From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751667AbeBRSMY (ORCPT ); Sun, 18 Feb 2018 13:12:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:57162 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751532AbeBRSMX (ORCPT ); Sun, 18 Feb 2018 13:12:23 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7947E2171F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=shli@kernel.org Date: Sun, 18 Feb 2018 10:12:21 -0800 From: Shaohua Li To: Heinz Mauelshagen Cc: dm-devel@redhat.com, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: [PATCH] md: fix md_write_start() deadlock w/o metadata devices Message-ID: <20180218181221.a5l5nzgav7s6smor@kernel.org> References: <054eff295e0cd2df2b11a3f9ba3b3d66e89beb47.1517609290.git.heinzm@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <054eff295e0cd2df2b11a3f9ba3b3d66e89beb47.1517609290.git.heinzm@redhat.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 02, 2018 at 11:13:19PM +0100, Heinz Mauelshagen wrote: > If no metadata devices are configured on raid1/4/5/6/10 > (e.g. via dm-raid), md_write_start() unconditionally waits > for superblocks to be written thus deadlocking. > > Fix introduces mddev->has_superblocks bool, defines it in md_run() > and checks for it in md_write_start() to conditionally avoid waiting. > > Once on it, check for non-existing superblocks in md_super_write(). > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=198647 > Fixes: cc27b0c78c796 ("md: fix deadlock between mddev_suspend() and md_write_start()") Applied, thanks! > Signed-off-by: Heinz Mauelshagen > --- > drivers/md/md.c | 10 ++++++++++ > drivers/md/md.h | 2 ++ > 2 files changed, 12 insertions(+) > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index 0081ace39a64..8a7e7034962c 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -801,6 +801,9 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev, > struct bio *bio; > int ff = 0; > > + if (!page) > + return; > + > if (test_bit(Faulty, &rdev->flags)) > return; > > @@ -5452,6 +5455,7 @@ int md_run(struct mddev *mddev) > * the only valid external interface is through the md > * device. > */ > + mddev->has_superblocks = false; > rdev_for_each(rdev, mddev) { > if (test_bit(Faulty, &rdev->flags)) > continue; > @@ -5465,6 +5469,9 @@ int md_run(struct mddev *mddev) > set_disk_ro(mddev->gendisk, 1); > } > > + if (rdev->sb_page) > + mddev->has_superblocks = true; > + > /* perform some consistency tests on the device. > * We don't want the data to overlap the metadata, > * Internal Bitmap issues have been handled elsewhere. > @@ -8049,6 +8056,7 @@ EXPORT_SYMBOL(md_done_sync); > bool md_write_start(struct mddev *mddev, struct bio *bi) > { > int did_change = 0; > + > if (bio_data_dir(bi) != WRITE) > return true; > > @@ -8081,6 +8089,8 @@ bool md_write_start(struct mddev *mddev, struct bio *bi) > rcu_read_unlock(); > if (did_change) > sysfs_notify_dirent_safe(mddev->sysfs_state); > + if (!mddev->has_superblocks) > + return true; > wait_event(mddev->sb_wait, > !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) || > mddev->suspended); > diff --git a/drivers/md/md.h b/drivers/md/md.h > index 58cd20a5e85e..fbc925cce810 100644 > --- a/drivers/md/md.h > +++ b/drivers/md/md.h > @@ -468,6 +468,8 @@ struct mddev { > void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev); > struct md_cluster_info *cluster_info; > unsigned int good_device_nr; /* good device num within cluster raid */ > + > + bool has_superblocks:1; > }; > > enum recovery_flags { > -- > 2.14.3 >