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 7AF76C433DB for ; Mon, 8 Feb 2021 12:46:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36EC664E42 for ; Mon, 8 Feb 2021 12:46:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232599AbhBHMqK (ORCPT ); Mon, 8 Feb 2021 07:46:10 -0500 Received: from mail.kernel.org ([198.145.29.99]:50528 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232430AbhBHMp6 (ORCPT ); Mon, 8 Feb 2021 07:45:58 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5A91364E75; Mon, 8 Feb 2021 12:45:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612788316; bh=ifobcqNo6vcc1rN286jX0rDurugavttR0zGgFnndxJc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZabfLnCfWboDagFh79lmOMVM+OrOKo/UCF/y6QKsZ4+6j7wxciY+YxaHlKW/i107j rAAnOR3B6JIkry3ZkGEcrhEijpEg4UCtgpNn6Z7/+AEQaCQvx3Jh2fmSZQEoITz8ZO AuVrvNEltcrZSto+htnos71mPdfLSH6irIGjbt8I= Date: Mon, 8 Feb 2021 13:45:14 +0100 From: Greg KH To: Jack Wang Cc: sashal@kernel.org, stable@vger.kernel.org, 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: <20210205141301.71682-1-jinpu.wang@cloud.ionos.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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