slab: Remove folio references from __do_krealloc()

One slight tweak I made is to calculate 'ks' earlier, which means we
can reuse it in the warning rather than calculating the object size twice.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://patch.msgid.link/20251113000932.1589073-10-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

@@ -6932,16 +6932,16 @@ __do_krealloc(const void *p, size_t new_size, unsigned long align, gfp_t flags,
 	if (is_kfence_address(p)) {
 		ks = orig_size = kfence_ksize(p);
 	} else {
-		struct folio *folio;
+		struct page *page = virt_to_page(p);
+		struct slab *slab = page_slab(page);
 
-		folio = virt_to_folio(p);
-		if (unlikely(!folio_test_slab(folio))) {
+		if (!slab) {
 			/* Big kmalloc object */
-			WARN_ON(folio_size(folio) <= KMALLOC_MAX_CACHE_SIZE);
-			WARN_ON(p != folio_address(folio));
-			ks = folio_size(folio);
+			ks = page_size(page);
+			WARN_ON(ks <= KMALLOC_MAX_CACHE_SIZE);
+			WARN_ON(p != page_address(page));
 		} else {
-			s = folio_slab(folio)->slab_cache;
+			s = slab->slab_cache;
 			orig_size = get_orig_size(s, (void *)p);
 			ks = s->object_size;
 		}