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.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (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 4B083E7F154 for ; Fri, 29 Sep 2023 09:33:45 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-1.v29.lw.sourceforge.com) by sfs-ml-1.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1qm9sW-0004pE-Ec; Fri, 29 Sep 2023 09:33:43 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qm9sT-0004ov-CP; Fri, 29 Sep 2023 09:33:40 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=NNKyA6g97rLVbr42UzH2N/ytlbMvdX3fLnQJc60CKxo=; b=KLGNBNufZiZKn0QfrJerH6T0Yf Wyx+VzlNmH2bkR8KT4llbe+edwAHy86UMls3F0zdcqMbfvrsPnOkwc05hJj70KzgAkzf6xYNvNmR0 62WxaJTylS3V+mjeuXUmr+cUx3tf/CB8v+xN0laoT8JC8eGkSyX6+Gd8hPY1lvP/4HNE=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To :From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=NNKyA6g97rLVbr42UzH2N/ytlbMvdX3fLnQJc60CKxo=; b=JVI6g/zFccuuxFKgZh8pNVC8PJ BoTZkn6gOIPkP/Xf1eamhLhc3lblPTA6nSIFQ/WQCcLGdXJtR0CpjjXLrmiizhM33HcVVsnp13jXd +DUhzfLkGSEtRf9lL0U5HrEOM/nMIU9s94V7jT5d9MkjmjfHnVI49ag9OAnxmEOairAk=; Received: from dfw.source.kernel.org ([139.178.84.217]) by sfi-mx-1.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1qm9sQ-00BHUy-E4; Fri, 29 Sep 2023 09:33:40 +0000 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 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-Disposition: inline In-Reply-To: X-Headers-End: 1qm9sQ-00BHUy-E4 Subject: Re: [f2fs-dev] [PATCH 87/87] fs: move i_blocks up a few places in struct inode X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: 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, Michael Ellerman , James Morris , Christophe Leroy , 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 , Greg Kroah-Hartman , Stephen Smalley , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Ronnie Sahlberg , Sergey Senozhatsky , Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= , Chuck Lever , Sven Schnelle , Jiri Olsa , Jan Kara , Tejun Heo , Andrew Morton , linux-trace-kernel@vger.kernel.org, Dave Kleikamp , samba-technical@lists.samba.org, 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.kernel.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, Ilpo =?utf-8?B?SsOkcnZpbmVu?= , 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 , Jeff Layton , 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 , 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net 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. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel