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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 55964C10F0E for ; Mon, 8 Apr 2019 01:23:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1A39820879 for ; Mon, 8 Apr 2019 01:23:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=iluvatar.ai header.i=@iluvatar.ai header.b="Zbc+c/tj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726465AbfDHBXf (ORCPT ); Sun, 7 Apr 2019 21:23:35 -0400 Received: from owa.iluvatar.ai ([103.91.158.24]:5252 "EHLO smg.iluvatar.ai" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726349AbfDHBXe (ORCPT ); Sun, 7 Apr 2019 21:23:34 -0400 X-AuditID: 0a650161-78bff700000078a3-78-5caaa28bd427 Received: from owa.iluvatar.ai (s-10-101-1-102.iluvatar.local [10.101.1.102]) by smg.iluvatar.ai (Symantec Messaging Gateway) with SMTP id 22.E3.30883.B82AAAC5; Mon, 8 Apr 2019 09:23:23 +0800 (HKT) Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline DKIM-Signature: v=1; a=rsa-sha256; d=iluvatar.ai; s=key_2018; c=relaxed/relaxed; t=1554686603; h=from:subject:to:date:message-id; bh=Ux048TmV854h+e950bXokICm1VWZROCck0ccAamUXr0=; b=Zbc+c/tjn6VUUGy7gHT+rvKNJnbSpGkvqNlxx5CXMucMs21p//6rIXdkO+/THtZae3SDSXz+hZM AloXWfy1olhnocsuAnEPf1MhRrZfCCkRpesAd+0Fl6WMgQfap04teimdi94j/nLFVieD0OgWKFIqA lCZ/bjkmFE2Rm3TjdhQ= Received: from hsj-Precision-5520 (10.101.199.253) by S-10-101-1-102.iluvatar.local (10.101.1.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1415.2; Mon, 8 Apr 2019 09:23:23 +0800 Date: Mon, 8 Apr 2019 09:23:21 +0800 From: Huang Shijie To: Ira Weiny CC: , , , Subject: Re: [PATCH] mm/gup.c: fix the wrong comments Message-ID: <20190408012320.GA11988@hsj-Precision-5520> References: <20190404072347.3440-1-sjhuang@iluvatar.ai> <20190404165046.GB1857@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 In-Reply-To: <20190404165046.GB1857@iweiny-DESK2.sc.intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Originating-IP: [10.101.199.253] X-ClientProxiedBy: S-10-101-1-105.iluvatar.local (10.101.1.105) To S-10-101-1-102.iluvatar.local (10.101.1.102) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrNLMWRmVeSWpSXmKPExsXClcqYptu9aFWMQesJDYs569ewWex/+pzF 4vKuOWwW99b8Z7XYuvcquwOrR+ONG2wei/e8ZPLY9GkSu8eJGb9ZPD5vkgtgjeKySUnNySxL LdK3S+DK+HaMrWAHR8XO1sUsDYxn2LoYOTgkBEwkjk7i72Lk4hASOMEosX9XP2MXIycHs4CO xILdn8BqmAWkJZb/4wCpYRF4yyTxfPELZoiGb4wSy6Z/ZAdpYBFQkVi29zqYzSagITH3xF1m EFtEQFni9L+rbBBD8yUe3ZvNDDJUWMBU4s/GDBCTV8Bc4uhGf5AKIYFsidWXPoB18goISpyc +YQFxOYUsJN483ED2GmiQBMPbDvOBNIqJKAg8WKlFkhYQkBJYsneWUwQdqHEjIkrGCcwCs9C 8swshGdmIVmwgJF5FSN/cW66XmZOaVliSWKRXmLmJkZIDCTuYLzR+VLvEKMAB6MSD++N7FUx QqyJZcWVuYcYJTiYlUR4d04FCvGmJFZWpRblxxeV5qQWH2KU5mBREuctm2gSIySQnliSmp2a WpBaBJNl4uCUamCaOV3o6p1NBisO9qzcL1O4fstiTe1vL1xUFTd83KEi0b6i7IpZ9pIXjBW+ 5+S/HX1jejbrrpf0bNaLNW9d/tk+vXsnc5XWnQyRLWJFN7deZzsheaS72f60XcXT4g9+9Tvt O6dvc7Bcv2PGrFOfjx2zTp//zdNngYvC0g3ZXlV/24LTBV3VlX6wf7ueeXDBL5t/J/ieyEgf 3cTe4lPQfWZi11nlojVlx+u4P7fvZvDauPHkhnkVT5q/c0pGVAb+XDj/UKld4IfKayc+bpe9 uNGvqUHD+aZ1T8JJCY6pa55N4d22y9+Zg3VWn/15cevgeboMDs/Xnvr06P0TwS3S/DqurWls G086WpiX2RpJyLtOUWIpzkg01GIuKk4EALCAxvD+AgAA Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 04, 2019 at 09:50:47AM -0700, Ira Weiny wrote: > On Thu, Apr 04, 2019 at 03:23:47PM +0800, Huang Shijie wrote: > > When CONFIG_HAVE_GENERIC_GUP is defined, the kernel will use its own > > get_user_pages_fast(). > > > > In the following scenario, we will may meet the bug in the DMA case: > > ..................... > > get_user_pages_fast(start,,, pages); > > ...... > > sg_alloc_table_from_pages(, pages, ...); > > ..................... > > > > The root cause is that sg_alloc_table_from_pages() requires the > > page order to keep the same as it used in the user space, but > > get_user_pages_fast() will mess it up. > > I wonder if there is something we can do to change sg_alloc_table_from_pages() > to work? Reading the comment for it there is no indication of this limitation. The sg_alloc_table_from_pages() cannot work if the page order is wrong... > So should we update that comment as well? Okay. I will create a DMA patch to add more comment for sg_alloc_table_from_pages(). Thanks Huang Shijie