mpage: convert map_buffer_to_folio() to folio_create_empty_buffers()

Saves a folio->page->folio conversion.

Link: https://lkml.kernel.org/r/20231016201114.1928083-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/mpage.c

@@ -119,8 +119,7 @@ static void map_buffer_to_folio(struct folio *folio, struct buffer_head *bh,
 			folio_mark_uptodate(folio);
 			return;
 		}
-		create_empty_buffers(&folio->page, i_blocksize(inode), 0);
-		head = folio_buffers(folio);
+		head = folio_create_empty_buffers(folio, i_blocksize(inode), 0);
 	}
 
 	page_bh = head;