memcg: introduce memcg_uncharge

At multiple places in memcontrol.c, the memory and memsw page counters are
being uncharged.  This is error-prone.  Let's move the functionality to a
newly introduced memcg_uncharge and call it from all those places.

Link: https://lkml.kernel.org/r/20250404013913.1663035-4-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 52be78515d70cae5609ea1f64c3cb65f010947fe..dfb3f14c1178a243832350e6457c5604cd335018 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1822,6 +1822,13 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages,
        return ret;
 }
 
+static void memcg_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages)
+{
+       page_counter_uncharge(&memcg->memory, nr_pages);
+       if (do_memsw_account())
+               page_counter_uncharge(&memcg->memsw, nr_pages);
+}
+
 /*
  * Returns stocks cached in percpu and reset cached information.
  */
@@ -1834,10 +1841,7 @@ static void drain_stock(struct memcg_stock_pcp *stock)
                return;
 
        if (stock_pages) {
-               page_counter_uncharge(&old->memory, stock_pages);
-               if (do_memsw_account())
-                       page_counter_uncharge(&old->memsw, stock_pages);
-
+               memcg_uncharge(old, stock_pages);
                WRITE_ONCE(stock->nr_pages, 0);
        }
 
@@ -1900,9 +1904,7 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
                 * In case of unlikely failure to lock percpu stock_lock
                 * uncharge memcg directly.
                 */
-               page_counter_uncharge(&memcg->memory, nr_pages);
-               if (do_memsw_account())
-                       page_counter_uncharge(&memcg->memsw, nr_pages);
+               memcg_uncharge(memcg, nr_pages);
                return;
        }
        __refill_stock(memcg, nr_pages);
@@ -2876,12 +2878,8 @@ static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock)
 
                        mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages);
                        memcg1_account_kmem(memcg, -nr_pages);
-                       if (!mem_cgroup_is_root(memcg)) {
-                               page_counter_uncharge(&memcg->memory, nr_pages);
-                               if (do_memsw_account())
-                                       page_counter_uncharge(&memcg->memsw,
-                                                             nr_pages);
-                       }
+                       if (!mem_cgroup_is_root(memcg))
+                               memcg_uncharge(memcg, nr_pages);
 
                        css_put(&memcg->css);
                }
@@ -4702,9 +4700,7 @@ static inline void uncharge_gather_clear(struct uncharge_gather *ug)
 static void uncharge_batch(const struct uncharge_gather *ug)
 {
        if (ug->nr_memory) {
-               page_counter_uncharge(&ug->memcg->memory, ug->nr_memory);
-               if (do_memsw_account())
-                       page_counter_uncharge(&ug->memcg->memsw, ug->nr_memory);
+               memcg_uncharge(ug->memcg, ug->nr_memory);
                if (ug->nr_kmem) {
                        mod_memcg_state(ug->memcg, MEMCG_KMEM, -ug->nr_kmem);
                        memcg1_account_kmem(ug->memcg, -ug->nr_kmem);