f2fs: fix to avoid accessing invalid fio in f2fs_allocate_data_block()

Callers may pass fio parameter with NULL value to f2fs_allocate_data_block(),
so we should make sure accessing fio's field after fio's validation check.

Fixes: f608c38c ("f2fs: clean up parameter of f2fs_allocate_data_block()")
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -3417,12 +3417,12 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
 		f2fs_inode_chksum_set(sbi, page);
 	}
 
-	if (F2FS_IO_ALIGNED(sbi))
-		fio->retry = false;
-
 	if (fio) {
 		struct f2fs_bio_info *io;
 
+		if (F2FS_IO_ALIGNED(sbi))
+			fio->retry = false;
+
 		INIT_LIST_HEAD(&fio->list);
 		fio->in_list = true;
 		io = sbi->write_io[fio->type] + fio->temp;