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=-7.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, PDS_BAD_THREAD_QP_64,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 7C5BAC43460 for ; Wed, 14 Apr 2021 15:52:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 06D1C61244 for ; Wed, 14 Apr 2021 15:52:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 06D1C61244 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=ACULAB.COM Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9B7EF6B0081; Wed, 14 Apr 2021 11:52:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 98E2F6B0082; Wed, 14 Apr 2021 11:52:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 82F7D6B0083; Wed, 14 Apr 2021 11:52:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0123.hostedemail.com [216.40.44.123]) by kanga.kvack.org (Postfix) with ESMTP id 6A5946B0081 for ; Wed, 14 Apr 2021 11:52:22 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 1D1865923C19 for ; Wed, 14 Apr 2021 15:52:22 +0000 (UTC) X-FDA: 78031414524.23.A32B11A Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by imf02.hostedemail.com (Postfix) with ESMTP id 5A34F40002C2 for ; Wed, 14 Apr 2021 15:52:05 +0000 (UTC) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-15-m9cXnC2KMlaJybEViQCuIg-1; Wed, 14 Apr 2021 16:52:18 +0100 X-MC-Unique: m9cXnC2KMlaJybEViQCuIg-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, 14 Apr 2021 16:52:16 +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, 14 Apr 2021 16:52:16 +0100 From: David Laight To: 'Matthew Wilcox' , Jesper Dangaard Brouer CC: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mips@vger.kernel.org" , Ilias Apalodimas , Matteo Croce , Grygorii Strashko , Arnd Bergmann , "Christoph Hellwig" Subject: RE: [PATCH 1/1] mm: Fix struct page layout on 32-bit systems Thread-Topic: [PATCH 1/1] mm: Fix struct page layout on 32-bit systems Thread-Index: AQHXMSRrwdfrgigLI0exh4xFUSZq9Kq0J1eg Date: Wed, 14 Apr 2021 15:52:16 +0000 Message-ID: <7f6cee3dcf1749fbb7b54eaf129141e7@AcuMS.aculab.com> References: <20210410205246.507048-1-willy@infradead.org> <20210410205246.507048-2-willy@infradead.org> <20210411114307.5087f958@carbon> <20210411103318.GC2531743@casper.infradead.org> <20210412011532.GG2531743@casper.infradead.org> <20210414101044.19da09df@carbon> <20210414115052.GS2531743@casper.infradead.org> In-Reply-To: <20210414115052.GS2531743@casper.infradead.org> 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: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 5A34F40002C2 X-Stat-Signature: 17u1wt3bx1fnedmozpcb8r8ecmshhefe Received-SPF: none (aculab.com>: No applicable sender policy available) receiver=imf02; identity=mailfrom; envelope-from=""; helo=eu-smtp-delivery-151.mimecast.com; client-ip=185.58.86.151 X-HE-DKIM-Result: none/none X-HE-Tag: 1618415525-856655 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > Doing this fixes it: >=20 > +++ b/include/linux/types.h > @@ -140,7 +140,7 @@ typedef u64 blkcnt_t; > * so they don't care about the size of the actual bus addresses. > */ > #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT > -typedef u64 dma_addr_t; > +typedef u64 __attribute__((aligned(sizeof(void *)))) dma_addr_t; > #else > typedef u32 dma_addr_t; > #endif I hate __packed so much I've been checking what it does! If you add __packed to the dma_addr_t field inside the union then gcc (at least) removes the pad from before it, but also 'remembers' the alignment that is enforced by other members of the structure. So you don't need the extra aligned(sizeof (void *)) since that is implicit. So in this case __packed probably has no side effects. (Unless a 32bit arch has instructions for a 64bit read that must not be on an 8n+4 boundary and the address is taken). It also doesn't affect 64bit - since the previous field forces 64bit alignment. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)