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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0686C54EE9 for ; Mon, 19 Sep 2022 10:46:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229673AbiISKqK (ORCPT ); Mon, 19 Sep 2022 06:46:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34558 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229976AbiISKpn (ORCPT ); Mon, 19 Sep 2022 06:45:43 -0400 Received: from out1.migadu.com (out1.migadu.com [IPv6:2001:41d0:2:863f::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F6D16168; Mon, 19 Sep 2022 03:28:36 -0700 (PDT) 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=1663583314; 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=HbKeZTfik2pMHV79p6gXSE8IXVFHdfJd0El4C7BHEQ8=; b=JbdRu245UdkmBLOGcN3/fNgHPJC5p/+OggoJGFmdGN8IiimLru+Hmkd4rPBj9IeD5Omhih cMyoIV3oysKNw+jABMyMeksiAfwPuCKlyzSajNjlyRTzTR4c+XQn78/5CwhTvchNS1RDEw XTGanU/cSkW0aT+dNKwoda7pELseY4c= From: Guoqing Jiang Subject: Re: [PATCH v3 5/5] md/raid10: convert resync_lock to use seqlock To: Yu Kuai , song@kernel.org, logang@deltatee.com, pmenzel@molgen.mpg.de Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, "yukuai3@huawei.com >> yukuai (C)" References: <20220916113428.774061-1-yukuai1@huaweicloud.com> <20220916113428.774061-6-yukuai1@huaweicloud.com> Message-ID: Date: Mon, 19 Sep 2022 18:28:29 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On 9/19/22 9:08 AM, Yu Kuai wrote: > Hi, > > 在 2022/09/18 19:36, Guoqing Jiang 写道: >> >> >> On 9/16/22 7:34 PM, Yu Kuai wrote: >>> From: Yu Kuai >>> >>> Currently, wait_barrier() will hold 'resync_lock' to read >>> 'conf->barrier', >>> and io can't be dispatched until 'barrier' is dropped. >>> >>> Since holding the 'barrier' is not common, convert 'resync_lock' to use >>> seqlock so that holding lock can be avoided in fast path. >>> >>> Signed-off-by: Yu Kuai >>> --- >>>   drivers/md/raid10.c | 87 >>> ++++++++++++++++++++++++++++++--------------- >>>   drivers/md/raid10.h |  2 +- >>>   2 files changed, 59 insertions(+), 30 deletions(-) >>> >>> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c >>> index 9a28abd19709..2daa7d57034c 100644 >>> --- a/drivers/md/raid10.c >>> +++ b/drivers/md/raid10.c >>> @@ -79,6 +79,21 @@ static void end_reshape(struct r10conf *conf); >>>   #include "raid1-10.c" >>> +#define NULL_CMD >>> +#define cmd_before(conf, cmd) \ >>> +    do { \ >>> +        write_sequnlock_irq(&(conf)->resync_lock); \ >>> +        cmd; \ >>> +    } while (0) >>> +#define cmd_after(conf) write_seqlock_irq(&(conf)->resync_lock) >> >> The two is not paired well given only cmd_before needs the 'cmd'. > > May be should I just remove cmd_after? I'd remove it but just my personal flavor. >> >>> + >>> +#define wait_event_barrier_cmd(conf, cond, cmd) \ >>> +    wait_event_cmd((conf)->wait_barrier, cond, cmd_before(conf, >>> cmd), \ >>> +               cmd_after(conf)) >>> + >>> +#define wait_event_barrier(conf, cond) \ >>> +    wait_event_barrier_cmd(conf, cond, NULL_CMD) >> >> What is the issue without define NULL_CMD? >> > > Checkpatch will complain this: > > ERROR: space prohibited before that close parenthesis ')' > #38: FILE: drivers/md/raid10.c:94: > +       wait_event_barrier_cmd(conf, cond, ) > > total: 1 errors, 0 warnings, 169 lines checked Hmm, freeze_array has a different usage for it, so two cmds before sleep and one cmd after sleep, perhaps it is the best way for now. Thanks, Guoqing