f2fs: fix to recover data written by dio

If data are overwritten through dio, previous f2fs doesn't remain the fsync mark
due to no additional node writes.

Note that this patch should resolve the xfstests:311.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index cadd28f..9c80f35 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1048,6 +1048,9 @@
 	if (check_direct_IO(inode, rw, iov, offset, nr_segs))
 		return 0;
 
+	/* clear fsync mark to recover these blocks */
+	fsync_mark_clear(F2FS_SB(inode->i_sb), inode->i_ino);
+
 	return blockdev_direct_IO(rw, iocb, inode, iov, offset, nr_segs,
 							get_data_block);
 }