mm/swap: convert find_get_incore_page to use folios

Eliminates a use of FGP_HEAD and saves 35 bytes of text.

Link: https://lkml.kernel.org/r/20221019183332.2802139-3-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/swap_state.c

@@ -386,17 +386,14 @@ struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
 {
 	swp_entry_t swp;
 	struct swap_info_struct *si;
-	struct page *page = pagecache_get_page(mapping, index,
-						FGP_ENTRY | FGP_HEAD, 0);
+	struct folio *folio = __filemap_get_folio(mapping, index, FGP_ENTRY, 0);
 
-	if (!page)
-		return page;
-	if (!xa_is_value(page))
-		return find_subpage(page, index);
+	if (!xa_is_value(folio))
+		goto out;
 	if (!shmem_mapping(mapping))
 		return NULL;
 
-	swp = radix_to_swp_entry(page);
+	swp = radix_to_swp_entry(folio);
 	/* There might be swapin error entries in shmem mapping. */
 	if (non_swap_entry(swp))
 		return NULL;
@@ -404,9 +401,13 @@ struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
 	si = get_swap_device(swp);
 	if (!si)
 		return NULL;
-	page = find_get_page(swap_address_space(swp), swp_offset(swp));
+	index = swp_offset(swp);
+	folio = filemap_get_folio(swap_address_space(swp), index);
 	put_swap_device(si);
-	return page;
+out:
+	if (!folio)
+		return NULL;
+	return folio_file_page(folio, index);
 }
 
 struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,