From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) (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 597FD33122D for ; Thu, 18 Dec 2025 06:50:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766040636; cv=none; b=SFIHA4nrtijwDYHtqAGxAo2Nk52N6IYsTg4kSaRfmx2RfP9XDVmWi//iRKIV4KoDn+1ZTqR4XvWQuFQMxgjZPnA1jt3/IG07w0YtUFvHov/d7x6yuWO5UgkARq92tnTLOD7HWvubffqs5SCJrjwSKWEH6Ng2rme7EU+jTqZpjPM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766040636; c=relaxed/simple; bh=V3pWVQx7qFzNjskJIdOmv8h/kW8OOhv/SOKrPzO4Cmw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pL/i/TS4lWHL1ACxWhFFSJRMf2CsxvojpdLtYYMeV1vbusRuE5CN8GGMSYDS5t2TVv3ow9FnDMhET1hmWZnP3TrLk4X10LaYQZY85Luh/d1hFIC765tnNR52mX4A4BtojojClphipHa57sGahngDSVgXgnLEAMUXSJrQLORUZJA= 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=qqYeirWs; arc=none smtp.client-ip=91.218.175.179 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="qqYeirWs" Message-ID: <4513ee04-03ff-4de0-bbf4-b5b35dfd41ad@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766040631; 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=dW1sFUrpgDlh6EpvXxN9ly9S/e1gx9r8RyoILFDsHvs=; b=qqYeirWsSALh+5MJ3vqdKKt01VPxpqJMm9SbwN9uQ2gnloClPekoB/b0dUyK0Q/KKCItnz lQxU2gJPqVR6ATWE/UNNaLHwgFbkLxIPksppMfCKHALKrQuapRMg2sVGEJQXMUT+PkABkK 4+ude2eYI1txPiaCzHrkn0AnpdXTx7A= Date: Thu, 18 Dec 2025 14:50:19 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2 14/28] mm: mglru: prevent memory cgroup release in mglru To: Johannes Weiner Cc: 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, 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, 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 12/18/25 6:18 AM, Johannes Weiner wrote: > On Wed, Dec 17, 2025 at 03:27:38PM +0800, Qi Zheng wrote: >> @@ -4242,6 +4244,13 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) >> } >> } >> >> + rcu_read_lock(); >> + memcg = folio_memcg(folio); >> + lruvec = mem_cgroup_lruvec(memcg, pgdat); >> + max_seq = READ_ONCE((lruvec)->lrugen.max_seq); >> + gen = lru_gen_from_seq(max_seq); >> + mm_state = get_mm_state(lruvec); >> + >> arch_enter_lazy_mmu_mode(); >> >> pte -= (addr - start) / PAGE_SIZE; >> @@ -4282,6 +4291,8 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) >> if (mm_state && suitable_to_scan(i, young)) >> update_bloom_filter(mm_state, max_seq, pvmw->pmd); >> >> + rcu_read_unlock(); >> + >> return true; > > This seems a bit long to be holding the rcu lock. Indeed. > Maybe do a get and a > put instead? OK, will use get_mem_cgroup_from_folio(folio) to do this. This way, #8 doesn't need to be folded into #27.