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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04745ECAAD5 for ; Mon, 12 Sep 2022 14:02:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229945AbiILOCh (ORCPT ); Mon, 12 Sep 2022 10:02:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56154 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229764AbiILOCf (ORCPT ); Mon, 12 Sep 2022 10:02:35 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D26931DF7; Mon, 12 Sep 2022 07:02:34 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 55620B80D55; Mon, 12 Sep 2022 14:02:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C12BDC433D7; Mon, 12 Sep 2022 14:02:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1662991350; bh=CJr3xwvNDLqpU75iwXI4nimkb371IeI9yF6/g36e4xc=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=N1nOlaRpf2JgDjhUFohphJn0WEbiK2kjJ26VaR9g4S5wHF2HOFtBsFk/2T0nXBph7 77ibhHYqpi3L6XnjzmPh//mHS2Lg5SslT7sj+yslZc8YFPDPcjTumTUL2w9WPW7OFR ftYUFI2lqrKbP35Bn4c5rnjobP2zddXr4QSR+0gCoI10pBxFj5bhOK+kISSJ0GCcM/ +TKchp8rwoV4O9RbRNkPOrt/vl3g9S4zAofpbEG5hLuuh0hQKYt2c6vJkPZWnOv2Yq qsuylp4XPZcB4gkt7uTDSyigrW6sr28/mZGFZTJai5QQu7GOvbQT8p5m5xgzm4NEvW kfXn2hX9ZIvGQ== Message-ID: <1abae98579030d437224ae24f73fffaabb3f64c1.camel@kernel.org> Subject: Re: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field From: Jeff Layton To: "J. Bruce Fields" Cc: Florian Weimer , Theodore Ts'o , Jan Kara , NeilBrown , adilger.kernel@dilger.ca, djwong@kernel.org, david@fromorbit.com, trondmy@hammerspace.com, viro@zeniv.linux.org.uk, zohar@linux.ibm.com, xiubli@redhat.com, chuck.lever@oracle.com, lczerner@redhat.com, brauner@kernel.org, linux-man@vger.kernel.org, linux-api@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ceph-devel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-nfs@vger.kernel.org, linux-xfs@vger.kernel.org Date: Mon, 12 Sep 2022 10:02:27 -0400 In-Reply-To: <20220912135131.GC9304@fieldses.org> References: <20220908155605.GD8951@fieldses.org> <9e06c506fd6b3e3118da0ec24276e85ea3ee45a1.camel@kernel.org> <20220908182252.GA18939@fieldses.org> <44efe219dbf511492b21a653905448d43d0f3363.camel@kernel.org> <20220909154506.GB5674@fieldses.org> <125df688dbebaf06478b0911e76e228e910b04b3.camel@kernel.org> <20220910145600.GA347@fieldses.org> <9eaed9a47d1aef11fee95f0079e302bc776bc7ff.camel@kernel.org> <87a67423la.fsf@oldenburg.str.redhat.com> <7c71050e139a479e08ab7cf95e9e47da19a30687.camel@kernel.org> <20220912135131.GC9304@fieldses.org> Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.4 (3.44.4-1.fc36) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Mon, 2022-09-12 at 09:51 -0400, J. Bruce Fields wrote: > On Mon, Sep 12, 2022 at 08:55:04AM -0400, Jeff Layton wrote: > > Because of the "seen" flag, we have a 63 bit counter to play with. Coul= d > > we use a similar scheme to the one we use to handle when "jiffies" > > wraps?=A0Assume that we'd never compare two values that were more than > > 2^62 apart? We could add i_version_before/i_version_after macros to mak= e > > it simple to handle this. >=20 > As far as I recall the protocol just assumes it can never wrap. I guess > you could add a new change_attr_type that works the way you describe. > But without some new protocol clients aren't going to know what to do > with a change attribute that wraps. >=20 Right, I think that's the case now, and with contemporary hardware that shouldn't ever happen, but in 10 years when we're looking at femtosecond latencies, could this be different? I don't know. > I think this just needs to be designed so that wrapping is impossible in > any realistic scenario. I feel like that's doable? >=20 > If we feel we have to catch that case, the only 100% correct behavior > would probably be to make the filesystem readonly. What would be the recourse at that point? Rebuild the fs from scratch, I guess? --=20 Jeff Layton