slab: Remove folio references in slab alloc/free

Use pages directly to further the split between slab and folio.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Link: https://patch.msgid.link/20251113000932.1589073-5-willy@infradead.org
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: Matthew Wilcox (Oracle)

mm/slub.c

@@ -3045,24 +3045,24 @@ static inline struct slab *alloc_slab_page(gfp_t flags, int node,
 					   struct kmem_cache_order_objects oo,
 					   bool allow_spin)
 {
-	struct folio *folio;
+	struct page *page;
 	struct slab *slab;
 	unsigned int order = oo_order(oo);
 
 	if (unlikely(!allow_spin))
-		folio = (struct folio *)alloc_frozen_pages_nolock(0/* __GFP_COMP is implied */,
+		page = alloc_frozen_pages_nolock(0/* __GFP_COMP is implied */,
 								  node, order);
 	else if (node == NUMA_NO_NODE)
-		folio = (struct folio *)alloc_frozen_pages(flags, order);
+		page = alloc_frozen_pages(flags, order);
 	else
-		folio = (struct folio *)__alloc_frozen_pages(flags, order, node, NULL);
+		page = __alloc_frozen_pages(flags, order, node, NULL);
 
-	if (!folio)
+	if (!page)
 		return NULL;
 
-	slab = folio_slab(folio);
-	__folio_set_slab(folio);
-	if (folio_is_pfmemalloc(folio))
+	__SetPageSlab(page);
+	slab = page_slab(page);
+	if (page_is_pfmemalloc(page))
 		slab_set_pfmemalloc(slab);
 
 	return slab;
@@ -3286,16 +3286,16 @@ static struct slab *new_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 static void __free_slab(struct kmem_cache *s, struct slab *slab)
 {
-	struct folio *folio = slab_folio(slab);
-	int order = folio_order(folio);
+	struct page *page = slab_page(slab);
+	int order = compound_order(page);
 	int pages = 1 << order;
 
 	__slab_clear_pfmemalloc(slab);
-	folio->mapping = NULL;
-	__folio_clear_slab(folio);
+	page->mapping = NULL;
+	__ClearPageSlab(page);
 	mm_account_reclaimed_pages(pages);
 	unaccount_slab(slab, order, s);
-	free_frozen_pages(&folio->page, order);
+	free_frozen_pages(page, order);
 }
 
 static void rcu_free_slab(struct rcu_head *h)