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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 60D69C3F2D1 for ; Thu, 5 Mar 2020 04:27:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3BC362073B for ; Thu, 5 Mar 2020 04:27:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725838AbgCEE1I (ORCPT ); Wed, 4 Mar 2020 23:27:08 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:55765 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725818AbgCEE1I (ORCPT ); Wed, 4 Mar 2020 23:27:08 -0500 X-Originating-IP: 159.89.7.238 Received: from [10.55.55.2] (unknown [159.89.7.238]) (Authenticated sender: cengiz@kernel.wtf) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id C1ACE1C0007; Thu, 5 Mar 2020 04:27:03 +0000 (UTC) From: Cengiz Can To: Ming Lei CC: Keith Busch , Chaitanya Kulkarni , Jens Axboe , Bjorn Helgaas , Jan Kara , "linux-block" , stable , Date: Thu, 05 Mar 2020 07:27:02 +0300 Message-ID: <170a8f261f0.2bfa.85c738e3968116fc5c0dc2de74002084@kernel.wtf> In-Reply-To: References: <20200302220639.GA2393@dhcp-10-100-145-180.wdl.wdc.com> <20200303110731.65552-1-cengiz@kernel.wtf> User-Agent: AquaMail/1.23.0-1556 (build: 102300002) Subject: Re: [PATCH] blktrace: Protect q->blk_trace with RCU MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="us-ascii" Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On March 5, 2020 04:51:51 Ming Lei wrote: > On Tue, Mar 3, 2020 at 8:37 PM Cengiz Can wrote: >> >> Added a reassignment into the NULL check block to fix the issue. >> >> Fixes: c780e86dd48 ("blktrace: Protect q->blk_trace with RCU") >> >> Signed-off-by: Cengiz Can >> --- >> kernel/trace/blktrace.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c >> index 4560878f0bac..29ea88f10b87 100644 >> --- a/kernel/trace/blktrace.c >> +++ b/kernel/trace/blktrace.c >> @@ -1896,8 +1896,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct >> device *dev, >> } >> >> ret = 0; >> - if (bt == NULL) >> + if (bt == NULL) { >> ret = blk_trace_setup_queue(q, bdev); >> + bt = q->blk_trace; > > I'd suggest to use the following line for avoiding RCU warning: > > bt = rcu_dereference_protected(q->blk_trace, > lockdep_is_held(&q->blk_trace_mutex)); > > Otherwise, the patch looks fine for me: Thank you. Please kindly see v2. > > Reviewed-by: Ming Lei > > Thanks, > Ming Lei