From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-173.mta1.migadu.com (out-173.mta1.migadu.com [95.215.58.173]) (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 562B5340A59 for ; Thu, 20 Nov 2025 13:39:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763645979; cv=none; b=PGUwBEjBz0EKayaRHEGpucuOFMZx25WfsHRR1+gzWzNaKULv04ursOXnoXGHNJwPWLqyT+tbSLqTp37iZmF4YuGwOjv0gf8D422ya6PhAiDYjWbLAiueP6+zQpXic+2XfkKSgkDKPLlwPFd2vgZY3E/pXueVLvTf4/5C8oBKBE8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763645979; c=relaxed/simple; bh=hkXe7RvFHHVtJLQkpvdP71g/k/1+IGz0BF9TRROxH/M=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KUPUYykPoV5xfHaFf39hHfKmzQUPOjwNhxuOeU23r/zPiReA391n5NOyoQs0AOPxkg6K8yIJ1pWGxkQMLzZEi5aw4sVQVfg4z41GiP5d7IE/myVRaKZnJPM5Sy2/fNtOrGFLbNyeu0Bb/SdB2IJ/BD+0SSZqtrxh8srmVjyhOBY= 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=A4d9y4YW; arc=none smtp.client-ip=95.215.58.173 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="A4d9y4YW" Message-ID: <82a16330-f801-46f9-bc4d-b10ae9e1472a@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1763645963; 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=4VBW5d85HPNjGo5XvcopxN5QwpZOcDhSseUA2IDtV6A=; b=A4d9y4YWBMIDtkYVklUQaOQptNvSdxm1jgBqV92EzXwKqRp6kfKDevWnXtE/QsdXN65gi5 n9IUhTH1NvnYDMs2/WbW/QyCefvwAe0xMwYh2pih3XH9sj9UJqFaEJEbaNa6MWWuRZsXvl azBSwSk/aVFUYrpaIUusu5PJC937F6A= Date: Thu, 20 Nov 2025 21:39:11 +0800 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v1 13/26] mm: mglru: prevent memory cgroup release in mglru To: Harry Yoo Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng References: X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 11/19/25 6:13 PM, Harry Yoo wrote: > On Tue, Oct 28, 2025 at 09:58:26PM +0800, Qi Zheng wrote: >> From: Muchun Song >> >> In the near future, a folio will no longer pin its corresponding >> memory cgroup. To ensure safety, it will only be appropriate to >> hold the rcu read lock or acquire a reference to the memory cgroup >> returned by folio_memcg(), thereby preventing it from being released. >> >> In the current patch, the rcu read lock is employed to safeguard >> against the release of the memory cgroup in mglru. >> >> This serves as a preparatory measure for the reparenting of the >> LRU pages. >> >> Signed-off-by: Muchun Song >> Signed-off-by: Qi Zheng >> --- >> mm/vmscan.c | 23 +++++++++++++++++------ >> 1 file changed, 17 insertions(+), 6 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 660cd40cfddd4..676e6270e5b45 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -4279,6 +4288,8 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) >> >> arch_leave_lazy_mmu_mode(); >> >> + rcu_read_unlock(); >> + >> /* feedback from rmap walkers to page table walkers */ >> if (mm_state && suitable_to_scan(i, young)) >> update_bloom_filter(mm_state, max_seq, pvmw->pmd); > > mm_state has the same life cycle as mem_cgroup. So it should be > protected by rcu read lock? You are right. The mm_state is defined as follows: struct lruvec { struct lru_gen_mm_state mm_state; }; will fix it in the next version. Thanks, Qi >