Async flush uasserts on windows SERVER-735

Author: RedBeard0531

util/mmap_win.cpp

@@ -100,21 +100,20 @@ namespace mongo {
     }
 
     void MemoryMappedFile::flush(bool sync) {
+        uassert(13056, "Async flushing not supported on windows", sync);
+
         if (!view) return;
 
-        // Note: this is blocking and ignores sync
         bool success = FlushViewOfFile(view, 0); // 0 means whole mapping
         if (!success){
             int err = GetLastError();
-            out() << "FlushViewOfFile failed " << err << " " << endl;
+            out() << "FlushViewOfFile failed " << err << endl;
         }
 
-        if (sync){
-            bool success = FlushFileBuffers(fd);
-            if (!success){
-                int err = GetLastError();
-                out() << "FlushFileBuffers failed " << err << " " << endl;
-            }
+        success = FlushFileBuffers(fd);
+        if (!success){
+            int err = GetLastError();
+            out() << "FlushFileBuffers failed " << err << endl;
         }
     }
 }