memcg: convert get_obj_cgroup_from_page to get_obj_cgroup_from_folio

As the one caller now has a folio, pass it in and use it.  Removes three
calls to compound_head().

Link: https://lkml.kernel.org/r/20230715042343.434588-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/memcontrol.h

@@ -1759,7 +1759,7 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order);
 void __memcg_kmem_uncharge_page(struct page *page, int order);
 
 struct obj_cgroup *get_obj_cgroup_from_current(void);
-struct obj_cgroup *get_obj_cgroup_from_page(struct page *page);
+struct obj_cgroup *get_obj_cgroup_from_folio(struct folio *folio);
 
 int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size);
 void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size);
@@ -1843,7 +1843,7 @@ static inline void __memcg_kmem_uncharge_page(struct page *page, int order)
 {
 }
 
-static inline struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
+static inline struct obj_cgroup *get_obj_cgroup_from_folio(struct folio *folio)
 {
 	return NULL;
 }

mm/memcontrol.c

@@ -3036,21 +3036,21 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
 	return objcg;
 }
 
-struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
+struct obj_cgroup *get_obj_cgroup_from_folio(struct folio *folio)
 {
 	struct obj_cgroup *objcg;
 
 	if (!memcg_kmem_online())
 		return NULL;
 
-	if (PageMemcgKmem(page)) {
-		objcg = __folio_objcg(page_folio(page));
+	if (folio_memcg_kmem(folio)) {
+		objcg = __folio_objcg(folio);
 		obj_cgroup_get(objcg);
 	} else {
 		struct mem_cgroup *memcg;
 
 		rcu_read_lock();
-		memcg = __folio_memcg(page_folio(page));
+		memcg = __folio_memcg(folio);
 		if (memcg)
 			objcg = __get_obj_cgroup_from_memcg(memcg);
 		else

mm/zswap.c

@@ -1258,7 +1258,7 @@ bool zswap_store(struct folio *folio)
 	 * cgroup-aware entry LRU, we will push out entries system-wide based on
 	 * local cgroup limits.
 	 */
-	objcg = get_obj_cgroup_from_page(page);
+	objcg = get_obj_cgroup_from_folio(folio);
 	if (objcg && !obj_cgroup_may_zswap(objcg))
 		goto reject;