From patchwork Thu Sep 1 12:17:14 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 12962396 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 B85EAC0502C for ; Thu, 1 Sep 2022 12:17:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233161AbiIAMRX (ORCPT ); Thu, 1 Sep 2022 08:17:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232868AbiIAMRW (ORCPT ); Thu, 1 Sep 2022 08:17:22 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CC006118A63; Thu, 1 Sep 2022 05:17:20 -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 3C462B825E4; Thu, 1 Sep 2022 12:17:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E8490C433D6; Thu, 1 Sep 2022 12:17:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1662034638; bh=HMRBvtGrMdseHHO8WD6RRw3JemO/uRhitrcEcBh7oNk=; h=From:To:Cc:Subject:Date:From; b=JI38jC2mevkX/4GtWpVjQre7XaNbn7VhZ+Rkhr5IpRF7UZvDH5XtH3JLJL8qdirl+ Cj7CH8pj40ihyuVu6GQF/Bf3e0VZ6/LxPC2yXycJopLmTWI4Xtxhqk40NqrnQtVg8d zi3zvxmPfRS1JLpJa9fMCqGzXhOvcXClFUvpC2yevjgLyZk2PVOyOkCCp6EQS+9pHE ZDN1pjgpUw+le3WE/VmsnR5pEkX47pYbZMgTwMHBy6KCf3+8pjTkYGbk6lmWCviG7f vbGIubjeVMuSqwdxdutaaV/Il3IrzTukDESCtg5R7nLPG3wi+Qh9yEvTIxxtwAZsy+ uF5I3/4+RPJ4A== From: Jeff Layton To: tytso@mit.edu, adilger.kernel@dilger.ca, djwong@kernel.org, david@fromorbit.com, trondmy@hammerspace.com, neilb@suse.de, viro@zeniv.linux.org.uk, zohar@linux.ibm.com, xiubli@redhat.com, chuck.lever@oracle.com, lczerner@redhat.com, jack@suse.cz, bfields@fieldses.org, brauner@kernel.org, linux-man@vger.kernel.org Cc: 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 Subject: [RFC PATCH v2] statx, inode: document the new STATX_INO_VERSION field Date: Thu, 1 Sep 2022 08:17:14 -0400 Message-Id: <20220901121714.20051-1-jlayton@kernel.org> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org I'm proposing to expose the inode change attribute via statx [1]. Document what this value means and what an observer can infer from it changing. Signed-off-by: Jeff Layton [1]: https://lore.kernel.org/linux-nfs/20220826214703.134870-1-jlayton@kernel.org/T/#t --- man2/statx.2 | 17 +++++++++++++++++ man7/inode.7 | 12 ++++++++++++ 2 files changed, 29 insertions(+) v2: revised the definition to be more strict, since that seemed to be consensus on desired behavior. Spurious i_version bumps would now be considered bugs, by this definition. diff --git a/man2/statx.2 b/man2/statx.2 index 0d1b4591f74c..493e4e234809 100644 --- a/man2/statx.2 +++ b/man2/statx.2 @@ -62,6 +62,7 @@ struct statx { __u32 stx_dev_major; /* Major ID */ __u32 stx_dev_minor; /* Minor ID */ __u64 stx_mnt_id; /* Mount ID */ + __u64 stx_ino_version; /* Inode change attribute */ }; .EE .in @@ -247,6 +248,7 @@ STATX_BTIME Want stx_btime STATX_ALL The same as STATX_BASIC_STATS | STATX_BTIME. It is deprecated and should not be used. STATX_MNT_ID Want stx_mnt_id (since Linux 5.8) +STATX_INO_VERSION Want stx_ino_version (DRAFT) .TE .in .PP @@ -411,6 +413,21 @@ and corresponds to the number in the first field in one of the records in For further information on the above fields, see .BR inode (7). .\" +.TP +.I stx_ino_version +The inode version, also known as the inode change attribute. This +value must change any time there is an inode status change. Any +operation that would cause the +.I stx_ctime +to change must also cause +.I stx_ino_version +to change, even when there is no apparent change to the +.I stx_ctime +due to coarse timestamp granularity. +.IP +An observer cannot infer anything about the nature or magnitude of the change +from the value of this field. A change in this value only indicates that +there has been an explicit change in the inode. .SS File attributes The .I stx_attributes diff --git a/man7/inode.7 b/man7/inode.7 index 9b255a890720..d5e0890a52c0 100644 --- a/man7/inode.7 +++ b/man7/inode.7 @@ -184,6 +184,18 @@ Last status change timestamp (ctime) This is the file's last status change timestamp. It is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.). +.TP +Inode version (i_version) +(not returned in the \fIstat\fP structure); \fIstatx.stx_ino_version\fP +.IP +This is the inode change attribute. Any operation that would result in a change +to \fIstatx.stx_ctime\fP must result in a change to this value. The value must +change even in the case where the ctime change is not evident due to coarse +timestamp granularity. +.IP +An observer cannot infer anything from the returned value about the nature or +magnitude of the change. If the returned value is different from the last time +it was checked, then something has made an explicit change to the inode. .PP The timestamp fields report time measured with a zero point at the .IR Epoch ,