From patchwork Wed Nov 30 16:26:28 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ewan Milne X-Patchwork-Id: 9454589 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A18CD60585 for ; Wed, 30 Nov 2016 16:26:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8B79928467 for ; Wed, 30 Nov 2016 16:26:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7E64928470; Wed, 30 Nov 2016 16:26:32 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0937328467 for ; Wed, 30 Nov 2016 16:26:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757575AbcK3Q0b (ORCPT ); Wed, 30 Nov 2016 11:26:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37618 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757554AbcK3Q0a (ORCPT ); Wed, 30 Nov 2016 11:26:30 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3CB46C10656D; Wed, 30 Nov 2016 16:26:30 +0000 (UTC) Received: from [10.18.25.104] (dhcp-25-104.bos.redhat.com [10.18.25.104]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uAUGQTRN015833; Wed, 30 Nov 2016 11:26:29 -0500 Subject: Re: SG does not ignore dxferp (direct io + mmap) From: "Ewan D. Milne" Reply-To: emilne@redhat.com To: Johannes Thumshirn Cc: Laurence Oberman , Eyal Ben David , dgilbert@interlog.com, linux-scsi@vger.kernel.org In-Reply-To: <1194718949.74785.1480096576577.JavaMail.zimbra@redhat.com> References: <1479752642.19792.43.camel@localhost.localdomain> <20161122083759.xeifuex3xxfimuwz@linux-x5ow.site> <1479839407.28416.21.camel@localhost.localdomain> <2146476957.2165908.1479927335303.JavaMail.zimbra@redhat.com> <1479932524.28416.43.camel@localhost.localdomain> <20161125080758.5bh5jkcgvhw3xuvb@linux-x5ow.site> <1194718949.74785.1480096576577.JavaMail.zimbra@redhat.com> Organization: Red Hat Date: Wed, 30 Nov 2016 11:26:28 -0500 Message-ID: <1480523188.28416.94.camel@localhost.localdomain> Mime-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 30 Nov 2016 16:26:30 +0000 (UTC) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Fri, 2016-11-25 at 12:56 -0500, Ewan Milne wrote: > I think what we need to understand is what caused the regression in the > first place, I probably should have been bisecting the original failure > rather than trying to find where it started working. > Bisecting leads to this commit: commit 37f19e57a0de3c4a3417aa13ff4d04f1e0dee4b3 Author: Christoph Hellwig Date: Sun Jan 18 16:16:33 2015 +0100 block: merge __bio_map_user_iov into bio_map_user_iov And also remove the unused bdev argument. Signed-off-by: Christoph Hellwig Reviewed-by: Ming Lei Signed-off-by: Jens Axboe Specifically, the problem appears to be caused by the removal of the setting of bio->bi_bdev, which would previously be set to NULL. If I add: /* The test passes (no zero byte corruption). Setting dxferp would cause map_data.null_mapped to be set before it is passed to blk_rq_map_user(_iov) which would cause a difference in behavior. -Ewan --- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/block/bio.c b/block/bio.c index 0723d4c..ecac37b 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1351,6 +1351,7 @@ struct bio *bio_map_user_iov(struct request_queue *q, if (iter->type & WRITE) bio->bi_rw |= REQ_WRITE; + bio->bi_bdev = NULL; bio->bi_flags |= (1 << BIO_USER_MAPPED);