists_glibc (lchmod HAVE_LCHMOD)

encfs/FileNode.cpp

@@ -236,15 +236,13 @@ int FileNode::sync(bool datasync) {
   int fh = io->open(O_RDONLY);
   if (fh >= 0) {
     int res = -EIO;
-#ifdef linux
+#ifdef FDATASYNC
     if (datasync)
       res = fdatasync(fh);
     else
       res = fsync(fh);
 #else
     (void)datasync;
-    // no fdatasync support
-    // TODO: use autoconfig to check for it..
     res = fsync(fh);
 #endif
 

encfs/RawFileIO.cpp

@@ -270,11 +270,13 @@ int RawFileIO::truncate(off_t size) {
     knownSize = true;
   }
 
-#if !defined(__FreeBSD__) && !defined(__APPLE__)
   if (fd >= 0 && canWrite) {
+#ifdef FDATASYNC
     ::fdatasync(fd);
-  }
+#else
+    ::fsync(fd);
 #endif
+  }
 
   return res;
 }