From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 56875C43458 for ; Thu, 9 Jul 2026 04:17:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F17AD6B0088; Thu, 9 Jul 2026 00:17:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EEE466B008A; Thu, 9 Jul 2026 00:17:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E2DB76B008C; Thu, 9 Jul 2026 00:17:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id BA5D66B0088 for ; Thu, 9 Jul 2026 00:17:27 -0400 (EDT) Received: from smtpin01.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 31BE91C8125 for ; Thu, 9 Jul 2026 04:17:26 +0000 (UTC) X-FDA: 84967928892.01.1BE794E Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) by imf30.hostedemail.com (Postfix) with ESMTP id 0227780002 for ; Thu, 9 Jul 2026 04:17:23 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=icLsN4oX; spf=pass (imf30.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.180 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1783570644; h=from:from:sender: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:dkim-signature; bh=UBqGUL0+KiK1FMBVGSLXqyXS9/Lja6xJ1/PzEqDDCFY=; b=DwpqXkTzk1AYwz22sXTfiM48rZsHuSPQaX2OOQu6uIeFHWB8GNJ0nb1bvbr87qpUDsPdnI tUrFI9kDTtM4kTQOQJQBODCjsvzaLXWVCClFfTVvvGuHQiHdxj8l1cJf+Dflx/Vh7qsiDs Pxz7wS+tlNNdRihV22byjdNlvetRVoc= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1783570644; b=oJwdaf6ng6/Rhj6TbC88HNP193T1pIOeTUtJ3VoHHkazrsADee9qQAC24HwwBOPgdu4Iqy tcJvsVI4wz0ivrDIaEOxGevPXYRxsTVSS2zO9IJhwiS7gPOpITrssBMSqq5SS/XeCH6j9H XebDnjPUMk/9JKwcLRTNOvHHgdPnazk= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=icLsN4oX; spf=pass (imf30.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.180 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783570642; 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=UBqGUL0+KiK1FMBVGSLXqyXS9/Lja6xJ1/PzEqDDCFY=; b=icLsN4oXxOuREtLzUD4RXdMBccXd3DogAuZu4P1fEGCT4JgDFQZq7H9tzLzb0F0iYq0bME bOQp8MNv4Xq5eO+wuHws9itPdkw19ohX6bpcS859IzbhmKMOrEMHmLCIGXPSamjlWfuvpY De4KCJBJwUMom/iyle/je2BeLnQsmEQ= Date: Thu, 9 Jul 2026 12:17:10 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v4] mm: mglru: fix stale batch updates after memcg reparenting To: akpm@linux-foundation.org, david@kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng , stable@vger.kernel.org, kasong@tencent.com, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, harry@kernel.org, muchun.song@linux.dev, peiyang_he@smail.nju.edu.cn, mhocko@kernel.org, roman.gushchin@linux.dev, ljs@kernel.org References: <20260701075251.56413-1-qi.zheng@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <20260701075251.56413-1-qi.zheng@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0227780002 X-Stat-Signature: 4pcc14weidwgj8f1e8ngj9ohboc6xyjk X-HE-Tag: 1783570643-697997 X-HE-Meta: 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 OyWvcVPu V3329NC+xtGN0eTnxcRWMM2Ubk/liCWLq/UVg8Qq98edZxYHUbWSGPhuuX711cWrdBQzfCITdrruA2LT8Z9ztWK3zGT+RS1j/sExsH37+iDSfrencnO4x9uRwthwOLHlZwIxaFlXw8ZXNR1fAkeBaUM141uJA9PEpm7q1lwSu12cXTkNpIUD7jvY2pZmlHGHRTfkJwmPFhL5Q3faz+xZ0HFpCk6/ZR4dpPdZx8lsR1qt1E4gMfl+epsHUHOFelZzqR8F8 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Andrew and David, Gentle ping. Is this patch good to be applied? Thanks, Qi On 7/1/26 3:52 PM, Qi Zheng wrote: > From: Qi Zheng > > The mglru page table walker batches per-generation size deltas in > walk->nr_pages while walking page tables without holding the lruvec lock. > The reset_batch_size() later folds those deltas into walk->lruvec under > the lruvec lock. > > The page table walker can run concurrently with the memcg reparenting path > as follows: > > CPU0 CPU1 > ==== ==== > > walk_mm > --> walk_page_range > --> update_batch_size > --> walk->nr_pages += delta > > mem_cgroup_css_offline > --> memcg_reparent_objcgs > --> lock lruvec > lru_gen_reparent_memcg > --> reparent child folios to parent > unlock lruvec > > lock lruvec > reset_batch_size > --> child lrugen->nr_pages += delta > > This will trigger the following warning in lru_gen_exit_memcg(): > > VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0, > sizeof(lruvec->lrugen.nr_pages))); > > And the user-visible impact of underestimated nr_pages in MGLRU was > premature OOMs because MGLRU does not try to reclaim memory when nr_pages > reaches zero, but there are still more pages. > > To fix it, make reset_batch_size() check CSS_DYING under RCU before > flushing the pending batch. A non-dying memcg keeps the original lruvec > stable against RCU-delayed offlining; a dying memcg redirects the deltas > to the first non-dying ancestor. > > Reported-by: Peiyang He > Closes: https://lore.kernel.org/all/5A9E929D82717101+12fcf643-efb8-4b9a-a53a-1e28cc894f0b@smail.nju.edu.cn > Fixes: f304652609ea ("mm: vmscan: prepare for reparenting MGLRU folios") > Cc: > Signed-off-by: Qi Zheng > Reviewed-by: Harry Yoo (Oracle) > --- > Changes in v4: > - re-implement lock_batch_lruvec() in a simpler way > (suggested by Johannes and Harry) > - collect Reviewed-by > - rebase onto the next-20260630 >