From patchwork Wed Sep 7 11:33:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 603375 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 DE225C6FA8E for ; Wed, 7 Sep 2022 11:33:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230120AbiIGLdg (ORCPT ); Wed, 7 Sep 2022 07:33:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230007AbiIGLd2 (ORCPT ); Wed, 7 Sep 2022 07:33:28 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 289D4B69FE; Wed, 7 Sep 2022 04:33:27 -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 90DADB81C54; Wed, 7 Sep 2022 11:33:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21A83C433D7; Wed, 7 Sep 2022 11:33:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1662550404; bh=pgdqISJ78hjl4jnmYpYl02FTsH6QtwIm0GzwJzLcJeo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jUc7JHz1Hr2VUZGmUY4B2Dzd5YyfayOVb2CGCl2Zf2UIARfJWnVLP+OXLTGgPO92g AhLkb5dQ9JbjsORHi2Ax36RR74jMzgvHINBHQI6UyFgf2jN5fn/63ipvLH4ra4ahtV skULuiwl0q3Wy+Vi1CS8FMxQupOejwnl6u4CtO5lcEv0x5O0a/y5xb1Zi/ewxZxXds jARtbume4Mw03XpbL02ybRsrBXOKeiXKY3NgiuX2Kny8KdaX6kWEtWVG7210oIERkE O/QczdmNwXrYTxn+O56xquvTObPPvgSm1Ujr2fWFDysoa2oMg1+MEm3g01n8Kp6hhR kOEgcTuiayIdA== 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, fweimer@redhat.com 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, Colin Walters Subject: [PATCH v4 1/6] iversion: update comments with info about atime updates Date: Wed, 7 Sep 2022 07:33:13 -0400 Message-Id: <20220907113318.21810-2-jlayton@kernel.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220907113318.21810-1-jlayton@kernel.org> References: <20220907113318.21810-1-jlayton@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org The i_version field in the kernel has had different semantics over the decades, but we're now proposing to expose it to userland via statx. This means that we need a clear, consistent definition of what it means and when it should change. Update the comments in iversion.h to describe when the i_version must change. Cc: Colin Walters Cc: NeilBrown Cc: Trond Myklebust Cc: Dave Chinner Link: https://lore.kernel.org/linux-xfs/166086932784.5425.17134712694961326033@noble.neil.brown.name/#t Signed-off-by: Jeff Layton --- include/linux/iversion.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/include/linux/iversion.h b/include/linux/iversion.h index 3bfebde5a1a6..0555a3851dbf 100644 --- a/include/linux/iversion.h +++ b/include/linux/iversion.h @@ -9,8 +9,14 @@ * --------------------------- * The change attribute (i_version) is mandated by NFSv4 and is mostly for * knfsd, but is also used for other purposes (e.g. IMA). The i_version must - * appear different to observers if there was a change to the inode's data or - * metadata since it was last queried. + * appear larger to observers if there was an explicit change to the inode's + * data or metadata since it was last queried. + * + * An explicit change is one that would ordinarily result in a change to the + * inode status change time (aka ctime). i_version must appear to change, even + * if the ctime does not (since the whole point is to avoid missing updates due + * to timestamp granularity). If POSIX mandates that the ctime must change due + * to an operation, then the i_version counter must be incremented as well. * * Observers see the i_version as a 64-bit number that never decreases. If it * remains the same since it was last checked, then nothing has changed in the