f2fs: remove preflush for nobarrier case

This patch removes REQ_PREFLUSH in the nobarrier case.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -306,9 +306,9 @@ static void __f2fs_submit_merged_bio(struct f2fs_sb_info *sbi,
 	if (type >= META_FLUSH) {
 		io->fio.type = META_FLUSH;
 		io->fio.op = REQ_OP_WRITE;
-		io->fio.op_flags = REQ_PREFLUSH | REQ_META | REQ_PRIO;
+		io->fio.op_flags = REQ_META | REQ_PRIO;
 		if (!test_opt(sbi, NOBARRIER))
-			io->fio.op_flags |= REQ_FUA;
+			io->fio.op_flags |= REQ_PREFLUSH | REQ_FUA;
 	}
 	__submit_merged_bio(io);
 out: