mm/swap: convert add_to_swap_cache() to take a folio

With all callers using folios, we can convert add_to_swap_cache() to take
a folio and use it throughout.

Link: https://lkml.kernel.org/r/20220902194653.1739778-13-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/shmem.c

@@ -1406,7 +1406,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	if (list_empty(&info->swaplist))
 		list_add(&info->swaplist, &shmem_swaplist);
 
-	if (add_to_swap_cache(&folio->page, swap,
+	if (add_to_swap_cache(folio, swap,
 			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
 			NULL) == 0) {
 		spin_lock_irq(&info->lock);

mm/swap.h

@@ -32,7 +32,7 @@ extern struct address_space *swapper_spaces[];
 void show_swap_cache_info(void);
 bool add_to_swap(struct folio *folio);
 void *get_shadow_from_swap_cache(swp_entry_t entry);
-int add_to_swap_cache(struct page *page, swp_entry_t entry,
+int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
 		      gfp_t gfp, void **shadowp);
 void __delete_from_swap_cache(struct folio *folio,
 			      swp_entry_t entry, void *shadow);
@@ -122,7 +122,7 @@ static inline void *get_shadow_from_swap_cache(swp_entry_t entry)
 	return NULL;
 }
 
-static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
+static inline int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
 					gfp_t gfp_mask, void **shadowp)
 {
 	return -1;

mm/swap_state.c

@@ -85,21 +85,21 @@ void *get_shadow_from_swap_cache(swp_entry_t entry)
  * add_to_swap_cache resembles filemap_add_folio on swapper_space,
  * but sets SwapCache flag and private instead of mapping and index.
  */
-int add_to_swap_cache(struct page *page, swp_entry_t entry,
+int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
 			gfp_t gfp, void **shadowp)
 {
 	struct address_space *address_space = swap_address_space(entry);
 	pgoff_t idx = swp_offset(entry);
-	XA_STATE_ORDER(xas, &address_space->i_pages, idx, compound_order(page));
-	unsigned long i, nr = thp_nr_pages(page);
+	XA_STATE_ORDER(xas, &address_space->i_pages, idx, folio_order(folio));
+	unsigned long i, nr = folio_nr_pages(folio);
 	void *old;
 
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	VM_BUG_ON_PAGE(PageSwapCache(page), page);
-	VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
+	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+	VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
+	VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
 
-	page_ref_add(page, nr);
-	SetPageSwapCache(page);
+	folio_ref_add(folio, nr);
+	folio_set_swapcache(folio);
 
 	do {
 		xas_lock_irq(&xas);
@@ -107,19 +107,19 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry,
 		if (xas_error(&xas))
 			goto unlock;
 		for (i = 0; i < nr; i++) {
-			VM_BUG_ON_PAGE(xas.xa_index != idx + i, page);
+			VM_BUG_ON_FOLIO(xas.xa_index != idx + i, folio);
 			old = xas_load(&xas);
 			if (xa_is_value(old)) {
 				if (shadowp)
 					*shadowp = old;
 			}
-			set_page_private(page + i, entry.val + i);
-			xas_store(&xas, page);
+			set_page_private(folio_page(folio, i), entry.val + i);
+			xas_store(&xas, folio);
 			xas_next(&xas);
 		}
 		address_space->nrpages += nr;
-		__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
-		__mod_lruvec_page_state(page, NR_SWAPCACHE, nr);
+		__node_stat_mod_folio(folio, NR_FILE_PAGES, nr);
+		__lruvec_stat_mod_folio(folio, NR_SWAPCACHE, nr);
 unlock:
 		xas_unlock_irq(&xas);
 	} while (xas_nomem(&xas, gfp));
@@ -127,8 +127,8 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry,
 	if (!xas_error(&xas))
 		return 0;
 
-	ClearPageSwapCache(page);
-	page_ref_sub(page, nr);
+	folio_clear_swapcache(folio);
+	folio_ref_sub(folio, nr);
 	return xas_error(&xas);
 }
 
@@ -194,7 +194,7 @@ bool add_to_swap(struct folio *folio)
 	/*
 	 * Add it to the swap cache.
 	 */
-	err = add_to_swap_cache(&folio->page, entry,
+	err = add_to_swap_cache(folio, entry,
 			__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
 	if (err)
 		/*
@@ -484,7 +484,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 		goto fail_unlock;
 
 	/* May fail (-ENOMEM) if XArray node allocation failed. */
-	if (add_to_swap_cache(&folio->page, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
+	if (add_to_swap_cache(folio, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
 		goto fail_unlock;
 
 	mem_cgroup_swapin_uncharge_swap(entry);