f2fs: allow dio read for LFS mode

We can allow dio reads for LFS mode, while doing buffered writes for dio writes.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1732,7 +1732,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 
 	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
 		return 0;
-	if (test_opt(F2FS_I_SB(inode), LFS))
+	if (rw == WRITE && test_opt(F2FS_I_SB(inode), LFS))
 		return 0;
 
 	trace_f2fs_direct_IO_enter(inode, offset, count, rw);