mm/memcg, swap: store cgroup id in cluster table directly

Drop the usage of the swap_cgroup_ctrl, and use the dynamic cluster table
instead.

The per-cluster memcg table is 1024 / 512 bytes on most archs, and does
not need RCU protection: the cgroup data is only read and written under
the cluster lock.  That keeps things simple, lets the allocation use plain
kmalloc with immediate kfree (no deferred free), and keeps fragmentation
acceptable.

[akpm@linux-foundation.org: memcgv1: don't compile swap functions when CONFIG_SWAP=n]
  Link: https://lore.kernel.org/202605281711.bSeZlErK-lkp@intel.com
[akpm@linux-foundation.org: fix CONFIG_SWAP=n build]
Link: https://lore.kernel.org/20260517-swap-table-p4-v5-10-88ae43e064c7@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, 17 insertions, 10 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a013f37f24aa..8f2662db166b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -29,6 +29,7 @@ struct obj_cgroup;
 struct page;
 struct mm_struct;
 struct kmem_cache;
+struct swap_cluster_info;
 
 /* Cgroup-specific page state, on top of universal node page state */
 enum memcg_stat_item {
@@ -1899,9 +1900,6 @@ static inline void mem_cgroup_exit_user_fault(void)
 	current->in_user_fault = 0;
 }
 
-void __memcg1_swapout(struct folio *folio);
-void memcg1_swapin(struct folio *folio);
-
 #else /* CONFIG_MEMCG_V1 */
 static inline
 unsigned long memcg1_soft_limit_reclaim(pg_data_t *pgdat, int order,
@@ -1929,14 +1927,23 @@ static inline void mem_cgroup_exit_user_fault(void)
 {
 }
 
-static inline void __memcg1_swapout(struct folio *folio)
+#endif /* CONFIG_MEMCG_V1 */
+
+#if defined(CONFIG_MEMCG_V1) && defined(CONFIG_SWAP)
+
+void __memcg1_swapout(struct folio *folio, struct swap_cluster_info *ci);
+void memcg1_swapin(struct folio *folio);
+
+#else
+
+static inline void __memcg1_swapout(struct folio *folio,
+		struct swap_cluster_info *ci)
 {
 }
 
 static inline void memcg1_swapin(struct folio *folio)
 {
 }
-
-#endif /* CONFIG_MEMCG_V1 */
+#endif
 
 #endif /* _LINUX_MEMCONTROL_H */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index f907d3df52d0..200e7c345f26 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -579,12 +579,12 @@ static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 	return __mem_cgroup_try_charge_swap(folio);
 }
 
-extern void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
-static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
+extern void __mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages);
+static inline void mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_pages)
 {
 	if (mem_cgroup_disabled())
 		return;
-	__mem_cgroup_uncharge_swap(entry, nr_pages);
+	__mem_cgroup_uncharge_swap(id, nr_pages);
 }
 
 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
@@ -595,7 +595,7 @@ static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 	return 0;
 }
 
-static inline void mem_cgroup_uncharge_swap(swp_entry_t entry,
+static inline void mem_cgroup_uncharge_swap(unsigned short id,
 					    unsigned int nr_pages)
 {
 }