mm: memcontrol: use do_memsw_account() in a few more places

It's slightly more descriptive and consistent with other places that
distinguish cgroup1's combined memory+swap accounting scheme from
cgroup2's dedicated swap accounting.

Link: https://lkml.kernel.org/r/20220926135704.400818-4-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeelb@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcontrol.c

@@ -1667,17 +1667,17 @@ unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg)
 {
 	unsigned long max = READ_ONCE(memcg->memory.max);
 
-	if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
-		if (mem_cgroup_swappiness(memcg))
-			max += min(READ_ONCE(memcg->swap.max),
-				   (unsigned long)total_swap_pages);
-	} else { /* v1 */
+	if (do_memsw_account()) {
 		if (mem_cgroup_swappiness(memcg)) {
 			/* Calculate swap excess capacity from memsw limit */
 			unsigned long swap = READ_ONCE(memcg->memsw.max) - max;
 
 			max += min(swap, (unsigned long)total_swap_pages);
 		}
+	} else {
+		if (mem_cgroup_swappiness(memcg))
+			max += min(READ_ONCE(memcg->swap.max),
+				   (unsigned long)total_swap_pages);
 	}
 	return max;
 }
@@ -7334,7 +7334,7 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 	if (mem_cgroup_disabled())
 		return;
 
-	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
+	if (!do_memsw_account())
 		return;
 
 	memcg = folio_memcg(folio);
@@ -7399,7 +7399,7 @@ int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
 	struct mem_cgroup *memcg;
 	unsigned short oldid;
 
-	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
+	if (do_memsw_account())
 		return 0;
 
 	memcg = folio_memcg(folio);
@@ -7451,10 +7451,10 @@ void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
 	memcg = mem_cgroup_from_id(id);
 	if (memcg) {
 		if (!mem_cgroup_is_root(memcg)) {
-			if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
-				page_counter_uncharge(&memcg->swap, nr_pages);
-			else
+			if (do_memsw_account())
 				page_counter_uncharge(&memcg->memsw, nr_pages);
+			else
+				page_counter_uncharge(&memcg->swap, nr_pages);
 		}
 		mod_memcg_state(memcg, MEMCG_SWAP, -nr_pages);
 		mem_cgroup_id_put_many(memcg, nr_pages);