Added knob to disable O_DIRECT

fdbrpc/AsyncFileEIO.actor.h

@@ -248,7 +248,7 @@ private:
 		if( flags & OPEN_READWRITE ) oflags |= O_RDWR;
 		if( flags & OPEN_ATOMIC_WRITE_AND_CREATE ) oflags |= O_TRUNC;
 #if defined(__linux__)
-		if ( flags & OPEN_UNBUFFERED ) oflags |= O_DIRECT;
+		if ( flags & OPEN_UNBUFFERED && !FLOW_KNOBS->DISABLE_ODIRECT ) oflags |= O_DIRECT;
 #endif
 		return oflags;
 	}

fdbrpc/Net2FileSystem.cpp

@@ -63,7 +63,7 @@ Future< Reference<class IAsyncFile> > Net2FileSystem::open( std::string filename
 	// cases, DISABLE_POSIX_KERNEL_AIO knob can be enabled to fallback to EIO instead
 	// of Kernel AIO.
 	if ((flags & IAsyncFile::OPEN_UNBUFFERED) && !(flags & IAsyncFile::OPEN_NO_AIO) &&
-	    !FLOW_KNOBS->DISABLE_POSIX_KERNEL_AIO)
+	    !FLOW_KNOBS->DISABLE_POSIX_KERNEL_AIO && !FLOW_KNOBS->DISABLE_ODIRECT)
 		f = AsyncFileKAIO::open(filename, flags, mode, NULL);
 	else
 #endif

flow/Knobs.cpp

@@ -87,6 +87,7 @@ FlowKnobs::FlowKnobs(bool randomize, bool isSimulated) {
 
 	//AsyncFileEIO
 	init( EIO_MAX_PARALLELISM,                                  4  );
+	init( DISABLE_ODIRECT,                                      0 );
 
 	//AsyncFileKAIO
 	init( MAX_OUTSTANDING,                                      64 );

flow/Knobs.h

@@ -107,6 +107,7 @@ public:
 
 	//AsyncFileEIO
 	int EIO_MAX_PARALLELISM;
+	int DISABLE_ODIRECT;
 
 	//AsyncFileKAIO
 	int MAX_OUTSTANDING;