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=-4.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=no 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 07F9CC433E1 for ; Mon, 24 Aug 2020 02:43:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D37D0206F7 for ; Mon, 24 Aug 2020 02:43:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="vs5dk/WU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726904AbgHXCnz (ORCPT ); Sun, 23 Aug 2020 22:43:55 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:46380 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726737AbgHXCnz (ORCPT ); Sun, 23 Aug 2020 22:43:55 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 07O2hjJP137572; Mon, 24 Aug 2020 02:43:45 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2020-01-29; bh=jmEc7LEX72M9J+SWhhgI/bXZ1snMJxDO6mGt0Wu/CL8=; b=vs5dk/WUlBPLcxqPSBcy5iJ/8NOSs2h2nCEZnpFH8jIGitSSsH56ZEjSUrIAgOabhyvv s856cuoefe1+KB8NL/5MnhFcmkF4nrVzpLf+p5F7FYEA1cty6qKk6L8T/WS6QXhORSP8 PcHtcYqWWkSOgVTGmf4urzItzfs4sVU+8GKOskO6Ts9Mat1rBM9/MI1r4w3lbdKEGDqE FJ9Zc0kZrA3529pWQpvsauerl66O4tW80BSHRhNyNudBvj3rwfn41HGLswmV8IJTIOfP VN1R48/m+nfMeJCfuBtKH4zCgl30ZZ561qlOmgGdCSplwgXELCRTHEiyNAgXnpEtj4Vf lg== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2120.oracle.com with ESMTP id 333dbrj38n-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 24 Aug 2020 02:43:45 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 07O2eVv8145172; Mon, 24 Aug 2020 02:43:44 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userp3020.oracle.com with ESMTP id 333rtvvege-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 24 Aug 2020 02:43:44 +0000 Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 07O2hgvw029153; Mon, 24 Aug 2020 02:43:43 GMT Received: from localhost (/10.159.140.7) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Sun, 23 Aug 2020 19:43:42 -0700 Date: Sun, 23 Aug 2020 19:43:41 -0700 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Amir Goldstein , linux-xfs@vger.kernel.org, sandeen@sandeen.net Subject: Re: [PATCH 08/11] xfs: widen ondisk timestamps to deal with y2038 problem Message-ID: <20200824024341.GT6096@magnolia> References: <159797588727.965217.7260803484540460144.stgit@magnolia> <159797594159.965217.2504039364311840477.stgit@magnolia> <20200822073319.GH1629@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200822073319.GH1629@infradead.org> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9722 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 adultscore=0 phishscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008240010 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9722 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 phishscore=0 malwarescore=0 mlxlogscore=999 spamscore=0 mlxscore=0 lowpriorityscore=0 suspectscore=1 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008240010 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Sat, Aug 22, 2020 at 08:33:19AM +0100, Christoph Hellwig wrote: > > * in the AGI header so that we can skip the finobt walk at mount time when > > @@ -855,12 +862,18 @@ struct xfs_agfl { > > * > > * Inode timestamps consist of signed 32-bit counters for seconds and > > * nanoseconds; time zero is the Unix epoch, Jan 1 00:00:00 UTC 1970. > > + * > > + * When bigtime is enabled, timestamps become an unsigned 64-bit nanoseconds > > + * counter. Time zero is the start of the classic timestamp range. > > */ > > union xfs_timestamp { > > struct { > > __be32 t_sec; /* timestamp seconds */ > > __be32 t_nsec; /* timestamp nanoseconds */ > > }; > > + > > + /* Nanoseconds since the bigtime epoch. */ > > + __be64 t_bigtime; > > }; > > So do we really need the union here? What about: > > (1) keep the typedef instead of removing it > (2) switch the typedef to be just a __be64, and use trivial helpers > to extract the two separate legacy sec/nsec field > (3) PROFIT!!! Been there, done that. Dave suggested some replacement code (which corrupted the values), then I modified that into a correct version, which then made smatch angry because it doesn't like code that does bit shifts on __be64 values. > > +/* Convert an ondisk timestamp into the 64-bit safe incore format. */ > > void > > xfs_inode_from_disk_timestamp( > > + struct xfs_dinode *dip, > > struct timespec64 *tv, > > const union xfs_timestamp *ts) > > I think passing ts by value might lead to somewhat better code > generation on modern ABIs (and older ABIs just fall back to pass > by reference transparently). Hm, ok. I did not know that. :) > > { > > + if (dip->di_version >= 3 && > > + (dip->di_flags2 & cpu_to_be64(XFS_DIFLAG2_BIGTIME))) { > > Do we want a helper for this condition? Yes, yes we do. Will add. > > + uint64_t t = be64_to_cpu(ts->t_bigtime); > > + uint64_t s; > > + uint32_t n; > > + > > + s = div_u64_rem(t, NSEC_PER_SEC, &n); > > + tv->tv_sec = s - XFS_INO_BIGTIME_EPOCH; > > + tv->tv_nsec = n; > > + return; > > + } > > + > > tv->tv_sec = (int)be32_to_cpu(ts->t_sec); > > tv->tv_nsec = (int)be32_to_cpu(ts->t_nsec); > > Nit: for these kinds of symmetric conditions and if/else feels a little > more natural. > > > + xfs_log_dinode_to_disk_ts(from, &to->di_crtime, &from->di_crtime); > > This adds a > 80 char line. Do we care now that checkpatch has been changed to allow up to 100 columns? > > + if (from->di_flags2 & XFS_DIFLAG2_BIGTIME) { > > + uint64_t t; > > + > > + t = (uint64_t)(ts->tv_sec + XFS_INO_BIGTIME_EPOCH); > > + t *= NSEC_PER_SEC; > > + its->t_bigtime = t + ts->tv_nsec; > > This calculation is dupliated in two places, might be worth > adding a little helper (which will need to get the sec/nsec values > passed separately due to the different structures). > > > + xfs_inode_to_log_dinode_ts(from, &to->di_crtime, &from->di_crtime); > > Another line over 8 characters here. > > > + if (xfs_sb_version_hasbigtime(&mp->m_sb)) { > > + sb->s_time_min = XFS_INO_BIGTIME_MIN; > > + sb->s_time_max = XFS_INO_BIGTIME_MAX; > > + } else { > > + sb->s_time_min = XFS_INO_TIME_MIN; > > + sb->s_time_max = XFS_INO_TIME_MAX; > > + } > > This is really a comment on the earlier patch, but maybe we should > name the old constants with "OLD" or "LEGACY" or "SMALL" in the name? Yes, good suggestion! > > @@ -1494,6 +1499,10 @@ xfs_fc_fill_super( > > if (XFS_SB_VERSION_NUM(&mp->m_sb) == XFS_SB_VERSION_5) > > sb->s_flags |= SB_I_VERSION; > > > > + if (xfs_sb_version_hasbigtime(&mp->m_sb)) > > + xfs_warn(mp, > > + "EXPERIMENTAL big timestamp feature in use. Use at your own risk!"); > > + > > Is there any good reason to mark this experimental? As you and Dave have both pointed out, there are plenty of stupid bugs still in this. I think I'd like to have at least one EXPERIMENTAL cycle to make sure I didn't commit anything pathologically stupid in here. ext4 34-bit sign extension bug . --D