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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 C0CBFC34031 for ; Tue, 18 Feb 2020 21:52:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92C81207FD for ; Tue, 18 Feb 2020 21:52:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726482AbgBRVwt (ORCPT ); Tue, 18 Feb 2020 16:52:49 -0500 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:39406 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726481AbgBRVwt (ORCPT ); Tue, 18 Feb 2020 16:52:49 -0500 Received: from dread.disaster.area (pa49-179-138-28.pa.nsw.optusnet.com.au [49.179.138.28]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 873D47EA9E2; Wed, 19 Feb 2020 08:52:44 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1j4AnL-0003Oo-Hs; Wed, 19 Feb 2020 08:52:43 +1100 Date: Wed, 19 Feb 2020 08:52:43 +1100 From: Dave Chinner To: Brian Foster Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH v2] xfs: fix iclog release error check race with shutdown Message-ID: <20200218215243.GS10776@dread.disaster.area> References: <20200218175425.20598-1-bfoster@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200218175425.20598-1-bfoster@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=LYdCFQXi c=1 sm=1 tr=0 a=zAxSp4fFY/GQY8/esVNjqw==:117 a=zAxSp4fFY/GQY8/esVNjqw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=l697ptgUJYAA:10 a=20KFwNOVAAAA:8 a=VwQbUJbxAAAA:8 a=7-415B0cAAAA:8 a=3EkYcGV84Bsk_DNOYAkA:9 a=CjuIK1q_8ugA:10 a=AjGcO6oz07-iQ99wixmX:22 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Feb 18, 2020 at 12:54:25PM -0500, Brian Foster wrote: > Prior to commit df732b29c8 ("xfs: call xlog_state_release_iclog with > l_icloglock held"), xlog_state_release_iclog() always performed a > locked check of the iclog error state before proceeding into the > sync state processing code. As of this commit, part of > xlog_state_release_iclog() was open-coded into > xfs_log_release_iclog() and as a result the locked error state check > was lost. > > The lockless check still exists, but this doesn't account for the > possibility of a race with a shutdown being performed by another > task causing the iclog state to change while the original task waits > on ->l_icloglock. This has reproduced very rarely via generic/475 > and manifests as an assert failure in __xlog_state_release_iclog() > due to an unexpected iclog state. > > Restore the locked error state check in xlog_state_release_iclog() > to ensure that an iclog state update via shutdown doesn't race with > the iclog release state processing code. > > Fixes: df732b29c807 ("xfs: call xlog_state_release_iclog with l_icloglock held") > Reported-by: Zorro Lang > Signed-off-by: Brian Foster > --- > > v2: > - Include Fixes tag. > - Use common error path to include shutdown call. > v1: https://lore.kernel.org/linux-xfs/20200214181528.24046-1-bfoster@redhat.com/ > > fs/xfs/xfs_log.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > index f6006d94a581..796ff37d5bb5 100644 > --- a/fs/xfs/xfs_log.c > +++ b/fs/xfs/xfs_log.c > @@ -605,18 +605,23 @@ xfs_log_release_iclog( > struct xlog *log = mp->m_log; > bool sync; > > - if (iclog->ic_state == XLOG_STATE_IOERROR) { > - xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR); > - return -EIO; > - } hmmmm. xfs_force_shutdown() will does nothing if the iclog at the head of the log->iclog list is marked with XLOG_STATE_IOERROR before IO is submitted. In general, that is the case here as the head iclog is what xlog_state_get_iclog_space() returns. i.e. XLOG_STATE_IOERROR here implies the log has already been shut down because the state is IOERROR rather than ACTIVE or WANT_SYNC as was set when the iclog was obtained from xlog_state_get_iclog_space(). > + if (iclog->ic_state == XLOG_STATE_IOERROR) > + goto error; > > if (atomic_dec_and_lock(&iclog->ic_refcnt, &log->l_icloglock)) { > + if (iclog->ic_state == XLOG_STATE_IOERROR) { > + spin_unlock(&log->l_icloglock); > + goto error; > + } > sync = __xlog_state_release_iclog(log, iclog); > spin_unlock(&log->l_icloglock); > if (sync) > xlog_sync(log, iclog); > } > return 0; > +error: > + xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR); > + return -EIO; Hence I suspect that this should be ASSERT(XLOG_FORCED_SHUTDOWN(log)) just like is in xfs_log_force_umount() when this pre-existing log IO error condition is tripped over... Cheers, Dave. -- Dave Chinner david@fromorbit.com