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mm: memcg: add NULL check to obj_cgroup_put()

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JIRA: https://issues.redhat.com/browse/RHEL-113275

commit 91b71e78b8e478e1a9af36b15ff1d38810572866
Author: Yosry Ahmed <yosryahmed@google.com>
Date:   Sat Mar 16 01:58:03 2024 +0000

    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>

Signed-off-by: Radostin Stoyanov <rstoyano@redhat.com>
This commit is contained in:
Radostin Stoyanov
2026-01-23 08:32:52 +00:00
parent 7674ae3ddf
commit 79b0243403
4 changed files with 11 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/memcontrol.h
+2 -1
View File
@@ -861,7 +861,8 @@ 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)
kernel/bpf/memalloc.c
+2 -4
View File
@@ -761,8 +761,7 @@ 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) {
@@ -778,8 +777,7 @@ 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);
}
}
mm/memcontrol.c
+6 -12
View File
@@ -2156,8 +2156,7 @@ 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);
}
/*
@@ -2941,8 +2940,7 @@ 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;
}
@@ -3214,8 +3212,7 @@ 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)
@@ -3342,8 +3339,7 @@ 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);
@@ -5208,8 +5204,7 @@ 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);
@@ -6401,8 +6396,7 @@ 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,
mm/zswap.c
+1 -2
View File
@@ -1766,8 +1766,7 @@ put_pool:
freepage:
zswap_entry_cache_free(entry);
reject:
if (objcg)
obj_cgroup_put(objcg);
obj_cgroup_put(objcg);
return false;
shrink: