From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaohua Li Subject: Re: [PATCH] raid1: include bio_end_io_list in nr_queued to prevent freeze_array hang Date: Sun, 6 Mar 2016 15:33:04 -0800 Message-ID: <20160306233304.GA3200@kernel.org> References: <1456760638-23936-1-git-send-email-nate.dailey@stratus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1456760638-23936-1-git-send-email-nate.dailey@stratus.com> Sender: linux-raid-owner@vger.kernel.org To: Nate Dailey Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Mon, Feb 29, 2016 at 10:43:58AM -0500, Nate Dailey wrote: > If raid1d is handling a mix of read and write errors, handle_read_error's > call to freeze_array can get stuck. > > This can happen because, though the bio_end_io_list is initially drained, > writes can be added to it via handle_write_finished as the retry_list > is processed. These writes contribute to nr_pending but are not included > in nr_queued. > > If a later entry on the retry_list triggers a call to handle_read_error, > freeze array hangs waiting for nr_pending == nr_queued+extra. The writes > on the bio_end_io_list aren't included in nr_queued so the condition will > never be satisfied. > > To prevent the hang, include bio_end_io_list writes in nr_queued. > > There's probably a better way to handle decrementing nr_queued, but this > seemed like the safest way to avoid breaking surrounding code. > > I'm happy to supply the script I used to repro this hang. Looks good. Could you please also fix raid10? Thanks, Shaohua