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=-8.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 C7428C388F7 for ; Thu, 22 Oct 2020 08:35:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61083223FB for ; Thu, 22 Oct 2020 08:35:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VokcFf2i" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2508042AbgJVIfk (ORCPT ); Thu, 22 Oct 2020 04:35:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:26895 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2507994AbgJVIfg (ORCPT ); Thu, 22 Oct 2020 04:35:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603355735; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AfHzVZ9ARVJM/ygIfC1QZ398dtBlt7YNWVKjnVzurTM=; b=VokcFf2i8L4P7N6p6g1GPzIk6C4eSFVTb5tlnAVTBilTNWxUevfM8DpMbIfkJQpn94AG+0 cpaCgF7ODsxCEnwLzJ5x8Xkc7EEGBQ7ul0WujEaTBeLefiHXLKbUtZUFAiRK1kAbtq4m6h JJ4B7smwjoegfbDrrShW+ZC1AM3+10w= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-548-2Rope0bHNb6JPkcxydWrHA-1; Thu, 22 Oct 2020 04:35:30 -0400 X-MC-Unique: 2Rope0bHNb6JPkcxydWrHA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 28CE7879517; Thu, 22 Oct 2020 08:35:27 +0000 (UTC) Received: from [10.36.113.152] (ovpn-113-152.ams2.redhat.com [10.36.113.152]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5EA8D5D9DD; Thu, 22 Oct 2020 08:35:21 +0000 (UTC) Subject: Re: Buggy commit tracked to: "Re: [PATCH 2/9] iov_iter: move rw_copy_check_uvector() into lib/iov_iter.c" To: Greg KH , Al Viro , Nick Desaulniers Cc: Christoph Hellwig , kernel-team@android.com, Andrew Morton , Jens Axboe , Arnd Bergmann , David Howells , David Laight , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org References: <20200925045146.1283714-1-hch@lst.de> <20200925045146.1283714-3-hch@lst.de> <20201021161301.GA1196312@kroah.com> <20201021233914.GR3576660@ZenIV.linux.org.uk> <20201022082654.GA1477657@kroah.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <80a2e5fa-718a-8433-1ab0-dd5b3e3b5416@redhat.com> Date: Thu, 22 Oct 2020 10:35:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20201022082654.GA1477657@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 22.10.20 10:26, Greg KH wrote: > On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote: >> On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote: >>> On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote: >>>> From: David Laight >>>> >>>> This lets the compiler inline it into import_iovec() generating >>>> much better code. >>>> >>>> Signed-off-by: David Laight >>>> Signed-off-by: Christoph Hellwig >>>> --- >>>> fs/read_write.c | 179 ------------------------------------------------ >>>> lib/iov_iter.c | 176 +++++++++++++++++++++++++++++++++++++++++++++++ >>>> 2 files changed, 176 insertions(+), 179 deletions(-) >>> >>> Strangely, this commit causes a regression in Linus's tree right now. >>> >>> I can't really figure out what the regression is, only that this commit >>> triggers a "large Android system binary" from working properly. There's >>> no kernel log messages anywhere, and I don't have any way to strace the >>> thing in the testing framework, so any hints that people can provide >>> would be most appreciated. >> >> It's a pure move - modulo changed line breaks in the argument lists >> the functions involved are identical before and after that (just checked >> that directly, by checking out the trees before and after, extracting two >> functions in question from fs/read_write.c and lib/iov_iter.c (before and >> after, resp.) and checking the diff between those. >> >> How certain is your bisection? > > The bisection is very reproducable. > > But, this looks now to be a compiler bug. I'm using the latest version > of clang and if I put "noinline" at the front of the function, > everything works. Well, the compiler can do more invasive optimizations when inlining. If you have buggy code that relies on some unspecified behavior, inlining can change the behavior ... but going over that code, there isn't too much action going on. At least nothing screamed at me. -- Thanks, David / dhildenb