mm/memcg, swap: tidy up cgroup v1 memsw swap helpers

The cgroup v1 swap helpers always operate on swap cache folios whose swap
entry is stable: the folio is locked and in the swap cache.  There is no
need to pass the swap entry or page count as separate parameters when they
can be derived from the folio itself.

Simplify the redundant parameters and add sanity checks to document the
required preconditions.

Also rename memcg1_swapout to __memcg1_swapout to indicate it requires
special calling context: the folio must be isolated and dying, and the
call must be made with interrupts disabled.

No functional change.

Link: https://lore.kernel.org/20260517-swap-table-p4-v5-6-88ae43e064c7@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Youngjun Park <youngjun.park@lge.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 8 insertions, 10 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index dc3fa687759b..7d08128de1fd 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1899,8 +1899,8 @@ static inline void mem_cgroup_exit_user_fault(void)
 	current->in_user_fault = 0;
 }
 
-void memcg1_swapout(struct folio *folio, swp_entry_t entry);
-void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages);
+void __memcg1_swapout(struct folio *folio);
+void memcg1_swapin(struct folio *folio);
 
 #else /* CONFIG_MEMCG_V1 */
 static inline
@@ -1929,11 +1929,11 @@ static inline void mem_cgroup_exit_user_fault(void)
 {
 }
 
-static inline void memcg1_swapout(struct folio *folio, swp_entry_t entry)
+static inline void __memcg1_swapout(struct folio *folio)
 {
 }
 
-static inline void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages)
+static inline void memcg1_swapin(struct folio *folio)
 {
 }
 
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 7a09df6977a5..f907d3df52d0 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -571,13 +571,12 @@ static inline void folio_throttle_swaprate(struct folio *folio, gfp_t gfp)
 #endif
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_SWAP)
-int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry);
-static inline int mem_cgroup_try_charge_swap(struct folio *folio,
-		swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct folio *folio);
+static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 {
 	if (mem_cgroup_disabled())
 		return 0;
-	return __mem_cgroup_try_charge_swap(folio, entry);
+	return __mem_cgroup_try_charge_swap(folio);
 }
 
 extern void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
@@ -591,8 +590,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p
 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
 extern bool mem_cgroup_swap_full(struct folio *folio);
 #else
-static inline int mem_cgroup_try_charge_swap(struct folio *folio,
-					     swp_entry_t entry)
+static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 {
 	return 0;
 }