From nobody Fri Oct 17 10:31:34 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6D1CC4332F for ; Wed, 19 Oct 2022 08:47:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231559AbiJSIrE (ORCPT ); Wed, 19 Oct 2022 04:47:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231397AbiJSIpw (ORCPT ); Wed, 19 Oct 2022 04:45:52 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2B0E868B9; Wed, 19 Oct 2022 01:44:15 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A3690617AC; Wed, 19 Oct 2022 08:44:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1F63C433D6; Wed, 19 Oct 2022 08:44:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666169055; bh=VtFKGsLaErRVzOB9Z09DPYXE6t91wddQ7M2ZiRFgHpo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=d36zqZGDmODF1s5zSqRCAvH+CPB9crylxW+0etX7rV1eDtIBejDmZg4mJvbSDLMJ8 oDEAM+jvwMNGRX6Fo5BHr4LUR3z0RhFAgBQTWRgvvsqh03/94QZr7VwaVuc9SZdydv JSihO+j11E3Af5wWTIiGhm4vL5KSFCG5pIsKwFM0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, stable@kernel.org, Jinke Han , Theodore Tso Subject: [PATCH 6.0 142/862] ext4: place buffer head allocation before handle start Date: Wed, 19 Oct 2022 10:23:49 +0200 Message-Id: <20221019083256.258802162@linuxfoundation.org> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221019083249.951566199@linuxfoundation.org> References: <20221019083249.951566199@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Jinke Han commit d1052d236eddf6aa851434db1897b942e8db9921 upstream. In our product environment, we encounter some jbd hung waiting handles to stop while several writters were doing memory reclaim for buffer head allocation in delay alloc write path. Ext4 do buffer head allocation with holding transaction handle which may be blocked too long if the reclaim works not so smooth. According to our bcc trace, the reclaim time in buffer head allocation can reach 258s and the jbd transaction commit also take almost the same time meanwhile. Except for these extreme cases, we often see several seconds delays for cgroup memory reclaim on our servers. This is more likely to happen considering docker environment. One thing to note, the allocation of buffer heads is as often as page allocation or more often when blocksize less than page size. Just like page cache allocation, we should also place the buffer head allocation before startting the handle. Cc: stable@kernel.org Signed-off-by: Jinke Han Link: https://lore.kernel.org/r/20220903012429.22555-1-hanjinke.666@bytedan= ce.com Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/inode.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1188,6 +1188,13 @@ retry_grab: page =3D grab_cache_page_write_begin(mapping, index); if (!page) return -ENOMEM; + /* + * The same as page allocation, we prealloc buffer heads before + * starting the handle. + */ + if (!page_has_buffers(page)) + create_empty_buffers(page, inode->i_sb->s_blocksize, 0); + unlock_page(page); =20 retry_journal: