From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758574Ab2JKLda (ORCPT ); Thu, 11 Oct 2012 07:33:30 -0400 Received: from multi.imgtec.com ([194.200.65.239]:24793 "EHLO multi.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758351Ab2JKLd3 (ORCPT ); Thu, 11 Oct 2012 07:33:29 -0400 Message-ID: <5076AE3B.5040509@imgtec.com> Date: Thu, 11 Oct 2012 12:32:11 +0100 From: James Hogan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120911 Thunderbird/15.0.1 MIME-Version: 1.0 To: James Bottomley CC: , Subject: Re: [RESEND PATCH] scsi: make struct scsi_varlen_cdb_hdr packed References: <1349946933-30314-1-git-send-email-james.hogan@imgtec.com> <1349951069.2425.44.camel@dabdike.int.hansenpartnership.com> In-Reply-To: <1349951069.2425.44.camel@dabdike.int.hansenpartnership.com> X-Enigmail-Version: 1.4.4 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.154.65] X-SEF-Processed: 7_3_0_01181__2012_10_11_12_33_23 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/10/12 11:24, James Bottomley wrote: > On Thu, 2012-10-11 at 10:15 +0100, James Hogan wrote: >> The struct scsi_varlen_cdb_hdr is expected to be exactly 10 bytes when >> used in struct osd_cdb_head, but it isn't marked as packed. Some >> architectures will round the struct size up which triggers BUILD_BUG_ON >> compile errors in osd_initiator.c when the outer structs are unexpected >> sizes. This is fixed by marking struct scsi_varlen_cdb_hdr as __packed. > > What actual problem have you encountered? The structure is {u8[8], u16} > which is naturally packed on every architecture I know about. I've even > built osd_initiator without problem on parisc, which has some of the > most rigid alignment rules I've seen. Hi James, The alignment is fine (the offset of the u16 is 8 bytes), but unfortunately with the metag port of gcc, sizeof(struct scsi_varlen_cdb_hdr) is rounded up to a 4 byte boundary (even though the largest data member alignment is only 2 bytes), which is 12 bytes instead of 10. Cheers James