mm, slab: use frozen pages for large kmalloc

Since slab pages are now frozen, it makes sense to have large kmalloc()
objects behave same as small kmalloc(), as the choice between the two is
an implementation detail depending on allocation size.

Notably, increasing refcount on a slab page containing kmalloc() object
is not possible anymore, so it should be consistent for large kmalloc
pages.

Therefore, change large kmalloc to use the frozen pages API.

Because of some unexpected fallout in the slab pages case (see commit
b9c0e49 ("mm: decline to manipulate the refcount on a slab page"),
implement the same kind of checks and warnings as part of this change.

Notably, networking code using sendpage_ok() to determine whether the
page refcount can be manipulated in the network stack should continue
behaving correctly. Before this change, the function returns true for
large kmalloc pages and page refcount can be manipulated. After this
change, the function will return false.

Acked-by: Roman Gushchin <[email protected]>
Acked-by: Harry Yoo <[email protected]>
Signed-off-by: Vlastimil Babka <[email protected]>

Author: tehcaster

include/linux/mm.h

@@ -1325,6 +1325,8 @@ static inline void get_page(struct page *page)
 	struct folio *folio = page_folio(page);
 	if (WARN_ON_ONCE(folio_test_slab(folio)))
 		return;
+	if (WARN_ON_ONCE(folio_test_large_kmalloc(folio)))
+		return;
 	folio_get(folio);
 }
 
@@ -1419,7 +1421,7 @@ static inline void put_page(struct page *page)
 {
 	struct folio *folio = page_folio(page);
 
-	if (folio_test_slab(folio))
+	if (folio_test_slab(folio) || folio_test_large_kmalloc(folio))
 		return;
 
 	folio_put(folio);

mm/slub.c

@@ -4271,9 +4271,9 @@ static void *___kmalloc_large_node(size_t size, gfp_t flags, int node)
 	flags |= __GFP_COMP;
 
 	if (node == NUMA_NO_NODE)
-		folio = (struct folio *)alloc_pages_noprof(flags, order);
+		folio = (struct folio *)alloc_frozen_pages_noprof(flags, order);
 	else
-		folio = (struct folio *)__alloc_pages_noprof(flags, order, node, NULL);
+		folio = (struct folio *)__alloc_frozen_pages_noprof(flags, order, node, NULL);
 
 	if (folio) {
 		ptr = folio_address(folio);
@@ -4770,7 +4770,7 @@ static void free_large_kmalloc(struct folio *folio, void *object)
 	lruvec_stat_mod_folio(folio, NR_SLAB_UNRECLAIMABLE_B,
 			      -(PAGE_SIZE << order));
 	__folio_clear_large_kmalloc(folio);
-	folio_put(folio);
+	free_frozen_pages(&folio->page, order);
 }
 
 /*