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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BB485E743D3 for ; Fri, 29 Sep 2023 00:35:57 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=ryWGGERq; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4RxWbw2y3Bz3cb9 for ; Fri, 29 Sep 2023 10:35:56 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=ryWGGERq; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=145.40.73.55; helo=sin.source.kernel.org; envelope-from=djwong@kernel.org; receiver=lists.ozlabs.org) Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4RxKwf47vgz3cVj; Fri, 29 Sep 2023 03:19:46 +1000 (AEST) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id C13F2CE2245; Thu, 28 Sep 2023 17:19:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE2E8C433C8; Thu, 28 Sep 2023 17:19:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695921584; bh=TBXriEELB328eOKqJ6NFSOrKvuSXYJvHz6sohZrQIx0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ryWGGERqf3ypGjqQYm5gVKZvkucKGUk0K4h6YIIWQ/NpKuXJi36HQDWjgdgtJd7wu TP/RvT38TPj/OA2Jk4aeD0DGoa7LAN7jIOlBWE0I1eYn6imAEKifbbeaG59NKi/slD aEVjDaHe+6Tji3j/v0JkIDO2dR6Fo6pHy84G4o5KxjxBslGp0LwydCJH4NJcX4DsY2 2+Ki57CRL6p89OjFpqSqXlcve39ZEqPDxD7QZyCHUVk8IqPpmvXHWivOQJXeNPWNjx piSViGDp1oRPgjAY21DvqURTHMn9e50dg1rgKW7SErtrbVvTXl75DArwoAJ6zoDjTa 8X72loIt6il5Q== Date: Thu, 28 Sep 2023 10:19:43 -0700 From: "Darrick J. Wong" To: Jeff Layton Subject: Re: [PATCH 86/87] fs: switch timespec64 fields in inode to discrete integers Message-ID: <20230928171943.GK11439@frogsfrogsfrogs> References: <20230928110554.34758-1-jlayton@kernel.org> <20230928110554.34758-2-jlayton@kernel.org> <6020d6e7-b187-4abb-bf38-dc09d8bd0f6d@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mailman-Approved-At: Fri, 29 Sep 2023 10:31:49 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Latchesar Ionkov , Konstantin Komarov , "Rafael J . Wysocki" , Hugh Dickins , Anders Larsen , Carlos Llamas , Andrii Nakryiko , Mattia Dongili , John Johansen , Yonghong Song , Alexander Gordeev , Christoph Hellwig , Mike Marshall , Paulo Alcantara , linux-xfs@vger.kernel.org, James Morris , Christoph Hellwig , Christian Borntraeger , devel@lists.orangefs.org, Shyam Prasad N , linux-um@lists.infradead.org, Nicholas Piggin , Alexander Viro , Eric Van Hensbergen , Suren Baghdasaryan , Trond Myklebust , Anton Altaparmakov , Christian Brauner , Greg Kroah-Hartman , Stephen Smalley , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Ronnie Sahlberg , Sergey Senozhatsky , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Chuck Lever , Sven Schnelle , Jiri Olsa , Jan Kara , Tejun Heo , Andrew Morton , linux-trace-kernel@vger.kernel.org, Linus Torvalds , Dave Kleikamp , linux-mm@kvack.org, Joel Fernandes , Eric Dumazet , Stanislav Fomichev , linux-s390@vger.kernel.org, linux-nilfs@vger.kernel.org, Paul Moore , Leon Romanovsky , John Fastabend , Luis Chamberlain , codalist@coda.cs.cmu.edu, Iurii Zaikin , Namjae Jeon , Masami Hiramatsu , Todd Kjos , Vasily Gorbik , selinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, reiserfs-devel@vger.kernel.org, Miklos Szeredi , Yue Hu , Jaegeuk Kim , Martijn Coenen , OGAWA Hirofumi , Hao Luo , Tony Luck , Theodore Ts'o , Nicolas Pitre , linux-ntfs-dev@lists.sourceforge.net, Muchun Song , linux-f2fs-devel@lists.sourceforge.net, "Guilherme G. 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Hallyn" , Christian Schoenebeck , Kees Cook , Arnd Bergmann , autofs@vger.kernel.org, Steven Rostedt , Mark Gross , Damien Le Moal , Eric Paris , ceph-devel@vger.kernel.org, Gao Xiang , Jan Harkes , linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org, Olga Kornievskaia , Song Liu , samba-technical@lists.samba.org, Steve French , Jeremy Kerr , Netdev , Bob Peterson , linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org, ntfs3@lists.linux.dev, linux-erofs@lists.ozlabs.org, "David S . Miller" , Chandan Babu R , jfs-discussion@lists.sourceforge.net, Jan Kara , Neil Brown , Dominique Martinet , Amir Goldstein , Bob Copeland , KP Singh , linux-unionfs@vger.kernel.org, David Howells , Joseph Qi , Andreas Dilger , M ikulas Patocka , Ard Biesheuvel , Anton Ivanov , Andreas Gruenbacher , Richard Weinberger , Mark Fasheh , Dai Ngo , Jason Gunthorpe , linux-serial@vger.kernel.org, Jakub Kicinski , Salah Triki , Evgeniy Dushistov , linux-cifs@vger.kernel.org, Heiko Carstens , Chao Yu , apparmor@lists.ubuntu.com, Josef Bacik , Tom Talpey , Hans de Goede , "Tigran A. Aivazian" , David Sterba , Xiubo Li , Ryusuke Konishi , Johannes Thumshirn , Ritu Agarwal , Luis de Bethencourt , Martin KaFai Lau , v9fs@lists.linu x.dev, David Sterba , linux-security-module@vger.kernel.org, Jeffle Xu , Phillip Lougher , Johannes Berg , Sungjong Seo , David Woodhouse , linux-karma-devel@lists.sourceforge.net, linux-btrfs@vger.kernel.org, Joel Becker Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Sep 28, 2023 at 01:06:03PM -0400, Jeff Layton wrote: > On Thu, 2023-09-28 at 11:48 -0400, Arnd Bergmann wrote: > > On Thu, Sep 28, 2023, at 07:05, Jeff Layton wrote: > > > This shaves 8 bytes off struct inode, according to pahole. > > > > > > Signed-off-by: Jeff Layton > > > > FWIW, this is similar to the approach that Deepa suggested > > back in 2016: > > > > https://lore.kernel.org/lkml/1452144972-15802-3-git-send-email-deepa.kernel@gmail.com/ > > > > It was NaKed at the time because of the added complexity, > > though it would have been much easier to do it then, > > as we had to touch all the timespec references anyway. > > > > The approach still seems ok to me, but I'm not sure it's worth > > doing it now if we didn't do it then. > > > > I remember seeing those patches go by. I don't remember that change > being NaK'ed, but I wasn't paying close attention at the time > > Looking at it objectively now, I think it's worth it to recover 8 bytes > per inode and open a 4 byte hole that Amir can use to grow the > i_fsnotify_mask. We might even able to shave off another 12 bytes > eventually if we can move to a single 64-bit word per timestamp. I don't think you can, since btrfs timestamps utilize s64 seconds counting in both directions from the Unix epoch. They also support ns resolution: struct btrfs_timespec { __le64 sec; __le32 nsec; } __attribute__ ((__packed__)); --D > It is a lot of churn though. > -- > Jeff Layton