From nobody Fri Dec 19 17:14:44 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 BB45CECAAA1 for ; Mon, 24 Oct 2022 11:46:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231424AbiJXLqr (ORCPT ); Mon, 24 Oct 2022 07:46:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231844AbiJXLog (ORCPT ); Mon, 24 Oct 2022 07:44:36 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 65DF110BE; Mon, 24 Oct 2022 04:42:05 -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 B93406129E; Mon, 24 Oct 2022 11:40:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9F80C433C1; Mon, 24 Oct 2022 11:40:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666611647; bh=+I0xfy1z0X+lsymIB2vC9bMATzX/t2nZ5Oe46nZnOzY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Jidp2Y8nsnEnavBQn+EioPMg2cQv9p/mpOPe0XUCePdPln2UZ2Cp1Ldss6cN1Vy5r qc1jba3UIl7MqR1hCTcN23ZkwL9ZO3UEXHn9kXpk+gQ065EovmO4iGXBYLsvLnsIQ3 PhRKMA2FOjW7rtdAQ+lOYIDe4OAyabggSyS9Zvso= 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 4.9 058/159] ext4: place buffer head allocation before handle start Date: Mon, 24 Oct 2022 13:30:12 +0200 Message-Id: <20221024112951.560021650@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024112949.358278806@linuxfoundation.org> References: <20221024112949.358278806@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 @@ -1215,6 +1215,13 @@ retry_grab: page =3D grab_cache_page_write_begin(mapping, index, flags); 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: