mm: memcg: add NULL check to obj_cgroup_put()

9 out of 16 callers perform a NULL check before calling obj_cgroup_put().
Move the NULL check in the function, similar to mem_cgroup_put().  The
unlikely() NULL check in current_objcg_update() was left alone to avoid
dropping the unlikey() annotation as this a fast path.

Link: https://lkml.kernel.org/r/20240316015803.2777252-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 394fd0a887ae75eae7c31cf948eafa1bb12a38fe..b6264796815d427121dd25423b6ebb916322c979 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -818,7 +818,8 @@ static inline void obj_cgroup_get_many(struct obj_cgroup *objcg,
 
 static inline void obj_cgroup_put(struct obj_cgroup *objcg)
 {
-       percpu_ref_put(&objcg->refcnt);
+       if (objcg)
+               percpu_ref_put(&objcg->refcnt);
 }
 
 static inline bool mem_cgroup_tryget(struct mem_cgroup *memcg)

diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index 550f02e2cb1327e1d082a895f3be16f22bf06f57..a546aba46d5da9fcebfaaf5663971c70c6c01c0e 100644 (file)
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -759,8 +759,7 @@ void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma)
                        rcu_in_progress += atomic_read(&c->call_rcu_ttrace_in_progress);
                        rcu_in_progress += atomic_read(&c->call_rcu_in_progress);
                }
-               if (ma->objcg)
-                       obj_cgroup_put(ma->objcg);
+               obj_cgroup_put(ma->objcg);
                destroy_mem_alloc(ma, rcu_in_progress);
        }
        if (ma->caches) {
@@ -776,8 +775,7 @@ void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma)
                                rcu_in_progress += atomic_read(&c->call_rcu_in_progress);
                        }
                }
-               if (ma->objcg)
-                       obj_cgroup_put(ma->objcg);
+               obj_cgroup_put(ma->objcg);
                destroy_mem_alloc(ma, rcu_in_progress);
        }
 }

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fabce2b50c69551e46b0197cbad5a96cb79dde19..786c0fae6e30924a81c3c187d448bb423adb4f30 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2369,8 +2369,7 @@ static void drain_local_stock(struct work_struct *dummy)
        clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
 
        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
-       if (old)
-               obj_cgroup_put(old);
+       obj_cgroup_put(old);
 }
 
 /*
@@ -3145,8 +3144,7 @@ static struct obj_cgroup *current_objcg_update(void)
                if (old) {
                        old = (struct obj_cgroup *)
                                ((unsigned long)old & ~CURRENT_OBJCG_UPDATE_FLAG);
-                       if (old)
-                               obj_cgroup_put(old);
+                       obj_cgroup_put(old);
 
                        old = NULL;
                }
@@ -3418,8 +3416,7 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
                mod_objcg_mlstate(objcg, pgdat, idx, nr);
 
        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
-       if (old)
-               obj_cgroup_put(old);
+       obj_cgroup_put(old);
 }
 
 static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
@@ -3546,8 +3543,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
        }
 
        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
-       if (old)
-               obj_cgroup_put(old);
+       obj_cgroup_put(old);
 
        if (nr_pages)
                obj_cgroup_uncharge_pages(objcg, nr_pages);
@@ -5468,8 +5464,7 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg)
 {
        int node;
 
-       if (memcg->orig_objcg)
-               obj_cgroup_put(memcg->orig_objcg);
+       obj_cgroup_put(memcg->orig_objcg);
 
        for_each_node(node)
                free_mem_cgroup_per_node_info(memcg, node);
@@ -6620,8 +6615,7 @@ static void mem_cgroup_exit(struct task_struct *task)
 
        objcg = (struct obj_cgroup *)
                ((unsigned long)objcg & ~CURRENT_OBJCG_UPDATE_FLAG);
-       if (objcg)
-               obj_cgroup_put(objcg);
+       obj_cgroup_put(objcg);
 
        /*
         * Some kernel allocations can happen after this point,

diff --git a/mm/zswap.c b/mm/zswap.c
index 6f8850c44b6166d363d20813732d9b1befc22c61..2817e2791c135050f5bb401976583aecc441260e 100644 (file)
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1618,8 +1618,7 @@ put_pool:
 freepage:
        zswap_entry_cache_free(entry);
 reject:
-       if (objcg)
-               obj_cgroup_put(objcg);
+       obj_cgroup_put(objcg);
 check_old:
        /*
         * If the zswap store fails or zswap is disabled, we must invalidate the