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=-6.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 C1527C433DB for ; Wed, 10 Mar 2021 18:23:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9484964DAF for ; Wed, 10 Mar 2021 18:23:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233340AbhCJSX0 (ORCPT ); Wed, 10 Mar 2021 13:23:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:38130 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229602AbhCJSXL (ORCPT ); Wed, 10 Mar 2021 13:23:11 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7C19264EE2; Wed, 10 Mar 2021 18:23:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615400591; bh=ofwr0djgmV5AwKLBclBoFXU08p4fHrwTsEPkjAt2/fs=; h=Date:From:To:Cc:Subject:From; b=AEGjpzvLa7RfaY0h8oucryFjkgkIcnhtkgAhT2MHcu44s+8mMXR92hV3saEDnUG2V ya1YQaO2yZAvzLhBPBRD4RAOApvBocEw3rTb3DGDzwbnYYbODluN1IlHMVTG9WbK26 8YRCiNLQCwnkHT+1CZ/PqTuy2vUs6r7t43MiIj/egaSEix18bwtFikly7Rz/xjTq9c GAYvmYWEPtK9MIR6hsUYJPrMlkFFmchspBPJRLt2R931wF13Xjj8Z/utoNFUuAHeas fPBNca/2Q5l9wau/uGIVKTNrj1jFixlGqJ9ArojTZXTbkrFI+zBnxoA29EQYlBOm+A kVIzS3/OvJsMQ== Date: Wed, 10 Mar 2021 11:23:07 -0700 From: Nathan Chancellor To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: -Walign-mismatch in block/blk-mq.c Message-ID: <20210310182307.zzcbi5w5jrmveld4@archlinux-ax161> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Jens, There is a new clang warning added in the development branch, -Walign-mismatch, which shows an instance in block/blk-mq.c: block/blk-mq.c:630:39: warning: passing 8-byte aligned argument to 32-byte aligned parameter 2 of 'smp_call_function_single_async' may result in an unaligned pointer access [-Walign-mismatch] smp_call_function_single_async(cpu, &rq->csd); ^ 1 warning generated. There appears to be some history here as I can see that this member was purposefully unaligned in commit 4ccafe032005 ("block: unalign call_single_data in struct request"). However, I later see a change in commit 7c3fb70f0341 ("block: rearrange a few request fields for better cache layout") that seems somewhat related. Is it possible to get back the alignment by rearranging the structure again? This seems to be the only solution for the warning aside from just outright disabling it, which would be a shame since it seems like it could be useful for architectures that cannot handle unaligned accesses well, unless I am missing something obvious :) Cheers, Nathan