[v1] fix: mm: memcontrol: convert objcg to be per-memcg per-node type

[PATCH] fix: mm: memcontrol: convert objcg to be per-memcg per-node type

Posted by Qi Zheng 1 month ago

From: Qi Zheng <zhengqi.arch@bytedance.com>

Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
from being called agagin in __mem_cgroup_free().

Reported-by: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 mm/memcontrol.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 992a3f5caa62b..ad32639ea5959 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4140,8 +4140,14 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
 	for_each_node(nid) {
 		struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
 
-		if (pn && pn->orig_objcg)
+		if (pn && pn->orig_objcg) {
 			obj_cgroup_put(pn->orig_objcg);
+			/*
+			 * Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
+			 * from being called agagin in __mem_cgroup_free().
+			 */
+			pn->orig_objcg = NULL;
+		}
 	}
 	free_shrinker_info(memcg);
 offline_kmem:
-- 
2.20.1

Re: [PATCH] fix: mm: memcontrol: convert objcg to be per-memcg per-node type

Posted by Usama Arif 1 month ago


On 09/03/2026 14:29, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@bytedance.com>
> 
> Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
> from being called agagin in __mem_cgroup_free().
> 
> Reported-by: Usama Arif <usama.arif@linux.dev>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> ---
>  mm/memcontrol.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 992a3f5caa62b..ad32639ea5959 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4140,8 +4140,14 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
>  	for_each_node(nid) {
>  		struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
>  
> -		if (pn && pn->orig_objcg)
> +		if (pn && pn->orig_objcg) {
>  			obj_cgroup_put(pn->orig_objcg);
> +			/*
> +			 * Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
> +			 * from being called agagin in __mem_cgroup_free().

nit: s/agagin/again/

Apart from the nit.

Acked-by: Usama Arif <usama.arif@linux.dev>

> +			 */
> +			pn->orig_objcg = NULL;
> +		}
>  	}
>  	free_shrinker_info(memcg);
>  offline_kmem:

Re: [PATCH] fix: mm: memcontrol: convert objcg to be per-memcg per-node type

Posted by Qi Zheng 1 month ago


On 3/9/26 7:33 PM, Usama Arif wrote:
> 
> 
> On 09/03/2026 14:29, Qi Zheng wrote:
>> From: Qi Zheng <zhengqi.arch@bytedance.com>
>>
>> Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
>> from being called agagin in __mem_cgroup_free().
>>
>> Reported-by: Usama Arif <usama.arif@linux.dev>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>> ---
>>   mm/memcontrol.c | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 992a3f5caa62b..ad32639ea5959 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -4140,8 +4140,14 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
>>   	for_each_node(nid) {
>>   		struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
>>   
>> -		if (pn && pn->orig_objcg)
>> +		if (pn && pn->orig_objcg) {
>>   			obj_cgroup_put(pn->orig_objcg);
>> +			/*
>> +			 * Reset pn->orig_objcg to NULL to prevent obj_cgroup_put()
>> +			 * from being called agagin in __mem_cgroup_free().
> 
> nit: s/agagin/again/

Ouch, my bad.

Hi Andrew, can you help squash the following diff:

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ad32639ea5959..5fcbb651846a4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4144,7 +4144,7 @@ static int mem_cgroup_css_online(struct 
cgroup_subsys_state *css)
                         obj_cgroup_put(pn->orig_objcg);
                         /*
                          * Reset pn->orig_objcg to NULL to prevent 
obj_cgroup_put()
-                        * from being called agagin in __mem_cgroup_free().
+                        * from being called again in __mem_cgroup_free().
                          */
                         pn->orig_objcg = NULL;
                 }

> 
> Apart from the nit.
> 
> Acked-by: Usama Arif <usama.arif@linux.dev>

Thanks!

> 
>> +			 */
>> +			pn->orig_objcg = NULL;
>> +		}
>>   	}
>>   	free_shrinker_info(memcg);
>>   offline_kmem:
>