mm: memcontrol: fix swap counter leak from offline cgroup

commit 73f839b addressed an issue regarding the swap counter leak
that occurred from an offline cgroup.  However, commit 89ce924
modified the parameter from @swap_memcg to @memcg (presumably this
alteration was introduced while resolving conflicts).  Fix this problem by
reverting this minor change.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 89ce924 ("mm: memcontrol: move memsw charge callbacks to v1")
Signed-off-by: Muchun Song <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Shakeel Butt <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Cc: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Muchun Song

mm/memcontrol-v1.c

@@ -620,7 +620,7 @@ void memcg1_swapout(struct folio *folio, swp_entry_t entry)
 		mem_cgroup_id_get_many(swap_memcg, nr_entries - 1);
 	mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);
 
-	swap_cgroup_record(folio, mem_cgroup_id(memcg), entry);
+	swap_cgroup_record(folio, mem_cgroup_id(swap_memcg), entry);
 
 	folio_unqueue_deferred_split(folio);
 	folio->memcg_data = 0;