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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 1730FC17442 for ; Sun, 10 Nov 2019 14:43:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E2A2220869 for ; Sun, 10 Nov 2019 14:43:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726733AbfKJOnM (ORCPT ); Sun, 10 Nov 2019 09:43:12 -0500 Received: from mx2.suse.de ([195.135.220.15]:45656 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726402AbfKJOnL (ORCPT ); Sun, 10 Nov 2019 09:43:11 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id EE954AEF1; Sun, 10 Nov 2019 14:43:09 +0000 (UTC) Message-ID: <1573396023.2662.4.camel@suse.com> Subject: Re: [PATCH 4.19 114/149] UAS: Revert commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments") From: Oliver Neukum To: Alan Stern , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Christoph Hellwig Date: Sun, 10 Nov 2019 15:27:03 +0100 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Freitag, den 08.11.2019, 10:35 -0500 schrieb Alan Stern: > On Fri, 8 Nov 2019, Greg Kroah-Hartman wrote: > > > On Thu, Nov 07, 2019 at 12:32:45PM +0100, Oliver Neukum wrote: > > > Am Dienstag, den 05.11.2019, 17:38 +0100 schrieb Greg Kroah-Hartman: > > > > > > Given this information, perhaps you will decide that the revert is > > > > > > worthwhile. > > > > > > > > > > Damned if I do, damned if I do not. > > > > > Check for usbip and special case it? > > > > > > > > We should be able to do that in the host controller driver for usbip, > > > > right? What is the symptom if you use a UAS device with usbip and this > > > > commit? > > > > > > Yes, that patch should then also be applied. Then it will work. > > > Without it, commands will fail, as transfers will end prematurely. > > > > Ok, I'm confused now. I just checked, and I really have no idea what > > needs to be backported anymore. 3ae62a42090f ("UAS: fix alignment of > > scatter/gather segments") was backported to all of the stable kernels, > > and now we reverted it. > > > > So what else needs to be done here? > > In one sense, nothing needs to be done. 3ae62a42090f was intended to > fix a long-standing problem with USBIP, but people reported a OK, now I am a bit confused. AFAICT 3ae62a42090f actually did fix the issue. So if you simply revert it, the issue will reappear. > regression in performance. (Admittedly, the report was about the > correponding change to usb-storage, not the change to uas, but it's > reasonable to think the effect would be the same.) So in line with the Yes. > no-regressions policy, we only need to revert the commit -- which you > have already done. But that breaks UAS over USBIP, doesn't it? > On the other hand, the long-standing problem in USBIP can be fixed by > back-porting commit ea44d190764b. But since that commit isn't a > bug-fix (and since it's rather large), you may question whether it is > appropriate for the -stable kernel series. It certainly is large. But without it UAS won't work over USBIP, will it? I think that is the central question we need to answer here. Regards Oliver