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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 CDA99C433C1 for ; Wed, 31 Mar 2021 10:39:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7170161987 for ; Wed, 31 Mar 2021 10:39:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234981AbhCaKis convert rfc822-to-8bit (ORCPT ); Wed, 31 Mar 2021 06:38:48 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:31676 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234862AbhCaKiU (ORCPT ); Wed, 31 Mar 2021 06:38:20 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-99-VTUrauydP9eC8qUNDw8g6Q-1; Wed, 31 Mar 2021 11:38:16 +0100 X-MC-Unique: VTUrauydP9eC8qUNDw8g6Q-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 31 Mar 2021 11:38:15 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.012; Wed, 31 Mar 2021 11:38:15 +0100 From: David Laight To: 'Nathan Chancellor' , Jian Cai CC: "cjdb@google.com" , "manojgupta@google.com" , "llozano@google.com" , "clang-built-linux@googlegroups.com" , Guenter Roeck , Jens Axboe , "Nick Desaulniers" , "linux-block@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] blk-mq: fix alignment mismatch. Thread-Topic: [PATCH] blk-mq: fix alignment mismatch. Thread-Index: AQHXJbyzId+/bYuSL06dtp6dmHSiz6qd53HQ Date: Wed, 31 Mar 2021 10:38:15 +0000 Message-ID: <553e40c54eea408a96f42eec53616993@AcuMS.aculab.com> References: <20210330230249.709221-1-jiancai@google.com> <20210330232946.m5p7426macyjduzm@archlinux-ax161> In-Reply-To: <20210330232946.m5p7426macyjduzm@archlinux-ax161> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Nathan Chancellor > Sent: 31 March 2021 00:30 > > Hi Jian, > > On Tue, Mar 30, 2021 at 04:02:49PM -0700, Jian Cai wrote: > > This fixes the mismatch of alignments between csd and its use as an > > argument to smp_call_function_single_async, which causes build failure > > when -Walign-mismatch in Clang is used. > > > > Link: > > http://crrev.com/c/1193732 > > > > Suggested-by: Guenter Roeck > > Signed-off-by: Jian Cai > > Thanks for the patch. This is effectively a revert of commit > 4ccafe032005 ("block: unalign call_single_data in struct request"), > which I had brought up in this thread: > > https://lore.kernel.org/r/20210310182307.zzcbi5w5jrmveld4@archlinux-ax161/ > > This is obviously a correct fix, I am not just sure what the impact to > 'struct request' will be. If the structure is allocated on-stack then aligning it requires the compiler generate the rather horrid 'double stack frame' for the function. Possibly the unaligned 'struct' should be used by all the code except for a few places where it makes sense to allocate an aligned item? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)