From nobody Tue Feb 10 11:15:22 2026 Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) (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 5AB34393DD4 for ; Thu, 5 Feb 2026 09:04:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.188 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282249; cv=none; b=Nl6LqBm2Zzk7AJerHNN63oILzLmYtiUyK/dlNxzFa1JQkqtSVJph76sWtBQ0/LSmUeZ5c0lozeZLgt5Uk0F77QK1c8TungHd4UoCXNQim3In25AZqsByxfdxjmFf6q8kr1bY2IFfp8ATSzP0Fzr4Oby4o/fHWgzhtcKdN02RJA4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282249; c=relaxed/simple; bh=6p1rTQSn/szsvXfKM1Mr1/YwGhM74koqcntWzctOIok=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WH9I9Ud6eQABts+XwL7dFUAxh0Ve5+vSGa0qg+BX5gNL6hxSM6khbpCgR9CgPp6n5lxRumQ4tzT7fakoV/4pNONcRsaqSga4FoTlL6JyCPJ185Ccgt+tOViAUxMViJX35hfUCbEDLMbNomqVV7Hy40H+OH9uYY3S9B44e1Q36As= 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=WAJrOF27; arc=none smtp.client-ip=95.215.58.188 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="WAJrOF27" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1770282247; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9FlmauyfzMJ30WpiQCMliVOAMipux2gAWQ7/AZwbz08=; b=WAJrOF27HCB5BG4W4Di4FgtDhc8i110kCSU2tRmeUnuO1z1k7WPQt/L4RHD1/2BsrxR3mX zyHHe1wcSNkf2b+itnL1IIRsE6hcaMU1L/Pna41B8IAASe182aVKqM4oSd5dzRHEQq9IjY 3sKzG7UJhuWg/yfG+NB0L90DJYIBxx0= From: Qi Zheng To: 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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v4 21/31] mm: swap: prevent lruvec release in lru_gen_clear_refs() Date: Thu, 5 Feb 2026 17:01:40 +0800 Message-ID: In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" From: Muchun Song In the near future, a folio will no longer pin its corresponding memory cgroup. So an lruvec returned by folio_lruvec() could be released without the rcu read lock or a reference to its memory cgroup. In the current patch, the rcu read lock is employed to safeguard against the release of the lruvec in lru_gen_clear_refs(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Johannes Weiner Acked-by: Shakeel Butt --- mm/swap.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/swap.c b/mm/swap.c index 245ba159e01d7..cb1148a92d8ec 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -412,18 +412,20 @@ static void lru_gen_inc_refs(struct folio *folio) =20 static bool lru_gen_clear_refs(struct folio *folio) { - struct lru_gen_folio *lrugen; int gen =3D folio_lru_gen(folio); int type =3D folio_is_file_lru(folio); + unsigned long seq; =20 if (gen < 0) return true; =20 set_mask_bits(&folio->flags.f, LRU_REFS_FLAGS | BIT(PG_workingset), 0); =20 - lrugen =3D &folio_lruvec(folio)->lrugen; + rcu_read_lock(); + seq =3D READ_ONCE(folio_lruvec(folio)->lrugen.min_seq[type]); + rcu_read_unlock(); /* whether can do without shuffling under the LRU lock */ - return gen =3D=3D lru_gen_from_seq(READ_ONCE(lrugen->min_seq[type])); + return gen =3D=3D lru_gen_from_seq(seq); } =20 #else /* !CONFIG_LRU_GEN */ --=20 2.20.1