From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f194.google.com ([209.85.128.194]:32861 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751413AbdGRS1q (ORCPT ); Tue, 18 Jul 2017 14:27:46 -0400 Received: by mail-wr0-f194.google.com with SMTP id y43so5461626wrd.0 for ; Tue, 18 Jul 2017 11:27:46 -0700 (PDT) Subject: Re: [PATCH, RFC] xfs: fix multi-AG deadlock in xfs_bunmapi References: <20170718172545.18065-1-hch@lst.de> <20170718181535.GJ4224@magnolia> From: Nikolay Borisov Message-ID: Date: Tue, 18 Jul 2017 21:27:43 +0300 MIME-Version: 1.0 In-Reply-To: <20170718181535.GJ4224@magnolia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" , Christoph Hellwig Cc: linux-xfs@vger.kernel.org On 18.07.2017 21:15, Darrick J. Wong wrote: > On Tue, Jul 18, 2017 at 07:25:45PM +0200, Christoph Hellwig wrote: >> Just like in the allocator we must avoid touching multiple AGs out of >> order when freeing blocks, as freeing still locks the AGF and can cause >> the same AB-BA deadlocks as in the allocation path. >> >> Signed-off-by: Christoph Hellwig >> Reported-by: Nikolay Borisov > > Looks ok, though I wonder what the bug report looked like. :) https://www.spinics.net/lists/linux-xfs/msg05918.html > > Reviewed-by: Darrick J. Wong > >> --- >> fs/xfs/libxfs/xfs_bmap.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c >> index 0a9880777c9c..935adde72a8b 100644 >> --- a/fs/xfs/libxfs/xfs_bmap.c >> +++ b/fs/xfs/libxfs/xfs_bmap.c >> @@ -5435,6 +5435,7 @@ __xfs_bunmapi( >> xfs_fsblock_t sum; >> xfs_filblks_t len = *rlen; /* length to unmap in file */ >> xfs_fileoff_t max_len; >> + xfs_agnumber_t prev_agno = NULLAGNUMBER, agno; >> >> trace_xfs_bunmap(ip, bno, len, flags, _RET_IP_); >> >> @@ -5534,6 +5535,17 @@ __xfs_bunmapi( >> */ >> del = got; >> wasdel = isnullstartblock(del.br_startblock); >> + >> + /* >> + * Make sure we don't touch multiple AGF headers out of order >> + * in a single transaction, as that could cause AB-BA deadlocks. >> + */ >> + if (!wasdel) { >> + agno = XFS_FSB_TO_AGNO(mp, del.br_startblock); >> + if (prev_agno != NULLAGNUMBER && prev_agno > agno) >> + break; >> + prev_agno = agno; >> + } >> if (got.br_startoff < start) { >> del.br_startoff = start; >> del.br_blockcount -= start - got.br_startoff; >> -- >> 2.11.0 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html