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From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: AE58320004 X-Rspamd-Server: rspam08 X-Stat-Signature: b1hiwpikcu5yowdpwqb6ocgspwgagohk X-HE-Tag: 1772881713-923095 X-HE-Meta: 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 lOGVKT9t q6l8jkbX2gOuqPlzAFSKfKUkH/MYSTNp5WXCL4ijQ882Fqn+PeRxCnEfqdy9BWqvniuOjIphcFSDrly/Q2/ze6YGIn38S+FvT+DCsPIWwrK06uOdx7JtPWbLy3BjoHgiz3sJeP2W95nq3FeDo9Q8Mg6hQwXJ6QP27xKzIej9drn81nMAy3HqIw0x3ceDYXT6KS9J3tbS8HZmo5pDpIsO6Roh+vrsRaOVQg7q6meh+AQnpDwhnWI4SY3v3Xg16q2eMdBcnBEDvs/eiy61D2/49PQDSout+PYrYwR5da5b6JLLdfQ8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 07/03/2026 08:51, Qi Zheng wrote: > Hi Usama, > > On 3/7/26 4:29 AM, Usama Arif wrote: >> On Thu,  5 Mar 2026 19:52:49 +0800 Qi Zheng wrote: >> >>> From: Qi Zheng >>> >>> Convert objcg to be per-memcg per-node type, so that when reparent LRU >>> folios later, we can hold the lru lock at the node level, thus avoiding >>> holding too many lru locks at once. >>> >>> Signed-off-by: Qi Zheng >>> Acked-by: Shakeel Butt >>> --- >>>   include/linux/memcontrol.h | 23 +++++------ >>>   include/linux/sched.h      |  2 +- >>>   mm/memcontrol.c            | 79 +++++++++++++++++++++++--------------- >>>   3 files changed, 62 insertions(+), 42 deletions(-) >>> >> >> [...] >> >>> @@ -4087,7 +4100,13 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) >>>       xa_store(&mem_cgroup_private_ids, memcg->id.id, memcg, GFP_KERNEL); >>>         return 0; >>> -free_shrinker: >>> +free_objcg: >>> +    for_each_node(nid) { >>> +        struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid]; >>> + >>> +        if (pn && pn->orig_objcg) >>> +            obj_cgroup_put(pn->orig_objcg); >> >> Is it possible that you might call obj_cgroup_put twice on the same cgroup? > > Oh, I think you are right. Here pn->orig_objcg was not reset to NULL, so > obj_cgroup_put() will be called in __mem_cgroup_free() again. > >> >> If css_create fails, css_free_rwork_fn is queued, which ends up calling >> mem_cgroup_css_free which calls obj_cgroup_put again? >> >> Maybe adding pn->orig_objcg = NULL overhere after obj_cgroup_put >> is enough to prevent the double put from causing issues? > > Agree. > > Like this? > Yes below looks good! Might be good to add a comment as well why setting it to NULL. > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 992a3f5caa62b..e0795aec4356b 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4140,8 +4140,10 @@ 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); > +                       pn->orig_objcg = NULL; > +               } >         } >         free_shrinker_info(memcg); >  offline_kmem: > > If there are no problems, I will send a fix patch later. > > Thanks, > Qi > >> >>> +    } >>>       free_shrinker_info(memcg); >>>   offline_kmem: >>>       memcg_offline_kmem(memcg); >>> --  >>> 2.20.1 >>> >>> >