slab: Remove folio references from kfree_nolock()

In preparation for splitting struct slab from struct page and struct
folio, remove mentions of struct folio from this function.  Since large
kmalloc objects are not supported here, we can just use virt_to_slab().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://patch.msgid.link/20251113000932.1589073-13-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

@@ -6850,21 +6850,19 @@ EXPORT_SYMBOL(kfree);
  */
 void kfree_nolock(const void *object)
 {
-	struct folio *folio;
 	struct slab *slab;
 	struct kmem_cache *s;
 	void *x = (void *)object;
 
 	if (unlikely(ZERO_OR_NULL_PTR(object)))
 		return;
 
-	folio = virt_to_folio(object);
-	if (unlikely(!folio_test_slab(folio))) {
+	slab = virt_to_slab(object);
+	if (unlikely(!slab)) {
 		WARN_ONCE(1, "large_kmalloc is not supported by kfree_nolock()");
 		return;
 	}
 
-	slab = folio_slab(folio);
 	s = slab->slab_cache;
 
 	memcg_slab_free_hook(s, slab, &x, 1);