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 D2A81E743D3 for ; Fri, 29 Sep 2023 00:38:24 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=google header.b=QX6VBSWj; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4RxWfl3yfZz3dkQ for ; Fri, 29 Sep 2023 10:38:23 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=google header.b=QX6VBSWj; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linuxfoundation.org (client-ip=2a00:1450:4864:20::433; helo=mail-wr1-x433.google.com; envelope-from=torvalds@linuxfoundation.org; receiver=lists.ozlabs.org) Received: from mail-wr1-x433.google.com (mail-wr1-x433.google.com [IPv6:2a00:1450:4864:20::433]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4RxM5j4CZ1z3cbG for ; Fri, 29 Sep 2023 04:12:40 +1000 (AEST) Received: by mail-wr1-x433.google.com with SMTP id ffacd0b85a97d-31f7400cb74so12023039f8f.2 for ; Thu, 28 Sep 2023 11:12:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; t=1695924753; x=1696529553; darn=lists.ozlabs.org; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=UoV8bp+GLn88RdeFyi+3G/jZGwWmlguHsi2KfbyyFTc=; b=QX6VBSWjezHYd/1AX/qzA3QKEOWtiTGiJrN6fdc3VJfPsdfwQp0GiBJ0UsKmCV3iA/ toNBdH3OslcpBruiaSZpaH+qy1/Xa0rGEODFJdmVGTEOEJthyvcT23ldPkQ8Y32f0lFU ZKAJauRiGWmsd6ZboMi3KTXxMBnL1qIzmZg8w= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695924753; x=1696529553; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=UoV8bp+GLn88RdeFyi+3G/jZGwWmlguHsi2KfbyyFTc=; b=UDmS4nSSklcb1i6Z287DE1RhuK9xVPuQhGGrQYMq14dzumj2IM869O0BkI5dR8r2Dq 9hM1LPKxuvjwuFnhqvyL8/NzeVPYROJQK5oPPwpKUOpz+JUs9nDJZ5XJVu46pHdJaz+9 3BwTybIlmiy0HWWo200KwhLxwaFC/iwCxemRiXQjg9FknAAE/Mvn5xb+2h4QaOcSCigg XHVyQWE80HpRm4+mt2yvLpdlWueU2//kRtSWTZ06a+iz59bnF423EAaPHsl1Y95h/7Uv d5g0CpYgmfcHo1LICvYBl0QfN9lw5in3cf2hKVtacq94i20CzkvpSM+XjmFlGflXiP03 zPww== X-Gm-Message-State: AOJu0YxHQit51pJe2X5QUMdsKqALHbPOFUecDRl0r116YgxzPiPF9Oy1 BWY39pmdMchAQZ4Wtrw5D2k6MmSehSSmeyciV8zGzB75ZJI= X-Google-Smtp-Source: AGHT+IGiIwt/VbmABQjpTzFxnxdwfSd/pChgVExsyHrix5FO+bj1c82QJcgOLfEGV3onhuiYbuWxMQ== X-Received: by 2002:a5d:4f8a:0:b0:317:5f13:5c2f with SMTP id d10-20020a5d4f8a000000b003175f135c2fmr1883490wru.0.1695924753282; Thu, 28 Sep 2023 11:12:33 -0700 (PDT) Received: from mail-wm1-f54.google.com (mail-wm1-f54.google.com. [209.85.128.54]) by smtp.gmail.com with ESMTPSA id d19-20020a17090692d300b009ae69c303aasm10751894ejx.137.2023.09.28.11.12.32 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Sep 2023 11:12:33 -0700 (PDT) Received: by mail-wm1-f54.google.com with SMTP id 5b1f17b1804b1-405361bb9f7so136740345e9.2 for ; Thu, 28 Sep 2023 11:12:32 -0700 (PDT) X-Received: by 2002:aa7:d899:0:b0:52f:c073:9c77 with SMTP id u25-20020aa7d899000000b0052fc0739c77mr1748627edq.35.1695922912868; Thu, 28 Sep 2023 10:41:52 -0700 (PDT) MIME-Version: 1.0 References: <20230928110554.34758-1-jlayton@kernel.org> <20230928110554.34758-3-jlayton@kernel.org> In-Reply-To: <20230928110554.34758-3-jlayton@kernel.org> From: Linus Torvalds Date: Thu, 28 Sep 2023 10:41:34 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 87/87] fs: move i_blocks up a few places in struct inode To: Jeff Layton Content-Type: text/plain; charset="UTF-8" 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" , "Darrick J. Wong" , Anders Larsen , Carlos Llamas , Andrii Nakryiko , Mattia Dongili , Hugh Dickins , 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 , =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= , Chuck Lever , Sven Schnelle , Jiri Olsa , Jan Kara , Tejun Heo , Andrew Morton , linux-trace-kernel@vger.kernel.org, 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. Piccoli" , gfs2@lists.linux.dev, Eric Biederman , Anna Schumaker , Brad Warrum , Mike Kravetz , linux-efi@vger.k ernel.org, Martin Brandenburg , ocfs2-devel@lists.linux.dev, Alexei Starovoitov , platform-driver-x86@vger.kernel.org, Chris Mason , linux-mtd@lists.infradead.org, linux-hardening@vger.kernel.org, Marc Dionne , Jiri Slaby , linux-afs@lists.infradead.org, Ian Kent , Naohiro Aota , Daniel Borkmann , Dennis Dalessandro , linux-rdma@vger.kernel.org, coda@cs.cmu.edu, =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= , Ilya Dryomov , Paolo Abeni , "Serge E. 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@vger.kernel.org, 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 , Mikulas 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.linux.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, 28 Sept 2023 at 04:06, Jeff Layton wrote: > > Move i_blocks up above the i_lock, which moves the new 4 byte hole to > just after the timestamps, without changing the size of the structure. I'm sure others have mentioned this, but 'struct inode' is marked with __randomize_layout, so the actual layout may end up being very different. I'm personally not convinced the whole structure randomization is worth it - it's easy enough to figure out for any distro kernel since the seed has to be the same across machines for modules to work, so even if the seed isn't "public", any layout is bound to be fairly easily discoverable. So the whole randomization only really works for private kernel builds, and it adds this kind of pain where "optimizing" the structure layout is kind of pointless depending on various options. I certainly *hope* no distro enables that pointless thing, but it's a worry. Linus