f2fs: fix to handle error path of f2fs_ra_meta_pages()

In f2fs_ra_meta_pages(), if f2fs_submit_page_bio() failed, we need to
unlock page, fix it.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -220,6 +220,7 @@ int f2fs_ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
 		.is_por = (type == META_POR),
 	};
 	struct blk_plug plug;
+	int err;
 
 	if (unlikely(type == META_POR))
 		fio.op_flags &= ~REQ_META;
@@ -263,8 +264,8 @@ int f2fs_ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
 		}
 
 		fio.page = page;
-		f2fs_submit_page_bio(&fio);
-		f2fs_put_page(page, 0);
+		err = f2fs_submit_page_bio(&fio);
+		f2fs_put_page(page, err ? 1 : 0);
 	}
 out:
 	blk_finish_plug(&plug);