erofs: introduce `z_erofs_parse_out_bvecs()'

`z_erofs_decompress_pcluster()' is too long therefore it'd be better
to introduce another helper to parse decompressed pages (or laterly,
decompressed bvecs.)

BTW, since `decompressed_bvecs' is too long as a part of the function
name, `out_bvecs' is used instead.
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Acked-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220715154203.48093-4-hsiangkao@linux.alibaba.com

fs/erofs/zdata.c

@@ -778,18 +778,58 @@ static bool z_erofs_page_is_invalidated(struct page *page)
 	return !page->mapping && !z_erofs_is_shortlived_page(page);
 }
 
+static int z_erofs_parse_out_bvecs(struct z_erofs_pcluster *pcl,
+				   struct page **pages, struct page **pagepool)
+{
+	struct z_erofs_pagevec_ctor ctor;
+	enum z_erofs_page_type page_type;
+	int i, err = 0;
+
+	z_erofs_pagevec_ctor_init(&ctor, Z_EROFS_NR_INLINE_PAGEVECS,
+				  pcl->pagevec, 0);
+	for (i = 0; i < pcl->vcnt; ++i) {
+		struct page *page = z_erofs_pagevec_dequeue(&ctor, &page_type);
+		unsigned int pagenr;
+
+		/* all pages in pagevec ought to be valid */
+		DBG_BUGON(!page);
+		DBG_BUGON(z_erofs_page_is_invalidated(page));
+
+		if (z_erofs_put_shortlivedpage(pagepool, page))
+			continue;
+
+		if (page_type == Z_EROFS_VLE_PAGE_TYPE_HEAD)
+			pagenr = 0;
+		else
+			pagenr = z_erofs_onlinepage_index(page);
+
+		DBG_BUGON(pagenr >= pcl->nr_pages);
+		/*
+		 * currently EROFS doesn't support multiref(dedup),
+		 * so here erroring out one multiref page.
+		 */
+		if (pages[pagenr]) {
+			DBG_BUGON(1);
+			SetPageError(pages[pagenr]);
+			z_erofs_onlinepage_endio(pages[pagenr]);
+			err = -EFSCORRUPTED;
+		}
+		pages[pagenr] = page;
+	}
+	z_erofs_pagevec_ctor_exit(&ctor, true);
+	return err;
+}
+
 static int z_erofs_decompress_pcluster(struct super_block *sb,
 				       struct z_erofs_pcluster *pcl,
 				       struct page **pagepool)
 {
 	struct erofs_sb_info *const sbi = EROFS_SB(sb);
 	unsigned int pclusterpages = z_erofs_pclusterpages(pcl);
-	struct z_erofs_pagevec_ctor ctor;
 	unsigned int i, inputsize, outputsize, llen, nr_pages;
 	struct page *pages_onstack[Z_EROFS_VMAP_ONSTACK_PAGES];
 	struct page **pages, **compressed_pages, *page;
 
-	enum z_erofs_page_type page_type;
 	bool overlapped, partial;
 	int err;
 
@@ -823,42 +863,7 @@ static int z_erofs_decompress_pcluster(struct super_block *sb,
 	for (i = 0; i < nr_pages; ++i)
 		pages[i] = NULL;
 
-	err = 0;
-	z_erofs_pagevec_ctor_init(&ctor, Z_EROFS_NR_INLINE_PAGEVECS,
-				  pcl->pagevec, 0);
-
-	for (i = 0; i < pcl->vcnt; ++i) {
-		unsigned int pagenr;
-
-		page = z_erofs_pagevec_dequeue(&ctor, &page_type);
-
-		/* all pages in pagevec ought to be valid */
-		DBG_BUGON(!page);
-		DBG_BUGON(z_erofs_page_is_invalidated(page));
-
-		if (z_erofs_put_shortlivedpage(pagepool, page))
-			continue;
-
-		if (page_type == Z_EROFS_VLE_PAGE_TYPE_HEAD)
-			pagenr = 0;
-		else
-			pagenr = z_erofs_onlinepage_index(page);
-
-		DBG_BUGON(pagenr >= nr_pages);
-
-		/*
-		 * currently EROFS doesn't support multiref(dedup),
-		 * so here erroring out one multiref page.
-		 */
-		if (pages[pagenr]) {
-			DBG_BUGON(1);
-			SetPageError(pages[pagenr]);
-			z_erofs_onlinepage_endio(pages[pagenr]);
-			err = -EFSCORRUPTED;
-		}
-		pages[pagenr] = page;
-	}
-	z_erofs_pagevec_ctor_exit(&ctor, true);
+	err = z_erofs_parse_out_bvecs(pcl, pages, pagepool);
 
 	overlapped = false;
 	compressed_pages = pcl->compressed_pages;