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=-2.2 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 0C09EC1747C for ; Tue, 5 Nov 2019 14:26:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD942214D8 for ; Tue, 5 Nov 2019 14:26:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730922AbfKEO0H (ORCPT ); Tue, 5 Nov 2019 09:26:07 -0500 Received: from mx2.suse.de ([195.135.220.15]:53818 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727849AbfKEO0H (ORCPT ); Tue, 5 Nov 2019 09:26:07 -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 61FD1AFF3; Tue, 5 Nov 2019 14:26:04 +0000 (UTC) Message-ID: <1572963963.2921.18.camel@suse.com> Subject: Re: [PATCH 4.4 28/46] UAS: Revert commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments") From: Oliver Neukum To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Alan Stern , Christoph Hellwig Date: Tue, 05 Nov 2019 15:26:03 +0100 In-Reply-To: <20191104211901.335806642@linuxfoundation.org> References: <20191104211830.912265604@linuxfoundation.org> <20191104211901.335806642@linuxfoundation.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Am Montag, den 04.11.2019, 22:44 +0100 schrieb Greg Kroah-Hartman: > From: Alan Stern > > commit 1186f86a71130a7635a20843e355bb880c7349b2 upstream. > > Commit 3ae62a42090f ("UAS: fix alignment of scatter/gather segments"), > copying a similar commit for usb-storage, attempted to solve a problem > involving scatter-gather I/O and USB/IP by setting the > virt_boundary_mask for mass-storage devices. We have that in 4.4.x > However, it now turns out that the analogous change in usb-storage > interacted badly with commit 09324d32d2a0 ("block: force an unlimited > segment size on queues with a virt boundary"), which was added later. > A typical error message is: 09324d32d2a0 I cannot find. > ehci-pci 0000:00:13.2: swiotlb buffer is full (sz: 327680 bytes), > total 32768 (slots), used 97 (slots) > > There is no longer any reason to keep the virt_boundary_mask setting > in the uas driver. It was needed in the first place only for > handling devices with a block size smaller than the maxpacket size and > where the host controller was not capable of fully general > scatter-gather operation (that is, able to merge two SG segments into > a single USB packet). But: > > High-speed or slower connections never use a bulk maxpacket > value larger than 512; > > The SCSI layer does not handle block devices with a block size > smaller than 512 bytes; > > All the host controllers capable of SuperSpeed operation can > handle fully general SG; > > Since commit ea44d190764b ("usbip: Implement SG support to > vhci-hcd and stub driver") was merged, the USB/IP driver can > also handle SG. Neither can I find ea44d190764b. It seems to me that, while the patch is necessary in upstream, in 4.4.x it would break usbip. Regards Oliver