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 X-Spam-Level: X-Spam-Status: No, score=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 242D9C433E0 for ; Fri, 8 Jan 2021 20:30:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C86BF23AC0 for ; Fri, 8 Jan 2021 20:30:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729132AbhAHUad (ORCPT ); Fri, 8 Jan 2021 15:30:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727443AbhAHUac (ORCPT ); Fri, 8 Jan 2021 15:30:32 -0500 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 441BCC061380; Fri, 8 Jan 2021 12:29:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: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=3NuKcP/o2asx0FFI9whdbE8cG4acAU/bjOidJQiHRu4=; b=SxjT6qlizraAdzfoC5DuKEWS9 05kTbDGljDKQCF7Y89n5rm1G8jVt15Cij9mGOb26YoYjV1lBEXJKfxWl1zXT4yzUabdV13w3ANw42 suUwIcfafPitFROZMPDmmxsW7RiHGlPix2V6aRHu8SZS6kIqAGbycJknu6c1bVmOuARHT2Sj4uwLZ IOv3ymo6c8n5rRXIS3ZpmSQ3fPiUiNy6gGkEqVMfUKwkJ5uqvNog6CZghXRpPM+8MFv3ioz5h1oCM kJOlq8RfZ27wyWNEnqrMVxxZM/hjVo+0WvI5VxJa86Tm8lMIeENA/ourZ7x0IfSHmqTvVK/q7QTdE LtN05F7gQ==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:45446) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kxyNx-0004SJ-2y; Fri, 08 Jan 2021 20:29:25 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1kxyNw-0002SW-4O; Fri, 08 Jan 2021 20:29:24 +0000 Date: Fri, 8 Jan 2021 20:29:24 +0000 From: Russell King - ARM Linux admin To: Linus Torvalds Cc: Will Deacon , Peter Zijlstra , Arnd Bergmann , linux-toolchains@vger.kernel.org, Mark Rutland , Theodore Ts'o , "linux-kernel@vger.kernel.org" , Andreas Dilger , Ext4 Developers List , Linux ARM Subject: Re: Aarch64 EXT4FS inode checksum failures - seems to be weak memory ordering issues Message-ID: <20210108202924.GY1551@shell.armlinux.org.uk> References: <20210106172033.GA2165@willie-the-truck> <20210106223223.GM1551@shell.armlinux.org.uk> <20210107111841.GN1551@shell.armlinux.org.uk> <20210107124506.GO1551@shell.armlinux.org.uk> <20210107133747.GP1551@shell.armlinux.org.uk> <20210108092655.GA4031@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: Russell King - ARM Linux admin Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 08, 2021 at 12:02:53PM -0800, Linus Torvalds wrote: > Well, honestly, I'm always in favor of having people not use ancient > compilers, but both of the issues at hand do seem to be specific to > arm64. > > The "gcc before 5.1 generates incorrect stack pointer writes on arm64" > sounds pretty much deadly, and I think means that yes, for arm64 we > simply need to require 5.1 or newer. > > I also suspect there is much less reason to use old gcc's on arm64. I > can't imagine that people really run very old setups, Is some old RHEL > version even relevant for arm64? For me, six years old for a compiler is really not "very old" - and, when I first encountered this problem, it was over 12 months ago. Apart from the kernel, I am not in the habbit of upgrading stuff for the sake of upgrading - I tend to stick with what I have and what works. Not everyone on this planet has a desire to have the latest and greatest all the time. Since then, I've _not_ wanted to change the compiler in case the problem vanishes without explanation - it had the feeling of being way more serious than a compiler bug, potentially a memory ordering bug. It took about a year just to start being able to work out what was going on - it would take up to about three months to show for me, and when it did, it spat out an ext4 inode checksum error and made the rootfs read-only. To "hide" that by upgrading the compiler, and then to be in the situation where you do not trust any aarch64 machine with your data is no real solution. That's exactly where I was until this had been found. The aarch64 architecture had completely lost my trust as a viable computing platform - and I was at the point of considering disposing of all my aarch64 hardware and replacing it with x86. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!