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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84299C4332F for ; Tue, 31 Oct 2023 10:26:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BFF346B02CB; Tue, 31 Oct 2023 06:26:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BADCC6B02CC; Tue, 31 Oct 2023 06:26:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A9CEC6B02CD; Tue, 31 Oct 2023 06:26:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 9AC856B02CB for ; Tue, 31 Oct 2023 06:26:34 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 597EE120B31 for ; Tue, 31 Oct 2023 10:26:34 +0000 (UTC) X-FDA: 81405377508.22.1682BFA Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf07.hostedemail.com (Postfix) with ESMTP id 9D3864000F for ; Tue, 31 Oct 2023 10:26:32 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=CBQ79pKp; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf07.hostedemail.com: domain of brauner@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=brauner@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1698747992; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qPB5AWv9l8vKQjg/DIgSxzR/673lWyQaSFjRURIuY2Y=; b=KH3JC35K4LD/sEr9u2m8JwwOzeVbt8+9BiIawype4ruxJja+0k/Ou7BHBmD9g64wkYlz0g KRWM0zlBy9x8EPSxJZrpeJfZCbDuftwg5hL+x914zkQXO1JSix5E8+Dju/Agg6cRjPJU3s iAGh9kx/WlFjywG+vLUrbE+b07rNf7M= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=CBQ79pKp; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf07.hostedemail.com: domain of brauner@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=brauner@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1698747992; a=rsa-sha256; cv=none; b=uLNf8vehMyQC3pE6TLCdidImYhXSTRg3YA5+PjdzJlufDd/JcqGqcDclqj7vgF+gvoAIhl +0Zm1TrK4aSr96wRclK459awIAWkMC3KV4SKvnMEwpaqw3ewiTnV+eOZpho0JFRDpcWtSc N+HJbt+EMQ4QBOGOlzWFcKvpWmvmY6I= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 6CFC860EC0; Tue, 31 Oct 2023 10:26:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A722C433CD; Tue, 31 Oct 2023 10:26:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698747991; bh=oub4W8UR9eJvRxgd0x2K3FAODzLnOQX75kkj3Rb+xzQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CBQ79pKptpDj7180sdV3SpAcAZvHyawpezclc+dj2iFMxLVXbCbeH5YfqE4WcuoSQ /IEC+3qoroTC2lIkVBcGC1DX6llrEm61HMJO99f+TerLtsheVQsLE9AfPYgLhim3il BwxCV8atgTPe56WKD61JOc4sLVO6kH2+d24WzaTAZ7BS3WWrCrsQF+tGOsjU+AaLRA sYchDKCcENZca1LRCxGxYqUCuu6xVqJq2heeguzA/O1G/LaEcErOyMUJBqHuHm/NWG odXeR9D7iD7TDRylyP2HU+NvC56rx+jfWJiWfYSK0levv1XvEdMBDZqRx+QV8N29Ze bO3o0pYhWGntQ== Date: Tue, 31 Oct 2023 11:26:22 +0100 From: Christian Brauner To: Jeff Layton Cc: Linus Torvalds , Alexander Viro , John Stultz , Thomas Gleixner , Stephen Boyd , Chandan Babu R , "Darrick J. Wong" , Dave Chinner , Theodore Ts'o , Andreas Dilger , Chris Mason , Josef Bacik , David Sterba , Hugh Dickins , Andrew Morton , Amir Goldstein , Jan Kara , David Howells , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH RFC 2/9] timekeeping: new interfaces for multigrain timestamp handing Message-ID: <20231031-stark-klar-0bab5f9ab4dc@brauner> References: <20231018-mgtime-v1-0-4a7a97b1f482@kernel.org> <20231018-mgtime-v1-2-4a7a97b1f482@kernel.org> <5f96e69d438ab96099bb67d16b77583c99911caa.camel@kernel.org> <20231019-fluor-skifahren-ec74ceb6c63e@brauner> <0a1a847af4372e62000b259e992850527f587205.camel@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <0a1a847af4372e62000b259e992850527f587205.camel@kernel.org> X-Rspamd-Queue-Id: 9D3864000F X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: tgpsuj7jc76degaex3szbmz48rbmojg4 X-HE-Tag: 1698747992-134029 X-HE-Meta: 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 D7tJRTvl Ncvvm8HWkVnmeLjTC8BoM+LC4bZXiDxLpXmrEuY+bwjmqkF1tXlTPK/9PU+ENQZCpgYRSp812RoV+NRZ1+Y2pHP6YBhQYthfre7qtfOPT0imTUaIAOTVVJr7PgDTbkeDDhKc6HF18/21wXw4qT2wlevVqXRQl4VzHZbclUrx0S7SvV0cadcdM7D1/YP41wPBLuMnZ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Oct 19, 2023 at 07:28:48AM -0400, Jeff Layton wrote: > On Thu, 2023-10-19 at 11:29 +0200, Christian Brauner wrote: > > > Back to your earlier point though: > > > > > > Is a global offset really a non-starter? I can see about doing something > > > per-superblock, but ktime_get_mg_coarse_ts64 should be roughly as cheap > > > as ktime_get_coarse_ts64. I don't see the downside there for the non- > > > multigrain filesystems to call that. > > > > I have to say that this doesn't excite me. This whole thing feels a bit > > hackish. I think that a change version is the way more sane way to go. > > > > What is it about this set that feels so much more hackish to you? Most > of this set is pretty similar to what we had to revert. Is it just the > timekeeper changes? Why do you feel those are a problem? So I think that the multi-grain timestamp work was well intended but it was ultimately a mistake. Because we added code that complicated timestamp timestamp handling in the vfs to a point where the costs clearly outweighed the benefits. And I don't think that this direction is worth going into. This whole thread ultimately boils down to complicating generic infrastructure quite extensively for nfs to handle exposing xfs without forcing an on-disk format change. That's even fine. That's not a problem but in the same way I don't think the solution is just stuffing this complexity into the vfs. IOW, if we make this a vfs problem then at the lowest possible cost and not by changing how timestamps work for everyone even if it's just internal.