From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4334C3BE16E for ; Wed, 25 Mar 2026 15:29:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774452542; cv=none; b=ZmMTBsSz7e4kFMJ0s926e1Tr6bUA6VbMSHNUggejXDJ96GQwOCne7Ty3Gi88TN2FXPH6tRUwcxWeidNFjxEUYSXFJpVd3XMP/E1BdyI6RqAiknsPCNgw2UszthXWN12YSClkmRZaT4whdbMhR6XP6W2EfMN34rvg3P6eUKPoA54= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774452542; c=relaxed/simple; bh=S+gB9lXh3YOTsDeZFSd4g0zO49rKXLKXwGpvrhbPAu8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bRQqInaVgHhBOzvGBkUdCizUKHZIb/thAwtMCum7JC1SuTjifDIPCYde9T2lLcimo+HDJsibQpQ9yA5mDQIJtjkssuFgEYfOLzMTC7k7PQZ9aXMSoIZ2EIWCLDCVoWzfUxZAzs5wlfQJz3VF1ilUe6Nr88fWIYQosregJ9pVJxI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CsU1vZ+n; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CsU1vZ+n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2560C4CEF7; Wed, 25 Mar 2026 15:28:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774452541; bh=S+gB9lXh3YOTsDeZFSd4g0zO49rKXLKXwGpvrhbPAu8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CsU1vZ+neeDNy1FrFSsnvYWLJC+Y5AbizxD9JdhZhz5TLzWJXU8AeQ3/KAJVp9MJx nOnwLgRcxQq9RfFkwfFk5uupxbbMwYYlGjMjdxWQpMAMjmrn9JmWZc0AQnNfWLu/Rf 4Shltt28OwDtEK6WwAPksJHzbrjfupQIkuYDawBFDDct8c8wSAwHLyF+ypUqBVmAji hiATEKCQbMcNYZWKj0qzZWHrWjfnEN3hKeLKYbMauPawZHgMiqCm/oKaSc2WjpwFQo spyzsqqnWDx97KRa0TK60JZpbHBH8qbORj5iWLnp/C95Fm9oYth+ZOZkLciVq8wk+w He9oxW9vKHw9Q== Date: Wed, 25 Mar 2026 15:28:53 +0000 From: "Lorenzo Stoakes (Oracle)" 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, 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, Qi Zheng Subject: Re: [PATCH v2 1/4] mm: memcontrol: correct the type of stats_updates to unsigned long Message-ID: References: <158fa0b1296168047342f02050e9d2bda6888d27.1774447069.git.zhengqi.arch@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158fa0b1296168047342f02050e9d2bda6888d27.1774447069.git.zhengqi.arch@bytedance.com> On Wed, Mar 25, 2026 at 10:13:22PM +0800, Qi Zheng wrote: > From: Qi Zheng > > The memcg_rstat_updated() tracks updates for vmstats_percpu->state > and lruvec_stats_percpu->state. Since these state values are of type long, > change the val parameter passed to memcg_rstat_updated() to long as well. > > Correspondingly, change the type of stats_updates in struct > memcg_vmstats_percpu and struct memcg_vmstats from unsigned int and > atomic_t to unsigned long and atomic_long_t respectively to prevent > potential overflow when handling large state updates during the > reparenting of LRU folios. Do we need a Fixes, possibly cc: stable for that? Apologies if already asked + answered. > > Signed-off-by: Qi Zheng Anyway logic seems fine to me, so: Reviewed-by: Lorenzo Stoakes (Oracle) > --- > mm/memcontrol.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index a47fb68dd65f1..7fb9cbc10dfbb 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -608,7 +608,7 @@ static inline int memcg_events_index(enum vm_event_item idx) > > struct memcg_vmstats_percpu { > /* Stats updates since the last flush */ > - unsigned int stats_updates; > + unsigned long stats_updates; > > /* Cached pointers for fast iteration in memcg_rstat_updated() */ > struct memcg_vmstats_percpu __percpu *parent_pcpu; > @@ -639,7 +639,7 @@ struct memcg_vmstats { > unsigned long events_pending[NR_MEMCG_EVENTS]; > > /* Stats updates since the last flush */ > - atomic_t stats_updates; > + atomic_long_t stats_updates; > }; > > /* > @@ -665,16 +665,16 @@ static u64 flush_last_time; > > static bool memcg_vmstats_needs_flush(struct memcg_vmstats *vmstats) > { > - return atomic_read(&vmstats->stats_updates) > > + return atomic_long_read(&vmstats->stats_updates) > > MEMCG_CHARGE_BATCH * num_online_cpus(); > } > > -static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val, > +static inline void memcg_rstat_updated(struct mem_cgroup *memcg, long val, > int cpu) > { > struct memcg_vmstats_percpu __percpu *statc_pcpu; > struct memcg_vmstats_percpu *statc; > - unsigned int stats_updates; > + unsigned long stats_updates; > > if (!val) > return; > @@ -697,7 +697,7 @@ static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val, > continue; > > stats_updates = this_cpu_xchg(statc_pcpu->stats_updates, 0); > - atomic_add(stats_updates, &statc->vmstats->stats_updates); > + atomic_long_add(stats_updates, &statc->vmstats->stats_updates); > } > } > > @@ -705,7 +705,7 @@ static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force) > { > bool needs_flush = memcg_vmstats_needs_flush(memcg->vmstats); > > - trace_memcg_flush_stats(memcg, atomic_read(&memcg->vmstats->stats_updates), > + trace_memcg_flush_stats(memcg, atomic_long_read(&memcg->vmstats->stats_updates), > force, needs_flush); > > if (!force && !needs_flush) > @@ -4406,8 +4406,8 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) > } > WRITE_ONCE(statc->stats_updates, 0); > /* We are in a per-cpu loop here, only do the atomic write once */ > - if (atomic_read(&memcg->vmstats->stats_updates)) > - atomic_set(&memcg->vmstats->stats_updates, 0); > + if (atomic_long_read(&memcg->vmstats->stats_updates)) > + atomic_long_set(&memcg->vmstats->stats_updates, 0); > } > > static void mem_cgroup_fork(struct task_struct *task) > -- > 2.20.1 >