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 CEB03ECAAA1 for ; Tue, 30 Aug 2022 13:52:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231303AbiH3NwP (ORCPT ); Tue, 30 Aug 2022 09:52:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231307AbiH3Nvz (ORCPT ); Tue, 30 Aug 2022 09:51:55 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8CDE4BA52; Tue, 30 Aug 2022 06:50:09 -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 42EBAB81C07; Tue, 30 Aug 2022 13:50:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CB94FC433D6; Tue, 30 Aug 2022 13:50:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661867405; bh=l7ELeaRTVCV4lo7/FQ0h0/nHSZnx9Fi3ScrPGF9gzvs=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=aWStCZCicrMebcTCOFe7sxaeIJUPqBAwUaEf0+CLgJ2SV1vBL9kIWVDHMZrU6a+FW b9wM+EAjmMpBpn68zTuq/Oc0sLAIkrPOV+QuNAE61dO12HJ9cNoU5YwvQCyrQwHtJ7 d5miBia6XH86fk/Zk+SFdI0Ce87PENiBZeWTSL60/FGV0QGbue6pCsXGB9n4quAWcI diZUKu5+Q0tiqX/QvnQ7X1MLf6ovVGhsyD0xQoz0v6rDTjBxAj4y0SRS20V1pvAcCa QcGZgRLg2BYoUiNkCzqa/HtZVKnjjHnLKkcfSm7HbwD3G/MyLvhdJELzoBaofQajzk T7OMDrGENU0IQ== Message-ID: Subject: Re: [PATCH v3 1/7] iversion: update comments with info about atime updates From: Jeff Layton To: "J. Bruce Fields" Cc: NeilBrown , Dave Chinner , tytso@mit.edu, adilger.kernel@dilger.ca, djwong@kernel.org, trondmy@hammerspace.com, viro@zeniv.linux.org.uk, zohar@linux.ibm.com, xiubli@redhat.com, chuck.lever@oracle.com, lczerner@redhat.com, jack@suse.cz, brauner@kernel.org, linux-api@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ceph@vger.kernel.org, linux-ext4@vger.kernel.org, linux-nfs@vger.kernel.org, linux-xfs@vger.kernel.org, Colin Walters Date: Tue, 30 Aug 2022 09:50:02 -0400 In-Reply-To: <20220830132443.GA26330@fieldses.org> References: <20220826214703.134870-1-jlayton@kernel.org> <20220826214703.134870-2-jlayton@kernel.org> <20220829075651.GS3600936@dread.disaster.area> <549776abfaddcc936c6de7800b6d8249d97d9f28.camel@kernel.org> <166181389550.27490.8200873228292034867@noble.neil.brown.name> <20220830132443.GA26330@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 Tue, 2022-08-30 at 09:24 -0400, J. Bruce Fields wrote: > On Tue, Aug 30, 2022 at 07:40:02AM -0400, Jeff Layton wrote: > > Yes, saying only that it must be different is intentional. What we > > really want is for consumers to treat this as an opaque value for the > > most part [1]. Therefore an implementation based on hashing would > > conform to the spec, I'd think, as long as all of the relevant info is > > part of the hash. >=20 > It'd conform, but it might not be as useful as an increasing value. >=20 > E.g. a client can use that to work out which of a series of reordered > write replies is the most recent, and I seem to recall that can prevent > unnecessary invalidations in some cases. >=20 That's a good point; the linux client does this. That said, NFSv4 has a way for the server to advertise its change attribute behavior [1] (though nfsd hasn't implemented this yet). We don't have a good way to do that in userland for now. This is another place where fsinfo() would have been nice to have. I think until we have something like that, we'd want to keep our promises to userland to a minimum. [1]: https://www.rfc-editor.org/rfc/rfc7862.html#section-12.2.3 . I guess I should look at plumbing this in for IS_I_VERSION inodes... --=20 Jeff Layton