mm: convert do_swap_page() to use swap_cache_get_folio()

Saves a folio->page->folio conversion.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

mm/memory.c

···
 	if (unlikely(!si))
 		goto out;
 
-	page = lookup_swap_cache(entry, vma, vmf->address);
-	if (page)
-		folio = page_folio(page);
+	folio = swap_cache_get_folio(entry, vma, vmf->address);
+	if (folio)
+		page = folio_file_page(folio, swp_offset(entry));
 	swapcache = folio;
 
 	if (!folio) {