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=-16.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 76E9DC433E6 for ; Mon, 8 Feb 2021 14:50:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 401FB64E75 for ; Mon, 8 Feb 2021 14:50:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232839AbhBHOuZ (ORCPT ); Mon, 8 Feb 2021 09:50:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:48906 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232929AbhBHOtt (ORCPT ); Mon, 8 Feb 2021 09:49:49 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0E4B364DD5; Mon, 8 Feb 2021 14:49:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612795746; bh=Y6fziRpW9V/TdLpks4xbZW/OLBoVJsPuYzoRRPrtiD8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uZTmzx/bCNB/tlwETj5IOMa18yKjIIQRTh/sbyF9ccYh9ATk8H1bhNZ7dXHtU6r8D ERotQXmyI7PbczpWoL1O/Q8/Dh+68LKgzPV+y2rA8hmReqqdln8V5YGgIysQy42Sct UXRZa9YC3+nJs/j5kwVqd/2HLHgsB3K0AlXPFyFQ= Date: Mon, 8 Feb 2021 15:49:03 +0100 From: Greg KH To: Jinpu Wang Cc: Sasha Levin , stable , Xiao Ni , David Jeffery , Song Liu Subject: Re: [stable-5.10] md: Set prev_flush_start and flush_bio in an atomic way Message-ID: References: <20210205141301.71682-1-jinpu.wang@cloud.ionos.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Feb 08, 2021 at 03:38:48PM +0100, Jinpu Wang wrote: > On Mon, Feb 8, 2021 at 1:45 PM Greg KH wrote: > > > > On Fri, Feb 05, 2021 at 03:13:01PM +0100, Jack Wang wrote: > > > From: Xiao Ni > > > > > > One customer reports a crash problem which causes by flush request. It > > > triggers a warning before crash. > > > > > > /* new request after previous flush is completed */ > > > if (ktime_after(req_start, mddev->prev_flush_start)) { > > > WARN_ON(mddev->flush_bio); > > > mddev->flush_bio = bio; > > > bio = NULL; > > > } > > > > > > The WARN_ON is triggered. We use spin lock to protect prev_flush_start and > > > flush_bio in md_flush_request. But there is no lock protection in > > > md_submit_flush_data. It can set flush_bio to NULL first because of > > > compiler reordering write instructions. > > > > > > For example, flush bio1 sets flush bio to NULL first in > > > md_submit_flush_data. An interrupt or vmware causing an extended stall > > > happen between updating flush_bio and prev_flush_start. Because flush_bio > > > is NULL, flush bio2 can get the lock and submit to underlayer disks. Then > > > flush bio1 updates prev_flush_start after the interrupt or extended stall. > > > > > > Then flush bio3 enters in md_flush_request. The start time req_start is > > > behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't > > > finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK > > > again. INIT_WORK() will re-initialize the list pointers in the > > > work_struct, which then can result in a corrupted work list and the > > > work_struct queued a second time. With the work list corrupted, it can > > > lead in invalid work items being used and cause a crash in > > > process_one_work. > > > > > > We need to make sure only one flush bio can be handled at one same time. > > > So add spin lock in md_submit_flush_data to protect prev_flush_start and > > > flush_bio in an atomic way. > > > > > > Reviewed-by: David Jeffery > > > Signed-off-by: Xiao Ni > > > Signed-off-by: Song Liu > > > [jwang: backport dc5d17a3c39b06aef866afca19245a9cfb533a79 to 4.19] > > > Signed-off-by: Jack Wang > > > --- > > > drivers/md/md.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/drivers/md/md.c b/drivers/md/md.c > > > index ea139d0c0bc3..2bd60bd9e2ca 100644 > > > --- a/drivers/md/md.c > > > +++ b/drivers/md/md.c > > > @@ -639,8 +639,10 @@ static void md_submit_flush_data(struct work_struct *ws) > > > * could wait for this and below md_handle_request could wait for those > > > * bios because of suspend check > > > */ > > > + spin_lock_irq(&mddev->lock); > > > mddev->last_flush = mddev->start_flush; > > > mddev->flush_bio = NULL; > > > + spin_unlock_irq(&mddev->lock); > > > wake_up(&mddev->sb_wait); > > > > > > if (bio->bi_iter.bi_size == 0) { > > > -- > > > 2.25.1 > > > > Now queued up, thanks. > > > > greg k-h > Thanks, I see only this patch got applied. Do you have concern > regarding first 7 patches? I only see this one patch. Please resend anything else you wish to have applied as I think I said that I dropped everything you submitted before, right? thanks, greg k-h