slab: Remove folio references from build_detached_freelist()

Use pages and slabs directly instead of converting to folios.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://patch.msgid.link/20251113000932.1589073-11-willy@infradead.org
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: Matthew Wilcox (Oracle)

mm/slub.c

@@ -7245,23 +7245,25 @@ int build_detached_freelist(struct kmem_cache *s, size_t size,
 {
 	int lookahead = 3;
 	void *object;
-	struct folio *folio;
+	struct page *page;
+	struct slab *slab;
 	size_t same;
 
 	object = p[--size];
-	folio = virt_to_folio(object);
+	page = virt_to_page(object);
+	slab = page_slab(page);
 	if (!s) {
 		/* Handle kalloc'ed objects */
-		if (unlikely(!folio_test_slab(folio))) {
-			free_large_kmalloc(&folio->page, object);
+		if (!slab) {
+			free_large_kmalloc(page, object);
 			df->slab = NULL;
 			return size;
 		}
 		/* Derive kmem_cache from object */
-		df->slab = folio_slab(folio);
-		df->s = df->slab->slab_cache;
+		df->slab = slab;
+		df->s = slab->slab_cache;
 	} else {
-		df->slab = folio_slab(folio);
+		df->slab = slab;
 		df->s = cache_from_obj(s, object); /* Support for memcg */
 	}