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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD9CBC432C0 for ; Mon, 2 Dec 2019 19:41:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A8CE120848 for ; Mon, 2 Dec 2019 19:41:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728031AbfLBTlP (ORCPT ); Mon, 2 Dec 2019 14:41:15 -0500 Received: from mx.ewheeler.net ([173.205.220.69]:49709 "EHLO mx.ewheeler.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727927AbfLBTlP (ORCPT ); Mon, 2 Dec 2019 14:41:15 -0500 X-Greylist: delayed 385 seconds by postgrey-1.27 at vger.kernel.org; Mon, 02 Dec 2019 14:41:14 EST Received: from localhost (localhost [127.0.0.1]) by mx.ewheeler.net (Postfix) with ESMTP id 5EF76A0440; Mon, 2 Dec 2019 19:34:44 +0000 (UTC) X-Virus-Scanned: amavisd-new at ewheeler.net Received: from mx.ewheeler.net ([127.0.0.1]) by localhost (mx.ewheeler.net [127.0.0.1]) (amavisd-new, port 10024) with LMTP id uRQNVO4LW8_g; Mon, 2 Dec 2019 19:34:23 +0000 (UTC) Received: from mx.ewheeler.net (mx.ewheeler.net [173.205.220.69]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx.ewheeler.net (Postfix) with ESMTPSA id 1F97BA0693; Mon, 2 Dec 2019 19:34:23 +0000 (UTC) Date: Mon, 2 Dec 2019 19:34:12 +0000 (UTC) From: Eric Wheeler X-X-Sender: lists@mx.ewheeler.net To: Coly Li cc: kungf , kent.overstreet@gmail.com, linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] bcache: add REQ_FUA to avoid data lost in writeback mode In-Reply-To: <785fe04f-f841-3083-66db-53fab7bc0577@suse.de> Message-ID: References: <20191202102409.3980-1-wings.wyang@gmail.com> <785fe04f-f841-3083-66db-53fab7bc0577@suse.de> User-Agent: Alpine 2.11 (LRH 23 2013-08-11) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-844282404-2137853158-1575315263=:11561" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---844282404-2137853158-1575315263=:11561 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Mon, 2 Dec 2019, Coly Li wrote: > On 2019/12/2 6:24 下午, kungf wrote: > > data may lost when in the follow scene of writeback mode: > > 1. client write data1 to bcache > > 2. client fdatasync > > 3. bcache flush cache set and backing device > > if now data1 was not writed back to backing, it was only guaranteed safe in cache. > > 4.then cache writeback data1 to backing with only REQ_OP_WRITE > > So data1 was not guaranteed in non-volatile storage, it may lost if power interruption  > > > > Hi, > > Do you encounter such problem in real work load ? With bcache journal, I > don't see the possibility of data lost with your description. > > Correct me if I am wrong. > > Coly Li If this does become necessary, then we should have a sysfs or superblock flag to disable FUA for those with RAID BBUs. -- Eric Wheeler > > Signed-off-by: kungf > > --- > > drivers/md/bcache/writeback.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c > > index 4a40f9eadeaf..e5cecb60569e 100644 > > --- a/drivers/md/bcache/writeback.c > > +++ b/drivers/md/bcache/writeback.c > > @@ -357,7 +357,7 @@ static void write_dirty(struct closure *cl) > > */ > > if (KEY_DIRTY(&w->key)) { > > dirty_init(w); > > - bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0); > > + bio_set_op_attrs(&io->bio, REQ_OP_WRITE | REQ_FUA, 0); > > io->bio.bi_iter.bi_sector = KEY_START(&w->key); > > bio_set_dev(&io->bio, io->dc->bdev); > > io->bio.bi_end_io = dirty_endio; > > > > ---844282404-2137853158-1575315263=:11561--