Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753169AbdHVTMI (ORCPT ); Tue, 22 Aug 2017 15:12:08 -0400 Received: from mail-bl2nam02on0114.outbound.protection.outlook.com ([104.47.38.114]:9696 "EHLO NAM02-BL2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753012AbdHVTLK (ORCPT ); Tue, 22 Aug 2017 15:11:10 -0400 From: Long Li To: Christoph Hellwig CC: KY Srinivasan , Haiyang Zhang , "James E.J. Bottomley" , "devel@linuxdriverproject.org" , "linux-scsi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: RE: [PATCH] storvsc: do not assume SG list is continuous when doing bounce buffers (for 4.1 stable only) Thread-Topic: [PATCH] storvsc: do not assume SG list is continuous when doing bounce buffers (for 4.1 stable only) Thread-Index: AQHTGwgeCzSYTgLBr0SPYmQRSrcKyKKP6bqAgADTlUA= Date: Tue, 22 Aug 2017 19:11:04 +0000 Message-ID: References: <1503379905-18908-1-git-send-email-longli@exchange.microsoft.com> <20170822062841.GA1061@infradead.org> In-Reply-To: <20170822062841.GA1061@infradead.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=True; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Ref=https://api.informationprotection.azure.com/api/72f988bf-86f1-41af-91ab-2d7cd011db47; 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charset="us-ascii" MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Aug 2017 19:11:04.4786 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR21MB0127 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v7MJCFej012522 Content-Length: 968 Lines: 21 > Wouldn't it make sense to backport the changes to set the virt_boundary > (which probably still is the SG_GAPS flag in such an old kernel)? We can make storvsc use SG_GAPS. But the following patch is missing in 4.1 stable block layer to make this work on some I/O situations. Backporting is more difficult and affect other code. commit 5e7c4274a70aa2d6f485996d0ca1dad52d0039ca Author: Jens Axboe Date: Thu Sep 3 19:28:20 2015 +0300 block: Check for gaps on front and back merges We are checking for gaps to previous bio_vec, which can only detect back merges gaps. Moreover, at the point where we check for a gap, we don't know if we will attempt a back or a front merge. Thus, check for gap to prev in a back merge attempt and check for a gap to next in a front merge attempt. Signed-off-by: Jens Axboe [sagig: Minor rename change] Signed-off-by: Sagi Grimberg