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 182F1CE7B1F for ; Fri, 29 Sep 2023 09:33:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9BB726B025A; Fri, 29 Sep 2023 05:33:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 944206B0266; Fri, 29 Sep 2023 05:33:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 798086B0269; Fri, 29 Sep 2023 05:33:35 -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 69AC76B025A for ; Fri, 29 Sep 2023 05:33:35 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 2A571141313 for ; Fri, 29 Sep 2023 09:33:35 +0000 (UTC) X-FDA: 81289122390.04.9226C60 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf03.hostedemail.com (Postfix) with ESMTP id 7472620004 for ; Fri, 29 Sep 2023 09:33:33 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=j3Z7MPGX; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf03.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=1695980013; 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=NNKyA6g97rLVbr42UzH2N/ytlbMvdX3fLnQJc60CKxo=; b=eDCcsa5FV/vEtTusq1IYW7QlfQnRt2vj3pf3/SDNAx+Aq6ZoWIngw4vWI7w9z+IpIPsPzh IkyUA3xGzD1IKpukWu8nZkLc4uLrXKJmLxzEBjrhX6X6Hn1qQluT+pGfoPyqTzPG8OSt2A g+kelQJJ1zHsY1MKXQXnZBLH5FgKvew= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=j3Z7MPGX; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf03.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=1695980013; a=rsa-sha256; cv=none; b=BER6nYK/bd05TYB0Hjih8538+eAOBh5gwnG+IfYhsrctfxsCXeTUBLjVMe0M/ZD/PT2IJI YnxQGlPH+jc4cQJhAJBhLIywpOQjZD3Q5Odax7oqEn28iavedB+/bOAnVH9jKeiWMz0ETt 6VyjcV2K5PJeSYEesTv4bcFY6QgOMso= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 2FAEC61E8C; Fri, 29 Sep 2023 09:33:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D9F8C433C8; Fri, 29 Sep 2023 09:32:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695980011; bh=5rEQjJQmUmhQcZE/S/zbC0z+O4aP1HcivNZvR+uMTdw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j3Z7MPGXgH3qxJhUlGKswKaevoMz5lRlYfLKv517rB572Uft036HOzVnh6y+Fta2y IoP7pRk6lJWa27fv+jFujIlmXsGfS+YQww12NsbvPCYDl6f8XCPE+CtURkcHaeicsG yrkS/+0BXoBXAhDuBIWkGS4iWyGcgZc4uj5K1I6XTsFJQGfVSUCd06bbdxYUiSeitY kWvaORdHP4IXSdIX2Ck5PihMbYV+j7YqPan4YQc6tbETcfSrUPTc518VDuKuEt3jeG gYpsCzcJzJ2TfBOID0I9Ah10OPTMXVGJPcaLChcuIuOHlJVeXlo8F4Hi+JnhGg6W4h 6HAwcZKgDftHQ== Date: Fri, 29 Sep 2023 11:32:49 +0200 From: Christian Brauner To: Linus Torvalds Cc: Jeff Layton , Alexander Viro , David Sterba , Amir Goldstein , Theodore Ts'o , Eric Biederman , Kees Cook , Jeremy Kerr , Arnd Bergmann , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Greg Kroah-Hartman , Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= , Todd Kjos , Martijn Coenen , Joel Fernandes , Carlos Llamas , Suren Baghdasaryan , Mattia Dongili , Dennis Dalessandro , Jason Gunthorpe , Leon Romanovsky , Brad Warrum , Ritu Agarwal , Hans de Goede , Ilpo =?utf-8?B?SsOkcnZpbmVu?= , Mark Gross , Jiri Slaby , Eric Van Hensbergen , Latchesar Ionkov , Dominique Martinet , Christian Schoenebeck , David Sterba , David Howells , Marc Dionne , Ian Kent , Luis de Bethencourt , Salah Triki , "Tigran A. 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Hallyn" , Stephen Smalley , Eric Paris , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-rdma@vger.kernel.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, v9fs@lists.linux.dev, linux-afs@lists.infradead.org, autofs@vger.kernel.org, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org, codalist@coda.cs.cmu.edu, linux-efi@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, gfs2@lists.linux.dev, linux-um@lists.infradead.org, linux-mtd@lists.infradead.org, jfs-discussion@lists.sourceforge.net, linux-nfs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, ntfs3@lists.linux.dev, ocfs2-devel@lists.linux.dev, linux-karma-devel@lists.sourceforge.net, devel@lists.orangefs.org, linux-unionfs@vger.kernel.org, linux-hardening@vger.kernel.org, reiserfs-devel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-trace-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, selinux@vger.kernel.org Subject: Re: [PATCH 87/87] fs: move i_blocks up a few places in struct inode Message-ID: <20230929-keimt-umspannen-bfd12d2c2033@brauner> References: <20230928110554.34758-1-jlayton@kernel.org> <20230928110554.34758-3-jlayton@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 7472620004 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: pumfc9eeonona98qnogmtqxfpidmwuij X-HE-Tag: 1695980013-432135 X-HE-Meta: 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 jpUHdk9N 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rhSJXhySO7ez9qwceVxzovvpEch2qVXBz63oCeuCMBDOPGDuYHo9AmM23PHNM2alcmzEMoS70MBCFcJ79yKMoCje1f+p0oan3mktJN3ozGZ7HJzBR5JiXo/xXl02QpcADbZKgJGcwWUxCIQV42iWIMrJPfRd7wia99THAh409xqwW0bFCiqMaDGFAuxWSgaTMkI80ftZRfyCwH3VaSFvbmPPD1wUPDvxG/ko8cMeoC1ZG3ouei5iy3+8skHqr9ousbK6QVoxTKifhyWZ+oKPjt0zsSx4cXw9uIZjaoDpdOwhmDDisnsSDkDoua1ipThk46+2tCJB0kgt/hEHACgOzQyqlGT1NtrJ8Deny5WShzCYPorTFkIpSckryf8uRr136z9hZuZAryzY3pn5GUzeOkN7+jNEvGUUc= 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: On Thu, Sep 28, 2023 at 10:41:34AM -0700, Linus Torvalds wrote: > 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. They don't last we checked. Just last cycle we moved stuff in struct file around to optimize things and we explicitly said we don't give a damn about struct randomization. Anyone who enables this will bleed performance pretty badly, I would reckon.