From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5576F34CFBD for ; Sat, 7 Mar 2026 11:08:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772881715; cv=none; b=Odg+ujOlBqL4FrmDDdHNkP9YYw15pbQJRzWNfE7rmED3XYEdkhivXPJtZJLxgXwwgfqGVu09ZoMTxvMrtqEjjcJgXICm+fyZit/ab4uhA4ukSito2oqDOLji+QCfEy1qZmeAMHfW7Cuch/Krpxfy8EGJaO+Vf+zvl3FjRMXyCg4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772881715; c=relaxed/simple; bh=PLDDDyPHkkSfMtILwYY2Y87oGhso5hisie/vFK/S+oM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mM76ostDn1hteQWHJdpD5+CeUib0eqY2IK6xkLCXYB/AQJpWf9riMMqWsbqX3/gTfcQwerXRhecDH7c17nA4OJoLGJV2zrwQNTr+NFbMnEXAUEsn+j6jx1pYuvFJK9WeFriq2X/R5rjYi+6hR4dNRB/9T4RivgZgpCJKNxin2jY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=kfzZo6l6; arc=none smtp.client-ip=91.218.175.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="kfzZo6l6" Message-ID: <898e8ca7-efcb-4bd7-8016-871b37be830e@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772881711; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pQQUq7VI4DGC3acaTy19EaAJ0WQoVtzSXc8kQhaWbHc=; b=kfzZo6l69X5HrOvPj6d3TGCxNlYxsoIX97rJXw21pqm85Yy4fSQBuKP2SkSSVprE9sOwEY Ksd3u/afuQ+H+OtMWzyqydnVEwLKjMPJAArdwtmHfpUSpAVM1urZuoMKC6+i1hd4pyXMFt 0gXNx4N5pTuI2BSEQoP7E0x3P03dLHU= Date: Sat, 7 Mar 2026 14:08:25 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v6 31/33] mm: memcontrol: convert objcg to be per-memcg per-node type Content-Language: en-GB To: Qi Zheng Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, bhe@redhat.com, usamaarif642@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Qi Zheng References: <20260306202931.3878822-1-usama.arif@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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 >>> >>> >