mm: remove references to page->index in huge_memory.c

We already have folios in all these places; it's just a matter of using
them instead of the pages.

Link: https://lkml.kernel.org/r/20241005200121.3231142-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Matthew Wilcox (Oracle)

mm/huge_memory.c

@@ -3199,8 +3199,8 @@ static void __split_huge_page_tail(struct folio *folio, int tail,
 	/* ->mapping in first and second tail page is replaced by other uses */
 	VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
 			page_tail);
-	page_tail->mapping = head->mapping;
-	page_tail->index = head->index + tail;
+	new_folio->mapping = folio->mapping;
+	new_folio->index = folio->index + tail;
 
 	/*
 	 * page->private should not be set in tail pages. Fix up and warn once
@@ -3276,24 +3276,24 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	ClearPageHasHWPoisoned(head);
 
 	for (i = nr - new_nr; i >= new_nr; i -= new_nr) {
+		struct folio *tail;
 		__split_huge_page_tail(folio, i, lruvec, list, new_order);
+		tail = page_folio(head + i);
 		/* Some pages can be beyond EOF: drop them from page cache */
-		if (head[i].index >= end) {
-			struct folio *tail = page_folio(head + i);
-
+		if (tail->index >= end) {
 			if (shmem_mapping(folio->mapping))
 				nr_dropped++;
 			else if (folio_test_clear_dirty(tail))
 				folio_account_cleaned(tail,
 					inode_to_wb(folio->mapping->host));
 			__filemap_remove_folio(tail, NULL);
 			folio_put(tail);
-		} else if (!PageAnon(page)) {
-			__xa_store(&folio->mapping->i_pages, head[i].index,
-					head + i, 0);
+		} else if (!folio_test_anon(folio)) {
+			__xa_store(&folio->mapping->i_pages, tail->index,
+					tail, 0);
 		} else if (swap_cache) {
 			__xa_store(&swap_cache->i_pages, offset + i,
-					head + i, 0);
+					tail, 0);
 		}
 	}